Appearances of colorectal hepatic metastases at diffusion-weighted MRI compared with histopathology: initial observations

Objective

To describe the appearances of colorectal liver metastases on diffusion-weighted MRI (DW-MRI) and to compare these appearances with histopathology.

Methods

43 patients with colorectal liver metastases were evaluated using breath-hold DW-MRI (b-values 0, 150 and 500 s mm^–2). The b=500 s mm^–2 DW-MRI were reviewed consensually for lesion size and appearance by two readers. 18/43 patients underwent surgery allowing radiological–pathological comparison. Tissue sections were reviewed by a pathologist, who classified metastases histologically as cellular, fibrotic, necrotic or mixed. The frequency of DW-MRI findings and histological features were compared using the χ² test.

Results

84 metastases were found in 43 patients. On b=500 s mm^–2 DW-MRI, metastases showed three high signal intensity patterns: rim (55/84), uniform (23/84) and variegate (6/84). Of the 55 metastases showing rim pattern, 54 were >1 cm in diameter (p<0.01, χ² test). 25/84 metastases were surgically resected. Of these, 11/22 metastases >1 cm in diameter showed rim pattern and demonstrated central necrosis at histopathology (p=0.04, χ² test). No definite relationship was found between uniform and variegate patterns with histology.

Conclusion

Rim high signal intensity was the most common appearance of colorectal liver metastases >1 cm diameter on DW-MRI at b-values of 500 s mm^–2, a finding attributable to central necrosis.The appearances of colorectal liver metastases on contrast-enhanced MRI are well described. Following administration of extracellular gadolinium contrast medium, colorectal liver metastases typically show rim enhancement in the arterial phase, but appear hypointense in the portovenous and interstitial phases of enhancement [1,2]. Using small iron oxide particles (SPIO), metastases appear hyperintense on T₂* weighted imaging [3,4]. On mangafodipir trisodium (MnDPDP) [5,6] or gadoxetic acid (Gd-EOB-DTPA) enhanced imaging [7-9], metastases are hypointense on T₁ weighting in the hepatocellular phase of enhancement.Diffusion-weighted MRI (DW-MRI) does not require exogenous contrast administration and derives its image contrast from differences in the mobility of water between tissues [10]. In areas where the extracellular space is reduced or the tortuosity of the extracellular space is increased (e.g. cellular tumour tissues), the signal intensity on diffusion-weighted images is high, which reflects decreased water diffusivity.DW-MRI is increasingly applied in the liver for disease detection and characterisation. It has been shown that DW-MRI is more sensitive than T₂ weighted MRI for lesion detection [11,12]. Furthermore, DW-MRI used on its own or in combination with contrast-enhanced imaging can improve the detection of metastases [13,14]. Clearly, recognising the range of DW-MRI appearances of colorectal liver metastases would increase the confidence of their diagnosis. DW-MRI may be particularly valuable in patients with renal impairment, in whom there may be reluctance or contraindication to the administration of extracellular gadolinium contrast media.In our clinical practice, we have observed a range of DW-MRI appearances of colorectal liver metastases, and, although metastases can be detected at b-values of 150 s mm^–2, these demonstrate more characteristic appearances at a higher b value of 500 s mm^–2. As far as we are aware, the DW-MRI appearances of colorectal liver metastases have not been previously reported in the published literature. Furthermore, the pathological basis for the DW-MRI appearances of colorectal liver metastases has not been clearly established. Radiological–pathological comparisons of colorectal liver metastases can inform our understanding of the histological changes that result in their DW-MRI appearance, and may in future help to identify biologically relevant subgroups for selective treatment. Hence, the aim of this study was to describe the appearances of colorectal liver metastases on DW-MRI and to compare these appearances with histopathology.     

Gd-EOB-DTPA-enhanced MRI for the assessment of liver function and volume in liver cirrhosis

Objective:

The aims of this study were to use dynamic hepatocyte-specific contrast-enhanced MRI to evaluate liver volume and function in liver cirrhosis, correlate the results with standard scoring models and explore the inhomogeneous distribution of liver function in cirrhotic livers.

Methods:

10 patients with liver cirrhosis and 20 healthy volunteers, serving as controls, were included. Hepatic extraction fraction (HEF), input relative blood flow and mean transit time were calculated on a voxel-by-voxel basis using deconvolutional analysis. Segmental and total liver volumes as well as segmental and total hepatic extraction capacity, expressed in HEFml, were calculated. An incongruence score (IS) was constructed to reflect the uneven distribution of liver function. The Mann–Whitney U-test was used for group comparison of the quantitative liver function parameters, liver volumes and ISs. Correlations between liver function parameters and clinical scores were assessed using Spearman rank correlation.

Results:

Patients had larger parenchymal liver volume, lower hepatocyte function and more inhomogeneous distribution of function compared with healthy controls.

Conclusion:

The study demonstrates the non-homogeneous nature of liver cirrhosis and underlines the necessity of a liver function test able to compensate for the heterogeneous distribution of liver function in patients with diseased liver parenchyma.

Advances in knowledge:

The study describes a new way to quantitatively assess the hepatic uptake of gadoxetate or gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid in the liver as a whole as well as on a segmental level.In patients undergoing liver resection, post-operative liver failure is a major concern and has in current practice become the biggest cause for mortality after liver resection [1–3]. Residual liver should be of adequate volume and quality to sustain immediate post-operative function and to allow regeneration for complete restoration of hepatic function. Currently, surgical decision-making is predominantly based on volume calculation from cross-sectional imaging, sometimes in combination with liver function evaluation [4,5]. A variety of different methods for quantitative assessment of global liver function are available, including clearance–retention tests, redox chemistry and scintigraphy [6,7]. All currently available metabolic tests give a global assessment of liver function and do not account or correct for the possible heterogeneous distribution of function within the liver parenchyma. Scoring models, of which the Child–Pugh score (CPS) [8,9] and the model for end-stage liver disease (MELD) [10] are the most frequently used, are hampered by the same limitations.A number of published studies, using different scintigraphic methods, have verified the presence of heterogeneous distribution of function in the liver parenchyma. In a group of patients with diverse underlying liver pathologies investigated with ^99mTc-mebrofenin, it was found that liver function was unevenly distributed within the liver [11]. Regional variations in uptake were also demonstrated using ^99mTc-labelled galactosyl human serum albumin [12,13]. This phenomenon was also observed in patients with primary sclerosing cholangitis using ^99mTc-HIDA [14].Gadoxetate or gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA; Primovist®, Bayer Healthcare, Berlin) is a contrast agent developed for MRI. It is a gadolinium chelate that is actively taken up into the hepatocytes through the organic anion-transporting polypeptides [15]. This is a property Gd-EOB-DTPA shares with the iminodiacetic acid compounds used in hepatobiliary scintigraphy (HBS) and with indocyanine green (ICG) [16–20]. Pharmacokinetic studies show that about 50% of the administered dose of Gd-EOB-DTPA is extracted by the liver and eliminated through the hepatobiliary pathway. The remaining 50% is eliminated by renal excretion [21]. As the hepatic elimination of Gd-EOB-DTPA is dependent on the integrity of the hepatocyte mass, quantification of the uptake should represent the same aspects of liver function as assessed by ICG clearance or HBS.Dynamic hepatocyte-specific contrast-enhanced MRI (DHCE-MRI) has previously been used in animal models for the evaluation of hepatic function in various experimental settings, either using semi-quantitative parameters or using deconvolutional analysis (DA) [22–25]. In human studies, liver parenchymal enhancement after administration of Gd-EOB-DTPA has been shown to correlate with ICG clearance and with liver cirrhosis as assessed by the CPS [26,27], and subsequent biliary excretion has been shown to be delayed in patients with impaired liver function [28]. In a study of patients with primary biliary cirrhosis, quantitative parameters indicative of liver function derived from DA were shown to correlate with disease severity [29]. Also, compartmental modelling has been used to assess the hepatic uptake of Gd-EOB-DTPA, and the parameters derived were shown to be dependent on the CPS [30]. These findings support the hypothesis that results from DHCE-MRI have the potential to assess liver function.The present study should be regarded as a feasibility study aiming to investigate DHCE-MRI as a method to explore the inhomogeneous distribution of liver function in patients with liver cirrhosis compared with a control group and to explore the correlation between DHCE-MRI-derived liver function parameters with commonly used clinical scoring models. The primary outcome was the overall hepatic extraction capacity of Gd-EOB-DTPA, and secondary outcomes were measures of liver function heterogeneity, liver function indices and correlation analysis.     

The intravertebral cleft in benign vertebral compression fracture: the diagnostic performance of non-enhanced MRI and fat-suppressed contrast-enhanced MRI

We compared the diagnostic performance of non-enhanced MRI and fat-suppressed contrast-enhanced MRI (CEMRI) in diagnosing intravertebral clefts in benign vertebral compression fractures (VCFs). We retrospectively reviewed 99 consecutive patients who had undergone percutaneous vertebroplasty for VCFs. A cleft was defined as a signal void or hyperintense area on non-enhanced MRI (T₁ and T₂ weighted imaging) or as a hypointense area within a diffusely enhanced vertebra on CEMRI. A cleft was confirmed as a solid opacification on post-procedural radiographs. The interobserver reliability and MRI diagnostic performance were evaluated. The interobserver reliability of non-enhanced MRI was substantial (k _ 0.698) and the interobserver reliability of CEMRI was almost perfect (k _ 0.836). Post-procedural radiographs showed solid cleft opacification in 32 out of the 99 cases. The sensitivity and specificity of non-enhanced MRI were 0.72 and 0.82 (observer 1) and 0.63 and 0.87 (observer 2), respectively. The sensitivity and specificity of CEMRI were 0.94 and 0.63 (observer 1) and 0.85 and 0.60 (observer 2), respectively. The sensitivity of CEMRI was significantly higher than that of non-enhanced MRI, and the specificity of non-enhanced MRI was higher than that of CEMRI. CEMRI was highly reliable and sensitive, and non-enhanced MRI was specific for intravertebral clefts. Therefore, spine MRIs, including CEMRI, could provide useful information about intravertebral clefts before percutaneous vertebroplasty.Intravertebral clefts associated with vertebral compression fractures (VCFs) are radiographic signs representing cavities within fractured vertebrae and have long been considered pathognomonic for avascular necrosis of the spine (Kümmell’s sign) [1–3]. However, several investigators have observed that intravertebral clefts are common in patients with osteoporotic compression fractures [4–6]. Currently, clefts are thought to represent corticocancellous disruption in mobile osteoporotic fractures, rather than avascular necrotic disease [4, 6].Percutaneous vertebroplasty (PV) is an effective and minimally invasive procedure for the treatment of osteoporotic compression fractures [7, 8]. The advent of PV as the major treatment option for VCFs has prompted interest in intravertebral clefts occurring in benign VCFs. Recent studies have suggested that the clinical outcomes and complications associated with PV are influenced by the presence of clefts [4, 9–13]. Thus, radiological detection of clefts is indispensable for managing patients with VCFs.Spine MRI is commonly used for the evaluation of acute VCFs. MRI is useful in distinguishing malignancy from acute osteoporotic VCFs [14, 15] and is effective in demonstrating bone marrow oedema associated with acute compression fractures, which is one of the indications for performing PV [14, 16]. The MRI findings associated with intravertebral clefts have been well described [3–5]. However, there is controversy concerning the efficacy of MRI in diagnosing clefts. Specifically, the reliability and effectiveness of contrast-enhanced MRI (CEMRI), first assessed by Oka et al in 2005 [11], has not been properly evaluated. Such evaluation is important, given that CEMRI entails additional expense.To evaluate the efficacy of the CEMRI for the prediction of intravertebral clefts, we assessed the interobserver reliability and diagnostic performance of non-enhanced T₁ weighted and T₂ weighted MRI (T1WI and T2WI) and CEMRI in the identification of intravertebral clefts in VCFs. We then compared the diagnostic performance of CEMRI with that of non-enhanced MRI.     

Towards clinical assessment of velopharyngeal closure using MRI: evaluation of real-time MRI sequences at 1.5 and 3 T

Objective

The objective of this study was to demonstrate soft palate MRI at 1.5 and 3 T with high temporal resolution on clinical scanners.

Methods

Six volunteers were imaged while speaking, using both four real-time steady-state free-precession (SSFP) sequences at 3 T and four balanced SSFP (bSSFP) at 1.5 T. Temporal resolution was 9–20 frames s⁻¹ (fps), spatial resolution 1.6×1.6×10.0–2.7×2.7×10.0 mm³. Simultaneous audio was recorded. Signal-to-noise ratio (SNR), palate thickness and image quality score (1–4, non-diagnostic–excellent) were evaluated.

Results

SNR was higher at 3 T than 1.5 T in the relaxed palate (nasal breathing position) and reduced in the elevated palate at 3 T, but not 1.5 T. Image quality was not significantly different between field strengths or sequences (p=NS). At 3 T, 40% acquisitions scored 2 and 56% scored 3. Most 1.5 T acquisitions scored 1 (19%) or 4 (46%). Image quality was more dependent on subject or field than sequence. SNR in static images was highest with 1.9×1.9×10.0 mm³ resolution (10 fps) and measured palate thickness was similar (p=NS) to that at the highest resolution (1.6×1.6×10.0 mm³). SNR in intensity–time plots through the soft palate was highest with 2.7×2.7×10.0 mm³ resolution (20 fps).

Conclusions

At 3 T, SSFP images are of a reliable quality, but 1.5 T bSSFP images are often better. For geometric measurements, temporal should be traded for spatial resolution (1.9×1.9×10.0 mm³, 10 fps). For assessment of motion, temporal should be prioritised over spatial resolution (2.7×2.7×10.0 mm³, 20 fps).

Advances in knowledge

Diagnostic quality real-time soft palate MRI is possible using clinical scanners and optimised protocols have been developed. 3 T SSFP imaging is reliable, but 1.5 T bSSFP often produces better images.Approximately 450 babies born in the UK every year have an orofacial cleft [1], the majority of which include the palate [2]. While a cleft palate is commonly repaired surgically at around 6 months [3], residual velopharyngeal insufficiencies require follow-up surgery in 15–50% of cases [4]. This residual defect results in an incomplete closure of the velopharyngeal port, which in turns leads to hypernasal speech. Assessment of velopharyngeal closure in speech therapy is commonly performed using X-ray videofluoroscopy or nasendoscopy [5,6]. While nasendoscopy is only minimally invasive, it may be uncomfortable and provides only an en face view of the velopharyngeal port. In contrast, X-ray videofluoroscopy is non-invasive and produces an image which is a projection of the target anatomy. Additional information may be obtained from projections at multiple angles [5,7], but anatomical structures may overlie each other. Furthermore, soft tissue contrast, such as that from the soft palate, is poor, although it may be improved using a barium contrast agent coating [8] at the expense of making the procedure more invasive and unpleasant. Arguably the greatest drawback of X-ray videofluoroscopy is the associated ionising radiation dose, which carries increased risk in paediatric patients [9].An increasing number of research studies have used MRI to image the soft palate [10-13] and upper vocal tract [14-17]. In contrast to X-ray videofluoroscopy and nasendoscopy, MRI provides tomographic images in any plane with flexible tissue contrast. As a result, MRI has been used to obtain images of the musculature of the palate at rest and during sustained phonation [10,18,19]. It has also been used to image the whole vocal tract at rest or during sustained phonation [20-27] and with a single mid-sagittal image dynamically during speech [13,15-17,28-35].For assessment of velopharyngeal closure, dynamic imaging with sufficient temporal resolution and simultaneous audio recording is required. Audio recording during imaging is complicated by the loud noise of the MRI scanner, and both the safety risk and image degradation caused by using an electronic microphone within the magnet. As a result, optical fibre-based equipment with noise cancellation algorithms must be used [36].In order to fully resolve soft palate motion, Narayanan et al [30] suggested that a minimum temporal resolution of 20 frames s⁻¹ (fps) is required. A similar conclusion was reached by Bae et al [13], based on measurements of soft palate motion extracted from X-ray videofluoroscopy. Using segmented MRI, Inoue et al [35] demonstrated that changes in the velar position that were evident at acquired frame rates of 33 fps were not observed at 8 fps. However, MRI is traditionally seen as a slow imaging modality and achieving sufficient temporal resolution at an acceptable spatial resolution is challenging. Furthermore, as the soft palate is bordered on both sides by air, the associated changes in magnetic susceptibility at the interfaces make images prone to related artefacts.Dynamic MRI of the vocal tract has been performed using both segmented [17,33,37] and real-time acquisitions [13,15,16,28,31,38]. Segmented acquisitions [39] acquire only a fraction of the k-space data required for each image during one repetition of the test phrase and, hence, require multiple identical repetitions. While these segmented techniques permit high temporal and spatial resolutions [35], they require reproducible production of the same phrase up to 256 times [34], leading to subject fatigue. Differences between repeats of up to 95 ms in the onset of speech following a trigger have also been demonstrated [36].In contrast to segmented techniques, real-time dynamic methods permit imaging of natural speech, but require extremely rapid acquisition and often advanced reconstruction methods. The turbo spin echo (TSE) zoom technique [40] has been used to perform real-time MRI of the vocal tract [29,31] and is available as a clinical tool. The zoom technique excites a reduced field of view in the phase encode direction, hence allowing a smaller acquisition matrix and shorter scan for a constant spatial resolution. While such spin echo-based techniques are less susceptible to magnetic field inhomogeneity related signal dropout artefacts than other sequences, the frame rates achieved with these sequences are limited to 6 fps [31]. Gradient echo-based techniques have also been used to achieve similar temporal resolution [12,41,42] in the upper vocal tract, but are often used at much higher frame rates in other MRI applications such as cardiac imaging [43,44]. A number of gradient echo sequence variants exist. Fast low-angle shot (FLASH) type sequences [45] spoil any remaining transverse magnetisation at the end of every sequence repetition (TR). In contrast, steady-state free-precession (SSFP) sequences are not spoiled [46] and the remaining transverse magnetisation is used in the next TR to improve the signal-to-noise ratio (SNR), but renders the images sensitive to signal loss in the presence of motion. Balanced SSFP (bSSFP) sequences include additional gradients to bring the transverse magnetisation completely back into phase at the end of every TR [47,48]. The result is that bSSFP sequences have high SNR and are less sensitive to motion than SSFP sequences, but are more sensitive to field inhomogeneities, which cause bands of signal dropout.Both TSE and the gradient echo techniques discussed here sample in a rectilinear or Cartesian fashion, where one line of k-space is sampled in each echo. However, for real-time speech imaging, the highest acquired frame rates have been achieved by sampling k-space along a spiral trajectory [15,16,30,49]. While spiral imaging is an efficient way to sample k-space and is motion-resilient, it is prone to artefacts, particularly blurring caused by magnetic field inhomogeneities and off-resonance protons (i.e. fat) [50]. Recently, one group successfully used spiral imaging with multiple saturation bands and an alternating echo time (TE) to achieve an acquired real-time frame rate of 22 fps [13,16]. The saturation bands were used to allow a small field of view to be imaged without aliasing artefacts. The alternating TE was used to generate dynamic field maps which were incorporated into the reconstruction to compensate for magnetic field inhomogeneities. However, such advanced acquisition and reconstruction techniques are only available in a small number of research centres.The aim of this work is to optimise and demonstrate high-temporal-resolution real-time sequences available on routine clinical MRI scanners for assessment of soft palate motion and velopharyngeal closure. Consequently, radial and spiral acquisitions were excluded and the work focuses on Cartesian gradient echo sequences with parallel imaging techniques. As more clinical MRI departments now have 3 T scanners, imaging was performed at both 1.5 and 3 T to enable comparisons. At each field strength, we optimised sequences and implemented four combinations of spatial and temporal resolution in six subjects with simultaneous audio recordings.     

Iron overload: accuracy of in-phase and out-of-phase MRI as a quick method to evaluate liver iron load in haematological malignancies and chronic liver disease

Objectives

The purpose of this prospective study was to evaluate the accuracy of in-phase and out-of-phase imaging to assess hepatic iron concentration in patients with haematological malignancies and chronic liver disease.

Methods

MRI-based hepatic iron concentration (M-HIC, μmol g^–1) was used as a reference standard. 42 patients suspected of having iron overload and 12 control subjects underwent 1.5 T in- and out-of-phase and M-HIC liver imaging. Two methods, semi-quantitative visual grading made by two independent readers and quantitative relative signal intensity (rSI) grading from the signal intensity differences of in-phase and out-of-phase images, were used. Statistical analyses were performed using the Spearman and Kruskal–Wallis tests, receiver operator curves and κ coefficients.

Results

The correlations between M-HIC and visual gradings of Reader 1 (r=0.9534, p<0.0001) and Reader 2 (r=0.9456, p<0.0001) were higher than the correlations of the rSI method (r=0.7719, p<0.0001). There was excellent agreement between the readers (weighted κ=0.9619). Both visual grading and rSI were similar in detecting liver iron overload: rSI had 84.85% sensitivity and 100% specificity; visual grading had 85% sensitivity and 100% specificity. The differences between the grades of visual grading were significant (p<0.0001) and the method was able to distinguish different degrees of iron overload at the threshold of 151 μmol g^–1 with 100% positive predictive value and negative predictive value.

Conclusion

Detection and grading of liver iron can be performed reliably with in-phase and out-of-phase imaging. Liver fat is a potential pitfall, which limits the use of rSI.Iron overload is a clinically recognised condition with variety of aetiologies and clinical manifestations [1-4]. Liver iron concentration correlates closely with the total body iron stores [5]. The excess iron accumulates mainly in the liver and the progressive accumulation of toxic iron can lead to organ failure if untreated [2,4]. Several diseases causing iron overload, such as transfusion-dependent anaemia, haematological malignancies, thalassaemia, haemochromatosis and chronic liver disease, result in a large number of patients with a potentially treatable iron overload [1,2,4].Several quantitative MRI methods for iron overload measurement by multiple sequences have been established, such as proportional signal intensity (SI) methods and proton transverse relaxation rates (R₂, R₂*) [4,6,7]. A gradient echo liver-to-muscle SI-based algorithm [8] has been widely validated and used for quantitative liver iron measurement [8-11]. MRI-based hepatic iron concentration (M-HIC, μmol g^–1 liver dry weight) with corresponding R₂* [9] can be calculated with this method which is a directly proportional linear iron indicator, virtually independent of the fat fraction, as the echo times are taken in-phase [8,9]. This method showed a high accuracy in calibrations with the biochemical analysis of liver biopsies (3–375 μmol g^–1) of 174 patients. The mean difference of 0.8 μmol g^–1 (95% confidence interval of –6.3 to 7.9) between this method and the biochemical analysis is quite similar [8] to the intra-individual variability found in histological samples [12].The quantitative MRI methods are based on progressive SI decay, with the longer echo times due to relaxing properties of iron. Interestingly, this iron-induced effect is seen in MR images with multiple echoes [4,6-11], but also in dual-echo images, namely in-phase and out-of-phase imaging [13,14]. In-phase and out-of-phase imaging has become a routine part of liver MRI, performed initially for liver fat detection [6,13,15]. Quite recently some investigators have noticed an alternative approach of the sequence to detect liver iron overload due to the more pronounced SI decrease on in-phase images with the longer echo time [13,14]. Yet, to our knowledge, this is the first prospective study evaluating the accuracy of in-phase and out-of-phase imaging to assess hepatic iron concentration.The purpose of the study was to evaluate the capability and accuracy of dual-echo in-phase and out-of-phase imaging to assess hepatic iron concentration at 1.5 T in patients with haematological malignancies and chronic liver disease. MRI-based hepatic iron concentration (M-HIC, μmol g^–1) was used as a reference standard [8,9].     

Focal nodular hyperplasia: characterisation at gadoxetic acid-enhanced MRI and diffusion-weighted MRI

Purpose:

The aim of this study was to assess the enhancement patterns of hepatic focal nodular hyperplasia (FNH) on gadoxetic acid-enhanced MRI and diffusion-weighted (DW) MRI.

Methods:

This retrospective study had institutional review board approval. Gadoxetic acid-enhanced and DW MR images were evaluated in 23 patients with 30 FNHs (26 histologically proven and 4 radiologically diagnosed). The lesion enhancement patterns of the hepatobiliary phase images were classified as heterogeneous or homogeneous signal intensity (SI), and as dominantly high/iso or low SI compared with those of adjacent liver parenchyma. Heterogeneous (any) SI lesions and homogeneous low SI lesions were categorised into the fibrosis group, whereas homogeneous high/iso SI lesions were categorised into the non-fibrosis group. Additionally, lesion SI on T₂ weighted images, DW images and apparent diffusion coefficient (ADC) values were compared between the two groups.

Results:

The lesions showed heterogeneous high/iso SI (n=16), heterogeneous low SI (n=5), homogeneous high/iso SI (n=7) or homogeneous low SI (n=2) at the hepatobiliary phase MR images. The fibrosis group lesions were more likely to show high SI on DW images and T₂ weighted images compared with those in the non-fibrosis group (p<0.05). ADC values tended to be lower in the fibrosis group than those in the non-fibrosis group without significance.

Conclusion:

FNH showed variable enhancement patterns on hepatobiliary phase images during gadoxetic acid-enhanced MRI. SI on DW and T₂ weighted images differed according to the fibrosis component contained in the lesion.

Advances in knowledge:

FNH shows a wide spectrum of imaging findings on gadoxetic acid-enhanced MRI and DW MRI.Focal nodular hyperplasia (FNH) is the second most common benign hepatic tumour after haemangioma, and most frequently occurs in females of childbearing and middle age [1]. It is considered to result from a congenital vascular disorder leading to a hyperplastic response of the surrounding liver parenchyma and is histologically characterised by normal hepatocytes with malformed bile ducts [2,3]. It is generally accepted that FNH can be managed conservatively and most cases do not require surgery because of the lack of malignancy potential and low risk of complications such as rupture or haemorrhage [4,5]. Therefore, the goal of imaging is to make a confident diagnosis and to avoid a biopsy or even surgical resection.MRI is a well-established and widely used diagnostic modality for detecting and characterising focal hepatic lesions and generally allows a confident diagnosis of typical FNH [6–8]. Findings of typical FNH on conventional gadolinium-enhanced MRI are brisk arterial enhancement, iso or slightly low signal intensity (SI) on the portal and equilibrium phase, iso or slightly low SI on T₁ weighted images, iso or slightly high SI on T₂ weighted images, a central scar showing high SI on T₂ weighted images and delayed dynamic enhancement [6–9]. However, when atypical imaging features are present, such as atypical findings of a central scar, high SI on T₁ weighted images or washout during the portal or equilibrium phase, it is not easy to distinguish FNH from other hypervascular tumours, such as hepatocellular adenomas, hypervascular metastasis or fibrolamellar hepatocellular carcinomas [6,9]. Indeed, according to a study by Bieze et al [6], characterisation of FNH and hepatocellular adenoma on standard MRI is inconclusive in 40% of lesions.Gadoxetic acid (Primovist®; Bayer-Schering Pharma, Berlin, Germany) is a new recently approved hepatobiliary gadolinium-based contrast agent. It has dual pharmacokinetic actions that combine extracellular properties for dynamic phase imaging with high hepatocyte-specific uptake and biliary excretion for delayed hepatobiliary phase imaging [10,11]. Many reports have concluded that FNHs show liver-specific enhancement and appear as iso or high SI on hepatobiliary phase imaging, and this enhancement pattern is a new additional criterion for diagnosing FNH, particularly in comparison with hepatocellular adenoma [6,10–15]. However, even though the major enhancement features of FNH are iso or high SI on hepatobiliary phase imaging, the portion of the central stellate scar or radiating fibrous septa of FNH demonstrates low SI owing to a lack of functioning hepatocytes. We postulate that the overall SI of FNH lesions during hepatobiliary phase imaging is dependent on their proportions of cellular and fibrous components.Diffusion-weighted (DW) imaging is useful for the detection and characterisation of hepatic focal lesions [16–18]. In theory, DW imaging measures the random motion of water molecules in biological tissues and reflects tissue properties, such as the size of the extracellular space, viscosity and cellularity [18–20]. According to prior hepatic fibrosis evaluations using DW imaging, lower apparent diffusion coefficient (ADC) values are observed in cirrhotic liver compared with normal liver tissue, which may be owing to restricted diffusion from extracellular fibrosis [21–25]. Despite the fact that FNH is benign, some lesions show diffusion restrictions, probably owing to their high cellularity [26–28], and fibrosis components contained in FNH lesions should influence the degree of diffusion restriction.The purpose of this study was to classify FNH lesions according to their enhancement pattern on hepatobiliary phase imaging and to assess the findings on DW and T₂ weighted imaging of the lesions with regard to those on hepatobiliary phase imaging.     

MRI features of serous oligocystic adenoma of the pancreas: differentiation from mucinous cystic neoplasm of the pancreas

Objectives

The purpose of this study was to describe the MRI features of the benign pancreatic neoplasm serous oligocystic adenoma (SOA) that differ from those of mucinous cystic neoplasm (MCN), a neoplasm with the potential for malignant degeneration.

Methods

Seven patients with SOA (seven women; mean age 36.6 years) and eight patients with MCN (eight women: mean age 39.9 years) were included. Several imaging features were reviewed: mass size, location, shape, wall thickness, cyst configuration (Type I, unilocular; Type II, multiple clustered cyst; Type III, cyst with internal septation) and signal intensity of the lesion with heterogeneity.

Results

SOA lesions were smaller (3.4 cm) than those of MCN (9.3 cm) (p=0.023). The commonest lesion shape was lobulated (85.7%) for SOA, but oval (50.0%) or lobulated (37.5%) for MCN (p=0.015). The most common cyst configuration was Type II (85.7%) for SOA and Type III (75.0%) for MCN (p=0.008). Heterogeneity of each locule in T₁ weighted images was visible in all cases of MCN, but in no case for SOA (p=0.004).

Conclusion

SOA could be differentiated from MCN by identifying the imaging features of lobulated contour with multiple clustered cyst configurations and homogeneity of each locule in T₁ weighted MR images.Serous oligocystic adenoma (SOA) is a recently described rare, benign pancreatic neoplasm and a morphological variant of serous microcystic adenoma, because it contains six or fewer cysts and the cysts are large (>2 cm) [1,2]. Pathologically, SOA is a benign pancreatic neoplasm composed of a few relatively large cysts uniformly lined with glycogen-rich cuboidal epithelial cells [3]. According to the World Health Organization classification, SOA is a subgroup of pancreatic serous cystic tumours and the term SOA is a synonym for macrocystic serous cystadenoma [3,4].The CT and MRI features of SOA of the pancreas are documented [2]. On CT and MRI, SOA typically appears as a small unilocular or bilocular cyst (<5 cm) with a thin wall (<2 mm) that lacks mural nodules or calcifications [2]. Because the cystic spaces are >2 cm, SOA images can be mistaken for mucinous cystic neoplasm (MCN), pseudocyst or intraductal papillary mucinous tumour [2,5-7]. It is very difficult to differentiate SOA from MCN by clinical and radiological features [2,6,8,9]. SOA does not require resection unless it causes symptoms, but MCN should be resected because of a potential for malignant degeneration [5,7,8]. Endoscopic ultrasound and cyst fluid aspiration have a role in distinguishing mucinous and serous lesions, but it is an invasive procedure with a risk of complications such as pancreatitis [10]. Therefore, it is clinically valuable to determine characteristic imaging findings that can distinguish SOA from MCN.Recently, Kim et al [6] and Cohen-Scali et al [5] described characteristic CT findings that can be used to differentiate SOA from MCN. MRI can demonstrate septa within a lesion with greater sensitivity than CT; therefore, MRI provides a better evaluation of tissue characteristics than CT [1,11]. However, few studies have described the MRI features of SOA [1,2]. The purpose of this study was to describe the differences in the MRI features of SOA and MCN in the pancreas.     

Segmental liver hyperintensity in malignant biliary obstruction on diffusion weighted MRI: associated MRI findings and relationship with serum alanine aminotransferase levels

Objectives

Segmental liver hyperintensity can be observed in malignant biliary obstruction on diffusion weighted MRI (DW-MRI). We describe MRI findings associated with this sign and evaluate whether DW-MRI segmental hyperintensity has any relationship with serum alanine aminotransferase (ALT) levels.

Methods

The DW-MRI T₁ weighted, T₂ weighted and gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced T₁ weighted images obtained in 21 patients with hepatic malignancy, who demonstrated biliary obstruction and segmental hyperintensity on DW-MRI (b=0–750 s mm^–2), were retrospectively reviewed by 2 readers blinded to clinical results. DW-MRI hyperintense liver segments were recorded as hypointense, isointense or hyperintense relative to normal liver on T₁/T₂ weighted imaging. It was also noted whether contrast enhancement was similar to that observed in normal liver or diminished in the hepatocellular phase. The mean apparent diffusion coefficient (ADC) value (×10⁻³ s mm^–2) of DW-MRI hyperintense segments, normal liver and tumour were compared using Student’s t-test. The frequency of MRI findings was corroborated with serum ALT levels, which reflect hepatocyte injury.

Results

DW-MRI hyperintense segments frequently showed T₁ hyperintensity (10/21), T₂ hyperintensity (19/21) and/or diminished contrast enhancement (15/21). Tumours showed significantly lower mean ADC values than liver (1.23±0.08 vs 1.43±0.05; p=0.013). Segments showing concomitant T₁ hyperintensity had lower mean ADC values than liver (1.30±0.05 vs 1.43±0.05; p=0.023). The patients (8/10) with concomitant T₁ and DW-MRI segmental hyperintensity showed elevated ALT levels (p=0.030, Fisher’s exact test).

Conclusion

Concomitantly high T₁ weighted and DW-MRI signal in liver segments was associated with lower ADC values and abnormal liver function tests, which could reflect underlying cellular swelling and damage.Hepatic malignancies, both primary tumours and metastases, are known to cause biliary obstruction. Although a tumour at the porta hepatis might obstruct bile ducts to both hepatic lobes, smaller tumours arising in the periphery of the liver can also cause localised segmental or subsegmental biliary obstruction. Such obstruction can lead to intrahepatic biliary dilatation demonstrable by ultrasound [1] or CT [2]. Significant biliary obstruction can result in hepatocellular injury, which can be reflected by an increase in serum alanine aminotransferse (ALT) [3]. ALT is a cytosolic enzyme highly specific for hepatocytes that is released when cell membrane integrity is compromised during cell injury or cell death [4,5].MRI has been used to evaluate the effects of biliary obstruction on the liver parenchyma. The liver segment associated with intrahepatic biliary obstruction has been reported to show high T₂ signal intensity but more variable hypointense to hyperintense signal intensity on T₁ weighted imaging [6,7], reflecting a probable change in tissue composition. However, morphological imaging does not necessarily reflect biochemical or histological changes that occur as a consequence of obstruction. Diffusion weighted MRI (DW-MRI) informs us of the mobility of water molecules in the microenvironment [8], which can be inferred from the higher b-value images (b>500 s mm^–2) and quantified by the apparent diffusion coefficient (ADC). In areas of impeded water diffusion (e.g. owing to increased cellularity and/or cellular swelling) b-value images (b>500 s mm^–2) return high signal intensity and low ADC values. This technique has been used in the liver for the characterisation of tumours, cancer treatment response assessment and for the evaluation of liver fibrosis [9,10].At our institution it has been observed that some patients with intrahepatic duct dilatation secondary to a hepatic tumour show hyperintensity of involved liver segments on DW-MRI (Figure 1). Given that biliary obstruction causes increased hepatocyte volume [11] and ALT derangement [3], we hypothesise that segmental hyperintensity in the liver parenchyma associated with biliary obstruction on DW-MRI might indicate underlying hepatocellular swelling and damage that could be related to serum ALT levels. Thus, DW-MRI could enable the identification of obstructed liver segments with functional damage for which urgent intervention is needed (e.g. by selective biliary drainage/stenting) to prevent further deterioration [12]; DW-MRI might also provide a means to assess the effectiveness of stenting or treatment by resolution of this appearance.Open in a separate windowFigure 1A 79-year-old male with metastatic colorectal cancer to liver. Diffusion weighted images acquired at (a) a b-value of 0 s mm^–2 and (b) a b-value of 750 s mm^–2 show segmental hyperintensity (arrows) of the obstructed liver segment resulting from a metastasis (arrowheads) located at the apex of the segment. Note small dilated biliary ducts within the segment are signal-suppressed on the high b-value image (b).As far as we are aware, the application of DW-MRI for the assessment of biliary obstruction has not been previously described. The association of DW-MRI findings to other conventional MRI findings has not been established. Furthermore, the relationship between DW-MRI findings and serum ALT derangement is also unknown. Hence, the aim of this study was to explore the conventional MRI findings associated with DW-MRI hyperintensity in patients with malignant biliary tree obstruction and to evaluate whether DW-MRI segmental hyperintensity has any relationship with serum ALT levels.     

Diagnostic efficacy of gadoxetic acid-enhanced MRI for the detection and characterisation of liver metastases: comparison with multidetector-row CT

Objectives

We compared the diagnostic performance of gadoxetic acid-enhanced MRI and 16-slice multidetector CT (MDCT) with respect to their abilities to detect hepatic metastases and differentiate hepatic metastases from hepatic cysts and haemangiomas.

Methods

67 patients with 110 liver metastases (size 0.3–2.5 cm), 33 haemangiomas (size 0.5–1.5 cm) and 17 cysts (size 0.3–1.0 cm) underwent 4-phase MDCT and gadoxetic acid-enhanced MRI, including early dynamic phases, post-contrast T₂ weighted turbo spin echo sequences and 20 min hepatocyte-selective phases. Two observers independently analysed each image in random order. Sensitivity and diagnostic accuracy for lesion detection and differentiation for MDCT and gadoxetic acid-enhanced MRI were calculated using receiver operating characteristic analysis.

Results

For both observers, the Az values of gadoxetic acid-enhanced MRI (mean, 0.982 and 0.981) were significantly higher than the Az values of MDCT (mean, 0.839 and 0.892) (p<0.05) for the detection of metastases and for the differentiation of metastases from haemangiomas and cysts. Sensitivities of gadoxetic acid-enhanced MRI with regard to the detection and characterisation of liver metastases (mean, 96.9% and 96.0%) were significantly higher than those of MDCT (mean, 78.7% and 75.0%) (p<0.05).

Conclusion

Gadoxetic acid-enhanced MRI showed higher diagnostic accuracy and sensitivity than did MDCT for the detection of hepatic metastases and for the differentiation between hepatic metastases and hepatic haemangiomas or cysts.The early detection and precise characterisation of liver metastases are crucial factors in liver imaging because the success of surgery and ablation therapy depends on the knowledge of the precise number and locations of metastatic lesions [144]. Multidetector-row CT (MDCT) has been widely used as a primary imaging modality for evaluating liver metastases because of its wide availability. However, there has been some concern that MDCT images may not accurately characterise small hepatic nodules that are “too small to characterise”, and may not sufficiently differentiate small hepatic metastases from small hepatic cysts or haemangiomas, which are the most frequently encountered causes of focal liver lesions on CT [5-7]. Furthermore, MDCT is less able to detect liver metastases than MRI using liver-targeted agents, such as superparamagnetic iron oxide [8-13]. Thus, with the advent of new MR contrast agents for liver imaging, considerable attention has been focused on the ability of MR contrast agents to detect and characterise small focal liver lesions relative to the conventional imaging modality or previously existing MR contrast agents.Gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA, gadoxetic acid disodium, Primovist®; Bayer HealthCare, Berlin, Germany) is a recently introduced dual-acting MR contrast agent that combines the properties of an extracellular space contrast (ECS) agent and a liver-specific agent [14-19]. The combination of these properties enables the acquisition of the early vascular-interstitial phase, which provides haemodynamic information, and the hepatocyte phase, which detects liver malignancies. Thus, gadoxetic acid has a potency to fulfil the dual requirements for early detection and accurate characterisation of focal liver lesions. To the best our knowledge, no previous study has evaluated the diagnostic capability of gadoxetic acid-enhanced MRI to detect and characterise liver metastases compared with MDCT. In this study, we retrospectively compared the diagnostic performance of gadoxetic acid-enhanced MRI and 16-slice MDCT in detecting small hepatic metastases and in differentiating hepatic metastases from hepatic haemangiomas and cysts, using alternative free-response receiver operating characteristic (ROC) analysis.     

Diffusion-weighted MRI as a potential imaging biomarker reflecting the metastatic potential of upper urinary tract cancer

Objective:

To evaluate the role of diffusion-weighted MRI (DW-MRI) as an imaging biomarker for upper urinary tract cancer (UUTC) that has already metastasized or will metastasize soon.

Methods:

61 patients clinically diagnosed with UUTC were prospectively enrolled in this study. All the patients underwent MRI, including DW-MRI, prior to any interventions. Correlations between apparent diffusion coefficient (ADC) and other clinicopathological variables, including metastasis-free survival, were analysed.

Results:

Median follow-up period was 938 days. Of the 61 patients, 12 had any metastases at the initial diagnosis. 11 patients developed metastases during the follow-up period. These 23 patients were categorized as “Metastatic”. Of the remaining 38 patients, 35 with a follow-up period longer than 400 days were categorized as “Localized”. ADC was significantly lower in the Metastatic category than in the Localized (p = 0.0002) category. Multivariate analysis of pre-operative variables identified ADC (cut-off value, 1.08 × 10⁻³ mm² s⁻¹) and clinical T stage based on T₂ weighted MRI as an independent predictive factor of metastatic UUTC. 46 patients without any metastases during the initial diagnosis were stratified into a high-risk group (16 patients with low ADC and clinical T3–4) and a low-risk group (30 patients with high ADC or clinical Ta-2). The 3-year metastasis-free survivals were 45% and 93%, respectively.

Conclusion:

In the current study, UUTC with lower ADC value is more likely to have metastatic potential. Incorporating ADC with clinical T stage helps to differentiate metastatic UUTC at the initial diagnosis.

Advances in knowledge:

DW-MRI is a potential imaging biomarker reflecting metastatic propensity of UUTC.Upper urinary tract cancer (UUTC) is a potentially lethal disease. The prognosis remains poor even when standard care, radical nephroureterectomy (RNU) is performed, and almost one-third of the patients die within 5 years.^1–3 In the management of localized UUTC, adjuvant chemotherapy has no impact on survival, particularly owing to the impaired post-surgical renal function or comorbidity.⁴ However, neoadjuvant chemotherapy, which showed a survival benefit in bladder cancer,⁵ may have a similar benefit in UUTC.Neoadjuvant chemotherapy can be considered an option for locally advanced disease at diagnosis. Two nomograms are available for predicting locally advanced UUTC in the pre-operative setting: one includes tumour histological grade, architecture and location and the other includes histological grade and radiological clinical stage.^6,7 “Localized disease” at the initial diagnosis that will develop metastasis soon after RNU can also be a candidate for neoadjuvant chemotherapy. However, identifying these occult or developing metastases pre-operatively remains a challenge.Diffusion-weighted MRI (DW-MRI) is a functional imaging technique that reveals physiological information by quantifying the diffusion of water molecules in tissues.⁸ The extent of water diffusion is quantified as the apparent diffusion coefficient (ADC). In 2009, a consensus meeting was held on the use of DW-MRI as a cancer imaging biomarker.⁹ An extraordinary opportunity for DW-MRI to evolve into a clinically valuable imaging tool was indicated. This imaging technique has been incorporated into general oncological imaging practices, including tissue characterization, monitoring the treatment response and predicting treatment outcome, in various cancers.^8,10–14Previous studies demonstrated the role of the ADC as a marker for the biological aggressiveness of UUTC by showing a correlation of the ADC with the histological grade and the Ki-67 labelling index.^14,15 Furthermore, the ADC was significantly associated with the cancer-specific survival after RNU.¹⁵ Therefore, we hypothesized that the ADC can be used as a marker to reflect the metastatic potential of UUTC, as has been reported in bladder cancer.¹⁶ The aim of this study is to show that the ADC can predict UUTC that has already metastasized or will metastasize soon. We first evaluated ADC values of the biologically metastatic UUTC and non-metastatic UUTC. Secondarily, we analysed the potential of the ADC to predict the development of metastasis.     

Primary vaginal cancer: role of MRI in diagnosis,staging and treatment

Primary carcinoma of the vagina is rare, accounting for 1–3% of all gynaecological malignancies. MRI has an increasing role in diagnosis, staging, treatment and assessment of complications in gynaecologic malignancy. In this review, we illustrate the utility of MRI in patients with primary vaginal cancer and highlight key aspects of staging, treatment, recurrence and complications.The incidence of primary vaginal cancer increases with age, with approximately 50% of patients presenting at age greater than 70 years and 20% greater than 80 years.¹ Around 2890 patients are currently diagnosed with vaginal carcinoma in the USA each year, and almost 30% die of the disease.² The precursor for vaginal cancer, vaginal intraepithelial neoplasia (VAIN) and invasive vaginal cancer is strongly associated with human papillomavirus (HPV) infection (93%).^3,4 In situ and invasive vaginal cancer share many of the same risk factors as cervical cancer, such as tobacco use, younger age at coitarche, HPV and multiple sexual partners.^5–7 In fact, higher rates of vaginal cancer are observed in patients with a previous diagnosis of cervical cancer or cervical intraepithelial neoplasia.^7,8As is true for other gynaecologic malignancies, vaginal cancer diagnosis and staging rely primarily on clinical evaluation by the International Federation of Gynecology and Obstetrics (FIGO).⁹ Pelvic examination continues to be the most important tool for evaluating local extent of disease, but this method alone is limited in its ability to detect lymphadenopathy and the extent of tumour infiltration. Hence, FIGO encourages the use of imaging. Fluorine-18 fludeoxyglucose-positron emission tomography (¹⁸F-FDG-PET), a standard imaging tool for staging and follow-up in cervical cancer, can also be used for vaginal tumours, with improved sensitivity for nodal involvement compared to CT alone.¹⁰ In addition to staging for nodal and distant disease, CT [simulation with three dimensional (3D) conformations] is particularly useful for treatment planning and delivery of external beam radiation. MRI, with its excellent soft tissue resolution, is commonly used in gynaecologic malignancies and has been shown to be accurate in diagnosis, local staging and spread of disease in vaginal cancer.^11,12 While no formal studies are available for vaginal cancer, in cervical cancer MRI actually alters the stage in almost 30% of patients.^13–15Treatment planning in primary vaginal cancer is complex and requires a detailed understanding of the extent of disease. Because vaginal cancer is rare, treatment plans remain less well defined, often individualized and extrapolated from institutional experience and outcomes in cervical cancer.^1,16–19 There is an increasing trend towards organ preservation and treatment strategies based on combined external beam radiation and brachytherapy, often with concurrent chemotherapy,^14,20,21 surgery being reserved for those with in situ or very early-stage disease.²² Increasing utilization of MR may provide superior delineation of tumour volume, both for initial staging and follow-up, to allow for better treatment planning.²³     

Diffusion-weighted MRI in the follow-up of chronic periaortitis

Objective:

To evaluate the usefulness of diffusion-weighted MRI (DWI) for the assessment of the intraindividual follow-up in patients with chronic periaortitis (CP) under medication.

Methods:

MRI data of 21 consecutive patients with newly diagnosed untreated disease were retrospectively examined before and after medical therapy, with a median follow-up of 16 weeks. DWI parameters [b800 signal, apparent diffusion coefficient (ADC) values] of the CP and psoas muscle were analysed together with the extent and contrast enhancement. Pre- and post-treatment laboratory inflammation markers were acquired parallel to each MR examination.

Results:

Statistically significant lower b800 signal intensities (p ≤ 0.0001) and higher ADC values (p ≤ 0.0001) were observed after medical treatment within the fibrous periaortic tissue. Extent and contrast enhancement of the CP showed also a statistically significant decrease (p ≤ 0.0001) in the follow-up examinations, while the control parameters within the psoas muscle showed no differences.

Conclusion:

DWI seems to be a useful method for the evaluation of response to treatment without contrast agents. The technique may be helpful in the assessment of disease activity to guide further therapeutic strategies.

Advances in knowledge:

DWI detects significant differences in the intraindividual follow-up of CP under medical therapy.Chronic periaortitis (CP) is a proliferating fibroinflammatory disease of the perivascular retroperitoneal space and aortic wall.^1–4 Owing to adventitial inflammation, some recent theories consider CP as a large vessel vasculitis.⁵ Clinical manifestations of CP include idiopathic retroperitoneal fibrosis, inflammatory aortic aneurysm and perianeurysmal retroperitoneal fibrosis.^2,6,7 The three manifestations with very similar histopathological characteristics are distinguished by the diameter of the abdominal aorta and concomitant ureteral affection.^1,3,7Specific clinical symptoms are caused by extrinsic compression of the ureters or retroperitoneal veins, resulting in hydronephrosis, oliguria, lower extremity oedema and deep vein thrombosis.^1,8Under medical treatment with steroids, CP has a good prognosis.⁷ Today tamoxifen is suggested as a safe and effective therapeutic alternative, and immunosuppressive drugs can be considered in patients with suboptimal responses to these drugs or multiple relapses.^9–11CT and MRI are the modalities of first choice for diagnosis and follow-up of CP.^1,7,12 The fibrotic para-aortic tissue shows significant contrast uptake in gadolinium-enhanced MRI.^12–14 Dynamic contrast-enhanced MRI was suggested for the assessment of the disease activity.^15,16 However, in cases with impaired renal function (e.g. by ureteral compression), gadolinium-independent imaging methods should be preferred owing to the potential development of a nephrogenic systemic fibrosis.¹⁷Diffusion-weighted MRI (DWI) is a non-contrast MR modality that has been successfully applied for the assessment of retroperitoneal masses, inflammatory abdominal aortic aneurysms and for the differentiation between retroperitoneal fibrosis and malignant retroperitoneal neoplasms.^18–21DWI indicates restricted diffusion of water, for example caused by a high cellularity in malignant disease or active inflammation. The apparent diffusion coefficient (ADC) is a quantitative parameter for the level of restricted diffusion, which is calculated from the signals of different diffusion gradients (b-values).²²In the context of untreated CP diffusion-weighted MRI may detect restricted inflammation as a sign of high cellularity caused by active inflammation.There are no data for the evaluation of intraindividual follow-up and the response to treatment by DWI of CP so far. Therefore, the aim of the present study was to analyse differences in DWI signals during follow-up in patients with CP before and after treatment. In addition, we sought to elucidate the potential of DWI in the therapy monitoring of CP.     

The role of pre-treatment diffusion-weighted MRI in predicting long-term outcome of colorectal liver metastasis

Objective:

To determine the prognostic value of pre-treatment apparent diffusion coefficient (ADC) of colorectal liver metastases in predicting disease response, progression-free survival (PFS) and overall survival (OS).

Methods:

We retrospectively reviewed 102 patients who underwent pre-treatment diffusion-weighted MRI using a breath-hold (b=0, 150, 500) or a free-breathing (b=0, 50, 100, 250, 500, 750) technique. The mean ADC (b=0–500) and mean flow-insensitive ADC (ADC_high) values (breath-hold: b=150 and 500; free-breathing: b=100 and 500) of up to three hepatic lesions were evaluated in each patient. Clinical and laboratory parameters were recorded. Tumour response was assessed by Response Evaluation Criteria in Solid Tumors (RECIST) criteria at 12 weeks after treatment. Associations between tumour response, ADC values and clinical/laboratory parameters were examined by one-way analysis of variance. The relationship of ADC with PFS and OS was determined by Kaplan–Meier analysis.

Results:

62 patients responded to chemotherapy at 12 weeks. The pre-treatment mean ADC and mean ADC_high were higher in the non-responding group than in the responding group (1.55 vs 1.36, p=0.033; 1.40 vs 1.16, p=0.024). However, the PFS and OS of the two groups of patients stratified by the median of mean ADC values or threshold derived by receiver operating characteristic analysis were not statistically significant. By multivariate Cox regression analysis, patients with ≤2 metastases and response to chemotherapy showed better PFS; white cell count ≤10 and surgical treatment were associated with better OS.

Conclusion:

Colorectal liver metastasis with higher pre-treatment mean ADC and mean ADC_high was associated with poorer response to chemotherapy. However, ADC and ADC_high values did not predict the patient outcome in this study cohort.

Advances in knowledge:

High mean ADC values of colorectal liver metastases on pre-treatment diffusion-weighted MRI is associated with poorer response to chemotherapy.Liver metastasis from colorectal cancer is common and is associated with poor survival. It has been shown that liver metastectomy [1], radiofrequency ablation [2] and good response to chemotherapy confer a favourable long-term outcome [3]. Given the impact of adverse effects of current treatments on quality of life, knowledge on the likelihood to respond to chemotherapy, progression-free survival (PFS) and overall survival (OS) will also facilitate clinical decision making on how aggressively to pursue the various therapeutic options.There are several pre-treatment clinical factors that have been shown to affect the outcome in metastatic colorectal cancer [4]. Negative clinical predictors of outcome include platelets (plt) >400×10⁹ l⁻¹, alkaline phosphatase (ALP) >300 units per litre, white blood cell count (WCC) >10×10⁹ l⁻¹, and haemoglobin (Hb) <11×10⁹ l⁻¹. The presence of lung or lymph node metastases and the primary site being at the rectum are associated with better outlook. However, there is currently no imaging-derived prognostic index that is linked to treatment outcomes. An MRI prognostic feature is attractive because it can be derived non-invasively and may also be applied for response monitoring.The apparent diffusion coefficient (ADC), derived from diffusion-weighted MRI (DW-MRI), provides information on the microscopic movement of water molecules [5–7]. In neoplasms, ADC informs on cell membrane integrity, cellular density, extracellular space tortuosity and microstructural organisation [8,9]. Solid tumours usually return lower ADC values than their tissue of origin. In brain tumours, a pre-treatment ADC value has been shown to predict tumour response [10] and disease survival [11]. Although studies have shown that a high pre-treatment ADC value of colorectal liver metastases predicts poor response to chemotherapy [12,13], the relationship of pre-treatment ADC value and the patient clinical outcome has not been examined in abdominal malignancies.The aim of this study was to determine whether pre-treatment ADC of colorectal liver metastases is of prognostic value in predicting the patient outcome in terms of disease response, PFS and OS.     

Comparison of mammography, sonography, MRI and clinical examination in patients with locally advanced or inflammatory breast cancer who underwent neoadjuvant chemotherapy

Objectives

The purpose of this study was to determine the relative accuracies of mammography, sonography, MRI and clinical examination in predicting residual tumour size and pathological response after neoadjuvant chemotherapy for locally advanced or inflammatory breast cancer. Each prediction method was compared with the gold standard of surgical pathology.

Methods

43 patients (age range, 25–62 years; mean age, 42.7 years) with locally advanced or inflammatory breast cancer who had been treated by neoadjuvant chemotherapy were enrolled prospectively. We compared the predicted residual tumour size and the predicted response on imaging and clinical examination with residual tumour size and response on pathology. Statistical analysis was performed using weighted kappa statistics and intraclass correlation coefficients (ICC).

Results

The ICC values between predicted tumour size and pathologically determined tumour size were 0.65 for clinical examination, 0.69 for mammography, 0.78 for sonography and 0.97 for MRI. Agreement between the response predictions at mid-treatment and the responses measured by pathology had kappa values of 0.28 for clinical examination, 0.32 for mammography, 0.46 for sonography and 0.68 for MRI. Agreement between the final response predictions and the responses measured by pathology had kappa values of 0.43 for clinical examination, 0.44 for mammography, 0.50 for sonography and 0.82 for MRI.

Conclusion

Predictions of response and residual tumour size made on MRI were better correlated with the assessments of response and residual tumour size made upon pathology than were predictions made on the basis of clinical examination, mammography or sonography. Thus, the evaluation of predicted response using MRI could provide a relatively sensitive early assessment of chemotherapy efficacy.The advantages of neoadjuvant chemotherapy are multiple and it has been used widely during the past few years [1]. Its primary role is to induce tumour shrinkage and permit breast-conserving surgery, primarily in patients with advanced breast cancer [2-4]. Neoadjuvant chemotherapy allows earlier treatment of micrometastatic disease and the study of biological markers that might predict tumour response [5]. The effectiveness of chemotherapeutic agents in treating both primary breast cancer and potential metastatic disease may be enhanced by the presence of tumour neovascularity. If chemotherapy is given before surgery, while tumour vascularity remains intact, the chemotherapeutic agents may be better able to reach the tumour and thus be more effective.Neoadjuvant chemotherapy of locally advanced breast cancer (LABC) has also been shown to improve the resectability rate, offering disease-free and overall survival rates that are at least equivalent to those offered by surgery alone [6,7]. Pathological complete response (pCR) is clinically significant because it is associated with improved long-term prognosis and decreased risk of recurrence [6,8]. Decisions regarding the continuation of current regimens and the appropriate type and timing of surgery depend on the radiological and clinical assessment of residual tumour size during neoadjuvant chemotherapy [9,10]. Until now, many studies have shown that physical examinations, mammography and sonography provide suboptimal evaluations of lesion extent that do not allow accurate assessments of pathological response or residual tumour size [5^,11-13]. In the case of LABC, physical examination, mammography or sonography may be suitable for detecting the larger lesions of non-responders, but they have limited sensitivity for responders with smaller residual lesions [14,15]. For mammography, calcifications may persist or even increase in patients who respond to neoadjuvant chemotherapy [14,16,17].Many previous studies have shown that MRI is the most reliable technique for evaluating residual disease after neoadjuvant chemotherapy, although initial reports described frequent false-negatives with smaller-volume disease [18-27]. Recent studies have increased the sensitivity of MRI, with increased resolution, reduced slice thickness and lower enhancement thresholds being used to minimise the underestimation of residual disease [15^,22-27]. It is still difficult, however, to distinguish residual scarring, necrosis and fibrosis from viable residual malignancy and to predict accurate response after neoadjuvant chemotherapy, especially in responders. Few published studies have described work with patients with inflammatory breast cancer who underwent neoadjuvant chemotherapy because the incidence of this disease is very low [28,29]. The purpose of our study was to determine the relative accuracies of mammography, sonography, MRI and clinical examination in predicting residual tumour size and pathological response after neoadjuvant chemotherapy for locally advanced and inflammatory breast cancer. We compared each prediction method with the gold standard of surgical pathology.     

Prognostic factors associated with a subchondral insufficiency fracture of the femoral head

Objective

The aim of this study was to identify the risk factors associated with the prognosis of a subchondral insufficiency fracture of the femoral head (SIF).

Methods

Between June 2002 and July 2009, 25 patients diagnosed with SIF were included in this study. Sequential radiographs were evaluated for the progression of collapse. Clinical profiles, including age, body mass index, follow-up period and Singh’s index, were documented. The morphological characteristics of the low-intensity band on T₁ weighted MRI were also examined with regards to four factors: band length, band thickness, the length of the weight-bearing portion and the band length ratio (defined as the proportion of the band length to the weight-bearing portion of the femoral head in the slice through the femoral head centre).

Results

Radiographically, a progression of collapse was observed in 15 of 25 (60.0%) patients. The band length in patients with progression of collapse [22.5 mm; 95% confidence interval (CI) 17.7, 27.3] was significantly larger than in patients without a progression of collapse (13.4 mm; 95% CI 7.6, 19.3; p<0.05). The band length ratio in patients with progression of collapse (59.8%; 95% CI 50.8, 68.9) was also significantly higher than in patients without a progression of collapse (40.9%; 95% CI 29.8, 52.0; p<0.05). No significant differences were present in the other values.

Conclusion

These results indicate that the band length and the band length ratio might be predictive for the progression of collapse in SIF.Subchondral insufficiency fractures of the femoral head (SIF) often occur in osteoporotic elderly patients [1-9]. Patients usually suffer from acute hip pain without any obvious antecedent trauma. Radiologically, a subchondral fracture is seen primarily in the superolateral portion of the femoral head [4,5,10]. T₁ weighted MRI reveal a very low-intensity band in the subchondral area of the femoral head, which tends to be irregular, disconnected and convex to the articular surface [2,4,5,7,9,11]. This low-intensity band in SIF was histologically proven to correspond with the fracture line and associated repair tissue [5,9]. Some cases of SIF resolve after conservative treatment [5,11-14]; other cases progress until collapse, thereby requiring surgical treatment [4-10,15]. The prognosis of SIF patients remains unclear.The current study investigated the risk factors that influence the prognosis of SIF based on the progression to collapse.     

Visualisation of liver tumours using hand-held real-time strain imaging: results of animal experiments

Objective

Surgical resection is the only curative option for colorectal hepatic metastases. Intra-operative localisation of these metastases during hepatic resection is performed by intra-operative B-mode imaging and palpation. Because liver metastases are stiffer than normal tissues, elastography may be a useful complement to B-mode imaging. This paper reports quantitative measures of the image quality attained during intra-operative real-time elastographic visualisation of liver metastasis.

Methods

VX2 tumours were implanted in the liver of eight rabbits and were scanned in vivo. Measurements of the tumour dimensions obtained via elastography were compared with those obtained using B-mode imaging and with gross pathology.

Results

Measurements of tumour diameters were similar when obtained by intra-operative elastography and pathological measurement methods (mean difference±standard deviation, 0.1±0.9 mm). The contrast between tumours and normal tissues was significantly higher (p<0.05) in elastograms (26±10 dB contrast) than in sonograms (1±1 dB contrast). Sensitivity and specificity for detecting tumours using intra-operative elastography were 100% and 88%, respectively, and positive and negative predictive values were 89% and 100%, respectively. In two cases elastograms were able to detect a tumour that was ambiguous in B-mode images.

Conclusion

Combined hand-held B-mode/strain imaging may provide additional information that is relevant for detection of liver metastases that may be missed by standard B-mode imaging alone, such as small and/or isoechoic tumours.Colorectal cancer is the fourth most common cancer in males and the third most common cancer in females worldwide [1,2]. Approximately half of these patients either present with hepatic metastases or develop them during the course of their disease. Although ablative therapies are frequently used, resection of liver metastases, when possible, remains the preferred therapy for potential cure [3,4]. The overall 5 year survival rates are in the range of 35–58% in several studies reporting on the results of hepatectomy conducted with curative intent [4,5]. The pre-operative and intra-operative staging of metastases is essential to remove all metastases and increase the rate of cure. At the pre-operative stage, contrast-enhanced CT is the most commonly used modality to screen for metastases. It is highly sensitive, particularly since the introduction of helical CT and multidetector systems capable of scanning the entire liver in a few seconds, allowing for several scans during the liver''s different circulatory phases [6]. MRI is very sensitive as well, and has the advantage of liver-specific contrast if required. MRI is also used for screening purposes, despite the fact that it is more time-consuming than other methodologies and may be subject to motion artefacts [7]. According to different reports, these modalities detect >90% of liver metastases if their diameter is >5 mm [7,8]. There is still a group of patients who undergo hepatic surgery without correct pre-operative diagnosis [8,9]. The use of intra-operative ultrasound (IOUS) with or without contrast agents has proved to be efficient in finding, during hepatectomy, metastases that were not detected by pre-operative examinations [9,10]. IOUS has been shown to yield significant new information, not identified on pre-operative imaging, which determines the resectability of the metastasis or changes the operative plan. IOUS is considered the gold standard, thereby achieving universal usage [9,11]. However, the rate of hepatic recurrence following apparently curative liver resection is about 40% at 3 years [12]. This underlines the limitation of IOUS itself, and the need for a more accurate imaging technique cannot be overemphasised. The missed tumours may be small, isoechoic, deeply located or positioned in regions that are difficult to image [13,14]. Therefore, surgeons also use visual and tactile sensory information intra-operatively to evaluate differences in mechanical properties between normal livers and tumours. Palpation provides tactile sensory information regarding the mechanical properties of materials intra-operatively. Palpation involves the application of a stress, with evaluation of the resultant displacement, strain and other mechanical responses that are thus subjectively evaluated. The primary mechanical property that is frequently evaluated when surgeons palpate hepatic tumours intra-operatively to assist resection is the relative stiffness of the liver when compared with a tumour. Stiffer tissues strain less than softer tissues under similar conditions, and tumours generally tend to be stiffer than normal livers. Therefore, ultrasonic elastography is an ideal imaging modality for probing the bioelasticity distribution in biological tissues [15]. The technique is based on the strain-gauge principle, according to which the stiff tissue strains less than soft tissue and when deformed externally by a mechanical compression. Because the stiffness rather than the backscatter is sensed remotely, tumours that are not detectable on sonograms might often be revealed with good resolution and good contrast in elastograms. Real-time ultrasound elastography is now used in a widespread manner in the clinic, and these systems have become commercially available [16-19].Our long-term objective is to incorporate elasticity imaging within a medical device for the treatment of liver metastases using high-intensity focused ultrasound (HIFU) for eventual clinical use. In previous studies [20,21], we have described the use of a toroidal transducer for HIFU ablation, which could represent a promising alternative for treating colorectal liver metastases. This device is designed to be used during surgery. We have also shown that elastography is useful in the evaluation of the region that has been ablated using this device [22]. In this article, we explore the feasibility of utilising hand-held real-time elastography for the visualisation of metastases. The hand-held approach was chosen to provide a straightforward complement to conventional B-mode images, which are currently used to define the extent of the metastatic disease. In vivo studies using a rabbit model of a liver tumour were conducted in order to provide quantitative measures of the image quality attained during intra-operative real-time elastographic visualisation of liver metastasis. During these experiments, the ability of extracorporeal strain images to detect these tumours was also evaluated as a secondary objective.     

MRI manifestations of soft-tissue haemangiomas and accompanying reactive bone changes

Objectives

Soft tissue haemangiomas are common benign vascular lesions that can be accompanied by reactive changes in the adjacent bone structure. This study aimed to discuss the MRI features of soft-tissue haemangiomas with an emphasis on changes in bone.

Methods

The radiographic and MRI findings of 23 patients (9 males, 14 females; mean age 25 years; age range 2–46 years) with soft-tissue haemangiomas were analysed retrospectively. MR images were evaluated for location of the lesion, size, configuration, signal features, contrast patterns, proximity to adjacent bone and changes in the accompanying bone. Excisional biopsy was performed in 15 patients.

Results

Radiographs demonstrated phleboliths in 8 patients (34%) and reactive bone changes in 4 (19%). On MRI, T₁ weighted images showed that most of the lesions were isointense or isohyperintense, as compared with muscle tissue; however, on T₂ weighted images all lesions appeared as hyperintense. Following intravenous gadolinium-diethylene triamine pentaacetic acid (DTPA) administration, homogeneous enhancement was observed in 3 lesions and heterogeneous enhancement was seen in 19. No enhancement was observed in one patient. Bone atrophy adjacent to the lesion was observed in four patients.

Conclusion

MRI is the most valuable means of diagnosing deep soft-tissue haemangiomas. Bone changes can accompany deeply situated haemangiomas; in four of our patients, we found atrophy of the bone adjacent to the lesion. To our knowledge, this is the first report in the literature regarding atrophy of the bone adjacent to a lesion.Soft-tissue haemangioma, a frequently encountered benign vascular lesion, accounts for 7% of all benign soft-tissue tumours [1-5]. Such lesions can be cutaneous, subcutaneous, intramuscular or synovial [1]. Intramuscular haemangioma is rare and responsible for 0.8–1.8% of all haemangiomas [3,5,6]. Superficial haemangiomas are diagnosed easily because they cause discolorations of the skin; imaging techniques are rarely needed [1]. However, deep lesions are difficult to diagnose clinically, because they do not cause discolorations and grow slowly; imaging techniques are required to discriminate these deep haemangiomas from malignant lesions [1,2,7]. Bone changes accompanying haemangioma have been reported previously in the literature and include cortical thickening, erosion, medullary sclerosis, trabecular coarsening and hypertrophy [1,8]. Here, we present the MRI manifestations of soft-tissue haemangiomas and reactive changes to the neighbouring bones. To the best of our knowledge, this is the first report of its kind in the English literature.     

Pancreatic ductal adenocarcinoma with intratumoral cystic lesions on MRI: correlation with histopathological findings

The purpose of this study was to evaluate intratumoral cystic lesions of pancreatic ductal adenocarcinoma (PDAC) depicted on MRI, and to correlate these cystic lesions with their histopathological findings. This study included 12 patients (7 males and 5 females; mean age, 59 years) with intratumoral cystic lesions of PDAC detected on a retrospective MRI review. We reviewed the histopathological findings of the cystic lesions within PDACs and analysed the MRI findings, focusing on the appearance of the intratumoral cystic lesions, i.e. the size, number, margin and intratumoral location, and on the ancillary findings of PDAC, i.e. peripancreatic infiltration, upstream pancreatic duct dilatation and distal parenchymal atrophy. Intratumoral cystic lesions were classified as neoplastic mucin cysts (n = 7, 58%) or cystic necrosis (n = 5, 42%) according to the histopathological findings; they ranged in greatest dimension from 0.5 cm to 3.4 cm (mean, 1.7 cm). Seven patients had only one cystic lesion each, while the remaining five had multiple cystic lesions. Most of the neoplastic mucin cysts had smooth margins (n = 6, 86%) and eccentric locations (n = 6), whereas most cystic necroses had irregular margins (n = 4, 80%) and centric locations (n = 4). The most common ancillary findings of PDAC were peripancreatic infiltration, distal pancreatic atrophy and upstream pancreatic duct dilatation (92%, 75% and 58%, respectively). The intratumoral cystic lesions of PDACs on MRI were classified as either neoplastic mucin cysts with smooth margins and eccentric locations or cystic necroses with irregular margins and centric locations.Pancreatic cancer is the fifth leading cause of cancer-related death in both men and women and is responsible for 5% of all cancer-related deaths in the United States [1]. Despite the advances in surgical techniques, as well as the major improvements in chemotherapy and radiotherapy protocols, the prognosis of pancreatic ductal adenocarcinoma (PDAC) usually implies a 1-year survival rate of <20% and a 5-year survival rate of <5% [2].PDAC typically presents as an irregular solid tumour with a scirrhous character resulting from a prominent desmoplastic reaction. However, recent studies have shown that PDAC may be accompanied by cystic changes within or adjacent to the mass, and that the incidence of PDAC with cystic changes ranges from <1% to 8% [3, 4]. Radiologists should be familiar with PDACs with cystic changes as they may resemble more common cystic pancreatic lesions, such as pseudocysts, intraductal papillary mucinous neoplasms (IPMNs), solid pseudopapillary tumours and non-functioning islet cell tumours, all of which are managed differently and usually have better patient survival rates [5–7].Many studies have discussed the radiological appearance of PDAC accompanied by cystic lesions [6–11]. Most of these studies have discussed pseudocysts or retention cysts depicted adjacent to the PDAC or in the extrapancreatic area in the clinical setting of pancreatitis [8–11], whereas only a few studies have discussed intratumoral cystic lesions, such as cystic necroses, in larger ordinary PDACs [6, 7]. Some case reports have described the intratumoral cystic changes of PDAC variants, i.e. adenosquamous carcinoma [12], mucinous adenocarcinoma (colloid or mucinous non-cystic carcinoma) [13], osteoclast-like giant cell carcinoma [14] and pleomorphic giant cell carcinoma [15]. To the best of our knowledge, there have been no radiological reports regarding the intratumoral cystic lesions of ordinary PDAC. Compared with CT, MRI has the advantage of being able to detect cystic changes within pancreatic masses and to provide more accurate morphological detail on these changes [16]. Therefore, the aims of this study were to evaluate intratumoral cystic lesions of ordinary PDAC detected on MRI and to correlate the cystic lesions with their histopathological findings.     

Compromised perfusion in femoral head in normal rats: distinctive perfusion MRI evidence of contrast washout delay

Objectives

The femoral head is prone to osteonecrosis. This study investigated dynamic contrast-enhanced (DCE) MRI contrast washout features of the femoral head and compared the data with data from other bony compartments in normal rats.

Methods

7-month-old Wistar rats were used. DCE MRI of the right hip (n=18), right knee (n=12) and lumbar spine (n=10) was performed after an intravenous bolus injection of Gd-DOTA (0.3 mmol kg^–1). Temporal resolution was 0.6 s for hip and spine, and 0.3 s for knee. The total scan duration was 8 min for hip and spine, and 4.5 min for knee. The regions of interest for enhancement measurement included femoral head, proximal femoral diaphysis, distal femoral diaphysis and epiphysis, proximal tibial epiphysis and diaphysis, and lumbar vertebrae L1–5.

Results

Femoral head showed no enhancement signal decay during the DCE MRI period, while all other bony compartments showed a contrast washin phase followed by a contrast washout phase. In the knee joint, the contrast washout of the proximal tibia diaphysis was slower that of other bony compartments of the knee.

Conclusion

Based on the evidence of delayed contrast washout, this study showed that blood perfusion in the femoral head could be compromised in normal rats.Clinical studies have shown that the femoral head has a poorer blood supply compared with the femoral neck and femoral shaft [1,2]. MRI-derived perfusion indices of maximum enhancement and enhancement slope for the femoral head were only about one-fifth to one-quarter of those for the femoral shaft in healthy elderly male and female subjects [1]. Because of the absence of an effective collateral circulation, the femoral head is at an especially high risk of ischaemic injury [3]. Osteonecrosis of the femoral head may be idiopathic or secondary to numerous diseases. Bone perfusion can affect bone metabolism and microdamage repair. Osteonecrosis can have early vascular components that change underlying bone perfusion in the affected bone and joint, and contribute to the clinical cascade of disease [4]. Relatively mild haemodynamic impairment, which may not necessarily compromise other sites, has the potential to cause osteonecrosis of the femoral head [1,5,6]. In animals, osteonecrosis of the femoral head is sporadically encountered in dogs [7]. Perthes disease-like necrosis of the femoral head and neck occurs in some breeds of small dogs [7]. Osteonecrosis of the femoral head is also seen in spontaneously hypertensive rats [8-10]. Recently it was reported that delayed washout in dynamic contrast-enhanced (DCE) MRI suggests compromised blood perfusion in the tissue, including blood stasis or outflow obstruction [11]. It was also reported that delayed contrast washout could be seen in sites of bone marrow oedema, osteoarthritis and avascular osteonecrosis [11]. This study investigated DCE MRI contrast washout features of the femoral head in normal mature rats. The results from the femoral head were compared with the data from proximal and distal femoral diaphysis, distal femoral epiphysis, proximal tibial epiphysis and diaphysis, and lumbar vertebral bodies.     

Vascular invasion in hepatocellular carcinoma: is there a correlation with MRI?

Objective

Hepatocellular carcinoma (HCC) is one of the commonest malignancies worldwide. Prognosis is predicted by size at diagnosis, vascular invasion and tumour proliferation markers. This study investigates if MRI features of histologically proven HCCs correlate with vascular invasion.

Methods

Between 2006 and 2008, 18 consecutive patients, with a total of 27 HCCs, had comprehensive MRI studies performed at our institution within a median of 36 days of histology sampling. Each lesion was evaluated independently on MRI by 3 radiologists (blinded to both the radiology and histopathology reports) using a 5-point confidence scale for 23 specific imaging features. The mean of the rating scores across readers was calculated to determine interobserver consistency. The most consistent features were then used to examine the value of features in predicting vascular invasion, using a χ² test for trend, having eliminated those features without sufficient variability.

Results

22 of the 23 imaging features showed sufficient variability across lesions. None of these significantly correlated with the presence of vascular invasion, although a trend was identified with the presence of washout in the portal venous phase on MRI and the median size of lesions, which was greater with vascular invasion.

Conclusion

This study suggests that no single MRI feature accurately predicts the presence of vascular invasion in HCCs, although a trend was seen with the presence of washout in the portal venous phase post gadolinium. Larger prospective studies are required to investigate this further.Hepatocellular carcinoma (HCC) is one of the commonest malignancies worldwide, either arising de novo or on a background of cirrhosis. The incidence in Western countries is rising owing to increasing rates of alcoholic liver disease and hepatitis C infection. Untreated, the 5-year survival rate for symptomatic HCC is less than 5% [1]. At present, surgery is the only potentially curative treatment for HCC with options including either a partial hepatectomy or orthotopic liver transplantation (OLT). Following resection there is a 5-year survival rate of 40–50% [2] with a cumulative 5-year recurrence rate between 75 and 100% [3]. The 5-year survival rate in patients with cirrhosis following transplantation of small (<2 cm) HCC is up to 80% [4]. However, the use of OLT is limited owing to the lack of donor livers. Regional therapies such as transcatheter arterial chemoembolisation [5] and percutaneous radiofrequency ablation [6] may improve prognosis. The value of neo-adjuvant and adjuvant chemotherapy and immunotherapy in prolonging survival remains controversial [7,8]. However, a recent study evaluating sorafenib, a multikinase inhibitor, in patients with advanced HCC has shown an increased median overall survival of 2.8 months over a placebo [9].Studies of patients with explanted liver for end-stage cirrhosis have shown that MRI, with the use of dynamic gadolinium-enhanced sequences, has a moderate sensitivity for the detection of HCC of between 55 and 91% [10-12] and specificity between 55 and 86% [11-13]. The sensitivity is lower with lesions <2 cm in size [11-13]. In patients with cirrhosis, HCC is thought to develop as part of a spectrum of de-differentiation from regenerative nodule through to low-grade dysplastic nodule, high-grade dysplastic nodule, then to frankly malignant. Early diagnosis using non-invasive imaging leads to an improved prognosis but at present, unless biopsy is performed, only lesion size is used to determine patient management in those where gross vascular involvement or metastatic spread precludes curative treatment.Several factors predicting outcome have been identified including tumour pathological factors (such as size, stage, grade, the presence of vascular invasion, portal vein tumour thrombus and intrahepatic metastases) [14,15], the patient’s hepatitis status, the patient’s functional liver reserve [16] and the serum α-fetoprotein level [17]. Overall, one of the most strongly correlated factors is the presence or absence of vascular invasion. There is a 4.4- and 15-fold increased risk of recurrence following OLT for HCC in patients with micro- or macrovascular invasion, respectively [18].The aims of this retrospective study were twofold. First to identify the interobserver variability of MRI features for patients with histologically proven HCC, and second to determine if there was a correlation between imaging features on MRI and histologically defined vascular invasion; these MRI features could then serve as a surrogate marker of prognosis. There has been little literature to date attempting to correlate MRI features with microvascular invasion.