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.     

Pseudotumours in chronic kidney disease: Can diffusion-weighted MRI rule out malignancy

Objectives

To evaluate whether diffusion-weighted MRI (DW-MRI) can distinguish pseudotumours in chronic kidney disease (CKD pseudotumours) from renal-cell-carcinomas (RCCs) (with or without CKD) and whether it offers additional benefit over conventional MRI.

Methods

One-hundred patients underwent MDCT, MRI and DW-MRI (at b-values of 0 and 500 s/mm²) for evaluation of focal renal lesions. Of these, 20 patients with 40 CKD pseudotumours and 36 patients with 40 RCCs were retrospectively analyzed. T1-weighted, T2-weighted, diffusion-weighted images were evaluated, apparent-diffusion-coefficient (ADC) values were compared and receiver-operating-characteristic (ROC) curves were drawn to establish cut-off ADC-values.

Results

92.5% of CKD pseudotumours remained indeterminate after conventional MRI. On DW-MRI, none of them showed restricted diffusion and thus malignancy could be ruled out in 100% of the lesions. In contrast, all the solid RCCs showed diffusion restriction. Mean ADC-value for CKD pseudotumours was significantly higher than RCCs and surrounding diseased parenchyma [2.50 vs 1.56 (×10⁻³ mm²/s) (P < 0.0001) and 2.05 (×10⁻³ mm²/s) (P = 0.0001) respectively]. ROC analysis for differentiating CKD pseudotumours and RCC yielded high sensitivity (91.7%) and specificity (100%) for cut-off ADC-value of 2.04 (×10⁻³ mm²/s).

Conclusions

CKD pseudotumors usually remain indeterminate on conventional non-contrast MRI. DW-MRI can distinguish CKD pseudotumors from RCCs and offers a non-contrast non-invasive alternative for ruling out malignancy.     

Apparent diffusion coefficient (ADC) in liver fibrosis: Usefulness of normalized ADC using the spleen as reference organ

Objective

The purpose of the current study was to determine the usefulness of the usage of the spleen as a reference organ to normalize liver ADC to improve the diagnostic performance of diffusion weighted imaging (DWI) for assessing liver fibrosis.

Materials and methods

Forty-nine subjects, 34 patients with liver disease and 15 control subjects were assessed with diffusion-weighted imaging. Liver ADC and normalized liver ADC (defined as the ratio of liver ADC to spleen ADC) were compared between patients and the control groups as well as among patients with different stages of fibrosis. Receiver operating characteristic (ROC) analysis was used to determine the performance of ADC and normalized liver ADC for prediction of liver fibrosis and cirrhosis.

Results

There was no significant difference between spleen ADC values among patients in comparison to control (1.107 ± 0.07 × 10⁻³mm²/s vs. 1.12 ± 0.068 × 10⁻³mm²/s, p = 0.998) or among patients with different stages of fibrosis (p = 0.59–0.89). The mean liver ADC and mean normalized liver ADC values were significantly lower in patients with hepatic fibrosis compared to volunteers (P = 0.01,<0.001 respectively), however liver ADC could not significantly differentiate different stages of fibrosis except between stages 0 and 4. The mean normalized liver ADC was significantly different between stage 0 and stages 2, 3, and 4 as well as between stage 1 and stage 4. In addition, it had a trend toward significance between stage 0 and 1, stage 2 and 4 as well as stage 3 and 4. Both liver ADC and normalized liver ADC had a significant negative correlation with the grade of fibrosis, however it was more powerful for normalized liver ADC in comparison to liver ADC (r = −0.694 vs. −0.361, p = 0.01 vs. 0.05). ROC analysis showed higher performance using normalized liver ADC in comparison to liver ADC, with higher AUC, sensitivity, and specificity for detection of fibrotic stages ?2 (0.88, 92.5% and 76.2% Vs 0.72, 82.1%, and 57.1% respectively). The corresponding values for stages ?3 were 0.83, 100%, and 55% vs. 0.69, 77.3%, and 44.4% respectively), while the corresponding values for cirrhosis (stage 4) were 0.87, 81.8%, and 81.8% for normalized liver ADC vs. 0.74, 69.2%, 72.2%.for ADC liver.

Conclusion

The utility of using the spleen as a reference organ could improve the diagnostic performance of ADC measurement for the diagnosis of liver fibrosis. The application of this technique for the evaluation of liver fibrosis is promising.     

Diffusion weighted MR imaging in patients with HCC and liver cirrhosis after administration of different gadolinium contrast agents: Is it still reliable?

Purpose

Diffusion weighted imaging (DWI) is an emerging technique for abdominal MR and usually performed before intravenous contrast injection. Recent studies performed in patients with normal liver function have shown that DWI can be performed after gadolinium administration. Aim of this study was to compare DWI before and after administration of different gadolinium compounds in patients with HCC and liver cirrhosis.

Materials and methods

15 patients with known HCC and liver cirrhosis underwent liver MRI at 1.5 T (Magnetom Avanto, Siemens) including DWI on day 1 before and after administration of gadobutrol (Gadovist^®) and on day 2 after administration of EOB-Gadolinium-DTPA (Primovist^®). Signal to noise ratios (SNR) and contrast to noise ratios (CNR) of HCC lesions were determined for all DWI data sets. Furthermore, ADC values were compared using a Wilcoxon test. A p-value <0.05 indicated statistically significant differences.

Results

There were no statistically significant differences regarding SNR pre-contrast (mean: 48.1), after gadobutrol (mean: 47.7) or after EOB-Gadolinium-DTPA (mean: 50.0; values for b = 50 s/mm²). Similarly, no significant differences were found for CNR (average values:34.4 vs. 32.3 vs. 30.7; b = 50 s/mm²) nor for ADC-values (mean: 1.5 vs. 1.4 vs. 1.5 × 10⁻³ mm²/s) of HCC.

Conclusion

There is no significant difference regarding DWI in patients with cirrhosis before and after contrast injection. Hence, it is reliable to run DWI after gadolinium either as an alternative for unsuccessful pre-contrast DWI or as a gap filler to spare time in EOB-Gadolinium-DTPA imaging.     

Diagnostic performance of conventional diffusion weighted imaging and diffusion tensor imaging for the liver fibrosis and inflammation

Objective

To evaluate the diagnostic accuracy of liver apparent diffusion coefficient (ADC) measured with conventional diffusion-weighted imaging (CDI) and diffusion tensor imaging (DTI) for the diagnosis of liver fibrosis and inflammation.

Materials and methods

Thirty-seven patients with histologic diagnosis of chronic viral hepatitis and 34 healthy volunteers were included in this prospective study. All patients and healthy volunteers were examined by 3 T MRI. CDI and DTI were performed using a breath-hold single-shot echo-planar spin echo sequence with b factors of 0 and 1000 s/mm². ADCs were obtained with CDI and DTI. Histopathologically, fibrosis of the liver parenchyma was classified with the use of a 5-point scale (0–4) and inflammation was classified with use of a 4-point scale (0–3) in accordance with the METAVIR score. Quantitatively, signal intensity and the ADCs of the liver parenchyma were compared between patients stratified by fibrosis stage and inflammation grade.

Results

With a b factor of 1000 s/mm², the signal intensity of the cirrhotic livers was significantly higher than those of the normal volunteers. In addition, ADCs reconstructed from CDI and DTI of the patients were significantly lower than those of the normal volunteers. Liver ADC values inversely correlated with fibrosis and inflammation but there was only statistically significant for inflammatory grading. CDI performed better than DTI for the diagnosis of fibrosis and inflammation.

Conclusion

ADC values measured with CDI and DTI may help in the detection of liver fibrosis. They may also give contributory to the inflammatory grading, particularly in distinguishing high from low grade.     

Diffusion weighted MRI in chronic viral hepatitis C: Correlation between apparent diffusion coefficient values and histopathological scores

Aim of the work

To assess the utility of hepatic ADC of diffusion weighted MRI in the diagnosis of liver fibrosis in chronic hepatitis C patients and to evaluate its relationship with both the stage of liver fibrosis and grade of necro-inflammation.

Subjects and methods

Forty patients with chronic viral hepatitis C and 30 healthy control group were examined by 1.5 T MRI scanner using DWI at b-values of 100, 400 and 800 s/mm². The mean ADC values of both patients and the control group were correlated to biopsy findings and graded according to METAVIR scoring system.

Results

The mean ADC values of the liver at all b-values were statistically significantly lower in the study group than those of the control group. A strong negative correlation was found between the mean ADC value and the stage of fibrosis. No significant correlation was found between the mean ADC value and the grade of necroinflammation.

Conclusion

The ADC value of diffusion weighted MRI can be used to distinguish between liver parenchyma of patients with chronic viral hepatitis C and healthy subjects and it is useful for estimation of the stage of liver fibrosis but not valuable in estimation of the grade of necro-inflammation.     

The role of MR diffusion in differentiation of malignant and benign hepatic focal lesions

Aim

To determine if focal liver masses could be differentiated as benign or malignant by DWI and ADC maps.

Methods and materials

Sixty focal liver lesions were scanned using 1.5 T MRI. DWI was performed with b 0, b 500 and b 1000 gradients with ADC measurements. Comparison of mean ADC values between each benign and malignant lesion was done. Reference standard of diagnosis was obtained by correlating DWI with histopathologic findings and imaging follow-up. The accuracies of DWI and ADC values were assessed with the Student’s t test, and cut-off values were determined with receiver operating characteristic curve analysis.

Results

When ADC value of 1.0 × 10⁻³ mm²/s was used as a threshold value for differentiation of malignant tumors from benign lesions, sensitivity was 90.3%, specificity 78.57% and accuracy 86.7%. The best result was obtained with the use of ADC cut off value (at b 500) of 1.5 × 10⁻³ mm²/s and ADC cut off value (at b 1000) of 1.0 × 10⁻³ mm²/s, with 90.3% sensitivity, 92.86% specificity, 91.1% accuracy, 96.6% positive predictive value and 81.3% negative predictive value.

Conclusion

DWI and ADC map is a useful tool in differential diagnosis of malignant from benign liver lesions.     

Diffusion-weighted MRI versus transient elastography in quantification of liver fibrosis in patients with chronic cholestatic liver diseases

Purpose

To evaluate the diagnostic value of diffusion-weighted magnetic resonance imaging (DWMRI) and transient elastography (TE) in quantification of liver fibrosis in patients with chronic cholestatic liver diseases.

Materials and methods

Forty-five patients underwent DWMRI, TE, and liver biopsy for staging of liver fibrosis. Apparent diffusion coefficient (ADC) was calculated for six locations in the liver for combination of five diffusion sensitivity values b = 0, 50, 200, 400 and 800 s/mm². A receiver operating characteristic (ROC) analysis was performed to determine the diagnostic performance of DWMRI and TE. Segmental ADC variations were evaluated by means of coefficient of variation.

Results

The mean ADCs (×10⁻³ mm²/s; b = 0–800 s/mm²) were significantly different at stage F1 versus F ≥ 2 (p < 0.05) and F2 versus F4. However, no significant difference was found between F2 and F3. For prediction of F ≥ 2 and F ≥ 3 areas under the ROC curves were 0.868 and 0.906 for DWMRI, and 0.966 and 0.960 for TE, respectively. The sensitivity and specificity were 90.9% and 89.3% for F ≥ 2 (ADC ≤ 1.65), and 92.3% and 92.1% for F ≥ 3 (ADC ≤ 1.63). Segmental ADC variation was lowest for F4 (CV = 9.54 ± 6.3%).

Conclusion

DWMRI and TE could be used for assessment of liver fibrosis with TE having higher diagnostic accuracy and DWMRI providing insight into liver fibrosis distribution.     

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 value of diffusion weighted magnetic resonance image in early ankylosing spondylitis

Background

Diffusion-weighted MRI (DW-MRI) shows the early changes in microscopical movement of water molecules, hence diagnosis of early sacroiliitis which is one of the diagnostic criteria of seronegative spondyloarthropathies.

Objective

To determine the value of DW-MRI in detection of signal characteristics of the sacroiliac joints in patients with early ankylosing spondylitis (AS).

Patients and methods

Fifteen patients with clinically suspected AS, 20 patients with mechanical low back pain and 20 healthy controls underwent conventional MRI and DWI. Apparent diffusion coefficient (ADC) was measured. In addition ten clinically confirmed AS patients underwent whole body-DWI.

Results

Mean ADC values of both sacroiliac joints in AS patients were (0.523 ± 0.15) × 10⁻³ mm²/s in the ilium and (0.502 ± 0.15) × 10⁻³ mm²/s in the sacrum. There was no significant difference between mechanical LBP and healthy controls. But there was a significant difference between AS and LBP patients. Mean ADC value of focal lesions of clinically confirmed AS was 0.965 ± 0.25 × 10⁻³ mm²/s in the sacrum and 0.932 ± 0.31 × 10⁻³ mm²/s in the ilium.

Conclusion

Subchondral bone marrow ADC values of sacroiliac joints allow differentiation between inflammatory and mechanical LBP. Furthermore, it may be helpful in evaluating the efficacy of the treatment and determine disease prognosis.     

Diagnostic performance of breast MRI with and without the addition of quantitative diffusion weighted imaging

Objective

The purpose of our study was to investigate whether adding diffusion weighted imaging to dynamic contrast-enhanced MRI could improve the diagnostic performance of breast MRI.

Materials and methods

This retrospective study included 86 women with 93 primary and postoperative breast lesions detected on DCE-MRI who underwent subsequent biopsy. The diagnostic performance was calculated for DCE-MRI alone, combined DCE-MRI and quantitative DWI, and for quantitative DWI alone.

Results

Of the 93 lesions, 42 were benign and 51 malignant (5 DCIS, 41 IDC, 2 ILC, 3 NOS). Both DCIS (mean ADC = 1.17 ± 0.12 × 10⁻³ mm²/s) and IDC (mean ADC, 0.98 ± 0.14) exhibited lower mean ADC values than benign lesions (ADC value = 1.72 ± 0.36). Applying an ADC cutoff value of 1.33 increased the specificity and PPV of DCE-breast MRI from 59.5% and 75% to 78.5% and 83.3%, respectively. The specificity and PPV for quantitative DW-MRI alone (73.5% and 83.3%) were close to those broken out from the combined use of DCE and quantitative DW-MRI. However, the sensitivity and NPV of DWI remains lower than that of DCE-MRI.

Conclusion

DWI shows potential for improving the diagnostic performance of breast MRI and may reduce the number of unnecessary biopsies.     

Diagnostic value of apparent diffusion coefficient calculated with diffusion-weighted MRI for quantification of liver fibrosis

Aim of the work

To evaluate the diagnostic values of the hepatic ADC calculated with diffusion-weighted MRI for quantification of the hepatic fibrosis in patients with chronic viral hepatitis.

Subjects and methods

Thirty-eight chronic viral hepatitis C patients with similar control group were examined by 1.5 Tesla MR scanner with diffusion gradient encoding in three orthogonal directions at b values of (300, 500, 700, and 1000 s/mm²). They were correlated to biopsy finding and graded according to Ishak scoring system. Hepatic ADC values were measured for both patients and control groups.

Results

The best correlation between ADC values and biopsy were seen at b values 300, 700, and 1000 s/mm², which showed high sensitivity, specificity, positive, and negative predictive values, with lesser correlation were obtained at b values of 500 s/mm². Cut off values between different grades of fibrosis were calculated and presented in the text.

Conclusion

ADC measured with DWI is a reliable non-invasive technique for quantification of liver fibrosis, and could replace liver biopsy in certain cases.     

Diffusion-weighted MRI of the prostate at 3.0 T: Comparison of endorectal coil (ERC) MRI and phased-array coil (PAC) MRI—The impact of SNR on ADC measurement

Purpose

To compare ADC values measured from diffusion-weighted MR (DW-MR) images of the prostate obtained with both endorectal and phased-array coils (ERC + PAC) to those from DW-MRI images obtained with an eight-channel torso phased-array coil (PAC) at 3.0 T.

Methods

The institutional review board issued a waiver of informed consent for this HIPAA-compliant study. Twenty-five patients with biopsy-proven prostate cancer underwent standard 3-T MRI using 2 different coil arrangements (ERC + PAC and PAC only) in the same session. DW-MRI at five b-values (0, 600, 1000, 1200, and 1500 s/mm²) were acquired using both coil arrangements. On b = 0 images, signal-to-noise ratios (SNRs) were measured as the ratio of the mean signal from PZ and TZ ROIs to the standard deviation from the mean signal in an artifact-free ROI in the rectum. Matching regions-of-interest (ROIs) were identified in the peripheral zone and transition zone on ERC-MRI and PAC-MRI. For each ROI, mean ADC values for all zero and non-zero b-value combinations were computed.

Results

Mean SNR with ERC-MRI at PZ (66.33 ± 27.07) and TZ (32.69 ± 12.52) was 9.27 and 5.52 times higher than with PAC-MRI ((7.32 ± 2.30) and (6.13 ± 1.56), respectively) (P < 0.0001 for both). ADCs from DW-MR images obtained with all b-values in the PZ and TZ were significantly lower with PAC-MRI than with ERC-MRI (P < 0.001 for all).

Conclusion

Lower SNR of DW-MR images of the prostate obtained with a PAC can significantly decrease ADC values at higher b-values compared to similar measurements obtained using the ERC. To address these requirements, clinical MR systems should have image processing capabilities which incorporate the noise distribution.     

Apparent diffusion coefficient of renal parenchyma and color Doppler ultrasound of intrarenal arteries in patients with cirrhosis related renal dysfunction

Objectives

The aim of this work was to study the renal hemodynamic changes which occur with liver cirrhosis using diffusion weighted magnetic resonance imaging (DW-MRI) and renal color duplex Doppler ultrasound.

Patients and methods

Patients were divided into four groups: Group A: 15 cirrhotic patients with compensated liver cirrhosis, Group B: 15 cirrhotic patients with refractory ascites, Group C: 15 cirrhotic patients with hepatorenal syndrome, Group D: 10 healthy persons as a control. The apparent diffusion coefficient (ADCs) of the kidneys was calculated using low b values (ADC_low) and high b values (ADC_high). Color Doppler ultrasound was performed in interlobar and arcuate arteries to calculate resistive index (RI) and pulsatility index (PI) in all patients.

Results

ADC_low showed a statistically significant difference between patients with hepatorenal syndrome and other groups. Using ADC_high no significant difference between different groups was noted. RI and PI of both interlobar and arcuate arteries were significantly higher in all the patient groups than the control group (P < 0.0001). RI and PI of both interlobar and arcuate arteries were significantly higher in patients with hepatorenal syndrome.

Conclusion

Liver cirrhosis, even in the presence of refractory ascites, did not affect the ADC value of renal parenchyma, however ADC value is affected in renal parenchyma of patients with hepato-renal syndrome. Duplex-Doppler ultrasound of intrarenal arteries enables the early detection of renal hemodynamic disturbances in patients with liver cirrhosis.     

Prediction of clinical outcome after stereotactic body radiotherapy for non-small cell lung cancer using diffusion-weighted MRI and F-FDG PET

Purpose/objectives

To evaluate the use of diffusion-weighted magnetic resonance imaging (DW-MRI) and ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) for predicting disease progression (DP) among patients with non-small cell lung carcinoma (NSCLC) treated with stereotactic body radiotherapy (SBRT).

Materials/methods

Fifteen patients with histologically confirmed stage I NSCLC who underwent pre-treatment DW-MRI and PET and were treated with SBRT were enrolled. The mean apparent diffusion coefficient (ADC) value and maximum standardised uptake value (SUV_max) were measured at the target lesion and evaluated for correlations with DP.

Results

The median pre-treatment ADC value was 1.04 × 10⁻³ (range 0.83–1.29 × 10⁻³) mm²/s, and the median pre-treatment SUV_max was 9.9 (range 1.6–30). There was no correlation between the ADC value and SUV_max. The group with the lower ADC value (≤1.05 × 10⁻³ mm²/s) and that with a higher SUV_max (≥7.9) tended to have poor DP, but neither trend was statistically significant (p = 0.09 and 0.32, respectively). The combination of the ADC value and SUV_max was a statistically significant predictor of DP (p = 0.036).

Conclusion

A low ADC value on pre-treatment DW-MRI and a high SUV_max may be associated with poor DP in NSCLC patients treated with SBRT. Using both values in combination was a better predictor.     

Diffusion weighted MRI and transient elastography assessment of liver fibrosis in hepatitis C patients: Validity of non invasive imaging techniques

Objective

Treatment for hepatitis C infection and monitoring of progression were based on degree of fibrosis, which were traditionally diagnosed by liver biopsy but it has many limitations. We aim to evaluate noninvasive imaging methods, so-called diffusion-weighted MRI (DW MRI) and transient elastography [(TE), fibroscan] in diagnosing liver fibrosis in hepatitis C (HCV) patients.

Patients

The Study included 102 hepatitis C patients (62 male) with mean age of 38 ± 5. For all patients liver biopsy was done followed by DW MRI and TE. METAVIR classification system was used for staging liver fibrosis. Data obtained were collected and results of DW MRI and TE were compared with those of histopathology. The diagnostic performance of ADC and TE was determined using areas under receiver operating characteristic (AUROC) curves for significant fibrosis ?F3.

Results

Measuring ADC at different b-values had a significant negative correlation with stage of fibrosis P = 0.001, the best negative correlation at b-value of 700 mm²/s. TE had a significant positive correlation with stage of fibrosis P = 0.005. Both examination showed a significant difference between fibrosis stage <F3 and stages ?F3 with P < 0.00 for ADC measure at each b-value and TE respectively.

Conclusion

This study suggests that DW MRI and TE had favorable comparable results with liver biopsy for the diagnosis of significant liver fibrosis.     

Diffusion-weighted imaging in the head and neck region: usefulness of apparent diffusion coefficient values for characterization of lesions

PURPOSE

We aimed to evaluate the role of apparent diffusion coefficient (ADC) values calculated from diffusion-weighted imaging for head and neck lesion characterization in daily routine, in comparison with histopathological results.

METHODS

Ninety consecutive patients who underwent magnetic resonance imaging (MRI) at a university hospital for diagnosis of neck lesions were included in this prospective study. Diffusion-weighted echo-planar MRI was performed on a 1.5 T unit with b factor of 0 and 1000 s/mm² and ADC maps were generated. ADC values were measured for benign and malignant whole lesions seen in daily practice.

RESULTS

The median ADC value of the malignant tumors and benign lesions were 0.72×10⁻³ mm²/s, (range, 0.39–1.51×10⁻³ mm²/s) and 1.17×10⁻³ mm²/s, (range, 0.52–2.38×10⁻³ mm²/s), respectively, with a significant difference between them (P < 0.001). A cutoff ADC value of 0.98×10⁻³ mm²/s was used to distinguish between benign and malignant lesions, yielding 85.3% sensitivity and 78.6% specificity. The median ADC value of lymphomas (0.44×10⁻³ mm²/s; range, 0.39–0.58×10⁻³ mm²/s) was significantly smaller (P < 0.001) than that of squamous cell carcinomas (median ADC value 0.72×10⁻³ mm²/s; range, 0.65–1.06×10⁻³ mm²/s). There was no significant difference between median ADC values of inflammatory (1.13×10⁻³ mm²/s; range, 0.85–2.38×10⁻³ mm²/s) and noninflammatory benign lesions (1.26×10⁻³ mm²/s; range, 0.52–2.33×10⁻³ mm²/s).

CONCLUSION

Diffusion-weighted imaging and the ADC values can be used to differentiate and characterize benign and malignant head and neck lesions.Diagnosis of head and neck lesions is difficult due to the complicated anatomic structure and different histological components of the many tissues that the neck contains. Imaging of head and neck lesions is not only important for diagnosis of lesions, but also for differentiation of benign lesions from malignant lesions and staging of tumors. While conventional imaging methods mainly evaluate morphological properties, their value is limited in recognizing prognostic characteristics such as benign-malignant differentiation of lesions (1). Routine magnetic resonance imaging (MRI) is a time-consuming method, which is sensitive to differences between examiners and may require the use of contrast material. With development of rapid MRI sequences (such as echo-planar [EPI], fast advanced spin echo [FASE], split echo acquisition of fast spin echo [SPLICE]), the sensitivity to susceptibility artifacts limiting the use of MRI for the head and neck region and limitations linked to duration have been significantly reduced (2, 3).Diffusion-weighted magnetic resonance imaging (DW-MRI) is a short sequence produced from EPI, FASE, SPLICE sequences. DW-MRI is sensitive to the randomized (Brownian) motion of water molecules at a microscopic level, which provides functional information about tissues. DW-MRI was initially used to diagnose early stroke in the brain and to evaluate brain masses (4–6). Previous studies have shown that rapid growth of high-grade tumors like astrocytoma and lymphoma causes hypercellularity, which leads to limitation of the diffusion of water molecules. Nowadays, apparent diffusion coefficient (ADC) maps calculated from DW-MRI sequences are being increasingly used to provide quantitative data for head and neck lesion diagnosis. In malignant lesions, the DW-MRI signal increases and signal loss is observed on ADC maps (5, 7, 8). Many researchers benefited from this feature of DW-MRI and evaluated the effectiveness of DW-MRI for head and neck lesion identification, benign-malignant differentiation, and characterization of malignant lesions (9–11).In this prospective study, head and neck lesions that are seen in daily routine were evaluated using DW-MRI, and the role of ADC values in lesion characterization was investigated with the guidance of histopathological results.     

Impact of size of region-of-interest on differentiation of renal cell carcinoma and renal cysts on multi-phase CT: Preliminary findings

Introduction

To assess impact of size of regions-of-interest (ROI) on differentiation of RCC and renal cysts using multi-phase CT, with focus on differentiating papillary RCC (pRCC) and cysts given known hypovascularity of pRCC.

Methods

99 renal lesions (23 pRCC, 47 clear-cell RCC, 7 chromophobe RCC, 22 cysts) underwent multi-phase CT. Subjective presence of visual enhancement was recorded for each lesion. Whole-lesion (WL) ROIs, and small (≤5 mm²), medium (average size of small and large ROIs), and large (half of lesion diameter) peripherally located partial-lesion (PL) ROIs, were placed on non-contrast and nephrographic phases. Impact of ROI size in separating cysts from all RCC and from pRCC based on increased attenuation between phases was assessed using ROC analysis.

Results

Visual enhancement was perceived in 96% of ccRCC, 61% of pRCC, and 9% of cysts. AUCs for separating all RCC and cysts for WL-ROI and small, medium, and large PL-ROIs were 91%, 96%, 91% and 93%, and among lesions without visible enhancement were 60%, 79%, 67% and 67%. AUCs for separating pRCC and cysts for WL-ROI and small, medium, and large PL-ROIs were 78%, 92%, 82% and 84%, and among lesions without visible enhancement were 64%, 88%, 69% and 69%.

Conclusion

Small PL-ROIs had higher accuracy than WL-ROI or other PL-ROIs in separating RCC from cysts, with greater impact in differentiating pRCC from cysts and differentiating lesions without visible enhancement. Thus, when evaluating renal lesions using multi-phase CT, we suggest placing small peripheral ROIs for highest accuracy in distinguishing renal malignancy and benign cysts.     

Efficiency of apparent diffusion coefficients in differentiation of colorectal tumor recurrences and posttherapeutical soft-tissue changes

Objective

To evaluate effectiveness of apparent diffusion coefficient (ADC) values measured by diffusion-weighted magnetic resonance imaging (DW-MRI) in differentiation of colorectal tumor recurrences and posttherapeutical soft tissue changes.

Methods

For this prospective study, 30 patients (22 males, 8 females; age range 30–81 years; mean age 61 ± 12 years) who underwent surgery for colorectal tumors and had a mass detected by computed tomography (CT) and/or MRI during follow-up examinations were divided into 2 groups [17 patients (Group 1) with recurrence and 13 patients (Group 2) with benign fibrosis/granulation tissue]. Final diagnoses were based on histopathological examination in 14 patients and clinical follow-up at least 6 months in the remaining 16. In the latter, the diagnosis of recurrence was made in cases in which the lesion was larger on follow-up CT and MRI; recurrence was ruled out in cases of stable or shrinking lesions without any increase in tumor markers. DW-MRI was performed in the axial plane, for two different b values (b = 0 and 800 s/mm²).The mean apparent diffusion coefficient (ADC) values were measured by manual delineation of regions of interest on ADC maps.

Results

The median ADC values were 1.07 × 10⁻³ mm/s² (min: 0.82, max: 2.05) and 1.91 × 10⁻³ mm/s² (min: 1.51, max: 2.22) in Groups 1 and 2, respectively. A statistically significant difference was detected between the two groups (P < 0.001). When the threshold value used to determine whether the lesions recurred was 1.48 × 10⁻³ mm/s² based on ROC analysis, the sensitivity was 82% and the specificity was 100%. There were three patients with a false-negative diagnosis, and the primary histopathological diagnosis of all was mucinous adenocarcinoma.

Conclusions

Because recurrences in mucinous adenocarcinomas have high ADC values, they may show overlap with benign lesions. In the detection of the local recurrence of colorectal neoplasms, with the exception of mucinous adenocarcinomas, ADC measurements are reliable imaging techniques.     

Impact of thrombocytopenia on radiofrequency ablation therapy of hepatocellular carcinoma in patients with liver cirrhosis

Objective

The objective of our study was to assess the impact of thrombocytopenia on percutaneous radiofrequency ablation (RFA) therapy of Hepatocellular carcinoma (HCC) in patients with liver cirrhosis.

Material and methods

We analyzed retrospectively 64 patients with liver cirrhosis and thrombocytopenia, defined as a platelet count of less than 100 × 10³/mm³ that had undergone percutaneous RFA to treat 86 HCCs. The Kaplan–Meier and Cox regression methods were used to predict hemorrhage, and time to the first decompensation event, defined as the development of ascites, hepatic encephalopathy, variceal hemorrhage, and deterioration of liver function to Child-Pugh class B/C.

Results

There were no significant risk factors of hemorrhage. Univariate and multivariate analyses revealed that liver decompensation was clearly linked to prothrombin activity (p = 0.010 and p = 0.006, respectively) and a ? 63% of prothrombin activity was found as significant threshold for the occurrence of liver decompensation (p = 0.003) confirmed by the Cox model (p = 0.05).

Conclusion

Percutaneous RFA for HCC can be performed safely without the need for support, in patients with liver cirrhosis and thrombocytopenia up to 37 × 10³/mm³.