Imaging features of intrahepatic cholangiocarcinoma in Gd-EOB-DTPA-enhanced MRI

Objective

The aim of this study is to describe the imaging features of intrahepatic cholangiocarcinoma in Gd-EOB-DTPA-enhanced MRI and to determine whether it results in improved tumour conspicuity of cholangiocarcinoma.

Materials and methods

Fifty-four patients with histologically proven intrahepatic cholangiocarcinoma underwent MRI of the liver using a 1.5 T MR-scanner with Gadoxetic acid disodium (Gd-EOB-DTPA; Eovist/Primovist, Bayer Healthcare, Berlin, Germany). The standard imaging protocol included a T2w multi-shot TSE sequence with fat saturation (fs), a T2w single shot sequence without fs and a T1w 3D GRE sequences with fs (unenhanced and arterial, portovenous, late venous and hepatobiliary phase). Two board certified radiologists experienced in liver MRI (5 and 10 years experience) evaluated retrospectively all MRI scans qualitatively and quantitatively. Signal was measured with region-of-interests (ROI) and signal-to-noise (SNR) as well as contrast-to-noise (CNR) was calculated. Statistical significance was tested with an ANOVA and a pairwise Wilcoxon rank test.

Results

All intrahepatic cholangiocarcinomas presented as hypointense lesions in the late venous and hepatobiliary phase. Images in the hepatobiliary phase showed the highest lesion conspicuity, i.e. n = 9 blurred (16.6%), n = 31 moderate (57.4%) and n = 14 sharp (26%). This was significantly higher than the lesion conspicuity of all other sequences or phases. Furthermore, the CNR was the highest in this sequence with 76.8 ± 51.3, with significantly higher values than the CNR of the unenhanced T1w sequence (CNR: 35.6 ± 21.0; p < 0.0001) and the arterial phase images (CNR: 53.6 ± 36.8; p < 0.001). The hepatobiliary phase images showed a SNR of 97.3 ± 59.7 (p < 0.001) and thus was significantly different from the unenhanced T1w sequence (SNR: 60.4 ± 35.3; p < 0.001), whereas the increase in SNR from the late venous to hepatobiliary phase was neglectable, indicating that no liver-specific contrast uptake is present in cholangiocarcinoma.

Conclusion

Intrahepatic cholangiocarcinoma presents as a hypointense lesion in Gd-EOB-DTPA-enhanced MRI in late venous phase images. The lesion conspicuity as well as CNR was highest in the hepatobiliary phase. Consequently, hepatobiliary phase images in Gd-EOB-DTPA-enhanced MRI images might be helpful for therapy planning due to the exact depiction of the tumour borders.     

90°-Flip-angle three-dimensional double-echo steady-state (3D-DESS) magnetic resonance imaging of the knee: Isovoxel cartilage imaging at 3 T

Purpose

The purpose of this study was to investigate whether 3D-double echo steady state (3D-DESS) with improved contrast by setting the FA (Flip angle) at 90° is useful in 3D isotropic cartilage imaging of the knee at 3 T.

Materials and methods

Imaging was performed in 10 healthy volunteers using 3 methods: with 3D-DESS using FA of 25° and 90°, and with true fast imaging with steady-state precession (True-FISP). The signal-to-noise ratio (SNR) of the synovial fluid and cartilage, and contrast-to-noise ratio (CNR) were measured, and mean values were compared. Visual assessment of artifacts was performed with the cartilage divided into 6 regions.

Results

There were no significant differences in synovial fluid SNR in the comparison between FA-90° 3D-DESS and True-FISP (P = 0.364). A significantly higher cartilage SNR was observed with FA-90° 3D-DESS than with True-FISP (P = 0.031). There were no significant differences in synovial fluid-cartilage CNR between FA-90° 3D-DESS and True-FISP (P = 0.892). In the evaluation of artifacts, FA-90° 3D-DESS imaging showed a significantly higher score than True-FISP imaging in the patella and trochlea cartilage (P < 0.001, P < 0.002).

Conclusions

FA-90° 3D-DESS is useful in 3D isotropic cartilage imaging of the knee at 3 T.     

T2-weighted MR imaging of the liver: Qualitative and quantitative comparison of SPACE MR imaging with turbo spin-echo MR imaging

Objective

To qualitatively and quantitatively compare T2-weighted MR imaging of the liver using volumetric spin-echo with sampling perfection with application-optimized contrast using different flip angle evolutions (SPACE) with conventional turbo spin-echo (TSE) sequence for fat-suppressed T2-weighted MR imaging of the liver.

Materials and methods

Thirty-three patients with suspected focal liver lesions had SPACE MR imaging and conventional fat-suppressed TSE MR imaging. Images were analyzed quantitatively by measuring the lesion-to-liver contrast-to-noise ratio (CNR), and the signal-to-noise ratio (SNR) of main focal hepatic lesions, hepatic and splenic parenchyma and qualitatively by evaluating the presence of vascular, respiratory motion and cardiac artifacts. Wilcoxon signed rank test was used to search for differences between the two sequences.

Results

SPACE MR imaging showed significantly greater CNR for focal liver lesions (median = 22.82) than TSE MR imaging (median = 14.15) (P < .001). No differences were found for SNR of hepatic parenchyma (P = .097), main focal hepatic lesions (P = .35), and splenic parenchyma (P = .25). SPACE sequence showed less artifacts than TSE sequence (vascular, P < .001; respiratory motion, P < .001; cardiac, P < .001) but needed a longer acquisition time (228.4 vs. 162.1 s; P < .001).

Conclusion

SPACE MR imaging provides a significantly increased CNR for focal liver lesions and less artifacts by comparison with the conventional TSE sequence. These results should stimulate further clinical studies with a surgical standard of reference to compare the two techniques in terms of sensitivity for malignant lesions.     

Bile duct evaluation of potential living liver donors with Gd-EOB-DTPA enhanced MR cholangiography: Single-dose,double dose or half-dose contrast enhanced imaging

Introduction

Detailed knowledge of the biliary anatomy is essential to avoid complications in living donor liver transplantation. The aim of this study was to determine the optimal dosage of Gd-EOB-DTPA for contrast-enhanced magnetic resonance cholangiography (ce-MRC) with reference to contrast-enhanced CT cholangiography (ce-CTC).

Materials and methods

30 potential living liver donors (PLLD) underwent both ce-CTC and ce-MRC. Ten candidates each received single, double or half-dose Gd-EOB-DTPA. Ce-MRC images with and without inversion recovery pulses (T1w ± IR) were acquired 20–30 min after intravenous contrast injection. Image data was quantitatively and qualitatively reviewed by two radiologists based on a on a 5-point scale. Data sets were compared using a Mann–Whitney-U-test or Wilcoxon-rank-sum-test. Kappa values were also calculated.

Results

All image series provided sufficient diagnostic information both showing normal biliary anatomy and variant bile ducts. Ce-CTC showed statistically significant better results compared to all ce-MRC data sets. T1w MRC with single dose Gd-EOB-DTPA proved to be superior to half and double dose in subjective and objective evaluation without a statistically significant difference.

Conclusions

Ce-MRC is at any dosage inferior to ce-CTC. As far as preoperative planning of bile duct surgery is focused on the central biliary anatomy, ce-MRC can replace harmful ce-CTC strategies, anyway. Best results were seen with single dose GD-EOB-DTPA on T1w MRC+IR.     

Hepatic hemangiomas: difference in enhancement pattern on 3T MR imaging with gadobenate dimeglumine versus gadoxetate disodium

Purpose

To compare intraindividual differences in enhancement pattern of hepatic hemangiomas between gadobenate dimeglumine (Gd-BOPTA) and gadoxetate disodium (Gd-EOB-DTPA)-enhanced 3T MR imaging.

Materials and methods

This is a HIPAA-compliant, IRB-approved retrospective study with waiver for informed consent granted. From 10/07 to 5/09, 10 patients (2 males, 8 females; mean age, 57.3 years) with 15 hepatic hemangiomas (mean diameter, 4.4 ± 5.6 cm) underwent both Gd-BOPTA- and Gd-EOB-DTPA-enhanced 3T MR imaging (mean interval, 266 days; range, 38–462 days). Diagnosis of hemangioma was based on strict imaging criteria. MR imaging was obtained during three arterial, portal venous, and up to four delayed phases. During each phase, hemangioma-to-liver contrast-to-noise ratio (CNR) was measured for each lesion on both examinations. Statistical analysis was performed using paired Student's t-test.

Results

Hemangioma-to-liver CNR peaked during the portal venous phase (Gd-BOPTA: 48.9 ± 65.8, Gd-EOB-DTPA: 0.7 ± 3.8). During all imaging phases except the first arterial phase, hemangioma-to-liver CNR was significantly lower on Gd-EOB-DTPA-enhanced compared to Gd-BOPTA-enhanced MR images (p < 0.05). Notably, Gd-EOB-DTPA yielded negative hemangioma-to-liver CNR (−2.5 ± 2.4) compared to Gd-BOPTA (40.7 ± 56.4) during the first delayed phase (7–8 min after contrast administration), remaining negative for the rest of the delayed phases (up to 26 min after contrast administration).

Conclusion

The enhancement patterns of hepatic hemangiomas differs significantly between Gd-BOPTA and Gd-EOB-DTPA-enhanced 3T MR imaging. The smaller dose, shorter plasma half-life, and increased hepatobiliary uptake of Gd-EOB-DTPA leads to a negative CNR of hemangioma-to-liver on delayed phases and could create an imaging pitfall with this agent.     

Optimization of keV-settings in abdominal and lower extremity dual-source dual-energy CT angiography determined with virtual monoenergetic imaging

Objectives

To compare objective image quality indices in dual-energy CT angiography (DE-CTA) studies of the abdomen and lower extremity using conventional polyenergetic images (PEIs) and virtual monoenergetic images (MEIs) at different kiloelectron volt (keV) levels.

Methods

We retrospectively evaluated 68 dual-source DE-CTA studies. 50 patients (42 men, 71 ± 10 years) underwent abdominal DE-CTA. 18 patients (13 men, 67 ± 10 years) underwent lower extremity DE-CTA. MEIs from 40 to 120 keV were reconstructed. Signal intensity, noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were assessed in infrarenal aorta, superior mesenteric, external iliac, femoral, popliteal, and lower leg arteries. Comparisons between MEIs and PEIs were performed with Dunnett's test.

Results

222 arteries were evaluated. In abdominal arteries 70 keV MEIs showed statistically equal signal intensity, noise and CNR levels (+13%; +31%, −14% on average; all p > 0.05) compared to PEIs; SNR was equal or slightly impaired (−7% on average; p < 0.001–1.00). In lower extremity arteries 60 keV MEIs resulted in significantly higher signal intensity and CNR (+54%; +54% on average; all p < 0.05) compared to PEIs at equal noise levels (+18% on average; all p > 0.05) and equal or higher SNR (+49% on average; p < 0.01–0.35).

Conclusions

Low-keV MEIs lead to equal or higher signal intensity and CNR compared to PEIs. In lower extremity DE-CTA, additional reconstruction of low-keV MEIs at 60 keV might increase diagnostic confidence.     

Diffusion weighted imaging of liver lesions suspect for metastases: Apparent diffusion coefficient (ADC) values and lesion contrast are independent from Gd-EOB-DTPA administration

Purpose

Gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) enhanced liver MRI is widely used for detection and differentiation of focal liver lesions. Diffusion weighted imaging (DWI) including apparent diffusion coefficient (ADC) measurements is increasingly utilised as a fast and, with limitations, quantitative method for liver lesion detection and characterisation. Herein we investigate whether the administration of Gd-EOB-DTPA affects DWI.

Materials and methods

31 consecutive patients referred to standardised liver MRI (1.5 T, Gd-EOB-DTPA, 0.025 mmol/kg) were retrospectively reviewed. All underwent a breathhold DWI sequence before and after contrast agent administration (EPI-DWI, TR/TE (effective): 2100/62 ms, b-values: 0 and 800 s/mm²). Patients with previously treated liver lesions were excluded. Signal intensity of lesion, parenchyma and noise on DWI images as well as the ADC value were measured after identification by two observers in consensus using manually placed regions of interest. The reference standard was imaging follow-up determined separately by two radiologists. Data analysis included signal-to-noise (SNR) ratio and contrast-to-noise ratio (CNR) calculations, comparisons were drawn by employing multiple Bonferroni corrected Wilcoxon signed-rank tests.

Results

50 malignant and 39 benign lesions were identified. Neither SNR, CNR nor ADC values showed significant differences between pre- and postcontrast DWI. Both pre- and postcontrast ADC values differed significantly between benign and malignant lesions (P < 0.001).

Conclusion

We did not identify a significant influence of Gd-EOB-DTPA on DWI of liver lesions. This allows for individual tailoring of imaging protocols according to clinical needs.     

Value of monoenergetic low-kV dual energy CT datasets for improved image quality of CT pulmonary angiography

Purpose

High vessel attenuation and high contrast-to-noise ratio (CNR) are prerequisites for high diagnostic confidence in CT pulmonary angiography (CTPA). This study evaluated the impact of calculated monoenergetic dual-energy (DE) CTPA datasets on vessel attenuation and CNR.

Materials and methods

50 Patients (24 men, mean age 68 ± 14 years) who underwent DE-CTPA were retrospectively included in this study. The 80 and 140-kV DE polyenergetic image data were used to calculate virtual monoenergetic image datasets in 10 kiloelectron volt (keV) increments from 40 to 120 keV. Vessel and soft tissue attenuation and image noise were measured in various regions of interest and the CNR was subsequently calculated. Differences in vessel attenuation and CNR were compared between the different monoenergetic datasets. The best monoenergetic dataset was then compared to the standard 120-kV polyenergetic dataset.

Results

Vessel attenuation and CNR of 70-keV CTPA datasets were superior to all other monoenergetic image datasets (all p < 0.05). 70-keV monoenergetic datasets provided a statistically significant 12% increase in mean vessel attenuation compared to standard 120-kV polyenergetic datasets (384 ± 117 HU vs. 342 ± 106 HU, respectively; p < 0.0001) and a statistically significant 18% increase in mean CNR (29 ± 13 vs. 24± 11 respectively; p < 0.0001).

Conclusion

Virtual 70-keV monoenergetic CTPA image datasets significantly increase vessel attenuation and CNR of DE-CTPA studies, suggesting that clinical application of low-keV monoenergetic reconstructions may allow a decrease in the amount of iodinated contrast required for adequate image quality in DE-CTPA examinations.     

Dark blood versus bright blood T2* acquisition in cardiovascular magnetic resonance (CMR) for thalassaemia major (TM) patients: Evaluation of feasibility,reproducibility and image quality

Objectives

To compare the effectiveness of dark blood (DB) versus bright blood (BB) sequences. To assess the intra and inter-observer variability and inter-study reproducibility between BB versus DB. To evaluate image quality level in the two sequences.

Methods

In a setting of 138 patients we performed CMR using cardiac gated Gradient-multiecho single breath-hold BB and DB sequences in the middle ventricular septum.Each acquisition was repeated during the same exam. Truncation method was used to account for background noise. Image quality (IQ) was assessed using a 5 point grading scale and image analysis was conducted by 2 experienced observers.

Results

Compared with the conventional BB acquisition, the coefficient of correlation and significance of the DB technique was superior for intra-observer reproducibility (p < 0.001), inter-observer reproducibility (p < 0.001) and inter-study reproducibility (p < 0.001). The variability is also lower for DB sequences for T2* values <14 ms. Assessment of artifacts showed a superior score for DB versus BB scans (4 versus 3, p < 0.001).

Conclusions

Improvement in terms of inter observer and inter study variability using DB sequences was obtained. The greatest disparity between them was seen in inter-study reproducibility and higher IQ in DB was seen.Study demonstrates better performance of DB imaging compared to BB in presence of comparable effectiveness.     

Detection of active bile leak with Gd-EOB-DTPA enhanced MR cholangiography: Comparison of 20–25 min delayed and 60–180 min delayed images

Objectives

The purpose of this study was to assess the value of contrast-enhanced magnetic resonance cholangiography (MRC) performed in different time delays after injection of gadoxetic acid disodium (Gd-EOB-DTPA) for the diagnosis of active bile leak.

Methods

This retrospective analysis included Gd-EOB-DTPA enhanced MR images of 34 patients suspected of bile leak. Images were acquired 20–25 min after Gd-EOB-DTPA injection. If there was inadequate contrast in the bile ducts then delayed images after 60–90 min and 150–180 min were obtained. Results were correlated with intraoperative findings, ERCP results, clinical data, laboratory tests, and follow-up examinations.

Results

Gd-EOB-DTPA enhanced MRC yielded an overall sensitivity of 96.4%, specificity of 100% and accuracy of 97.1% for the diagnosis of an active bile leak. The sensitivity of 20–25 min delayed MR images was 42.9%, of combined 20–25 min and 60–90 min delayed images was 92.9% and of combined 20–25 min, 60–90 min and 150–180 min delayed images was 96.4%.

Conclusions

Gd-EOB-DTPA enhanced MRC utilizing delayed phase images was effective for detecting the presence and location of active bile leaks. The images acquired 60–180 min post-injection enabled identification of bile leaks even in patients with a dilated biliary system or moderate liver dysfunction.     

MRI for characterization of primary tumors in the non-cirrhotic liver: Added value of Gd-EOB-DTPA enhanced hepatospecific phase

Purpose

To evaluate the added value of hepatospecific phase in Gd-EOB-DTPA enhanced magnetic resonance imaging (MRI) in patients with primary tumors in non-cirrhotic liver.

Methods

Twenty-nine patients (median, 39 years; range, 18–81 years; 11 male) underwent preoperative Gd-EOB-DTPA enhanced MRI including hepatospecific phase after 10 and 20 min of contrast injection at four institutions in Europe, North America and New Zealand. Images were evaluated by three different readers (R1–R3) who characterized liver tumors with and without consultation of the hepatospecific phase images. Confidence in diagnosis was scored on a visual analog scale from 1 to 10. Histopathology (adenoma, n = 5; focal nodular hyperplasia, n = 11 and hepatocellular carcinoma, n = 13) in all patients served as the standard of reference. Differences were evaluated using the McNemar and Wilcoxon signed rank test.

Results

Without hepatospecific phase images available, 22 (76%), 19 (66%) and 19 (66%) of 29 tumors were characterized correctly by the three readers respectively. Mean confidence in diagnosis was 6.1, 5.7 and 5.8. With the hepatospecific phase included, characterization of liver tumors did not change significantly with 21 (72%), 23 (79%) and 19 (66%) of 29 tumors diagnosed correctly (p > 0.05). According confidence ratings increased to 6.3, 6.5 and 7.7, respectively. Increase in diagnostic confidence was significant for R2 and R3 (p < 0.05) and independent of reader's experience.

Conclusion

The additional hepatospecific phase in Gd-EOB-DTPA enhanced MRI did not significantly increase diagnostic accuracy in characterization of primary tumors in the non-cirrhotic liver. However, 2/3 readers showed a significant increase in diagnostic confidence after consultation of the hepatospecific phase.     

Comparison of monopolar and bipolar diffusion weighted imaging sequences for detection of small hepatic metastases

Objective

To compare monopolar (MP) and bipolar (BP) diffusion weighted imaging (DWI) in detecting small liver metastases.

Materials and methods

Eighty-eight patients underwent 3-T MRI. The signal-to-noise ratios (SNR) of the liver parenchyma and lesions, the lesion-to-liver contrast-to-noise ratios (CNR), and the detection sensitivities were compared. The lesion distortion was scored (LDS) from 4 (no distortion) to 1 (excessive distortion), dichotomised as no-distortion and distortion, and the association between detected lesions for each reader in the MP or BP DWI group and the dichotomised lesion distortion degree was assessed.

Result

Forty-six hepatic metastases were confirmed. The CNR with BP images showed significantly higher values than with MP (P = 0.017). The detection sensitivities of the three readers were higher in the BP sequence than in MP, and one reader detected significantly more hepatic lesions with BP images (P = 0.04). LDS was significantly improved with BP sequence (P = 0.002). In the no-distortion group, excluding the MP DWI assessments of one reader, detection sensitivities were significantly higher than in the distortion group (P < 0.001 and P = 0.002, respectively).

Conclusion

Reduced lesion distortion improves the detection of small liver metastases, and BP is more sensitive in detecting small liver metastases than MP DWI.     

Effect of saline flush on enhancement of proximal and distal segments using 320-row coronary CT angiography

Objective

To investigate the effect of saline flush on coronary CT angiography of proximal, middle, and distal coronary artery segments, using 320-row CT, and to compare two injection duration protocols as to amount of contrast in the right heart chambers.

Methods

This retrospective study was approved by the local ethics committee, and the requirement for informed consent to participate in this study was waived. The final study group included 108 patients who underwent coronary CT angiography. The first 36 patients received contrast medium without saline flush (group 1); the next 36 patients received contrast medium for 14 s and saline flush (group 2); the last 36 patients received contrast medium for 12 s and saline flush (group 3). The CT number, noise, contrast-to-noise ratio (CNR), and number of segments with a CT number greater than 325 Hounsfield units (HU) were recorded for proximal, middle, and distal segments.

Results

The CT numbers and the CNR in groups 2 and 3 were significantly higher than that in group 1 (p < 0.005); the difference between groups 2 and 3 was not significant. The proportion of segments greater than 325 HU improved with saline flush (p < 0.05), with a larger improvement in the distal segments.

Conclusions

Saline flush improves enhancement and CNR of coronary arteries, particularly of distal segments, in coronary CT angiography using 320-row CT. An average contrast medium injection of 44 mL was feasible using a saline flush.     

New proposal for the staging of nonalcoholic steatohepatitis: Evaluation of liver fibrosis on Gd-EOB-DTPA-enhanced MRI

Purpose

We investigated whether the gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced MRI was useful for nonalcoholic steatohepatitis (NASH) staging based on the severity of liver fibrosis.

Materials and methods

Twenty-one male Sprague-Dawley rats aged 7 weeks, weighing about 150 g in NASH group were fed a choline-deficient diet for 4, 7 or 10 weeks, and seven rats in the control group were fed a standard diet (n = 7). After the feeding period, the rats were subjected to contrast-enhanced MRI (2D-FLASH; TR/TE = 101/2.9 ms, flip angle 90°). Gd-DTPA (0.1 mmol Gd/kg) and Gd-EOB-DTPA (0.025 mmol Gd/kg) were injected at 24-h intervals, and the speed of contrast injection was 1 mL/s. Signal intensities of the liver were measured and the relative enhancement (RE), the time of maximum RE (T_max) and elimination half-life of RE (T_1/2) in the liver were compared. The fibrosis rate (%) was calculated with the following formula: fibrosis/whole area × 100.

Results

The fibrosis rates of each group were as follows: 0.52, 0.79, 2.84, and 0.50% (4, 7, 10 weeks and control groups). The fibrosis rate of the 10 weeks group was significantly higher than the control and 4 or 7 weeks groups. Although there was no difference between the T_max and T_1/2 of each group after Gd-DTPA injection, the T_max and T_1/2 of the 10 weeks group were significantly prolonged in comparison with the control and 4 or 7 weeks groups after Gd-EOB-DTPA injection (p < 0.01). There was a significant correlation between the fibrosis rate and T_max or T_1/2 after Gd-EOB-DTPA injection (r = 0.90 or 0.97).

Conclusion

It was possible to assess the progress of liver fibrosis in NASH by evaluating the signal intensity-time course on Gd-EOB-DTPA-enhanced MRI.     

Optimal gadolinium concentration for direct MR arthrography at high field strength up to 7 T: In vitro model

Objective

Prospective evaluation of optimal MR arthrographic concentration of two gadolinium-based agents of different relaxivities, either in saline or iodinated carriers at 1.5, 3 and 7 T field strengths was evaluated in vitro.

Materials and methods

At 1.5, 3.0 and 7.0 T, gadobenate and gadoteridol were studied at different concentrations in both normal saline and iodinated contrast. IRT1W and multi-echo T2FSE sequences were obtained. Signal–concentration relationship of both used agents in different carriers and field strengths was plotted from their collected T1 and T2 values, as well as their derived longitudinal (r1) and transverse (r2) relaxivities.

Results

Significant increase in T1 signal intensity (p < 0.001) of both gadobenate and gadoteridol was observed in higher fields of 3 T and 7 T, stronger for gadoteridol. Contrarily, gadoteridol showed a significantly lesser decrease (p < 0.0001) of T2 signal intensity with increasing field from 3 T to 7 T.Iodinated carriers significantly diminished T2 signal intensity (p < 0.0001) except for highest concentration (10 mmol/L) (p = 0.8899) while this was only significant (p = 0.0279) between extreme concentrations for T1 signal.

Conclusion

On transitioning to high-field (3 T and 7 T) MR arthrography, keeping the least amount of iodine for intra-articular contrast delivery, and when choice is available, gadoteridol is preferable to gadobenate. However, gadobenate was still optimal at 3 T.     

Paradoxical signal pattern of mediastinal cysts on T2-weighted MR imaging: phantom and clinical study

Purpose

To evaluate the intracystic MRI (magnetic resonance imaging) signal intensity of mediastinal cystic masses on T2-weighted images.

Materials and methods

A phantom study was performed to evaluate the signal intensity of a mediastinal cystic mass phantom (rubber balloon containing water) adjacent to a cardiac phantom pulsing at the rate of 60/min. T2-weighted images (sequence, fast spin echo [FSE] and single shot fast spin echo [SSFSE]) were acquired for the mediastinal cystic mass phantom. Further, a clinical study was performed in 33 patients (16 men, 17 women; age range, 19-85 years; mean, 65years) with thymic cysts or pericardial cysts. In all patients, T2-weighted images (FSE and SSFSE) were acquired. The signal intensity of cystic lesion was evaluated and was compared with that of muscle. A region of interest (ROI) was positioned on the standard MR console, and signal intensity of the cystic mass (cSI), that of the muscle (mSI), and the rate of absolute value of cSI–mSI to standard deviation (SD) of background noise (|cSI–mSI|/SD = CNR [contrast-to-noise ratio]) were measured.

Results

The phantom study demonstrated that the rate phantom-ROI/saline-ROI was higher in SSFSE (0.36) than in FSE (0.19). In clinical cases, the degree of the signal intensity was higher in SSFSE than in FSE. The CNR was significantly higher in SSFSE (mean ± standard deviation, 111.0 ± 47.6) than in FSE (72.8 ± 36.6) (p < 0.001, Wilcoxon signed-rank test).

Conclusions

Anterior mediastinal cysts often show lower signal intensity than the original signal intensity of water on T2-weighted images. SSFSE sequence reduces this paradoxical signal pattern on T2-weighted images, which may otherwise cause misinterpretation when assessing cystic lesions.     

Coronary CT angiography: Comparison of a novel iterative reconstruction with filtered back projection for reconstruction of low-dose CT—Initial experience

Objective

To prospectively compare subjective and objective image quality in 20% tube current coronary CT angiography (cCTA) datasets between an iterative reconstruction algorithm (SAFIRE) and traditional filtered back projection (FBP).

Materials and methods

Twenty patients underwent a prospectively ECG-triggered dual-step cCTA protocol using 2nd generation dual-source CT (DSCT). CT raw data was reconstructed using standard FBP at full-dose (Group_1a) and 80% tube current reduced low-dose (Group_1b). The low-dose raw data was additionally reconstructed using iterative raw data reconstruction (Group_2). Attenuation and image noise were measured in three regions of interest and signal-to-noise-ratio (SNR) as well as contrast-to-noise-ratio (CNR) was calculated. Subjective diagnostic image quality was evaluated using a 4-point Likert scale.

Results

Mean image noise of group_2 was lowered by 22% on average when compared to group_1b (p < 0.0001–0.0033), while there were no significant differences in mean attenuation within the same anatomical regions. The lower image noise resulted in significantly higher SNR and CNR ratios in group_2 compared to group_1b (p < 0.0001–0.0232). Subjective image quality of group_2 (1.88 ± 0.63) was also rated significantly higher when compared to group_1b (1.58 ± 0.63, p = 0.004).

Conclusions

Image quality of 80% tube current reduced iteratively reconstructed cCTA raw data is significantly improved when compared to standard FBP and consequently may improve the diagnostic accuracy of cCTA.     

Detection and classification of different liver lesions: Comparison of Gd-EOB-DTPA-enhanced MRI versus multiphasic spiral CT in a clinical single centre investigation

Objective

To compare the diagnostic efficacy of Gd-EOB-DTPA-enhanced magnetic resonance imaging (MRI) vs. multidetector computed tomography (MDCT) for the detection and classification of focal liver lesions, differentiated also for lesion entity and size; a separate analysis of pre- and postcontrast images as well as T2-weighted MRI sequences of focal and exclusively solid lesions was integrated.

Methods

Twenty-nine patients with 130 focal liver lesions underwent MDCT (64-detector-row; contrast medium iopromide; native, arterial, portalvenous, venous phase) and MRI (1.5-T; dynamic and tissue-specific phase 20 min after application of Gd-EOB-DTPA). Hepatic lesions were verified against a standard of reference (SOR). CT and MR images were independently analysed by four blinded radiologists on an ordinal 6-point-scale, determining lesion classification and diagnostic confidence.

Results

Among 130 lesions, 68 were classified as malignant and 62 as benign by SOR. The detection of malignant and benign lesions differed significantly between combined and postcontrast MRI vs. MDCT; overall detection rate was 91.5% for combined MRI and 80.4% for combined MDCT (p < 0.05). Considering all four readers together, combined MDCT achieved sensitivity of 66.2%, specificity of 79.0%, and diagnostic accuracy of 72.3%; combined MRI reached superior diagnostic efficacy: sensitivity 86.8%, specificity 94.4%, accuracy 90.4% (p < 0.05). Differentiated for lesion size, in particular lesions <20 mm revealed diagnostic benefit by MRI. Postcontrast MRI also achieved higher overall sensitivity, specificity, and accuracy compared to postcontrast MDCT for focal and exclusively solid liver lesions (p < 0.05).

Conclusion

Combined and postcontrast Gd-EOB-DTPA-enhanced MRI provided significantly higher overall detection rate and diagnostic accuracy, including low inter-observer variability, compared to MDCT in a single centre study.     

Validity of gradient-echo three-dimensional delayed gadolinium-enhanced magnetic resonance imaging of hip joint cartilage: A histologically controlled study

Objective

To validate gradient-echo three-dimensional (3D) delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) by means of histological analyses in the assessment of hip joint cartilage.

Materials and methods

Twenty-one femoral head specimens collected from 21 patients (7 males, 14 females, mean age: 60.9 ± 9.6 years; range: 37.6–77.3 years), who underwent total hip replacement for symptomatic hip joint osteoarthritis, underwent MRI and histological assessment. A region of 2 cm² at the weight-bearing area was marked with four pins to enable multi-planar MRI reformatting to be matched with histological sections. MRI was performed at 3 T with a 3D double-echo steady-state (DESS) sequence for morphological cartilage assessment and 3D Volumetric Interpolated Breathhold Examination (VIBE) for T1_Gd mapping. Histological sections were evaluated according to the Mankin score system. Total Mankin score, grade of toluidine staining (sensitive for glycosaminoglycan content) and a modified Mankin score classification system with four sub-groups of cartilage damage were correlated with MRI data.

Results

Spearman's rho correlation analyses revealed a statistically significant correlation between T1_Gd mapping and histological analyses in all categories including total Mankin score (r = −0.658, p-value ≤ 0.001), toluidine staining (r = −0.802, p-value < 0.001) and modified Mankin score (r = −0.716, p-value < 0.001). The correlation between morphological MRI and histological cartilage assessment was statistically significant but inferior to the biochemical cartilage MRI (r-values ranging from −0.411 to 0.525, p-values < 0.001).

Conclusions

Gradient-echo dGEMRIC is reliable while offering the unique features of high image resolution and 3D biochemically sensitive MRI for the assessment of early cartilage degeneration.     

Relationship between myocardial T2* values and cardiac volumetric and functional parameters in β-thalassemia patients evaluated by cardiac magnetic resonance in association with serum ferritin levels

Purpose

Myocardial T2* cardiovascular magnetic resonance provides a rapid and reproducible assessment of cardiac iron load in thalassemia patients. Although cardiac involvement is mainly characterized by left ventricular dysfunction caused by iron overload, little is known about right ventricular function. The aim of this study was to assess the relationship between T2* value in myocardium and left–right ventricular volumetric and functional parameters and to evaluate the existing associations between left–right ventricles volumetric and functional parameter, myocardial T2* values and blood ferritin levels.

Materials and methods

A retrospective analysis of 208 patients with β-thalassemia major and thalassemia intermedia was performed (109 males and 99 females; mean age 37.7 ± 13 years; 143 thalassemia major, 65 thalassemia intermedia). Myocardial iron load was assessed by T2* measurements, and volumetric functions were analyzed using the steady state free precession sequence.

Results

A significant correlation was observed between EFLV and T2* (p = 0.0001), EFRV and T2* (p = 0.0279). An inverse correlation was present between DVLV and T2* (p = 0.0468), SVLV and T2* (p = 0.0003), SVRV and T2* (p = 0.0001). There was no significant correlation between cardiac T2* and LV–RV mass indices. A significant correlation was observed between T2* and serum ferritin levels (p < 0.001) and between EFLV and serum ferritin (p < 0.05).

Conclusion

Myocardial iron load assessed by T2* cardiac magnetic resonance is associated with deterioration in left–right ventricular function; this is more evident when T2* values fall below 14 ms. CMR appears to be a promising approach for cardiac risk evaluation in TM patients.