Faculty Bibliography

PURPOSE: To perform image quality comparison between accelerated multiband diffusion acquisition (mb2-DWI) and conventional diffusion acquisition (c-DWI) in patients undergoing clinically indicated liver MRI. METHODS: In this prospective study 22 consecutive patients undergoing clinically indicated liver MRI on a 3-T scanner equipped to perform multiband diffusion-weighed imaging (mb-DWI) were included. DWI was performed with single-shot spin-echo echo-planar technique with fat-suppression in free breathing with matching parameters when possible using c-DWI, mb-DWI, and multiband DWI with a twofold acceleration (mb2-DWI). These diffusion sequences were compared with respect to various parameters of image quality, lesion detectability, and liver ADC measurements. RESULTS: Accelerated mb2-DWI was 40.9% faster than c-DWI (88 vs. 149 s). Various image quality parameter scores were similar or higher on mb2-DWI when compared to c-DWI. The overall image quality score (averaged over the three readers) was significantly higher for mb-2 compared to c-DWI for b = 0 s/mm2 (3.48 +/- 0.52 vs. 3.21 +/- 0.54; p = 0.001) and for b = 800 s/mm2 (3.24 +/- 0.76 vs. 3.06 +/- 0.86; p = 0.010). Total of 25 hepatic lesions were visible on mb2-DWI and c-DWI, with identical lesion detectability. There was no significant difference in liver ADC between mb2-DWI and c-DWI (p = 0.12). Bland-Altman plot demonstrates lower mean liver ADC with mb2-DWI compared to c-DWI (by 0.043 x 10-3 mm2/s or 3.7% of the average ADC). CONCLUSION: Multiband technique can be used to increase acquisition speed nearly twofold for free-breathing DWI of the liver with similar or improved overall image quality and similar lesion detectability compared to conventional DWI.

AIM: To evaluate the performance of normalised apparent diffusion coefficient (ADC) values for prostate cancer assessment when performed by independent observers blinded to histopathology findings. MATERIALS AND METHODS: Fifty-eight patients undergoing 3 T phased-array coil magnetic resonance imaging (MRI) including diffusion-weighted imaging (DWI; maximal b-value 1000 s/mm2) before prostatectomy were included. Two radiologists independently evaluated the images, unaware of the histopathology findings. Regions of interest (ROIs) were drawn within areas showing visually low ADC within the peripheral zone (PZ) and transition zone (TZ) bilaterally. ROIs were also placed within regions in both lobes not suspicious for tumour, allowing computation of normalised ADC (nADC) ratios between suspicious and non-suspicious regions. The diagnostic performance of ADC and nADC were compared. RESULTS: For PZ tumour detection, ADC achieved significantly higher area under the receiver operating characteristic curve (AUC; p=0.026) and specificity (p=0.021) than nADC for reader 1, and significantly higher AUC (p=0.025) than nADC for reader 2. For TZ tumour detection, nADC achieved significantly higher specificity (p=0.003) and accuracy (p=0.004) than ADC for reader 2. For PZ Gleason score >3+3 tumour detection, ADC achieved significantly higher AUC (p=0.003) and specificity (p=0.005) than nADC for reader 1, and significantly higher AUC (p=0.023) than nADC for reader 2. For TZ Gleason score >3+3 tumour detection, ADC achieved significantly higher specificity (p=0.019) than nADC for reader 1. CONCLUSION: In contrast to prior studies performing unblinded evaluations, ADC was observed to outperform nADC overall for two independent observers blinded to the histopathology findings. Therefore, although strategies to improve the utility of ADC measurements in prostate cancer assessment merit continued investigation, caution is warranted when applying normalisation to improve diagnostic performance in clinical practice.

PURPOSE: To determine the frequency and characteristics of recommendations for additional imaging and/or intervention (RAIs) in abdominal CT and MRI interpretations that might be avoided through comprehensive comparison with all available prior examinations. METHODS: A total of 1,006 RAIs in abdominopelvic CT and MRI reports were retrospectively evaluated. Reports and images from each patient's prior imaging examinations, including those of all relevant body parts and modalities, were reviewed to determine if the RAI could have been avoided based on prior imaging. Frequency and characteristics of such "avoidable" RAIs were evaluated. RESULTS: A total of 41 of 1,006 (4.1%) RAIs were avoidable. The key prior examination that established the RAI as avoidable was a different modality in 53.7% (22 of 41) and on a different body area in 41.5% (17 of 41) of cases, including chest imaging in 31.7% (13 of 41). A total of 83.3% (5 of 6) adrenal RAIs, and 80.0% (4 of 5) liver RAIs were avoidable based on prior chest imaging. The key finding was present on the prior images but was not described in the report in 46.3% (19 of 41) of cases. A greater number of prior examinations were available in cases of avoidable RAIs (mean, 12.2 +/- 16.7) than in those of nonavoidable RAIs (mean, 5.7 +/- 9.5) (P < .001). CONCLUSIONS: A small fraction of RAIs can be avoided by performing a thorough evaluation of all prior imaging examinations, including different modalities and body parts. Nearly half of the key prior examinations did not report the finding, highlighting the importance of directly reviewing relevant images, particularly chest imaging for evaluation of indeterminate upper-abdominal findings. Configuration of PACS for optimized selection and display of relevant examination reports and images may facilitate such comparisons.

OBJECTIVE: The purpose of this article was to assess the feasibility of golden-angle radial acquisition with compress sensing reconstruction (Golden-angle RAdial Sparse Parallel [GRASP]) for acquiring high temporal resolution data for pharmacokinetic modeling while maintaining high image quality in patients with Crohn disease terminal ileitis. MATERIALS AND METHODS: Fourteen patients with biopsy-proven Crohn terminal ileitis were scanned using both contrast-enhanced GRASP and Cartesian breath-hold (volume-interpolated breath-hold examination [VIBE]) acquisitions. GRASP data were reconstructed with 2.4-second temporal resolution and fitted to the generalized kinetic model using an individualized arterial input function to derive the volume transfer coefficient (K(trans)) and interstitial volume (ve). Reconstructions, including data from the entire GRASP acquisition and Cartesian VIBE acquisitions, were rated for image quality, artifact, and detection of typical Crohn ileitis features. RESULTS: Inflamed loops of ileum had significantly higher K(trans) (3.36 +/- 2.49 vs 0.86 +/- 0.49 min(-1), p < 0.005) and ve (0.53 +/- 0.15 vs 0.20 +/- 0.11, p < 0.005) compared with normal bowel loops. There were no significant differences between GRASP and Cartesian VIBE for overall image quality (p = 0.180) or detection of Crohn ileitis features, although streak artifact was worse with the GRASP acquisition (p = 0.001). CONCLUSION: High temporal resolution data for pharmacokinetic modeling and high spatial resolution data for morphologic image analysis can be achieved in the same acquisition using GRASP.

PURPOSE: To determine multi-parametric MRI features that can help differentiate malignant omental caking from benign omental thickening in the setting of portal hypertension. METHODS: We identified 19 patients with an abnormal omentum on MRI and an available reference standard: 11 patients with portal hypertension and benign omental thickening (9 male, 2 female, mean age 58 +/- 6 years) and 8 patients with metastatic omental caking (4 male, 4 female, mean age 61 +/- 13 years). Criteria for benign omental thickening were no evidence of malignancy for at least 24 months of follow-up (n = 7), negative ascites cytology (n = 2), or absence of malignancy on pathologic analysis of liver explant (n = 2). Criteria for omental malignancy were positive omental biopsy (n = 6) or ascites cytology (n = 2). Two radiologists (R1 and R2) evaluated characteristics of the thickened omentum on MRI. RESULTS: Findings occurring with significantly higher frequency in malignant omental caking were hyperintensity on high b-value diffusion-weighted imaging (DWI) (R1 88% vs. 0%, R2 88% vs. 0%), hyperenhancement (R1 75% vs. 0%, R2 75% vs. 0%), and convex outer omental contour (R1 88% vs. 0%, R2 75% vs. 9%) (all p /= 0.058). CONCLUSION: Abnormal signal on DWI, hyperenhancement, and convex outer contour are helpful MRI features to differentiate malignant from benign omental thickening.

OBJECTIVE: The purpose of this article is to determine whether MRI features of renal cell carcinoma (RCC), such as enhancing solid component and T1 signal intensity, are associated with clinicopathologic outcomes. MATERIALS AND METHODS: This retrospective study included 241 RCCs in 230 patients who underwent preoperative MRI, had pathologic analysis results available, and were monitored for at least 3 months. A radiologist assessed tumor features on MRI, including unenhanced T1 signal relative to renal cortex and the percentage of solid enhancing components. The electronic medical record or follow-up images were reviewed to assess for the development of local recurrence or metastases. Statistical analysis was performed to correlate imaging features at MRI with pathologic and clinical outcome. RESULTS: The following tumor features were observed: predominantly cystic morphologic features (defined as solid component