Faculty Bibliography

PURPOSE: To determine if pretreatment apparent diffusion coefficient (ADC) of leiomyomas could predict volumetric response (VR) following uterine artery embolization (UAE). MATERIALS AND METHODS: We retrospectively studied 11 women who underwent pelvic MRI before and >120 days following UAE. MRI included conventional and diffusion weighted imaging sequences. Percentage change in leiomyoma volume was determined by multiplanar T2-weighted imaging. A Pearson correlation coefficient was calculated between leiomyoma VR following UAE and the following pre-embolization parameters: initial volume, relative enhancement, relative T2 signal intensity (SI) and ADC. Receiver operating characteristic (ROC) curve analysis was used to determine the sensitivity and specificity of ADC for predicting volumetric response. RESULTS: Twenty-eight leiomyomas were included with a mean interval from UAE to follow-up MRI of 207 days. The preprocedural volume of the leiomyomas ranged from 18 to 182 cm(3) (median 47 cm(3)). and ADC ranged from 0.37 to 1.71 mm(2)/s (mean 0.80 mm(2)/s). All leiomyomas were 100% necrotic following UAE. Leiomyoma VR following UAE was 48% +/- 3.5%. with significant correlation between VR and ADC (r = 0.41; P = 0.017) but no correlation with initial leiomyoma volume, relative T2 SI, or relative enhancement. Using a threshold of 0.875 x 10(-3) mm(2)/s, ADC could predict > 50% VR with sensitivity and specificity of 70% and 83%, respectively. CONCLUSION: Pre-UAE ADC of leiomyomas correlated significantly with percent VR following UAE. In contrast, no correlation was seen between VR post-UAE and conventional imaging findings. This suggests that VR following UAE depends on leiomyoma histology reflected in DWI rather than features revealed by conventional MRI

AIM: To determine whether the location of the computed tomography (CT) whirl sign can be used to help differentiate caecal from sigmoid volvulus. MATERIALS AND METHODS: Thirty-one patients (mean age 64.6 years) underwent multidetector CT and had confirmed colonic volvulus. There were 15 patients with caecal volvulus and 16 with sigmoid volvulus. Axial and coronal images were retrospectively evaluated on the picture archiving and communication system (PACS) by two reviewers in consensus without knowledge of the final diagnosis to determine whether a CT whirl sign was present and, if so, was the location to the right of midline or in the midline/left. The location of the twisting at imaging was correlated with whether the patient had caecal or sigmoid volvulus. Fisher's exact test was used to determine whether there was an association between the location of the twist (right versus mid-left) and the location of the colonic volvulus (caecal versus sigmoid). The non contrast CT (NCCT) examinations of 30 additional patients without colonic volvulus were evaluated for the presence or absence of a CT whirl sign. RESULTS: All 31 patients with colonic volvulus had a CT whirl sign. No patient who underwent NCCT for kidney stones demonstrated a CT whirl sign. According to Fisher's exact test, there was a highly significant association (p<0.0001) between the location of the twist (right versus mid-left) and the location of the colonic volvulus (caecal versus sigmoid). Using the location of the twist as a predictor of whether the volvulus was caecal or sigmoid provided a correct diagnosis for 93.3% (14/15) of the patients with caecal volvulus and 100% (16/16) of those with sigmoid volvulus, yielding an overall diagnostic accuracy of 96.8% (30/31). CONCLUSION: The location of the mesenteric twist (CT whirl sign) is a highly accurate finding in discriminating caecal from sigmoid volvulus

OBJECTIVE: The purpose of our study was to compare the visibility of prostate cancer on trace diffusion-weighted (DW) images and the apparent diffusion coefficient (ADC) map. MATERIALS AND METHODS: In this retrospective study, 45 patients with prostate cancer underwent preoperative MRI, including DW imaging (DWI) (b values 0, 500, and 1,000 s/mm(2)). A single observer reviewed the images in conjunction with tumor maps constructed from prostatectomy. For 132 peripheral zone (PZ) tumor foci, the visibility and contrast relative to benign PZ were recorded for T2-weighted imaging, trace DWI b500 images, trace DWI b1,000 images, and ADC maps. Trace DWI b1,000 images and ADC maps were compared in terms of Gleason score, size, normalized T2 signal intensity, ADC, and normalized ADC of visible tumors. RESULTS: For each image set, the percentage of visible tumor foci and contrast relative to benign PZ were as follows: T2-weighted imaging, 80.3% and 0.411; trace DWI b500, 26.5% and 0.131; trace DWI b1,000, 46.2% and 0.119; and ADC maps, 62.1% and 0.309. Forty-seven tumor foci were visible on both trace DWI b1,000 images and ADC maps, 14 only on trace DWI b1,000 images, 35 only on ADC maps, and 36 on neither image set. There was no significant difference in Gleason score, size, normalized T2 signal intensity, ADC, or normalized ADC between tumors visible only on trace DWI b1,000 images and those visible only on ADC maps. CONCLUSION: Given a greater proportion of tumors visible on the ADC map than trace DWI and greater contrast relative to benign PZ on the ADC map, we suggest that, when performing DWI of the prostate, careful attention be given to the ADC map for tumor identification

PURPOSE: To compare single-shot echo-planar imaging (SS EPI) diffusion-weighted MRI (DWI) of abdominal organs between 1.5 Tesla (T) and 3.0T in healthy volunteers in terms of image quality, apparent diffusion coefficient (ADC) values, and ADC reproducibility. MATERIALS AND METHODS: Eight healthy volunteers were prospectively imaged in this HIPAA-compliant IRB-approved study. Each subject underwent two consecutive scans at both 1.5 and 3.0T, which included breathhold and free-breathing DWI using a wide range of b-values (0 to 800 s/mm(2) ). A blinded observer rated subjective image quality (maximum score= 8), and a separate observer placed regions of interest within the liver, renal cortices, pancreas, and spleen to measure ADC at each field strength. Paired Wilcoxon tests were used to compare abdominal DWI between 1.5T and 3.0T for specific combinations of organs, b-values, and acquisition techniques. RESULTS: Subjective image quality was significantly lower at 3.0T for all comparisons (P = 0.0078- 0.0156). ADC values were similar at 1.5T and 3.0T for all assessed organs, except for lower liver ADC at 3.0T using b0-500-600 and breathhold technique. ADC reproducibility was moderate at both 1.5T and 3.0T, with no significant difference in coefficient of variation of ADC between field strengths. CONCLUSION: Compared with 1.5T, SS EPI at 3.0T provided generally similar ADC values, however, with worse image quality. Further optimization of abdominal DWI at 3.0T is needed. J. Magn. Reson. Imaging 2011;33:128-135. (c) 2010 Wiley-Liss, Inc

BACKGROUND AND PURPOSE: Neuro-axonal damage is a well known sequelae of MS pathogeneses. Consequently, our aim was to test whether the approximately 20% of patients with MS exhibiting a clinically benign disease course also have minimal neural dysfunction as reflected by the global concentration of their MR imaging marker NAA. MATERIALS AND METHODS: Q(NAA) was obtained with nonlocalizing whole-head (1)H-MR spectroscopy in 43 patients with benign RRMS (30 women, 13 men; mean age, 44.7 +/- 7.3 years of age) with 21.0 +/- 4.4 years (range, 15-35 years) of disease duration from the first symptom and an EDSS score of 1.9 (range, 0-3). Q(NAA) was by divided by the brain volume (from MR imaging segmentation) to normalize it into WBNAA. All participants gave institutional review board-approved written informed consent, and the study was HIPAA compliant. RESULTS: The patients' lesion load was 12.2 +/- 7.7 cm(3). Their 8.3 +/- 1.8 mmol/L WBNAA was 35% lower than that in controls (P < .001). Individual average loss rates (absolute loss compared with controls divided by disease duration) clustered around 0.22 +/- 0.09 mmol/L/year (1.7%/year, assuming monotonic decline). This rate could be extrapolated from that already reported for patients with RRMS of much shorter disease duration. WBNAA did not correlate with lesion load or EDSS. CONCLUSIONS: Normal WBNAA is not characteristic of benign MS and is not an early predictor of its course. These patients, therefore, probably benefit from successful compensation and sparing of eloquent regions. Because they may ultimately have a rapid decline once their brain plasticity is exhausted, they may benefit from treatment options offered to more affected patients

PURPOSE: : To compare image quality and lesion detection in postcontrast liver magnetic resonance imaging (MRI) between volumetric interpolated breath-hold examination (VIBE) sequences that achieve fat suppression via chemically selective fat saturation (FS-VIBE) and a 2-point Dixon water-fat separation method (Dixon-VIBE). MATERIALS AND METHODS: : Thirty patients underwent contrast-enhanced liver MRI at 1.5 T in which Dixon-VIBE was performed immediately after a delayed FS-VIBE. Two radiologists in consensus reviewed the sequences for a variety of qualitative and quantitative image quality measures and for lesion detection. RESULTS: : Dixon-VIBE received nearly perfect scores for strength and homogeneity of fat suppression that were significantly better than scores for FS-VIBE, with an associated significant improvement in liver-fat contrast (P < 0.0001 for all comparisons). Dixon-VIBE also received significantly better scores for sharpness of intrahepatic vessels (P = 0.0029) and overall image quality (P < 0.0001). Despite a slightly longer acquisition time for Dixon-VIBE, there was no significant difference in motion artifact (P = 0.3877). There was no significant difference for sensitivity, positive predictive value, or contrast relative to background liver for focal lesions (P = 0.448, P = 0.347, and P = 0.2312, respectively). CONCLUSIONS: : For postcontrast liver MRI, Dixon-VIBE demonstrated significantly improved fat suppression. Various assessments of lesion detection showed no significant difference between sequences

OBJECTIVE: The purpose of this study was to retrospectively describe the MRI features of the pathologically related entities renal oncocytoma and chromophobe renal cell carcinoma (RCC). MATERIALS AND METHODS: Twenty-eight cases of histologically proven renal oncocytoma and 15 of chromophobe RCC evaluated with preoperative MRI from January 2003 through June 2009 at our institution were independently reviewed for an array of MRI features by two radiologists blinded to the final histopathologic diagnosis. These features were tabulated and compared between chromophobe RCC and renal oncocytoma by use of the Mann-Whitney test and binary logistic regression. RESULTS: Renal oncocytoma and chromophobe RCC showed no significant difference in size or any of 16 qualitative imaging features (p = 0.0842-1.0, reader 1; p = 0.0611-1.0, reader 2). Microscopic fat, hemorrhage, cysts, infiltrative margins, perinephric fat invasion, renal vein invasion, enhancement homogeneity, and hypervascularity were each observed in less than 20% of cases by both readers. A central scar and segmental enhancement inversion (a recently described finding in which early contrast-enhanced images show relatively more enhanced and less enhanced intralesional components with inversion of their relative enhancement on later images) were observed by both readers in at least 10% of cases of both renal oncocytoma and of chromophobe RCC with no significant difference between the two entities (p = 0.2092-0.2960). CONCLUSION: We have presented the largest series to date of the MRI features of both renal oncocytoma and chromophobe RCC. These related entities exhibited similar findings, and no MRI features were reliable in distinguishing between them

Study Type - Diagnostic (exploratory cohort)Level of Evidence 2b OBJECTIVE: To evaluate the role of magnetic resonance imaging (MRI) and up-standing ultrasonography (USUS) for the detection of inguinal hernias (IHs) before open radical retropubic prostatectomy (ORRP) and to assess factors associated with the presence of IHs in these men. PATIENTS AND METHODS: From 1 July 2007 to 1 February 2009, 164 men underwent preoperative evaluation for ORRP by one surgeon. Of these men 113 (69%) were evaluated for IHs by physical examination (PE), USUS and MRI. In all 226 groins were examined. Any IH diagnosed by any method was considered a true positive. The sensitivity, negative predictive value (NPV), and concordance were calculated for the three diagnostic methods. Possible predictive factors of IHs were evaluated. RESULTS: Of the 226 groins evaluated, 72 (32%) IHs were diagnosed. USUS had the greatest sensitivity (69.4%) and the highest NPV (87.5%). MRI had fair agreement with PE and USUS, while USUS and PE had moderate agreement with each other. No factor was associated with an increased likelihood of preoperative diagnosis of IH. CONCLUSIONS: This study was limited by the lack of a reference standard to diagnose IH. USUS was the most sensitive method for the detection of IH. We recommend that all men undergoing ORRP should be evaluated for IHs by PE and at least one imaging method and that IHs be repaired at the time of ORRP, obviating the need for a second surgical procedure

OBJECTIVE: The purpose of our study was to assess the utility of the apparent diffusion coefficient (ADC) in distinguishing low-grade and high-grade clear cell renal cell carcinoma (ccRCC). MATERIALS AND METHODS: The cases of 57 patients with pathologically proven ccRCC who underwent preoperative MRI, including diffusion-weighted imaging, were retrospectively assessed. ADC values were obtained from ADC maps calculated using b-value combinations of 0 and 400 s/mm(2) and of 0 and 800 s/mm(2) (hereafter referred to as ADC-400 and ADC-800). Lesions were also evaluated for an array of conventional MRI features. A single expert uropathologist reviewed all slides to determine nuclear grade. The utility of ADC for detecting high-grade ccRCC, alone and in combination with conventional MRI features, was assessed using receiver operating characteristic (ROC) analysis and binary logistic regression. RESULTS: ADC-400 and ADC-800 were significantly lower among high-grade than among low-grade ccRCC (2.24 +/- 0.50 mm(2)/s vs 1.59 +/- 0.57 mm(2)/s for ADC-400, p < 0.001; 1.85 +/- 0.40 mm(2)/s vs 1.28 +/- 0.48 mm(2)/s for ADC-800; p < 0.001). The area under the ROC curve for identifying high-grade ccRCC using ADC-400 and ADC-800 was 0.801 and 0.824 respectively (p = 0.606), with optimal thresholds, sensitivity, and specificity as follows: ADC-400: 2.17 mm(2)/s, 88.5%, 64.5% and ADC-800: 1.20 mm(2)/s, 65.4%, 96.0%. Using multivariate logistic regression, only necrosis (p = 0.0229) and perinephric fat invasion (p = 0.0160) were retained among conventional imaging features as independent risk factors for high-grade ccRCC. The accuracy of the logistic regression model for predicting high-grade ccRCC was significantly improved by inclusion of either ADC-400 (p = 0.0143) or ADC-800 (p = 0.015). CONCLUSION: ADC is significantly lower in high-grade ccRCC compared with low-grade ccRCC and increases the accuracy for detecting high-grade ccRCC compared with conventional MRI features alone