Faculty Bibliography

We compared individual computed tomography (CT) and MRI findings in differentiating acute from chronic cholecystitis. Thirty-seven patients undergoing both studies before cholecystectomy were included. Two radiologists (R1/R2) independently assessed all cases. For detecting acute cholecystitis, MRI showed better sensitivity (R1) using gallbladder wall thickening, accuracy (R1) and sensitivity (R1) using gallstones, sensitivity (R1 and R2) and accuracy (R2) using gallbladder wall hyperemia, accuracy (R1 and R2) using gallbladder wall defect, and accuracy (R2) using adjacent liver hyperemia (P=.004-.063). MRI also showed better specificity (R2) using pericholecystic fat stranding (P=.016). Overall, several findings showed better sensitivity and/or accuracy for acute cholecystitis on MRI than CT.

AIM: To identify retrospectively potential associations between apparent diffusion coefficient (ADC) values of pancreatic adenocarcinoma and tumour grade as well as other pathological features, using histopathological assessment from the Whipple procedure as the reference standard. MATERIALS AND METHODS: Thirty patients with pancreatic adenocarcinoma underwent magnetic resonance imaging (MRI) including diffusion-weighted imaging with b-values of 0 and 500 s/mm before the Whipple procedure. Two radiologists independently recorded the ADC values of the tumour and benign pancreas for all cases. ADC values were compared with histopathological findings following the Whipple procedure. RESULTS: The intra-class correlation coefficient was 0.689 for benign pancreas and 0.695 for tumours, indicating good inter-reader agreement for ADC values. The mean ADC value was significantly lower in tumours than in benign pancreas for both readers (reader 1: 1.74 +/- 0.34 x 10 mm/s versus 2.08 +/- 0.48 x 10 mm/s, respectively, p = 0.006; reader 2: 1.69 +/- 0.41 x 10 mm/s versus 2.11 +/- 0.54 x 10 mm/s, respectively, p < 0.001). However, there was no significant difference in mean ADC between poorly and well/moderately differentiated tumours for either reader (reader 1: 1.69 +/- 0.36 x 10 mm/s versus 1.78 +/- 0.33 x 10 mm/s, respectively, p = 0.491; reader 2: 1.62 +/- 0.33 x 10 mm/s versus 1.75 +/- 0.49 x 10 mm/s, respectively, p = 0.405). The area under the curve (AUC) for differentiation of poorly and well/moderately differentiated tumours was 0.611 and 0.596 for readers 1 and 2, respectively, and was not significantly better than an AUC of 0.500 for either reader (p >/= 0.306). In addition, ADC was not significantly different for either reader between tumours with stage T3 versus stage T1/T2, between tumours with and without metastatic peri-pancreatic lymph nodes, or between tumours located in the pancreatic head versus other pancreatic regions (p >/= 0.413). CONCLUSION: No associations between ADC values of pancreatic adenocarcinoma and tumour grade or other adverse pathological features were observed.

PURPOSE: Past studies have identified a high frequency of recommendations for additional imaging (RAI) for computed tomography (CT) studies performed in an emergency department (ED), thereby potentially contributing to increased imaging utilization and costs. The purpose of this study was to compare rates of RAI within the ED setting between ED-based and organ-based subspecialty radiologists. METHODS: We identified 600 ED CT studies, comprising 200 head, chest, and abdominal CT studies, split equally between cases reviewed by ED-based and organ-based radiologists. Frequency of RAI for the three examinations was compared between these subspecialty groups. RESULTS: Frequencies of RAI were 21.5 %, 13.5 %, and 5.5 % for CT examinations of the chest, abdomen, and brain, respectively. There was a significantly higher frequency of RAI for chest CT studies interpreted by chest radiologists than by ED radiologists (28.0 % vs. 15.0 %, respectively, p = 0.036), largely due to a higher rate of RAI for incidentally detected lung nodules and masses as well as other pulmonary parenchymal abnormalities by chest radiologists. There was no significant difference in RAI on brain or abdominal CT studies between the two groups (p = 0.426-1.0). However, on abdominal studies, only ED-based radiologists provided RAI for abnormalities of the bowel or uterus, while only organ-based radiologists provided RAI for pancreatic abnormalities. Only 25.6 % of RAI were subsequently performed at our institution. CONCLUSION: For chest CT studies performed at the authors' institution, differences in management of incidental pulmonary nodules contributed to a significantly higher frequency of RAI by chest radiologists than by ED-based radiologists. Further investigation of the impact of these differences on cost and patient outcomes is warranted.

Compared with earlier prostate MRI techniques that suffered from relatively poor sensitivity and specificity for detecting prostate cancer because of their reliance predominantly on morphology, multiparametric prostate MRI (mpMRI) in 2013 provides a wealth of functional information that has made possible vastly improved detection and characterization of prostate cancer. Our aims in this article are to describe the various imaging sequences that comprise the mpMRI exam, as well as to review current literature on the strengths/weaknesses of these sequences; to delineate strategies for standardizing interpretation and reporting of MRI results; and finally, to expound on the role that prostate MRI currently does and potentially can play in clinical practice.

OBJECTIVE: Numerous prior studies have shown the utility of apparent diffusion coefficient values in cervical cancer assessment, particularly in differentiation from benign cervix. This article will discuss histogram-based analysis for detection of adverse histologic features of cervical cancer. CONCLUSION: The study by Downey et al. in this issue investigates histogram-based analysis for detection of adverse histologic features of cervical cancer, including subtype and grade. This approach offers a more complete assessment of tumor texture and heterogeneity. Given the potential utility suggested by the results of this study, additional larger studies are warranted.

PURPOSE: To improve robustness to patient motion of "fresh blood imaging" (FBI) for lower extremity noncontrast MR angiography. METHODS: In FBI, two sets of three-dimensional fast spin echo images are acquired at different cardiac phases and subtracted to generate bright-blood angiograms. Routinely performed with a single coronal slab and sequential acquisition of systolic and diastolic data, FBI is prone to subtraction errors due to patient motion. In this preliminary feasibility study, FBI was implemented with two sagittal imaging slabs, and the systolic and diastolic acquisitions were interleaved to minimize sensitivity to motion. The proposed technique was evaluated in volunteers and patients. RESULTS: In 10 volunteers, imaged while performing controlled movements, interleaved FBI demonstrated better tolerance to subject motion than sequential FBI. In one patient with peripheral arterial disease, interleaved FBI offered better depiction of collateral flow by reducing sensitivity to inadvertent motion. CONCLUSIONS: FBI with interleaved acquisition of diastolic and systolic data in two sagittal imaging slabs offers improved tolerance to patient motion. Magn Reson Med, 2013. (c) 2013 Wiley Periodicals, Inc.

OBJECTIVE: To evaluate the prognostic implications of the MRI appearance and pathological features of papillary renal cell carcinoma (pRCC). METHODS: A total of 128 pRCC in 115 patients who underwent preoperative MRI were characterised in terms of pathological type (type 1 vs. type 2), MRI appearance (focal vs. infiltrative) and additional MRI features. Patients were classified on the basis of the presence or absence of metastatic disease. RESULTS: There were 65 focal type 1, 54 focal type 2 and 9 infiltrative pRCC. All infiltrative pRCC were of histopathological type 2. Renal vein thrombus was present in 89 % of infiltrative pRCC and no cases of focal pRCC. Metastatic disease was observed in 3.7 % of focal type 1, 7.5 % of focal type 2 and 75.0 % of infiltrative type 2 pRCC. Infiltrative MRI appearance was a significant predictor of metastatic disease, independent of pathological type, size and T stage (P 0.5). CONCLUSION: Infiltrative MRI appearance and renal vein thrombus identify a subset of pathological type 2 pRCC at a significantly increased risk of metastatic disease.

OBJECTIVE: The objectives of this study were to develop a new method for free-breathing contrast-enhanced multiphase liver magnetic resonance imaging (MRI) using a combination of compressed sensing, parallel imaging, and radial k-space sampling and to demonstrate the feasibility of this method by performing image quality comparison with breath-hold cartesian T1-weighted (conventional) postcontrast acquisitions in healthy participants. MATERIALS AND METHODS: This Health Insurance Portability and Accountability Act-compliant prospective study received approval from the institutional review board. Eight participants underwent 3 separate contrast-enhanced fat-saturated T1-weighted gradient-echo MRI examinations with matching imaging parameters: conventional breath-hold examination with cartesian k-space sampling volumetric interpolate breath hold examination (BH-VIBE) and free-breathing acquisitions with interleaved angle-bisection and continuous golden-angle radial sampling schemes. Interleaved angle-bisection and golden-angle data from each 100 consecutive spokes were reconstructed using a combination of compressed sensing and parallel imaging (interleaved-angle radial sparse parallel [IARASP] and golden-angle radial sparse parallel [GRASP]) to generate multiple postcontrast phases.Arterial- and venous-phase BH-VIBE, IARASP, and GRASP reconstructions were evaluated by 2 radiologists in a blinded fashion. The readers independently assessed quality of enhancement (QE), overall image quality (IQ), and other parameters of image quality on a 5-point scale, with the highest score indicating the most desirable examination. Mixed model analysis of variance was used to compare each measure of image quality. RESULTS: Images of BH-VIBE and GRASP had significantly higher QE and IQ values compared with IARASP for both phases (P < 0.05). The differences in QE between BH-VIBE and GRASP for the arterial and venous phases were not significant (P > 0.05). Although GRASP had lower IQ score compared with BH-VIBE for the arterial (3.9 vs 4.8; P < 0.0001) and venous (4.2 vs 4.8; P = 0.005) phases, GRASP received IQ scores of 3 or more in all participants, which was consistent with acceptable or better diagnostic image quality. CONCLUSION: Contrast-enhanced multiphase liver MRI of diagnostic quality can be performed during free breathing using a combination of compressed sensing, parallel imaging, and golden-angle radial sampling.