Description: Objective The aim of the study was to analyze MR imaging features of renal epithelioid angiomyolipoma (EAML). Methods This study included 17 patients with histopathologically confirmed renal EAML who underwent renal MRI scanning before radical or partial nephrectomy. MR images were retrospectively reviewed and correlated with pathological findings. Result Fifteen lesions (88.2%) appeared as round or oval. The tumor-kidney interface was round in 14 lesions (82.4%). Fifteen tumors (88.2%) presented mainly isointensity on T1WI, and eleven tumors (64.7%) presented mainly hypointensity on T2WI. Twelve lesions (70.6%) showed restricted diffusion on DWI, and the mean ADC value was 1.23 ± 0.28 × 10 −3 mm 2 /s. Minimal fat component was identified as loss of signal intensity on opposed-phase MR images in 6 cases (35.3%). Sixteen lesions (100%) demonstrated inhomogeneous enhancement, and 7 of 16 masses (43.8%) showed reticular enhancement. Rapid wash-in and wash-out enhancement was seen in 13 masses (81.3%). In the corticomedullary phase, the mass showed markedly enhancement in 14 cases (87.5%). The irregular vessels and hemorrhage were detected in 4 cases (23.5%) and 7 cases (41.2%), respectively. One patient (5.9%) had a lymph node involvement at initial diagnosis, and showed distant metastasis after operation. In the immunohistochemical analysis, 15 tumors (88.2%) were positive for melanocytic marker (HMB45 or Melan-A), and all cases (100%) were negative for epithelial-associated markers (CK or AE1/AE3). Conclusion The presence of hypointensity on T2WI, restricted diffusion on DWI, round tumor-kidney interface, reticular, and marked enhancement (rapid wash-in and wash-out) should further raise suspicion for renal EAML. The diagnosis may be confirmed by pathological analysis.

Description: Purpose The purpose of the study was to evaluate the post-contrast appearance of local tumor progression (LTP) following renal ablation to better understand patterns of tumor recurrence and to optimize follow-up imaging protocols. Methods From 2002 to 2015, 913 patients underwent 988 renal ablation procedures for treatment of 1064 tumors. LTP was identified in 24 (2.6%) patients during median imaging follow-up of 30 months (range 0–139). One patient with LTP was followed with non-contrast MRI only and was excluded from evaluation. Three body radiologists reviewed the contrast-enhanced CT and/or MRI follow-up imaging in the remaining 23 patients to determine the timing and imaging appearance of the recurrent tumor. Results Local tumor progression was identified on contrast-enhanced CT or MRI at median 11 months (range 1 and 68) after renal ablation. Corticomedullary phase imaging was performed in 16/23 (70%) patients. LTP was identified on the corticomedullary phase in all cases, and was most conspicuous on the corticomedullary phase compared to any other phase of imaging in 15/16 (94%) patients. No cases of LTP were best visualized on non-contrast or excretory phase images. Conclusions Delayed recurrence following renal ablation is possible; therefore, extended follow-up is indicated in ablation patients. Almost all cases of LTP were best visualized on the corticomedullary phase of imaging, which should be included in any post-ablation imaging protocol. Excretory phase images were not required to diagnose LTP in any case and could be excluded from routine post-ablation follow-up.

Description: The skin and subcutaneous tissues are inevitably imaged as part of most body MRI studies. Incidental or even symptomatic skin lesions may, therefore, be detected and present a diagnostic challenge for the radiologist. We aim to provide a comprehensive review, with illustrative examples, of the skin abnormalities encountered on body MRI studies in our busy academic radiology department.

Description: All women, during their lifetime, are at risk of developing some form of gynecologic malignancy. The role of FDG-PET/CT has become more established in the management of gynecologic malignancies in the last decade. In this article, we will review the role of FDG-PET/CT in endometrial, cervical, ovarian, and vaginal cancer, by highlighting its strengths and limitations. While the role in initial or pre-operative staging for FDG-PET/CT is controversial, it allows noninvasive detection of equivocal or distant metastases, may alter stage and prognosis, and can guide or help eliminate unnecessary interventions that may not be beneficial. FDG-PET/CT is a useful adjunct to traditional staging with MR and CT.

Description: Purpose To determine whether objective volumetric whole-lesion apparent diffusion coefficient (ADC) distribution analysis improves upon the capabilities of conventional subjective small region-of-interest (ROI) ADC measurements for prediction of renal cell carcinoma (RCC) subtype. Methods This IRB-approved study retrospectively enrolled 55 patients (152 tumors). Diffusion-weighted imaging DWI was acquired at b values of 0, 250, and 800 s/mm 2 on a 1.5T system (Aera, Siemens Healthcare). Whole-lesion measurements were performed by a research fellow and reviewed by a fellowship-trained radiologist. Mean, median, skewness, kurtosis, and every 5th percentile ADCs were determined from the whole-lesion histogram. Linear mixed models that accounted for within-subject correlation of lesions were used to compare ADCs among RCC subtypes. Receiver-operating characteristic (ROC) curve analysis with optimal cutoff points from the Youden index was used to test the ability of ADCs to differentiate clear cell RCC (ccRCC), papillary RCC (pRCC), and oncocytoma subtypes. Results Whole-lesion ADC values were significantly different between pRCC and ccRCC, and between pRCC and oncocytoma, demonstrating strong ability to differentiate subtypes across the quantiles (both P  〈 0.001). Best percentile ROC analysis demonstrated AUC values of 95.2 for ccRCC vs. pRCC; 67.6 for oncocytoma vs. ccRCC; and 95.8 for oncocytoma vs. pRCC. Best percentile ROC analysis further indicated model sensitivities/specificities of 84.5%/93.1% for ccRCC vs. pRCC; 100.0%/10.3% for oncocytoma vs. ccRCC; and 88.5%/93.1% for oncocytoma vs. pRCC. Conclusion The objective methodology of whole-lesion volumetric ADC measurements maintains the sensitivity/specificity of conventional expert-based ROI analysis, provides information on lesion heterogeneity, and reduces observer bias.

Description: Purpose To investigate if multiphasic multidetector computed tomography (MDCT) enhancement profiles can distinguish clear cell renal cell carcinomas (ccRCCs) with high carbonic anhydrase-IX (CA-IX) expression from ccRCCs with low CA-IX expression. Methods With IRB approval for this retrospective study, we derived a cohort of 105 histologically proven ccRCCs with preoperative 4-phase renal mass MDCT from 2001 to 2013. Following manual segmentation, the computer-assisted detection algorithm selected a 0.5-cm-diameter region of maximal attenuation within each lesion in each phase. CA-IX expression level was determined by immunohistochemical staining of tumor specimens. In the high and low CA-IX expression subgroups, the magnitude of enhancement and washout were compared using t tests; the performance of contrast washout in differentiating between subgroups was assessed with logistic regression analysis. Results ccRCCs with high and low CA-IX expression both exhibited peak enhancement in the corticomedullary phase. ccRCCs with high CA-IX expression demonstrated significantly greater relative nephrographic washout than those with low CA-IX expression (18.4% vs. 7.8%, p  = 0.03). ccRCCs with high CA-IX expression had greater relative excretory washout than ccRCCs with low CA-IX expression with a trend toward significance (33.4% vs. 25.2%, p  = 0.05). After controlling for tumor size and stage, for distinguishing ccRCCs with high and low CA-IX expression, relative excretory washout had a sensitivity, negative predictive value, accuracy, and positive predictive value of 99% (65/66), 88% (7/8), 69% (72/105), and 67% (65/97), respectively. Conclusion Relative nephrographic and excretory washout may have the potential to help distinguish ccRCCs with high and low CA-IX expression, but this requires further validation.

Description: Since the introduction of CT colonography (CTC) in the mid-1990s, there have been continuous advancements in the examination technique and advanced visualization software for interpretation. This review will cover the origins of CTC as a natural extension of abdominal CT imaging, and discuss the evolution of CTC through the subsequent clinical phases of feasibility, validation, and implementation.

Description: Microbubble ultrasound contrast agents (UCAs) were recently approved by the Food and Drug administration for non-cardiac imaging. The physical principles of UCAs, methods of administration, dosage, adverse effects, and imaging techniques both current and future are described. UCAs consist of microbubbles in suspension which strongly interact with the ultrasound beam and are readily detectable by ultrasound imaging systems. They are confined to the blood pool when administered intravenously, unlike iodinated and gadolinium contrast agents. UCAs have a proven safety record based on over two decades of use, during which they have been used in echocardiography in the U.S. and for non-cardiac imaging in the rest of the world. Adverse effects are less common with UCAs than CT/MR contrast agents. Compared to CT and MR, contrast-enhanced ultrasound has the advantages of real-time imaging, portability, and reduced susceptibility to metal and motion artifact. UCAs are not nephrotoxic and can be used in renal failure. High acoustic amplitudes can cause microbubbles to fragment in a manner that can result in short-term increases in capillary permeability or capillary rupture. These bioeffects can be beneficial and have been used to enhance drug delivery under appropriate conditions. Imaging with a mechanical index of 〈 0.4 preserves the microbubbles and is not typically associated with substantial bioeffects. Molecularly targeted ultrasound contrast agents are created by conjugating the microbubble shell with a peptide, antibody, or other ligand designed to target an endothelial biomarker associated with tumor angiogenesis or inflammation. These microbubbles then accumulate in the microvasculature at target sites where they can be imaged. Ultrasound contrast agents are a valuable addition to the diagnostic imaging toolkit. They will facilitate cross-sectional abdominal imaging in situations where contrast-enhanced CT and MR are contraindicated or impractical.