Michael T. Corwin

Differentiation of Ovarian Endometriomas from Hemorrhagic Cysts at MR Imaging: Utility of the T2 Dark Spot Sign

PURPOSE To determine sensitivity and specificity of the T2 dark spot sign in helping to distinguish endometriomas from other hemorrhagic adnexal lesions. MATERIALS AND METHODS This HIPAA-compliant, institutional review board-approved retrospective study, with informed consent waived, included 56 women (mean age, 38.8 years; range, 18-66 years). With a radiology database search of pelvic magnetic resonance images from December 16, 2002, to July 24, 2012, 74 cystic hemorrhagic adnexal lesions with hyperintense signal on T1-weighted images were identified. Lesions were excluded if they had solid enhancing components. Final diagnosis was established with pathologic analysis for all endometriomas and neoplasms. Hemorrhagic cysts were diagnosed with pathologic analysis (n = 7), follow-up imaging (n = 13), or prior ultrasonography (n = 5). Two radiologists independently reviewed cases and recorded the presence or absence of T2 shading and T2 dark spots. T2 dark spots were defined as discrete, well-defined markedly hypointense foci within the adnexal lesion on T2-weighted images. Sensitivity, specificity, and positive and negative predictive values of the T2 dark spot sign in distinguishing endometriomas from nonendometrioma hemorrhagic lesions were calculated. RESULTS Sixteen of 45 endometriomas (36%), zero of 25 hemorrhagic cysts, and two of four neoplasms (50%) (all serous cystadenomas) demonstrated T2 dark spots. Forty-two of 45 endometriomas (93%), 12 of 25 hemorrhagic cysts (48%), and four of four neoplasms (100%) demonstrated T2 shading. Sensitivity, specificity, positive predictive value, and negative predictive value of T2 dark spots for differentiating endometriomas from other hemorrhagic cystic ovarian masses were 36% (95% confidence interval [CI]: 19.8, 51.3), 93% (95% CI: 83.9, 100), 89% (95% CI: 63.9, 98.1), and 48% (95% CI: 34.8, 61.8), respectively, and for T2 shading, they were 93% (95% CI: 84.0, 100), 45% (95% CI: 27.8, 61.9), 72% (95% CI: 58.9, 83.0), and 81% (95% CI: 53.7, 95.0), respectively. CONCLUSION The T2 dark spot sign has high specificity for chronic hemorrhage and is useful to differentiate endometriomas from hemorrhagic cysts. The T2 shading sign is sensitive but not specific for endometriomas. Online supplemental material is available for this article.

Multidetector CT of Vascular Compression Syndromes in the Abdomen and Pelvis

Certain abdominopelvic vascular structures may be compressed by adjacent anatomic structures or may cause compression of adjacent hollow viscera. Such compressions may be asymptomatic; when symptomatic, however, they can lead to a variety of uncommon syndromes in the abdomen and pelvis, including median arcuate ligament syndrome, May-Thurner syndrome, nutcracker syndrome, superior mesenteric artery syndrome, ureteropelvic junction obstruction, ovarian vein syndrome, and other forms of ureteral compression. These syndromes, the pathogenesis of some of which remains controversial, can result in nonspecific symptoms of epigastric or flank pain, weight loss, nausea and vomiting, hematuria, or urinary tract infection. Direct venography or duplex ultrasonography can provide hemodynamic information in cases of vascular compression. However, multidetector computed tomography is particularly useful in that it allows a comprehensive single-study evaluation of the anatomy and resultant morphologic changes. Anatomic findings that can predispose to these syndromes may be encountered in patients who are undergoing imaging for unrelated reasons. However, the diagnosis of these syndromes should not be made on the basis of imaging findings alone. Severely symptomatic patients require treatment, which is generally surgical, although endovascular techniques are increasingly being used to treat venous compressions.

Evidence Supporting LI-RADS Major Features for CT- and MR Imaging–based Diagnosis of Hepatocellular Carcinoma: A Systematic Review

The Liver Imaging Reporting and Data System (LI-RADS) standardizes the interpretation, reporting, and data collection for imaging examinations in patients at risk for hepatocellular carcinoma (HCC). It assigns category codes reflecting relative probability of HCC to imaging-detected liver observations based on major and ancillary imaging features. LI-RADS also includes imaging features suggesting malignancy other than HCC. Supported and endorsed by the American College of Radiology (ACR), the system has been developed by a committee of radiologists, hepatologists, pathologists, surgeons, lexicon experts, and ACR staff, with input from the American Association for the Study of Liver Diseases and the Organ Procurement Transplantation Network/United Network for Organ Sharing. Development of LI-RADS has been based on literature review, expert opinion, rounds of testing and iteration, and feedback from users. This article summarizes and assesses the quality of evidence supporting each LI-RADS major feature for diagnosis of HCC, as well as of the LI-RADS imaging features suggesting malignancy other than HCC. Based on the evidence, recommendations are provided for or against their continued inclusion in LI-RADS.

Differences in Liver Imaging and Reporting Data System Categorization Between MRI and CT.

OBJECTIVE The purpose of this study is to determine whether focal liver observations are categorized differently by CT and MRI using the Liver Imaging and Reporting Data System (LI-RADS). MATERIALS AND METHODS We performed a retrospective review of 58 patients at risk for hepatocellular carcinoma who underwent liver protocol CT and MRI within 1 month of each other. Two readers assigned a LI-RADS category for all focal liver observations in consensus. A significant category upgrade was defined as a change from LI-RADS categories 1 and 2 or nonvisualization to LI-RADS categories 3-5, from LI-RADS category 3 to category 4 or 5, from LI-RADS category 4 to category 5, or from any category to LI-RADS category 5V. A significant downgrade was defined as a change from LI-RADS category 5 to categories 1-4, from LI-RADS category 4 to categories 1-3, or from LI-RADS category 3 to categories 1 or 2. RESULTS The LI-RADS category was different between CT and MRI for 77.2% (176/228) of observations. A significant upgrade occurred on MRI for 42.5% (97/228) of observations because of nonvisualization by CT (n = 78), capsule (n = 8), arterial hyperenhancement (n = 4), intratumoral fat (n = 2), larger size (n = 2), tumor in portal vein (n = 2), and wash-out (n = 1). Of these 97 upgraded observations, two were upgraded to LI-RADS category 5V, 15 were upgraded to category 5, and 13 were upgraded to category 4. A significant downgrade occurred on MRI for 8.8% (20/228) of observations because of marked T2 hyperintensity (n = 14), smaller size (n = 2), wedge shape (n = 2), and marked T2 hypointensity (n = 2). CONCLUSION LI-RADS categorization of focal liver observations is dependent on imaging modality. MRI results in both upgraded and downgraded categorization compared with CT in an important proportion of observations.

Ovarian Fibromas and Fibrothecomas Sonographic Correlation With Computed Tomography and Magnetic Resonance Imaging: A 5-Year Single-Institution Experience

To evaluate imaging characteristics of ovarian fibromas and fibrothe‐comas and to identify select clinical markers and imaging features to help in their diagnosis.

MR Angiography of Renal Transplant Vasculature with Ferumoxytol:: Comparison of High-Resolution Steady-State and First-Pass Acquisitions.

RATIONALE AND OBJECTIVES This work aimed to quantify the differences in signal-to-noise ratio (SNR) and vessel sharpness between steady-state and first-pass magnetic resonance angiography (MRA) with ferumoxytol in renal transplant recipients. MATERIALS AND METHODS We performed a retrospective study of adult patients who underwent steady-state and first-pass MRA with ferumoxytol to evaluate renal transplant vasculature. SNR was calculated in the external iliac artery, and vessel sharpness was calculated in the external iliac and renal transplant arteries for both acquisitions. Data were compared using Students t test. RESULTS Fifteen patients were included (mean age 56.9 years, 10 males). The mean SNR of the external iliac artery was 42.2 (SD, 11.9) for the first-pass MRA and 41.8 (SD, 9.7) for the steady-state MRA (p = 0.92). The mean vessel sharpness was significantly higher for the steady-state MRA compared to first-pass MRA for both external iliac (1.24 vs. 0.80 mm(-1), p < 0.01) and renal transplant arteries (1.26 vs. 0.79 mm(-1), p < 0.01). CONCLUSION Steady-state MRA using ferumoxytol improves vessel sharpness while maintaining equivalent SNR compared to conventional first-pass MRA in renal transplant patients.

Gallbladder Wall Thickening

W1 atitis, acute hepatitis, or severe pyelonephritis. Systemic diseases that may cause diffuse wall thickening include heart and renal failure, liver dysfunction, portal venous hypertension, and sepsis. Other causes of diffuse wall thickening include infiltrative processes, such as gallbladder carcinoma, and hyperplastic changes, as seen in adenomyomatosis, although these may also present with focal thickening. The thickness of the gallbladder wall depends on the degree of gallbladder distention; pseudothickening can occur in the postprandial state due to physiologic contraction.

Comparison of ferumoxytol‐enhanced MRA with conventional angiography for assessment of severity of transplant renal artery stenosis

To determine the accuracy of ferumoxytol‐enhanced magnetic resonance angiography (MRA) in assessing the severity of transplant renal artery stenosis (TRAS), using digital subtraction angiography (DSA) as the reference standard.

Incidentally detected misty mesentery on CT: risk of malignancy correlates with mesenteric lymph node size.

Objective To determine the natural history of incidentally detected misty mesentery on computed tomography (CT) and to correlate the risk of malignancy with size of mesenteric lymph nodes. Methods A retrospective review of all CT abdomen/pelvic examinations from January 1, 2004 through December 31, 2008 identified cases of misty mesentery. The largest mesenteric lymph node was measured, and additional areas of lymphadenopathy were identified. Follow-up was obtained by reviewing all subsequent CT examinations, clinical notes, and pathologic specimens. Patients were excluded if they had a known malignancy at the time of initial CT, CT or clinical history revealing a cause for the misty mesentery, or CT follow-up of less than 2 years. Results Thirty-seven patients with misty mesentery were included. The mean time from the original CT to the latest follow-up was 3.8 years. The largest lymph node measured less than 10 mm in 30 (81%) of 37 patients. All 30 patients demonstrated stable lymph node size, had no other regions with lymphadenopathy, and none developed malignancy. The largest lymph node was 10 mm or greater in 7 (19%) of 31 patients. Three of these patients developed non-Hodgkin lymphoma, 2 of which had other areas of lymphadenopathy. No cases of nonlymphomatous malignancy were identified. Conclusions The development of malignancy in patients with incidentally detected misty mesentery correlates with mesenteric lymph node size. Patients with misty mesentery and largest mesenteric lymph node less than 10 mm without additional areas of lymphadenopathy demonstrate a benign course, and no further follow-up may be necessary.

Technical ReportMR Angiography of Renal Transplant Vasculature with Ferumoxytol:: Comparison of High-Resolution Steady-State and First-Pass Acquisitions

RATIONALE AND OBJECTIVES This work aimed to quantify the differences in signal-to-noise ratio (SNR) and vessel sharpness between steady-state and first-pass magnetic resonance angiography (MRA) with ferumoxytol in renal transplant recipients. MATERIALS AND METHODS We performed a retrospective study of adult patients who underwent steady-state and first-pass MRA with ferumoxytol to evaluate renal transplant vasculature. SNR was calculated in the external iliac artery, and vessel sharpness was calculated in the external iliac and renal transplant arteries for both acquisitions. Data were compared using Students t test. RESULTS Fifteen patients were included (mean age 56.9 years, 10 males). The mean SNR of the external iliac artery was 42.2 (SD, 11.9) for the first-pass MRA and 41.8 (SD, 9.7) for the steady-state MRA (p = 0.92). The mean vessel sharpness was significantly higher for the steady-state MRA compared to first-pass MRA for both external iliac (1.24 vs. 0.80 mm(-1), p < 0.01) and renal transplant arteries (1.26 vs. 0.79 mm(-1), p < 0.01). CONCLUSION Steady-state MRA using ferumoxytol improves vessel sharpness while maintaining equivalent SNR compared to conventional first-pass MRA in renal transplant patients.