Utility of Shear Wave Elastography for Assessing Allograft Fibrosis in Renal Transplant Recipients: A Pilot Study.

OBJECTIVES: To evaluate the utility of ultrasound-based shear wave elastography (SWE) as a noninvasive method to accurately detect and potentially stage the severity of renal allograft fibrosis and assess its user reproducibility. METHODS: In this Institutional Review Board-approved, Health Insurance Portability and Accountability Act-compliant prospective study, 70 renal transplant recipients underwent an SWE evaluation of their allograft followed directly by biopsy. Two radiologists performed separate SWE measurement acquisitions and the mean, median, and standard deviation of 10 SWE measurements, obtained separately within the cortex and the medulla, were automatically computed. Each patient's SWE results were subsequently compared to their histologic fibrosis scores. The Fisher exact test and univariate logistic regression models were fit to test for associations between the presence of fibrosis (yes/no) as well as categorical SWE results based on the fibrosis severity, ranging from F0 (no fibrosis) to F3 (severe fibrosis), correlating with histologic scores according to the 2007 Banff classification system. Interobserver and intraobserver correlations were also examined. RESULTS: Our median medulla SWE values reached statistical significance (P = .04) in association with fibrosis. Furthermore, for every unit increase in the median medulla SWE measurement, the odds of fibrosis increased by approximately 20%. No statistical significance was found for mean cortical, median cortical, or mean medullary SWE values (P = .32, .37, and .06, respectively) in association with fibrosis. CONCLUSIONS: The use of SWE for assessing renal allograft fibrosis is challenging but promising. Further investigation with a larger sample size remains to validate our initial results and establish clinical relevance.

Challenges and Considerations When Using Shear Wave Elastography to Evaluate the Transplanted Kidney, With Pictorial Review.

The gold standard in evaluating renal allograft dysfunction has traditionally been renal biopsy. However, not only does biopsy come with inherent risks, the time frame from biopsy to detecting renal dysfunction is often inefficient. It is therefore advantageous to have a noninvasive, low-cost, time-saving method, such as shear wave elastography (SWE), to detect fibrosis early, to maximize immunosuppressive care. It is important to consider factors that affect tissue stiffness in the kidney, as well as the challenges incurred when using SWE in this anisotropic organ, in order to select the most appropriate patients for this exam.

Renal Cell Carcinomas: Sonographic Appearance Depending on Size and Histologic Type.

OBJECTIVES: Prior studies have demonstrated that approximately 10% of malignant renal cell carcinomas are as echogenic as angiomyolipomas on sonography. However, a recent presentation suggested that small (<1-cm) echogenic renal masses are always angiomyolipomas or other benign entities. We therefore examined our own cases of renal cell carcinoma, with corresponding sonography, to confirm that some renal cell carcinomas may also be detected as hyperechoic masses on sonography. METHODS: Institutional Review Board approval and Health Insurance Portability and Accountability Act compliance were maintained for this retrospective review of 91 pathologically proven cases of renal cell carcinoma, with corresponding sonography. Tumors were first differentiated by histologic cell type (clear cell, papillary, and chromophobe). Tumors were then stratified according to 2 size group parameters, falling into those that were 3 cm or larger and those that were smaller than 3 cm in diameter, with the less than 3-cm group further subdivided into 2 cm or smaller and greater than 2 cm. Tumor echogenicity was graded on a 5-point scale with respect to the renal parenchyma. RESULTS: Forty-six tumors (51%) were 3 cm in diameter or smaller, and most were found to be either isoechoic (35%) or mildly hyperechoic (26%) to the surrounding renal parenchyma. Of tumors smaller than 2 cm, most were either mildly hyperechoic (29%) or as hyperechoic as renal sinus fat (very hyperechoic; 29%). Tumors larger than 3 cm were found most often to be either isoechoic (49%) or mildly hyperechoic (33%), with only 4% found to be very hyperechoic. CONCLUSIONS: The sonographic appearances of renal cell carcinomas include a small population that are very hyperechoic on sonography and thus could potentially be misdiagnosed as angiomyolipomas.

Clinical and Imaging Findings in Children with Myelin Oligodendrocyte Glycoprotein Antibody Associated Disease (MOGAD): From Presentation to Relapse.

BACKGROUND AND PURPOSE: Myelin oligodendrocyte glycoprotein-antibody associated disease (MOGAD) is an increasingly recognized cause of demyelinating disease in children. The purpose of this study is to characterize the CNS imaging manifestations of pediatric MOGAD and identify clinical and imaging variables associated with relapse. MATERIALS AND METHODS: We retrospectively identified children with serum antibody-positive MOGAD evaluated at our institution between 1997 and 2020. Clinical and demographic data were collected. MRIs of the brain, orbit, and spine at presentation and relapse were reviewed for location and pattern of abnormality. RESULTS: Among 61 cases (34 girls), mean age at presentation was 7 years (IQR 4-11). At presentation, there was imaging involvement of the brain in 78.6% (44/56), optic pathway in 55.4% (31/56), and spine in 19.6% (11/56). Brain involvement was commonly in the frontal (70.5%, 31/44) and subcortical (75%, 33/44) white matter, with involvement of the thalamus and pons in 47.7% each (21/44). Optic neuritis (ON) was commonly bilateral (80.6%, 25/31) involving intraorbital segments (77.4%, 24/31). Spinal cord lesions were typically cervical (72.7%, 8/11) and multifocal (72.7%, 8/11).The imaging patterns were age-dependent; children ≤9 years more commonly demonstrated ADEM-like imaging pattern at presentation (39.4%, 13/33) and first relapse (8/23, 34.8%), while children >9 years more commonly had ON at presentation (34.8%, 8/23, P = .001) and FLAIR-hyperintense lesions in anti-MOG-associated encephalitis with seizures at first relapse (5/18, 27.8%, P = .008). CONCLUSIONS: We describe the CNS imaging findings in pediatric MOGAD. The imaging pattern is age-dependent at presentation and first relapse. Younger age at presentation is associated with longer time to relapse.

Magnetoencephalography Atlas Viewer for Dipole Localization and Viewing.

Magnetoencephalography (MEG) is a noninvasive neuroimaging technique widely recognized for epilepsy and tumor mapping. MEG clinical reporting requires a multidisciplinary team, including expert input regarding each dipole's anatomic localization. Here, we introduce a novel tool, the "Magnetoencephalography Atlas Viewer" (MAV), which streamlines this anatomical analysis. The MAV normalizes the patient's Magnetic Resonance Imaging (MRI) to the Montreal Neurological Institute (MNI) space, reverse-normalizes MNI atlases to the native MRI, identifies MEG dipole files, and matches dipoles' coordinates to their spatial location in atlas files. It offers a user-friendly and interactive graphical user interface (GUI) for displaying individual dipoles, groups, coordinates, anatomical labels, and a tri-planar MRI view of the patient with dipole overlays. It evaluated over 273 dipoles obtained in clinical epilepsy subjects. Consensus-based ground truth was established by three neuroradiologists, with a minimum agreement threshold of two. The concordance between the ground truth and MAV labeling ranged from 79% to 84%, depending on the normalization method. Higher concordance rates were observed in subjects with minimal or no structural abnormalities on the MRI, ranging from 80% to 90%. The MAV provides a straightforward MEG dipole anatomic localization method, allowing a nonspecialist to prepopulate a report, thereby facilitating and reducing the time of clinical reporting.

Renal cell carcinoma attenuation values on unenhanced CT: importance of multiple, small region-of-interest measurements.

OBJECTIVE: Since it has been suggested that benign renal cysts can be diagnosed at unenhanced CT on the basis of homogeneity and attenuations of 20 HU or less, we determined the prevalence of renal cell carcinomas (RCCs) with these characteristics using two different methods of measuring attenuation. MATERIALS AND METHODS: After IRB approval, two radiologists obtained unenhanced attenuation values of 104 RCCs (mean size 5.6 cm) using a single, large region of interest (ROI), two-thirds the size of the mass. They were then determined if the masses appeared heterogeneous. Of RCCs measuring 20 HU or less, those which appeared homogeneous were re-measured with multiple (6 or more), small (0.6 cm2 or smaller) ROIs dispersed throughout the lesion. Masses with attenuations 20 HU or less were compared to those with masses with HU greater than 20 for any differences in demographic data. RESULTS: Of 104 RCCS, 24 RCC had HU less than 20 using a large ROI. Of these, 21 appeared heterogeneous and 3 appeared homogeneous. Using multiple small ROIs, these three RCCs revealed maximum attenuation values above 20 HU (Range: 26-32 HU). A greater portion of RCCs measuring 20 HU or less using a large ROI were clear cell sub-type. There were no other differences. CONCLUSIONS: Renal cell carcinoma can measure 20 HU or less at unenhanced CT when a single large ROI is used. While most appear heterogeneous, some may appear homogeneous, but will likely reveal attenuations greater than 20 HU when multiple, small ROIs are used. This knowledge may prevent some RCCs from being misdiagnosed as cysts on unenhanced CT.

Pitfalls of Sonographic Imaging of Uterine Leiomyoma.

Leiomyomas are the most common uterine tumor and the most common cause of uterine enlargement in the nonpregnant patient. Sonography is the imaging modality of choice for the initial diagnosis and imaging workup of uterine leiomyomas and is also extremely helpful in determining the etiology of a broad range of pelvic symptoms in the female patient. Although the classic sonographic appearance of uterine leiomyomas is well established and easily recognizable, other pelvic masses may occasionally be confused with uterine leiomyomas, and the ability to distinguish between these entities is crucial in optimizing appropriate patient care. This article will review pelvic abnormalities that can be confused on ultrasound with uterine leiomyomas and potential methods that can be used to avoid these pitfalls.

Technical tips for managing difficult iliac access.

Difficult iliac artery access remains one of the limiting factors in the successful application of endovascular management of abdominal and thoracic aortic pathologies. An understanding of the scope of the problem, as well as the recognition of patient characteristics that increase the likelihood of difficult access are paramount in preoperative planning. Herein we discuss the specific challenges of aorto-iliac access as well as provide a treatment algorithm for avoiding aorto-iliac complications. Alternative access strategies and emergency bail-out procedures are discussed. A thorough understanding of the preoperative anatomy and imaging is key to successful endovascular aortic surgery.