Spatial distribution of MRI-Determined hepatic proton density fat fraction in adults with nonalcoholic fatty liver disease.

PURPOSE: To describe the spatial distribution of liver fat,using MRI-estimated proton density fat fraction (PDFF), in adults with nonalcoholic fatty liver disease (NAFLD). MATERIALS AND METHODS: This Investigational Review Board-approved, Health Insurance Portability and Accountability Act-compliant study prospectively enrolled 50 adults (30 women, 20 men) with biopsy-proven NAFLD. Hepatic PDFF was measured by low-flip-angle multiecho spoiled gradient-recalled-echo MRI at 3 Tesla. Three nonoverlapping regions of interest were placed within each liver segment. Statistical analyses included Pearson's correlation, multivariable linear regression, and permutation-based paired tests. RESULTS: The study population's mean whole-liver PDFF was 16.1% (range: 1.6­39.6%). The mean whole-liver PDFF variability was 1.9% (range: 0.7­4.5%). Higher variability was associated with higher PDFF (r=0.34;P=0.0156). The mean PDFF was significantly higher in the right lobe than the left (16.5% versus 15.3%, P=0.0028). The mean PDFF variability was higher in the left lobe than the right (1.86% versus 1.28%; P<0.0001). Segment II had the lowest mean segmental PDFF (14.8%);segment VIII had the highest (16.7%). Segments V(0.71%) and VI (0.70%) had the lowest mean segmental PDFF variability; segment II had the highest (1.32%). CONCLUSION: IN adult NAFLD there are small but significant differences in fat content.

Implicit screening of abdominal aortic aneurysms among veterans using lumbar spine MRI.

BACKGROUND: Early detection of abdominal aortic aneurysms (AAAs) is critical given the high morbidity and mortality of a ruptured aneurysm. Screening ultrasound is recommended for men 65 and 75 years of age with a smoking history. However, studies have shown that the rate of ultrasound screening is low and that implicit AAA screening by abdominal imaging studies that were not originally intended for AAA screening can play a major role in AAA detection. OBJECTIVE: The main objective was to evaluate the role of lumbar spine MRIs as an implicit AAA screening study by assessing the detection rate of AAAs in a broader cohort of veterans that included screening and non-screening populations. METHODS: 4085 consecutive lumbar spine MRIs from our institution between 2/2020 and 9/2023 were retrospectively reviewed. Each study was labeled AAA present, AAA not present, or indeterminate by radiologists. The correlation between the presence of AAAs and cardiovascular risk factors was assessed using multinomial logistic regression. RESULTS: AAAs were present in 89 studies (2.2 %) from 80 patients (mean age 75.8 (56-93), M:F 10:0) and absent in 3935 cases (96.3 %) from 3310 patients (mean age 61.7 (19-100), M:F 9:1). Indeterminate cases (n = 61, 1.5 %) were mainly due to incomplete visualization (70.5 %). Mean AAA size was 3.6 cm with most AAAs (n = 43) smaller than 3.5 cm. Sixteen AAAs were 3.5-3.9 cm, 16 between 4 and 4.9cm, and 6 between 5 and 5.9 cm. Artifact precluded measurements in 8 cases. Among the AAA-positive cases, 20 had no prior documentation of AAA. Twenty-one patients with AAAs would not have met the criteria for the routine AAA screening ultrasound. Higher rates of hypertension, hyperlipidemia, and smoking were observed for the AAA cohort at 78.8 % (OR 2.037, CI 1.160-3.576, P = .013), 82.5 % (2.808, 1.543-5.110, P < .001), and 75 % (3.340, 1.979-5.638, P < .001), respectively, compared to the matched no-AAA cohort (58.2 %, 57.6 %, and 50.8 %; n = 2055). CONCLUSION: Lumbar spine MRI is a valid modality for implicit screening of AAAs. CLINICAL IMPACT: Those interpreting lumbar spine MRIs should be vigilant about assessing for AAAs, especially in men with a history of hypertension, hyperlipidemia, or tobacco smoking.

Reproducibility of hepatic fat fraction measurement by magnetic resonance imaging.

PURPOSE: To evaluate the reproducibility of magnetic resonance imaging (MRI)-determined hepatic fat fraction (%) across imaging sites with different magnet types and field strength. Reproducibility among MRI platforms is unclear, even though evaluating hepatic fat fractions (FFs) using MRI-based methods is accurate against MR spectroscopy. MATERIALS AND METHODS: Overweight subjects were recruited to undergo eight MRI examinations at five imaging centers with a range of magnet manufacturers and field strengths (1.5 and 3 T). FFs were estimated in liver and in fat-emulsion phantoms using three methods: 1) dual-echo images without correction (nominally out-of-phase [OP] and in-phase [IP]); 2) dual-dual-echo images (two sequences) with T2* correction (nominally OP/IP and IP/IP); and 3) six-echo images with spectral model and T2* correction, at sequential alternating OP and IP echo times (Methods 1, 2, and 3, respectively). RESULTS: Ten subjects were recruited. For Methods 1, 2, and 3, respectively, hepatic FF ranged from -2.5 to 27.0, 1.9 to 29.6, and 1.3 to 34.4%. Intraclass correlation coefficients were 0.85, 0.89, and 0.91 for each method, and within-subject coefficients of variation were 18.5, 9.9, and 10.3%, respectively. Mean phantom FFs derived by Methods 2 and 3 were comparable to the known FF for each phantom. Method 1 underestimated phantom FF. CONCLUSION: Methods 2 and 3 accurately assess FF. Strong reproducibility across magnet type and strength render them suitable for use in multicenter trials and longitudinal assessments.

Diagnostic Challenges in Primary Sacral Tumors and the Yield of Computed Tomography-Guided Needle Biopsy in the Modern Era.

OBJECTIVE: Primary sacral tumors pose unique challenges because of their complex radiographic appearances, diverse pathologic entities, and dramatically different treatment paradigms based on tumor type. Magnetic resonance imaging and computed tomography (CT) can provide valuable information; however, sacral lesions can possess unique radiographic features and pose diagnostic dilemmas. CT-guided percutaneous needle biopsy is a critical component of the diagnostic workup. However, limited data are available on its efficacy for primary sacral tumors. METHODS: The data from patients with newly diagnosed primary sacral lesions during a 12-year period at our hospital were analyzed. The preoperative magnetic resonance imaging findings, biopsy results, and pathological data for patients who required surgery were analyzed. Unique cases in which the final pathologic result was unexpected from the preoperative imaging findings have been highlighted. RESULTS: Of 38 patients who underwent percutaneous needle biopsy, diagnostic tissue was obtained on the first attempt for 31 (82%). Five of the remaining 7 obtained diagnostic tissue on the second attempt, yielding 95% diagnosis, with only two requiring open biopsies. In 2 patients with diagnostic tissue on CT-guided biopsy, an open biopsy was still recommended because of the clinical scenario. In both patients, the open biopsy results matched those of the CT-guided biopsy. For the 18 patients who required surgery, we found 100% correlation between the percutaneous needle biopsy findings and the final pathological diagnosis. No biopsy-induced complications or extraspinal tumor seeding occurred. CONCLUSIONS: CT-guided biopsy is a safe and effective technique. It represents a critical component of the diagnostic algorithm, given the diverse pathological findings of primary sacral lesions and dramatic differences in treatment.

Cerebral Misery Perfusion on Susceptibility Weighted Imaging in Acute Carotid Dissection.

The cerebral vasculature incorporates several fail-safes that must be breached before an irreversible ischemic event takes place. In particular, when autoregulatory vasodilatation fails secondary to falling cerebral perfusion pressure (CPP; stage I hemodynamic failure), increases in the oxygen extraction fraction work to maintain the cerebral metabolic rate of oxygen. Previously, failure of this mechanism, stage II hemodynamic failure, or misery perfusion, has been imaged via positron emission tomography/computed tomography (PET/CT). Current susceptibility-weighted sequences (SWI) allow for more efficient imaging of this physiology. In this case, we identify an incident of reversible ischemia caused by spontaneous carotid artery dissection using a combination of diffusion weighted imaging (DWI) and SWI. The level of hemodynamic failure identified by the imaging sequences elevated the urgency of neurointervention, expediting the patient's arrival to the neurointerventional table and thus avoiding impending irreversible ischemia.