Agenesis of the Dorsal Pancreas: Case Report and Review of Age-Related Differences in Presentation.

Agenesis of the dorsal pancreas (ADP) is a rare congenital anomaly that occurs when the body and tail of the pancreas fail to develop from the dorsal bud in utero. ADP may be discovered when evaluating conditions arising from the anomaly, such as diabetes mellitus, pancreatitis, and pancreatic insufficiency, but is more commonly found as an incidental finding. To date, fewer than 120 cases have been reported in the literature. We report a 6-year-old male who was found to have ADP on computed tomography during the investigation of abdominal pain and vomiting. We review the variable presentation, genetic mutations, and age-related differences between children and adults with this rare condition.

Liver Tumor Enhancement at Hybrid Angio-CT and Comparison With Tumor and Hepatic Parenchymal Distribution of Yttrium-90 Microspheres by Positron Emission Tomography.

This single-center retrospective study evaluated patients who underwent treatment of a primary or secondary hepatic malignancy with injection of glass or resin yttrium-90 (90Y) microspheres with a corresponding hybrid angiography-computed tomography (angio-CT) and 90Y positron emission tomography (PET). Volumetric contours were defined by three independent observers and were used to calculate relative tumoral enhancement at angio-CT. This parameter was compared with the tumor-to-normal (T/N) activity ratio predicted by technetium-99m macro-aggregated albumin (99mTc-MAA) single photon emission computed tomography (SPECT) and microsphere activity distribution by 90Y PET. A similar correlation was observed for the enhancement ratio at angio-CT with observed microsphere distribution at 90Y PET (r=0.34) to that predicted by 99mTc-MAA SPECT (r=0.32). The enhancement ratio on angio-CT performed as well as 99mTc-MAA in the prediction of 90Y PET activity distribution. The technique could not be readily applied to tumors with large areas of hypoattenuation (necrosis) on angio-CT. With refinement and further study, this technique could be used as a quantitative adjunct to standard-of-care 99mTc-MAA SPECT for dosimetry calculations and prediction of microsphere distribution to maximize tumor response and minimize hepatotoxicity.

Multidisciplinary Management of Chylothorax.

Chylothorax, the accumulation of chyle in the pleural space, is usually caused by the disruption of the thoracic duct or its tributaries. Etiologies are broadly divided into traumatic, including postsurgical, and nontraumatic, most commonly in the setting of malignancy. The management of chylothorax largely depends on the cause and includes dietary modification and drainage of the pleural space. A definitive intervention, whether surgical or a percutaneous lymphatic intervention, should be considered in patients with a persistently high volume of chylous output and in those with a prolonged leak, before complications such as malnutrition ensue. No methodologically robust clinical trials guiding management are currently available. In this article, we review the current literature and propose a stepwise, evidence-based multidisciplinary approach to the management of patients with both traumatic and nontraumatic chylothorax.

Investigating the turbulent dynamics of small-scale surface fires.

High frequency (30 Hz) two-dimensional particle image velocimetry data recorded during a field experiment exploring fire spread from point ignition in hand-spread pine needles under calm ambient wind conditions are analysed in this study. In the initial stages, as the flame spreads approximately radially away from the ignition point in the absence of a preferred wind-forcing direction, it entrains cooler ambient air into the warmer fire core, thereby experiencing a dynamic pressure resistance. The fire-front, comprising a flame that is tilted inward, is surrounded by a region of downdraft. Coherent structures describe the initial shape of the fire-front and its response to local wind shifts while also revealing possible fire-spread mechanisms. Vortex tubes originating outside the fire spiral inward and get stretched thinner at the fire-front leading to higher vorticity there. These tubes comprise circulation structures that induce a radially outward velocity close to the fuel bed, which pushes hot gases outward, thereby causing the fire to spread. Moreover, these circulation structures confirm the presence of counter-rotating vortex pairs that are known to be a key mechanism for fire spread. The axis of the vortex tubes changes its orientation alternately towards and away from the surface of the fuel bed, causing the vortex tubes to be kinked. The strong updraft observed at the location of the fire-front could potentially advect and tilt the kinked vortex tube vertically upward leading to fire-whirl formation. As the fire evolves, its perimeter disintegrates in response to flow instabilities to form smaller fire "pockets". These pockets are confined to certain points in the flow field that remain relatively fixed for a while and resemble the behavior of a chaotic system in the vicinity of an attractor. Increased magnitudes of the turbulent fluxes of horizontal momentum, computed at certain such fixed points along the fire-front, are symptomatic of irregular fire bursts and help contextualize the fire spread. Most importantly, the time-varying transport terms of the turbulent kinetic energy budget equation computed at adjacent fixed points indicate that local fires along the fire-front primarily interact via the horizontal turbulent transport term.

Interventional radiology preparedness during coronavirus disease (COVID-19) pandemic.

The COVID-19 pandemic has affected every sector of healthcare. Interventional Radiology in many instances continues to provide frontline care during this pandemic. The purpose of this article is to assist Interventional Radiologists in their preparation to face the challenges, by summarizing global experiences and guidelines. We provide a basic framework that can be used to prepare institue specific guidelines in coordination with multidisciplinary teams and hospital administration.

Sources of systematic error in proton density fat fraction (PDFF) quantification in the liver evaluated from magnitude images with different numbers of echoes.

The purpose of this work was to investigate sources of bias in magnetic resonance imaging (MRI) liver fat quantification that lead to a dependence of the proton density fat fraction (PDFF) on the number of echoes. This was a retrospective analysis of liver MRI data from 463 subjects. The magnitude signal variation with TE from spoiled gradient echo images was curve fitted to estimate the PDFF using a model that included monoexponential R2 * decay and a multi-peak fat spectrum. Additional corrections for non-exponential decay (Gaussian), bi-exponential decay, degree of fat saturation, water frequency shift and noise bias were introduced. The fitting error was minimized with respect to 463 × 3 = 1389 subject-specific parameters and seven additional parameters associated with these corrections. The effect on PDFF was analyzed, notably the dependence on the number of echoes. The effects on R2 * were also analyzed. The results showed that the inclusion of bias corrections resulted in an increase in the quality of fit (r2 ) in 427 of 463 subjects (i.e. 92.2%) and a reduction in the total fitting error (residual norm) of 43.6%. This was largely a result of the Gaussian decay (57.8% of the reduction), fat spectrum (31.0%) and biexponential decay (8.8%) terms. The inclusion of corrections was also accompanied by a decrease in the dependence of PDFF on the number of echoes. Similar analysis of R2 * showed a decrease in the dependence on the number of echoes. Comparison of PDFF with spectroscopy indicated excellent agreement before and after correction, but the latter exhibited lower bias on a Bland-Altman plot (1.35% versus 0.41%). In conclusion, correction for known and expected biases in PDFF quantification in liver reduces the fitting error, decreases the dependence on the number of echoes and increases the accuracy.

Effect of intravenous gadoxetate disodium and flip angle on hepatic proton density fat fraction estimation with six-echo, gradient-recalled-echo, magnitude-based MR imaging at 3T.

PURPOSE: The aim of the study was to determine in patients undergoing gadoxetate disodium (Gx)-enhanced MR exams whether proton density fat fraction (PDFF) estimation accuracy of magnitude-based multi-gradient-echo MRI (MRI-M) could be improved by using high flip angle (FA) on post-contrast images. MATERIALS AND METHODS: Thirty-one adults with known or suspected hepatic steatosis undergoing 3T clinical Gx-enhanced liver MRI were enrolled prospectively. MR spectroscopy (MRS), the reference standard, was performed before Gx to measure MRS-PDFF. Low (10°)- and high (50°)-flip angle (FA) MRI-M sequences were acquired before and during the hepatobiliary phase after Gx administration; MRI-PDFF was estimated in the MRS-PDFF voxel location. Linear regression parameters (slope, intercept, average bias, R 2) were calculated for MRS-PDFF as a function of MRI-PDFF for each MRI-M sequence (pre-Gx low-FA, pre-Gx high-FA, post-Gx low-FA, post-Gx high-FA) for all patients and for patients with MRS-PDFF <10%. Regression parameters were compared (Bonferroni-adjusted bootstrap-based tests). RESULTS: Three of the four MRI-M sequences (pre-Gx low-FA, post-Gx low-FA, post-Gx high-FA) provided relatively unbiased PDFF estimates overall and in the low-PDFF range, with regression slopes close to 1 and intercepts and biases close to zero. Pre-Gx high-FA MRI overestimated PDFF in proportion to MRS-PDFF, with slopes of 0.72 (overall) and 0.63 (low-PDFF range). Based on regression bias closest to 0, the post-Gx high-FA sequence was the most accurate overall and in the low-PDFF range. This sequence provided statistically significant improvements in at least two regression parameters compared to every other sequence. CONCLUSION: In patients undergoing Gx-enhanced MR exams, PDFF estimation accuracy of MRI-M can be improved by using high-FA on post-contrast images.

Accuracy and the effect of possible subject-based confounders of magnitude-based MRI for estimating hepatic proton density fat fraction in adults, using MR spectroscopy as reference.

PURPOSE: To determine the accuracy and the effect of possible subject-based confounders of magnitude-based magnetic resonance imaging (MRI) for estimating hepatic proton density fat fraction (PDFF) for different numbers of echoes in adults with known or suspected nonalcoholic fatty liver disease, using MR spectroscopy (MRS) as a reference. MATERIALS AND METHODS: In this retrospective analysis of 506 adults, hepatic PDFF was estimated by unenhanced 3.0T MRI, using right-lobe MRS as reference. Regions of interest placed on source images and on six-echo parametric PDFF maps were colocalized to MRS voxel location. Accuracy using different numbers of echoes was assessed by regression and Bland-Altman analysis; slope, intercept, average bias, and R2 were calculated. The effect of age, sex, and body mass index (BMI) on hepatic PDFF accuracy was investigated using multivariate linear regression analyses. RESULTS: MRI closely agreed with MRS for all tested methods. For three- to six-echo methods, slope, regression intercept, average bias, and R2 were 1.01-0.99, 0.11-0.62%, 0.24-0.56%, and 0.981-0.982, respectively. Slope was closest to unity for the five-echo method. The two-echo method was least accurate, underestimating PDFF by an average of 2.93%, compared to an average of 0.23-0.69% for the other methods. Statistically significant but clinically nonmeaningful effects on PDFF error were found for subject BMI (P range: 0.0016 to 0.0783), male sex (P range: 0.015 to 0.037), and no statistically significant effect was found for subject age (P range: 0.18-0.24). CONCLUSION: Hepatic magnitude-based MRI PDFF estimates using three, four, five, and six echoes, and six-echo parametric maps are accurate compared to reference MRS values, and that accuracy is not meaningfully confounded by age, sex, or BMI.

Accuracy of MR imaging-estimated proton density fat fraction for classification of dichotomized histologic steatosis grades in nonalcoholic fatty liver disease.

PURPOSE: To evaluate the diagnostic performance of previously proposed high-specificity magnetic resonance (MR) imaging-estimated proton density fat fraction (PDFF) thresholds for diagnosis of steatosis grade 1 or higher (PDFF threshold of 6.4%), grade 2 or higher (PDFF threshold of 17.4%), and grade 3 (PDFF threshold of 22.1%) by using histologic findings as a reference in an independent cohort of adults known to have or suspected of having nonalcoholic fatty liver disease (NAFLD). MATERIALS AND METHODS: This prospective, cross-sectional, institutional review board-approved, HIPAA-compliant single-center study was conducted in an independent cohort of 89 adults known to have or suspected of having NAFLD who underwent contemporaneous liver biopsy. MR imaging PDFF was estimated at 3 T by using magnitude-based low-flip-angle multiecho gradient-recalled-echo imaging with T2* correction and multipeak modeling. Steatosis was graded histologically (grades 0, 1, 2, and 3, according to the Nonalcoholic Steatohepatitis Clinical Research Network scoring system). Sensitivity, specificity, and binomial confidence intervals were calculated for the proposed MR imaging PDFF thresholds. RESULTS: The proposed MR imaging PDFF threshold of 6.4% to diagnose grade 1 or higher steatosis had 86% sensitivity (71 of 83 patients; 95% confidence interval [CI]: 76, 92) and 83% specificity (five of six patients; 95% CI: 36, 100). The threshold of 17.4% to diagnose grade 2 or higher steatosis had 64% sensitivity (28 of 44 patients; 95% CI: 48, 78) and 96% specificity (43 of 45 patients; 95% CI: 85, 100). The threshold of 22.1% to diagnose grade 3 steatosis had 71% sensitivity (10 of 14 patients; 95% CI: 42, 92) and 92% specificity (69 of 75 patients; 95% CI: 83, 97). CONCLUSION: In an independent cohort of adults known to have or suspected of having NAFLD, the previously proposed MR imaging PDFF thresholds provided moderate to high sensitivity and high specificity for diagnosis of grade 1 or higher, grade 2 or higher, and grade 3 steatosis. Prospective multicenter studies are now needed to further validate these high-specificity thresholds.

Magnetic Resonance-guided Focused Ultrasound Treatment for Uterine Fibroids: First Study in Indian Women.

OBJECTIVES: To study the results of magnetic resonance-guided focused ultrasound surgery (MRgFUS) treatment carried out on Indian patients in our Hospital. MATERIALS AND METHODS: Fifty Indian women (mean age = 36.2 ± 8.3 years) were treated for fibroids as outpatients using the ExAblate MRgFUS system (InSightec). Non-perfused volumes (NPVs) were measured immediately after treatment to calculate the treatment outcomes. A validated symptom-specific questionnaire to record their symptoms prior to treatment and six months following treatment was completed by patients. The size of the fibroids was measured on the day of the treatment and during the 6-month checkup to calculate shrinkage. Adverse events during and following treatment were recorded and monitored. RESULTS: The average NPV ratio measured after the treatment was 88% ± 6%, indicative of high ablated fibroid tissue. Prior to treatment, the mean Symptoms Severity Score was 56.9 ± 4.8 (n = 50), which is indicative of highly symptomatic patients. Six months following treatment, there was an average fibroid shrinkage of 30% ± 11%, and a significant decrease in the mean score to 28.6 ± 6.0 (n = 50) (P < 0.001). There were no reports of serious or unexpected adverse events at any point during treatment or during the follow-up period from any of the 50 women treated in the current study. CONCLUSIONS: The current results obtained after 6 months of treatment corroborated previous data on the safety and efficacy of MRgFUS for treating uterine fibroids. This is the first publication that provides such data for a large cohort of Indian women.