Purpose: The accurate localization of bifurcation points in the brain near the circle of Willis is essential for labeling cerebral arteries and detecting potential aneurysms. Studies on the development of segmentation-based landmark localization methods for cerebral angiography are lacking. This study aimed to develop and validate a method for localizing anatomical landmarks using a three-dimensional (3D) encoder-decoder deep convolutional neural network architecture. Materials and Methods: Time-of-flight magnetic resonance angiography (MRA) images of 224 subjects obtained from publicly available datasets were used. Ten anatomical landmark points were annotated, and four different landmark subset configurations were trained and validated. For each configuration, 3D U-Net-based models were developed using the MRA images and their corresponding annotated landmarks. The deep learning prediction results were evaluated in terms of landmark localization errors. Results: Among the four configurations, the configuration with five landmark subsets produced the smallest landmark localization errors in the test dataset. Post-processing of the U-Net-predicted segmentation masks further reduced the mean localization errors across all landmark points for the configuration with five subsets. Conclusion: The proposed landmark localization method effectively identified major anatomical landmarks around the circle of Willis and showed the potential to automate segmental analyses of intracranial arterial tortuosity.
Acute lymphoblastic leukemia (ALL) primarily affects the bone marrow and peripheral blood. Extramedullary manifestations, especially in the sinonasal cavity, are rare and difficult to diagnose. We report a case of B-cell ALL in a 4-year-old girl who initially presented with a sinonasal mass mimicking a primary malignant neoplasm. The patient developed right eye protrusion upon nasal blowing over a period of 2 weeks. Imaging studies revealed an aggressive-appearing mass in the right maxillary sinus with extensive local invasion. The radiologic differential diagnosis included rhabdomyosarcoma, lymphoma, and other pediatric sinonasal malignancies. Histopathologic examination of the biopsy specimen and subsequent bone marrow evaluation established the diagnosis of B-cell ALL with BCR/ABL1 fusion. This case highlights the importance of including ALL in the differential diagnosis of sinonasal masses in pediatric patients, particularly when imaging features suggest an aggressive malignancy accompanied by hematologic abnormalities. A comprehensive evaluation, including imaging studies, routine laboratory tests, tissue biopsy, and bone marrow examination, is crucial for establishing an accurate diagnosis and initiating appropriate treatment.
Purpose: To characterize the electromagnetic (EM) behavior of a monopole and dipole hybrid (MDH) antenna and evaluate its performance relative to monopole and dipole antennas for 10.5 tesla (T) magnetic resonance imaging (MRI) applications. Materials and Methods: Full-wave EM simulations were performed to model an inductor-shortened 20-cm dipole and an MDH antenna with asymmetric 9-cm and 12-cm poles. Single elements and 16-channel arrays were arranged on cylindrical formers (inner diameter 25 cm) around a tissue-mimicking phantom (epsilon r = 49, sigma = 0.6 S/m, diameter = 18 cm, height = 30 cm) with similar to 4 cm inter-element spacing and no additional decoupling circuitry. The eight-channel monopole antenna and MDH arrays were further modeled and analyzed with and without coaxial feed cables to assess cable-induced effects on magnetic (B) field distribution. Relative individual transmit field maps of the 8-channel monopole antenna and MDH arrays were acquired on a 10.5 T MRI system using a gradient echo (GRE) sequence (repetition time [TR] = 4000 ms, echo time [TE] = 3.0 ms, acquisition time [TA] = 7:48 ms, flip angle = 60 degrees, field of view [FOV] = 354 x 354 mm(3), resolution = 3.0 x 1.5 x 3.0 mm(3)). Results: The MDH antenna demonstrated enhanced longitudinal B-field concentration and improved directivity compared with the dipole antenna element. Across the 8- and 16-channel arrays, the MDH structures consistently exhibited lower coupling, reducing S-21 by up to 10 dB relative to the monopole and dipole antenna arrays. Cable attachment significantly altered the MDH field patterns, reflecting dipole-like sensitivity to common-mode currents; however, appropriate cable management preserved field stability. Conclusion: The MDH antenna provides intrinsic decoupling advantages and robust multichannel behavior without requiring additional decoupling circuitry. These characteristics make the MDH architecture a strong candidate for next-generation high-density arrays for ultra-high field MRI.
Hepatic angiomyolipoma is a rare benign tumor that often mimics hepatocellular carcinoma on imaging. Here, we report a rare case of hepatic angiomyolipoma with extensive hemorrhagic degeneration, resulting in a large hemorrhagic component that mimicked a complicated cystic neoplasm. A 43-year-old woman presented with mild abdominal distension, and imaging revealed a 16-cm multiloculated cystic mass in the left hepatic lobe. Computed tomography revealed a thick, enhancing wall and septa with hyperattenuating internal fluid. On gadoxetic acid-enhanced magnetic resonance imaging, arterial enhancement was observed along the thick wall, and a subtle opposedphase signal drop indicated a small fat component that was initially missed. Laparoscopic left lobectomy was performed under suspicion of a malignant cystic neoplasm. Histopathological examination revealed an angiomyolipoma composed of thick-walled vessels, spindle-shaped muscle bundles, and scant adipocytes, with human melanoma black 45 positivity and absence of an epithelial lining, consistent with hemorrhagic degeneration. This case highlights how hemorrhagic degeneration can pose a significant diagnostic challenge by masking the typical features of hepatic angiomyolipoma, leading to diagnostic confusion with complicated cystic tumors.
Purpose: To assess the accuracy of supraspinatus muscle fat fraction and atrophy measured on the Y-view compared with the newly proposed fossa-view sagittal MRI plane. Materials and Methods: This study included 84 patients (36 male; mean age, 65.1 +/- 10.1 years) who underwent shoulder MRI with extended oblique sagittal T1-weighted and three-dimensional (3D) six-echo Dixon imaging between December 2020 and November 2022. The reference fat fraction was calculated by integrating voxel-wise Dixon values, while supraspinatus muscle volume was quantified using a 3D nnU-Net algorithm and normalized to the scapular volume to derive the standardized muscle index (SMI). Fat fraction and cross-sectional area were quantified on the Y-view and fossaview and compared with the reference values. Subgroup analyses were performed using fatty degeneration and retraction grades. Results: Agreement with the reference fat fraction was significantly higher for the fossa-view (intraclass correlation coefficient [ICC], 0.923) than for the Y-view (ICC, 0.822; p = 0.006). The fossa-view showed smaller deviations and narrower limits of agreement. For SMI, the Y-view (ICC, 0.782) showed higher agreement than the fossa-view (ICC, 0.694), although the difference was not statistically significant (p = 0.219). Subgroup analyses showed better Y-view performance at lower retraction grades and better fossa-view performance at higher grades, although the differences were not statistically significant (all p > 0.05). Conclusion: Both planes reliably quantified the fat fraction with greater accuracy in the fossa-view. However, single-plane assessment of muscle atrophy was less reliable, underscoring the need for MRI evaluation of the entire muscle.
