k-Space Deep Learning for Parallel MRI: Application to Time-Resolved MR Angiography

Time-resolved angiography with interleaved stochastic trajectories (TWIST) has been widely used for dynamic contrast enhanced MRI (DCE-MRI). To achieve highly accelerated acquisitions, TWIST combines the periphery of the k-space data from several adjacent frames to reconstruct one temporal frame. However, this view-sharing scheme limits the true temporal resolution of TWIST. Moreover, the k-space sampling patterns have been specially designed for a specific generalized autocalibrating partial parallel acquisition (GRAPPA) factor so that it is not possible to reduce the number of view-sharing once the k-data is acquired. To address these issues, this paper proposes a novel k-space deep learning approach for parallel MRI. In particular, we have designed our neural network so that accurate k-space interpolations are performed simultaneously for multiple coils by exploiting the redundancies along the coils and images. Reconstruction results using in vivo TWIST data set confirm that the proposed method can immediately generate high-quality reconstruction results with various choices of view- sharing, allowing us to exploit the trade-off between spatial and temporal resolution in time-resolved MR angiography

Hippocampal sclerosis and encephalomalacia as prognostic factors of tuberculous meningitis-related and herpes simplex encephalitis-related epilepsy

AbstractBackgroundTuberculous meningitis (TBM) and herpes simplex encephalitis (HSE) are common neurological diseases involving the brain parenchyma, and both can result in chronic epilepsy. Here, we identified possible variables affecting the prognosis of central nervous system (CNS) infection-related epilepsy.MethodsThe clinical seizure characteristics and demographic data of 20 TBM- and 55 HSE-related epilepsy patients were compared. Statistically significant prognostic variables were identified using multiple regression analysis.ResultsSex, age at infection, age at epilepsy onset, presence of seizures at the time of infection, latency period, and seizure characteristics between two groups were similar except for the pattern of brain lesions observed on the MRI and their overall prognosis. Patients with hippocampal sclerosis (HS) only comprised 30% and 52.7% of the TBM and HSE groups, respectively. Encephalomalacia had a positive effect in the HSE group while HS had a negative effect in this group, but no significant effects were found in the TBM group. Through a multiple regression analysis with a correction for group effects, HS was associated with a poor prognosis. However, encephalomalacia was concomitantly associated with a good prognosis. In addition, a short latency period, with a one-year interval, and being male were both associated with a good prognosis, while the age at the onset of epilepsy was associated with a poor prognosis.ConclusionsThis study suggests that HS and encephalomalacia could have mutual but contradictory effects on the prognosis of CNS infection-related epilepsy

Early Recurring Hepatocellular Carcinoma after Partial Hepatic Resection: Preoperative CT Findings

OBJECTIVE: The purpose of this study was to determine the utility of preoperative CT in predicting early recurrence of hepatocellular carcinoma after partial hepatic resection. MATERIALS AND METHODS: Preoperative three-phase helical CT scans in 53 patients with hepatocellular carcinoma were retrospectively reviewed by two radiologists. In 27 patients (group I), HCC had recurred within six months, while 26 (group II) had remained disease free for at least two years. In each group, preoperative CT findings were evaluated in each group for the tumor size and number, the presence or absence of capsule, distinctness of tumor margin, perinodular extension, and the presence or absence of portal vein thrombosis. RESULTS: In group I, a tumor capsule of tumor was seen in five of 27 patients (19%), and in group II, in 16 of 26 (62%) (p =.001). The tumor margin was distinct in eight patients (30%) in group I and in 20 (77%) in group II (p =.001). Multiple tumors, perinodular extension, and portal vein thrombosis were more frequently seen in group I but the differences were not statistically significant (p >.05). Tumor size was similar in each group (p >.05). CONCLUSION: Preoperative CT findings that may help predict the early recurrence of hepatocellular carcinoma after surgical resection are an absence of capsule of tumors and an indistinct margin. Reference to these findings during preoperative CT can guide clinicians in their choice of treatment.ope

Intracranial Dural Metastasis of Ewing's Sarcoma: a Case Report

Although intracranial dural metastasis of Ewing's sarcoma is a very rare finding, its imaging characteristics are similar to those of its primary form in the central nervous system. Thus, this tumor must be considered in the differential diagnosis of extra-axial dural masses

Overlapping Ablation Using a Coaxial Radiofrequency Electrode and Multiple Cannulae System: Experimental Study in ex-Vivo Bovine Liver

Objective To assess the sizes and configurations of thermal zones after overlapping ablations using a coaxial radiofrequency (RF) electrode and multiple cannulae in ex-vivo bovine liver. Materials and Methods For ablation procedures, a coaxial RF electrode and introducer set was used. Employing real-time ultrasound guidance and overlapping techniques in explanted, fresh bovine liver, we created five kinds of thermal zones with one (n=10), two (n=8), four (n=3), and six ablation spheres (n=3). Following ablation, MR images were obtained and the dimensions of all thermal zones were measured on the longitudinal or transverse section of specimens. The shape of the composite ablation zones was evaluated using three-dimensional MR image reconstruction. Results At gross pathologic examination of ten single-ablation zones (spheres), the long-axis (transverse) and short-axis lengths of zones ranged from 3.7 to 4.4 (mean, 4.1) cm and from 3.5 to 4.0 (mean, 3.7) cm, respectively. The long-axis (transverse) and short-axis lengths of double-ablation zones (cylinders) with 23% overlap ranged from 7.0 to 7.7 (mean, 7.3) cm and from 3.0 to 3.9 (mean, 3.5) cm, respectively; those with 58% overlap ranged from 6.0 to 6.4 (mean, 6.2) cm and from 3.8 to 4.6 (mean, 4.3) cm, respectively. The long-axis (diagonal) and short-axis lengths on a transverse section of four-ablation zones (cakes) ranged from 8.5 to 9.7 (mean, 9.1) cm and from 3.0 to 4.1 (mean, 3.7) cm, respectively. Gross pathologic examination of three composite six-ablation zones (spheres) showed that the long-axis (diagonal) and short-axis lengths of zones ranged from 9.0 to 9.9 (mean, 9.4) cm and from 6.8 to 7.5 (mean, 7.2) cm, respectively. T2-weighted MR images depicted low-signal thermal zones containing multiple curvilinear and spotty regions of hyperintensity. Conclusion Using a coaxial RF electrode and multiple cannulae, together with ultrasound guidance and precise overlapping ablation techniques, we successfully created predictable thermal zones in ex-vivo bovine liver.ope