Simultaneous use of Individual and Joint Regularization Terms in Compressive Sensing: Joint Reconstruction of Multi-Channel Multi-Contrast MRI Acquisitions

Purpose: A time-efficient strategy to acquire high-quality multi-contrast images is to reconstruct undersampled data with joint regularization terms that leverage common information across contrasts. However, these terms can cause leakage of uncommon features among contrasts, compromising diagnostic utility. The goal of this study is to develop a compressive sensing method for multi-channel multi-contrast magnetic resonance imaging (MRI) that optimally utilizes shared information while preventing feature leakage. Theory: Joint regularization terms group sparsity and colour total variation are used to exploit common features across images while individual sparsity and total variation are also used to prevent leakage of distinct features across contrasts. The multi-channel multi-contrast reconstruction problem is solved via a fast algorithm based on Alternating Direction Method of Multipliers. Methods: The proposed method is compared against using only individual and only joint regularization terms in reconstruction. Comparisons were performed on single-channel simulated and multi-channel in-vivo datasets in terms of reconstruction quality and neuroradiologist reader scores. Results: The proposed method demonstrates rapid convergence and improved image quality for both simulated and in-vivo datasets. Furthermore, while reconstructions that solely use joint regularization terms are prone to leakage-of-features, the proposed method reliably avoids leakage via simultaneous use of joint and individual terms. Conclusion: The proposed compressive sensing method performs fast reconstruction of multi-channel multi-contrast MRI data with improved image quality. It offers reliability against feature leakage in joint reconstructions, thereby holding great promise for clinical use.Comment: 13 pages, 13 figures. Submitted for possible publicatio

Increased ocular wall thickness and decreased globe volume in children with mucopolysaccharidosis type VI

PURPOSElthough clinical ophthalmologic findings have been reported, no study documented magnetic resonance imaging (MRI) findings in mucopolysaccharidosis (MPS) type VI. The aim of this study was to determine the ophthalmologic imaging findings of MPS type VI in the pediatric age group retrospectively.METHODSBrain MRIs of 10 patients with MPS type VI and 49 healthy children were evaluated independently by two pediatric radiologists for the following characteristics: globe volume, ocular wall thickness, and optic nerve sheath diameter for each orbit. The means of the measurement of each group were compared by using an independent t-test. Agreement and bias between reviewers were assessed by intra-class correlation coefficients (ICC).RESULTSA total of 59 children [32 girls (54.23%), 27 boys (45.77%); age range, 4-16 years; mean age, 10.37 ± 3.73 years] were included in the study. Statistical analysis revealed smaller eyeballs and thicker ocular walls of patients with MPS type VI (P < .001 and P < .001, respectively). However, there was no statistically significant difference in terms of optic nerve sheath diameter between the two groups (P=.648).CONCLUSIONPatients with MPS type VI displayed reduced globe volumes and increased ocular wall thicknesses compared to the healthy children. Therefore, we recommend that ophthalmologic imaging findings might prove to be an auxiliary tool in the diagnosis of MPS patients

CT dose management for neurologic events in patients with cardiac devices: Radiation exposure variation in patients with cardiac devices

PURPOSE:To compare the inter-center cranial computed tomography (CT) acquisition rates, CT findings, CT related radiation dose, and variability of CT acquisition parameters for neurologic events among patients with implantable cardioverter-defibrillator (ICD) or left ventricular assist device (LVAD).METHODS:A total of 224 patients [ICD group (n = 155) and LVAD group (n = 69)] who had at least one cranial CT scan were enrolled from three medical centers. The variability and effect of the number, indication, and findings of cranial CT scans as well as CT acquisition parameters including tube potential, tube current, tube rotation time (TI), slice collimation (cSL), and spiral or sequential scanning techniques on CT dose index volume (CTDIvol), total dose length product (DLP) were analyzed.RESULTS:The mean DLP value of Center A and mean CTDIvol values of Center A and C were significantly lower than Center B (p < 0.001). The mean CTDIvol and DLP values in the ICD group were substantially lower than the LVAD group (p<0.001). The most potent parameters causing the changes in CTDIvol and DLP were kV, mAs values, and CT scanning technique as sequential or spiral according to multivariate linear regression analysis.CONCLUSION:Cranial CT acquisition parameters and radiation doses vary significantly between centers, which necessitates optimization of cranial CT protocols to overcome the cumulative radiation dose burden in patients with neurologic events

Pharmacoresistant seizures in neurofibromatosis type 1 related to hippocampal sclerosis: Three case presentation and review

Neurofibromatosis type 1 (NF1) is an autosomal dominantly inherited disorder, with an estimated prevalence of 1 in 3000-4000 people. Seizures occur 4-7% of individuals with NF1, mostly due to associated brain tumors or cortical malformations. Hippocampal sclerosis (HS) in the patients with NF1 has been reported very rarely and only 15 patients were found in review of English literature. We presented here 3 additional patients with NF1 and intractable seizures due to hippocampal sclerosis; in whom one of them underwent epilepsy surgery and he is seizure free for 5 years after right temporal lobectomy.Wo

Predictive Factors for Postoperative Outcome in Temporal Lobe Epilepsy According to Two Different Classifications

Purpose: The determination of prognostic factors is important for predicting outcome after epilepsy surgery. We investigated the factors related to surgical outcome within a homogeneous group of patients suffering from pathologically proven mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS), and compared Engel's outcome classification system with the latest one proposed by the ILAE. Method: We included 109 patients with MTLE-HS who were followed-up for at least 1 year after epilepsy surgery. A retrospective chart review was performed to extract patients' demographic details, and potential pre- postoperative risk factors. Outcome of surgery was defined by the Engel's and ILAE classifications. In addition, the course of prognosis was determined according to the changes in ILAE classifications on an annual basis. Univariate and multivariate logistic regression analyses were used for the latest available outcomes and two different courses of prognosis. Results: The average duration of follow up was 4.78 +/- 2.55 years in the 109 patients with MTLE-HS. The univariate and multiple logistic regression analyses showed that the occurrence of seizures during the first month after surgery was a significant risk factor for a poor outcome. A history of trauma was also significant for patients with late recurrence of postsurgical seizures after at least 1-year seizure remission. Conclusion: The occurrence of seizures during the first month after surgery is a significant prognostic factor in patients with MTLE-HS. Ignoring early postoperative seizures in classification systems may result in difficulty in identifying the course of epilepsy after surgery. (C) 2008 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.WoSScopu

Assessment of the Effect of Cigarette Smoking on Regional Brain Volumes and Lesion Load in Patients with Clinically Isolated Syndrome

Purpose: Smoking has been associated with an increased risk of developing multiple sclerosis, disease progression and clinical disability. We detected the effects of smoking on regional brain volumes and lesion load in patients with clinically isolated syndrome using quantitative magnetic resonance imaging. Materials and Methods: Smoker patients (n = 16), smoker healthy controls (n = 13), non-smoker patients (n = 17) and non-smoker healthy controls (n = 14) underwent magnetic resonance imaging and neocortical volumes were measured. Lesion load was calculated in terms of number and volume of white matter hyperintensities. Results: Smoking was associated with increased gray matter volumes in several regions of the brain. A tendency towards greater lesion load in smoker patients was found. Smoking duration was significantly negatively correlated with intracranial volume and left hemisphere cortical gray matter volume. There was no relationship between regional brain volumes and clinical disability scores, lesion load duration of the disease and degree of smoking exposure. Conclusions: Clinically isolated syndrome related regional brain atrophy might vary in extent and severity with smoking. Despite increased lesion load, less cortical and deep gray matter damage with a possible neuroprotective effect occurs in smoking.Wo

Ischemic Stroke Phenotype in Patients with Nonsustained Atrial Fibrillation

Background and Purpose-The widespread use of ambulatory cardiac monitoring has not only increased the detection of high-risk arrhythmias like persistent and paroxysmal atrial fibrillation (AF), but also made it possible to identify other aberrations such as short-lasting (<30 seconds) irregular runs of supraventricular tachycardia. Ischemic stroke phenotype might be helpful in understanding whether these nonsustained episodes play a similar role in stroke pathophysiology like their persistent and paroxysmal counterparts. Methods-In a consecutive series of patients with ischemic stroke, we retrospectively determined clinical and imaging features associated with nonsustained AF (n=126), defined as <30-second-lasting supraventricular tachyarrhythmias with irregular RR interval on 24-hour Holter monitoring, and compared them to patients with persistent/paroxysmal AF (n=239) and no AF (n=246). Results-Patients with persistent/paroxysmal AF significantly differed from patients with nonsustained AF by a higher prevalence of female sex (odds ratio [95% confidence interval], 1.8 [1.1-2.9]), coronary artery disease (1.9 [1.1-3.0]), and embolic imaging features (2.7 [1.1-6.5]), and lower frequency of smoking (0.4 [0.2-0.8]) and hyperlipidemia (0.5 [0.3-0.8]). In contrast, patients with no AF were younger (0.5 [0.4-0.6] per decade) and more likely to be male (1.7 [1.0-2.8]) in comparison with nonsustained AF population. The prevalence of nonsustained AF was similar among cryptogenic and noncryptogenic stroke patients (32% versus 29%). Voxel-wise comparison of lesion probability maps revealed no significant difference between cryptogenic stroke patients with and without nonsustained AF. Conclusions-Clinical features of patients with nonsustained AF exhibited an intermediary phenotype in between patients with persistent/paroxysmal AF and no AF. Furthermore, imaging features did not entirely resemble patterns observed in patients with longer durations of AF.WoSScopu