Using deep learning convolutional neural networks to automatically perform cerebral aqueduct CSF flow analysis.

Since the development of phase-contrast magnetic resonance imaging (PC-MRI), quantification of cerebrospinal fluid (CSF) flow across the cerebral aqueduct has been utilized for diagnosis of conditions such as normal pressure hydrocephalus (NPH). This study aims to develop an automated method of aqueduct CSF flow analysis using convolution neural networks (CNNs), which can replace the current standard involving manual segmentation of aqueduct region of interest (ROI). Retrospective analysis was performed on 333 patients who underwent PC-MRI, totaling 353 imaging studies. Aqueduct flow measurements using manual ROI placement was performed independently by two radiologists. Two types of CNNs, MultiResUNet and UNet, were trained using ROI data from the senior radiologist, with PC-MRI studies being randomly divided into training (80%) and validation (20%) datasets. Segmentation performance was assessed using Dice similarity coefficient (DSC), and CSF flow parameters were calculated from both manual and CNN-derived ROIs. MultiResUNet, UNet and second radiologist (Rater 2) had DSCs of 0.933, 0.928, and 0.867, respectively, with p < 0.001 between CNNs and Rater 2. Comparison of CSF flow parameters showed excellent intraclass correlation coefficients (ICCs) for MultiResUNet, with lowest correlation being 0.67. For UNet, lower ICCs of -0.01 to 0.56 were observed. Only 3/353 (0.8%) studies failed to have appropriate ROIs placed by MultiResUNet, compared to 12/353 (3.4%) failed cases for UNet. In conclusion, CNNs were able to measure aqueductal CSF flow with similar performance to a senior neuroradiologist. MultiResUNet demonstrated fewer cases of segmentation failure and more consistent flow measurements compared to the widely adopted UNet.

Comparison of Multispectral Image-Processing Methods for Brain Tissue Classification in BrainWeb Synthetic Data and Real MR Images.

Accurate quantification of brain tissue is a fundamental and challenging task in neuroimaging. Over the past two decades, statistical parametric mapping (SPM) and FMRIB's Automated Segmentation Tool (FAST) have been widely used to estimate gray matter (GM) and white matter (WM) volumes. However, they cannot reliably estimate cerebrospinal fluid (CSF) volumes. To address this problem, we developed the TRIO algorithm (TRIOA), a new magnetic resonance (MR) multispectral classification method. SPM8, SPM12, FAST, and the TRIOA were evaluated using the BrainWeb database and real magnetic resonance imaging (MRI) data. In this paper, the MR brain images of 140 healthy volunteers (51.5 ± 15.8 y/o) were obtained using a whole-body 1.5 T MRI system (Aera, Siemens, Erlangen, Germany). Before classification, several preprocessing steps were performed, including skull stripping and motion and inhomogeneity correction. After extensive experimentation, the TRIOA was shown to be more effective than SPM and FAST. For real data, all test methods revealed that the participants aged 20-83 years exhibited an age-associated decline in GM and WM volume fractions. However, for CSF volume estimation, SPM8-s and SPM12-m both produced different results, which were also different compared with those obtained by FAST and the TRIOA. Furthermore, the TRIOA performed consistently better than both SPM and FAST for GM, WM, and CSF volume estimation. Compared with SPM and FAST, the proposed TRIOA showed more advantages by providing more accurate MR brain tissue classification and volume measurements, specifically in CSF volume estimation.

Novel Automated Method for the Detection of White Matter Hyperintensities in Brain Multispectral MR Images.

BACKGROUND: According to the Standards for Reporting Vascular Changes on Neuroimaging, White Matter Hyperintensities (WMHs) are cerebral white matter lesions that are characterized by abnormal tissues of variable sizes and appear hyperintense in T2-weighted Magnetic Resonance (MR) measurements without cavitation (i.e., their tissue signals differ from those of Cerebrospinal Fluid or CSF). Such abnormal tissue regions are typically observed in the MR images of brains of healthy older adults and are associated with a number of geriatric neurodegenerative diseases. Explanations of the exact causes and mechanisms of these diseases remain inconclusive. Moreover, WMHs are typically identified by visual assessment and manual examination, both of which require considerable time. This brings up a need of developing a method for detecting WMHs more objectively and enabling patients to be treated early. As a consequence, damages on nerve cells can be limited and the severity of patients' conditions can be contained. AIMS: This paper presents a computer-aided technique for automatically detecting and segmenting anomalies in MR images. METHODS: The method has two steps: (1) a Band Expansion Process (BEP) to expand the dimensions of brain MR images nonlinearly and (2) anomaly detection algorithms to detect WMHs. Synthesized MR images provided by BrainWeb were used as benchmarks against which the detection performance of the algorithms was determined. RESULTS: The most notable findings are as follows: Firstly, compared with the other anomaly detection algorithms and the Lesion Segmentation Tool (LST), BEP-anomaly detection is shown to be the most effective in detecting WMHs. Secondly, across all levels of background noise and inhomogeneity, the mean Similarity Index (SI) produced by our proposed algorithm is higher than that produced by LST, indicating that the algorithm is more effective than LST in segmenting WMHs from brain MR images. CONCLUSION: Experimental results demonstrated a significantly high accuracy of the BEP-K/R-RX method in detection of synthetic brain MS lesion data. In the meantime, it also effectively enhances the detection of brain lesions.

Outcome analysis in 270 radiologically guided implantations of totally implantable venous access ports via basilic vein.

BACKGROUND: Totally implantable venous access ports (TIVAPs) are widely applied in patients who require chemotherapy, parenteral nutrition, or frequent intravenous drug infusion. Although various venous access routes are possible for TIVAP insertion, the best method remains a topic of controversy. We present a single-center retrospective study of radiologically guided placement of TIVAPs through the basilic vein, with analysis of technical feasibility, patient safety, and device-related complications. METHODS: We retrospectively reviewed 270 patients who received TIVAP implantation through the basilic vein from November 2013 to July 2016, under imaging guidance by an interventional radiology team at our institution. Fluoroscopic images, chest radiographs, computed tomography scans, and medical records were reviewed after port implantation. Catheter maintenance days were calculated and catheter-related complications were recorded. RESULTS: The procedural success rate was 99.3%. In total, 270 TIVAPs were implanted in 270 patients, of which 150 remained functional at the end of the study period. The total catheter maintenance days was 77 543 days, and the mean catheter indwelling duration was 287 ± 207 days. In 20 (7.4%) patients, TIVAP-related complications occurred during the follow-up period, resulting in a postprocedural complication rate of 0.26 incidences per 1000 catheter days. No significant relationship was observed between complications and gender (p = 0.188), age (p = 0.528), body mass index (p = 0.547), the type of primary malignancy (p = 0.914), or between the left and right basilic veins (p = 0.319). CONCLUSION: Real-time ultrasound and fluoroscopic guidance provides a safe method for TIVAP implantation through the basilic vein, with a high technical success rate and few device-related complications.

Trends in computed tomography scan uses in Taiwan from 2000 to 2013.

BACKGROUND: The trends in computed tomography (CT) scan uses in Taiwan were examined in different age and sex groups and compared between catastrophic illness and noncatastrophic illness groups. METHODS: This retrospective cohort study used data from the National Health Insurance Research Database (NHIRD) in Taiwan to analyze CT scan uses from the beginning of 2000 to the end of 2013. The number, annual growth rate, and cumulative fold change ratio were estimated in different groups classified by sex, age, or disease category (catastrophic illness, noncatastrophic illness). RESULTS: The number of CT scan uses per million people per year in Taiwan increased 2.5 times from 24 257 in 2000 to 60 351 in 2013, at the average annual growth rate of 7.4% ± 5.9%. The annual number of CT scan uses in different age groups and disease category groups was significantly higher in males than in females. However, the average annual growth rate and the cumulative fold change ratio were slightly higher in females than in males. The majority of CT scan uses were in middle age and young adult groups. The annual number of CT scan uses in the young adult, child/adolescent, and middle age groups increased 3.7-, 3.5-, and 2.7-fold from 2000 to 2013, but decreased 0.8-fold in the old-age group. The annual number of CT scan uses was highest in the noncatastrophic illness group, followed by the catastrophic illness cancer group and catastrophic illness others group. CONCLUSION: CT scan uses in Taiwan increased continuously from 2000 to 2013, even in the groups with higher radiation-related cancer risk. Therefore, clinicians, radiologists, and medical policy makers should weigh diagnostic benefit against sex-specific and age-specific risks in the future.

Breast Tumor Detection and Classification Using Intravoxel Incoherent Motion Hyperspectral Imaging Techniques.

Breast cancer is a main cause of disease and death for women globally. Because of the limitations of traditional mammography and ultrasonography, magnetic resonance imaging (MRI) has gradually become an important radiological method for breast cancer assessment over the past decades. MRI is free of the problems related to radiation exposure and provides excellent image resolution and contrast. However, a disadvantage is the injection of contrast agent, which is toxic for some patients (such as patients with chronic renal disease or pregnant and lactating women). Recent findings of gadolinium deposits in the brain are also a concern. To address these issues, this paper develops an intravoxel incoherent motion- (IVIM-) MRI-based histogram analysis approach, which takes advantage of several hyperspectral techniques, such as the band expansion process (BEP), to expand a multispectral image to hyperspectral images and create an automatic target generation process (ATGP). After automatically finding suspected targets, further detection was attained by using kernel constrained energy minimization (KCEM). A decision tree and histogram analysis were applied to classify breast tissue via quantitative analysis for detected lesions, which were used to distinguish between three categories of breast tissue: malignant tumors (i.e., central and peripheral zone), cysts, and normal breast tissues. The experimental results demonstrated that the proposed IVIM-MRI-based histogram analysis approach can effectively differentiate between these three breast tissue types.

Investigation of chemotherapy-induced brain structural alterations in breast cancer patients with generalized q-sampling MRI and graph theoretical analysis.

BACKGROUND: Breast neoplasms are the most common cancer among women in Taiwan. Cognitive deficits are common complications of breast cancer survivors treated with chemotherapy. The most frequently observed disorders involve executive function and memory impairment. With improvements in tumor intervention and the consequent increase in the number of cancer survivors, the quality of life of patients has become an important issue. We are interested in the early effects of chemotherapy on the brain structures of patients. In addition, generalized q-sampling imaging (GQI), a wide range of q-space datasets for a more accurate and sophisticated diffusion MR approach, was first used in this topic. METHODS: As diffusion tensor imaging (DTI) is associated with restrictions in the resolution of crossing fibers, we attempted to use GQI, which can overcome these difficulties and is advantageous over DTI for tractography of the crossing fibers. This cross-sectional study included two groups: breast cancer survivors who had completed their chemotherapy (n = 19) and healthy controls (n = 20). All participants underwent diffusion MRI exams and neuropsychological assessments. We included four parts in our image analysis, i.e., voxel-based statistical analysis, multiple regression analysis, graph theoretical analysis and network-based statistical analysis. RESULTS: The results from the voxel-based statistical analysis showed significantly lower GFA and NQA values in the breast cancer group than those in the control group. We found significant positive correlations between the FACT-Cog and GQI indices. In the graph theoretical analysis, the breast cancer group demonstrated significantly longer characteristic path length. Adjuvant chemotherapy affected the integrity of white matter and resulted in poor cognitive performance, as indicated by the correlations between the neuropsychological assessment scales and the GQI indices. In addition, it was found that the characteristic path lengths in the breast cancer group increased, indicating that the brain network integration became worse. CONCLUSIONS: Our study demonstrated alterations in structural brain networks and associated neuropsychological deficits among breast cancer survivors.

Adult-to-adult living donor liver transplantation preoperative survey using MDCT, a single medical center experience in Taiwan.

This study evaluated multi-detector computed tomography (MDCT) scans performed on potential living donors for adult-to-adult liver transplantation (LDLT), with the aim of identifying significant findings that could be used to exclude potential transplantation donors. We retrospectively reviewed the medical records of 151 consecutive potential adult donors for LDLT from May 2007 to January 2015. Liver parenchyma steatosis, focal hepatic mass or intraabdominal malignancy, vascular variations, and donor liver volume were evaluated via MDCT. Grounds for excluding potential donors were also recorded and analyzed. Of the 151 potential donors, nine (6.0%) had moderate to severe fatty liver, 37 (24.5%) had hepatic arterial variants, 22 (14.6%) had significant portal venous variants, and more than half were found to have right accessory inferior hepatic vein. No intraabdominal malignancies were found. Eighty-eight potential donors were rejected, with the most common cause being insufficient recipient volume or remnant donor volume (47.7%), moderate to severe parenchymal steatosis (10.2%), and recipient expiration prior to transplantation (8.0%). An additional 16 potential donors were excluded by the surgical team due to the complexity of their portal venous variations. The rate of exclusion by pre-transplant imaging evaluation with MDCT was 33.8%. MDCT can provide accurate quantification of donor liver volume and steatosis severity along with precise demonstration of vascular variants, which are crucial for the preoperative evaluation of LDLT. However, MDCT may be ineffective for evaluating the biliary system without hepatobiliary-excreted contrast agent and has the disadvantage of ionizing radiation.

Noninvasive assessment of intracranial elastance and pressure in spontaneous intracranial hypotension by MRI.

BACKGROUND: Spontaneous intracranial hypotension (SIH) is often misdiagnosed, and can lead to severe complications. Conventional MR sequences show a limited ability to aid in this diagnosis. MR-based intracranial pressure (MR-ICP) may be able to detect changes of intracranial elastance and pressure. PURPOSE: To determine whether MR-ICP is able to differentiate SIH patients from normal subjects, improve diagnostic sensitivity, and provide an insight into the pathophysiology. STUDY TYPE: Prospective. SUBJECTS: Twenty-eight SIH cases with orthostatic headache and 20 healthy volunteers. FIELD STRENGTH/SEQUENCE: Cine phase-contrast MRI on a 1.5T scanner. ASSESSMENT: Intracranial elastance (IE) was derived from the ratio of the peak-to-peak cerebrospinal fluid (CSF) pressure gradient (PGcsf-pp ) and intracranial volume change, obtained by summing all flows before each sequential cardiac frame. STATISTICAL TESTS: Student's t-test was used to compare the MR-ICP indexes and flow parameters between SIH patients and healthy volunteers (P < 0.01). RESULTS: The SIH patients with cervical epidural venous dilatation (EVD) had an IE of 0.121 ± 0.027 mmHg/cm/ml, significantly higher than that of the normal volunteers (0.085 ± 0.027 mmHg/cm/ml; P = 0.002). In contradistinction, the EVD-negative SIH patients, including four with no sign of CSF leaks, had significantly lower IE (0.055 ± 0.012 mmHg/cm/ml) compared with the normal volunteers and the EVD-positive group (P = 0.001, P < 0.001). The EVD-negative patients had significantly lower PGcsf-pp (0.024 ± 0.007 mmHg/cm) compared with the normal volunteers and the EVD-positive group (0.035 ± 0.011 mmHg/cm, 0.040 ± 0.010 mmHg/cm; P = 0.003, P < 0.001). Additionally, the MRI flow study showed a significant decrease in transcranial inflow and outflow of SIH patients (P < 0.01). DATA CONCLUSION: We found that the MR-ICP method is potentially more sensitive than morphological MRI in the early diagnosis of SIH. Also, contrary to common belief, our results suggest that an abnormal craniospinal elastance might be the cause of SIH, instead of CSF leak. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2018;47:1255-1263.

Patient safety during radiological examinations: a nationwide survey of residency training hospitals in Taiwan.

OBJECTIVES: Variations in radiological examination procedures and patient load lead to variations in standards of care related to patient safety and healthcare quality. To understand the status of safety measures to protect patients undergoing radiological examinations at residency training hospitals in Taiwan, a follow-up survey evaluating the full spectrum of diagnostic radiology procedures was conducted. DESIGN: Questionnaires covering 12 patient safety-related themes throughout the examination procedures were mailed to the departments of diagnostic radiology with residency training programmes in 19 medical centres (with >500 beds) and 17 smaller local institutions in Taiwan. After receiving the responses, all themes in 2014 were compared between medical centres and local institutions by using χ(2) or 2-sample t-tests. PARTICIPANTS: Radiology Directors or Technology Chiefs of medical centres and local institutions in Taiwan participated in this survey by completing and returning the questionnaires. RESULTS: The response rates of medical centres and local institutions were 95% and 100%, respectively. As indicated, large medical centres carried out more frequent clinically ordered, radiologist-guided patient education to prepare patients for specific examinations (CT, 28% vs 6%; special procedures, 78% vs 44%) and incident review and analysis (89% vs 47%); however, they required significantly longer access time for MRI examinations (7.00±29.50 vs 3.50±3.50 days), had more yearly incidents of large-volume contrast-medium extravasation (2.75±1.00 vs 1.00±0.75 cases) and blank radiographs (41% vs 8%), lower monthly rates of suboptimal (but interpretable) radiographs (0.00±0.01% vs 0.64±1.84%) and high-risk reminder reporting (0.01±0.16% vs 1.00±1.75%) than local institutions. CONCLUSIONS: Our study elucidates the status of patient safety in diagnostic radiology in Taiwan, thereby providing helpful information to improve patient safety guidelines needed for medical imaging in the future.

Pulmonary hypertension and right ventricular dysfunction in patients with left to right shunt coronary artery fistula: evaluation with cardiac CT.

In this study, we aimed to evaluate whether patients with left to right shunt coronary artery fistula (LRSCAF) are predisposed to developing pulmonary hypertension and right ventricular dysfunction compared with healthy individuals. The value of cardiac CT findings in determining the necessity of intervention for these patients was investigated. We retrospectively studied 19 patients with LRSCAF and 19 healthy patients. Several parameters were observed on cardiac CT by two radiologists, including pulmonary trunk diameter (PA diameter), right ventricular diameter (RVD), left ventricular diameter (LVD), RVD/LVD ratio, septal bowing and CT score of right ventricular dysfunction (CSRVD). Data from both groups were compared. The inter- and intra-observer variabilities and correlations were examined. The disease group was further divided into intervention (n = 9) and non-intervention (n = 10) groups, and their data were compared. All cardiac CT findings showed significant intra- and inter-observer correlation without significant variability. Mann-Whitney U tests and χ(2) analysis showed that PA diameter, RVD/LVD ratio acquired from two observers, and CSRVD were higher in the disease group than in the control group (all P values < 0.05 for χ(2) and almost all P values < 0.05 for Mann-Whitney U). The RVD/LVD ratio and CSRVD were higher in the intervention group than in the non-intervention group (all P values < 0.05). Receiver operating curve analysis identified RVD/LVD = 1.036 and CSRVD = 3.5 as the best cut-off values to determine the necessity of further intervention. Patients with LRSCAF are more predisposed to pulmonary hypertension and right ventricular dysfunction compared with the normal population. RVD/LVD > 1.0 and CSRVD ≥ 4.0 may determine the necessity of intervention for patients with LRSCAF.

Time-Resolved Magnetic Resonance Angiography in the Evaluation of Intracranial Vascular Lesions and Tumors: A Pictorial Essay of Our Experience.

Time-resolved magnetic resonance angiography (TR MRA) is a promising less invasive technique for the diagnosis of intracranial vascular lesions and hypervascular tumors. Similar to 4-dimensional computed tomographic angiography obtaining high frame rate images, TR MRA utilizes acceleration techniques to acquire sequential arterial and venous phase images for identifying, localizing, and classifying vascular lesions. Because of the good agreement with digital subtraction angiography for grading brain arteriovenous malformations with the Spetzler-Martin classification and the good sensitivity for visualizing arteriovenous fistulas, studies have suggested that TR MRA could serve as a screening or routine follow-up tool for diagnosing intracranial vascular disorders. In this pictorial essay, we report on the use of TR MRA at 3.0 T to diagnose intracranial vascular lesions and hypervascular tumors, employing DSA as the reference technique.

Percutaneous Transthoracic Lung Biopsy: Comparison Between C-Arm Cone-Beam CT and Conventional CT Guidance.

BACKGROUND: C-arm cone-beam computed tomography (CBCT) is a comparatively novel modality for guiding percutaneous transthoracic lung biopsies (PTLBs), and despite its potential advantages over conventional computed tomography (CCT), a head-to-head comparison of the two techniques has yet to be reported in the literature. This study aims to evaluate the diagnostic value and safety of CBCT-guided PTLB compared to CCT-guided biopsy, with cases performed in a single hospital. METHODS: A total of 104 PTLB patients were retrospectively analyzed in this study. 35 PTLBs were performed under CBCT guidance, and 69 PTLBs were performed under CCT guidance. Diagnostic accuracy, sensitivity, and specificity for malignancy as well as procedure time, radiation dose of patients, and complication rate in the two groups were compared. RESULTS: Total procedure time was significantly lower in the CBCT group (32 ± 11 minutes) compared to the CCT group (38 ± 9.7 minutes; P = .009), especially among patients ≥70 years of age (CBCT: 33 ± 12 minutes, CCT: 42 ± 13, P = .022). For lesions in the lower lobes, the CBCT-guided group received significantly reduced effective radiation dose (2.9 ± 1.6 mSv) than CCT-guided patients (3.7 ± 0.80; P = .042). Diagnostic accuracy, sensitivity, and specificity for malignancy were comparable between the two groups, as were post-biopsy complication rates. CONCLUSION: CBCT guidance significantly reduces the procedure time and radiation exposure for PTLBs compared with CCT, and should be considered in clinical settings that may be difficult or time-consuming to perform under CCT.

Feature extraction and pattern classification of colorectal polyps in colonoscopic imaging.

A computer-aided diagnostic system for colonoscopic imaging has been developed to classify colorectal polyps by type. The modules of the proposed system include image enhancement, feature extraction, feature selection and polyp classification. Three hundred sixty-five images (214 with hyperplastic polyps and 151 with adenomatous polyps) were collected from a branch of a medical center in central Taiwan. The raw images were enhanced by the principal component transform (PCT). The features of texture analysis, spatial domain and spectral domain were extracted from the first component of the PCT. Sequential forward selection (SFS) and sequential floating forward selection (SFFS) were used to select the input feature vectors for classification. Support vector machines (SVMs) were employed to classify the colorectal polyps by type. The classification performance was measured by the Az values of the Receiver Operating Characteristic curve. For all 180 features used as input vectors, the test data set yielded Az values of 88.7%. The Az value was increased by 2.6% (from 88.7% to 91.3%) and 4.4% (from 88.7% to 93.1%) for the features selected by the SFS and the SFFS, respectively. The SFS and the SFFS reduced the dimension of the input vector by 57.2% and 73.8%, respectively. The SFFS outperformed the SFS in both the reduction of the dimension of the feature vector and the classification performance. When the colonoscopic images were visually inspected by experienced physicians, the accuracy of detecting polyps by types was around 85%. The accuracy of the SFFS with the SVM classifier reached 96%. The classification performance of the proposed system outperformed the conventional visual inspection approach. Therefore, the proposed computer-aided system could be used to improve the quality of colorectal polyp diagnosis.

Usefulness of phase-contrast magnetic resonance imaging for diagnosis and treatment evaluation in patients with SIH.

BACKGROUND: Most diagnostic tools for spontaneous intracranial hypotension (SIH) are either invasive or occasionally inconsistent with the clinical condition. In this study, we examined the cerebrospinal fluid (CSF) dynamics in SIH using phase-contrast magnetic resonance (PC-MR) imaging. MATERIALS AND METHOD: Seventeen SIH patients and 32 healthy individuals, matched by sex and age, were recruited. Each person underwent brain and PC-MR imaging using 3-Tesla MRI. We evaluated the differences in image parameters among patients during the initial and recovery stages against the status of the control group. RESULTS: SIH patients had lower CSF flow-volume, flux, peak velocity, and higher systolic-to-diastolic time ratio, as well as systolic-to-diastolic volume ratio compared to the control group and the conditions when they recovered. The flow time and volume of the diastolic phase markedly increased after treatment. The discriminating power of PC-MR for SIH was good. Diffuse pachymeningeal enhancement and venous engorgement were present when their PC-MR values were lower than the cut-off values for SIH diagnosis. The headache scores correlated with the peak velocity and pituitary volume. CONCLUSION: Noninvasive PC-MR could provide valid parameters for diagnosis and treatment follow-up in SIH patients. It may be more sensitive than conventional brain MRI.

The merit of proton magnetic resonance spectroscopy in the longitudinal assessment of spinocerebellar ataxias and multiple system atrophy-cerebellar type.

BACKGROUND: Spinocerebellar ataxia (SCA) and multiple system atrophy-cerebellar type (MSA-C) often present with similar clinical manifestations in the beginning. Magnetic resonance spectroscopy (MRS) has been proved to be a useful tool to help differentiate different types of SCA and MSA-C on cross-sectional studies. However, longitudinal changes of the MRS metabolites in these subjects have never been reported. The purpose of this study was to track the longitudinal evolution of the MRS metabolites in these patients and to ascertain the correlation between clinical severity measured by Scale of the Assessment and Rating of Ataxia (SARA) and MRS metabolites. RESULTS: Significant reductions of NAA/Cr and NAA/Cho in the cerebellar hemispheres in all patients and lower Cho/Cr in the cerebellar hemispheres in patients with SCA2 or MSA-C were found at all times. At initial assessments, patients with MSA-C or SCA2 tended to have lower NAA/Cr and Cho/Cr in the cerebellar hemispheres than those with SCA3 or SCA6. At follow-ups, patients with SCA2 or MSA-C had a lower NAA/Cr in cerebellar hemispheres than those with SCA3 or SCA6. Patients with MSA-C had a lower NAA/Cr in the vermis and Cho/Cr in the cerebellar hemispheres than those with SCA2 at the start, and had a lower NAA/Cr in cerebellar hemispheres than those with SCA2 at follow-ups. CONCLUSION: Characteristic patterns of neurodegenerative evolution were observed in patients with disparate SCAs and MSA-C using MRS and SARA. A continual impairment of neuronal integrity was observed in all groups of patients. The longitudinal changes of MRS metabolites and SARA scores were most striking in patients with SCA2 and MSA-C. Although the changes in the metabolites on MRS may still be used to help understand the pathophysiology of ataxia disorders, they are short of being a good biomarker.

Multi-detector row computed tomographic evaluation of a rare type of complete vascular ring: double aortic arch with atretic left arch distal to the origin of left subclavian artery.

Double aortic arch with an atretic left arch distal to the origin of left subclavian artery was diagnosed with multi-detector row computed tomography (MDCT) in two children with dysphagia. This rare type of complete vascular ring is clinically important because it may be confused with right aortic arch in mirror imaging. Anatomic details of this rare type of complete vascular ring demonstrated on MDCT facilitated appropriate surgical treatment.

Partial ring artifact on cardiac CT: image presentation and clinical implication.

In computed tomography (CT), the term "artifact" is applied to any systematic discrepancy between the CT numbers in the reconstructed image and the true attenuation coefficients of the object. A partial ring artifact in cardiac CT has a unique pattern and has not been previously reported in real clinical practice. In this report, we will demonstrate the images and animations of a cardiac CT which is affected by a partial ring artifact due to a broken detector module. The different characteristics of ring artifacts on routine and cardiac CT, and the implications for clinical interpretation will also be described. In summary, when a partial ring artifact is noted incidentally on cardiac CT, we suggest interpreting the images by reviewing reconstructed images from different RR-intervals to avoid unnecessary repeated scans and additional radiation exposure.

MDCT evaluation of cardiac involvement in hypereosinophilic syndrome: differentiating mural thrombus, infarcted, and noninfarcted myocardium by delayed-phase scanning.

Hypereosinophilic syndrome is a rare disease that can cause multiple-organ damage. Cardiac involvement, which presents as myocardial necrosis, infarction, or thrombus formation, is the leading cause of morbidity and death. Here, we present the case of a 17-year-old girl who had hypereosinophilic syndrome with cardiac involvement, which was evaluated by multidetector-row computed tomography. By means of arterial-phase and low-dose delayed-phase scanning, multidetector-row computed tomography clearly identified the mural thrombus and the infarcted and noninfarcted myocardium-which surpassed the performance of echocardiography in tissue characterization. Therefore, we propose that multidetector-row computed tomography could be a useful noninvasive tool for evaluating patients with cardiac involvement of hypereosinophilic syndrome.

Peripheral nerve regeneration using a microporous polylactic acid asymmetric conduit in a rabbit long-gap sciatic nerve transection model.

The performance of an asymmetric conduit made of microporous polylactic acid (PLA) in promoting the long-term peripheral nerve regeneration across a 20-mm-long sciatic nerve gap was evaluated by a rabbit sciatic nerve transection model. Magnetic resonance imaging (MRI) was employed to monitor the nerve regeneration process. The extents of nerve regeneration and conduit degradation were quantified by image analysis. Functional and histological analyses were followed to assess nerve reinnervation. MR images showed that the transected nerve was connected at about 4 months. The diameter of the regenerated nerve continued to increase while the conduit was gradually degraded. The conduit was completely degraded in 18 months. The degradation kinetics in vivo was estimated based on MR images. The functional recovery after 18 months was ∼82% based on electrophysiology. The extension range of the operated limb was slowly recuperated to ∼81% at 18 months. Histology showed that nerve bundles were self-assembled after 16-18 months, but the morphologies were still different from those of normal sciatic nerve. This was the first work on the long-term evaluation of peripheral nerve regeneration in a rabbit model, and the first to report the use of MRI to obtain the real-time images of regenerated nerve in a biomaterial conduit as well as to define the degradation rate of the conduit in vivo. The platform established in this study serves to evaluate the regeneration of larger-diameter (>3-mm) nerve across a long-gap bridged by a conduit.