Forward-projected Model-based Iterative Reconstruction SoluTion in Temporal Bone Computed Tomography: A Comparison Study of All Reconstruction Modes.

OBJECTIVE: Identify appropriate reconstruction modes of Forward-projected model-based Iterative Reconstruction SoluTion (FIRST) in temporal bone computed tomography (CT) and investigate the contribution of spatial resolution and noise to the visual assessment. METHODS: Sixteen temporal bone CT images were reconstructed. Two blinded radiologists assessed 8 anatomical structures and classified the visual assessment. These visual scores were compared across reconstruction modes among each anatomical structure. Visual scores and contrast-to-noise ratio, noise power spectrum (NPS) at low (NPSLow) and high (NPSHigh) spatial frequencies, and 50% modulation transfer function relationships were evaluated. RESULTS: Visual scores differed significantly for the stapedius muscle and osseous spiral lamina, with CARDIAC SHARP, BONE, and LUNG modes for the osseous spiral lamina scoring highest. Visual scores significantly positively correlated with NPSLow, NPSHigh, and 50% modulation transfer function but negatively with contrast-to-noise ratio. CONCLUSIONS: Modes providing higher spatial resolution and lower noise reduction showed an improved visual assessment of CT images reconstructed with FIRST.

Comparison of image quality between synthetic and patients' electrocardiogram-gated 320-row pediatric cardiac computed tomography.

BACKGROUND: Pediatric cardiac computed tomography (CT) can be acquired without electrode placement by using synthetic electrocardiogram (ECG). OBJECTIVE: To determine whether the depiction of gross cardiac structures and coronary arteries in 320-row pediatric CT is not inferior when CT is gated with synthetic ECG at 150 beats per minute (bpm), compared to the patients' own ECG. MATERIALS AND METHODS: Sixty 320-row CT examinations performed in children younger than 3 years old with congenital cardiac anomaly were enrolled in this retrospective study. Thirty examinations were scanned using the children's own ECG for gating and 30 examinations were scanned using synthetic ECG at 150 bpm. The image quality was compared between the two gating modes using a 3-point scale to delineate the following anatomical structures: atrial septum, ventricular septum, right atrium, right ventricle, left atrium, left ventricle, main pulmonary artery, ascending aorta, aortic arch including the patent ductus arteriosus, descending aorta, right coronary artery and left main trunk. Beam-hardening artifacts from contrast enhancement material were evaluated using a 3-point scale, and the overall image quality was evaluated using a 5-point scale. RESULTS: Synthetic ECG was not inferior to the patients' ECG in depicting each structure, beam-hardening artifact and overall image quality. Average indices were clinically acceptable imaging quality, except for subjective image quality of mid and distal coronary arteries. CONCLUSION: Pediatric cardiac CT in patients younger than 3 years old can be acquired using synthetic ECG gating, with image quality not inferior to the patients' ECG.

Mediastinoscopic view of the bronchial arteries in a series of surgical cases evaluated with three-dimensional computed tomography.

BACKGROUND: We have routinely performed three-dimensional computed tomography (3-D CT) prior to video-assisted transmediastinal esophagectomy to evaluate the small arteries in the mediastinal operative field. This evaluation would be helpful in performing mediastinoscopic esophagectomy. METHODS: Thirty-one patients who underwent transmediastinal esophagectomy with preoperative evaluations by 3-D CT were the study subject. The bronchial arteries depicted by the 3-D CT were classified by their origin and laterality. In 18 of the 31 cases, the surgical video was available and the identification rate in the video was reviewed for each of the categorized bronchial arteries. RESULTS: The detection rates of each classified artery were as follows (abbreviations, detection rate); the intercostal-bronchial trunk (IBT, 22/31), the direct left bronchial artery (LBA, 17/31), the common trunk of bronchial arteries (CTB, 7/31), the direct right bronchial artery (RBA, 2/31), and the ectopic arteries (16/31). The ectopic arteries arose from the aortic arch (11 cases), the right subclavian artery (6 cases) or the left subclavian artery (1 case). The identification rates of IBT, LBA, CTB, RBA and any of the ectopic arteries in the video review were 12/13, 4/8, 3/4, 1/1 and 2/10, respectively. CONCLUSIONS: Preoperative 3-D CT was a highly sensitive evaluation for the bronchial arteries encountered during transmediastinal esophagectomy. Orthotopic arteries except for LBA were frequently identified at the predicted sites. Although RBA and CTB were present infrequently, they often flowed into regional nodes at the bilateral bronchi or the tracheal bifurcation and, therefore, should be preoperatively evaluated.

Pediatric 320-row cardiac computed tomography using electrocardiogram-gated model-based full iterative reconstruction.

BACKGROUND: Full iterative reconstruction algorithm is available, but its diagnostic quality in pediatric cardiac CT is unknown. OBJECTIVE: To compare the imaging quality of two algorithms, full and hybrid iterative reconstruction, in pediatric cardiac CT. MATERIALS AND METHODS: We included 49 children with congenital cardiac anomalies who underwent cardiac CT. We compared quality of images reconstructed using the two algorithms (full and hybrid iterative reconstruction) based on a 3-point scale for the delineation of the following anatomical structures: atrial septum, ventricular septum, right atrium, right ventricle, left atrium, left ventricle, main pulmonary artery, ascending aorta, aortic arch including the patent ductus arteriosus, descending aorta, right coronary artery and left main trunk. We evaluated beam-hardening artifacts from contrast-enhancement material using a 3-point scale, and we evaluated the overall image quality using a 5-point scale. We also compared image noise, signal-to-noise ratio and contrast-to-noise ratio between the algorithms. RESULTS: The overall image quality was significantly higher with full iterative reconstruction than with hybrid iterative reconstruction (3.67±0.79 vs. 3.31±0.89, P=0.0072). The evaluation scores for most of the gross structures were higher with full iterative reconstruction than with hybrid iterative reconstruction. There was no significant difference between full and hybrid iterative reconstruction for the presence of beam-hardening artifacts. Image noise was significantly lower in full iterative reconstruction, while signal-to-noise ratio and contrast-to-noise ratio were significantly higher in full iterative reconstruction. CONCLUSION: The diagnostic quality was superior in images with cardiac CT reconstructed with electrocardiogram-gated full iterative reconstruction.

Diagnostic Phase of Calcium Scoring Scan Applied as the Center of Acquisition Window of Coronary Computed Tomography Angiography Improves Image Quality in Minimal Acquisition Window Scan (Target CTA Mode) Using the Second Generation 320-Row CT.

OBJECTIVE: To compare the image quality of coronary computed tomography angiography (CCTA) acquired under two conditions: 75% fixed as the acquisition window center (Group 75%) and the diagnostic phase for calcium scoring scan as the center (CS; Group CS). METHODS: 320-row cardiac CT with a minimal acquisition window (scanned using "Target CTA" mode) was performed on 81 patients. In Group 75% (n = 40), CS was obtained and reconstructed at 75% and the center of the CCTA acquisition window was set at 75%. In Group CS (n = 41), CS was obtained at 75% and the diagnostic phase showing minimal artifacts was applied as the center of the CCTA acquisition window. Image quality was evaluated using a four-point scale (4-excellent) and the mean scores were compared between groups. RESULTS: The CCTA scan diagnostic phase occurred significantly earlier in CS (75.7 ± 3.2% vs. 73.6 ± 4.5% for Groups 75% and CS, resp., p = 0.013). The mean Group CS image quality score (3.58 ± 0.63) was also higher than that for Group 75% (3.19 ± 0.66, p < 0.0001). CONCLUSIONS: The image quality of CCTA in Target CTA mode was significantly better when the center of acquisition window is adjusted using CS.

Feasibility of diffusion tensor tractography for preoperative prediction of the location of the facial and vestibulocochlear nerves in relation to vestibular schwannoma.

BACKGROUND: According to recent findings, diffusion tensor tractography (DTT) only allows prediction of facial nerve location in relation to vestibular schwannoma (VS) with high probability. However, previous studies have not mentioned why only the facial nerve was selectively visualized. Our previous report investigated the optimal conditions of DTT for normal facial and vestibulocochlear nerves. In the present study, we applied the optimal conditions of DTT to VS patients to assess the feasibility of DTT for the facial and vestibulocochlear nerves. METHODS: We investigated 11 patients with VS who underwent tumor resection. Visualized tracts were compared with locations of the facial and cochlear nerves as identified by intraoperative electrophysiological monitoring. RESULTS: With the proposed method, visualized tracts corresponded to pathway area of the facial or cochlear nerves in nine of 11 patients (81.8%); specifically, to the pathway area of the facial nerve in three of 11 patients (27.3%), and to the pathway area of the cochlear nerve in six of 11 patients (54.5%). CONCLUSIONS: We visualized facial or vestibulocochlear nerves in nine of 11 patients (81.8%). For the first time, DTT proved able to visualize not only the facial nerve but also the vestibulocochlear nerve in VS patients. Despite our findings, good methods for distinguishing whether a visualized nerve tract represents facial nerve, vestibulocochlear nerve, or only noise remain unavailable. Close attention should therefore be paid to the interpretation of visualized fibers.

Database of normal Japanese gray matter volumes in the default mode network.

PURPOSE: To show the gray matter volumes in the default mode network (DMN) using the atlas-based method and to evaluate age-related volume change in the DMN region. Estimation of gray matter volumes is interesting research because previous reports showed an association with gray matter volume (GMV) and diseases. MATERIALS AND METHODS: We focused on five nodes of the DMN (posterior cingulate, precuneus, lateral temporal cortex [LTC], medial prefrontal cortex, and inferior parietal lobule). In all, 1122 healthy adults were included in the present study. T1-weighted magnetic resonance (MR) images were obtained using a 3T-MR scanner. To investigate GMV in the DMN, segmented gray matter images were measured by the atlas-based method, using Statistical Parametric Mapping 5. Volumes were expressed using three different methods: region of interest (ROI)-volume (mL), the volume itself; ROI-TIV (%), as a percentage of total intracranial volume (individual difference of head size is corrected); and ROI-GMV (%), as a percentage of gray matter volume (individual difference of atrophy speed for aging is corrected). RESULTS: Negative correlations between measurement values on ROI and age were observed in all five ROIs of the DMN region by two measures of volume (ROI-volume (mL) and ROI-TIV (%)), in both genders. In contrast, positive correlations between measurement values on ROI and age were observed in the posterior cingulate and LTC with ROI-GMV (%), in both genders. CONCLUSION: The present study is the first report about volume change in the DMN that includes age-related effects.

[Fluoroscopy dose reduction of computed tomography guided chest interventional radiology using real-time iterative reconstruction].

The purpose of this study was to evaluate the radiation dose reduction to patients and radiologists in computed tomography (CT) guided examinations for the thoracic region using CT fluoroscopy. Image quality evaluation of the real-time filtered back-projection (RT-FBP) images and the real-time adaptive iterative dose reduction (RT-AIDR) images was carried out on noise and artifacts that were considered to affect the CT fluoroscopy. The image standard deviation was improved in the fluoroscopy setting with less than 30 mA on 120 kV. With regard to the evaluation of artifact visibility and the amount generated by the needle attached to the chest phantom, there was no significant difference between the RT-FBP images with 120 kV, 20 mA and the RT-AIDR images with low-dose conditions (greater than 80 kV, 30 mA and less than 120 kV, 20 mA). The results suggest that it is possible to reduce the radiation dose by approximately 34% at the maximum using RT-AIDR while maintaining image quality equivalent to the RT-FBP images with 120 V, 20 mA.

[Study on cine view of relative enhancement ratio map in O2-enhanced MRI].

Magnetic resonance imaging (MRI) enables the evaluation of organ structure and function. Oxygen-enhanced MRI (O2-enhanced MRI) is a method for evaluating the pulmonary ventilation function using oxygen as a contrast agent. We created the Cine View of Relative Enhancement Ratio Map (Cine RER map) in O2-enhanced MRI to easily observe the contrast effect for clinical use. Relative enhancement ratio (RER) was determined as the pixel values of the Cine RER map. Moreover, six healthy volunteers underwent O2-enhanced MRI to determine the appropriate scale width of the Cine RER map. We calculated each RER and set 0 to 1.27 as the scale width of the Cine RER map based on the results. The Cine RER map made it possible to observe the contrast effect over time and thus is a convenient tool for evaluating the pulmonary ventilation function in O2-enhanced MRI.

Corticospinal tract-sparing intensity-modulated radiotherapy treatment planning.

AIM: To establish intensity-modulated radiotherapy (IMRT) planning procedures that spare the corticospinal tract by integrating diffusion tensor tractography into the treatment planning software. BACKGROUND: Organs at risk are generally contoured according to the outline of the organ as demonstrated by CT or MRI. But a part of the organ with specific function is difficult to protect, because such functional part of the organ cannot be delineated on CT or conventional sequence of MRI. METHODS: Diagnostic and treatment planning images of glioblastoma patients who had been treated by conventional 3-dimensional conformal radiotherapy were used for re-planning of IMRT. Three-dimensional fiber maps of the corticospinal tracts were created from the diffusion tensors obtained from the patients before the surgery, and were blended with the anatomical MR images (i.e. gadolinium-enhanced T1-weighted images or T2-weighted images). DICOM-formatted blended images were transferred and fused to the planning CT images. Then, IMRT plans were attempted. RESULTS: The corticospinal tracts could be contoured as organs at risk (OARs), because the blended images contained both anatomical information and fiber-tract maps. Other OARs were contoured in a way similar to that of ordinary IMRT planning. Gross tumor volumes, clinical target volumes, planning target volumes, and other OARs were contoured on the treatment planning software, and IMRT plans were made. CONCLUSIONS: IMRT plans with diminished doses to the corticospinal tract were attained. This technique enabled us to spare specific neuron fibers as OARs which were formerly "invisible" and to reduce the probability of late morbidities.

Association between iron content and gray matter missegmentation with voxel-based morphometry in basal ganglia.

PURPOSE: To show an association between T2-weighted signal intensity (T2-SI) variation and missegmentation in the putamen of healthy adults, using 3.0-tesla magnetic resonance scanner and voxel-based morphomery (VBM). MATERIALS AND METHODS: Contiguous sagittal T1-weighted images and axial T2-weighted images of the brain were obtained from 1380 healthy participants using a 3.0 Tesla (T) MR scanner. After image preprocessing with Statistical Parametric Mapping 5, the association between T2-SI ratio (= A/B, where A is the mean of the T2-SI in the putamen, and B is that in the thalamus) variation and gray matter missegmentation was assessed using VBM. RESULTS: A significant positive correlation was revealed between T2-SI ratio and bilateral putamen volume on the gray matter images. In addition, we found a significant negative correlation between T2-SI ratio and bilateral putamen volume on the white matter images. We consider that these results show the influence of missegmentation. CONCLUSION: To the best of our knowledge, this is the first VBM study to demonstrate an association between T2-SI variation and gray matter missegmentation. These results indicate the possibility that VBM may be more affected by individual differences in iron content levels than by individual differences in tissue volumes if detected-regions with VBM contained substantial iron deposition.

Bilateral pre- and postcentral gyrus volume positively correlates with T2-SNR of putamen in healthy adults.

INTRODUCTION: The aim of the present study was to investigate the correlation between local gray matter volume and signal-to-noise ratio on T2-weighted imaging (T2-SNR) of putamen in healthy adults using two tools: voxel-based morphometry (VBM) treating age as a confounding covariate to control for age-related gray matter volume changes and high spatial resolution T1-weighted imaging acquired with a 3.0-T magnetic resonance (3T-MR) scanner. METHODS: Contiguous sagittal T1-weighted images and axial T2-weighted images of the brain were obtained from 1,380 healthy participants. T2-SNR of putamen was defined as A/B, where A is the mean T2-weighted signal intensity (T2-SI) in the right and left sides of putamen, and B is the background noise. The software Statistical Parametric Mapping 5 was used for image segmentation. The association between T2-SNR of putamen and gray matter volume was assessed with VBM, treating age as a confounding covariate. RESULTS: A significant positive correlation was obtained between T2-SNR of putamen and bilateral pre- and postcentral gyrus volume. CONCLUSION: To the best of our knowledge, this is the first VBM study to show an age-independent relationship between T2-SNR of putamen and bilateral pre- and postcentral gyrus volumes in healthy adults.

Diffeomorphic Anatomical Registration Through Exponentiated Lie Algebra provides reduced effect of scanner for cortex volumetry with atlas-based method in healthy subjects.

INTRODUCTION: This study aimed to investigate whether the effect of scanner for cortex volumetry with atlas-based method is reduced using Diffeomorphic Anatomical Registration Through Exponentiated Lie Algebra (DARTEL) normalization compared with standard normalization. METHODS: Three-dimensional T1-weighted magnetic resonance images (3D-T1WIs) of 21 healthy subjects were obtained and evaluated for effect of scanner in cortex volumetry. 3D-T1WIs of the 21 subjects were obtained with five MRI systems. Imaging of each subject was performed on each of five different MRI scanners. We used the Voxel-Based Morphometry 8 tool implemented in Statistical Parametric Mapping 8 and WFU PickAtlas software (Talairach brain atlas theory). The following software default settings were used as bilateral region-of-interest labels: "Frontal Lobe," "Hippocampus," "Occipital Lobe," "Orbital Gyrus," "Parietal Lobe," "Putamen," and "Temporal Lobe." RESULTS: Effect of scanner for cortex volumetry using the atlas-based method was reduced with DARTEL normalization compared with standard normalization in Frontal Lobe, Occipital Lobe, Orbital Gyrus, Putamen, and Temporal Lobe; was the same in Hippocampus and Parietal Lobe; and showed no increase with DARTEL normalization for any region of interest (ROI). CONCLUSION: DARTEL normalization reduces the effect of scanner, which is a major problem in multicenter studies.

Repeatability of measured brain volume by atlas-based method using T1-weighted image.

The aims of this study were to (1) investigate the repeatability of measured volumes using the atlas-based method in each area of the brain, and (2) validate our hypothesis that the repeatability of the measured volumes with the atlas-based method was improved by using smoothed images. T1-weighted magnetic resonance images were obtained in five healthy subjects using the 1.5-T scanner. We used Statistical Parametric Mapping 5 and WFU PickAtlas software (theory of the Talairach brain atlas). Volumes inside region-of-interest (ROI) were measured in ten sets (five subjects × right and left) on six ROIs, respectively. One set comprises five images (one subject × five 3D-T1WIs). The percentage change was defined as [100 × (measured volume-mean volume in each set)/mean volume in each set)]. As a result, the average percentage changes using non-smoothed image on each ROI were as follows: gray matter, 0.482%; white matter, 0.375%; cerebrospinal fluid images, 0.731%; hippocampus, 0.864%; orbital gyrus, 1.692%; cerebellum posterior lobe, 0.854%. Using smoothed images with large FWHM resulted in improved repeatability on orbital gyrus. This is the first report of repeatability in each brain structure and improved repeatability with smoothed images using the atlas-based method.

Chronic nicotinamide mononucleotide supplementation elevates blood nicotinamide adenine dinucleotide levels and alters muscle function in healthy older men.

Preclinical studies have revealed that the elevation of nicotinamide adenine dinucleotide (NAD + ) upon the administration of nicotinamide mononucleotide (NMN), an NAD + precursor, can mitigate aging-related disorders; however, human data on this are limited. We investigated whether the chronic oral supplementation of NMN can elevate blood NAD + levels and alter physiological dysfunctions in healthy older participants. We administered 250 mg NMN per day to aged men for 6 or 12 weeks in a placebo-controlled, randomized, double-blind, parallel-group trial. Chronic NMN supplementation was well tolerated and caused no significant deleterious effect. Metabolomic analysis of whole blood samples demonstrated that oral NMN supplementation significantly increased the NAD + and NAD + metabolite concentrations. There were nominally significant improvements in gait speed and performance in the left grip test, which should be validated in larger studies; however, NMN exerted no significant effect on body composition. Therefore, chronic oral NMN supplementation can be an efficient NAD + booster for preventing aging-related muscle dysfunctions in humans.

Automatic Aortic Valve Cusps Segmentation from CT Images Based on the Cascading Multiple Deep Neural Networks.

Accurate morphological information on aortic valve cusps is critical in treatment planning. Image segmentation is necessary to acquire this information, but manual segmentation is tedious and time consuming. In this paper, we propose a fully automatic aortic valve cusps segmentation method from CT images by combining two deep neural networks, spatial configuration-Net for detecting anatomical landmarks and U-Net for segmentation of aortic valve components. A total of 258 CT volumes of end systolic and end diastolic phases, which include cases with and without severe calcifications, were collected and manually annotated for each aortic valve component. The collected CT volumes were split 6:2:2 for the training, validation and test steps, and our method was evaluated by five-fold cross validation. The segmentation was successful for all CT volumes with 69.26 s as mean processing time. For the segmentation results of the aortic root, the right-coronary cusp, the left-coronary cusp and the non-coronary cusp, mean Dice Coefficient were 0.95, 0.70, 0.69, and 0.67, respectively. There were strong correlations between measurement values automatically calculated based on the annotations and those based on the segmentation results. The results suggest that our method can be used to automatically obtain measurement values for aortic valve morphology.

3 Tesla MRI detects accelerated hippocampal volume reduction in postmenopausal women.

PURPOSE: To clarify age-related structural changes specific to hippocampal volume by hierarchizing according to age, gender, and menopausal status. Many studies report the neuroprotective effects of estrogen and age-related brain volume changes; however, there are no studies regarding age-related change specific to hippocampal volume in terms of age, gender, and menopausal status. MATERIALS AND METHODS: T1-weighted MR images were obtained in 412 healthy adults divided into eight groups according to age and gender, to analyze brain volume change focusing on hippocampal volume. RESULTS: Voxel-based morphometry (VBM) revealed significantly smaller gray matter volume in the hippocampus bilaterally in females aged in their fifties (51 of 59 females were at menopause) compared with females in their forties (3 of 46 females were at menopause). No significant difference was found, however, between female groups in their fifties versus sixties, or sixties versus seventies; or between male groups in their forties versus fifties, fifties versus sixties, or sixties versus seventies. In addition, VBM revealed significant hippocampal volume reduction bilaterally in all postmenopausal women compared with all premenopausal women. CONCLUSION: The results of the current study suggest that the menopause may be associated with hippocampal volume reduction.

Entorhinal cortex volume measured with 3T MRI is positively correlated with the Wechsler Memory Scale-Revised logical/verbal memory score for healthy subjects.

INTRODUCTION: Previous studies revealed a correlation between local brain volume and cognitive function. The aim of the present study was to investigate the correlation between local gray matter volume and the Wechsler Memory Scale-Revised (WMS-R) logical/verbal memory (WMS-R-verbal) score in healthy adults using a 3 Tesla magnetic resonance scanner and voxel-based morphometry (VBM). METHODS: T1-weighted magnetic resonance images were obtained in 1,169 healthy adults. The T1-weighted images in native space were bias-corrected, spatially normalized, and segmented into gray matter, white matter, and cerebrospinal fluid images with Statistical Parametric Mapping 5. To investigate regionally the specific effects of the WMS-R-verbal score on the gray matter images, simple regression analysis was performed by VBM treating age, total intracranial volume, and gender as confounding covariates. A P value of less than 0.05 corrected with false discovery rate in voxel difference was considered to be statistically significant. RESULTS: Our study showed a significant positive correlation between the WMS-R-verbal score and the bilateral entorhinal cortex volume. In the right entorhinal, T value is 4.75, and the size of the clusters is 155 voxels. In the left entorhinal, T value is 4.08, and the size of the clusters is 23 voxels. A significant negative correlation was not found. CONCLUSION: To our knowledge, this is the first VBM study showing that entorhinal cortex volume is positively correlated with the WMS-R-verbal score for healthy subjects. Therefore, in our structural neuroimaging study, we add evidence to the hypothesis that the entorhinal cortex is involved in verbal memory processing.

Sleep-Induced Glottis Closure in Multiple System Atrophy Evaluated by Four-Dimensional Computed Tomography.

Multiple system atrophy (MSA) is a progressive neurodegenerative disorder. Since patients with MSA often have sleep-related respiratory disorders including upper-airway obstruction and/or central sleep disturbance, appropriate evaluation of the upper airway especially during sleep may be indispensable. Fiberoptic laryngoscopy during diazepam-induced sleep has been reported for upper-airway obstruction verification. However, some patients cannot endure the uncomfortable sensation of the fiberscope. To address these issues, we devised a protocol of four four-dimensional computed tomography (4D-CT) for upper-airway evaluation during sleep. Here, we report the case of patient with MSA who was evaluated for upper-airway obstruction during sleep using 4D-CT. A 46-year-old man (height 1.60 m, weight 79 kg) was admitted to our neurological department for tracheal intubation because of a sudden onset of respiratory failure occurring at night. At the age of 45 years, he was diagnosed as MSA with predominant parkinsonism. As pulmonary disease had been excluded and his swallowing was normal, our differential diagnoses were central sleep apnea or obstructive sleep apnea related to his MSA or obstructive sleep apnea (SA) related to his obesity. A tracheostomy was done to maintain the airway after extubation. Polysomnography showed obstructive SA and not central SA. Awake fiberoptic laryngoscopy showed no upper airway obstruction but bilateral vocal abduction impairment (BVAI) during inspiration. To assess the spatial and temporal conditions of the upper respiratory tract-the patient could not tolerate sleep laryngoscopy-we carried out a 4D-CT. Reconstructed 4D-CT images of respiration during sleep showed clear abnormalities: glottis closure at the terminal stage of inspiration and subsequent velopharyngeal closure. As glottis closure does not occur normally in obesity patients, the cause of the respiratory failure in this patient was considered MSA-related sleep-induced airway obstruction. We decided to keep the tracheostoma, because BVAI in patients with MSA may be getting worse, although central apnea after tracheostomy may cause sudden central origin-related death; 4 months postoperatively, the patient had experienced no further airway-related complications. This report indicates that 4D-CT sequential upper-airway assessment during sleep is useful for determining the abnormalities causing obstructive SA in patients with MSA.

Evaluation of peripheral bronchiole visualization using model-based iterative reconstruction in quarter-detector computed tomography.

This study aimed to evaluate the visualization of peripheral bronchioles in normal lungs via quarter-detector computed tomography (QDCT). Visualization of bronchioles within 10 mm from the pleura is considered a sign of bronchiectasis. However, it is not known peripheral bronchioles how close to the pleura in normal lungs can be tracked using QDCT. This study included 228 parts in 76 lungs from 38 consecutive patients who underwent QDCT. Reconstruction was performed with different thicknesses, increments, and matrix sizes: 0.5-mm thickness and increment with 512 and 1024 matrixes (Group5 and Group10, respectively) and 0.25-mm thickness and increment with 1024 matrix (Group10Thin). The distance between the most peripheral bronchiole visible and the pleura was determined in the three groups. The distance between the peripheral bronchial duct ends and the nearest pleural surface were significantly shorter in the order of Group10Thin, Group10, and Group5, and the mean distances from the pleura in Group10Thin and Group10 were shorter than 10 mm. These findings suggest the visualization of peripheral bronchioles in QDCT was better with a 1024 axial matrix than with a 512 matrix, and with a 0.25-mm slice thickness/increment than with a 0.5-mm slice thickness/increment. Our study also indicates bronchioles within 10 mm of the pleura do not necessarily indicate pathology.