Published papers

Background: The development of ultra-high–resolution CT (U-HRCT) is expected to improve the accuracy of coronary stenosis evaluation. This study aimed to evaluate the accuracy of the stenosis severities of coronary artery phantoms estimated using U-HRCT by comparing them to those estimated with conventional CT. Methods: Coronary artery phantoms with non-calcified and calcified lesions were scanned with conventional CT (64-row ​× ​0.625 ​mm) and U-HRCT (32-row ​× ​0.3125 ​mm). The coronary artery phantoms had lumen diameters of 2.0, 3.0, and 4.0 ​mm with non-calcified lesions representing 0%, 25%, 50%, and 75% stenosis and 3.0 and 4.0 ​mm with calcified lesions representing 0%, 25%, 50%, and 75% stenosis. The lumen diameters at the stenotic and non-stenotic regions were measured, and the stenosis severities were compared with the true values. Results: For non-calcified lesions, conventional CT significantly underestimated the stenosis severity in the phantom showing 75% stenosis with lumen diameters of 2.0 and 3.0 ​mm (p ​< ​0.05), while the estimated stenosis severities were not significantly different from the true values at all settings with U-HRCT. For the calcified lesions, conventional CT overestimated the stenosis severities at all settings (p ​< ​0.05), while U-HRCT yielded estimations closer to the true values, although still with some overestimation (p ​< ​0.05). Conclusion: By using U-HRCT, the estimated stenosis severities of the coronary artery with non-calcified lesion become almost equal to the true value, while those with calcified lesion are still overestimated although they become closer to the true value.

Objective: To evaluate wall discontinuity, as observed using 64-slice multidetector-row computed tomography (64-MDCT), as a direct finding (DF) indicating the perforation site in patients with gastrointestinal (GI) tract perforations. Methods: We retrospectively studied 41 consecutive patients presenting with acute abdomen and exhibiting extraluminal air (EA) on 64-MDCT. Three readers evaluated the distribution of EA, extraluminal faeces, dirty mass, dirty fat sign, extraluminal fluid collection and bowel wall thickening (i.e. conventional findings, CFs) as well as DFs. Results: Twenty-two cases were surgically or endoscopically confirmed to have upper GI tract perforations, and 19 had lower GI tract perforations. The DFs correctly identified the sites of perforation in 80.5% of patients when 2-mm-thick imaging slices were used. For the detection of upper GI tract perforations, the sensitivity, specificity and accuracy were 95.5%, 94.7% and 95.1% for the DFs and 50.0%, 100% and 73.2% for the CFs, respectively. Significant differences in sensitivity (p<0.001) and diagnostic accuracy (p<0.05) were observed between the DFs and CFs for upper GI perforations but not for lower GI tract perforations. Conclusion: DFs of the perforation site by using 64-MDCT were more sensitive and accurate than CFs for the detection of upper GI tract perforations. © 2009 European Society of Radiology.

BACKGROUND: Red blood cells (RBCs) labeled with single-photon emitters have been clinically used for blood-pool imaging. Although some PET tracers have been introduced for blood-pool imaging, they have not yet been widely used. The present study investigated the feasibility of labeling RBCs with 18F-2-deoxy-2-fluoro-D-glucose (18F-FDG) for blood-pool imaging with PET. RBCs isolated from venous blood of rats were washed with glucose-free phosphate-buffered saline and labeled with 18F-FDG. To optimize labeling efficiency, the effects of glucose deprivation time and incubation (labeling) time with 18F-FDG were investigated. Post-labeling stability was assessed by calculating the release fraction of radioactivity and identifying the chemical forms of 18F in the released and intracellular components of 18F-FDG-labeled RBCs incubated in plasma. Just after intravenous injection of the optimized autologous 18F-FDG-labeled RBCs, dynamic PET scans were performed to evaluate in vivo imaging in normal rats and intraabdominal bleeding models (temporary and persistent bleeding). RESULTS: The optimal durations of glucose deprivation and incubation (labeling) with 18F-FDG were 60 and 30 min, respectively. As low as 10% of 18F was released as the form of 18F-FDG from 18F-FDG-labeled RBCs after a 60-min incubation. Dynamic PET images of normal rats showed strong persistence in the cardiovascular system for at least 120 min. In the intraabdominal bleeding models, 18F-FDG-labeled RBC PET visualized the extravascular blood clearly and revealed the dynamic changes of the extravascular radioactivity in the temporary and persistent bleeding. CONCLUSIONS: RBCs can be effectively labeled with 18F-FDG and used for blood-pool imaging with PET in rats.

PURPOSE: We developed a method of image data projection of bone SPECT into 3D volume-rendered CT images for 3D SPECT/CT fusion. The aims of our study were to evaluate its feasibility and clinical usefulness. METHODS: Whole-body bone scintigraphy (WB) and SPECT/CT scans were performed in 318 cancer patients using a dedicated SPECT/CT systems. Volume data of bone SPECT and CT were fused to obtain 2D SPECT/CT images. To generate our 3D SPECT/CT images, colored voxel data of bone SPECT were projected onto the corresponding location of the volume-rendered CT data after a semi-automatic bone extraction. Then, the resultant 3D images were blended with conventional volume-rendered CT images, allowing to grasp the three-dimensional relationship between bone metabolism and anatomy. WB and SPECT (WB + SPECT), 2D SPECT/CT fusion, and 3D SPECT/CT fusion were evaluated by two independent reviewers in the diagnosis of bone metastasis. The inter-observer variability and diagnostic accuracy in these three image sets were investigated using a four-point diagnostic scale. RESULTS: Increased bone metabolism was found in 744 metastatic sites and 1002 benign changes. On a per-lesion basis, inter-observer agreements in the diagnosis of bone metastasis were 0.72 for WB + SPECT, 0.90 for 2D SPECT/CT, and 0.89 for 3D SPECT/CT. Receiver operating characteristic analyses for the diagnostic accuracy of bone metastasis showed that WB + SPECT, 2D SPECT/CT, and 3D SPECT/CT had an area under the curve of 0.800, 0.983, and 0.983 for reader 1, 0.865, 0.992, and 0.993 for reader 2, respectively (WB + SPECT vs. 2D or 3D SPECT/CT, p < 0.001; 2D vs. 3D SPECT/CT, n.s.). The durations of interpretation of WB + SPECT, 2D SPECT/CT, and 3D SPECT/CT images were 241 ± 75, 225 ± 73, and 182 ± 71 s for reader 1 and 207 ± 72, 190 ± 73, and 179 ± 73 s for reader 2, respectively. As a result, it took shorter time to read 3D SPECT/CT images than 2D SPECT/CT (p < 0.0001) or WB + SPECT images (p < 0.0001). CONCLUSIONS: 3D SPECT/CT fusion offers comparable diagnostic accuracy to 2D SPECT/CT fusion. The visual effect of 3D SPECT/CT fusion facilitates reduction of reading time compared to 2D SPECT/CT fusion.

© 2019 Background: Fluorine-18 sodium fluoride (NaF), a bone-seeking radiopharmaceutical used to detect osseous metastases, localizes in regions of microcalcification in atherosclerosis. Objectives: To determine if atherosclerosis of penile arteries plays a role in erectile dysfunction (ED), this study analyzed NaF images in prostate cancer patients. Methods: NaF positron emission tomography–computed tomography bone scans were evaluated in 437 prostate cancer patients (age 66.6 ± 8.7 years). Their urologic histories were reviewed for prevalent ED (diagnosed before the scan date) or incident ED (no ED at first scan, but developed during 1-year follow-up); patients with no ED (neither before the scan nor during follow-up) were included as a control group. A semicircular region of interest was set on the dorsal one-half of the penis (to avoid residual excreted activity in the urethra) on 5 contiguous slices at the base of the penis on positron emission tomography–computed tomography coronal reconstructions, and the average standardized uptake value (SUVmax) was described as NaF uptake. Results: Of 437 patients, 336 (76.9%) had prevalent ED, 60 incident ED (13.7%), and 41 had no ED (9.4%). SUVmax in patients with prevalent (median 1.88; interquartile range [IQR]: 1.67 to 2.16) or incident (median 1.86; IQR: 1.72 to 2.08) ED was significantly higher than no ED (median 1.42; IQR: 1.25 to 1.54) patients (p < 0.001). After adjustment for other risk factors, the odds ratio of prevalent or incident ED was 25.2 (95% confidence interval: 9.5 to 67.0) for every 0.5-U increment in SUVmax with receptor operating characteristic area of 0.91 (95% confidence interval: 0.88 to 0.94). Conclusions: NaF uptake in penile vessels suggests that atherosclerosis is associated with ED in prostate cancer patients. The importance of NaF uptake needs to be tested in noncancer subjects and cause-effect relationship needs to be established.

Background: Visual snow syndrome (VSS) is a neurological condition characterized by persistent flickering dots in the visual fields, palinopsia, enhanced entoptic phenomenon, photophobia, and nyctalopia. Neuroimaging evidence supports the role of the visual association cortex in visual snow syndrome. Case series: We provided clinical care to three patients with visual snow syndrome, in whom [ I]-IMP single-photon emission computed tomography (SPECT) imaging was performed. Case 1 was a 21-year-old male with a past history of migraine with aura who exhibited visual snow and entoptic phenomenon. In this patient, [ I]-IMP SPECT imaging revealed right occipital and temporal hypoperfusion with a distribution matching the ventral visual stream. [ I]-IMP SPECT imaging detected only mild bilateral frontal hypoperfusion in Case 2 and no overt abnormalities in Case 3. Conclusion: Although visual snow syndrome seems to be a heterogenous condition, our observations indicate that abnormal visual processing within the ventral visual stream may play a role in the pathogenesis of this condition. 123 123 123

Humans can walk stably and efficiently. One of the most distinctive characteristics of human waking is two-peaked vertical ground force (GRF), which generate efficient human walking. A part of such characteristics is brought by the mechanical characteristics of the human foot, that is the mechanical compliance and its complex structure consisting of skins, muscles, ligaments, and bones. The goal of this study is to clarify the generation mechanism of two-peaked GRF of human walking. In this study, we particularly focused on phalangeal ligaments and plantar fascia and analyze their contribution to GRF. To this end, we dealt with anatomically detailed threedimensional dynamical finite element analysis of the human foot. The GRF profiles and plantar pressure distribution was analyzed changing the existence condition of phalangeal ligaments and/or plantar fascia. From the results, it was revealed that phalangeal ligaments and plantar fascia are important to reproduce a two-peaked GRF profiles.

A human foot has a complex structure which consists of a flexible flesh and many muscles, tendons, ligaments, and bones. The complex structure is supposed to contribute to efficient and stable bipedal locomotion. Detailed behavior of the foot complex during walking, however, is not well unerstood. We built a musculoskeletal gait simulator driven by pneumatic artificial muscles in order to solve a mechanism of a human gait. We measured ground reaction force of the musculoskeletal gait simulator during the stance phase by using a force plate. This gait simulator's vertical ground reaction force has two high peaks like a human's.

A human foot complex consists of a flexible flesh and many muscles, ligaments, and bones. Structured compliance provided by the complex structure is supposed to contribute to efficient and stable bipedal locomotion. Detailed behavior of the foot complex during walking, however, is not well understood . We built a gait simulator driven by pneumatic musculoskeletal system in order to clarify the mechanism of a human walking by using the gait simulator with a cadaver foot. This gait simulator duplicates the double support phase in experiment environment. We also made realistic foot model with bones and artificial skin as a test model of new robot foot for testing the performance of the gait simulator.

我々は手関節自動運動中の橈骨月状骨面の月状骨接触領域を4DCTを用いて計測した.健常ボランティア8名(男性4名,女性4名)を対象とし,4DCT撮影を手関節掌背屈運動,前腕回内外運動について行った.最大掌屈位,中間位,最大背屈位と最大回内位,中間位,最大回外位のフレームでの月状骨と橈骨月状骨窩の表面間距離を計算し,表面間距離1.5mm以下の部分を推定接触領域と定義した.月状骨の重心位置の橈骨関節面の前後方向への変位も計算した.推定接触領域は中間位と比較し,背屈位と回内位で有意に増加していた.月状骨重心位置は中間位と比較して背屈位と回内位で掌側へ有意に移動していた.月状骨窩掌側への応力集中は背屈位に加え,回内位で大きくなることが推測される.これらの肢位における橈骨月状骨面への荷重変化を考慮して保存加療や手術後の後療法を施行することが重要であると考える.(著者抄録)

末梢動脈疾患の診断や治療方針の決定に画像検査が果たす役割は大きく，マルチスライスCTを用いた低侵襲診断が重要な役割を占めるようになっている．マルチスライスCTは簡便で低侵襲であり，3次元画像を用いた詳細な評価が可能で，末梢動脈疾患においても高い診断能が得られている．また精度の高い血管径計測も可能であり，治療のプランニングに有用である．

Arteriovenous malformations of the sole of the foot are rare and can cause disturbances in normal living activities. We report a case of a plantar arteriovenous malformation in a 24-year-old male with pain and difficulty in walking. The arteriovenous malformation was complex, with a large and poorly marginated nidus, so we considered that with surgical resection, walking disabilities would be inevitable. When surgical removal of vascular mass is difficult, embolization alone can be effective. Therefore, he was treated with 4 therapeutic embolization procedures. Transvenous approaches to the venous sac and direct punctures of the nidus was performed. The nidus was successfully eradicated by embolization using alcohol, resulting in the disappearance of associated symptoms. Appropriate imaging is essential for diagnosis and evaluation of treatment. We were successful in achieving improved quality of life and satisfaction for a rare and difficult case by percutaneous embolization and sclerotherapy.

Objectives: To investigate the clinical utility of the Vesical Imaging-Reporting and Data System (VI-RADS) by comparing its diagnostic performance for muscle-invasive bladder cancer (MIBC) between radiologists and urologists based on multiparametric MRI, including three-dimensional (3D) fast spin-echo (FSE) T2-weighted acquisitions. Methods: This study included 66 treatment-naïve patients (60 men, 6 women; mean age 74.0 years) with pathologically proven bladder cancer who underwent multiparametric MRI, including 3D FSE T2-weighted imaging, before transurethral bladder tumour resection between January 2010 and November 2018. The MRI scans were categorised according to the five-point VI-RADS score by four independent readers (two board-certified radiologists and board-certified urologists each), blinded to the histopathological findings. The VI-RADS scores were compared with the postoperative histopathological diagnosis. Interobserver agreement was assessed using weighted kappa coefficients. ROC analysis and generalised estimating equations were used to evaluate the diagnostic performance. Results: Forty-nine (74.2%) and 17 (25.8%) tumours were confirmed to be non-MIBC and MIBC, respectively, based on pathological examination. The interobserver agreement was good-to-excellent between all pairs of readers (range, 0.73–0.91). The urologists’ sensitivity/specificity values for DCE-MRI VI-RADS scores were significantly lower than those of radiologists. No significant differences were observed for the overall VI-RADS score. The AUC for the overall VI-RADS score was 0.94, 0.92, 0.89, and 0.87 for radiologists 1 and 2 and urologists 1 and 2, respectively. Conclusions: The VI-RADS score, based on multiparametric MRI including 3D FSE T2-weighted acquisitions, can be useful for radiologists and urologists to determine the bladder cancer muscle invasion status preoperatively. Key Points: • VI-RADS (using multiparametric MRI including 3D FSE T2-weighted acquisitions) achieves good to excellent interobserver agreement and has similar diagnostic performance for detecting muscle invasion by both radiologists and urologists. • The diagnostic performance of the overall VI-RADS score is high for both radiologists and urologists, particularly due to the dominant effect of diffusion-weighted imaging on the overall VI-RADS score. • The sensitivity and specificity values of the T2WI VI-RADS scores for four readers in our study (using 3D FSE T2-weighted acquisitions) were similar (with slightly higher specificity values) to previously published results (using 2D FSE T2-weighted acquisitions).

Currently, no clinical studies have compared the inspiratory and expiratory volumes of unilateral lung or of each lobe among supine, standing, and sitting positions. In this prospective study, 100 asymptomatic volunteers underwent both low-radiation-dose conventional (supine position, with arms raised) and upright computed tomography (CT) (standing and sitting positions, with arms down) during inspiration and expiration breath-holds and pulmonary function test (PFT) on the same day. We compared the inspiratory/expiratory lung/lobe volumes on CT in the three positions. The inspiratory and expiratory bilateral upper and lower lobe and lung volumes were significantly higher in the standing/sitting positions than in the supine position (5.3–14.7% increases, all P < 0.001). However, the inspiratory right middle lobe volume remained similar in the three positions (all P > 0.15); the expiratory right middle lobe volume was significantly lower in the standing/sitting positions (16.3/14.1% decrease) than in the supine position (both P < 0.0001). The Pearson’s correlation coefficients (r) used to compare the total lung volumes on inspiratory CT in the supine/standing/sitting positions and the total lung capacity on PFT were 0.83/0.93/0.95, respectively. The r values comparing the total lung volumes on expiratory CT in the supine/standing/sitting positions and the functional residual capacity on PFT were 0.83/0.85/0.82, respectively. The r values comparing the total lung volume changes from expiration to inspiration on CT in the supine/standing/sitting positions and the inspiratory capacity on PFT were 0.53/0.62/0.65, respectively. The study results could impact preoperative CT volumetry of the lung in lung cancer patients (before lobectomy) for the prediction of postoperative residual pulmonary function, and could be used as the basis for elucidating undetermined pathological mechanisms. Furthermore, in addition to morphological evaluation of the chest, inspiratory and expiratory upright CT may be used as an alternative tool to predict lung volumes such as total lung capacity, functional residual capacity, and inspiratory capacity in situation in which PFT cannot be performed such as during an infectious disease pandemic, with relatively more accurate predictability compared with conventional supine CT.

Introduction: In the novel coronavirus disease (COVID-19) pandemic era, it is essential to rule out COVID-19 effectively to prevent transmission in both communities and medical facilities. According to previous reports in high prevalence areas, CT screening may be useful in the diagnosis of COVID-19. However, the value of CT screening in low prevalence areas has scarcely been reported. Methods: This report examines the diagnostic efficacy of CT screening before admission to a hospital in Tokyo. We conducted a retrospective analysis at Keio University Hospital from April 6, 2020, through May 29, 2020. We set up an outpatient screening clinic on April 6 for COVID-19, administering both PCR with nasopharyngeal swabs and chest CT for all patients scheduled for surgery under general anesthesia. Results: A total of 292 asymptomatic patients were included in this study. There were three PCR-positive patients, and they all had negative CT findings, which revealed that both the sensitivity and positive predictive value of CT (PPV) were 0%. There were nine CT-positive patients; the specificity and the negative predictive value (NPV) were 96.9% and 98.9%, respectively. Conclusion: CT screening was not useful in low prevalence areas at this time in Tokyo, even with the inclusion of the most prevalent phase. Given that the utility of CT screening depends on disease prevalence, the criteria for performing CT screening based on the prevalence of COVID-19 should be established.