Yokoyama, Yoichi



School of Medicine, Department of Radiology (Diagnostic Radiology) (Shinanomachi)



External Links


Papers 【 Display / hide

  • Three-dimensional evaluation of the coccyx movement between supine and standing positions using conventional and upright computed tomography imaging

    Yagi F., Yamada Y., Yamada M., Yokoyama Y., Mukai K., Nakahara T., Narita K., Jinzaki M.

    Scientific Reports (Scientific Reports)  11 ( 1 )  2021.12

     View Summary

    Currently, no three-dimensional reference data exist for the normal coccyx in the standing position on computed tomography (CT); however, this information could have utility for evaluating patients with coccydynia and pelvic floor dysfunction. Thus, we aimed to compare coccygeal parameters in the standing versus supine positions using upright and supine CT and evaluate the effects of sex, age, and body mass index (BMI) on coccygeal movement. Thirty-two healthy volunteers underwent both upright (standing position) and conventional (supine position) CT examinations. In the standing position, the coccyx became significantly longer and straighter, with the tip of the coccyx moving backward and downward (all p < 0.001). Additionally, the coccygeal straight length (standing/supine, 37.8 ± 7.1/35.7 ± 7.0 mm) and sacrococcygeal straight length (standing/supine, 131.7 ± 11.2/125.0 ± 10.7 mm) were significantly longer in the standing position. The sacrococcygeal angle (standing/supine, 115.0 ± 10.6/105.0 ± 12.5°) was significantly larger, while the lumbosacral angle (standing/supine, 21.1 ± 5.9/25.0 ± 4.9°) was significantly smaller. The migration length of the tip of the coccyx (mean, 7.9 mm) exhibited a moderate correlation with BMI (r = 0.42, p = 0.0163). Our results may provide important clues regarding the pathogenesis of coccydynia and pelvic floor dysfunction.

  • Effect of gravity on brain structure as indicated on upright computed tomography

    Yokoyama Y., Yamada Y., Kosugi K., Yamada M., Narita K., Nakahara T., Fujiwara H., Toda M., Jinzaki M.

    Scientific Reports (Scientific Reports)  11 ( 1 )  2021.12

     View Summary

    We aimed to use upright computed tomography (CT) to depict posture-related changes in the brain tissue under normal gravity. Thirty-two asymptomatic volunteers underwent upright CT in the sitting position and conventional CT in the supine position on the same day. We compared the shift of the pineal body, cerebellar tonsil, the length of pituitary stalk, optic nerve sheath area and perimeter (ONSA and ONSP, respectively), and lateral ventricular volume between the supine and sitting positions. We also compared shape changes of the cerebrospinal fluid (CSF) spaces at different sites between both positions. In the sitting position, the pineal body shifted 0.68 ± 0.27 mm in the ventral direction and 0.76 ± 0.24 mm in the caudal direction, the length of pituitary stalk decreased by 1.23 ± 0.71 mm, the cerebellar tonsil descended by 2.10 ± 0.86 mm, the right ONSA decreased by 15.21 ± 6.54%, the left ONSA decreased by 15.30 ± 7.37%, the right ONSP decreased by 8.52 ± 3.91%, the left ONSP decreased by 8.20 ± 4.38%, and the lateral ventricular volume decreased by 5.07 ± 3.24% (all P < 0.001). We also observed changes in the shape of CSF spaces with changes in posture. We concluded that the intracranial structure of healthy subjects and volume of ventricles changed according to posture on Earth.

  • Differences in airway lumen area between supine and upright computed tomography in patients with chronic obstructive pulmonary disease

    Chubachi S., Yamada Y., Yamada M., Yokoyama Y., Tanabe A., Matsuoka S., Niijima Y., Yamasawa W., Irie H., Murata M., Fukunaga K., Jinzaki M.

    Respiratory Research (Respiratory Research)  22 ( 1 )  2021.12

    ISSN  14659921

     View Summary

    Background: No clinical studies to date have compared the inspiratory and expiratory airway lumen area between supine and standing positions. Thus, the aims of this study were twofold: (1) to compare inspiratory and expiratory airway lumen area (IAA and EAA, respectively) on computed tomography (CT) among supine and standing positions; and (2) to investigate if IAA and EAA are associated with lung function abnormality in patients with chronic obstructive pulmonary disease (COPD). Methods: Forty-eight patients with COPD underwent both low-dose conventional (supine position) and upright CT (standing position) during inspiration and expiration breath-holds and a pulmonary function test (PFT) on the same day. We measured the IAA and EAA in each position. Results: For the trachea to the third-generation bronchi, the IAA was significantly larger in the standing position than in the supine position (4.1–4.9% increase, all p < 0.05). The EAA of all bronchi was significantly larger in the standing position than in the supine position (9.7–62.5% increases, all p < 0.001). The correlation coefficients of IAA in the standing position and forced expiratory volume in 1 s were slightly higher than those in the supine position. The correlation coefficients of EAA or EAA/IAA in the standing position and residual volume, and the inspiratory capacity/total lung capacity ratio were higher than those in the supine position. Conclusions: Airway lumen areas were larger in the standing position than in the supine position. IAAs reflect airway obstruction, and EAAs reflect lung hyperinflation. Upright CT might reveal these abnormalities more precisely. Trial registration University Hospital Medical Information Network (UMIN 000026587), Registered 17 March 2017. URL: https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000030456.

  • Orthostatic Enlargement of a Supracerebellar Arachnoid Cyst With Cerebellar Descent Visualized by Upright Computed Tomography

    Yoshida K., Toda M., Yamada Y., Yamada M., Yokoyama Y., Fujiwara H., Kosugi K., Sasaki H., Jinzaki M.

    World Neurosurgery (World Neurosurgery)  145   256 - 259 2021.01

    ISSN  18788750

     View Summary

    Background: Posterior fossa arachnoid cysts are often asymptomatic, but can rarely cause postural headache, the mechanism of which remains unknown. Case Description: We present a 40-year-old woman with an asymptomatic supracerebellar arachnoid cyst. Upright computed tomography (CT) showed enlargement of the arachnoid cyst and caudal descent of the cerebellum compared with supine CT with narrowing of the craniocervical junction cerebrospinal fluid space. Conclusions: This finding aids in understanding the association of posterior fossa arachnoid cysts with orthostatic headache. Clinicians should be aware of possible posture-related changes in intracranial structures.

  • Outcomes of the Nuss procedure for pectus excavatum in adults

    Sakamoto Y., Yokoyama Y., Nagasao T., Yamada Y., Yamada M., Jinzaki M., Kishi K.

    Journal of Plastic, Reconstructive and Aesthetic Surgery (Journal of Plastic, Reconstructive and Aesthetic Surgery)   2021

    ISSN  17486815

     View Summary

    Limited data exist with regard to the outcome of the Nuss procedure for pectus excavatum repair in adults. Here, we analysed changes in lung capacity and thoracic morphology based on computed tomography (CT) imaging in adults with pectus excavatum before surgery, during bar insertion and after bar removal. Patients who underwent the Nuss procedure for pectus excavatum after the age of 20 were included in this study. Chest CT scans of the included participants were taken before the Nuss procedure, immediately before removal of the pectus bar and 6 months after removal of the pectus bar. Lung capacity and thoracic morphology measurements were made from the CT scans. Six patients aged 24–43 years were included in this study. After the Nuss procedure, lung capacity was decreased in all patients. Although the pectus bar was removed, lung capacity had not significantly increased and was almost the same volume as before the Nuss procedure. After the Nuss procedure, the funnel chest shape had improved in all cases, patients’ thoracic spine had also moved forward as the thorax moved forward and patients’ stoop had improved. Despite a lack of change in lung capacity, surgical modification should be considered to reduce stress on the thoracic spine and in turn, reduce pain in patients with pectus excavatum. However, further long-term observation seems necessary.

display all >>

Reviews, Commentaries, etc. 【 Display / hide

Research Projects of Competitive Funds, etc. 【 Display / hide

  • Elucidation of the pathology of pelvic floor dysfunction and urinary dysfunction using upright Computed Tomography


    若手研究, Principal investigator

Awards 【 Display / hide

  • Certificate of Merit

    Yoichi Yokoyama, Yoshitake Yamada, Minoru Yamada, Keiichi Narita, Takehiro Nakahara, Takeo Nagura, Masahiro Jinzaki, 2020.12, Radiological Society of North America, Upright CT with Area Detectors for Whole-Body Scans: Performance and Visualization of the Effects of Gravity on Human

    Type of Award: International academic award (Japan or overseas)