title: Sensitivity correction for the influence of the fat layer on muscle oxygenation and estimation of fat thickness by time-resolved spectroscopy.
abstract: Near-infrared spectroscopy (NIRS) has been used for noninvasive assessment of oxygenation in living tissue. For muscle measurements by NIRS, the measurement sensitivity to muscle (S(M)) is strongly influenced by fat thickness (FT). In this study, we investigated the influence of FT and developed a correction curve for S(M) with an optode distance (3 cm) sufficiently large to probe the muscle. First, we measured the hemoglobin concentration in the forearm (n=36) and thigh (n=6) during arterial occlusion using a time-resolved spectroscopy (TRS) system, and then FT was measured by ultrasound. The correction curve was derived from the ratio of partial mean optical path length of the muscle layer 〈L(M)〉 to observed mean optical path length 〈L〉. There was good correlation between FT and 〈L〉 at rest, and 〈L〉 could be used to estimate FT. The estimated FT was used to validate the correction curve by measuring the forearm blood flow (FBF) by strain-gauge plethysmography (SGP_FBF) and TRS (TRS_FBF) simultaneously during a reactive hyperemia test with 16 volunteers. The corrected TRS_FBF results were similar to the SGP_FBF results. This is a simple method for sensitivity correction that does not require use of ultrasound.
authors.affiliation: Hamamatsu Photonics K.K., Central Research Laboratory, 5000 Hirakuchi, Hamakita-ku, Hamamatsu, Shizuoka 434-8601, Japan.
authors.forename: Etsuko
authors.initials: E
authors.lastname: Ohmae
authors.affiliation: Hamamatsu University School of Medicine, Department of Clinical Pharmacology and Therapeutics, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan.
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Nishio
authors.affiliation: Hamamatsu Photonics K.K., Central Research Laboratory, 5000 Hirakuchi, Hamakita-ku, Hamamatsu, Shizuoka 434-8601, Japan.
authors.forename: Motoki
authors.initials: M
authors.lastname: Oda
authors.affiliation: Hamamatsu Photonics K.K., Central Research Laboratory, 5000 Hirakuchi, Hamakita-ku, Hamamatsu, Shizuoka 434-8601, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Suzuki
authors.affiliation: Hamamatsu Photonics K.K., Central Research Laboratory, 5000 Hirakuchi, Hamakita-ku, Hamamatsu, Shizuoka 434-8601, Japan.
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Suzuki
authors.affiliation: Oita University Faculty of Medicine, Department of Clinical Pharmacology and Therapeutics, 1-1 Idaigaoka, Hasama-machi, Yufu, Oita 879-5593, Japan.
authors.forename: Kyoichi
authors.initials: K
authors.lastname: Ohashi
authors.affiliation: Kobe Design University, Applied Physiology Laboratory, 8-1-1 Gakuennishi-machi, Nishi-ku, Kobe 651-2196, Japan.
authors.forename: Shunsaku
authors.initials: S
authors.lastname: Koga
authors.affiliation: Hamamatsu Photonics K.K., Central Research Laboratory, 5000 Hirakuchi, Hamakita-ku, Hamamatsu, Shizuoka 434-8601, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Yamashita
authors.affiliation: Hamamatsu University School of Medicine, Department of Clinical Pharmacology and Therapeutics, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Watanabe
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology*; D000328:Adult; D005260:Female; D005542:Forearm / Q000098:blood supply*; D006454:Hemoglobins / Q000737:chemistry; D006801:Humans; D006940:Hyperemia; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000098:blood supply*; D010100:Oxygen / Q000737:chemistry; D052097:Quadriceps Muscle / Q000473:pathology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D013848:Thigh / Q000098:blood supply*; D014867:Water / Q000737:chemistry; D055815:Young Adult
chemical_list: D006454:Hemoglobins; D014867:Water; D010100:Oxygen