title: Correlation of the near-infrared spectroscopy signals with signal intensity in T(2)-weighted magnetic resonance imaging of the human masseter muscle.
abstract: The purpose of this study was to compare and contrast blood volume changes transcutaneously measured using near-infrared (NIR) spectroscopy against water signal intensity changes taken from a transverse T(2)-weighted MR image of the masseter muscle in healthy human subjects before, during and after contraction. Eight healthy non-smoking males with no history of chronic muscle pain or vascular headaches participated (mean age: 23.9+/-0.6 years). The MRI data were gathered using a turbo spin echo sequence (TR: 2300 ms; TE: 90 ms; FOV: 188x300 mm; scanning time: 30 s; slice thickness: 10 mm) and the slice level was set at the mid-point between the origin and insertion of the masseter. Intramuscular haemoglobin (Hb) levels and water content of the right masseter muscle were continuously monitored for 2 min before, 30 s during and 15 min after a maximum voluntary clenching (MVC) task. Both the near-infrared and MRI data were baseline-corrected and normalized and mean levels were established and plotted. Plots of the data showed that both near-infrared-based total Hb and T(2)-weighted MRI-based signal-intensity levels clearly decreased during contraction and a clear post-contraction rebound response was evident after the contraction. The near-infrared data were found to be highly correlated with MRI-based signal-intensity data (Pearson's r=0.909, P<0.0001). In conclusion, these data provide powerful evidence that near-infrared data (total Hb), transcutaneously taken from the masseter muscle in humans, will reflect the intramuscular water signal intensity changes seen using a T(2)-weighted MRI imaging method.
authors.affiliation: Department of Fixed Prosthodontics, Okayama University Dental School, 2-5-1 Shikata-cho, 700-8525, Okayama, Japan. kuboki@dent.okayama-u.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Kuboki
authors.forename: K
authors.initials: K
authors.lastname: Suzuki
authors.forename: K
authors.initials: K
authors.lastname: Maekawa
authors.forename: M
authors.initials: M
authors.lastname: Inoue-Minakuchi
authors.forename: C O
authors.initials: CO
authors.lastname: Acero
authors.forename: Y
authors.initials: Y
authors.lastname: Yanagi
authors.forename: T
authors.initials: T
authors.lastname: Wakasa
authors.forename: K
authors.initials: K
authors.lastname: Kishi
authors.forename: H
authors.initials: H
authors.lastname: Yatani
authors.forename: G T
authors.initials: GT
authors.lastname: Clark
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001810:Blood Volume / Q000502:physiology*; D001834:Body Water / Q000737:chemistry; D002138:Calibration; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008406:Masseter Muscle / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology; D012815:Signal Processing, Computer-Assisted; D019265:Spectroscopy, Near-Infrared; D013223:Statistics as Topic
chemical_list: D006454:Hemoglobins