title: Multi-subject and multi-task experimental validation of the hierarchical Bayesian diffuse optical tomography algorithm.
abstract: Diffuse optical tomography (DOT) is an emerging technology for improving the spatial resolution and spatial specificity of conventional multi-channel near-infrared spectroscopy (NIRS) by the use of high-density measurements and an image reconstruction algorithm. We recently proposed a hierarchical Bayesian DOT algorithm that allows for accurate simultaneous reconstruction of scalp and cortical hemodynamic changes, and verified its performance with a phantom experiment, a computer simulation, and experimental data from one human subject. We extend our previous human case study to a multi-subject, multi-task study, to demonstrate the validity of the algorithm on a wider population and varied task conditions. We measured brain activity during three graded tasks (hand movement, index finger movement, and no-movement), in 12 subjects, using high-density NIRS and functional magnetic resonance imaging (fMRI), acquired in different sessions. The reconstruction performance of our algorithm, and the current gold-standard method for DOT image reconstruction, were evaluated using the blood-oxygenation-level-dependent (BOLD) signals of the fMRI as a reference. In comparison with the BOLD signals, our method achieved a median localization error of 6 and 8mm, and a spatial-pattern similarity of 0.6 and 0.4 for the hand and finger tasks, respectively. It also did not reconstruct any activity in the no-movement task. Compared with the current gold-standard method, the new method showed fewer false positives, which resulted in improved spatial-pattern similarity, although the localization errors of the main activity clusters were comparable.
authors.affiliation: Neural Information Analysis Laboratories, ATR, 2-2-2 Hikaridai, Keihanna Science City, Kyoto 619-0288, Japan; Brain Functional Imaging Technologies Group, CiNet, 1-4 Yamadaoka, Suita City, Osaka 565-0871, Japan. Electronic address: oyamashi@atr.jp.
authors.forename: Okito
authors.initials: O
authors.lastname: Yamashita
authors.affiliation: Neural Information Analysis Laboratories, ATR, 2-2-2 Hikaridai, Keihanna Science City, Kyoto 619-0288, Japan.
authors.forename: Takeaki
authors.initials: T
authors.lastname: Shimokawa
authors.affiliation: Neural Information Analysis Laboratories, ATR, 2-2-2 Hikaridai, Keihanna Science City, Kyoto 619-0288, Japan; Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan.
authors.forename: Ryota
authors.initials: R
authors.lastname: Aisu
authors.affiliation: Medical Systems Division Research and Development Department, Shimadzu Corporation, 1 Nishinokyo-Kuwabaracho, Nakagyo-ku, Kyoto 604-8511, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Amita
authors.affiliation: Medical Systems Division Research and Development Department, Shimadzu Corporation, 1 Nishinokyo-Kuwabaracho, Nakagyo-ku, Kyoto 604-8511, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Inoue
authors.affiliation: Neural Information Analysis Laboratories, ATR, 2-2-2 Hikaridai, Keihanna Science City, Kyoto 619-0288, Japan.
authors.forename: Masa-Aki
authors.initials: MA
authors.lastname: Sato
mesh_terms: D000328:Adult; D000465:Algorithms; D001499:Bayes Theorem; D001931:Brain Mapping / Q000379:methods*; D019054:Evoked Potentials, Motor / Q000502:physiology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D009068:Movement / Q000502:physiology; D010363:Pattern Recognition, Automated / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D041622:Tomography, Optical / Q000379:methods*; D055815:Young Adult
keywords: Diffuse optical tomography; Image reconstruction; NIRS; Scalp blood flow