Test-retest assessment of cortical activation induced by repetitive transcranial magnetic stimulation with brain atlas-guided optical topography

Abstract

Repetitive transcranial magnetic stimulation (rTMS) is a technology that stimulates neurons with rapidly changing magnetic pulses with demonstrated therapeutic applications for various neuropsychiatric disorders. Functional near-infrared spectroscopy (fNIRS) is a suitable tool to assess rTMS-evoked brain responses without interference from the magnetic or electric fields generated by the TMS coil. We have previously reported a channel-wise study of combined rTMS/fNIRS on the motor and prefrontal cortices, showing a robust decrease of oxygenated hemoglobin concentration (Δ[HbO2]) at the sites of 1-Hz rTMS and the contralateral brain regions. However, the reliability of this putative clinical tool is unknown. In this study, we develop a rapid optical topography approach to spatially characterize the rTMS-evoked hemodynamic responses on a standard brain atlas. A hemispherical approximation of the brain is employed to convert the three-dimensional topography on the complex brain surface to a two-dimensional topography in the spherical coordinate system. The test-retest reliability of the combined rTMS/fNIRS is assessed using repeated measurements performed two to three days apart. The results demonstrate that the Δ[HbO2] amplitudes have moderate-to-high reliability at the group level; and the spatial patterns of the topographic images have high reproducibility in size and a moderate degree of overlap at the individual level.

Prefrontal hemodynamic mapping by functional near-infrared spectroscopy in response to thermal stimulations over three body sites

“…32 It overlays 2-D images of HbO or Hb activations/ deactivations over a standard human brain MRI atlas after 2-D angular interpolation of the channel-wise activation data in a spherical-coordinate system. The channel-wise β-values derived from GLM analysis, and t-values from subsequent statistical comparisons were used to generate activation maps (i.e., β-maps and t-maps) induced by thermal stimulation over different body sites.…”

“…These cranial landmarks served as reference positions to convert the realworld stereotaxic coordinates of the optodes to the Montreal Neurological Institute (MNI) coordinates used in a standard brain MRI atlas, based on the affine transformation. 32 Using NIRS-SPM software, 33 each of the Brodmann areas (BA) probed by the fNIRS optode array, and the respective percentage of covered BA over the entire area of the optode array, were identified. It was observed that the optode array mainly examined seven major Brodmann areas: BAs 6,8,9,10,44,45, and 46, all of which covered 97.42% of the area interrogated by the optode array.…”

Automated voxel classification used with atlas-guided diffuse optical tomography for assessment of functional brain networks in young and older adults

“…Such an automated classification is critical because it helps to extract and identify cerebral hemodynamic signals from appropriately matched anatomical locations, thus improving the accuracy of interpretations of local and global brain activities. Commonly used methods for registering NIRS data on a human brain template are often based on the EEG 10-20 system, [47][48][49] which is not directly applicable to the 3-D atlas-DOT images. In addition, routinely used voxel classification in fMRI is based on an affine transformation, which converts the voxel space to MNI space, followed by a voxel matching with a standard MNI structure template.…”

Tutorial on use of intraclass correlation coefficients for assessing intertest reliability and its application in functional near-infrared spectroscopy–based brain imaging

“…Usually both of the metrics are used to quantify the reliability of measurements. 5,8,9,11 This will provide important information on the effect of repeated testing on intertest reliability and will help make a decision on how many tests are needed. Taking the calculated ICC values in Table 7 as an example, ICCð2;1Þ ¼ 0.61 and ICCð2;2Þ ¼ 0.76 in the win case.…”