Abstract
.Significance: High density diffuse optical tomography (HD-DOT) as applied in functional near-infrared spectroscopy (fNIRS) is largely limited to continuous wave (CW) data. Using a single modulation frequency, frequency domain (FD) HD-DOT has recently demonstrated better localization of focal activation as compared to CW data. We show that combining CW and FD measurements and multiple modulation frequencies increases imaging performance in fNIRS.Aim: We evaluate the benefits of multiple modulation frequencies, combining different frequencies as well as CW data in fNIRS HD-DOT.Approach: A layered model was used, with activation occurring within a cortex layer. CW and FD measurements were simulated at 78, 141, and 203 MHz with and without noise. The localization error, full width half maximum, and effective resolution were evaluated.Results: Across the average of the three metrics, at 141 MHz, FD performed 8.4% better than CW, and the combination of CW and FD was 21.7% better than CW. FD measurements at 203 MHz performed 5% better than 78 MHz. Moreover, the three combined modulation frequencies of FD and CW performed up to 3.92% better than 141 MHz alone.Conclusions: We show that combining CW and FD measurements offers better performance than FD alone, with higher modulation frequencies increasing accuracy. Combining CW and FD measurements at multiple modulation frequencies yields the best overall performance.
Highlights
Functional near-infrared spectroscopy is a medical imaging modality that can be used to monitor and diagnose many different pathologies within the brain
The combined continuous wave (CW) and frequency domain (FD) measurement for localization error (LOCA) results in a more uniform central region than either CW or FD, as well as less artifacts around the edge of the field of view (FOV). This is seen on the left- and right-hand side of the FOV. It is only in the CW case that the LOCA dramatically increase to a maximum of 5.55 mm in the corners
This work is consistent with previous studies showing that CW and FD data offer significantly better imaging performance than CW alone as applied in Functional near-infrared spectroscopy (fNIRS) and High density diffuse optical tomography (HD-DOT)
Summary
Functional near-infrared spectroscopy (fNIRS) is a medical imaging modality that can be used to monitor and diagnose many different pathologies within the brain. FNIRS uses sparse arrays of sources and detectors to recover spectroscopic information, which are often used with simplistic models based on the Beer–Lambert Law to derive the bulk concentration of a chromophore, typically oxy and deoxy hemoglobin.[8] Using a high density grid of sources and detectors, tomographic image recovery of spatial distributions of optical properties has been shown to provide maps of localized concentration of these chromophores, which for functional cerebral imaging is known to be highly useful.[9,10]
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