Optimizing a two-layer method for hybrid diffuse correlation spectroscopy and frequency-domain diffuse optical spectroscopy cerebral measurements in adults

• Published in: Neurophotonics (Print) Vol. 10; no. 2; p. 025008
• Main Authors: Forti, Rodrigo Menezes, Martins, Giovani Grisotti, Baker, Wesley Boehs, Mesquita, Rickson C.
• Format: Journal Article
• Language: English
• Published: United States Society of Photo-Optical Instrumentation Engineers 01.04.2023; SPIE; S P I E - International Society for
• Subjects: Adults; Algorithms; Analysis; Approximation; Blood flow; Cerebral blood flow; Geometry; Measurement; Methods; Optical properties; Optics; Research Papers; Sensors; Simulation; Spectroscopy; Spectrum analysis; multilayer model; hybrid diffuse optics; diffuse correlation spectroscopy; multidistance; diffuse optical spectroscopy
• ISSN: 2329-423X; 2329-4248; 2329-4248
• DOI: 10.1117/1.NPh.10.2.025008

The sensitivity to extracerebral tissues is a well-known confounder of diffuse optics. Two-layer (2L) head models can separate cerebral signals from extracerebral artifacts, but they also carry the risk of crosstalk between fitting parameters. We aim to implement a constrained 2L head model for hybrid diffuse correlation spectroscopy (DCS) and frequency-domain diffuse optical spectroscopy (FD-DOS) data and to characterize errors in cerebral blood flow and tissue absorption with the proposed model. The algorithm uses the analytical solution of a 2L cylinder and an extracerebral layer thickness to fit multidistance FD-DOS (0.8 to 4 cm) and DCS (0.8 and 2.5 cm) data, assuming homogeneous tissue reduced scattering. We characterized the algorithm's accuracy for simulated data with noise generated using a 2L slab and realistic adult head geometries and for phantom data. Our algorithm recovered the cerebral flow index with 6.3 [2.8, 13.2]% and 34 [30, 42]% (median absolute percent error [interquartile range]) for slab and head geometries, respectively. Corresponding errors in the cerebral absorption coefficient were 5.0 [3.0, 7.9]% and 4.6 [2.4, 7.2]% for the slab and head geometries and 8 [5, 12]% for our phantom experiment. Our results were minimally sensitive to second-layer scattering changes and were robust to cross-talk between fitting parameters. In adults, the constrained 2L algorithm promises to improve FD-DOS/DCS accuracy compared with the conventional semi-infinite approach.