Dual-slope method for enhanced depth sensitivity in diffuse optical spectroscopy

摘要

Using diffusion theory, we show that a dual-slope method is more effective than single-slope methods or single-distance methods at enhancing sensitivity to deeper tissue. The dual-slope method requires a minimum of two sources and two detectors arranged in specially configured arrays. In particular, we present diffusion theory results for a symmetrical linear array of two sources (separated by 55 mm) that sandwich two detectors (separated by 15 mm), for which dual slopes achieve maximal sensitivity at a depth of about 5 mm for direct current (DC) intensity (as measured in continuous-wave spectroscopy) and 11 mm for phase (as measured in frequency-domain spectroscopy) under typical values of the tissue optical properties (absorption coefficient: similar to 0.01 mm(-1), reduced scattering coefficient: similar to 1 mm(-1)). This result is a major advance over single-distance or single-slope data, which feature maximal sensitivity to shallow tissue (<2 mm for the intensity, <5 mm for the phase). (C) 2019 Optical Society of America