New aspects in assessment of changes in width of subarachnoid space with near-infrared transillumination/backscattering sounding, part 1: Monte Carlo numerical modeling

Abstract

A modified Monte Carlo method was used for numerical modeling of the propagation of near-infrared radiation (NIR) within the anatomical layers of the human head. The distribution of NIR transmission between particular anatomical layers in the measurement region (frontal tubers) of the head was obtained. The study demonstrates the effect of the cardiac pump function-dependent changes in the width of the subarachnoid space (SAS) on the intensity of the backscattered radiation. It was proved that the influence of this factor increases with increasing distance between the observation point and the location of the NIR source placed on the surface of the head. Moreover, with sufficiently small NIR detector-source distance, the contribution of the optic radiation propagated within the SAS to the total signal received is negligibly low, which gives a basis for estimation of the modulatory influence of blood circulation within the superficial skin layer on the total intensity of the backscattered radiation. The dimensions of anatomical layers used in the study are real values measured in a female patient, in whom--due to unique circumstances--it was possible to make measurements followed by recordings in clinical conditions, a situation essential for verification of the results of numerical modeling.

Subarachnoid Space: New Tricks by an Old Dog

“…Theoretical and practical foundations of the NIR-T/BSS method were provided in the earlier model studies [7], [8], [10], [11]. Briefly, the signal received by the DS is divided over the signal received by the PS.…”

“…This happens because only the DS receives the radiation propagated within the SAS. Propagation of IR in the skin and bone is much worse than in the clear, translucent CSF of the SAS, and with the DS placed far enough from the emitter, no radiation propagated in the superficial tissue layers can reach the DS [7], [8]. The power of the IR stream reaching the DS is directly proportional to the width of the SAS.…”

“…The power of the IR stream reaching the DS is directly proportional to the width of the SAS. The wider the SAS or the propagation duct, the more radiation reaches the DS and the greater the signal from that sensor, which is the dividend in the calculation of the TQ [7], [8].…”

“…Modulation of that harmonic is a fast-variable component (or cardiac component) of the principal, second and third harmonics of the cardiac component waveform, respectively. A detailed description of the method of signal analysis is presented in other papers [7], [8], [10], [11].…”

Use of optical skin phantoms for preclinical evaluation of laser efficiency for skin lesion therapy

“…1,2 Phantoms have known and controlled properties, which enable them to be used as calibration standards for testing and development of optical noninvasive diagnostic methods. [3][4][5][6][7] In the case of laser therapy, new devices require assessment of their therapeutic efficiency before they can be introduced into clinical practice. Such tests are commonly conducted on ex vivo tissues or on animals in vivo.…”