Methodical Notes on the Term “Intensity” in Medicine and Physics

Abstract

In the article, as a discussion of the publication [1] published earlier in the journal on terminology in
 medical physics, the application of the term intensity in medicine and physics is considered. It is
 shown, contrary to the statement of the original article, that the term intensity is very widely used in
 various branches of physics, from optics and photometry to electrodynamics and radiophysics. At the
 same time, its ambiguity and non-identity of the use in different branches of physics, including the different dimensions of these quantities used, which often introduces a confusion and leads to errors in
 results, is also shown and discussed. For optics and photometry, according to the recommendations of
 the international SI system, the term intensity should be unambiguously understood as a quantity
 with the dimension W·sr–1. This is the main physical quantity of the SI system that characterizes radiation, but in Russian-language publications it is also called as a force of radiation, which can be misleading.

Photoplethysmographic Imaging of Hemodynamics and Two-Dimensional Oximetry

“…This assumption explains why it is possible to obtain an PPGI signal even in the case when optical radiation does not penetrate to the depth of the location of the blood vessels. The depth of the light penetration into the skin for the PPGI in the reflection mode is really of little importance [ 35 ], while there are ambiguities in its definition [ 36 ].…”

“…(2) . During the production and adjustment of the oximeter, the parameter RR is calibrated (coefficients A and B ) as a percentage of the oxyhemoglobin saturation, determined by direct readings of gas analysis of blood samples, in the arterial blood (SaO 2 ) [ 36 ]. Thus, the value of the pulse saturation SpO 2 can be obtained by measuring RR and substituting the measured value into the calibration equation ( Eq.…”

“…The noninvasive oximetry method is considered in more detail in the lecture article by D.A. Rogatkin [ 36 ].…”