Time Resolved Spectroscopic (TRS) and Continuous Wave Spectroscopic (CWS) Studies of Photon Migration in Human Arms and Limbs

Abstract

The optical study of tissues began with the spectroscopic studies of Glenn Millikan in 1935 who proposed a “metabolic microscope” by which he would follow metabolic demand as expressed by the deoxygenation of myoglobin and hemoglobin in tissue. This was beautifully demonstrated in his studies of the cat soleus muscle during functional actvity (tetanic contraction and ischemia) (1). While the optical changes could be attributed to both hemoglobin and myoglobin, the demonstration of the effectiveness of the dual-wavelength technique using a differential detector and color filters was established in his pioneer studies. Applications to humans emerged in 1940 (2) with the “Millikan Oximeter” which was applied to the lobe of the ear, and using the same princiles, this presaged the popular “pulse oximeter” as applied to the human finger tip (3) Neither of these approaches presumed to provide intracranial homoglobinometry. Thus the results of Jöbsis-Vander Vleit and later Piantadosi on transcranial spectroscopy are noteworthy. They have evolved a much more sophisticated instrument which attempts to deconvolute cytochrome from hemoglobin and myoglobin changes in the exercising muscle (4,5). Such studies have been vexed by an unknown optical path requiring the need for either speculation or transfer of data from one model to another in abortive attempts to convert what has been termed justifiably a “trend indicator” to a quantitative spectroscopic technique.