Electromagnetic waves from the lower radio frequencies up through the optical spectrum can generate a myriad of effects and responses in biological specimens. Some of these effects can be harmful to man at high radiation intensities, producing burns, cataracts, chemical changes, etc. Biological effects have been reported at lower radiation intensities, but it is not now known if lowlevel effects are harmful. Even behavioral changes have been reported. Most of the effects are not harmful under controlled conditions, and can thereby be used for therapeutic purposes and to make useful diagnostic measurements. The problem of microwave penetration into the body with resultant internal power absorption is a p proached from both the theoretical and the experimental viewpoints. The results are discussed in terms of therapeutic warming of tissues and possible hazards caused by internal "hot spots." The absorption and scattering effects of light in biological tissues are reviewed. Molecular absorption peaks in the optical spectrum are useful for making molecular concentration measurements by spectroscopy. Much of the related work in the literature is summarized, some new results are presented, and several useful applications of wave energy and medical instruments are di scussed. Mi I. INTRODUCTION EALTH OFFICIALS and medical personnel have recently been confronted with several problems associated with wave propagation effects in tissues and living systems such as man. They have turned to the engineering profession for help, but have found engineers generally unable to provide the needed guidance. Physiologists and biologists have attempted to fill this void, with results that clearly demand an informed engineering critique. I t seems curious indeed that although some of the early fundamental experiments with light and electromagnetic waves were performed over 100 years ago, the application of these energy forms to man himself is pitifully inadequate. This .paper is presented in an attempt to define the overall problem in some small measure, and illustrate the new applications methodology and techniques. It quite frankly represents an attempt to stimulate the engineering profession to respond to this urgent medical and social need. The paper consists of two basic parts. Section I1 describes electromagnetic radiation from, say, 1 MHz to 300 GHz, where the wavelength is large compared to cell sizes. There is little scattering, thus most of the wave reflection and transmission line concepts are applicable. Section I11 describes invited paper is om of a series planned on tap& of general inUTest-Tk Manuscript received February 24, 1972; revised March 20, 1972. This E d h. Facilities and administrative supporf for the research described were provided by Social Rehabilitation Service Research and Training Grant l&P-56818/0-09; Bureau of Radiological Health Grant 8-R01

The second edition of the Radiofrequency Radiation Dosimetry Handbook extends the data contained in the first edition, which was published by the United States Air Force School of Aerospace Medicine in September 1976 [Johnson et ai., 1976]. Several additional techniques have been used to extend the frequency range over which the specific absorption rate or mass-normalized rate of energy absorption (SAR)is calculated for models of human beings and animals, which results in useful theoretical data over the frequency range 10 kHz to 100 GHz. Some information is also given about ground-plane effects, experimental data found in the literature, and thermal effects of irradiation.

Crisis cards serve both a 'manifest', practical function (to provide important information when the patient is too ill to do so) and a 'latent' psychological one (positive effects on the patient's attitude to self, their illness and treatment, and their relationship with the clinical team).

The scattering and absorption of light by randomly oriented, discretely scattering, red blood cells imbedded in a homogeneous plasma medium can be described by the P1 approximation to the one-speed transport equation, where the cells have the dual role of anisotropic sources for first scattering events and of scattering and absorption sites for subsequent scattering events. Equations for diffuse reflectance defined for a finite size receiver in the plane of a normally incident cylindrical photon beam are derived and compared with experimental data to fundamentally justify the basic sending-receiving characteristics of a fiber optic catheter model. A model of the fiber optic catheter used for the spectrophotometric measurement of oxygen content in blood is developed from the theory and compared with experimental results to further substantiate the theoretical approach.

An air monitoring system incorporating this absorbent was readily constructed by simple modification of a common FID hydrocarbon monitor, with addition of a commercially available valve oven, switching valve, and timer. This system, except for the adjusted response time, had virtually the same operating specifications as the original hydrocarbon analyzer. Short-term studies indicated the system was practical, reliable, and accurate. Air-monitoring data obtained for Cincinnati indicated that the method could provide significant new information about air quality. LITERATURE CITED