Application of MRSI (Magnetic Resonance Spectroscopic Imaging) for proton chemical shift to noninvasive medical thermometry was studied theoretically and experimentally. In vitro experiments using a 9.4T spectrometer clarified that a proton chemical shift between water (-OH) proton and fat (-CH₂-) proton in each bovine organ such as tissue flap of muscle, liver, stomach wall, large intestinal wall and heart muscle is inversely proportional to temperature; The chemical shift between water and fat peak varied quite linearly about from 3.4ppm to 3.2ppm depending on tissue temperature in the range of 300K (27°C) to 318K (45°C) showing tissue insensitivities. For temperature imaging, multivoxel proton spectroscopy techniques are theoretically available. Development of a suitable multivoxel spectroscopy method for the thermometry and investigations about biological reactions including influence of pH are necessary.

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We have measured magnetic fields and electrical potentials evoked on the scalp by auditory stimuli of a pure tone and a short speech sound. As the inter-stimulus interval was decreased from 1, 400 to 200ms, the amplitude of the field and potential responses decreased, where the response to the speech severely changed in waveform at short intervals. As proved by computer simulations, these changes can not be explained by simple superposition of waveforms of successive responses. We have also studied the change of the response when the subject directed selective attention to either the tone or speech given at short intervals of 200-300ms. The attention-related shift was clearly observed in the potential response in a manner that depended on the sequence of the response-evoking and its preceding stimuli, where the stimuli-sequence dependence was quite different from that previously obtained in the measurement at long stimulus intervals. Assuming the superposition of successive responses, the observed stimuli-sequence dependence was interpreted as derived from that at long stimulus intervals.

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Many testing methods of equilibrium function have been proposed to make a diagnosis of vertigo up to now. However, nobody has noticed that the vertigo might be evaluated based on the phenomena of “induced motion”. We have found that the level of induced motion changes when the equilibrium function is disturbed. The possibility of the diagnosis using the induced motion phenomena is discussed in this paper. A moving ellipse pattern and a fixed point inside the ellipse were displayed in a dark room using laser beams. When the ellipse moves left and right sinusoidally, the fixed point is perceived to move in the opposite phase to the ellipse motion. This phenomena is called induced motion. We have ascertained that the level of induced motion increased when a normal subject became vertigo by caloric stimulation. This result anticipates that vertigo can be evaluated by using the level of induced motion. The comparative experiment was administered between 50 normal subjects and 17 vertigo patients who could not be detected by conventional eye movement test. The level of induced motion was measured by changing the amplitude of a moving point for the subjects to perceive the point to be fixed. We difined the value of induced motion (VIM) to the ratio of the amplitude of the moving point to that of the moving ellipse. From the experimental result, significant difference was found statistically between VIM of patients and that of normal subjects. Though the reason why the patients showed larger VIM than normal subjects is not clear, our method using the induced motion phenomena will become one of testing methods of vertigo. Especially, it is useful for the diagnosis of patients who can not be detected by conventional method using the eye movement measurement.

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The efficiency of the vascular-tissue system of mammals for oxygen supply to body tissue was estimated employing the spherical model for the capillary-tissue arrangement. In this model, a whole body consists of uniform tissue spheres with a sigle capillary in each center. The tissue mass of each sphere was calculated as the region of positive O₂ tension. Total tissue mass was determined as the function of the capillary number (n) with parameters of total blood flow (F₀) and tissue O₂ consumption rate (q_O2). The energy cost to maintain the vascular system with n terminals (capillaries) was assessed with the minimum volume model proposed by Kamiya and Togawa (1972). The efficiency of the entire system was defined as the ratio of (total tissue mass) or (total O₂ consumption)/(the energy cost). Using physiological data of F₀ and q_O2 in various mammals with body weights from 200g to a ton, the efficiency was calculated to determine the optimum capillary numbers and density in each animal. The results indicated that the total tissue mass corresponding to the optimum capillary number during exercise well agreed with the actual body mass in every animal and that the efficiency and the capillary blood flow (F_c) in such a state are almost invariable, irrespective of difference in species. From these results, it was suspected that there must exist a common design principle in mammals supported with a biological mechanism constructing and regulating the capillary-tissue system so that F_c during exercise might be maintained at the optimum level.

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The ultrasonic attenuation (A_s) and the propagation velocity (V_s) in the human coronary artery (CA) intima were measured to evaluate the progression of atherosclerosis of CA wall using acoustic microscopy. We used an ultrasonic tissue characterization system with a scanning acoustic microscope (HSAM-500S, 450MHz). CA specimens were obtained by autopsy from 52 patients and cut into rings 4 microns thick. Based on the pathological findings in the intima with an optical microscope, we classified them into 3 groups: normal (21 specimens), early stages of sclerosis (24 specimens), and advanced stages of sclerosis (7 specimens). The relationships between age and A_s, and age and V_s were not statistically significant. Significantly, A_s was lower in the early stage (1.7±0.6dB), and higher in the advanced stage (5.4±0.8dB) than in normal (2.5±0.5dB), while V_s was slower in the early stage (1, 611.9±53.0m/s), and faster in the advanced stage (2, 031.4±145.0m/s) than in normal (1, 757.8±90.4m/s). In summary, both A_s and V_s were not significantly affected by age, but were mainly influenced by pathological atherosclerotic change. In addition, both parameters showed non-linear change as compared with the optical findings of CA. Because PV is proportional to the square root of the elastic modules, A_s is faster in harder tissue. We therefore concluded that CA intima in optically defined early stages of disease showed an initial softening as compared with normal tissue, and this was followed by increasing hardening in the advanced stage as a result of progressing fibrosis and calcification.

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