Decreased tendon stiffness is considered to be a factor in the progression of tendon injury, and research is ongoing to develop methods for quantitatively assessing tendon stiffness. Strain ratio (SR) measurement using the strain elastography function of an ultrasound diagnostic device can noninvasively measure the stiffness of living tissue based on the ratio of strain values between the acoustic coupler and the measured material, and thus can be used to assess the stiffness of tendons. However, the reliability of such measurements remains an issue. Therefore, the purpose of this study was to clarify the influence of preloading on the SR measurement of a phantom mimicking a tendon with decreased stiffness. Independent inclusions with stiffness values of 100, 200, and 400 kPa were placed in the phantom and measured. Preloading was set to 0.5, 1.0, and 1.5N, and the SR was measured by applying an mechanically controlled additional load of 3.0N. Taking the average of three measurements for each inclusion as a representative value, three sets of measurements were performed on different days for each preloading condition. The intraclass correlation coefficient (ICC) was used to examine the intra-observer reliability between days. In addition, the SR among preloading conditions was compared. ICC (1, 1) was 0.99 for all preloading conditions, indicating excellent reliability. The comparison among preloading conditions showed that the SR significantly decreased at a preloading of 1.5N compared with 0.5N for all inclusions. These results suggest the importance of controlling preloading during SR measurements.

Carbonated beverage-based sensory stimulation affects swallowing movements and contributes to safe swallowing. Although the effects of carbonated beverages on swallowing movements have been reported using swallowing sounds, small amounts of swallowing have not been investigated. In this study, we extracted the acoustic characteristics from swallowing sounds acquired when 15 healthy adults swallowed 3mL, 5mL, and 10mL of water or carbonated water five times each. Consequently, we confirmed that the acoustic features of the swallowing sound in time domain, i.e., peak intensity and energy, marginally significantly reduced when swallowing carbonated water compared to water, regardless of the quantity. Even with a mouthful volume of 3mL of carbonated water, this trend was confirmed. Therefore, the potential evaluation of swallowing and rehabilitation through the swallowing of small amounts of carbonated water, which has a lower risk of aspiration for dysphagia, was considered.

Electromagnetic waves below 3000THz (1THz=10¹²Hz) are called “non-ionizing radiation,” while those below 300GHz are commonly referred to as “radiofrequency (RF) waves” (but are defined by the Radio Law of Japan as electromagnetic waves with frequency spectra from 10kHz to 3000GHz) . The primary effect of RF waves on human physiology is acute, resulting from the heat-generating effect of induced currents within the body. The magnitude of this effect correlates with the RF wave strength when the biological threshold is exceeded, but there is no cumulative effect for exposure to radio waves below the threshold. This concept is analogous to the acute effects (non-probabilistic effects) of ionizing radiation, based on the hypothesis that weak radio waves do not cause late effects (probabilistic effects) in humans. This review paper provides an overview of the bioeffects of electromagnetic waves on humans from an electrical engineering perspective, followed by a comparison of Japan’s guidelines with international safety standards for human protection from radio waves, focusing on the heat-generating effects of RF waves, along with the underlying principle and rationale behind safety limits and protection guidelines for whole-body exposure to radio waves.