# Studying Hardness Meter Spring Strength to Understand Hardness Distribution on Body Surfaces

• Arima, Yoshitaka (Department of Acupuncture and Moxibustion Therapy, Faculty of Health Promotional Sciences, Tokoha University)
Introduction: For developing a hardness multipoint measurement system for understanding hardness distribution on biological body surfaces, we investigated the spring strength of the contact portion main axis of a biological tissue hardness meter (product name: PEK). Methods: We measured the hardness of three-layered sheets of six types of gel sheets ($90mm{\times}60mm{\times}6mm$) constituting the acupuncture practice pads, with PEK measurements of 1.96 N, 2.94 N, 3.92 N, 4.90 N, 5.88 N, 6.86 N, 7.84 N, 8.82 N, and 9.81 N of the main axis spring strength. We obtained measurements 10 times for the gel sheets and simultaneously measured the load using a digital scale. We measured the hardness distribution of induration embedded and breast cancer palpation models, with a main axis with 1.96 N, 4.90 N, and 9.81 N spring strengths, to create a two-dimensional Contour Fill Chart. Results: Using 4.90 N spring strength, we could obtain measurement loads of ${\leq}3.0N$, and the mean hardness was 5.14 mm. This was close to the median of the total measurement range 0.0 -10.0 mm, making the measurement range the largest for this spring strength. We could image the induration of the induration-embedded model regardless of the spring strength. Conclusion: Overall, 4.90 N spring strength was best suited for imaging cancer in the breast cancer palpation model.