Moriwaki Takeshi, Oie Tomonori, Takamizawa Keiichi, Murayama Yoshinobu, Fukuda Toru, Omata Sadao, Nakayama Yasuhide
Division of Medical Engineering and Materials, National Cerebral and Cardiovascular Center Research Institute, Fujishiro-dai, Osaka, Japan.
J Med Eng Technol. 2013 Feb;37(2):96-101. doi: 10.3109/03091902.2012.747008.
To expand the performance capacity of the scanning haptic microscope (SHM) beyond surface mapping microscopy of elastic modulus or topography, surface density mapping of a natural tissue was performed by applying a measurement theory of SHM, in which a frequency change occurs upon contact of the sample surface with the SHM sensor - a microtactile sensor (MTS) that vibrates at a pre-determined constant oscillation frequency. This change was mainly stiffness-dependent at a low oscillation frequency and density-dependent at a high oscillation frequency. Two paragon examples with extremely different densities but similar macroscopic elastic moduli in the range of natural soft tissues were selected: one was agar hydrogels and the other silicon organogels with extremely low (less than 25 mg/cm(3)) and high densities (ca. 1300 mg/cm(3)), respectively. Measurements were performed in saline solution near the second-order resonance frequency, which led to the elastic modulus, and near the third-order resonance frequency. There was little difference in the frequency changes between the two resonance frequencies in agar gels. In contrast, in silicone gels, a large frequency change by MTS contact was observed near the third-order resonance frequency, indicating that the frequency change near the third-order resonance frequency reflected changes in both density and elastic modulus. Therefore, a density image of the canine aortic wall was subsequently obtained by subtracting the image observed near the second-order resonance frequency from that near the third-order resonance frequency. The elastin-rich region had a higher density than the collagen-rich region.
为了将扫描触觉显微镜（SHM）的性能扩展到弹性模量或形貌的表面映射显微镜之外，通过应用SHM的测量理论对天然组织进行表面密度映射，其中当样品表面与SHM传感器（一种以预定恒定振荡频率振动的微触觉传感器（MTS））接触时会发生频率变化。这种变化在低振荡频率下主要取决于刚度，在高振荡频率下取决于密度。选择了两个在天然软组织范围内密度差异极大但宏观弹性模量相似的典型例子：一个是琼脂水凝胶，另一个是密度极低（小于25mg/cm³）和极高（约1300mg/cm³）的硅有机凝胶。在接近二阶共振频率（这导致弹性模量）和接近三阶共振频率的盐溶液中进行测量。琼脂凝胶中两个共振频率之间的频率变化几乎没有差异。相反，在硅凝胶中，在接近三阶共振频率处观察到MTS接触引起的较大频率变化，表明接近三阶共振频率处的频率变化反映了密度和弹性模量的变化。因此，随后通过从接近三阶共振频率处观察到的图像中减去接近二阶共振频率处观察到的图像，获得了犬主动脉壁的密度图像。富含弹性蛋白的区域比富含胶原蛋白的区域具有更高的密度。
