Surface density mapping of natural tissue by a scanning haptic microscope (SHM).
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.
Division of Medical Engineering and Materials, National Cerebral and Cardiovascular Center Research Institute, Fujishiro-dai, Osaka, Japan.
Takeshi
T
Moriwaki
Tomonori
T
Oie
Keiichi
K
Takamizawa
Yoshinobu
Y
Murayama
Toru
T
Fukuda
Sadao
S
Omata
Yasuhide
Y
Nakayama
D000362:Agar / Q000737:chemistry; D000818:Animals; D001011:Aorta / Q000737:chemistry*; D004285:Dogs; D055119:Elastic Modulus; D020100:Hydrogels / Q000737:chemistry; D008853:Microscopy / Q000379:methods*; D012828:Silicones / Q000737:chemistry; D013499:Surface Properties
D020100:Hydrogels; D012828:Silicones; D000362:Agar