Acoustic impedance microscopy for biological tissue characterization.
A new method for two-dimensional acoustic impedance imaging for biological tissue characterization with micro-scale resolution was proposed. A biological tissue was placed on a plastic substrate with a thickness of 0.5mm. A focused acoustic pulse with a wide frequency band was irradiated from the "rear side" of the substrate. In order to generate the acoustic wave, an electric pulse with two nanoseconds in width was applied to a PVDF-TrFE type transducer. The component of echo intensity at an appropriate frequency was extracted from the signal received at the same transducer, by performing a time-frequency domain analysis. The spectrum intensity was interpreted into local acoustic impedance of the target tissue. The acoustic impedance of the substrate was carefully assessed prior to the measurement, since it strongly affects the echo intensity. In addition, a calibration was performed using a reference material of which acoustic impedance was known. The reference material was attached on the same substrate at different position in the field of view. An acoustic impedance microscopy with 200×200 pixels, its typical field of view being 2×2 mm, was obtained by scanning the transducer. The development of parallel fiber in cerebella cultures was clearly observed as the contrast in acoustic impedance, without staining the specimen. The technique is believed to be a powerful tool for biological tissue characterization, as no staining nor slicing is required.
Honda Electronics Co., Ltd., 20 Koyamazuka, Oiwa-cho, Toyohashi 441-3193, Japan. Electronic address: kazuto@honda-el.co.jp.
Kazuto
K
Kobayashi
Toyohashi University of Technology, 1-1 Tempaku, Toyohashi 441-8580, Japan.
Sachiko
S
Yoshida
Tohoku University, 6-6 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan.
Yoshifumi
Y
Saijo
Aichi Institute of Technology, 1247 Yachigusa, Yakusa, Toyota 470-0392, Japan.
Naohiro
N
Hozumi
D000158:Acoustic Impedance Tests / Q000379:methods*; D000818:Animals; D002138:Calibration; D002531:Cerebellum / Q000648:ultrastructure*; D004867:Equipment Design; D033401:Microscopy, Acoustic; D051381:Rats; D014159:Transducers
Acoustic impedance; Acoustic microscope; Tissue characterization