This paper describes our newly designed scanning acoustic microscope (SAM). Our concern is to determine the mechanical properties of each histological component of the vocal fold in normal and varying pathological states.
Generally speaking, the images obtained by means of an acoustic microscope not only present structure of the object to be investigated but also reflect its mechanical properties. Our present SAM has the following features.
1) The frequency of ultrasonic waves is variable between 100 and 200 MHz. The best resolution is about 5μm(at 200MHz).
2) This single device can function as three different types of SAM: i. e. reflection-, transmission-, and interference-type.
3) Linear and logarithmic conversions of the image intensity are available. The range of the intensity covered by linear conversion is about 20dB, whereas, by logarithmic conversion, it is about 40dB.
4) Tilting mechanism is installed to the sample bed so as to adjust the angle of specimen to be parallel to focal plane of the acoustic lens.
5) As far as one direction is concerned, consecutive images are obtained easily by simply pushing a button.
6) The image stored in the digital memory can be recorded by an ordinary video recorder.
Also, as concerns the reflected image, a brief explanation of the preparation of the specimen and the operation of the device are presented.
In Discussion, several advantages of the acoustic image compared with the optical image are mentioned. Then, a method of quantifying the mechanical property of biological tissues based on the acoustic image is briefly explained. A preliminary result on the vocal fold tissue shows that the 'hardness' increases in the order of the ground substance, the epithelium, and the fibrous components (a mixture of elastic and collagenous fibers).