Instrumentation for Ultrasound Biomicroscopy

Abstract

The essential component blocks of an ultrasound biomicroscope are identical to those of a conventional B-mode imaging system except that the operating frequency is approximately an order of magnitude higher. Achieving the goal of real time B-mode imaging at these frequencies required development of new technology in three important areas: (1) transducers, (2) high-frequency signal processing, and (3) precise motion control. Figure 2.1 shows a block diagram of the principal components of an ultrasound biomicroscope. A 40 to 100 MHz transducer is moved linearly over the imaging field (typically 4 mm), collecting radiofrequency ultrasound data at each of 512 equally spaced lines (8 µm between lines). A monocycle high voltage (200 V peak to peak) 40 to 100 MHz pulse is used to excite the transducer. The resulting 40 to 100 MHz ultrasound pulse is transmitted into the tissue and the backscattered ultrasound is detected by the same transducer. The radiofrequency signal (see Figure 1.10b) is received and amplified in proportion to the depth from which it originated using time-gain compensation (TGC), as shown in Figure 2.1.