A high-resolution transrectal ultrasonographic system

The design of a transrectal echographical ultrasound system is described in this paper. This system produces high-quality, gray-scale images of the prostate, seminal vesicles and the bladder. A light, hand-held probe is inserted into the rectum. The probe is covered with a thin latex sheath which is filled with water to obtain excellent acoustic coupling with the wall of the rectum. The transducer, which is placed in the tip, rotates continuously, and this generates an ultrasound beam at 90° to the probe. A balanced arm can be coupled to the probe during this procedure to obtain better position stability and patient comfort. The transducer can be detached. Most of the work has been done for a 5 MHz transducer, but sometimes a 3.5 MHz transducer is used for greater penetration (≈ 9 cm).The transmitting and receiving systems contain unusual circuits. This includes a novel high-voltage pulser that generates the ultrasound pulse, and a simple but flexible variable time-gain control that adjusts the gain in echoes from different depths. A unique gray-scale phantom, that contains a mixture of lossy gel and reflecting objects, has been used routinely to check the performance of the transrectal scanner. This help is achieving excellent images of the prostate and seminal vesicles.