Testing Diagnostic Ultrasound Probes For Bad Crystals
by: Kevin C. Carpenter, CBET
Here is a quick technique to test the linear array transducer of a diagnostic ultrasound machine. This procedure assists in determining if a transducer has defective crystals.
Turn the US machine on and get setup to use the linear array transducer. Put a light coat of ultrasonic jelly on the face of the transducer. Next, take a thin metal rod (a thin screw driver shaft will work, the thinner the better) and place it perpendicularly on the face of the transducer. Now, slowly move the metal rod along the face of the transducer. While doing so watch the display on the US machine. A continuous fan of lines should appear on the display. Each line will fade in and out individually as the metal rod passes directly over the corresponding crystal. If a section of the transducer does not result in a line being displayed then the crystal at that location may be bad, or the send/receive circuitry for that channel may be defective.
A linear array ultrasound transducer is made up of a large number of crystals stacked side by side. The crystals emit an ultrasonic wave and then listen for the wave to be reflected back to them. Passing a metal rod along the surface of the transducer reflects the ultrasonic wave immediately back into the crystal that just generated it and, if that crystal is working properly, a line appears on the display.
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This page was published on 9/19/98