Field Testing of Ultrasound Transducers
We often get questions regarding testing of transducers in the field; specifically how do you perform testing of transducer lenses, arrays, cables, connectors, and overall performance when performing repairs or preventative maintenance on-site. At our repair facility, we perform several tests that are difficult or impractical to do when in the field including a computer-generated platform of tests that electronically measure element sensitivity, cable capacitance, and overall performance as well as a clinical examination by our in-house registered sonographer to validate transducer performance from a clinical perspective.
There are several ways to field test a transducer with the first being an overall visual and mechanical inspection. Begin with the lens and check for nicks, cuts, gaps between the nosepiece and lens, or lens swelling.
Next, while watching the image (especially the near field), hold the scanhead by the strain relief and gently flex head at the strain relief and look for dropouts or noise being generated in the image. If you see either of these issues, you have one or more broken cables in the neck of the probe.
Moving down the cable, check for any nicks or cuts along the entire length. Now inspect the connector for any broken or bent pins and remove from service immediately any probes that have connector damage. A bent or broken pin can damage the connector board on a system which will in turn damage the next probe that is plugged into that port.
Now test the electrical safety by preparing a water bath with a saline solution. I prefer to use the top of a tissue-mimicking phantom so I can combine this with the next test. By setting up your leakage meter for chassis leakage, energizing the probe with the ultrasound system and inserting the nosepiece in the solution, and completing the circuit by inserting your leakage probe into the solution and then lifting the ground, you can test for transducer leakage current.
Now scan your phantom and look for any dropouts or irregularities in the image to check for dead or weak elements. By moving a transducer slowly across the phantom and watching for darker areas that move with the probe, you can identify problem elements.
The simple tests described here will enable a service engineer to perform a well-rounded evaluation of a transducer’s safety and performance when in the field.