Medical Device Testing Services
Medical Device Testing Services
 

Testing Know How

TESTING TIP: JANUARY 28TH, 2016  

January 28th, 2016- How to verify motion at high frequency?

 

Measurement of Attachment Lead

Most medical devices and materials exhibit frequency-dependent behavior. This sometimes presents a challenge when testing at high frequencies (40-60Hz). Device mass or material loss modulus may attenuate or dampen the device response as the test frequency is increased. This could alter the strain amplitude that you are hoping to achieve with the accelerated test. For any test setup involving significant strain it is best to validate that the desired motion is being met at the accelerated test frequency. Motion validation studies are performed in several steps:

  1. First the test is set up and a video of the test motion at a physiological test frequency is captured by a video camera.

  2. Using the ProAnalyst image analysis software, the motion is analyzed and measured to provide key attributes of the motion. For example for a bend test one might characterize the maximum and minimum bend radii that the specimen undergoes.

  3. Next the test is accelerated and another video is taken using the higher speed setting on the camera (up to 6,000 frames per second).

  4. Once again using the ProAnalyst image analysis software and the high speed video, the key features identified previously are measured and compared to the physiological measurements to verify that the same attributes are achieved (ie: same max/min radii are achieved).

 

Figure I shows an example of radii analysis for a pacemaker lead. The analysis ensures that the minimum and maximum radii are achieved at the accelerated test frequency. When designing a high frequency test, frequency dependent behaviors need to be taken into consideration and validation techniques need to be used to ensure that the test is accurate. MDT performs high speed video validation of accelerated high strain tests on a regular basis to ensure that our tests are the most accurate available.