Meet Justin Renfrow, our Director of Business Operations.

Renfrow_Justin_blogThe aspect of MED that we take the most pride in is our history. With over 30 years of experience in medical devices we’ve seen a little bit of everything and have solved our share of complex problems. In my 12 years in medical devices I’ve seen my fair share of issues pre and post launch. I take a lot of pride in being able to work with our clients not only in the R&D phases, but being able to help once a product is commercially available.

Recently we had a client come to us with an issue that they could not replicate. This was an excellent company with a very talented team of medical experts and engineers. I’ve had the pleasure of working with their product managers and especially their medical director and these folks are top notch. Needless to say, these were not untrained eyes. After an initial call with the client and a brainstorming session, one of our senior engineers was able to identify an issue with the testing fixture the client was using and replicate the failure in his kitchen. Once that discovery was made, we were able to make an immediate impact for our client.

There’s something to be said for a fresh set of eyes. It also never hurts when those eyes have seen hundreds of medical devices and have fought those same battles. We’re proud of the work we do for all of our clients, but it’s times like this where we can feel the impact we have on our clients and most importantly, patients. For me it was especially gratifying knowing that we made an impact for a group I see as colleagues and friends. I see personalities, not just projects, and being able to work closely with our clients makes my job something I look forward to everyday.

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Medical Device MRI Safety Testing: Where should a hip implant be placed in an ASTM F2182 test to measure the maximum RF-induced heating?

As mentioned in our previous case study , testing the radio-frequency-induced tissue heating by implanted medical devices is important to prevent harm to patients during MR imaging. The ASTM F2182 standard describes the method for testing to evaluate MRI safety with respect to RF-induced heating.  The ASTM standard defines a phantom for testing (i.e., rectangular acrylic container filled with conductive gel) that acts as an approximate simulation of the human body. However, many devices have asymmetrical or complex shapes (e.g., hip implants) that present a challenge for the safety test engineer:

  • Where and in what orientation should the device be placed within the ASTM F2182 phantom for adequate safety assessment?
  • Where on the implant should the temperature probes be placed?


The location of the implant’s placement in the phantom also affects RF-induced heating as shown by the highly non-uniform electrical field magnitude in the ASTM F2182 phantom (see figures at right). In most cases, physical testing to determine the worst case orientation and location within the phantom as well as the location of the temperature probes would require significant effort.

Computational simulation is a Image2cost effective way of determining the worst case orientation and placement of the implant within the phantom. Using the computational simulation predictions, locations may be selected to place temperature probes for the physical tests.
See an animation of a computational simulation of an example hip implant that is positioned in the worst case location and orientation within the ASTM F2182 phantom below. From the results of this cost effective simulation, MRI safety device testing may be performed with the implant in the worst case location and the temperature probes placed to identify the locations of maximum heating.


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