We recently added new equipment to our MRI safety evaluations laboratory that can be used to provide alternative methods for MR Conditional labeling of medical devices.
One safety concern for medical devices in the MR environment is radiofrequency (RF)-induced heating. MR Conditional labels include limits on scan duration and maximum RF power deposition to ensure that patients are not injured by device heating. Maximum RF power deposition is typically denoted as a specific absorption rate (SAR) value. SAR is a scanner-reported value that is dependent upon the mass of the patient as well as the anatomical area being scanned and is usually significantly overestimated by scanner manufacturers. These factors can lead to restrictive labeling for certain medical devices when SAR is used as the maximum RF power deposition condition on an MR Conditional label.
An alternative value that can be used for maximum RF power deposition on an MR Conditional label is B1+rms. B1+rms is a scanner-reported value that is independent of patient mass or anatomical scanning location and is calculated using a standardized equation according to IEC 60601-2-33. These attributes of B1+rms can allow for less conservative labeling compared to using SAR, especially for lower field strength MRI systems (i.e., 0.55 T and 1.2 T) that have more limited RF power.
Our new H-field probe and data acquisition system allow us to measure and map B1+rms in any MRI system. When used with our FDA-qualified medical device development tool (MDDT) or with our in-vivo RF-induced heating simulation capabilities, we can determine or scale RF-induced heating results at a given B1+rms condition. This can allow for less restrictive labeling for implants in terms of RF-induced heating, especially for electrically active implantable medical devices (AIMDs) with long metallic leads that have a higher propensity to cause heating.
For more information on how we can help you to explore alternative labeling or evaluate the overall MRI safety of your medical device, contact us today 855.463.1633 | firstname.lastname@example.org | medinstitute.com.
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