IMAGING PRACTICE ACCREDITATION SUBCOMMITTEE REPORT Tyler Fisher, MS, Costa Mesa, CA

ACR Accreditation for Add-On, Upright Stereotactic Breast Biopsy Systems

Over the past few years, the Hologic Affirm Up-Right Stereotactic Biopsy system has become more prevalent in the marketplace. This unit attaches to the Selenia Dimensions system and provides stereotactic biopsy capabilities with Tomosynthesis imaging. Many facilities are transitioning to this system from their prone stereotactic tables due to superior image quality, no need for a dedicated biopsy room, and the freedom to use 3D imaging for biopsy. For the imaging physicist, however, these units present unique challenges for accreditation testing.

The current ACR Stereotactic Biopsy manual and QC forms were developed in 1999 and include a number of evaluations for film units. The Affirm unit is capable of performing many of these tests, but modifications are necessary to make the testing more appropriate. For accredited facilities, the ACR forms must still be submitted and all the required tests must be completed. Many of the tests are similar to either the standard Selenia Dimensions tests or prone stereotactic tests. The significant differences are seen in the ACR phantom, dose and HVL measurement, and AEC testing.

For the ACR phantom, many facilities with the Affirm system no longer have the small accreditation phantom. These facilities are using the regular ACR Image Quality phantom for routine testing. Because the Selenia Dimensions unit uses the regular Dimensions detector during biopsy imaging, facilities may acquire an image of the entire large phantom in one exposure. You should remove the compression paddle and acquire the image with the needle holder outside the phantom. Both 2D and 3D images should be acquired and scored. It has been my experience that the software does not directly display the kVp and mAs of the images. The easiest way I have found to view this data is, after you have acquired all the images in 2D and 3D mode, choose the print button and then select each image. The DICOM data will display on the review monitor.

For dose measurements, it is important to measure the tube output directly, without the compression paddle in place. This will make a significant difference, both in measured output and HVL. Use these values to calculate Mean Glandula Dose to the phantom and make sure that it is less than 3.0 mGy for both 2D and 3D modes – if you use the dose data from your testing of the Dimensions System with the paddle in place, you will be under-estimating the dose significantly. Automatic Exposure Control testing should be performed using both 2D and 3D modes as the units will be used in both modes. Hologic QC manuals now provide CNR correction factors for stereotactic biopsy imaging that must be utilized for the Exposure Indices to be in compliance. Again, to view the technique factors for each image, you should go to the print screen and the technique factors will become available.

Finally, the submission process for the ACR requires printed images at this time, preferably on film, but high quality paper copies are also accepted. They will accept 3D images with the lesion visible within the imaging plane, as well as 2D images. In the future, the ACR will accept digital images view upload or CD submission, but that capability is not available now.

For all questions regarding the ACR Stereotactic Breast Biopsy Accreditation program, please visit the ACR website.

Back to Article List Next Previous