Technical Note: Dose distributions in the vicinity of high-density implants using 3D gel dosimeters

In this work, we develop a methodology for using Fricke gel dosimeters for dose distribution measurements surrounding high-density implants which circumvents artifact production by removing the obstruction during imaging.

Custom 3D printed molds were used to set cavities in Fricke gel phantoms to allow for the suspension of high-density implants in different geometries. This allowed for the metal valve extracted from a temporary tissue expander to be suspended during irradiation, and removed during optical-CT scanning.

The removal of the metal implant and subsequent backfilling of the remaining cavity with optically matched fluid prior to dose evaluation enables accurate optical-CT scanning of the gel dosimeters. Results have shown very good agreement between measured and calculated doses within 2 mm from the surface of the implant. Slight deviations are present within 1 mm of the interface.

Artifacts in the form of radial streaking, cold spots, and hot spots were all reduced using this technique, enabling the broader and more accurate use of optical-CT for the imaging of gels containing opaque objects.