Simple phantom fabrication for MRI‐based HDR brachytherapy applicator commissioning

Abstract

A new high dose rate (HDR) brachytherapy program was initiated in a community hospital setting, with the goal of using magnetic resonance (MR) images with the implant in place during the planning process. Physics acceptance testing and commissioning was completed for key program components, including multiple applicators. To image new applicators for MRI‐based planning prior to use with patients, agar gel doped with copper sulfate was created using simple, MR‐safe household materials as a practical and inexpensive alternative to custom‐machined precision phantoms. Applicators in‐phantom were scanned in a 1.5 T MRI scanner using the same sequences developed for the brachytherapy program, then rigidly registered to high‐resolution computed tomography (CT) images to assess distortion, artifact, and geometric displacement. To date, Varian tandem and ring sets, segmented cylinders, cervical probes, endometrial applicators; and third‐party plastic needles, tandems, and vaginal guides have been imaged in phantom and are available for use clinically.

Practical experience commissioning MRI‐compatible tandem and ring applicators for use with the Bravos HDR afterloader

“…Four rings and four tandems were imaged suspended in phantom, in a positional geometry designed to be similar to future patient treatments. The gel was created using ratios of 1 L distilled water, 30 g agar‐agar powder, and 5 mL of 0.1 CuSO 4 solution following the process described by Fagerstrom and Kaur, 12 based on work by Haack et al 13 . and Mitchell et al 14 .…”

“…Four rings and four tandems were imaged suspended in phantom, in a positional geometry designed to be similar to future patient treatments. The gel was created using ratios of 1 L distilled water, 30 g agar-agar powder, and 5 mL of 0.1 CuSO 4 solution following the process described by Fagerstrom and Kaur, 12 based on work by Haack et al 13 and Mitchell et al 14 The applicators were protected using a thin layer of plastic wrap before pouring the agar solution into the phantom base. This plastic introduced an air gap immediately surrounding the applicators, though this volume was minimized to the extent possible.…”

Overview of medical physics education and research programs in a non‐academic environment

“…APTs have presented work at national conferences 35 as well as contributed as authors on published studies. 36 APT alumni have since gone on to study and conduct research at accredited medical physics graduate programs, including at the University of Wisconsin, University of Victoria, Oregon Health and Science University,and Vanderbilt University.When interviewed,APT alumni all indicated they applied for the APT program with the goal of gaining clinical experience prior to applying to graduate school.…”

“…Three recently graduated physics students were successfully recruited and trained during this time. APTs have presented work at national conferences 35 as well as contributed as authors on published studies 36 . APT alumni have since gone on to study and conduct research at accredited medical physics graduate programs, including at the University of Wisconsin, University of Victoria, Oregon Health and Science University, and Vanderbilt University.…”