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

Area of Science:

• Medical Physics
• Oncology
• Radiotherapy

Background:

• Magnetic Resonance Imaging (MRI) is increasingly used for treatment planning in High-Dose-Rate (HDR) brachytherapy.
• MR-conditional applicators require rigorous commissioning to ensure safety and accuracy within the MRI environment.

Purpose of the Study:

• To commission MR-conditional brachytherapy ring sets for use with a Bravos HDR remote afterloader in an MRI planning setting.
• To verify applicator performance and specifications in both CT and MRI environments.

Main Methods:

• Commissioning involved measurements of channel length, radiograph, autoradiograph, ring offset, and treatment interrupts.
• Applicators were assessed using CT and MRI, comparing results against manufacturer specifications and 3D virtual models.

Main Results:

• One defective ring was identified and replaced.
• The complete applicator suite, including the replacement, adhered to manufacturer specifications.
• An offset correction of -0.4 cm was determined for use with the Bravos system.

Conclusions:

• Thorough commissioning of brachytherapy applicators is essential for clinical use in specific environments.
• The validated MR-conditional rings and Bravos system are suitable for MRI-guided HDR brachytherapy planning.
• Implementing an offset correction ensures accurate treatment delivery.