Prog Med Phys.  2024 Dec;35(4):116-124. 10.14316/pmp.2024.35.4.116.

A Commissioning Report on the Magnetic ResonanceCompatible Geneva Brachytherapy Applicator

• Huh Y
• Park H
• Jegal J
• Lee I
• Son J
• Kang S
• Choi CH
• Kim Ji
• Jin H

• KMID: 2564150
• DOI: http://doi.org/10.14316/pmp.2024.35.4.116

Abstract

Purpose
Brachytherapy is essential for treating gynecological cancers as it offers precise radiation delivery to tumors while minimizing radiation exposure to surrounding healthy tissues. The Geneva applicator, introduced in 2020 as a replacement for older models like the Utrecht applicator, enhances MRI-based brachytherapy with improved imaging capabilities and more accurate applicator placement. In 2021, updates to non-reimbursement policies in Korea for MRI-based 3D brachytherapy planning further promoted the adoption of advanced techniques such as the Geneva applicator. This study aims to commission the Geneva applicator, focusing on wall thickness, dummy marker positions, and source dwell positions to ensure accurate dose delivery and safety.
Methods
The commissioning process involved measuring wall thickness in both the longitudinal and transverse directions for the tandem and lunar-shaped ovoid tubes and comparing these measurements with the manufacturer’s specifications. Dummy marker positions were verified using CT imaging, with a focus on alignment tolerances of ±1 mm. Source dwell positions were planned using the Oncentra treatment planning system, with measurements taken using EBT4 film and analyzed with RIT software.
Results
Wall thickness measurements and dummy marker positions were within the specified tolerance ranges, confirming their accuracy. The source dwell positions, measured and analyzed through multiple tests, were all within the ±1 mm tolerance, ensuring the applicator’s reliability.
Conclusions
The Geneva applicator met all standards for safe and effective use in brachytherapy. The use of a 3D-printed holder was crucial for precise alignment and measurement. With updated reimbursement policies in Korea for MRI-based brachytherapy, the Geneva applicator is expected to significantly impact the future of advanced brachytherapy treatments and research.

Keyword

MRI-based brachytherapy,; Geneva applicator; EBT4 film; 3D-printed holder

Figure

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  Fig. 1 A Geneva applicator (Elekta) set comprising an intrauterine tube and a pair of ovoid tubes.

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  Fig. 2 3D-printed holders for a pair of ovoid tubes (green) and tandem tubes with varying tip lengths (gray). Film insertion slots are located at the top of each holder for measuring the dwell position.

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  Fig. 3 X-ray dummy markers for ovoid tubes (1, 2) and tandem tubes (3).

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  Fig. 4 Applicator setups with EBT4 film (Ashland) for source dwell position measurements. (a) A pair of ovoid and a tandem on the table for measurement of the source dwell position and side views for them (b).

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  Fig. 5 The dummy marker position comparison between the applicator model in the treatment planning system and CT images.

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  Fig. 6 Example images for the measurement of the longitudinal wall thickness of the tandem and ovoid (a) and the transverse wall thickness measurement of the tandem tube and the measurement of the angle of curvatures using the ImageJ (National Institutes of Health) tool (b: left, outer; right, inner; c: ovoids and a tandem).

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  Fig. 7 Measured film sets for the source dwell position of the tandem and ovoid tubes. (a) EBT4 films (Ashland) and (b, c) examples for the dwell position analysis for ovoid and tandem with RIT software (Radiological Imaging Technology).

Reference

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