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. 2021 Oct;22(10):278-287.
doi: 10.1002/acm2.13403. Epub 2021 Aug 26.

Gel and thermoluminescence dosimetry for dose verifications of a real anatomy simulated prostate conformal radiation treatment in the presence of metallic femoral prosthesis

Diana M C Rojas  1 , Juliana F Pavoni  2 , Gustavo V Arruda  3 , Oswaldo Baffa  2
Affiliations

Gel and thermoluminescence dosimetry for dose verifications of a real anatomy simulated prostate conformal radiation treatment in the presence of metallic femoral prosthesis

Diana M C Rojas et al. J Appl Clin Med Phys. 2021 Oct.

Abstract

This study aims to verify the dose delivery of prostate radiotherapy treatments in an adult pelvic phantom with two metallic hip and femur prosthesis using a four-field box technique. The prostate planned target volume (PTV) tridimensional (3D) dose distribution was evaluated using gel dosimetry, and thermoluminescent dosimeters (TLD) were used for point-dose measurements outside it. Both results were compared to the treatment planning system (TPS) dose calculation without using heterogeneity corrections to evaluate the influence of the metal in the dose distribution. MAGIC-f gel dosimeter (Methacrylic and Ascorbic acid in Gelatin Initiated by Copper with Formaldehyde) associated with magnetic resonance imaging was used. TLD were positioned at several points at the bone metal interface and the sacrum region. The comparison of the gel measured and the TPS calculated dose distributions were done using gamma analysis (3%/3 mm), and a pass rate of 93% was achieved. The TLD dose values at the bone-metal interface showed variations from the planned dose. However, at the sacrum region, where the beams did not intercept the prosthesis, there was a good agreement between TPS planning and TLD measurements. Our results show how the combination of 3D dosimetry and measurements at specific points in the phantom allowed a comprehensive view of the dose distribution and identified that care must also be paid to regions outside the PTV.

Keywords: MAGIC-f; femoral prosthesis; gel dosimetry; prostate; thermoluminescent dosimeters.

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Conflict of interest statement

The authors declare no conflicts of interest. This work is partially based on the Master's thesis of the first author which was coadvised by the coauthors.

Figures

FIGURE 1
FIGURE 1
Pelvic phantom illustration. The central region shows the cavity with the container with MAGIC‐f polymer gel positioned (A). Anterior view of the pelvis details inside the phantom (B)
FIGURE 2
FIGURE 2
Anterior view of the TLD dosimeters distribution in the femur, acetabulum, and sacral bone. There were four dosimeters placed around the femur, two at the acetabulum, and one at the sacrum for each side. Red and green arrows represent the dosimeters on the right and left side of the pelvis, respectively
FIGURE 3
FIGURE 3
Airtight PET container used for the 3D dose measurement (A) and screwed cap sealed glass test tubes (9 mL) used as calibration vials (B)
FIGURE 4
FIGURE 4
Screenshot of the TPS output for a bilateral prostheses prostate treatment using box technique irradiation
FIGURE 5
FIGURE 5
MAGIC‐f gel calibration curve showing a linear relationship: R2 = (2.21 ± 0.04) + (0.75 ± 0.02) D in the dose range measured, Pearson's r = 0.999
FIGURE 6
FIGURE 6
Examples of the axial gamma maps result in a comparison of the TPS dose distribution and the measured gel dose with 3%/3 mm criteria
FIGURE 7
FIGURE 7
Correlation between the delivered doses and the measured dose for Li:Mg.Ti TL dosimeters
See this image and copyright information in PMC

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