Development of a novel and low-cost anthropomorphic pelvis phantom for 3D dosimetry in radiotherapy

Abstract

Purpose The aim of this study was to construct a low-cost, anthropomorphic, and 3D-printed pelvis phantom and evaluate the feasibility of its use to perform 3D dosimetry with commercially available bead thermoluminescent dosimeters (TLDs). Material and methods A novel anthropomorphic female phantom was developed with all relevant pelvic organs to position the bead TLDs. Organs were 3D-printed using acrylonitrile butadiene styrene. Phantom components were confirmed to have mass density and computed tomography (CT) numbers similar to relevant tissues. To find out clinically required spatial resolution of beads to cause no perturbation effect, TLDs were positioned with 2.5, 5, and 7.5 mm spacing on the surface of syringe. After taking a CT scan and creating a 4-field conformal radiotherapy plan, 3 dose planes were extracted from the treatment planning system (TPS) at different depths. By using a 2D-gamma analysis, the TPS reports were compared with and without the presence of beads. Moreover, the bead TLDs were placed on the organs’ surfaces of the pelvis phantom and exposed to high-dose-rate (HDR) 60 Co source. TLDs’ readouts were compared with the TPS calculated doses, and dose surface histograms (DSHs) of organs were plotted. Results 3D-printed phantom organs agreed well with body tissues regarding both their design and radiation properties. Furthermore, the 2D-gamma analysis on the syringe showed more than 99% points passed 3%- and 3-mm criteria at different depths. By calculating the integral dose of DSHs, the percentage differences were –1.5%, 2%, 5%, and 10% for uterus, rectum, bladder, and sigmoid, respectively. Also, combined standard uncertainty was estimated as 3.5% ( k = 1). Conclusions A customized pelvis phantom was successfully built and assessed to confirm properties similar to body tissues. Additionally, no significant perturbation effect with different bead resolutions was presented by the external TPS, with 0.1 mm dose grid resolution.

3D in vivo dosimetry of HDR gynecological brachytherapy using micro silica bead TLDs

“…As a result of these CTDIvol and TLDs’ energy response curves at kV photon beams, a correction factor for TLDs with absorbed doses less than 1 Gy was applied to account for the absorbed dose from CT imaging. This correction factor was neglected for TLDs that were exposed to higher absorbed doses 22,29 …”

“…Some current integrated system for in vivo measurement has been launched to enable reporting online point absorbed dose during the BT procedure 22 . However, there is still limited point absorbed dose measurements routinely 32 .…”

“…The first phase of the feasibility study of using bead TLDs in BT 3D dosimetry was performed on a female pelvis phantom and has been reported by Babaloui et al 22 . During the current study, 30 cervical cancer patients who had an indication for HDR‐BT were selected and involved nonrandomly.…”

“…The first phase of the feasibility study of using bead TLDs in BT 3D dosimetry was performed on a female pelvis phantom and has been reported by Babaloui et al 22 During the current study, 30 cervical cancer patients who had an indication for HDR-BT were selected and involved nonrandomly. The previously published IVD protocol for rectum and bladder dose measurements was employed throughout the included patients' BT sessions at the radiotherapy department of Yas Hospital in Tehran, Iran, between May and December 2019.…”

Technical Note: On the feasibility of performing dosimetry in target and organ at risk using polymer dosimetry gel and thermoluminescence detectors in an anthropomorphic, deformable, and multimodal pelvis phantom

“…Advanced 3D printing methods allow to tailor the design and construction of anthropomorphic phantoms according to very specific needs since the phantom and the organs can be easily and reproducibly printed with different size, shape, or composition. Today, several anthropomorphic phantoms for different anatomical regions (i.e., head 30 and pelvis 11,31 ) have been developed to perform dose measurements using different dosimetry detectors (i.e., radiophotoluminescence glass dosimeters, 30 polymer dosimetry gel, 7 TLDs, 32 films 10 ). However, to the best of our knowledge, the new ADAM PETer phantom is the first anthropomorphic phantom that (i) simulates prostate cancer as multifocal and metastatic disease including metastasis in lymph nodes and bones, (ii) has a modular setup in which organ surrogates can be exchanged within 15 min, (iii) allows for simulation of inter‐ and intrafractional organ motion and deformation, and (iv) is compatible not only with CT and MRI, but also with PET.…”