Design and Fabrication of Water Phantom for Treatment Verification in High Dose Rate (HDR) Brachytherapy of the Cervix (original) (raw)
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An anthropomorphic phantom for quality assurance and training in gynaecological brachytherapy
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Brachytherapy, 2015
This study presents a prototype of a phantom appropriate for experimental bladder dosimetry. This work presents details of the phantom construction and dosimetric results obtained using radiochromic film and optically stimulated luminescence dosimeters (OSLDs). METHODS AND MATERIALS: The phantom was constructed of polymethyl methacrylate. Two artificial bladders were three-dimensional printed using previous computed tomography images. Radiochromic films and OSLDs were positioned on the artificial bladder walls, and the applicators were placed according to the original computed tomography image. RESULTS: The prototype phantom simulated the behavior of the dose on the bladder surface, enabling bladder movement in all directions. The dosimetric study that was performed using radiochromic film and OSLDs exhibited concordance, in most cases, with the results obtained from the planning system. CONCLUSIONS: The methodology presented offers conditions for researchers to investigate more accurately the behavior of the dose on the bladder surface during intracavitary brachytherapy procedures.
Physica Medica, 2013
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A novel phantom design for brachytherapy quality assurance
International journal of radiation research, 2016
Background: One major challenge in brachytherapy is to verify the accuracy of dose distribu ons calculated by the treatment planning system. In this project, a new phantom design has been introduced for quality assurance of dose distribu ons in gynocological (GYN) brachytherapy implants using EBT GafChromic film. Materials and Methods: This phantom has been designed and fabricated from 90 slabs of 18×16×0.2 cm 3 Perspex to accommodate a tandem and ovoids assembly, which is normally used for GYN brachytherapy treatment. In addi on, this phantom design is allowing the use EBT GafChromic films for dosimetric verifica on of GYN implants with Cs-137 Selectron LDR system. With this assembly, GafChromic films were exposed using a plan designed to deliver 2.5 Gy dose to point "A" in Manchester system for tandem and ovoids configura ons and to deliver 1.5 Gy of dose to 0.5 cm distance from the lateral surface of ovoids for using ovoid-pair. The measured dose distribu ons with GafChromic films were compared with the TPS isodose lines both numerically and spa ally. For a quan ta ve analysis of the results, the measured doses values at several points of interest were evaluated with the treatment planning data and values obtained following the TG-43 dose calcula on formalism. Results: The results of these inves ga ons have indicated that the new phantom design enables us to measure differences of greater than ±6% for LDR brachytherapy GYN treatments. Conclusion: The new phantom design could be u lized for the QA procedure of the brachytherapy remote aCer loading systems to confirm the accuracy of dose distribu on in GYN implants.
Introduction Based on Task Group No. 43 (TG-43U1) recommendations, water phantom is proposed as a reference phantom for the dosimetry of brachytherapy sources. The experimental determination of TG-43 parameters is usually performed in water-equivalent solid phantoms. The purpose of this study was to determine the conversion factors for equalizing solid phantoms to water. Materials and Methods TG-43 parameters of low-and high-energy brachytherapy sources (i.e., Pd-103, I-125 and Cs-137) were obtained in different phantoms, using Monte Carlo simulations. The brachytherapy sources were simulated at the center of different phantoms including water, solid water, poly(methyl methacrylate), polystyrene and polyethylene. Dosimetric parameters such as dose rate constant, radial dose function and anisotropy function of each source were compared in different phantoms. Then, conversion factors were obtained to make phantom parameters equivalent to those of water. Results Polynomial coefficients of conversion factors were obtained for all sources to quantitatively compare g(r) values in different phantom materials and the radial dose function in water. Conclusion Polynomial coefficients of conversion factors were obtained for all sources to quantitatively compare g(r) values in different phantom materials and the radial dose function in water.
Fabrication and calibration of a water phantom for dosimetry studies
2003
Water phantoms are being useJ for the dose calibration in radiotherapy treatment. In general phantoms are imported and the dimensions of such phantoms arc usually 30 em x 30 em x 30 em, But in few treatment cases such a, lung, total body irradiation (WI) and for routine eahhrations a large size phantom is required. For that reason a phantom of dimenslOns 45 em x 45 em x 33 em was fabricated in the present study. Dose measurements ofoneo beam were maJe at depths 2.5, 5.0, 7.5, 10.0, 12.5, 15.0, 17.5,20.0,22,5,25.0,27.5 and 30.0 em for field sizes 5 x 5, 10 x 10, 15 xIS, 20 x 20, 25 x 25 and 30 x 30 emz, Also in the case of linear accelerator doses were measured for the field sizes 5 x 5, 10 x 10, 15 x 15,20 x 20, 25 x 25, 30 x 30, 35 x 35, and 40 x 40 eml at the same depths. An ionization chamber (Model 23323) of volume 0.1 cm) in conjunction with a PTW UNIDOS electrometer was used for dose measurement. To get IAEA standard dose a conversion factor of 1.0343 is e:.tablished. The requ...
Iranian Journal of Medical Physics, 2020
Introduction: In vitro dosimetric verification prior to patient treatment plays a key role in accurate and precision radiotherapy treatment delivery. Since the human body is a heterogeneous medium, the aim of this study was to design a heterogeneous pelvic phantom for radiotherapy quality assurance. Material and Methods: A pelvic phantom was designed using wax, pelvic bone, borax powder, and water mimicking different biological tissues. Hounsfield units and relative electron densities were measured. Various intensity-modulated radiotherapy (IMRT) plans were imported to the pelvic phantom for verification and implemented on the Delta 4 phantom. The quantitative evaluation was performed in terms of dose deviation, distance to agreement, and gamma index passing rate. Results: According to the results of the CT images of an actual patient, relative electron densities for bone, fat, air cavity, bladder, and rectum were 1.335, 0.955, 0.158, 1.039, and 1.054, respectively. Moreover, the CT...
Development of a novel and low-cost anthropomorphic pelvis phantom for 3D dosimetry in radiotherapy
Journal of Contemporary Brachytherapy
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.
Asian Pacific Journal of Cancer Prevention
Background: To develop a dosimetric tool to estimate the dose delivered in the presence of air pockets with EBT3 film while simulating the conditions of vaginal vault brachytherapy (VVBT) with 3.0 diameter cylindrical applicator at a prescription dose distance of 5mm from the surface of it. Materials and Method: Six acrylic plates (10 cm x 10 cm, 0.5 cm thick) with four different types of slots were designed and produced locally. They can hold a cylindrical vaginal brachytherapy applicator in the centre, air equivalent material from the applicator's surface [(sizes 4.5 mm (A), 3.0 mm (B), and 2.0 mm (C)], EBT3 film at the prescribed dose distance, and holder rods. Plates were layered together with acrylic rods and assembled in a holding box in a water phantom. Three treatment plans done in TPS with prescription doses of 2 Gy, 3 Gy, and 4 Gy at 5.0 mm with a treatment length of 6 cm, and were executed in Co-60based HDR brachytherapy unit (M/s SagiNova, Germany) with & without the placement of air equivalent material, and the dose received at slot locations A, B, & C were noted. Results: The mean percentage deviation of measured dose without and with presence of air pocket at A, B and C was 13.9%, 11.0% and 6.4% respectively for all dose prescriptions. As the air pocket size expanded radially from 2.0 mm to 4.5 mm, the increase in dosage ranged from 6.4% to 13.9% which was due to the fact that the film was held at dosage prescription distance and the lack of attenuation of photons radially through air pocket. Conclusions: The present study can be carried out with a 3D printed phantom that simulates VVBT application having air pockets of different dimensions at different locations and also can be analyzed with Monte Carlo simulations.