Anthropomorphic phantom to investigate the bladder dose in gynecological high-dose-rate brachytherapy (original) (raw)
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An anthropomorphic phantom for quality assurance and training in gynaecological brachytherapy
Radiotherapy and Oncology, 2002
Background and purpose: An anthropomorphic water filled polymethylmethacrylate (PMMA) phantom designed to serve as a Quality Assurance (QA) tool and a training aid in brachytherapy of gynaecological tumours is investigated and presented. Several dosimetric parameters associated with the dose rate calculation can be verified with the aid of this phantom such as the source positioning, its imaging reconstruction from radiographs and the accuracy of the algorithm used for manual or computer dose rate calculation.
Physica Medica, 2013
The ferrous sulphate-benzoic acid-xylenol orange (FBX) chemical dosimeter, due to its aqueous form can measure average volume doses and hence may overcome the limitations of point dosimetry. The present study was undertaken to validate the use of FBX dosimeter for rectum and bladder dose measurement during intracavitary brachytherapy (ICBT) and transperineal interstitial brachytherapy (TIB). We filled cylindrical polypropylene tubes (PT) and Foley balloons (FB) with FBX solution and used them as substitutes for rectum and bladder dose measurements respectively. A water phantom was fabricated with provision to place the Fletcher-type ICBT and MUPIT template applicators, and FBX filled PT and FB within the phantom. The phantom was then CT scanned for treatment planning and subsequent irradiation. Our results show that the average difference between DVH derived dose value and FBX measured dose is 3.5% (PT) and 13.7% (FB) for ICBT, and 9% (PT) and 9.9% (FB) for TIB. We believe that the FBX system should be able to provide accuracy and precision sufficient for routine quality assurance purposes. The advantage of the FBX system is its water equivalent composition, average volume dose measuring capability, and energy and temperature independent response as compared to TLD or semiconductor dosimeters. However, detailed studies
International Journal of Gynecological Cancer, 2014
The objectives of the study were to assess the bladder doses during vaginal cuff brachytherapy and to examine the effect of bladder filling on normal tissue dosimetry by means of computed tomography. Materials and Methods: A total number of 45 women were enrolled in a prospective clinical trial. Patients were treated with the application of a single-line source vaginal cylinder. All the patients were asked to consume 400 mL of water 40 minutes before computed tomography scans were taken. For each patient, 2 treatment plans were performedVone with full bladder and the other one when the bladder was emptied. A dose-volume histogram and the equivalent of 2-Gy dose for full and empty bladder were calculated. Doses to the bowels in 2 states of the bladder were estimated. Results: Thirty-five patients received a lower dose to the empty bladder than to the filled organ. The average dose difference was 0.5 Gy. Ten patients received a lower dose to the full bladder than to the empty one. However, in this case, the difference amounted only to 0.2 Gy on average. Dose parameters (the maximal dose received by 0.1 cm 3 of tissue and the maximal dose received by 2 cm 3 of tissue) were lower in the empty state, but the volumetric parameters (the percent of bladder volume receiving Q50% of the prescribed dose and the percent of bladder volume receiving Q80% of the prescribed dose) were higher in the empty state of the bladder. Doses to the bowels seemed to be higher in the empty bladder. However, none of the doses exceeded the limitations. Conclusions: The results have shown that in most cases, the dose to the empty bladder is lower than when the bladder is full. Simultaneously, the doses to the bowels increase proportionally in the empty state of the bladder comparing to the full organ. Protection of the bowels, which are more radiosensitive, suggests treating the patients in the full state of the bladder. Early and late bowel toxicity should be investigated to establish clear standards of treatment.
International Journal of Scientific Research in Science and Technology
The aim of this study is to design and fabricate a local anatomical water phantom for dose distribution measurements during high dose rate brachytherapy of the cervix. Phantoms for dosimetry are used when there is a need to simulate the conditions of a procedure to measure dose at certain points of interest. It is dangerous to place a human being in a beam for dose measurements. Perspex (PMMA) sheets of thickness 6mm and 10mm were used for fabricating the phantom. The phantom designed is curved in shape with a predominantly 6mm thickness of the perspex material. It has a height of 41cm and breadth 31cm. The pieces of perspex material were glued to each other using Trichloromethane (chloroform) at room temperature. It is an organic compound with the formula CHCI3. A perspex sheet of 10mm was used to make one end of the phantom thicker than the other. This was done to support the reconstruction box. Two thin film holder slabs of dimensions 31.5 ×2.8 ?cm?^2 were fabricated by joining t...
2017
Intracavitary brachytherapy procedures are used for cervical cancer treatment, by the insertion of radioactive implants directly into the diseased tissues. During the treatment process, the bladder together with surrounding tissues are exposed to radiations. Clinical complications do results from high doses received by parts of the bladder during intracavitary brachytherapy of the cervix. The aim of this study is to assess the dose delivered to the bladder using Gafchromic films and compare it with the optimized dose calculated by the Brachy Prowess 4.60 Treatment Planning System (TPS) reports for empirical validation and system verification. Fletcher suite applicators were used to perform thirty (30) different clinical insertions on the constructed cervix phantom and results evaluated. The mean difference between the doses calculated by the TPS and the doses measured by the Gafchromic film for the bladder at the distance of 0.5cm from the edge of the film was 16.3 % (range -35.33 t...
International Journal of Radiation Oncology*Biology*Physics, 2008
Purpose: To investigate the effect of bladder filling on dosimetry and to determine the best bladder dosimetric parameter for vaginal cuff brachytherapy. Methods and Materials: In this prospective clinical trial, a total of 20 women underwent vaginal cylinder highdose-rate brachytherapy. The bladder was full for Fraction 2 and empty for Fraction 3. Dose-volume histogram and dose-surface histogram values were generated for the bladder, rectum, and urethra. The midline maximal bladder point (MBP) and the midline maximal rectal point were recorded. Paired t tests, Pearson correlations, and regression analyses were performed. Results: The volume and surface area of the irradiated bladder were significantly smaller when the bladder was empty than when full. Of the several dose-volume histogram and dose-surface histogram parameters evaluated, the bladder maximal dose received by 2 cm 3 of tissue, volume of bladder receiving 5050% of the dose, volume of bladder receiving 5070% of the dose, and surface area of bladder receiving 5050% of the dose significantly predicted for the difference between the empty vs. full filling state. The volume of bladder receiving 5070% of the dose and the maximal dose received by 2 cm 3 of tissue correlated significantly with the MBP. Bladder filling did not alter the volume or surface area of the rectum irradiated. However, an empty bladder did result in the nearest point of bowel being significantly closer to the vaginal cylinder than when the bladder was full. Conclusions: Patients undergoing vaginal cuff brachytherapy treated with an empty bladder have a lower bladder dose than those treated with a full bladder. The MBP correlated well with the volumetric assessments of bladder dose and provided a noninvasive method for reporting the MBP dose using three-dimensional imaging. The MBP can therefore be used as a surrogate for complex dosimetry in the clinic. Ó 2008 Elsevier Inc.
Journal of Contemporary Brachytherapy, 2013
Purpose: Distension and shape of urinary bladder may vary during intracavitary brachytherapy (ICBT) for cervical cancer, significantly affecting doses to bladder, rectum , sigmoid colon and small intestine and consequently late radiation toxicities. This study is to evaluate the effects of different fixed volume bladder distention on dosimetry, assessed by three dimensional image based planning, in different organs at risk during the treatment of cervical cancer with ICBT. Material and methods: Forty seven cervical cancer patients (stage IB to IVA) were qualified for ICBT following external beam radiotherapy. Urinary bladder was distended with different volumes of normal saline instilled by a Foley's catheter. Planning CT scans were performed after insertion of applicators and three dimensional treatment planning was done on Brachyvision ® treatment planning system (Varian Medical Systems, Palo Alto, CA). Dose volume histograms were analyzed. Bladder, rectum, sigmoid colon and small intestine doses were collected for individual plans and compared, based on the amount of bladder filling. Results: Mean dose to the bladder significantly decreased with increased bladder filling. However, doses to the small volumes (0.1 cc, 1 cc, 2 cc) which are relevant for brachytherapy, did not change significantly with bladder filling for bladder, rectum or sigmoid colon. Nevertheless, all dose values of small intestine are decreased significantly with bladder filling. Conclusions: Bladder distension has no significant effect on doses received during brachytherapy by relevant volumes of bladder, rectum and sigmoid colon except intestine where values are decreased with bladder distension. A larger study with clinical correlation of late toxicities is essential for proper evaluation of this strategy.
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.
Journal of contemporary brachytherapy, 2018
The dosimetry procedure by simple superposition accounts only for the self-shielding of the source and does not take into account the attenuation of photons by the applicators. The purpose of this investigation is an estimation of the effects of the tandem and ovoid applicator on dose distribution inside the phantom by MCNP5 Monte Carlo simulations. In this study, the superposition method is used for obtaining the dose distribution in the phantom without using the applicator for a typical gynecological brachytherapy (superposition-1). Then, the sources are simulated inside the tandem and ovoid applicator to identify the effect of applicator attenuation (superposition-2), and the dose at points A, B, bladder, and rectum were compared with the results of superposition. The exact dwell positions, times of the source, and positions of the dosimetry points were determined in images of a patient and treatment data of an adult woman patient from a cancer center. The MCNP5 Monte Carlo (MC) ...