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Purpose: To investigate the dosimetric characteristics of accelerated partial breast irradiation technique by MammoSite® applicator using thermoluminescent dosimeter (TLD) and Monte Carlo simulation to comparing them with treatment planning system calculation for planning target volume (PTV) and organs at risk such as skin, lung and chest wall. Materials and Methods: The Monte Carlo MCNP-5 code was used to simulate dose rate in the PTV that is a MammoSite® balloon with 1 cm margin around it. Experimental dosimetry was carried out within a female-equivalent chest phantom with TLD dosimeter after insertion of 192Ir source into the MammoSite® applicator. Three dimensional planning (TP) was done for dose delivery to the specific points within the phantom by means of FlexiPlan software. Results: Statistical comparisons were done between TP calculation, Monte Carlo simulation and TLD. Our results showed good agreement for surface doses between simulation and measurement. The mean skin dose for the simulation and TLD result was 61.7% and 56.8% of prescription dose, respectively. The maximum dose to the chest wall for Monte Carlo and TLD were 114.4% and 111.8% of prescription dose, respectively. The maximum dose to the lung for Monte Carlo and TLD results were 28.4% and 27.3% of prescription dose, respectively. Using Monte Carlo simulation and an average female chest phantom, it was possible to demonstrate the accuracy on the calculated dose rate in the PTV of a MammoSite® dose delivery system with 192Ir HDR sources. Conclusions: The results showed acceptable agreement between simulation, treatment planning, and experimental dosimetry results. [ABSTRACT FROM AUTHOR]

Purpose: To study the effects of the breast-air and breast-lung interfaces on the absorbed dose within the planning target volume (PTV) of a MammoSite® balloon dose delivery system as well as the effect of contrast material on the dose rate in the PTV. Methods: The Monte Carlo MCNP5 code was used to simulate dose rate in the PTV of a 2 cm radius MammoSite® balloon dose delivery system. The simulations were carried out using an average female chest phantom (AFCP) and a semi-infinite water phantom for both Yb-169 and Ir-192 high dose rate sources for brachytherapy application. Gastrografin was introduced at varying concentrations to study the effect of contrast material on the dose rate in the PTV. Results: The effect of the density of the materials surrounding the MammoSite® balloon containing 0% contrast material on the calculated dose rate at different radial distances in the PTV was demonstrated. Within the PTV, the ratio of the calculated dose rate for the AFCP and the semi-infinite water phantom for the point closest to the breast-air interface (90°) is less than that for the point closest to the breast-lung interface (270°) by 11.4% and 4% for the HDR sources of Yb-169 and Ir-192, respectively. When contrast material was introduced into the 2 cm radius MammoSite® balloon at varying concentrations, (5%, 10%, 15%, and 20%), the dose rate in the AFCP at 3.0 cm radial distance at 90° was decreased by as much as 14.8% and 6.2% for Yb-169 and Ir-192, respectively, when compared to that of the semi-infinite water phantom with contrast concentrations of 5%, 10%, 15%, and 20%, respectively. Conclusions: Commercially available software used to calculate dose rate in the PTV of a MammoSite® balloon needs to account for patient anatomy and density of surrounding materials in the dosimetry analyses in order to avoid patient underdose. [ABSTRACT FROM AUTHOR]

Contemporary radiation oncology departments are often lacking a conventional simulator due to common use of virtual simulation and recent implementation of image guided radiation therapy. A protocol based on MammoSite® method was developed using CT based planning, a Source Position Simulator (SPS) with a Simulator Wire and a linear accelerator based On-Board Imager (OBI) for daily verification. After MammoSite® balloon implantation, the patient undergoes a CT study. The images are evaluated for tissue conformance, balloon symmetry, and balloon surface to skin distance according to the departmental procedure. Prior to the CT study the SPS is attached to the transfer tube that in turn is attached to the balloon catheter. The length from the indexer to the first dwell position is measured using the simulator wire with X-ray markers. After the CT study is performed, the data set is sent to the Varian Eclipse treatment planning system (TPS) and to the Nucletron PLATO brachytherapy planning system. The reference digitally reconstructed radiographs (DRRs) of anterior and lateral setup fields are created using Eclipse TPS and are immediately available on the OBI console via the Varian Vision integrated system. The source dwell position coinciding with the balloon center is identified in the CT dataset, followed by the offset calculation, catheter reconstruction, dose points placement and dwell time calculation. OBI fluoroscopy images are acquired and marked as initial. Prior to each treatment fraction balloon diameter and symmetry are evaluated using OBI fluoroscopy and tools available on the OBI console. Acquired images are compared with reference DRRs and/or initial OBI images. The whole process from initial evaluation to daily verification is filmless and does not undermine the precision of the procedure. This verification time does not exceed 10 min. The balloon diameter correlates well (within 1 mm) between initial CT and OBI verification images. The balloon symmetry is defined with 1 mm accuracy using existing OBI console tools. It is feasible to use OBI based simulation for the MammoSite® balloon placement evaluation, balloon integrity daily verification, and treatment dwell position coincidence with balloon center. This verification is a rapid process and is an alternative to the conventional simulator based technique. The simulator wire with X-ray markers for the SPS is the recommended tool for the CT based MammoSite® procedure. [ABSTRACT FROM AUTHOR]

Abstract: Background and purpose: In a prospective multi-center phase II trial, we investigated the MammoSite® Radiation Therapy System, a new device for delivering intracavitary brachytherapy following breast conserving surgery. The MammoSite® is a dual lumen, closed ended catheter with a small, spherical inflatable balloon and a port for connecting a remote afterloader to the central lumen. We analyzed the surgical procedure and placement of the MammoSite®, treatment planning and radiation delivery complications and cosmesis, as well the comfort for the patients. Patients and methods: Between 2002 and 2004 a total of 32 patients (pts) were implanted using the MammoSite®. The reference isodose was defined 1cm from the balloon surface. We analyzed the post-implant anatomic position of the applicator and the geometric form of the balloon via ultrasound, CT and X-ray, related side effects, cosmetic outcome and patient quality of life. Results: Twenty-three out of 32 patients (72%) were eligible for MammoSite® intracavitary brachytherapy. Twenty-eight percentage had to be excluded because of different reasons. Eleven patients were treated with primary brachytherapy with a total dose of 34Gy (2×3.4Gy) and 12 had a boost with a mean dose of 13.3Gy (range: 7.5–15Gy; 2×2.5Gy) combined with EBRT and doses ranged between 46 and 50Gy. In three cases a balloon rupture occurred. We observed two abscesses within 3 months of implantation and serious seroma development in 10 patients (39%). Skin related side effects were erythema in 21 patients (91%), hyperpigmentation in 13 patients (56%) and teleangiectasia in six patients (26%) after mean follow-up 20 months. Conclusions: The MammoSite® Radiation Therapy System is a feasible treatment modality for intracavitary brachytherapy of breast cancer after breast conserving surgery. The advantage of the system is only one applicator is necessary for the delivery of a fractionated radiotherapy. In addition, patient tolerance of the procedure is high. Critical issues concern possible overdosages at the skin reflected by a high rate of late skin damage after only 20 months of follow-up time. The method could serve as an alternative to conventional multi-catheter brachytherapy for a selected group of patients. [Copyright &y& Elsevier]