High dose rate (HDR) brachytherapy uses high strength radioactive sources and temporary interstitial implants to conform the dose to target and minimize the treatment time. The advances of imaging ...technology enable accurate reconstruction of the implant and exact delineation of high-risk CTV and the surrounding critical structures. Furthermore, with sophisticated treatment planning systems, applicator devices and stepping source afterloaders, brachytherapy evolved to a more precise, safe and individualized treatment. At the Radiation Oncology Department of Metropolitan Hospital Athens, MRI guided HDR gynecologic (GYN) brachytherapy and accelerated partial breast irradiation (APBI) with brachytherapy are performed routinely. Contouring and treatment planning are based on the recommendations of the GEC - ESTRO Working group. The task of this presentation is to reveal the advantages of 3D image guided brachytherapy over 2D brachytherapy. Thus, two patients treated at our department (one GYN and one APBI) will be presented. The advantage of having adequate dose coverage of the high risk CTV and simultaneous low doses to the OARs when using 3D image- based brachytherapy will be presented. The treatment techniques, equipment issues, as well as implantation, imaging and treatment planning procedures will be described. Quality assurance checks will be treated separately.
Purpose:
Modern clinical accelerators are capable of producing ion beams from protons up to neon. This work compares the depth dose distribution and corresponding dose averaged linear energy transfer ...(LET) distribution, which is related to the biological effectiveness, for different ion beams (1H, 4He, 6Li, 8Be, 10B, 12C, 14N, and 16O) using multi-energetic spectra in order to configure spread-out Bragg peaks (SOBP).
Methods:
Monte Carlo simulations were performed in order to configure a 5 cm SOBP at 8 cm depth in water for all the different ion beams. Physical dose and dose averaged LET distributions as a function of depth were then calculated and compared. The superposition of dose distribution of all ions is also presented for a two opposing fields configuration. Additional simulations were performed for12C beams to investigate the dependence of dose and dose averaged LET distributions on target depth and size, as well as beam configuration. These included simulations for a 3 cm SOBP at 7, 10, and 13 cm depth in water, a 6 cm SOBP at 7 depth in water, and two opposing fields of 6 cm SOBP.
Results:
Alpha particles and protons present superior physical depth dose distributions relative to the rest of the beams studied. Dose averaged LET distributions results suggest higher biological effectiveness in the target volume for carbon, nitrogen and oxygen ions. This is coupled, however, with relatively high LET values—especially for the last two ion species—outside the SOBP where healthy tissue would be located. Dose averaged LET distributions for8Be and 10B beams show that they could be attractive alternatives to 12C for the treatment of small, not deeply seated lesions. The potential therapeutic effect of different ion beams studied in this work depends on target volume and position, as well as the number of beams used.
Conclusions:
The optimization of beam modality for specific tumor cites remains an open question that warrants further investigation and clinically relevant results.
Purpose: GATE is a Monte Carlo (MC) simulation toolkit based on the Geant4 package widely used for many medical physics applications. The latest version of GATE extends its applications to ...radiotherapy. Aim of the current study is to evaluate the validity of the code for accurate brachytherapy dosimetry, since this is a prerequisite for its integration within the armamentarium of validated and useful MC codes for this purpose. Methods: Towards this aim a number of most commercially used HDR and PDR Ir‐192 as well as LDR I‐125 brachytherapy sources have been simulated using the GATE MC toolkit. Their specific dosimetric parameters following the TG43 formalism have been derived and subsequently benchmarked versus the clinically used dosimetric data which are incorporated in several Brachytherapy treatment planning systems, and versus several MC codes — such as MCNP, EGSnrc, BrachyDose, GEANT, PENELOPE and MCPT — that have been used extensively for brachytherapy dosimetry. Results: The comparison of the GATE derived dosimetric results with the aforementioned established MC codes for the dose rate constant, the radial dose function, the anisotropy function as well as the along and away dose rate tables, exhibited an agreement within 3% in all cases. The use of different cross section libraries, material data tables as well as simulation geometries could justify these differences that are, however, comparable to the discrepancies observed among other MC codes for the same source designs. Conclusions: The GATE Monte Carlo toolkit has been benchmarked with well established MC codes in brachytherapy dosimetry and can be safely added within the armamentarium of MC codes used for this purpose. Its versatility and dynamic developing structure promises its use not only in the dosimetric characterization of brachytherapy sources but also in the simulation of real voxel based patient anatomy with the patient related implemented brachytherapy treatment plan.
Online monitoring of the stopping distribution of particle beams used for radiotherapy provides the possibility of detecting possible errors in dose deposition early during a given treatment session, ...and may therefore help to improve the quality of the therapy. Antiproton annihilation events produce several long-range secondary particles which can be detected in real time by standard high energy particle physics detector systems. In this note, Monte Carlo calculations are performed in order to study the feasibility of real-time imaging by detecting charged pions produced during antiproton irradiation of typical biological targets. A simple treatment plan in a water phantom is simulated and the results show that by detecting pi+/- the position and the size of the planned target volume can be located with precision in the order of 1 mm.
Purpose:
Water equivalent polymer gel dosimeters and magnetic resonance imaging were employed to measure the output factors of the two smallest treatment fields available in a Gamma Knife model C ...radiosurgery unit, those formed employing the 4 and 8 mm final collimator helmets.
Methods:
Three samples of the VIP normoxic gel formulation were prepared and irradiated so that a single shot of the field whose output factor is to be measured and a single shot of the reference 18 mm field were delivered in each one. Emphasis is given to the development and benchmarking of a refined data processing methodology of reduced uncertainty that fully exploits the 3D dose distributions registered in the dosimeters.
Results:
Polymer gel results for the output factor of the 8 mm collimator helmet are found to be in close agreement with the corresponding value recommended by the vendor (
0.955
±
0.007
versus 0.956, respectively). For the 4 mm collimator helmet, however, polymer gel results suggest an output factor 3% lower than the value recommended by the vendor (
0.841
±
0.009
versus 0.870, respectively).
Conclusions:
A comparison with corresponding measurements published in the literature indicates that output factor results of this work are in agreement with those obtained using dosimetric systems which, besides fine spatial resolution and lack of angular and dose rate dependence of the dosimeter’s response, share with polymer gels the favorable characteristic of minimal radiation field perturbation.
VIP polymer gel dosimeter was used for Carbon ion beam dosimetry using a 150 MeV/n beam with 10 Gy plateau dose and a SOBP irradiation scheme with 5 Gy Bragg peak dose. The results show a decrease by ...8 mm in the expected from Monte Carlo simulation range in water, suggesting that the dosimeter is non water equivalent. However VIP shows efficiency close to 1 in the plateau region and significantly reduced efficiency in the peak. On the other hand the SOBP results yield an efficiency close to 1 in the SOBP implying that the dose response of the VIP dosimeter may not be solely related to LET.
Purpose: Modern clinical accelerators are capable of producing ion beams from protons up to neon. This work compares the depth dose distribution and corresponding dose averaged linear energy transfer ...(LET) distribution, which is related to the biological effectiveness, for different ion beams ({sup 1}H, {sup 4}He, {sup 6}Li, {sup 8}Be, {sup 10}B, {sup 12}C, {sup 14}N, and {sup 16}O) using multi-energetic spectra in order to configure spread-out Bragg peaks (SOBP). Methods: Monte Carlo simulations were performed in order to configure a 5 cm SOBP at 8 cm depth in water for all the different ion beams. Physical dose and dose averaged LET distributions as a function of depth were then calculated and compared. The superposition of dose distribution of all ions is also presented for a two opposing fields configuration. Additional simulations were performed for {sup 12}C beams to investigate the dependence of dose and dose averaged LET distributions on target depth and size, as well as beam configuration. These included simulations for a 3 cm SOBP at 7, 10, and 13 cm depth in water, a 6 cm SOBP at 7 depth in water, and two opposing fields of 6 cm SOBP. Results: Alpha particles and protons present superior physical depth dose distributions relative to the rest of the beams studied. Dose averaged LET distributions results suggest higher biological effectiveness in the target volume for carbon, nitrogen and oxygen ions. This is coupled, however, with relatively high LET values--especially for the last two ion species--outside the SOBP where healthy tissue would be located. Dose averaged LET distributions for {sup 8}Be and {sup 10}B beams show that they could be attractive alternatives to {sup 12}C for the treatment of small, not deeply seated lesions. The potential therapeutic effect of different ion beams studied in this work depends on target volume and position, as well as the number of beams used. Conclusions: The optimization of beam modality for specific tumor cites remains an open question that warrants further investigation and clinically relevant results.
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