This work presents the development of an automatic radioactive seed implantation system (PSIS). PSIS may assist the testing permanent implants procedure in the prostate. These tests will be important in measurements of absorbed doses in the pelvic structures, involving the organs and tissues at risk to improve planning, seed positioning and dosimetry. The automated Prostate Seed Implant System (PSIS) has been designed to meet operational needs, which offers the freedom when positioning the brachytherapy needle inside the treatment area ensuring repeatability and fidelity to the planned treatment. Both the ultrasound probe and the seed implant needle are driven by stepper motors, ATMEGA microcontroller, bearings, aluminum shafts and a GUI (Graphical User Interface). Movement of both the probe and the needle holder was performed by fixed spindle on a threaded rod going through a stepper motors by a coupling. These engines were chosen due to the necessity of movements precision that these types of motors provide. The project was developed and the PSIS prototype was assembled. The prototype presented acceptable operating characteristics for prostate implants. The advantage of this system is that the automation of the application provides an accurate positioning and movement of both probe and seed application. In addition to this study, seeds implantation tests will be performed, and such tests will be essential in protocol validation processes.
O objetivo deste trabalho foi apresentar o estado da arte da pesquisa e desenvolvimento de um sistema mecânico de implante de sementes radioativas, denominado SISP, e de objeto anatômico simulador, OAS. O SISP e o OAS poderão auxiliar no procedimento de teste de implantes de sementes permanentes na próstata. Esses testes serão importantes para medições de doses absorvidas nas estruturas da pelve, envolvendo os órgãos e tecidos de risco para aprimoramento de planejamentos, posicionamentos de sementes e dosimetria. O SISP envolve dois suportes, anterior e posterior, uma mesa-móvel, placa-guia. As peças foram elaboradas em celeron; enquanto a placa guia em acrílico translúcido. Após individualmente confeccionadas, as peças foram montadas, compondo o protótipo final do SISP. Foi também elaborado e montado o objeto anatômico simulador de teste (OAS), reproduzindo de forma anatômico-equivalente a estrutura óssea da pelve, parte do reto, próstata e tecido adiposo. Os materiais utilizados no objeto de teste são de tecido-equivalente, com equivalência radiológica. Este artigo apresenta o sistema acoplando o SISP e OAS acoplados, possível de uso em implantes experimentais para braquiterapia de próstata.
Currently, there is a need to produce new therapeutic techniques for the treatment of prostate tumors, considering the high incidence of the disease and significant morbidity rates associated with surgery and radiotherapy. Simulations in brachytherapy produce essential information about the efficiency and dosimetric efficacy compared to other techniques. This study estimated the efficiency of dosimetry by parameters of merit generated from volumetric distributions of absorbed doses simulating two spatial distributions of Ho-166 seeds in a prostate model. A computer voxel model was developed, using the SISCODES (Computational System for Dosimetry by Neutrons and Photons by Stochastic Methods applied to radiology and radiotherapy) code. The virtual model reproduced a cubic box, filled with muscle equivalent tissue (TE), in which a 5-cm diameter sphere with TE-prostate was positioned 2-cm from the air-interface. Two Ho-166 seed distributions were employed with distinct pitches: 9 and 10 mm, with same distance between seed of 8mm in a fillet (needle). The MCNP5 code generated the energy deposited per unit mass in each voxel .The spatial dose distributions were obtained for each of the seed distributions. The following parameters-of-merit were evaluated: maximum dose values and histograms. The parameters were compared between the two simulated groups. It was possible to evaluate the most appropriate distribution to the prostate brachytherapy, which has been shown to be a function of the injected seed activity.
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