OBJECTIVE: The present study was aimed at identifying temporomandibular joint inflammatory processes employing technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO)-labelled autonomous leukocytes. MATERIALS AND METHODS: We have utilized an experimental model of arthritis induction in ten adult male New Zealand rabbits by means of ovalbumin intra-articular injection into each left temporomandibular joint. For control purposes, saline solution was injected. After leukocytes radiolabelling with 99mTc-HMPAO and injection into rabbits, scintigraphic images were obtained. RESULTS: A higher 99mTcHMPAO-leukocytes uptake was observed in left temporomandibular joint in comparison with the contralateral joint. Wilcoxon non-parametric test was applied for statistical analysis. There was a statistically significant difference between counts of radioactivity per minute in the inflammed joint and the contralateral one (p = 0.0073). CONCLUSION: The method employing 99mTc-HMPAO-labelled autologous leukocytes allows an early and accurate detection of inflammatory processes, contributing to the adoption of a therapeutic conduct for patients before structural alterations have occurred.

Keywords: Temporomandibular joint disorder, Arthritis, 99mTc-HMPAO

OBJECTIVE: The present study proposes the evaluation of the depth-dose profiles and the spatial distribution of radiation dose for ocular proton beam radiotherapy protocols, based on computer simulations in nuclear codes and an eye model discretized into voxels. MATERIALS AND METHODS: The employed computational tools were Geant4 (GEometry ANd Tracking) Toolkit and SISCODES (Sistema Computacional para Dosimetria em Radioterapia - Computer System for Dosimetry in Radiotherapy). Geant4 is a toolkit for simulating the passage of particles through the matter, based on Monte Carlo method. Computer simulations of proton therapy were performed based on preexisting facilities. RESULTS: Simulation data were integrated into SISCODES on the eye's model generating spatial dose distributions. Dose depth profiles reproducing the pure and modulated Bragg peaks are presented. Relevant aspects of proton beam radiotherapy planning are considered such as material absorber, modulation, collimator dimensions, incident proton energy and isodose generation. CONCLUSION: The conclusion is that proton therapy when properly modulated and directed can reproduce the ideal conditions for the dose deposition in the treatment of ocular tumors.

Keywords: Proton therapy; Geant4; SISCODES; Ocular radiotherapy; Protons.

Objective: The present paper describes a procedure for conversion of computed tomography or magnetic resonance images into a three-dimensional voxel model for dosimetry purposes. Such model is a personalized representation of the patient that can be utilized in nuclear particle transport simulations by means of the MCNP (Monte Carlo N-Particle) code, reproducing the stochastic process of nuclear particles interaction with human tissues. Materials and Methods: The developed computational system – SISCODES – is a tool designed for 3D planning of radiotherapy or radiological procedures. Based on tomographic images of the patient, the treatment plan is modeled and simulated. Then, the absorbed doses are shown by means of isodose curves superimposed on the model. The SISCODES couples the threedimensional model with the MCNP5 code, simulating the protocol of exposure to ionizing radiation. Results: The SISCODES has been utilized by the NRI/CNPq in the creation of anthropomorphic and anthropometric voxel models which are coupled with the MCNP code for modeling brachytherapy and teletherapy applied to lung, pelvis, spine, head and neck tumors, among others. The current SISCODES modules are presented together with examples of cases of radiotherapy planning. Conclusion: The SISCODES provides a fast method to create personalized voxel models of any patient which can be used in stochastic simulations. The combination of the MCNP simulation with a personalized model of the patient increases the dosimetry accuracy in radiotherapy.

Keywords: SISCODES; Radiotherapy; Dosimetry; Absorbed dose; Teletherapy; Brachytherapy.

Objective: The present paper addresses the dosimetric evaluation of carbon ion radiotherapy as compared with proton therapy. Materials and Methods: Computer simulations were undertaken with the Geant4 (GEometry ANd Tracking) code. An eye model discretized into voxels and implemented in the Siscodes system (computer system for dosimetry in radiation therapy) was utilized to generate and superimpose depth dose profiles and isodose curves. Different values for beam energy were adopted in the simulations of carbon ion beams, while in the simulation with proton beams irradiation line devices were included with different absorbing material thicknesses. Results: The simulations outputs were processed and integrated into the Siscodes to generate the spatial dose distribution in the eye model, considering changes in the beam entrance position. The dose rates were normalized as a function of the maximum dose for a beam at a specific entrance position, incident particle energy and number of incident carbon ions and protons. Conclusion: The described benefits together with the presented results contribute to the development of clinical applications and researches on carbon ion and proton therapy.

Keywords: Carbon ion therapy; Proton therapy; Geant4; Siscodes.

OBJECTIVE: The present paper is aimed at presenting a comparative dosimetric study of prostate brachytherapy with I-125 and Pd-103 seeds. MATERIALS AND METHODS: A protocol for both implants with 148 seeds was simulated on a heterogeneous three-dimensional pelvic phantom by means of the SISCODES/MCNP5 codes. Dose-volume histograms on prostate, rectum and bladder, dose indexes D₁₀, D₃₀, D₉₀, D_0.5cc, D_2cc and D_7cc, and representations of the spatial dose distribution were evaluated. RESULTS: For a D₉₀ index equivalent to the prescription dose, the initial activity of each I-125 seed was calculated as 0.42 mCi and of Pd-103 as 0.94 mCi. The maximum dose on the uretra was 90% and 108% of the prescription dose for I-125 and Pd-103, respectively. The D_2cc for I-125 was 30 Gy on the rectum and 127 Gy on the bladder; for Pd-103 was 29 Gy on the rectum and 189 Gy on the bladder. The D₁₀ on the pubic bone was 144 Gy for I-125 and 66 Gy for Pd-103. CONCLUSION: The results indicate that Pd-103 and I-125 implants could deposit the prescribed dose on the target volume. Among the findings of the present study, there is an excessive radiation exposure of the pelvic bones, particularly with the I-125 protocol.

Keywords: Radiotherapy; Dosimetry; Prostate cancer; Brachytherapy; SISCODES; MCNP.

OBJECTIVE: Comparative analysis of dosimetry in intracavitary balloon catheter brachytherapy with I-125 and in Cf-252 brachytherapy combined with BNCT for treatment of brain tumors. MATERIALS AND METHODS: Simulations of intracavitary balloon catheter brachytherapy with I-125 and in Cf-252 brachytherapy combined with BNCT were performed with the MCNP5 code, modeling the treatment of a brain tumor on a voxel computational phantom representing a human head. Absorbed dose rates were converted into biologically weighted dose rates. RESULTS: Intracavitary balloon catheter brachytherapy with I-125 produced biologically weighted mean dose rates of 3.2E-11, 1.3E-10, 1.9E-11 and 6.9E-13 RBE.Gy.h^–1.p ^–1.s, respectively, on the healthy tissue, on the balloon periphery and on the I₁ and I₂ tumor infiltration zones. On the other hand, Cf-252 brachytherapy combined with BNCT produced a biologically weighted mean dose rate of 5.2E09, 2.3E-07, 8.7E-09 and 2.4E-09 RBE.Gy.h^–1.p ^–1.s, respectively on the healthy tissue, on the target tumor and on the I₁ and I₂ infiltration zones. CONCLUSION: Cf-252 brachytherapy combined with BNCT delivered a selective irradiation to the target tumor and to infiltration zones, while intracavitary balloon catheter brachytherapy with I-125 delivered negligible doses on the tumor infiltration zones.

Keywords: Brachytherapy; Glioblastoma multiforme; Dosimetry; BNCT; MCNP.

OBJECTIVE: To perform a comparative dosimetric analysis, based on computer simulations, of temporary balloon implants with ^99mTc and balloon brachytherapy with high-dose-rate (HDR) ¹⁹²Ir, as boosts to radiotherapy. We hypothesized that the two techniques would produce equivalent doses under pre-established conditions of activity and exposure time. MATERIALS AND METHODS: Simulations of implants with ^99mTc-filled and HDR ¹⁹²Ir-filled balloons were performed with the Siscodes/MCNP5, modeling in voxels a magnetic resonance imaging set related to a young female. Spatial dose rate distributions were determined. In the dosimetric analysis of the protocols, the exposure time and the level of activity required were specified. RESULTS: The ^99mTc balloon presented a weighted dose rate in the tumor bed of 0.428 cGy.h^-1.mCi^-1 and 0.190 cGyh^-1.mCi^-1 at the balloon surface and at 8-10 mm from the surface, respectively, compared with 0.499 and 0.150 cGyh^-1.mCi^-1, respectively, for the HDR ¹⁹²Ir balloon. An exposure time of 24 hours was required for the ^99mTc balloon to produce a boost of 10.14 Gy with 1.0 Ci, whereas only 24 minutes with 10.0 Ci segments were required for the HDR ¹⁹²Ir balloon to produce a boost of 5.14 Gy at the same reference point, or 10.28 Gy in two 24-minutes fractions. CONCLUSION: Temporary ^99mTc balloon implantation is an attractive option for adjuvant radiotherapy in breast cancer, because of its availability, economic viability, and similar dosimetry in comparison with the use of HDR ¹⁹²Ir balloon implantation, which is the current standard in clinical practice.

Keywords: Breast brachytherapy; Balloon; Radiotherapy dosage; Radiotherapy, adjuvant; ^99mTc; ¹⁹²Ir; Monte Carlo method.