Wellington Furtado Pimenta Neves-Junior

ROLE OF INTRA- OR PERIPROSTATIC CALCIFICATIONS IN IMAGE-GUIDED RADIOTHERAPY FOR PROSTATE CANCER

PURPOSE Image-guided radiotherapy (IGRT) allows more precise localization of the prostate, thus minimizing errors resulting from organ motion and set-up during treatment of prostate cancer. Using megavoltage cone-beam computed tomography (MVCBCT), references such as bones, the prostate itself or implanted fiducial markers can be used as surrogates to correct patient positioning immediately before each treatment fraction. However, the use of fiducials requires an invasive procedure and may increase costs. We aimed to assess whether intra- or periprostatic calcifications (IPC) could be used as natural fiducials. METHODS AND MATERIALS Data on patients treated with IGRT for prostate cancer with clearly visible IPC and implanted fiducials in both planning CT and MVCBCT images were reviewed. IPC were classified as central when inside the prostate and peripheral when within the planning target volume. Daily deviations in lateral, longitudinal, and vertical directions from baseline positioning using fiducials and using IPC were compared. RESULTS A total of 287 MVCBCT images were obtained and analyzed from 10 patients. The mean ± standard deviation daily deviation (mm) in the lateral, longitudinal, and vertical coordinates were 0.55 ± 3.11, 0.58 ± 3.45, and -0.54 ± 4.03, respectively, for fiducials, and 0.72 ± 3.22, 0.63 ± 3.58, and -0.69 ± 4.26, for IPC. The p values for comparisons (fiducials vs. IPC) were 0.003, 0.653, and 0.078 for lateral, longitudinal, and vertical coordinates, respectively. When cases with central IPC were analyzed (n = 7), no significant difference was found in such comparisons. Central IPC and fiducials exhibited a similar pattern of displacement during treatment, with equal values for daily displacements in the three directions for more than 90% of measurements. CONCLUSIONS Our data suggest that centrally located IPC may be used as natural fiducials for treatment positioning during IGRT for prostate cancer, with potential reductions in the risks and costs associated with fiducial implantation.

Spine radiosurgery for the local treatment of spine metastases: Intensity-modulated radiotherapy, image guidance, clinical aspects and future directions

Many cancer patients will develop spinal metastases. Local control is important for preventing neurologic compromise and to relieve pain. Stereotactic body radiotherapy or spinal radiosurgery is a new radiation therapy technique for spinal metastasis that can deliver a high dose of radiation to a tumor while minimizing the radiation delivered to healthy, neighboring tissues. This treatment is based on intensity-modulated radiotherapy, image guidance and rigid immobilization. Spinal radiosurgery is an increasingly utilized treatment method that improves local control and pain relief after delivering ablative doses of radiation. Here, we present a review highlighting the use of spinal radiosurgery for the treatment of metastatic tumors of the spine. The data used in the review were collected from both published studies and ongoing trials. We found that spinal radiosurgery is safe and provides excellent tumor control (up to 94% local control) and pain relief (up to 96%), independent of histology. Extensive data regarding clinical outcomes are available; however, this information has primarily been generated from retrospective and nonrandomized prospective series. Currently, two randomized trials are enrolling patients to study clinical applications of fractionation schedules spinal Radiosurgery. Additionally, a phase I clinical trial is being conducted to assess the safety of concurrent stereotactic body radiotherapy and ipilimumab for spinal metastases. Clinical trials to refine clinical indications and dose fractionation are ongoing. The concomitant use of targeted agents may produce better outcomes in the future.

Educación a Distancia (EaD) en Física Médica

A formacao inicial e continuada de profissionais de fisica medica possui caracteristicas peculiares por ser uma area interdisciplinar, de evolucao tecnologica constante. Em paises como o Brasil, existem barreiras como: pequeno numero de profissionais, geograficamente mal distribuidos, baixos recursos financeiros, e poucas opcoes em termos de acesso a informacao, dificultando a incorporacao e disseminacao de novas tecnicas que impactam na qualidade do atendimento em saude. Esta revisao da literatura se propos a avaliar o papel da EaD na educacao de fisicos medicos, retratando sua aplicabilidade mediante a identificacao de experiencias relevantes. Os trabalhos mostram que a EaD tem caracteristicas interessantes para a area, tais como alta efetividade pedagogica e eficiencia economica, possibilitando o uso massivo de recursos multimidia, com grande abrangencia geografica e de forma gerenciavel. Portanto tem potencial para superar as barreiras e suprir carencias da area.

Determination of the Uncertainty in the Cross-calibration of an Ionization Chamber Used in Radiation Therapy

It was performed an analysis of the uncertainties involved in a cross-calibration procedure of an ionization chamber used in Sirio-Libanes Hospital, according to the methodology proposed in IAEA-TECDOC-1585, based on ISO GUM. The overall uncertainty obtained was 2,55% (coverage factor k = 2), which meant an increase of 0,04% compared to the reference ionization chamber uncertainty reported by the dosimetry laboratory of LCI-GMR-IPEN/CNEN-SP.

Feasibility study of using epitaxial silicon diodes for clinical electron and photon beams dosimetry

In this work the feasibility of using epitaxial (EPI) silicon diodes for clinical dosimetry was studied with a Siemens Primus Linear Accelerator from Sírio-Libanês Hospital. Three samples of EPI diodes were investigated, concerning the influence of pre-irradiation on their response as on-line clinical photon and electron beam dosimeter. All measurements were performed with the diodes unbiased, operating in the direct current mode and inserted into a PMMA phantom. The dynamic current responses of the diodes under irradiation with electron beams in the energy range of 6 MeV-21 MeV and photon beams of the 6 and 18 MV were measured at different dose-rates. The dose-response curves of the diodes are quite linear in the range of zero up to 29.54 kGy for electrons and evaluated from 63 cGy up to 370 cGy for photon beams. The percentage depth dose profile (PDD) and transversal dose profile (TDP) for both electron and photon beams were also measured in PMMA with the EPI diodes. The results were in excellent agreement with those calculated with Monte Carlo code using the Oncentra MasterPlan® Treatment Planning System (TPS). The TDP was also evaluated with a commercialized array of 2D pixel ionization chambers MatriXX from IBA Dosimetry®.

A comparison between Rad‐Hard Standard Float Zone (FZ) and Magnetic Czochralski (MCz) Silicon Diodes in Radiotherapy Electron Beams Dosimetry

In this work we present the preliminary results obtained with a comparison between rad‐hard FZ and MCz silicon diodes as on‐line clinical electron beams dosimeters. The dynamic current response of the diodes under irradiation with electron beams within the energy range of 6 MeV up to 21 MeV was investigated. For all energies, data show good instantaneous repeatability of the diodes, characterized by coefficients of variation better than 2.8% and 2.5% to FZ and MCz, respectively. The dose‐response curves of both diodes are quite linear with charge sensitivities better than 0.55 μC/Gy and 0.68 μC/Gy to FZ and MCz devices. These results show that MCz diode is more sensitive than FZ diode.

Educação a Distância (EaD) em Física Médica

A formacao inicial e continuada de profissionais de fisica medica possui caracteristicas peculiares por ser uma area interdisciplinar, de evolucao tecnologica constante. Em paises como o Brasil, existem barreiras como: pequeno numero de profissionais, geograficamente mal distribuidos, baixos recursos financeiros, e poucas opcoes em termos de acesso a informacao, dificultando a incorporacao e disseminacao de novas tecnicas que impactam na qualidade do atendimento em saude. Esta revisao da literatura se propos a avaliar o papel da EaD na educacao de fisicos medicos, retratando sua aplicabilidade mediante a identificacao de experiencias relevantes. Os trabalhos mostram que a EaD tem caracteristicas interessantes para a area, tais como alta efetividade pedagogica e eficiencia economica, possibilitando o uso massivo de recursos multimidia, com grande abrangencia geografica e de forma gerenciavel. Portanto tem potencial para superar as barreiras e suprir carencias da area.

Distance education within medical physics

A formacao inicial e continuada de profissionais de fisica medica possui caracteristicas peculiares por ser uma area interdisciplinar, de evolucao tecnologica constante. Em paises como o Brasil, existem barreiras como: pequeno numero de profissionais, geograficamente mal distribuidos, baixos recursos financeiros, e poucas opcoes em termos de acesso a informacao, dificultando a incorporacao e disseminacao de novas tecnicas que impactam na qualidade do atendimento em saude. Esta revisao da literatura se propos a avaliar o papel da EaD na educacao de fisicos medicos, retratando sua aplicabilidade mediante a identificacao de experiencias relevantes. Os trabalhos mostram que a EaD tem caracteristicas interessantes para a area, tais como alta efetividade pedagogica e eficiencia economica, possibilitando o uso massivo de recursos multimidia, com grande abrangencia geografica e de forma gerenciavel. Portanto tem potencial para superar as barreiras e suprir carencias da area.