Improvement of the penumbra for small radiosurgical fields using flattening filter free low megavoltage beams.

Background: In stereotactic radiosurgery, sharp beam edges have clear advantages to spare normal tissues. In general, the dose gradient is a limiting factor in minimizing dose to nearby critical structures for clinical cases. Therefore the penumbral width should be diminished.

Optimization of three dimensional planning dosimetric in breast phantom for match region of supraclavicular and tangential fields.

Aim: Complex geometry of breast tissue causes perturbation in dose distribution. This problem can beget overdose or under-dose points in match region of three fields. The aim of this study is to create dose homogeneity distribution in match region between tangential and supraclavicular fields (SCF) with Gafchromic external beam therapy (EBT) film.

EBT GAFCHROMIC(TM) film dosimetry in compensator-based intensity modulated radiation therapy.

The electron benefit transfer (EBT) GAFCHROMIC films possess a number of features making them appropriate for high-quality dosimetry in intensity-modulated radiation therapy (IMRT). Compensators to deliver IMRT are known to change the beam-energy spectrum as well as to produce scattered photons and to contaminate electrons; therefore, the accuracy and validity of EBT-film dosimetry in compensator-based IMRT should be investigated. Percentage-depth doses and lateral-beam profiles were measured using EBT films in perpendicular orientation with respect to 6 and 18 MV photon beam energies for: (1) different thicknesses of cerrobend slab (open, 1.

In vivo dosimetry with semiconductors in medium dose rate (MDR) brachytherapy for cervical cancer.

Purpose: This study was performed to evaluate the role of in vivo dosimetry with semiconductor detectors in gynaecological medium dose rate brachytherapy, and to compare the actual doses delivered to organs at risk (as measured using in vivo dosimetry) with those calculated during treatment planning.

Materials And Methods: Doses to the rectum and bladder were measured in a group of patients with cervical carcinoma using semiconductor detectors and compared to the doses calculated using a treatment planning system. 36 applications of brachytherapy at dose rates of 1.

The effect of rib and lung heterogeneities on the computed dose to lung in Ir-192 high-dose-rate breast brachytherapy: Monte Carlo versus a treatment planning system.

Aims: This study investigates to what extent the dose received by lungs from a commercially available treatment planning system, Ir-192 high-dose-rate (HDR), in breast brachytherapy, is accurate, with the emphasis on tissue heterogeneities, and taking into account the presence of ribs, in dose delivery to the lung.

Materials And Methods: A computed tomography (CT) scan of a breast was acquired and transferred to the 3-D treatment planning system and was also used to construct a patient-equivalent phantom. An implant involving 13 plastic catheters and 383 programmed source dwell positions were simulated, using the Monte Carlo N-Particle eXtended (MCNPX) code.

Evaluation of off-axis wedge correction factor using diode dosimeters for estimation of delivered dose in external radiotherapy.

An in vivo dosimetry system, using p-type diode dosimeters, was characterized for clinical applications of treatment machines ranging in megavoltage energies. This paper investigates two different models of diodes for externally wedged beams and explains a new algorithm for the calculation of the target dose at various tissue depths in external radiotherapy. The values of off-axis wedge correction factors were determined at two different positions in the wedged (toward the thick and thin edges) and in the non-wedged directions on entrance and exit surfaces of a polystyrene phantom in (60)Co and 6 MV photon beams.

Evaluation of treatment planning system of brachytherapy according to dose to the rectum delivered.

The aim of this study was to assess the actual dose delivered to the rectum and compare it with the treatment planning system (TPS) reports. In this study, the dose delivered to the rectum was measured by semiconductor diode detectors (PTW, Germany). The factors that influence diode response were investigated as well.

Differential dose volume histograms of Gamma knife in the presence of inhomogeneities using MRI-polymer gel dosimetry and MC simulation.

Polymer gel dosimeters offer a practical solution to 3D dose verification for conventional radiotherapy as well as intensity-modulated and stereotactic radiotherapy. In this study, EGSnrc calculated and PAGAT polymer gel dosimeter measured dose volume histograms (DVHs) for single-shot irradiations of the Gamma Knife (GK) unit were used to investigate the effects of the presence of inhomogeneities on 3D dose distribution. The head phantom was a custom-built 16 cm diameter Plexiglas sphere.

Monte Carlo estimation of photoneutrons contamination from high-energy X-ray medical accelerators in treatment room and maze: a simplified model.

Despite all advantages associated with high-energy radiotherapy to improve therapeutic gain, the production of photoneutron via interaction of high-energy photons with high atomic number (Z) materials increases undesired dose to the patient and staff. Owing to the limitation and complication of experimental neutron dosimetry in mixed beam environment, including photon and neutron, the Monte Carlo (MC) simulation is a gold standard method for calculation of photoneutron contaminations. On the other hand, the complexity of treatment head makes the MC simulation more difficult and time-consuming.

Determination of human absorbed dose of 67GA-DTPA-ACTH based on distribution data in rats.

The absorbed radiation dose to human organs has been estimated, following intravenous administration of (67)Ga-labelled adrenocorticotrophic hormone (ACTH) using distribution data from injected normal rats. Four rats were sacrificed at exact time intervals and the percentage of injected dose per gram of each organ was measured by direct counting from rat data. The Medical Internal Radiation Dose formulation was applied to extrapolate from rat to human and to project the absorbed radiation dose for various organs in a human.

Gamma knife radiosurgery in patients with trigeminal neuralgia: quality of life, outcomes, and complications.

Objective: to assess the outcomes, complications, and alteration in quality of life (QOL) in patients with trigeminal neuralgia who were treated with gamma knife radiosurgery (GKRS) in a prospective observational study.

Methods And Materials: between June 2006 and May 2007, 30 patients of medically refractory trigeminal neuralgia were included in our study and treated with GKRS at Iran Gamma Knife Centre (IGKC), Tehran, Iran. A median maximum prescription dose of 90Gy (range: 85-95) was delivered to the trigeminal nerve root entry zone.

Performance evaluation of MRI-based PAGAT polymer gel dosimeter in an inhomogeneous phantom using EGSnrc code on a Co-60 machine.

Relative isodose curves were obtained using PAGAT gel dosimeter on homogeneous and inhomogeneous phantoms. Distance-to-agreement (DTA) was calculated between simulated and measured values for both the homogeneous and inhomogeneous phantoms. All DTAs except one passed the acceptance criterion (+/-5 dose variation for selected isodose levels).

Dosimetry and verification of Co total body irradiation with human phantom and semiconductor diodes.

Total Body Irradiation (TBI) is a form of radiotherapy used for patients prior to bone marrow or stem cell transplant to destroy any undetectable cancer cells. The dosimetry characteristics of a (60)Co unit for TBI were studied and a simple method for the calculation of the prescribed dose for TBI is presented. Dose homogeneity was verified in a human phantom.

Radiosurgery for glomus jugulare tumors: experience treating 16 patients in Iran.

Object: Glomus jugulare tumors (GJT) have traditionally been treated by surgery or fractionated external-beam radiotherapy. The aim of this retrospective study was to determine the tumor control rate, clinical outcome, and short-term complications of stereotactic radiosurgery in subsets of patients who are poor candidates for these procedures, based on age, medical problems, tumor size, or prior treatment failure.

Methods: The Leksell Gamma Knife was used to treat 16 patients harboring symptomatic, residual, recurrent, or unresectable GJTs.

Monte carlo dose calculations in conventional thorax fields for 60Co photons.

Purpose: Our purpose was to apply the MCNP4C Monte Carlo (MC) code for dose calculations in the thorax region and compare the results with those of measurements and a conventional treatment planning system (TPS).

Materials And Methods: We modeled a Theratron 780E 60Co unit and benchmarked our modeling with percent depth doses (PDDs), beam profiles, and output factors measured in a water phantom. For PDDs and beam profiles, the differences between measurements and MC calculations were less than 1% and 2%, respectively.

Monte Carlo calculation of Varian 2300C/D Linac photon beam characteristics: a comparison between MCNP4C, GEANT3 and measurements.

Different codes are used for Monte Carlo (MC) calculations in radiation therapy. In this research, MCNP4C and GEANT3 codes have been compared in calculations of dosimetric characteristics of Varian Clinac 2300C/D. The parameters of influence in the differences seen in dosimetric features were discussed.