Effect of Brachytherapy With External Beam Radiation Therapy Versus Brachytherapy Alone for Intermediate-Risk Prostate Cancer: NRG Oncology RTOG 0232 Randomized Clinical Trial.

PURPOSE: To determine whether addition of external beam radiation therapy (EBRT) to brachytherapy (BT) (COMBO) compared with BT alone would improve 5-year freedom from progression (FFP) in intermediate-risk prostate cancer. METHODS: Men with prostate cancer stage cT1c-T2bN0M0, Gleason Score (GS) 2-6 and prostate-specific antigen (PSA) 10-20 or GS 7, and PSA < 10 were eligible. The COMBO arm was EBRT (45 Gy in 25 fractions) to prostate and seminal vesicles followed by BT prostate boost (110 Gy if 125-Iodine, 100 Gy if 103-Pd). BT arm was delivered to prostate only (145 Gy if 125-Iodine, 125 Gy if 103-Pd). The primary end point was FFP: PSA failure (American Society for Therapeutic Radiology and Oncology [ASTRO] or Phoenix definitions), local failure, distant failure, or death. RESULTS: Five hundred eighty-eight men were randomly assigned; 579 were eligible: 287 and 292 in COMBO and BT arms, respectively. The median age was 67 years; 89.1% had PSA < 10 ng/mL, 89.1% had GS 7, and 66.7% had T1 disease. There were no differences in FFP. The 5-year FFP-ASTRO was 85.6% (95% CI, 81.4 to 89.7) with COMBO compared with 82.7% (95% CI, 78.3 to 87.1) with BT (odds ratio [OR], 0.80; 95% CI, 0.51 to 1.26; Greenwood T P = .18). The 5-year FFP-Phoenix was 88.0% (95% CI, 84.2 to 91.9) with COMBO compared with 85.5% (95% CI, 81.3 to 89.6) with BT (OR, 0.80; 95% CI, 0.49 to 1.30; Greenwood T P = .19). There were no differences in the rates of genitourinary (GU) or GI acute toxicities. The 5-year cumulative incidence for late GU/GI grade 2+ toxicity is 42.8% (95% CI, 37.0 to 48.6) for COMBO compared with 25.8% (95% CI, 20.9 to 31.0) for BT (P < .0001). The 5-year cumulative incidence for late GU/GI grade 3+ toxicity is 8.2% (95% CI, 5.4 to 11.8) compared with 3.8% (95% CI, 2.0 to 6.5; P = .006). CONCLUSION: Compared with BT, COMBO did not improve FFP for prostate cancer but caused greater toxicity. BT alone can be considered as a standard treatment for men with intermediate-risk prostate cancer.

The International Organization for Medical Physics - a driving force for the global development of medical physics.

The International Organization for Medical Physics (IOMP) is the world's largest professional organization in the field of medical physics and has official non-governmental organization status with the World Health Organization (WHO) and the International Atomic Energy Agency (IAEA). IOMP is charged with a mission to advance medical physics practice worldwide by disseminating scientific and technical information, fostering the educational and professional development of medical physics and promoting the highest quality medical services for patients. IOMP's activities are directed towards the promotion of medical physics globally, improving patient care, and contributing to the benefit of healthcare to the society. Major organizational activities include but are not limited to scientific events, international collaborations, dissemination of information, education, training, and research. For nearly 60 years of existence, IOMP turned into a key factor not only in the field of medical physics, but also healthcare, and other related disciplines. IOMP is looking forward to future perspectives in international collaboration and enhancement of the professional skills, all directed towards enhancing patient benefit.

Medical physicist certification and training program accreditation.

As a profession, medical physics combines an advanced understanding of physics and math with knowledge of biology, anatomy and physiology. Consequently, rigorous education and training is required to assure that medical physicists have the requisite fundamental knowledge, specialized technical skills, and clinical understanding to contribute to the medical care of patients safely. There is, therefore, an interest in standardizing the educational pathways and in developing mechanisms to assure that competency is achieved and maintained. Throughout the world, several countries, regions, and professional organizations have developed mechanisms for accrediting medical physics educational programs, both for didactic work performed in undergraduate or post-graduate settings, and for clinical training conducted in hospitals and clinics. In addition, several national and international programs exist for certifying individual medical physicists. In some cases, once initial certification is achieved, the diplomate enters a program of maintenance of certification, to ensure that the skills obtained during training are not lost over a career. This article explores the differences and similarities in the training program accreditation and physicist certification mechanisms.

Patient doses from image-guided radiation therapy.

Recent publications show that some patients receive high cumulative radiation doses from recurrent CT examinations. Most of these patients had a diagnosis of malignancy, meaning that there was a likelihood that they would receive radiation therapy, possibly with image guidance. Patients receiving X-ray-based image-guided radiation therapy (IGRT) receive even more imaging dose, including to volumes of tissue outside the tumor target volume. The benefits of IGRT must be considered in light of the additional dose received. Monitoring and recording of the imaging dose should be considered, as should techniques to reduce both the dose and volume irradiated.

Low-density gel dosimeter for measurement of the electron return effect in an MR-linac.

Radiation therapy in the presence of a strong magnetic field is known to cause regions of enhanced and reduced dose at interfaces of materials with varying densities, in a phenomenon known as the electron return effect (ERE). In this study, a novel low-density gel dosimeter was developed to simulate lung tissue and was used to measure the ERE at the lung-soft tissue interface. Low-density gel dosimeters were developed with Fricke xylenol orange gelatin (FXG) and ferrous oxide xylenol orange (FOX) gels mixed with polystyrene foam beads of various sizes. The gels were characterized based on CT number, MR signal intensity, and uniformity. All low-density gels had CT numbers roughly equivalent to lung tissue. The optimal lung-equivalent gel formulation was determined to be FXG with <1 mm polystyrene beads due to the higher signal intensity of FXG compared to FOX and the higher uniformity with the small beads. Dose response curves were generated for the optimal low-density gel and conventional FXG. The change in spin-lattice relaxation rate (R1) before and after irradiation was linear with dose for both gels. Next, phantoms consisting of concentric cylinders with low-density and conventional FXG were created to simulate the lung-soft tissue interface. The phantoms were irradiated in a conventional linear accelerator (linac) and in a linac combined with a 1.5 T magnetic resonance imaging (MRI) unit (MR-linac) to measure the effects of the magnetic field on the dose distribution. Hot and cold spots were observed in the dose distribution at the boundaries between the gels for the phantom irradiated in the MR-linac but not the conventional linac, consistent with the ERE.

Simultaneous motion monitoring and truth-in-delivery analysis imaging framework for MR-guided radiotherapy.

Intrafraction motion (i.e. motion occurring during a treatment session) can play a pivotal role in the success of abdominal and thoracic radiation therapy. Hybrid magnetic resonance-guided radiotherapy (MR-gRT) systems have the potential to control for intrafraction motion. Recently, we introduced an MRI sequence capable of acquiring real-time cine imaging in two orthogonal planes (SOPI). We extend SOPI here to permit dynamic updating of slice positions in one-plane while keeping the other plane position fixed. In this implementation, cine images from the static plane are used for motion monitoring and as image navigators to sort stepped images in the other plane, producing dynamic 4D image volumes for use in dose reconstruction. A custom 3D-printed target, designed to mimic the pancreas and duodenum and filled with radiochromic FXG gel, was interfaced to the dynamic motion phantom. 4D-SOPI was acquired in a dynamic motion phantom driven by an actual patient respiratory waveform displaying amplitude/frequency variations and drifting and in a healthy volunteer. Unique 4D-MRI epochs were reconstructed from a time series of phantom motion. Dose from a static 4 cm × 15 cm field was calculated on each 4D respiratory phase bin and epoch image, scaled by the time spent in each bin, and then rigidly accumulated. The phantom was then positioned on an Elekta MR-Linac and irradiated while moving. Following irradiation, actual dose deposited to the FXG gel was determined by applying a R 1 versus dose calibration curve to R 1 maps of the phantom. The 4D-SOPI cine images produced a respiratory motion navigator that was highly correlated with the actual phantom motion (CC = 0.9981). The mean difference between the accumulated and measured dose inside the target was 4.4% of the maximum prescribed dose. These initial results demonstrate that 4D-SOPI is a promising imaging framework enabling simultaneous real-time motion monitoring and truth-in-delivery analysis for integrated MR-gRT systems.

Dosimetric, Radiobiological and Secondary Cancer Risk Evaluation in Head-and-Neck Three-dimensional Conformal Radiation Therapy, Intensity-Modulated Radiation Therapy, and Volumetric Modulated Arc Therapy: A Phantom Study.

This analysis estimated secondary cancer risks after volumetric modulated arc therapy (VMAT) and compared those risks to the risks associated with other modalities of head-and-neck (H&N) radiotherapy. Images of H&N anthropomorphic phantom were acquired with a computed tomography scanner and exported via digital imaging and communications in medicine (DICOM) standards to a treatment planning system. Treatment plans were performed using a VMAT dual-arc technique, a nine-field intensity-modulated radiation therapy (IMRT) technique, and a four-field three-dimensional conformal therapy (3DCRT) technique. The prescription dose was 66.0 Gy for all three techniques, but to accommodate the range of dosimeter responses, we delivered a single dose of 6.60 Gy to the isocenter. The lifetime risk for secondary cancers was estimated according to National Council on Radiation Protection and Measurements (NCRP) Report 116. VMAT delivered the lowest maximum doses to esophagus (23 Gy), and normal brain (40 Gy). In comparison, maximum doses for 3DCRT were 74% and 40%, higher than those for VMAT for the esophagus, and normal brain, respectively. The normal tissue complication probability and equivalent uniform dose for the brain (2.1%, 0.9%, 0.8% and 3.8 Gy, 2.6 Gy, 2.3 Gy) and esophagus (4.2%, 0.7%, 0.4% and 3.7 Gy, 2.2 Gy, 1.8 Gy) were calculated for the 3DCRT, IMRT and VMAT respectively. Fractional esophagus OAR volumes receiving more than 20 Gy were 3.6% for VMAT, 23.6% for IMRT, and 100% for 3DCRT. The calculations for mean doses, NTCP, EUD and OAR volumes suggest that the risk of secondary cancer induction after VMAT is lower than after IMRT and 3DCRT.

Prospective in silico study of the feasibility and dosimetric advantages of MRI-guided dose adaptation for human papillomavirus positive oropharyngeal cancer patients compared with standard IMRT.

PURPOSE: We aim to determine the feasibility and dosimetric benefits of a novel MRI-guided IMRT dose-adaption strategy for human papillomavirus positive (HPV+) oropharyngeal squamous cell carcinoma (OPC). MATERIALS/METHODS: Patients with locally advanced HPV+ OPC underwent pre-treatment and in-treatment MRIs every two weeks using RT immobilization setup. For each patient, two IMRT plans were created (i.e. standard and adaptive). The prescription dose for the standard plans was 2.12 Gy/fx for 33 fractions to the initial PTV. For adaptive plans, a new PTVadaptive was generated based on serial MRIs in case of detectable tumor shrinkage. Prescription dose to PTVadaptive was 2.12 Gy/fx to allow for maximum dose to the residual disease. Any previously involved volumes received minimally a floor dose of 50.16 Gy. Uninvolved elective nodal volumes were prescribed 50.16 Gy in 1.52 Gy/fx. Dosimetric parameters of organs at risk (OARs) were recorded for standard vs. adaptive plans. Normal tissue complication probability (NTCP) for toxicity endpoints was calculated using literature-derived multivariate logistic regression models. RESULTS: Five patients were included in this pilot study, 3 men and 2 women. Median age was 58 years (range 45-69). Three tumors originated at the tonsillar fossa and two at the base of tongue. The average dose to 95% of initial PTV volume was 70.7 Gy (SD,0.3) for standard plans vs. 58.5 Gy (SD,2.0) for adaptive plans. The majority of OARs showed decrease in dosimetric parameters using adaptive plans vs. standard plans, particularly swallowing related structures. The average reduction in the probability of developing dysphagia ≥ grade2, feeding tube persistence at 6-month post-treatment and hypothyroidism at 1-year post-treatment was 11%, 4%, and 5%, respectively. The probability of xerostomia at 6-month was only reduced by 1% for adaptive plans vs. standard IMRT. CONCLUSION: These in silico results showed that the proposed MRI-guided adaptive approach is technically feasible and advantageous in reducing dose to OARs, especially swallowing musculature.

A methodology to investigate the impact of image distortions on the radiation dose when using magnetic resonance images for planning.

We developed a novel technique to study the impact of geometric distortion of magnetic resonance imaging (MRI) on intensity-modulated radiation therapy treatment planning. The measured 3D datasets of residual geometric distortion (a 1.5 T MRI component of an MRI linear accelerator system) was fitted with a second-order polynomial model to map the spatial dependence of geometric distortions. Then the geometric distortion model was applied to computed tomography (CT) image and structure data to simulate the distortion of MRI data and structures. Fourteen CT-based treatment plans were selected from patients treated for gastrointestinal, genitourinary, thoracic, head and neck, or spinal tumors. Plans based on the distorted CT and structure data were generated (as the distorted plans). Dose deviations of the distorted plans were calculated and compared with the original plans to study the dosimetric impact of MRI distortion. The MRI geometric distortion led to notable dose deviations in five of the 14 patients, causing loss of target coverage of up to 3.68% and dose deviations to organs at risk in three patients, increasing the mean dose to the chest wall by up to 6.19 Gy in a gastrointestinal patient, and increases the maximum dose to the lung by 5.17 Gy in a thoracic patient.

Real-time volumetric relative dosimetry for magnetic resonance-image-guided radiation therapy (MR-IGRT).

The integration of magnetic resonance imaging (MRI) with linear accelerators (linac) has enabled the use of 3D MR-visible gel dosimeters for real-time verification of volumetric dose distributions. Several iron-based radiochromic 3D gels were created in-house then imaged and irradiated in a pre-clinical 1.5 T-7 MV MR-Linac. MR images were acquired using a range of balanced-fast field echo (b-FFE) sequences during irradiation to assess the contrast and dose response in irradiated regions and to minimize the presence of MR artifacts. Out of four radiochromic 3D gel formulations, the FOX 3D gel was found to provide superior MR contrast in the irradiated regions. The FOX gels responded linearly with respect to real-time dose and the signal remained stable post-irradiation for at least 20 min. The response of the FOX gel also was found to be unaffected by the radiofrequency and gradient fields created by the b-FFE sequence during irradiation. A reusable version of the FOX gel was used for b-FFE sequence optimization to reduce artifacts by increasing the number of averages at the expense of temporal resolution. Regardless of the real-time MR sequence used, the FOX 3D gels responded linearly to dose with minimal magnetic field effects due to the strong 1.5 T field or gradient fields present during imaging. These gels can easily be made in-house using non-reusable and reusable formulations depending on the needs of the clinic, and the results of this study encourage further applications of 3D gels for MR-IGRT applications.

Assessment of image quality and scatter and leakage radiation of an integrated MR-LINAC system.

PURPOSE: To assess the image quality, scatter, and leakage radiation of an integrated magnetic resonance linear accelerator (MR-LINAC or MRL) system. METHODS: A large American College of Radiology (ACR) magnetic resonance imaging (MRI) accreditation phantom was used to evaluate the MRI capabilities of the integrated MRL system compared with those of other diagnostic MRI systems. Multiple sets of T1 and T2/PD images were acquired with the linear accelerator positioned at various angles and with the radiation beam on and off. Images also were acquired on three different occasions over a period of about 12 months. Scatter and leakage radiation were measured with a large (150 cm3 ) ion chamber recalibrated for MV energy. For scatter measurements, a 25-cm stack of solid-water materials was placed at the isocenter on the patient couch to simulate a patient. The head leakage was measured at 1 m from the linear accelerator head in directions determined to produce the maximum leakage. All measurements were repeated with the magnetic field turned off to study the effects of the magnetic field. RESULTS: The geometric distortion, slice thickness accuracy, image uniformity, ghosting ratio, and high-contrast detectability were comparable to other 1.5 T diagnostic MRI scanners. No observable changes in image quality and no appreciable differences were found between radiation beam-on and beam-off images. The measured leakage and scattered radiation changed by less than 5% when the magnetic field was on compared to measurements with the field off. The beam stopper leakage was approximately 0.3 R/1000 MU, and because there was no direct beam imparted on the walls, a vault designed for a modern-day LINAC should have enough required radiation shielding to house the MRL. CONCLUSIONS: The image quality generated by the MRI system of the integrated MRL was similar to that of a diagnostic MRI scanner. Interference from the MV radiation was minimal, and there was no measurable difference in image quality with the beam on and off. Scatter radiation and leakage radiation of the MRL system were within the expected range of a comparable MV-LINAC.

Iron-based radiochromic systems for UV dosimetry applications.

Phototherapy treatment using ultraviolet (UV) A and B light sources has long existed as a treatment option for various skin conditions. Quality control for phototherapy treatment recommended by the British Association of Dermatologists and British Photodermatology Group generally focused on instrumentation-based dosimetry measurements. The purpose of this study was to present an alternative, easily prepared dosimeter system for the measurement of UV dose and as a simple quality assurance technique for phototherapy treatments. Five different UVA-sensitive radiochromic dosimeter formulations were investigated and responded with a measurable and visible optical change both in solution and in gel form. Iron(III) reduction reaction formulations were found to be more sensitive to UVA compared to iron(II) oxidation formulations. One iron(III) reduction formulation was found to be especially promising due to its sensitivity to UVA dose, ease of production, and linear response up to a saturation point.

Model for Estimating Power and Downtime Effects on Teletherapy Units in Low-Resource Settings.

PURPOSE: More than 6,500 megavoltage teletherapy units are needed worldwide, many in low-resource settings. Cobalt-60 units or linear accelerators (linacs) can fill this need. We have evaluated machine performance on the basis of patient throughput to provide insight into machine viability under various conditions in such a way that conclusions can be generalized to a vast array of clinical scenarios. MATERIALS AND METHODS: Data from patient treatment plans, peer-reviewed studies, and international organizations were combined to assess the relative patient throughput of linacs and cobalt-60 units that deliver radiotherapy with standard techniques under various power and maintenance support conditions. Data concerning the frequency and duration of power outages and downtime characteristics of the machines were used to model teletherapy operation in low-resource settings. RESULTS: Modeled average daily throughput was decreased for linacs because of lack of power infrastructure and for cobalt-60 units because of limited and decaying source strength. For conformal radiotherapy delivered with multileaf collimators, average daily patient throughput over 8 years of operation was equal for cobalt-60 units and linacs when an average of 1.83 hours of power outage occurred per 10-hour working day. Relative to conformal treatments delivered with multileaf collimators on the respective machines, the use of advanced techniques on linacs decreased throughput between 20% and 32% and, for cobalt machines, the need to manually place blocks reduced throughput up to 37%. CONCLUSION: Our patient throughput data indicate that cobalt-60 units are generally best suited for implementation when machine operation might be 70% or less of total operable time because of power outages or mechanical repair. However, each implementation scenario is unique and requires consideration of all variables affecting implementation.

Navigating the medical physics education and training landscape.

PURPOSE: The education and training landscape has been profoundly reshaped by the ABR 2012/2014 initiative and the MedPhys Match. This work quantifies these changes and summarizes available reports, surveys, and statistics on education and training. METHODS: We evaluate data from CAMPEP-accredited program websites, annual CAMPEP graduate and residency program reports, and surveys on the MedPhys Match and Professional Doctorate degree (DMP). RESULTS: From 2009-2015, the number of graduates from CAMPEP-accredited graduate programs rose from 210 to 332, while CAMPEP-accredited residency positions rose from 60 to 134. We estimate that approximately 60% of graduates of CAMPEP-accredited graduate programs intend to enter clinical practice, however, only 36% of graduates were successful in acquiring a residency position in 2015. The maximum residency placement percentage for a graduate program is 70%, while the median for all programs is only 22%. Overall residency placement percentage for CAMPEP-accredited program graduates from 2011-2015 was approximately 38% and 25% for those with a PhD and MS, respectively. The disparity between the number of clinically oriented graduates and available residency positions is perceived as a significant problem by over 70% of MedPhys Match participants responding to a post-match survey. Approximately 32% of these respondents indicated that prior knowledge of this situation would have changed their decision to pursue graduate education in medical physics. CONCLUSION: These data reveal a substantial disparity between the number of residency training positions and graduate students interested in these positions, and a substantial variability in residency placement percentage across graduate programs. Comprehensive data regarding current and projected supply and demand within the medical physics workforce are needed for perspective on these numbers. While the long-term effects of changes in the education and training infrastructure are still unclear, available survey data suggest that these changes could negatively affect potential entrants to the profession.

Investigation of magnetic field effects on the dose-response of 3D dosimeters for magnetic resonance - image guided radiation therapy applications.

BACKGROUND AND PURPOSE: The strong magnetic field of integrated magnetic resonance imaging (MRI) and radiation treatment systems influences secondary electrons resulting in changes in dose deposition in three dimensions. To fill the need for volumetric dose quality assurance, we investigated the effects of strong magnetic fields on 3D dosimeters for MR-image-guided radiation therapy (MR-IGRT) applications. MATERIAL AND METHODS: There are currently three main categories of 3D dosimeters, and the following were used in this study: radiochromic plastic (PRESAGE®), radiochromic gel (FOX), and polymer gel (BANG™). For the purposes of batch consistency, an electromagnet was used for same-day irradiations with and without a strong magnetic field (B0, 1.5T for PRESAGE® and FOX and 1.0T for BANG™). RESULTS: For PRESAGE®, the percent difference in optical signal with and without B0 was 1.5% at the spectral peak of 632nm. For FOX, the optical signal percent difference was 1.6% at 440nm and 0.5% at 585nm. For BANG™, the percent difference in R2 MR signal was 0.7%. CONCLUSIONS: The percent differences in responses with and without strong magnetic fields were minimal for all three 3D dosimeter systems. These 3D dosimeters therefore can be applied to MR-IGRT without requiring a correction factor.

Development of a flattening filter free multiple source model for use as an independent, Monte Carlo, dose calculation, quality assurance tool for clinical trials.

PURPOSE: The Imaging and Radiation Oncology Core-Houston (IROC-H) Quality Assurance Center (formerly the Radiological Physics Center) has reported varying levels of compliance from their anthropomorphic phantom auditing program. IROC-H studies have suggested that one source of disagreement between institution submitted calculated doses and measurement is the accuracy of the institution's treatment planning system dose calculations and heterogeneity corrections used. In order to audit this step of the radiation therapy treatment process, an independent dose calculation tool is needed. METHODS: Monte Carlo multiple source models for Varian flattening filter free (FFF) 6 MV and FFF 10 MV therapeutic x-ray beams were commissioned based on central axis depth dose data from a 10 × 10 cm2 field size and dose profiles for a 40 × 40 cm2 field size. The models were validated against open-field measurements in a water tank for field sizes ranging from 3 × 3 cm2 to 40 × 40 cm2 . The models were then benchmarked against IROC-H's anthropomorphic head and neck phantom and lung phantom measurements. RESULTS: Validation results, assessed with a ±2%/2 mm gamma criterion, showed average agreement of 99.9% and 99.0% for central axis depth dose data for FFF 6 MV and FFF 10 MV models, respectively. Dose profile agreement using the same evaluation technique averaged 97.8% and 97.9% for the respective models. Phantom benchmarking comparisons were evaluated with a ±3%/2 mm gamma criterion, and agreement averaged 90.1% and 90.8% for the respective models. CONCLUSIONS: Multiple source models for Varian FFF 6 MV and FFF 10 MV beams have been developed, validated, and benchmarked for inclusion in an independent dose calculation quality assurance tool for use in clinical trial audits.

Development of a Monte Carlo multiple source model for inclusion in a dose calculation auditing tool.

PURPOSE: The Imaging and Radiation Oncology Core Houston (IROC-H) (formerly the Radiological Physics Center) has reported varying levels of agreement in their anthropomorphic phantom audits. There is reason to believe one source of error in this observed disagreement is the accuracy of the dose calculation algorithms and heterogeneity corrections used. To audit this component of the radiotherapy treatment process, an independent dose calculation tool is needed. METHODS: Monte Carlo multiple source models for Elekta 6 MV and 10 MV therapeutic x-ray beams were commissioned based on measurement of central axis depth dose data for a 10 × 10 cm2 field size and dose profiles for a 40 × 40 cm2 field size. The models were validated against open field measurements consisting of depth dose data and dose profiles for field sizes ranging from 3 × 3 cm2 to 30 × 30 cm2 . The models were then benchmarked against measurements in IROC-H's anthropomorphic head and neck and lung phantoms. RESULTS: Validation results showed 97.9% and 96.8% of depth dose data passed a ±2% Van Dyk criterion for 6 MV and 10 MV models respectively. Dose profile comparisons showed an average agreement using a ±2%/2 mm criterion of 98.0% and 99.0% for 6 MV and 10 MV models respectively. Phantom plan comparisons were evaluated using ±3%/2 mm gamma criterion, and averaged passing rates between Monte Carlo and measurements were 87.4% and 89.9% for 6 MV and 10 MV models respectively. CONCLUSIONS: Accurate multiple source models for Elekta 6 MV and 10 MV x-ray beams have been developed for inclusion in an independent dose calculation tool for use in clinical trial audits.

Supplement 2 for the 2004 update of the AAPM Task Group No. 43 Report: Joint recommendations by the AAPM and GEC-ESTRO.

Since the publication of the 2004 update to the American Association of Physicists in Medicine (AAPM) Task Group No. 43 Report (TG-43U1) and its 2007 supplement (TG-43U1S1), several new low-energy photon-emitting brachytherapy sources have become available. Many of these sources have satisfied the AAPM prerequisites for routine clinical purposes and are posted on the Brachytherapy Source Registry managed jointly by the AAPM and the Imaging and Radiation Oncology Core Houston Quality Assurance Center (IROC Houston). Given increasingly closer interactions among physicists in North America and Europe, the AAPM and the Groupe Européen de Curiethérapie-European Society for Radiotherapy & Oncology (GEC-ESTRO) have prepared another supplement containing recommended brachytherapy dosimetry parameters for eleven low-energy photon-emitting brachytherapy sources. The current report presents consensus datasets approved by the AAPM and GEC-ESTRO. The following sources are included: 125 I sources (BEBIG model I25.S17, BEBIG model I25.S17plus, BEBIG model I25.S18, Elekta model 130.002, Oncura model 9011, and Theragenics model AgX100); 103 Pd sources (CivaTech Oncology model CS10, IBt model 1031L, IBt model 1032P, and IsoAid model IAPd-103A); and 131 Cs (IsoRay Medical model CS-1 Rev2). Observations are included on the behavior of these dosimetry parameters as a function of radionuclide. Recommendations are presented on the selection of dosimetry parameters, such as from societal reports issuing consensus datasets (e.g., TG-43U1, AAPM Report #229), the joint AAPM/IROC Houston Registry, the GEC-ESTRO website, the Carleton University website, and those included in software releases from vendors of treatment planning systems. Aspects such as timeliness, maintenance, and rigor of these resources are discussed. Links to reference data are provided for radionuclides (radiation spectra and half-lives) and dose scoring materials (compositions and mass densities). The recent literature is examined on photon energy response corrections for thermoluminescent dosimetry of low-energy photon-emitting brachytherapy sources. Depending upon the dosimetry parameters currently used by individual physicists, use of these recommended consensus datasets may result in changes to patient dose calculations. These changes must be carefully evaluated and reviewed with the radiation oncologist prior to their implementation.