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This study aimed to highlight the value and key findings of on-site proton audits.The authors performed 38 on-site measurement-based peer reviews of proton centers participating in National Cancer Institute-funded clinical trials. The reviews covered beam calibration, lateral and depth measurements, mechanical checks, treatment planning and clinical practice, and quality assurance (QA) practices. Program deficiencies were noted, and recommendations were made about ways institutions could improve their practices.Institutions received an average of 3 (range, 1-8) recommendations for practice improvements. The number of deficiencies did not decrease over time, highlighting the continued need for this type of peer review. The most common deficiencies were for Task Group-recommended QA compliance (97% of centers), computed tomography number (CTN) to relative linear stopping power conversion (59%), and QA procedures (53%). In addition, 32% of institutions assessed failed at least 1 lateral beam profile measurement (90% of pixels passing 3% [global]/3 mm; 10% threshold), despite passing internal QA measurements. These failures occurred for several different plan configurations (large, small, shallow, and deep targets) and at different depths in the beam path (proximal to target, central, and distal). CTN to relative linear stopping power conversion curves showed deviations at low, mid, and high CTNs and highlighted areas of inconsistency between proton centers, with many centers falling outside of 2 sigma of the mean curve of their peers. All deficiencies from the peer review were discussed with the institutions, and many implemented dosimetric treatment planning and practice changes to improve the accuracy of their system and consistency with other institutions.This peer review program has been integral in confirming and promoting consistency and best practice across proton centers for clinical trials, minimizing deviations for outcomes data.

PurposeTo test effects of positron emission tomography (PET)-based bone marrow-sparing (BMS) image-guided intensity modulated radiation therapy (IG-IMRT) on efficacy and toxicity for patients with locoregionally advanced cervical cancer.Methods and materialsIn an international phase II/III trial, patients with stage IB-IVA cervical carcinoma were treated with either PET-based BMS-IG-IMRT (PET-BMS-IMRT group) or standard image-guided IMRT (IMRT group), with concurrent cisplatin (40 mg/m2 weekly), followed by brachytherapy. The phase II component nonrandomly assigned patients to PET-BMS-IMRT or standard IMRT. The phase III trial randomized patients to PET-BMS-IMRT versus IMRT, with a primary endpoint of progression-free survival (PFS) but was closed early for futility. Phase III patients were analyzed separately and in combination with phase II patients, comparing acute hematologic toxicity, cisplatin delivery, PFS, overall survival (OS), and patterns of failure. In a post-hoc exploratory analysis, we investigated the association between pretreatment absolute lymphocyte count (ALC) and OS.ResultsIn total, 101 patients were enrolled on the phase II/III trial, including 29 enrolled in phase III (PET-BMS-IMRT group: 16; IMRT group: 13) before early closure. Median follow-up was 33 months for phase III patients and 39 months for all patients. PFS and OS at 5 years for all patients were 73.6% (95% confidence interval [CI], 64.9%-84.3%) and 84% (95% CI, 76%-92.9%]), respectively. There were no differences in number of cisplatin cycles, OS, PFS, or patterns of failure between groups for the combined cohort. The incidence of acute grade ≥ 3 neutropenia was significantly lower in the PET-BMS-IMRT group compared with IMRT for randomized patients (19% vs 54%, χ2P=.048) and in the combined cohort (13% vs 35%, χ2P=.01). Patients with pretreatment ALC ≤ 1.5 k/µL had nonsignificantly worse OS on multivariable analysis (HR 2.85; 95% CI, 0.94-8.62; adjusted P=.216), compared with patients with ALC > 1.5 k/µL. There was no difference in posttreatment ALC by treatment group.ConclusionsPET-BMS-IMRT significantly reduced acute grade ≥3 neutropenia, but not treatment-related lymphopenia, compared with standard IMRT. We found no evidence that PET-BMS-IMRT affected chemotherapy delivery or long-term outcomes, and weak evidence of an association between pretreatment ALC and OS.

Practical guidelines that are not explicit in the TG-51 protocol and its Addendum for photon beam dosimetry are presented for the implementation of the TG-51 protocol for reference dosimetry of external high-energy photon and electron beams. These guidelines pertain to: (i) measurement of depth-ionization curves required to obtain beam quality specifiers for the selection of beam quality conversion factors, (ii) considerations for the dosimetry system and specifications of a reference-class ionization chamber, (iii) commissioning a dosimetry system and frequency of measurements, (iv) positioning/aligning the water tank and ionization chamber for depth ionization and reference dose measurements, (v) requirements for ancillary equipment needed to measure charge (triaxial cables and electrometers) and to correct for environmental conditions, and (vi) translation from dose at the reference depth to that at the depth required by the treatment planning system. Procedures are identified to achieve the most accurate results (errors up to 8% have been observed) and, where applicable, a commonly used simplified procedure is described and the impact on reference dosimetry measurements is discussed so that the medical physicist can be informed on where to allocate resources.

Given the increasing availability of radiotherapy in sub-Saharan Africa, clinical trials that include radiotherapy are likely to grow. Ensuring appropriate delivery of radiotherapy through rigorous quality assurance is an important component of clinical trial execution. We reviewed the process for credentialing radiotherapy sites and radiotherapy quality assurance through the Imaging and Radiation Oncology Core (IROC) Houston Quality Assurance Center for AMC-081, a multicenter study of cisplatin and radiotherapy for women with locally advanced cervical cancer living with HIV, conducted by the AIDS Malignancy Consortium at 2 sites in South Africa and Zimbabwe.Women living with HIV with newly diagnosed stage IB2, IIA (4 cm), IIB-IVA cervical carcinoma (per 2009 FIGO) were enrolled on AMC-081. They received 3D conformal external-beam radiotherapy (EBRT) to the pelvis (41.4-45 Gy) using a linear accelerator, high dose rate brachytherapy (6-9 Gy to point A with each fraction and up to 4 fractions), and concurrent weekly cisplatin (40 mg/mAll of the 38 women enrolled on AMC-081 received +/- 5% of the protocol-specified prescribed dose of EBRT. Geometry of brachytherapy applicator placement was scored as per protocol in all implants. Doses to points A and B, ICRU bladder, or ICRU rectum required correction by IROC in50% of the implants. In the final evaluation, 58% of participants (n=22) were treated per protocol, 40% (n=15) had minor protocol deviations, and 3% (n=1) had major protocol deviations. No records were received within 60 days of treatment completion as requested in the protocol.Major radiotherapy deviations were low, but timely submission of radiotherapy data did not occur. Future studies, especially those that include specialized radiotherapy techniques such as stereotactic or intensity-modulated radiotherapy, will require pathways to ensure timely and adequate quality assurance.

PURPOSE: Sparing active bone marrow (ABM) can reduce acute hematologic toxicity in patients undergoing chemoradiotherapy for cervical cancer, but ABM segmentation based on positron emission tomography/computed tomography (PET/CT) is costly. We sought to develop an atlas-based ABM segmentation method for implementation in a prospective clinical trial. METHODS AND MATERIALS: A multiatlas was built on a training set of 144 patients and validated in 32 patients from the NRG-GY006 clinical trial. ABM for individual patients was defined as the subvolume of pelvic bone greater than the individual mean standardized uptake value on registered (18)F-fluorodeoxyglucose PET/CT images. Atlas-based and custom ABM segmentations were compared using the Dice similarity coefficient and mean distance to agreement and used to generate ABM-sparing intensity modulated radiation therapy plans. Dose-volume metrics and normal tissue complication probabilities of the two approaches were compared using linear regression. RESULTS: Atlas-based ABM volumes (mean [standard deviation], 548.4 [88.3] cm(3)) were slightly larger than custom ABM volumes (535.1 [93.2] cm(3)), with a Dice similarity coefficient of 0.73. Total pelvic bone marrow V(20) and D(mean) were systematically higher and custom ABM V(10) was systematically lower with custom-based plans (slope: 1.021 [95% confidence interval (CI), 1.005-1.037], 1.014 [95% CI, 1.006-1.022], and 0.98 [95% CI, 0.97-0.99], respectively). We found no significant differences between atlas-based and custom-based plans in bowel, rectum, bladder, femoral heads, or target dose-volume metrics. CONCLUSIONS: Atlas-based ABM segmentation can reduce pelvic bone marrow dose while achieving comparable target and other normal tissue dosimetry. This approach may allow ABM sparing in settings where PET/CT is unavailable.

The Children's Oncology Group (COG) has a strong quality assurance (QA) program managed by the Imaging and Radiation Oncology Core (IROC). This program consists of credentialing centers and providing real-time management of each case for protocol compliant target definition and radiation delivery. In the International Society of Pediatric Oncology (SIOP), the lack of an available, reliable online data platform has been a challenge and the European Society for Paediatric Oncology (SIOPE) quality and excellence in radiotherapy and imaging for children and adolescents with cancer across Europe in clinical trials (QUARTET) program currently provides QA review for prospective clinical trials. The COG and SIOP are fully committed to a QA program that ensures uniform execution of protocol treatments and provides validity of the clinical data used for analysis.

The purpose of this report is to provide detailed guidance on the dosimetry of the INTRABEAM® (Carl Zeiss Medical AG, Jena, Germany) electronic brachytherapy (eBT) system as it stands at the present time. This report has been developed by the members of American Association of Physicists in Medicine (AAPM) Task Group 292 and endorsed by the AAPM. Members of AAPM Task Group 292 on Electronic-Brachytherapy Dosimetry have reviewed pertinent publications and user manuals regarding the INTRABEAM system dosimetry and manufacturer-supplied dose calculation protocols. Formal written correspondence with Zeiss has also provided further clarification. Dose-rate calculations for the INTRABEAM system are highly dependent on choice of dosimetry protocol. Even with careful protocol selection, large uncertainties remain due to the incomplete characterization of the ionization chambers used for verification with respect to their energy dependence as well as manufacturing variations. There are two distinct sets of dose-rate data provided by Zeiss for the INTRABEAM system. One dataset (Calibration V4.0) is representative of the physical dose surrounding the source and the other dataset (TARGIT) has been adjusted to be consistent with a clinical trial named TARGIT (TARGeted Intraoperative RadioTherapy). The adjusted TARGIT doses are quite dissimilar to the physical doses, with differences ranging from 14% to 30% at the surface of a spherical applicator, depending on its diameter, and up to a factor of two at closer distances with the smaller needle applicators. In addition, ion chamber selection and associated manufacturing tolerances contribute to significant additional uncertainties. With these substantial differences in dose rates and their associated uncertainties, it is important for users to be aware of how each value is calculated and whether it is appropriate to be used for the intended treatment. If users intend to deliver doses that are the same as they were in 1998 at the onset of the TARGIT trial, then the TARGIT dose-rate tables should be used. The Calibration V4.0 dose rates may be more appropriate to use for applications other than TARGIT trial treatments, since they more closely represent the physical doses being delivered. Users should also be aware of the substantial uncertainties associated with the provided dose rates, which are due to beam hardening, chamber geometry, and selection of the point-of-measurement for a given ionization chamber. This report serves to describe the details and implications of the manufacturer-recommended dosimetry formalism for users of the INTRABEAM system.

Purpose To present the results and discuss potential insights gained through surveys on reference dosimetry practices. Methods Two surveys were sent to medical physicists to learn about the current state of reference dosimetry practices at radiation oncology clinics worldwide. A short survey designed to maximize response rate was made publicly available and distributed via the AAPM website and a medical physics list server. Another, much more involved survey, was sent to a smaller group of physicists to gain insight on detailed dosimetry practices. The questions were diverse, covering reference dosimetry practices on topics like measurements required for beam quality specification, the actual measurement of absorbed dose and ancillary equipment required like electrometers and environment monitoring measurements. Results There were 190 respondents to the short survey and seven respondents to the detailed survey. The diversity of responses indicates nonuniformity in reference dosimetry practices and differences in interpretation of reference dosimetry protocols. Conclusions The results of these surveys offer insight on clinical reference dosimetry practices and will be useful in identifying current and future needs for reference dosimetry.

Purpose To test the hypothesis that intensity modulated radiation therapy (IMRT) reduces acute hematologic and gastrointestinal (GI) toxicity for patients with locoregionally advanced cervical cancer. Methods and Materials We enrolled patients with stage IB-IVA cervical carcinoma in a single-arm phase II trial involving 8 centers internationally. All patients received weekly cisplatin concurrently with once-daily IMRT, followed by intracavitary brachytherapy, as indicated. The primary endpoint was the occurrence of either acute grade ≥3 neutropenia or clinically significant GI toxicity within 30 days of completing chemoradiation therapy. A preplanned subgroup analysis tested the hypothesis that positron emission tomography-based image-guided IMRT (IG-IMRT) would lower the risk of acute neutropenia. We also longitudinally assessed patients' changes in quality of life. Results From October 2011 to April 2015, 83 patients met the eligibility criteria and initiated protocol therapy. The median follow-up was 26.0 months. The incidence of any primary event was 26.5% (95% confidence interval [CI] 18.2%-36.9%), significantly lower than the 40% incidence hypothesized a priori from historical data ( P =.012). The incidence of grade ≥3 neutropenia and clinically significant GI toxicity was 19.3% (95% CI 12.2%-29.0%) and 12.0% (95% CI 6.7%-20.8%), respectively. Compared with patients treated without IG-IMRT (n=48), those treated with IG-IMRT (n=35) had a significantly lower incidence of grade ≥3 neutropenia (8.6% vs 27.1%; 2-sided χ 2 P =.035) and nonsignificantly lower incidence of grade ≥3 leukopenia (25.7% vs 41.7%; P =.13) and any grade ≥3 hematologic toxicity (31.4% vs 43.8%; P =.25). Conclusions IMRT reduces acute hematologic and GI toxicity compared with standard treatment, with promising therapeutic outcomes. Positron emission tomography IG-IMRT reduces the incidence of acute neutropenia.

Purpose: Accurate data regarding linear accelerator(Linac) radiation characteristics are important for treatment planning system modeling as well as regular quality assurance of the machine. The Imaging and Radiation Oncology Core-Houston (IROC-H) has measured the dosimetric characteristics of numerous machines through their on-site dosimetry review protocols. Photon data are presented and can be used as a secondary check of acquired values, as a means to verify commissioning a new machine, or in preparation for an IROC-H site visit. Methods: Photon data from IROC-H on-site reviews from 2000 to 2014 were compiled and analyzed. Specifically, data from approximately 500 Varian machines were analyzed. Each dataset consisted of point measurements of several dosimetric parameters at various locations in a water phantom to assess the percentage depth dose, jaw output factors, multileaf collimator small field output factors, off-axis factors, and wedge factors. The data were analyzed by energy and parameter, with similarly performing machine models being assimilated into classes. Common statistical metrics are presented for each machine class. Measurement data were compared against other reference data where applicable. Results: Distributions of the parameter data were shown to be robust and derive from a student’s t distribution. Based on statistical and clinical criteria, all machine models were able to be classified into two or three classes for each energy, except for 6 MV for which there were eight classes. Quantitative analysis of the measurements for 6, 10, 15, and 18 MV photon beams is presented for each parameter; supplementary material has also been made available which contains further statistical information. Conclusions: IROC-H has collected numerous data on Varian Linacs and the results of photon measurements from the past 15 years are presented. The data can be used as a comparison check of a physicist’s acquired values. Acquired values that are well outside the expected distribution should be verified by the physicist to identify whether the measurements are valid. Comparison of values to this reference data provides a redundant check to help prevent gross dosimetric treatment errors.

Purpose Reference dosimetry data can provide an independent second check of acquired values when commissioning or validating a treatment planning system (TPS). The Imaging and Radiation Oncology Core at Houston (IROC-Houston) has measured numerous linear accelerators throughout its existence. The results of those measurements are given here, comparing accelerators and the agreement of measurement versus institutional TPS calculations. Methods Data from IROC-Houston on-site reviews from 2000 through 2014 were analyzed for all Elekta accelerators, approximately 50. For each, consistent point dose measurements were conducted for several basic parameters in a water phantom, including percentage depth dose, output factors, small-field output factors, off-axis factors, and wedge factors. The results were compared by accelerator type independently for 6, 10, 15, and 18 MV. Distributions of the measurements for each parameter are given, providing the mean and standard deviation. Each accelerator's measurements were also compared to its corresponding TPS calculation from the institution to determine the level of agreement, as well as determining which dosimetric parameters were most often in error. Results Accelerators were grouped by head type and reference dosimetric values were compiled. No class of linac had better overall agreement with its TPS, but percentage depth dose and output factors commonly agreed well, while small-field output factors, off-axis factors, and wedge factors often disagreed substantially from their TPS calculations. Conclusion Reference data has been collected and analyzed for numerous Elekta linacs, which provide an independent way for a physicist to double-check their own measurements to prevent gross treatment errors. In addition, treatment planning parameters more often in error have been highlighted, providing practical caution for physicists commissioning treatment planning systems for Elekta linacs.

Purpose: Describe the Radiological Physics Center's (RPC) extensive standard dosimetry data set determined from on‐site audits measurements.Method and Materials: Measurements were made during on‐site audits to institutions participating in NCI funded cooperative clinical trials for 44 years using a 0.6cc cylindrical ionization chamber placed within the RPC's water tank. Measurements were made on Varian, Siemens, and Elekta/Philips accelerators for 11 different energies from 68 models of accelerators. We have measured percent depth dose, output factors, and off‐axis factors for 123 different accelerator model/energy combinations for which we have 5 or more sets of measurements. The RPC analyzed these data and determined the ‘standard data’ for each model/energy combination. The RPC defines ‘standard data’ as the mean value of 5 or more sets of dosimetry data or agreement with published depth dose data (within 2%). Results: The analysis of these standard data indicates that for modern accelerator models, the dosimetry data for a particular model/energy are within i,±2%. The RPC has always found accelerators of the same make/model/energy combination have the same dosimetric properties in terms of depth dose,field size dependence and off‐axis factors. Because of this consistency, the RPC can assign standard data for percent depth dose, average output factors and off‐axis factors for a given combination of energy and accelerator make and model.Conclusions: The RPC standard data can be used as a redundant quality assurance tool to assist Medical Physicists to have confidence in their clinical data to within 2%. The next step is for the RPC to provide a way for institutions to submit data to the RPC to determine if their data agrees with the standard data as a redundant check. This work was supported by PHS grants CA10953 awarded by NCI, DHHS.

Purpose: To describe the Radiological Physics Center's (RPC) methods to evaluate an institution's ability to meet protocol guidelines in order to decrease NCI clinical trial deviation rate. Methods: The RPC's dosimetry group utilizes 3 methods of assessing an institutions ability to meet the protocol treatment specifications. These methods involve a clinical and dosimetric review of a treatment plan submitted by the institution prior to the first patient being treated on a protocol. The three evaluation methods include use of site/treatment modality specific benchmark cases, evaluation of a previous patient treated in a similar fashion and a rapid review of the first patient placed on a trial prior to start of treatment. The dosimetric review consists of an independent dose recalculation using RPC measured data or RPC standard dosimetry data. The clinical review assesses the patient's DVHs and contouring of the tumor volume and critical structures, typically in conjunction with a radiation oncologist.Results: Over the past 5 years the RPC has performed these QA reviews for several of the clinical trial groups for several different disease sites and treatment modalities. We have reviewed 1366 treatment plans as a part of credentialing (97 gynecological, 223 prostate, 1046 breast) where 222 failed the first submission requiring the RPC to interact with the submitting institution to resolve the discrepancy. The review of the benchmarks has resulted in 18% of the institutions requiring intervention by the RPC. Performing these reviews has identified potential clinical and dosimetric problem areas that could possibly have resulted in 17% of the charts reviewed to receive a minor or major deviation. Conclusions: The RPC's clinical and dosimetry review of submitted treatment plans before or early in the treatment process has helped to reduce the deviation rates on protocols. Work supported by PHS grant CA 10953 awarded by NCI, DHHS

Purpose The NRG-BR001 trial is the first National Cancer Institute–sponsored trial to treat multiple (range 2-4) extracranial metastases with stereotactic body radiation therapy. Benchmark credentialing is required to ensure adherence to this complex protocol, in particular, for metastases in close proximity. The present report summarizes the dosimetric results and approval rates. Methods and Materials The benchmark used anonymized data from a patient with bilateral adrenal metastases, separated by Results Of 63 benchmarks submitted through October 2015, 94% were approved, with 51% approved at the first attempt. Most used volumetric arc therapy (VMAT) (78%), a single plan for both PTVs (90%), and prioritized the PTV over the stomach (75%). The median dose to 95% of the volume was 44.8 ± 1.0 Gy and 44.9 ± 1.0 Gy for the right and left PTV, respectively. The median dose to 0.03 cm 3 was 14.2 ± 2.2 Gy to the spinal cord and 46.5 ± 3.1 Gy to the stomach. Plans that spared the stomach significantly reduced the dose to the left PTV and stomach. Conformity metrics were significantly better for single plans that simultaneously treated both PTVs with VMAT, intensity modulated radiation therapy, or 3-dimensional conformal radiation therapy compared with separate plans. No significant differences existed in the dose at 2 cm from the PTVs. Conclusions Although most plans used VMAT, the range of conformity and dose falloff was large. The decision to prioritize either OARs or PTV coverage varied considerably, suggesting that the toxicity outcomes in the trial could be affected. Several benchmarks met the dose-volume histogram metrics but produced unacceptable plans owing to low conformity. Dissemination of a frequently-asked-questions document improved the approval rate at the first attempt. Benchmark credentialing was found to be a valuable tool for educating institutions about the protocol requirements.

Accurate data regarding linear accelerator (Linac) radiation characteristics are important for treatment planning system modeling as well as regular quality assurance of the machine. The Imaging and Radiation Oncology Core-Houston (IROC-H) has measured the dosimetric characteristics of numerous machines through their on-site dosimetry review protocols. Photon data are presented and can be used as a secondary check of acquired values, as a means to verify commissioning a new machine, or in preparation for an IROC-H site visit.Photon data from IROC-H on-site reviews from 2000 to 2014 were compiled and analyzed. Specifically, data from approximately 500 Varian machines were analyzed. Each dataset consisted of point measurements of several dosimetric parameters at various locations in a water phantom to assess the percentage depth dose, jaw output factors, multileaf collimator small field output factors, off-axis factors, and wedge factors. The data were analyzed by energy and parameter, with similarly performing machine models being assimilated into classes. Common statistical metrics are presented for each machine class. Measurement data were compared against other reference data where applicable.Distributions of the parameter data were shown to be robust and derive from a student's t distribution. Based on statistical and clinical criteria, all machine models were able to be classified into two or three classes for each energy, except for 6 MV for which there were eight classes. Quantitative analysis of the measurements for 6, 10, 15, and 18 MV photon beams is presented for each parameter; supplementary material has also been made available which contains further statistical information.IROC-H has collected numerous data on Varian Linacs and the results of photon measurements from the past 15 years are presented. The data can be used as a comparison check of a physicist's acquired values. Acquired values that are well outside the expected distribution should be verified by the physicist to identify whether the measurements are valid. Comparison of values to this reference data provides a redundant check to help prevent gross dosimetric treatment errors.

Purpose To compare radiation machine measurement data collected by the Imaging and Radiation Oncology Core at Houston (IROC-H) with institutional treatment planning system (TPS) values, to identify parameters with large differences in agreement; the findings will help institutions focus their efforts to improve the accuracy of their TPS models. Methods and Materials Between 2000 and 2014, IROC-H visited more than 250 institutions and conducted independent measurements of machine dosimetric data points, including percentage depth dose, output factors, off-axis factors, multileaf collimator small fields, and wedge data. We compared these data with the institutional TPS values for the same points by energy, class, and parameter to identify differences and similarities using criteria involving both the medians and standard deviations for Varian linear accelerators. Distributions of differences between machine measurements and institutional TPS values were generated for basic dosimetric parameters. Results On average, intensity modulated radiation therapy–style and stereotactic body radiation therapy–style output factors and upper physical wedge output factors were the most problematic. Percentage depth dose, jaw output factors, and enhanced dynamic wedge output factors agreed best between the IROC-H measurements and the TPS values. Although small differences were shown between 2 common TPS systems, neither was superior to the other. Parameter agreement was constant over time from 2000 to 2014. Conclusions Differences in basic dosimetric parameters between machine measurements and TPS values vary widely depending on the parameter, although agreement does not seem to vary by TPS and has not changed over time. Intensity modulated radiation therapy–style output factors, stereotactic body radiation therapy–style output factors, and upper physical wedge output factors had the largest disagreement and should be carefully modeled to ensure accuracy.

The task group (TG) for quality assurance for robotic radiosurgery was formed by the American Association of Physicists in Medicine's Science Council under the direction of the Radiation Therapy Committee and the Quality Assurance (QA) Subcommittee. The task group (TG-135) had three main charges: (1) To make recommendations on a code of practice for Robotic Radiosurgery QA; (2) To make recommendations on quality assurance and dosimetric verification techniques, especially in regard to real-time respiratory motion tracking software; (3) To make recommendations on issues which require further research and development. This report provides a general functional overview of the only clinically implemented robotic radiosurgery device, the CyberKnife. This report includes sections on device components and their individual component QA recommendations, followed by a section on the QA requirements for integrated systems. Examples of checklists for daily, monthly, annual, and upgrade QA are given as guidance for medical physicists. Areas in which QA procedures are still under development are discussed.

For commissioning a linear accelerator for clinical use, medical physicists are faced with many challenges including the need for precision, a variety of testing methods, data validation, the lack of standards, and time constraints. Since commissioning beam data are treated as a reference and ultimately used by treatment planning systems, it is vitally important that the collected data are of the highest quality to avoid dosimetric and patient treatment errors that may subsequently lead to a poor radiation outcome. Beam data commissioning should be performed with appropriate knowledge and proper tools and should be independent of the person collecting the data. To achieve this goal, Task Group 106 (TG-106) of the Therapy Physics Committee of the American Association of Physicists in Medicine was formed to review the practical aspects as well as the physics of linear accelerator commissioning. The report provides guidelines and recommendations on the proper selection of phantoms and detectors, setting up of a phantom for data acquisition (both scanning and no-scanning data), procedures for acquiring specific photon and electron beam parameters and methods to reduce measurement errors (

Introduction In 2014, the NRG Oncology Group initiated the first National Cancer Institute-sponsored, phase 1 clinical trial of stereotactic body radiation therapy (SBRT) for the treatment of multiple metastases in multiple organ sites (BR001; NCT02206334). The primary endpoint is to test the safety of SBRT for the treatment of 2 to 4 multiple lesions in several anatomic sites in a multi-institutional setting. Because of the technical challenges inherent to treating multiple lesions as their spatial separation decreases, we present the technical requirements for NRG-BR001 and the rationale for their selection. Methods and materials Patients with controlled primary tumors of breast, non-small cell lung, or prostate are eligible if they have 2 to 4 metastases distributed among 7 extracranial anatomic locations throughout the body. Prescription and organ-at-risk doses were determined by expert consensus. Credentialing requirements include (1) irradiation of the Imaging and Radiation Oncology Core phantom with SBRT, (2) submitting image guided radiation therapy case studies, and (3) planning the benchmark. Guidelines for navigating challenging planning cases including assessing composite dose are discussed. Results Dosimetric planning to multiple lesions receiving differing doses (45-50 Gy) and fractionation (3-5) while irradiating the same organs at risk is discussed, particularly for metastases in close proximity (≤5 cm). The benchmark case was selected to demonstrate the planning tradeoffs required to satisfy protocol requirements for 2 nearby lesions. Examples of passing benchmark plans exhibited a large variability in plan conformity. Discussion NRG-BR001 was developed using expert consensus on multiple issues from the dose fractionation regimen to the minimum image guided radiation therapy guidelines. Credentialing was tied to the task rather than the anatomic site to reduce its burden. Every effort was made to include a variety of delivery methods to reflect current SBRT technology. Although some simplifications were adopted, the successful completion of this trial will inform future designs of both national and institutional trials and would allow immediate clinical adoption of SBRT trials for oligometastases.

Purpose To present issues to be considered in, and make proposals for, image-based brachytherapy for cervical cancer. Methods and materials The Image-Guided Brachytherapy Working Group, consisting of representatives from the Gynecology Oncology Group (GOG), Radiologic Physics Center (RPC), American Brachytherapy Society (ABS), American College of Radiology (ACR), American College of Radiology Imaging Network (ACRIN), American Association of Physicists in Medicine (AAPM), Radiation Therapy Oncology Group (RTOG), and American Society for Therapeutic Radiology and Oncology (ASTRO), proposed guidelines for image-based brachytherapy for cervical cancer. This report was based on their aggregate clinical experience and a review of the literature. It reflects only the personal opinions of the authors and is not meant to be an endorsement from any of the above organizations. Results The Group recommended T 2 -weighted MRI using a pelvic surface coil with MRI-compatible brachytherapy applicators in place for image-based intracavitary brachytherapy for cervical cancer. Imaging must be performed with the patient in the treatment position, with all other treatment conditions duplicated as closely as possible. Future use of positron emission tomography or positron emission tomography/CT may obviate the need for special applicators. The group proposed the following terminology for image-based brachytherapy. The GTV (I) is defined as the gross tumor volume as defined through imaging, GTV is defined as the GTV (I) plus any clinically visualized or palpable tumor extensions, and GTV + cx is defined as the GTV plus the entire cervix. The dose–volume histograms (DVH) of the GTV, GTV (I) , GTV + cx should be performed, and the dose to 100%, 95%, or 90% of the GTV (D 100 , D 95 , and D 90 , respectively) and the percentage of the GTV covered by Point A dose (V 100 ) should be reported. Similarly, the DVH of the bladder and rectum wall should be performed, and the maximal dose at any point within the bladder and rectal wall should be reported, along with the maximal dose to a contiguous 1, 2, and 5 cm 3 volume of the bladder and rectum, respectively. In addition, the dose at the International Commission on Radiation Units and Measurements reference point for the bladder and rectum should be reported. The Group thought that the current dose prescription method in use for cervical cancer brachytherapy (i.e., to prescribe to Point A in most institutions) should not be changed as yet, because image-based dosimetry is not ready for routine practice. The Group proposes that for research purposes, individual centers and cooperative groups (e.g., GOG, RTOG, ACRIN) collect image-based dosimetry information and perform DVHs and correlate these data with the clinical outcome to determine which of the above parameters are relevant. The Group encourages external funding for image-based dosimetry and recommends that brachytherapy manufacturers develop image-compatible applicators. Conclusion Although current institutional brachytherapy prescription for cervical cancer should continue, image-based data collection and analysis are needed to optimize cervical cancer brachytherapy. Proposals are made for research in image-based brachytherapy for cervical cancer.

A new calibration protocol, developed by the AAPM Task Group 51 (TG‐51) to replace the TG‐21 protocol, is based on an absorbed‐dose to water standard and calibration factor (ND,w), while the TG‐21 protocol is based on an exposure (or air‐kerma) standard and calibration factor (Nx). Because of differences between these standards and the two protocols, the results of clinical reference dosimetry based on TG‐51 may be somewhat different from those based on TG‐21. The Radiological Physics Center has conducted a systematic comparison between the two protocols, in which photon and electron beam outputs following both protocols were compared under identical conditions. Cylindrical chambers used in this study were selected from the list given in the TG‐51 report, covering the majority of current manufacturers. Measured ratios between absorbed‐dose and air‐kerma calibration factors, derived from the standards traceable to the NIST, were compared with calculated values using the TG‐21 protocol. The comparison suggests that there is roughly a 1% discrepancy between measured and calculated ratios. This discrepancy may provide a reasonable measure of possible changes between the absorbed‐dose to water determined by TG‐51 and that determined by TG‐21 for photon beam calibrations. The typical change in a 6 MV photon beam calibration following the implementation of the TG‐51 protocol was about 1%, regardless of the chamber used, and the change was somewhat smaller for an 18 MV photon beam. On the other hand, the results for 9 and 16 MeV electron beams show larger changes up to 2%, perhaps because of the updated electron stopping power data used for the TG‐51 protocol, in addition to the inherent 1% discrepancy presented in the calibration factors. The results also indicate that the changes may be dependent on the electron energy. PACS number(s): 87.66.–a, 87.53.–j

Purpose: Dosimetric errors in radiotherapy dose delivery lead to suboptimal treatments and outcomes. This work reviews the frequency and severity of dosimetric and programmatic errors identified by on-site audits performed by the IROC Houston QA center. Methods: IROC Houston on-site audits evaluate absolute beam calibration, relative dosimetry data compared to the treatment planning system data, and processes such as machine QA. Audits conducted from 2000-present were abstracted for recommendations, including type of recommendation and magnitude of error when applicable. Dosimetric recommendations corresponded to absolute dose errors >3% and relative dosimetry errors >2%. On-site audits of 1020 accelerators at 409 institutions were reviewed. Results: A total of 1280 recommendations were made (average 3.1/institution). The most common recommendation was for inadequate QA procedures per TG-40 and/or TG-142 (82% of institutions) with the most commonly noted deficiency being x-ray and electron off-axis constancy versus gantry angle. Dosimetrically, the most common errors in relative dosimetry were in small-field output factors (59% of institutions), wedge factors (33% of institutions), off-axis factors (21% of institutions), and photon PDD (18% of institutions). Errors in calibration were also problematic: 20% of institutions had an error in electron beam calibration, 8% had an error in photon beam calibration, and 7% had an error in brachytherapy source calibration. Almost all types of data reviewed included errors up to 7% although 20 institutions had errors in excess of 10%, and 5 had errors in excess of 20%. The frequency of electron calibration errors decreased significantly with time, but all other errors show non-significant changes. Conclusion: There are many common and often serious errors made during the establishment and maintenance of a radiotherapy program that can be identified through independent peer review. Physicists should be cautious, particularly in areas highlighted herein that show a tendency for errors.

Purpose: To analyze the uncertainty of the TG-51 electron beam calibration correction factors for farmer type ion chambers currently used by institutions visited by IROC Houston. Methods: TG-51 calibration data were collected from 181 institutions visited by IROC Houston physicists for 1174 and 197 distinct electron beams from modern Varian and Elekta accelerators, respectively. Data collected and analyzed included ion chamber make and model, nominal energy, ND,w, I5₀, R5₀, k’R5₀, dref, Pgr and pdd(dref). k’R5₀ data for parallel plate chambers were excluded from the analysis. Results: Unlike photon beams, electron nominal energy is a poor indicator of the actual energy as evidenced by the range of R5₀ values for each electron beam energy (6–22MeV). The large range in R5₀ values resulted k’R5₀ values with a small standard deviation but large range between maximum value used and minimum value (0.001–0.029) used for a specific Varian nominal energy. Varian data showed more variability in k’R5₀ values than the Elekta data (0.001–0.014). Using the observed range of R5₀ values, the maximum spread in k’R5₀ values was determined by IROC Houston and compared to the spread of k’R5₀ values used in the community. For Elekta linacs the spreads were equivalent, but for Varian energies of 6 to 16MeV, the community spread was 2 to 6 times larger. Community Pgr values had a much larger range of values for 6 and 9 MeV values than predicted. The range in Varian pdd(dref ) used by the community for low energies was large, (1.4–4.9 percent), when it should have been very close to unity. Exradin, PTW Roos and PTW farmer chambers ND,w values showed the largest spread, ≥11 percent. Conclusion: While the vast majority of electron beam calibration correction factors used are accurate, there is a surprising spread in some of the values used.

Purpose: To determine the impact benchmarks and pre-treatment reviews have on improving the quality of submitted clinical trial data. Methods: Benchmarks are used to evaluate a site’s ability to develop a treatment that meets a specific protocol’s treatment guidelines prior to placing their first patient on the protocol. A pre-treatment review is an actual patient placed on the protocol in which the dosimetry and contour volumes are evaluated to be per protocol guidelines prior to allowing the beginning of the treatment. A key component of these QA mechanisms is that sites are provided timely feedback to educate them on how to plan per the protocol and prevent protocol deviations on patients accrued to a protocol. For both benchmarks and pre-treatment reviews a dose volume analysis (DVA) was performed using MIM softwareTM. For pre-treatment reviews a volume contour evaluation was also performed. Results: IROC Houston performed a QA effectiveness analysis of a protocol which required both benchmarks and pre-treatment reviews. In 70 percent of the patient cases submitted, the benchmark played an effective role in assuring that the pre-treatment review of the cases met protocol requirements. The 35 percent of sites failing the benchmark subsequently modified there planning technique to pass the benchmark before being allowed to submit a patient for pre-treatment review. However, in 30 percent of the submitted cases the pre-treatment review failed where the majority (71 percent) failed the DVA. 20 percent of sites submitting patients failed to correct their dose volume discrepancies indicated by the benchmark case. Conclusion: Benchmark cases and pre-treatment reviews can be an effective QA tool to educate sites on protocol guidelines and to minimize deviations. Without the benchmark cases it is possible that 65 percent of the cases undergoing a pre-treatment review would have failed to meet the protocols requirements.Support: U24-CA-180803

Purpose: The working group on the review and extension of the TG-51 protocol (WGTG51) collected data from American Association of Physicists in Medicine (AAPM) members with respect to their current TG-51 and associated addendum usage in the interest of considering future protocol addenda and guidance on reference dosimetry best practices. This study reports an overview of this survey on dosimetry of external beams. Methods: Fourteen survey questions were developed by WGTG51 and released in November 2015. The questions collected information on reference dosimetry, beam quality specification, and ancillary calibration equipment. Results: Of the 190 submissions completed worldwide (U.S. 70%), 83% were AAPM members. Of the respondents, 33.5% implemented the TG-51 addendum, with the maximum calibration difference for any photon beam, with respect to the original TG-51 protocol, being

Purpose: To make Image Guided Radiation Therapy (IGRT) credentialing a more unified, consistent and efficient process across the entire National Clinical Trial Network (NCTN). Methods: IGRT plays a role in several advanced NCTN trials. Previously an institution had to be IGRT credentialed for each protocol. When institutions were allowed to use previous credentials for new protocols it was limited to the same disease site as the original credentialing. The credentialing was analyzed by the physics PI of the protocol. We consulted with several of these physicists to determine what is important to consider when reviewing submissions and to learn ways to apply credentialing more broadly. Results: For trials open in 2016, IGRT credentialing can be simplified to cover either boney anatomy or soft tissue. This revised credentialing will cover all disease sites based on the type of anatomy, unless otherwise stated within the protocol. Institutions will submit will complete an online questionnaire about their IGRT procedures. Boney anatomy requirements will include submission of data from 2 sequential fraction of both a patient aligned with boney anatomy and pelvic patient. Soft tissue will require similar submissions for a patient aligned using soft tissue and a pelvic patient. Institutions will only be required to submit the pelvic patient once. Data should be in DICOM format and includes planning CT set, RT structure set, RT plan file, RT dose file, localization images and spatial registration file (if available). Reviews will be done by IROC-Houston staff who will continue to provide feedback to the sites. Conclusion: This revised IGRT credentialing process will bring consistency, a savings in time and effort for both the IROC Houston QA office and to those institutions wanting to be credentialed to participate in NCTN Trials. Sponsored by NIH/NCI CA10953

Purpose: IROC_H conducts external audits for output check verification of photon and electron beams. Many of these beams can meet the geometric requirements of the TG 51 calibration protocol. For those photon beams that are non TG 51 compliant like Elekta GammaKnife, Accuray CyberKnife and TomoTherapy, IROC_H has specific audit tools to monitor the reference calibration. Methods: IROC_H used its TLD and OSLD remote monitoring systems to verify the output of machines with TG 51 non compliant beams. Acrylic OSLD miniphantoms are used for the CyberKnife. Special TLD phantoms are used for TomoTherapy and GammaKnife machines to accommodate the specific geometry of each machine. These remote audit tools are sent to institutions to be irradiated and returned to IROC_H for analysis. Results: The average IROC_H/institution ratios for 480 GammaKnife, 660 CyberKnife and 907 rotational TomoTherapy beams are 1.000±0.021, 1.008±0.019, 0.974±0.023, respectively. In the particular case of TomoTherapy, the overall ratio is 0.977±0.022 for HD units. The standard deviations of all results are consistent with values determined for TG 51 compliant photon beams. These ratios have shown some changes compared to values presented in 2008. The GammaKnife results were corrected by an experimentally determined scatter factor of 1.025 in 2013. The TomoTherapy helical beam results are now from a rotational beam whereas in 2008 the results were from a static beam. The decision to change modality was based on recommendations from the users. Conclusion: External audits of beam outputs is a valuable tool to confirm the calibrations of photon beams regardless of whether the machine is TG 51 or TG 51 non compliant. The difference found for TomoTherapy units is under investigation. This investigation was supported by IROC grant CA180803 awarded by the NCI

Purpose: For each of this trials 3 treatment scenarios an institution must be credentialed. The purpose of credentialing is to verify all personnel involved with treatment planning have read the protocol and can follow the protocol specifications prior to placing a patient on protocol with the end result of limiting the number of protocol deviations. Credentialing also provides feedback to an institution prior to treatment of a patient on trial to correct any mistakes that may occur. Methods: An institution needs to update their Facility Questionnaire and download the 3 CT benchmark cases representing the 3 treatment groups (1A, 2A and 2B) of the study from the RPCs website. The institution may decide which modality (3DCRT/IMRT) to use for each benchmark, however at least one benchmark must be completed for each modality for which the institution wants to be credentialed. The RPC reviews these benchmarks using MIM for verification that dose requirements are per protocol. Results: Presently, 101 institutions have initiated the credentialing process. 94 institutions have submitted their benchmarks, 7% failed and never resubmitted a benchmark for re-review. The breakdown of credentialed techniques is; 4% IMRT only, 52% 3DCRT only and 44% 3DCRT/IMRT. Of those sites that have been credentialed: 6% of the institutions failed the benchmark for 1A, 11% failed for 2B and 40% failed for 2A at least once, before being credentialed. 9% of the institutions failed 2A twice and 1 institution failed three times. Conclusion: Currently 87 institutions have been credentialed for this study. The protocol has accrued 9 patients which have all been pre-treatment reviews where 2 of them had to be re-submitted for a re-review due to volume contouring. This work was supported by PHS grant CA 10953 awarded by NCI, DHHS.

Purpose: In recent years the need for small field data of MLCs has increased due to the use of intensity-modulated radiation (IMRT), but moreover the use of stereotactic body radiation (SBRT) has increased, which uses not simply small field sizes, but small jaw and field sizes together. Having reference data for these small fields that is reliable would be invaluable to the physics community. Our study has gathered these values and the data distributions from the Radiological Physics Center's (RPC) site visits between 1990 and the present. Methods: For all measurements, the RPC used a 25 × 25 × 25cm water phantom placed at 100cm SSD. All measurements were made with an Exradin A16 cylindrical ion chamber at an effective depth of 10 cm. A total of 42 Varian machine measurements were used to compose the data for a 6 MV beam and 5 TrueBeam 6 MV flattening filter free (FFF) beams were used for FFF data. Results: Jaw/MLC fields were measured for both 6 MV and 6 MF FFF beams with the jaws and MLCs both at the following field sizes: 6×6, 4×4, 3×3, and 2×2cm. Measurements were normalized to the 10×10 field readings (defined by the jaws and MLC). Spread in the data was minimal and demonstrates a high level of accuracy of acquired data. Conclusion: Small field Jaw/MLC reference data for Varian 6MV and 6 MV FFF beams has been analyzed and presented here, composed of the aggregation of numerous RPC site visits. Obtaining reliable small field data remains difficult, however the RPC has collected high fidelity small field Jaw/MLC data. The data are presented as a reference along with their distributions, in such a way that the physicist can act based upon their own desired agreement with the reference data.

The Radiological Physics Center (RPC) has functioned continuously for 38 years to assure the National Cancer Institute and the cooperative groups that institutions participating in multi-institutional trials can be expected to deliver radiation treatments that are clinically comparable to those delivered by other institutions in the cooperative groups. To accomplish this, the RPC monitors the machine output, the dosimetry data used by the institutions, the calculation algorithms used for treatment planning, and the institutions' quality control procedures. The methods of monitoring include on-site dosimetry review by an RPC physicist and a variety of remote audit tools. The introduction of advanced technology clinical trials has prompted several study groups to require participating institutions and personnel to become credentialed, to ensure their familiarity and capability with techniques such as three-dimensional conformal radiotherapy, intensity-modulated radiotherapy, stereotactic body radiotherapy, and brachytherapy. The RPC conducts a variety of credentialing activities, beginning with questionnaires to evaluate an institution's understanding of the protocol and their capabilities. Treatment-planning benchmarks are used to allow the institution to demonstrate their planning ability and to facilitate a review of the accuracy of treatment-planning systems under relevant conditions. The RPC also provides mailable anthropomorphic phantoms to verify tumor dose delivery for special treatment techniques. While conducting these reviews, the RPC has amassed a large amount of data describing the dosimetry at participating institutions. Representative data from the monitoring programs are discussed, and examples are presented of specific instances in which the RPC contributed to the discovery and resolution of dosimetry errors.

Purpose: To describe a new infrastructure and process that will enable end-users to commission model-based dose calculation (MBDC) software for brachytherapy planning, and to invite end-users to participate in the beta testing phase of this process. Methods: The AAPM working groups on model-based dose calculation algorithms in brachytherapy (WGDCAB) and brachytherapy source registry (WGBSR) collaboratively implemented the basic MBDC software commissioning workflow described in the AAPM+ESTRO TG-186 report. For a small number of initial test cases virtual CT image, anatomical structure set, treatment plan, and associated 3D dose data for a single dwell position occupied by a WGDCAB generic high-dose-rate Ir-192 virtual source, with or without a generic shielded applicator, were generated. Dose distributions were calculated using Monte Carlo (MC) code MCNP6, Elekta’s Advanced Collapsed cone Algorithm (ACE™), and Varian’s Acuros™ BV module. All data were saved in DICOM RT format and uploaded to a provisional, web-accessible repository in the joint AAPM—IROC Houston brachytherapy source registry. It is envisioned that end-users will download data for a test case from the repository, verify its correctness, calculate 3D dose locally, and then compare with MCNP6 and MBDC doses obtained from the repository using TPS-based comparison tools. User guides in preparation for each TPS will facilitate the process. Results: Initial evaluations of DICOM data download, TPS import, MBDC dose calculation, and reference dose comparison indicate that the infrastructure and process described above are both viable and practicable. Ancillary data including generic source and shielded applicator specifications, CAD drawings, and MC code definitions are also available in the repository. Conclusion: With further refinement and beta-test input from end-users, a practical MBDC software commissioning process for brachytherapy can be established. A procedure for adding new test cases submitted by end-users to the repository will be put in place by WGDCAB.

Purpose: To highlight the IROC Houston on-site dosimetry audit program, and to investigate the impact of clinical conditions on the frequency of errors/recommendations noted by IROC Houston. Methods: The results of IROC Houston on-site audits from 2000-present were abstracted and compared to clinical parameters, this included 409 institutions and 1020 linacs. In particular, we investigated the frequency of recommendations versus year, and the impact of repeat visits on the number of recommendations. We also investigated the impact on the number of recommendations of several clinical parameters: the number and age of the linacs, the linac/TPS combination, and the scope of the QA program. Results: The number of recommendations per institution (3.1 average) has shown decline between 2000 and present, although the number of recommendations per machine (0.89) has not changed. Previous IROC Houston site visits did not Result in fewer recommendations on a repeat visit, but IROC Houston tests have changed substantially during the last 15 years as radiotherapy technology has changed. There was no impact on the number of recommendations based on the number of machines at the institution or the age of a given machine. The fewest recommendations were observed for Varian-Eclipse combinations (0.71 recs/machine), while Elekta- Pinnacle combinations yielded the most (1.62 recs/machine). Finally, in the TG-142 era (post-2010), those institutions that had a QA recommendation (n=77) had significantly more other recommendations (1.83 per institution) than those that had no QA rec (n=12, 1.33 per institution). Conclusion: Establishing and maintaining a successful radiotherapy program is challenging and areas of improvement can routinely be identified. Clinical conditions such as linac-TPS combinations and the establishment of a good QA program impact the frequency of errors/deficiencies identified by IROC Houston during their on-site review process.

Purpose: To compare the CT Number (CTN) to Relative Linear Stopping Power (RLSP) conversion curves used by 14 proton institutions in their dose calculations. Methods: The proton institution’s CTN to RLSP conversion curves were collected by the Imaging and Radiation Oncology Core (IROC) Houston QA Center during its on-site dosimetry review audits. The CTN values were converted to scaled CT Numbers. The scaling assigns a CTN of 0 to air and 1000 to water to allow intercomparison. The conversion curves were compared and the mean curve was calculated based on institutions’ predicted RLSP values for air (CTN 0), lung (CTN 250), fat (CTN 950), water (1000), liver (CTN 1050), and bone (CTN 2000) points. Results: One institution’s curve was found to have a unique curve shape between the scaled CTN of 1025 to 1225. This institution modified its curve based on the findings. Another institution had higher RLSP values than expected for both low and high CTNs. This institution recalibrated their two CT scanners and the new data placed their curve closer to the mean of all institutions. After corrections were made to several conversion curves, four institutions still fall outside 2 standard deviations at very low CTNs (100–200), and two institutions fall outside between CTN 850–900. The largest percent difference in RLSP values between institutions for the specific tissues reviewed was 22% for the lung point. Conclusion: The review and comparison of CTN to RLSP conversion curves allows IROC Houston to identify any outliers and make recommendations for improvement. Several institutions improved their clinical dose calculation accuracy as a Result of this review. There is still area for improvement, particularly in the lung area of the curve. The IROC Houston QA Center is supported by NCI grant CA180803.

Purpose: To describe the extent of IROC Houston’s (formerly the RPC) QA activities and audit results for radiotherapy institutions outside of North America (NA). Methods: The IROC Houston’s QA program components were designed to audit the radiation dose calculation chain from the NIST traceable reference beam calibration, to inclusion of dosimetry parameters used to calculate tumor doses, to the delivery of the radiation dose. The QA program provided to international institutions includes: 1) remote TLD/OSLD audit of machine output, 2) credentialing for advanced technologies, and 3) review of patient treatment records. IROC Houston uses the same standards and acceptance criteria for all of its audits whether for North American or international sites. Results: IROC Houston’s QA program has reached out to radiotherapy sites in 43 different countries since 2013 through their participation in clinical trials. In the past two years, 2,778 international megavoltage beam outputs were audited with OSLD/TLD. While the average IROC/Inst ratio is near unity for all sites monitored, there are international regions whose results are significantly different from the NA region. In the past 2 years, 477 and 87 IMRT H&N phantoms were irradiated at NA and international sites, respectively. Regardless of the OSLD beam audit results, the overall pass rate (87 percent) for all international sites (no region separation) is equal to the NA sites. Of the 182 international patient charts reviewed, 10.7 percent of the dose calculation points did not meet our acceptance criterion as compared to 13.6 percent for NA sites. The lower pass rate for NA sites results from a much larger brachytherapy component which has been shown to be more error prone. Conclusion: IROC Houston has expanded its QA services worldwide and continues a long history of improving radiotherapy dose delivery in many countries. Funding received for QA audit services from the Korean GOG, DAHANCA, EORTC, ICON and CMIC Group

Traditionally the Radiological Physics Center (RPC) quality assurance audits of institutions have been performed by a qualified RPC physicist on-site, and by a mailed TLD program that monitors machine output calibrations. In 1997, the RPC implemented a comprehensive off-site evaluation of institution dosimetry data and patient dose calculations. A preliminary analysis and comparison of the off-site evaluation for seventeen institutions with the results of their respective RPC on-site review is presented. The comparison shows that a detailed off-site evaluation of the calibration protocol parameters is not effective in identifying calibration dosimetry problems. In general, the off-site evaluation failed to identify percent-depth-dose (PDD) and output factor discrepancies found at the institution during on-site reviews. However, PDD discrepancies found at one institution by the off-site evaluation correctly predicted the on-site findings. The most frequently identified dosimetry problems came from the evaluation of wedge factors and off-axis factors. The off-site evaluation of patient dose calculations shows discrepancies that are significant, but not confirmed by the on-site visit. Our findings indicate that for the off-site dosimetry review to be more successful in predicting potential problems, the RPC needs to continue to refine its "standard" dosimetry data. The comparison of the results of the two reviews has allowed the RPC to evaluate the effectiveness of the remote review, to identify areas where it is more effective and how this remote evaluation program can be revised and improved.

The AAPM Task Group 51 (TG-51) recently published its protocol for clinical reference dosimetry of megavoltage radiation therapy. Explicit application of TG-51 to a high energy accelerator with electron capability requires the clinical physicist to have a 1 mm thick sheet of lead and a parallel plate chamber. Many clinical physicists have neither, therefore the authors have studied the impact of alternative measurement techniques on output calibration to solve this problem. Depth dose measurements with a lead sheet in the beam are required to determine the beam quality (kQ) by obtaining the %dd(10)/sub x/ (depth dose with electron contamination removed) for energies /spl ges/10 MV, TG-51 also states that a parallel plate chamber is recommended for electron calibration and is required for reference dosimetry for electron energies /spl les/6 MeV. To determine if these requirements are necessary, the Radiological Physics Center (RPC) made measurements on Varlan, GE, and Siemens units for 10 and 18 MV photons and 5-20 MeV electrons. The comparison of lead versus no lead revealed that the k/sub Q/ value, thus the calibration of the beam, will vary by no more than 0.2%. The comparison between a parallel plate and a cylindrical Farmer chamber showed no measurable difference in the calibration across the range of electron energies. Omission of the lead to determine k/sub Q/ and use of a cylindrical chamber for low electron energies have an insignificant effect on the calibration.

History: TG‐135 was approved by AAPM at the 2006 Annual Meeting. The intent of this TG was to fill the gap between TG‐40, which does not cover certain QA aspects of newer radiation delivery devices, and TG‐100, which will revise our current QA paradigm. General Outline of Report: The report consists of three major sections: (1) QA for individual system components, (2) QA for the integrated systems, (3) a summary with QA checklists. At the time of publication there is only one FDA‐approved roboticradiosurgery system (Cyberknife, Accuray Inc, Sunnyvale, CA) on the market, therefore the report is often vendor‐specific. Technologies which became available in the clinic after the report was submitted for review (e.g. IRIS collimator, XSight lung tracking) were not included. Major Highlights: Each individual Cyberknife component will be discussed, with reference to applicable AAPM reports and additional QA recommendations if necessary. We also highlight areas in which a good QA approach has not yet been developed. Those include the QA of the imager systems, but also periodic QA of individual beam pointing accuracy. The second section, QA for integrated systems, explains how the various subsystems interact, and how to design a QA program for the feedback loops. Similar to the individual component QA, there are areas in the integrated systems QA where more work needs to be done. This includes e.g. QA of the interaction between image quality and tracking algorithm accuracy, and individual beam pointing QA for non‐isocentric plans. The Task Group's recommendations on patient‐like and individual patient QA are also included. The report summarizes daily, monthly, annual and special considerations (software and hardware upgrades, earthquakes, etc). Report as it relates to TG‐100: This report is intended to give QA recommendations based on the philosophy of TG‐40. The QM approach to roboticradiosurgery will have to be adapted to the TG‐100 philosophy after its publication, which includes the data collection for a FMEA analysis for this relatively new technology. Implementation Plan: The recommendations of TG‐135 should be critically evaluated by the site physicist after the report is published. Changes to the existing QA program should be made at the next scheduled incidence (i.e. changes for the annual QA at the next annual QA). Roboticradiosurgery is a fast‐evolving field, therefore keeping informed through reading peer‐reviewed literature and attending CE programs on QA is essential. Timeline for Report Release: TG 135 will be published in the May 2011 edition of Medical Physics. Learning Objectives: 1. Be aware of the estimated publication date for the report, report structure, and implementation plan. 2. Understand the difference between individual component QA and integrated systems QA. 3. Know which areas of roboticradiosurgery QA are still under development. 4. Anticipate the future change of QA philosophy for roboticradiosurgery with TG‐100.

Purpose: Accurate data of linear accelerator radiation characteristics is important for treatment planning system commissioning as well as regular quality assurance of the machine. The RPC has performed site visits of numerous machines . Data gathered from Varian machines from the past 15 years are presented. The data collected can be used as a secondary check or when commissioning a new machine to verify that values are reasonable. Methods: Data from the past 15 years of RPC site visits was compiled and analyzed. Data was composed from measurements from approximately 400 Varian machines. Each dataset consists of several point measurements at various locations in a water phantom to measure percentage depth dose, output factors, including small MLC fields, off-axis factors, and wedge factors if applicable. Common statistical values are presented for each machine type. Where applicable, data was compared to other reference data given by the vendor or a select number of previous researchers. Results: Data is separated by energy and parameter and then analyzed by machine class. Data distributions of the parameter data were normal except occasionally at the tails. Distributions of the data for each class and parameter are tabulated to give not simply a singular reference value, but metrics about the distribution: 5th and 95th percentile values and the standard deviation as well as the median. Conclusion: The RPC has collected numerous data on Varian linacs and presented the finding of the past 15 years. The data can be used as a reference data set for physicists to compare against. A linac that deviates from the values does not necessarily indicate there is a problem as long as the treatment planning system correlates to the machine. Comparison of linac and treatment planning system data to external reference data can prevent serious treatment errors.

Purpose: To describe the commissioning of Aluminum Oxide Optically Stimulated Luminescent Dosimeters (OSLD) for the use in Carbon beam remote dosimetry for centers participating in NCI-funded cooperative group clinical trials. Methods: As Carbon therapy centers express interest in participating in cooperative group clinical trials, the Imaging and Radiation Oncology Core Group (IROC) Houston QA Center (formerly RPC) is developing a way to remotely monitor the machine output of these Carbon facilities. OSLD have been commissioned for photon, electron and proton dosimetry, so an experiment was designed to commission the same dosimeters for Carbon. OSLD were irradiated in a Carbon therapy beam produced by the Siemens synchrotron at the Heidelberg Ion Therapy facility in Heidelberg, Germany. The OSLD were placed in acrylic phantoms, imaged with a CT scanner, and plans were developed using the Siemens treatment planning system. The OSLD were irradiated in uniform fields with maximum energies of 216, 301, and 402 MeV and at dose levels of 50, 100, 200 and 300 cGy. Results: The response of the OSLD in the Carbon beam, as compared to the Cobalt-60 reference condition, required an energy correction of 1.85 to account for the particle correction. OSLD dose calculations typically have a linearity correction to account for the change in response relative to the change in dose delivered. However, the response of the OSLD in the Carbon beam was found to be independent of the dose level; thus the linearity correction is 1.00. Conclusion: IROC Houston has commissioned OSLD for the use of remote output checks for Carbon therapy facilities to help ensure consistency across clinical trial participants. Work supported by grant CA10953 (NCI, DHHS).

Purpose: The RPC, established in 1968 has contributed to the development, conduct, and QA of NCI funded multi-institutional cooperative group clinical trials and institutions, primarily in the USA/Canada and 242 other countries, participating in trials. Methods: The RPC QA program components were designed to audit the radiation dose calculation chain from the NIST traceable reference beam calibration, to inclusion of dosimetry parameters used to calculate tumor doses, to the delivery of the radiation dose. The QA program included: 1) remote TLD/OSLD audit of machine output, 2) on-site dosimetry review visits, 3) credentialing for advanced technologies, and 4) review of patient treatment records. The RPC presented and published their findings to the radiation oncology community. Results: The number of institutions monitored by the RPC increased from around 1200 in the late 90s, to ∼2000 in 2013. There were over 4000 megavoltage therapy machines and ∼28,000 therapy beams in the 1991 institutions monitored by the RPC by the end of 2013. Within the 14,000 photon, electron and proton beam outputs remotely monitored with TLD/OSLD annually, between 10-20% of the institutions have one or more beams outside the RPC 5% criterion. Dosimetry site visits to photon and proton centers continue to result in 2-4 recommendations affecting key dosimetry parameters that impact patient treatment times. One in four patient treatment records reviewed by the RPC have their dose data corrected by >5% before trial groups use them for outcomes analysis. Twelve of fourteen clinically active proton centers are approved to participate in NCI funded clinical trials. The RPC published 222 peer reviewed articles since 1972. Conclusion: Findings from the RPC suggest that human errors continue to play a role in radiotherapy discrepancies and without the RPC independent QA program, the number of undetected errors and time elapsed before their discovery would have been greater. Work supported by MGH C06 CA059267 and grants CA10953, CA081647 awarded by NCI, DHHS.

Purpose: NSABP B‐39 / RTOG 0413 is a Phase III trial comparing Whole Breast Irradiation versus Partial Breast Irradiation (PBI). The partial breast arm consists of 3 techniques, 3D Conformal Radiation Therapy, MammoSite and multi‐catheter HDR. For each of these techniques an institution, radiation oncologist and physicist “team” must be credentialed. Credentialing requires completing knowledge assessment and facility questionnaires, importing a DICOM CTimage set, performing a treatment plan using the image set and exporting the images, structures and isodoses to the Image‐Guided Therapy QA Center (ITC). Method & Materials: An institution can obtain the Knowledge Assessment and Facility Questionnaires from the RPC's website (http://rpc.mdanderson.org). These questionnaires can be completed online, emailed, faxed or mailed directly to the RPC. An institution may be credentialed for one or more of the PBI techniques. A CT benchmark case exists for each PBI technique. The institution is required to import the appropriate CTimage set into their treatment planning system. The benchmark must be planned per protocol. The benchmark must then be digitally exported to the ITC along with all required hard copy data. The RPC will review each benchmark case submitted. Once the RPC has completed its review NSABP will be informed that the institution has met the requirements for credentialing and will be allowed to enter patients onto the protocol. Conclusion: The purpose of credentialing is to verify that the radiation oncologist and other personnel involved are familiar with the protocol and can plan a case per protocol prior to placing a patient on protocol. This process enables us to give a “team” feedback prior to treating a patient on the trial potentially enabling us to reduce the number of deviations incurred on the trial. This work was supported by PHS grant CA 10953 awarded by NCI, DHHS.

Purpose: The Radiological Physics Center (RPC) performs rapid reviews for several different study groups and for a variety of disease sites including colon, breast, endometrial and cervix. Rapid Reviews have been performed for high dose rate brachytherapy studies, 3D CRT and IMRT studies. The purpose of rapid reviews is to verify that the radiation oncologist is capable of treating a patient per protocol prior to treatment commencing with the goal of reducing the number of deviations. Methods: The rapid review process requires that the institution electronically submit the protocol patient treatment plan prior to the commencement of treatment for a dosimetric and clinical review. Dependent on the protocol, the first patient or every patient submitted by a physician might require a rapid review. Rapid reviews enable the RPC to provide feedback to the physician to rectify errors prior to the start of treatment. Deviations are assessed according to defined criteria within the specific protocolResults: For three protocols, where rapid reviews were required for the first patient placed on protocol, 24%, 48% and 53% required a revision and resubmission for a re‐review due to a significant protocol deviation. For one protocol, where rapid reviews were required for all patients, 81% of the submitted patient cases required a revision and resubmission for a re‐review. Radiation Oncologists who completed the rapid review process received no major deviations on subsequent patient's placed on protocol. Conclusion: Rapid reviews serve the purpose of reducing the number of protocol deviations by providing feedback to Radiation Oncologists on how to better comply with the requirements of the protocol prior to commencing treatment of a patient on the study.This work was supported by PHS grants CA10953 and CA081647 awarded by NCI, DHHS. This work was supported by PHS grants CA10953 and CA081647 awarded by NCI, DHHS.

Purpose: To analyze the findings of the Radiological Physics Center's (RPC) QA audits of institutions participating in NCI sponsored clinical trials. Methods: The RPC has developed an extensive Quality Assurance (QA) program over the past 44 years. This program includes on‐site dosimetry reviews where measurements on therapy machines are made, records are reviewed and personnel are interviewed. The program's remote audit tools include mailed dosimeters (OSLD/TLD) to verify output calibration, comparison of dosimetry data with RPC ‘standard’ data, evaluation of benchmark and patient calculations to verify the treatment planning algorithms, review of institution's QA procedures and records, and use of anthropomorphic phantoms to verify tumordose delivery. The RPC endeavors to assist institutions in finding the origins of any detected discrepancies, and to resolve them. Results: Ninety percent of institutions receiving dosimetry recommendations has remained level for the past 5 years. The most frequent recommendations were for not performing TG‐40 QA tests, wedge factors, small field size output factors and off‐axis factors. Since TG‐51 was published, the number of beam calibrations audited during visits with ion chambers, that met the RPC's ±3% criterion, decreased initially but has risen to pre‐TG‐51 levels. The OSLD/TLD program shows that only ∼3% of the beams are outside our ±5% criteria, but these discrepancies are distributed over 12–20% of the institutions. The percent of institutions with i,3l beam outside the RPC's criteria is approximately the same whether OSLD/TLD or ion chambers were used. The first time passing rate for the anthropomorphic phantoms is increasing with time. The prostate phantom has the highest pass rate while the spine phantom has the lowest. Conclusions: Numerous dosimetry errors continue to be discovered by the RPC's QA program and the RPC continues to play an important role in helping institutions resolve these errors. This work was supported by PHS grants CA10953 and CA081647 awarded by NCI.

We would like to correct a sentence on p. 2932, Sec. III E. General Patient Safety, Treatment Procedure Monitoring. The incorrect sentence reads: “We recommend that in addition to the treating therapist, a second medical professional (therapist, physicist, or physician) should be in the immediate vicinity at all times to assist when necessary. The corrected section follows below. We regret the error and hope the revised text will clarify the task groups recommendations in regards to the role of QMPs in treatment supervision. Glossary: Personal supervision—Physicist is present at the treatment console. Direct supervision—Physicist is in the department, available for immediate response. Corrected text: All treatments must occur under direct supervision of a QMP. In addition, a QMP must provide personal supervision at the first treatment, and as needed for subsequent treatments. The personal supervision should include participation in a timeout checklist, assessment of patient immobilization, assessment of adequate imaging parameters, tracking accuracy and correct Synchrony respiratory modeling (if applicable), consultation on excessive or unusual patient shift requirements during treatment not clearly caused by patient motion on the treatment couch, as well as other patientor plan-specific needs.

Purpose: The Radiological Physics Center (RPC) reviews patient records on brachytherapy cervix trials for completeness, consistency with the protocol and dosimetric accuracy to minimize patient dose delivery and reporting uncertainty for NCI funded clinical trials. Within cervical protocols, bladder and rectum doses are specified to limit toxicity to these normal tissues. However, bladder and rectal doses reported by institutions often disagree with the RPC's calculated doses. The RPC has investigated the sources of these disagreements. Methods: The RPC reviewed 182 HDR brachytherapy (tandem and ovoids (T&O)/tandem and ring (T&R)) implants and compared the institution's bladder and rectum point locations and doses to those determined by the RPC strictly adhering to protocol specifications (ICRU 38) for point location and using its independent dose calculation algorithm. The RPC also analyzed its own uncertainty in defining these two points. A dose agreement criterion of ±15% was used as agreed upon by the study group and RPC. Results: The RPC disagreed with the bladder and rectal doses in 25% and 45%, respectively, of the 182 implants. The RPC's own uncertainty in defining the bladder and rectal points was 1mm±0. 1(STDEV), respectively which in a worst case scenario might account for 7% of the dose disagreement. The majority of the dose disagreements were due to the institution's incorrect localization of the bladder and rectal points, by greater than 5mm and 4mm, respectively, away from the ICRU 38 defined location. There were no differences noted whether the applicator used was a T&O or T&R. Conclusions: Most errors resulted from institutions incorrectly defining the bladder and rectum dose calculation points per ICRU 38. Additional education, timely reviews of implant data and communication with institutions are needed to reduce the number of discrepancies. Work supported by PHS grant CA 10953 awarded by NCI, DHHS

Purpose: One of the RPC's quality audits used to assure the NCI and Cooperative Trial Groups that institutions participating in clinical trials deliver and report radiation doses that are clinically comparable and consistent is a retrospective review of clinical patient treatment charts. However, there is no standard regarding what patient and dosimetry data to include within a submitted trial patient's chart depending on treatment modality (brachytherapy vs. external beam) and protocol specific requirements. This work identifies the required data needed to perform a clinical trial quality audit review based on the evaluation of nearly 2000 patient charts. Methods: Since 2005, the RPC reviewed 1997 patient charts equating to over 13,000 points of calculation. In order to perform these dose recalculations, a minimal amount of data is needed for external beam and brachytherapytreatments. A review of these charts has identified the required patient specific and machine specific data required. In addition the data needs to be submitted in a useable format (CTimages submitted in DICOM format, isodose lines and DVHs in color). Results: Comprehensive data requirements for external beam and brachytherapy are presented. Since 2005, the RPC sent out 1021 letters requesting data or clarifications regarding the treatment. 86% of these requests were for patient specific information. The most common information omitted from a brachytherapy chart were the HDR dwell times and locations, and for external beam charts it was the daily treatment records indicating the monitor units delivered per field. Conclusions: For the RPC to state that trial patient doses are clinically comparable and consistent, the necessary patient and dosimetry data must be submitted in a timely manner. Development of a required data submission checklist to be included with each protocol will minimize trial data submission deficiencies and increase the efficiency of the RPC's quality audits. Work supported by PHS grant CA 10953 awarded by NCI, DHHS