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.

Stage III Non-Small Cell Lung Cancer: Prognostic Value of FDG PET Quantitative Imaging Features Combined with Clinical Prognostic Factors.

PURPOSE: To determine whether quantitative imaging features from pretreatment positron emission tomography (PET) can enhance patient overall survival risk stratification beyond what can be achieved with conventional prognostic factors in patients with stage III non-small cell lung cancer (NSCLC). MATERIALS AND METHODS: The institutional review board approved this retrospective chart review study and waived the requirement to obtain informed consent. The authors retrospectively identified 195 patients with stage III NSCLC treated definitively with radiation therapy between January 2008 and January 2013. All patients underwent pretreatment PET/computed tomography before treatment. Conventional PET metrics, along with histogram, shape and volume, and co-occurrence matrix features, were extracted. Linear predictors of overall survival were developed from leave-one-out cross-validation. Predictive Kaplan-Meier curves were used to compare the linear predictors with both quantitative imaging features and conventional prognostic factors to those generated with conventional prognostic factors alone. The Harrell concordance index was used to quantify the discriminatory power of the linear predictors for survival differences of at least 0, 6, 12, 18, and 24 months. Models were generated with features present in more than 50% of the cross-validation folds. RESULTS: Linear predictors of overall survival generated with both quantitative imaging features and conventional prognostic factors demonstrated improved risk stratification compared with those generated with conventional prognostic factors alone in terms of log-rank statistic (P = .18 vs P = .0001, respectively) and concordance index (0.62 vs 0.58, respectively). The use of quantitative imaging features selected during cross-validation improved the model using conventional prognostic factors alone (P = .007). Disease solidity and primary tumor energy from the co-occurrence matrix were found to be selected in all folds of cross-validation. CONCLUSION: Pretreatment PET features were associated with overall survival when adjusting for conventional prognostic factors in patients with stage III NSCLC.

Interstitial Brachytherapy for the Treatment of Locally Recurrent Anorectal Cancer.

BACKGROUND: Local tumor control (LC), overall survival (OS), symptom palliation, and late toxicity for patients with locally recurrent anorectal cancer treated with a computed tomography (CT)-guided interstitial brachytherapy implant were examined. METHODS: The medical records of 20 consecutive patients who had received interstitial brachytherapy for locally recurrent anorectal cancer from 2000 through 2012 were reviewed. Seventeen patients (85 %) had rectal cancer and three had anal cancer [median follow-up time for living patients, 23 months (range 13-132)]. Brachytherapy was used most commonly at the second pelvic recurrence (n = 13, 65 %). The implant dose was prescribed to 80 Gy to a 1-cm margin or 120 Gy to 100 % of the gross tumor volume. Endpoints were OS, LC, toxicity, and symptom palliation rate, all calculated from the time of implant. RESULTS: The actuarial 1-year rates of LC and OS were 80 and 95 %, respectively. At presentation, 17 patients (85 %) had symptoms related to the treated tumor which were palliated in 13 patients (76 %) at a median time of 3 months (range 1-6); palliation was permanent for seven patients (54 %), and the other six patients lost palliation after a median 8 months (range 5-17). One patient experienced a grade 3 late complication requiring a stent for hydronephrosis; five had grade 2 toxicity, and four had grade 1 toxicity. CONCLUSIONS: CT-guided interstitial brachytherapy for locally recurrent anorectal tumors produced durable tumor control and long-term survival, with effective palliation and minimal long-term morbidity.

Evaluation of 4D CT acquisition methods designed to reduce artifacts.

Four-dimensional computed tomography (4D CT) is used to account for respiratory motion in radiation treatment planning, but artifacts resulting from the acquisition and postprocessing limit its accuracy. We investigated the efficacy of three experimental 4D CT acquisition methods to reduce artifacts in a prospective institutional review board approved study. Eighteen thoracic patients scheduled to undergo radiation therapy received standard clinical 4D CT scans followed by each of the alternative 4D CT acquisitions: 1) data oversampling, 2) beam gating with breathing irregularities, and 3) rescanning the clinical acquisition acquired during irregular breathing. Relative values of a validated correlation-based artifact metric (CM) determined the best acquisition method per patient. Each 4D CT was processed by an extended phase sorting approach that optimizes the quantitative artifact metric (CM sorting). The clinical acquisitions were also postprocessed by phase sorting for artifact comparison of our current clinical implementation with the experimental methods. The oversampling acquisition achieved the lowest artifact presence among all acquisitions, achieving a 27% reduction from the current clinical 4D CT implementation (95% confidence interval = 34-20). The rescan method presented a significantly higher artifact presence from the clinical acquisition (37%; p < 0.002), the gating acquisition (26%; p < 0.005), and the oversampling acquisition (31%; p < 0.001), while the data lacked evidence of a significant difference between the clinical, gating, and oversampling methods. The oversampling acquisition reduced artifact presence from the current clinical 4D CT implementation to the largest degree and provided the simplest and most reproducible implementation. The rescan acquisition increased artifact presence significantly, compared to all acquisitions, and suffered from combination of data from independent scans over which large internal anatomic shifts occurred.

An anthropomorphic spine phantom for proton beam approval in NCI-funded trials.

As part of the approval process for the use of scattered or uniform scanning proton therapy in National Cancer Institute (NCI)-sponsored clinical trials, the Radiological Physics Center (RPC) mandates irradiation of two RPC anthropomorphic proton phantoms (prostate and spine). The RPC evaluates these irradiations to ensure that they agree with the institutions' treatment plans within criteria of the NCI-funded cooperative study groups. The purpose of this study was to evaluate the use of an anthropomorphic spine phantom for proton matched-field irradiation, and to assess its use as a credentialing tool for proton therapy beams. We used an anthropomorphic spine phantom made of human vertebral bodies embedded in a tissue substitute material called Muscle Substitute/Solid Rigid Number 4 (MS/SR4) comprising three sections: a posterior section containing the posterior surface and the spinous processes, and left and right (L/R) sections containing the vertebral bodies and the transverse processes. After feasibility studies at three institutions, the phantom, containing two thermoluminescent dosimeters (TLDs) for absolute dose measurements and two sheets of radiochromic film for relative dosimetry, was shipped consecutively to eight proton therapy centers participating in the approval study. At each center, the phantom was placed in a supine or prone position (according to the institution's spine treatment protocol) and imaged with computed tomography (CT). The images then were used with the institution's treatment planning system (TPS) to generate two matched fields, and the phantom was irradiated accordingly. The irradiated phantom was shipped to the RPC for analysis, and the measured values were compared with the institution's TPS dose and profiles using criteria of ± 7% for dose agreement and 5 mm for profile distance to agreement. All proton centers passed the dose criterion with a mean agreement of 3% (maximum observed agreement, 7%). One center failed the profile distance-to-agreement criterion on its initial irradiation, but its second irradiation passed the criterion. Another center failed the profile distance-to-agreement criterion, but no repeat irradiation was performed. Thus, seven of the eight institutions passed the film profile distance-to-agreement criterion with a mean agreement of 1.2 mm (maximum observed agreement 5 mm). We conclude that an anthropomorphic spine phantom using TLD and radiochromic film adequately verified dose delivery and field placement for matched-field treatments.

Comparison of an anthropomorphic PRESAGE® dosimeter and radiochromic film with a commercial radiation treatment planning system for breast IMRT: a feasibility study.

This work presents a comparison of an anthropomorphic PRESAGE® dosimeter and radiochromic film measurements with a commercial treatment planning system to determine the feasibility of PRESAGE® for 3D dosimetry in breast IMRT. An anthropomorphic PRESAGE® phantom was created in the shape of a breast phantom. A five-field IMRT plan was generated with a commercially available treatment planning system and delivered to the PRESAGE® phantom. The anthropomorphic PRESAGE® was scanned with the Duke midsized optical CT scanner (DMOS-RPC) and the OD distribution was converted to dose. Comparisons were performed between the dose distribution calculated with the Pinnacle3 treatment planning system, PRESAGE®, and EBT2 film measurements. DVHs, gamma maps, and line profiles were used to evaluate the agreement. Gamma map comparisons showed that Pinnacle3 agreed with PRESAGE® as greater than 95% of comparison points for the PTV passed a ± 3%/± 3 mm criterion when the outer 8 mm of phantom data were discluded. Edge artifacts were observed in the optical CT reconstruction, from the surface to approximately 8 mm depth. These artifacts resulted in dose differences between Pinnacle3 and PRESAGE® of up to 5% between the surface and a depth of 8 mm and decreased with increasing depth in the phantom. Line profile comparisons between all three independent measurements yielded a maximum difference of 2% within the central 80% of the field width. For the breast IMRT plan studied, the Pinnacle3 calculations agreed with PRESAGE® measurements to within the ±3%/± 3 mm gamma criterion. This work demonstrates the feasibility of the PRESAGE® to be fashioned into anthropomorphic shape, and establishes the accuracy of Pinnacle3 for breast IMRT. Furthermore, these data have established the groundwork for future investigations into 3D dosimetry with more complex anthropomorphic phantoms.

Assessment of a quantitative metric for 4D CT artifact evaluation by observer consensus.

The benefits of four-dimensional computed tomography (4D CT) are limited by the presence of artifacts that remain difficult to quantify. A correlation-based metric previously proposed for ciné 4D CT artifact identification was further validated as an independent artifact evaluator by using a novel qualitative assessment featuring a group of observers reaching a consensus decision on artifact location and magnitude. The consensus group evaluated ten ciné 4D CT scans for artifacts over each breathing phase of coronal lung views assuming one artifact per couch location. Each artifact was assigned a magnitude score of 1-5, 1 indicating lowest severity and 5 indicating highest severity. Consensus group results served as the ground truth for assessment of the correlation metric. The ten patients were split into two cohorts; cohort 1 generated an artifact identification threshold derived from receiver operating characteristic analysis using the Youden Index, while cohort 2 generated sensitivity and specificity values from application of the artifact threshold. The Pearson correlation coefficient was calculated between the correlation metric values and the consensus group scores for both cohorts. The average sensitivity and specificity values found with application of the artifact threshold were 0.703 and 0.476, respectively. The correlation coefficients of artifact magnitudes for cohort 1 and 2 were 0.80 and 0.61, respectively, (p < 0.001 for both); these correlation coefficients included a few scans with only two of the five possible magnitude scores. Artifact incidence was associated with breathing phase (p < 0.002), with presentation less likely near maximum exhale. Overall, the correlation metric allowed accurate and automated artifact identification. The consensus group evaluation resulted in efficient qualitative scoring, reduced interobserver variation, and provided consistent identification of artifact location and magnitudes.

Relative stopping power measurements to aid in the design of anthropomorphic phantoms for proton radiotherapy.

The delivery of accurate proton dose for clinical trials requires that the appropriate conversion function from Hounsfield unit (HU) to relative linear stopping power (RLSP) be used in proton treatment planning systems (TPS). One way of verifying that the TPS is calculating the correct dose is an end-to-end test using an anthropomorphic phantom containing tissue equivalent materials and dosimeters. Many of the phantoms in use for such end-to-end tests were originally designed using tissue-equivalent materials that had physical characteristics to match patient tissues when irradiated with megavoltage photon beams. The aim of this study was to measure the RLSP of materials used in the phantoms, as well as alternative materials to enable modifying phantoms for use at proton therapy centers. Samples of materials used and projected for use in the phantoms were measured and compared to the HU assigned by the treatment planning system. A percent difference in RLSP of 5% was used as the cutoff for materials deemed acceptable for use in proton therapy (i.e., proton equivalent). Until proper tissue-substitute materials are identified and incorporated, institutions that conduct end-to-end tests with the phantoms are instructed to override the TPS with the measured stopping powers we provide. To date, the RLSPs of 18 materials have been measured using a water phantom and/or multilayer ion chamber (MLIC). Nine materials were identified as acceptable for use in anthropomorphic phantoms. Some of the failing tissue substitute materials are still used in the current phantoms. Further investigation for additional appropriate tissue substitute materials in proton beams is ongoing. Until all anthropomorphic phantoms are constructed of appropriate materials, a unique HU-RLSP phantom has been developed to be used during site visits to verify the proton facility's treatment planning HU-RLSP calibration curve.

Essentials and guidelines for clinical medical physics residency training programs: executive summary of AAPM Report Number 249.

There is a clear need for established standards for medical physics residency training. The complexity of techniques in imaging, nuclear medicine, and radiation oncology continues to increase with each passing year. It is therefore imperative that training requirements and competencies are routinely reviewed and updated to reflect the changing environment in hospitals and clinics across the country. In 2010, the AAPM Work Group on Periodic Review of Medical Physics Residency Training was formed and charged with updating AAPM Report Number 90. This work group includes AAPM members with extensive experience in clinical, professional, and educational aspects of medical physics. The resulting report, AAPM Report Number 249, concentrates on the clinical and professional knowledge needed to function independently as a practicing medical physicist in the areas of radiation oncology, imaging, and nuclear medicine, and constitutes a revision to AAPM Report Number 90. This manuscript presents an executive summary of AAPM Report Number 249.

Development of a modified head and neck quality assurance phantom for use in stereotactic radiosurgery trials.

An anthropomorphic head phantom, constructed from a water-equivalent plastic shell with only a spherical target, was modified to include a nonspherical target (pituitary) and an adjacent organ at risk (OAR) (optic chiasm), within 2 mm, simulating the anatomy encountered when treating acromegaly. The target and OAR spatial proximity provided a more realistic treatment planning and dose delivery exercise. A separate dosimetry insert contained two TLD for absolute dosimetry and radiochromic film, in the sagittal and coronal planes, for relative dosimetry. The prescription was 25 Gy to 90% of the GTV, with ≤ 10% of the OAR volume receiving ≥ 8 Gy for the phantom trial. The modified phantom was used to test the rigor of the treatment planning process and phantom reproducibility using a Gamma Knife, CyberKnife, and linear accelerator (linac)-based radiosurgery system. Delivery reproducibility was tested by repeating each irradiation three times. TLD results from three irradiations on a CyberKnife and Gamma Knife agreed with the calculated target dose to within ± 4% with a maximum coefficient of variation of ± 2.1%. Gamma analysis in the coronal and sagittal film planes showed an average passing rate of 99.4% and 99.5% using ± 5%/3 mm criteria, respectively. Results from the linac irradiation were within ± 6.2% for TLD with a coefficient of variation of ± 0.1%. Distance to agreement was calculated to be 1.2 mm and 1.3mm along the inferior and superior edges of the target in the sagittal film plane, and 1.2 mm for both superior and inferior edges in the coronal film plane. A modified, anatomically realistic SRS phantom was developed that provided a realistic clinical planning and delivery challenge that can be used to credential institutions wanting to participate in NCI-funded clinical trials.

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.

Dose calculation for photon-emitting brachytherapy sources with average energy higher than 50 keV: report of the AAPM and ESTRO.

PURPOSE: Recommendations of the American Association of Physicists in Medicine (AAPM) and the European Society for Radiotherapy and Oncology (ESTRO) on dose calculations for high-energy (average energy higher than 50 keV) photon-emitting brachytherapy sources are presented, including the physical characteristics of specific (192)Ir, (137)Cs, and (60)Co source models. METHODS: This report has been prepared by the High Energy Brachytherapy Source Dosimetry (HEBD) Working Group. This report includes considerations in the application of the TG-43U1 formalism to high-energy photon-emitting sources with particular attention to phantom size effects, interpolation accuracy dependence on dose calculation grid size, and dosimetry parameter dependence on source active length. RESULTS: Consensus datasets for commercially available high-energy photon sources are provided, along with recommended methods for evaluating these datasets. Recommendations on dosimetry characterization methods, mainly using experimental procedures and Monte Carlo, are established and discussed. Also included are methodological recommendations on detector choice, detector energy response characterization and phantom materials, and measurement specification methodology. Uncertainty analyses are discussed and recommendations for high-energy sources without consensus datasets are given. CONCLUSIONS: Recommended consensus datasets for high-energy sources have been derived for sources that were commercially available as of January 2010. Data are presented according to the AAPM TG-43U1 formalism, with modified interpolation and extrapolation techniques of the AAPM TG-43U1S1 report for the 2D anisotropy function and radial dose function.

The Radiological Physics Center's standard dataset for small field size output factors.

Delivery of accurate intensity-modulated radiation therapy (IMRT) or stereotactic radiotherapy depends on a multitude of steps in the treatment delivery process. These steps range from imaging of the patient to dose calculation to machine delivery of the treatment plan. Within the treatment planning system's (TPS) dose calculation algorithm, various unique small field dosimetry parameters are essential, such as multileaf collimator modeling and field size dependence of the output. One of the largest challenges in this process is determining accurate small field size output factors. The Radiological Physics Center (RPC), as part of its mission to ensure that institutions deliver comparable and consistent radiation doses to their patients, conducts on-site dosimetry review visits to institutions. As a part of the on-site audit, the RPC measures the small field size output factors as might be used in IMRT treatments, and compares the resulting field size dependent output factors to values calculated by the institution's treatment planning system (TPS). The RPC has gathered multiple small field size output factor datasets for X-ray energies ranging from 6 to 18 MV from Varian, Siemens and Elekta linear accelerators. These datasets were measured at 10 cm depth and ranged from 10 × 10 cm(2) to 2 × 2 cm(2). The field sizes were defined by the MLC and for the Varian machines the secondary jaws were maintained at a 10 × 10 cm(2). The RPC measurements were made with a micro-ion chamber whose volume was small enough to gather a full ionization reading even for the 2 × 2 cm(2) field size. The RPC-measured output factors are tabulated and are reproducible with standard deviations (SD) ranging from 0.1% to 1.5%, while the institutions' calculated values had a much larger SD range, ranging up to 7.9% [corrected].The absolute average percent differences were greater for the 2 × 2 cm(2) than for the other field sizes. The RPC's measured small field output factors provide institutions with a standard dataset against which to compare their TPS calculated values. Any discrepancies noted between the standard dataset and calculated values should be investigated with careful measurements and with attention to the specific beam model.

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.

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.

Angular dependence of the nanoDot OSL dosimeter.

PURPOSE: Optically stimulated luminescent detectors (OSLDs) are quickly gaining popularity as passive dosimeters, with applications in medicine for linac output calibration verification, brachytherapy source verification, treatment plan quality assurance, and clinical dose measurements. With such wide applications, these dosimeters must be characterized for numerous factors affecting their response. The most abundant commercial OSLD is the InLight/OSL system from Landauer, Inc. The purpose of this study was to examine the angular dependence of the nanoDot dosimeter, which is part of the InLight system. METHODS: Relative dosimeter response data were taken at several angles in 6 and 18 MV photon beams, as well as a clinical proton beam. These measurements were done within a phantom at a depth beyond the build-up region. To verify the observed angular dependence, additional measurements were conducted as well as Monte Carlo simulations in MCNPX. RESULTS: When irradiated with the incident photon beams parallel to the plane of the dosimeter, the nanoDot response was 4% lower at 6 MV and 3% lower at 18 MV than the response when irradiated with the incident beam normal to the plane of the dosimeter. Monte Carlo simulations at 6 MV showed similar results to the experimental values. Examination of the results in Monte Carlo suggests the cause as partial volume irradiation. In a clinical proton beam, no angular dependence was found. CONCLUSIONS: A nontrivial angular response of this OSLD was observed in photon beams. This factor may need to be accounted for when evaluating doses from photon beams incident from a variety of directions.

Safety considerations for IMRT: executive summary.

This report on intensity-modulated radiation therapy (IMRT) is part of a series of white papers addressing patient safety commissioned by the American Society for Radiation Oncology's (ASTRO) Target Safely Campaign. The document has been approved by the ASTRO Board of Directors, endorsed by the American Association of Physicists in Medicine (AAPM) and American Association of Medical Dosimetrists (AAMD), and reviewed and accepted by the American College of Radiology's Commission on Radiation Oncology. This report is related to other reports of the ASTRO white paper series on patient safety which are still in preparation, and when appropriate it defers to guidance that will be published by those groups in future white papers. This document takes advantage of the large body of work on quality assurance and quality control principles within radiation oncology whenever possible. IMRT provides increased capability to conform isodose distributions to the shape of the target(s), thereby reducing dose to some adjacent critical structures. This promise of IMRT is one of the reasons for its widespread use. However, the promise of IMRT is counterbalanced by the complexity of the IMRT planning and delivery processes, and the associated risks, some of which have been demonstrated by the New York Times reports on serious accidents involving both IMRT and other radiation treatment modalities. This report provides an opportunity to broadly address safe delivery of IMRT, with a primary focus on recommendations for human error prevention and methods to reduce the occurrence of errors or machine malfunctions that can lead to catastrophic failures or errors.

A dosimetric uncertainty analysis for photon-emitting brachytherapy sources: report of AAPM Task Group No. 138 and GEC-ESTRO.

This report addresses uncertainties pertaining to brachytherapy single-source dosimetry preceding clinical use. The International Organization for Standardization (ISO) Guide to the Expression of Uncertainty in Measurement (GUM) and the National Institute of Standards and Technology (NIST) Technical Note 1297 are taken as reference standards for uncertainty formalism. Uncertainties in using detectors to measure or utilizing Monte Carlo methods to estimate brachytherapy dose distributions are provided with discussion of the components intrinsic to the overall dosimetric assessment. Uncertainties provided are based on published observations and cited when available. The uncertainty propagation from the primary calibration standard through transfer to the clinic for air-kerma strength is covered first. Uncertainties in each of the brachytherapy dosimetry parameters of the TG-43 formalism are then explored, ending with transfer to the clinic and recommended approaches. Dosimetric uncertainties during treatment delivery are considered briefly but are not included in the detailed analysis. For low- and high-energy brachytherapy sources of low dose rate and high dose rate, a combined dosimetric uncertainty <5% (k=1) is estimated, which is consistent with prior literature estimates. Recommendations are provided for clinical medical physicists, dosimetry investigators, and source and treatment planning system manufacturers. These recommendations include the use of the GUM and NIST reports, a requirement of constancy of manufacturer source design, dosimetry investigator guidelines, provision of the lowest uncertainty for patient treatment dosimetry, and the establishment of an action level based on dosimetric uncertainty. These recommendations reflect the guidance of the American Association of Physicists in Medicine (AAPM) and the Groupe Européen de Curiethérapie-European Society for Therapeutic Radiology and Oncology (GEC-ESTRO) for their members and may also be used as guidance to manufacturers and regulatory agencies in developing good manufacturing practices for sources used in routine clinical treatments.

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.

Radiologic and nuclear medicine studies in the United States and worldwide: frequency, radiation dose, and comparison with other radiation sources--1950-2007.

The U.S. National Council on Radiation Protection and Measurements and United Nations Scientific Committee on Effects of Atomic Radiation each conducted respective assessments of all radiation sources in the United States and worldwide. The goal of this article is to summarize and combine the results of these two publicly available surveys and to compare the results with historical information. In the United States in 2006, about 377 million diagnostic and interventional radiologic examinations and 18 million nuclear medicine examinations were performed. The United States accounts for about 12% of radiologic procedures and about one-half of nuclear medicine procedures performed worldwide. In the United States, the frequency of diagnostic radiologic examinations has increased almost 10-fold (1950-2006). The U.S. per-capita annual effective dose from medical procedures has increased about sixfold (0.5 mSv [1980] to 3.0 mSv [2006]). Worldwide estimates for 2000-2007 indicate that 3.6 billion medical procedures with ionizing radiation (3.1 billion diagnostic radiologic, 0.5 billion dental, and 37 million nuclear medicine examinations) are performed annually. Worldwide, the average annual per-capita effective dose from medicine (about 0.6 mSv of the total 3.0 mSv received from all sources) has approximately doubled in the past 10-15 years.