Purpose: Limited data exist regarding the range of heart doses received in routine practice with radiation therapy (RT) for breast cancer in the United States today and the potential effect of the continual assessment of the cardiac dose on practice patterns. Methods and Materials: From 2012 to 2015, 4688 patients with breast cancer treated with whole breast RT at 20 sites participating in a state-wide consortium were enrolled into a registry. The importance of limiting the cardiac dose has been emphasized in the consortium since 2012, and the mean heart dose (MHD) has been reported by each institution since 2014. The effects on the MHD were estimated for both conventional and accelerated fractionation using regression models, with technique (intensity modulated RT [IMRT] vs 3-dimensional conformal RT), deep inspiration breath hold use, patient position (supine vs prone), nodal RT (if delivered), and boost (yes vs no) as covariates. Results: For left-sided breast cancer treated with conventional fractionation, the median MHD in 2012 was 2.19 Gy versus 1.65 Gy in 2015 (P<.001). The factors that significantly increased the MHD for conventional fractionation were increased separation relative to 22 cm (1.5%/1 cm), supraclavicular or infraclavicular nodal RT (17.1%), internal mammary nodal RT (40.7%), use of a boost (20.9%), treatment year before 2015 (7.7%), and use of IMRT (20.8%). For left-sided BC treated with accelerated fractionation, the median MHD in 2012 was 1.70 Gy versus 1.22 Gy in 2015 (P<.001). The factors that significantly increased the MHD for accelerated fractionation were separation (1.7%/1 cm), use of a boost (20.0%), year before 2015 (8.5%), and use of IMRT (19.2%). The factors for both conventional fractionation and accelerated fractionation that significantly reduced the MHD were the use of deep inspiration breath hold and prone positioning. Conclusions: The MHD for left-sided breast cancer decreased during a recent 4-year period, coincident with an increased focus on cardiac sparing in the radiation oncology community in general and a state-wide consortium specifically. These data suggest a positive effect of systematically monitoring the heart dose delivered. (C) 2017 Elsevier Inc. All rights reserved.

Purpose: A database in which patient data are compiled allows analytic opportunities for continuous improvements in treatment quality and comparative effectiveness research. We describe the development of a novel, web-based system that supports the collection of complex radiation treatment planning information from centers that use diverse techniques, software, and hardware for radiation oncology care in a statewide quality collaborative, the Michigan Radiation Oncology Quality Consortium (MROQC).Methods and materials: The MROQC database seeks to enable assessment of physician-and patient-reported outcomes and quality improvement as a function of treatment planning and delivery techniques for breast and lung cancer patients. We created tools to collect anonymized data based on all plans.Results: The MROQC system representing 24 institutions has been successfully deployed in the state of Michigan. Since 2012, dose-volume histogram and Digital Imaging and Communications in Medicine-radiation therapy plan data and information on simulation, planning, and delivery techniques have been collected. Audits indicated >90% accurate data submission and spurred refinements to data collection methodology.Conclusions: This model web-based system captures detailed, high-quality radiation therapy dosimetry data along with patient- and physician-reported outcomes and clinical data for a radiation therapy collaborative quality initiative. The collaborative nature of the project has been integral to its success. Our methodology can be applied to setting up analogous consortiums and databases. (C) 2016 American Society for Radiation Oncology. Published by Elsevier Inc. All rights reserved.

This white paper recommends the standardization (content and presentation order) of several "key components" of the radiation therapy prescription to facilitate accurate communication between radiation therapy care providers. The rationale, other similar efforts, and detailed considerations are described. In brief, the Task Force recommends that the prescription's "elements" include: treatment site, method of delivery, dose per fraction, total number of fractions, total dose (eg, right breast, tangent photons, 267 cGy * 16 = 4272 cGy). A similar formalism is recommended for brachytherapy (eg, cervix, Ir-192 brachytherapy, 600cGy * 5 = 3000 cGy) and other modalities. The white paper also considers future directions for other items such as the simulation order, treatment planning objectives, prescription point or volume, treatment schedule, localization imaging, laboratory monitoring, concurrent chemotherapy, patient instructions for treatment, etc. The intent of this white paper is to facilitate accurate communication among providers to support safe practice as well as to guide vendors in product development that is consistent with this standard prescription.

IMPORTANCE Randomized trials have established the long-term safety and efficacy of hypofractionated whole-breast radiotherapy, but little is known about the acute toxic effects experienced by patients treated with hypofractionation as compared with conventional fractionation, particularly in real-world settings and from the patient's own perspective.OBJECTIVE To evaluate prospectively collected data on acute toxic effects and patient-reported outcomes in a cohort treated with varying radiation fractionation schemes in practices collaborating in the Michigan Radiation Oncology Quality Consortium (MROQC).DESIGN, SETTING, AND PARTICIPANTS We compared toxic effects in patients receiving hypofractionation (HF) vs conventional fractionation (CF) during treatment (through 7 days after treatment) and in follow-up (posttreatment days 8-210), after adjustment for sociodemographic, clinical, and treatment characteristics. The MROQC includes academic and community radiation oncology practices across Michigan. All 2604 patients who received adjuvant whole-breast radiotherapy after lumpectomy for unilateral breast cancer at MROQC participating sites from October 2011 through June 2014 were registered; we analyzed 2309 for whom there was a comprehensive physician toxicity evaluation within 1 week of completion of radiotherapy and at least 1 weekly toxicity evaluation during treatment.EXPOSURES Hypofractionation vs CF.MAIN OUTCOMES AND MEASURES Physicians reported dermatitis, pain, fatigue, and other common toxic effects associated with breast radiotherapy at baseline, weekly during radiotherapy, and in follow-up. Patients who consented also rated their own experiences, including breast pain, fatigue, and being bothered by symptoms.RESULTS Of the 2309 evaluable patients, 578 received HF. During treatment, after adjustment for sociodemographic, clinical, and treatment factors, patients receiving CF had significantly higher maximum physician-assessed skin reaction (moist desquamation, 28.5% vs 6.6%, P<.001; grade >= 2 dermatitis, 62.6% vs 27.4%, P<.001), self-reported pain (moderate/severe pain, 41.1% vs 24.2%, P=.003), burning/stinging bother (often/always, 38.7% vs 15.7%, P=.002), hurting bother (33.5% vs 16.0%, P=.001), swelling bother (29.6% vs 15.7%, P=.03), and fatigue (29.7% vs 18.9%, P=.02) but slightly greater absence of skin induration in follow-up (84.5% vs 81.2%, P=.02). No significant differences were observed in any other measured outcomes during follow-up extending through 6 months.CONCLUSIONS AND RELEVANCE Hypofractionation not only improves convenience but also may reduce acute pain, fatigue, and the extent to which patients are bothered by dermatitis in patients with breast cancer undergoing whole-breast radiotherapy.

This study describes initial testing and evaluation of a vertical-field open Magnetic Resonance Imaging (MRI) scanner for the purpose of simulation in radiation therapy for prostate cancer. We have evaluated the clinical workflow of using open MRI as a sole modality for simulation and planning. Relevant results related to MRI alignment (vs. CT) reference dataset with Cone-Beam CT (CBCT) for daily localization are presented.

Purpose: As part of the continuous quality of care improvement, an internal online database for processing reported incidents was established. In 3 years, 710 incidents were reported by 5 clinics. We have ranked the fault trees of the reported incidents using the AAPM report TG‐100 Failure Mode and Effects Analysis (FMEA) tools Methods: Risk Probability Number (RPN) generated as a Result of applying FMEA is based on the severity, probability of occurrence and probability of going undetected. The reports were sorted in two categories. Potentially affecting dose delivery, e.g. incorrect setup instructions; and deviations from an established workflow defined by policies and procedures (P&P), e.g., incorrect naming of the fields. In addition to FMEA, the impact of new, as well as periodic reviews of P&P by staff members is assessed Results: Of 710 reports 676 were analyzed, 374 were variation in the workflow not directly affecting quality of care, 302 were potentially affecting dose delivery. 19 of 302 had dosimetric impact; however, due to low occurrence only 4 instances, related to bolus placement, reached the RPN above 200. Review of current P&P reduced the RPN from 270 to 9. Periodic review, introduction of the new or revising the existing P&P had a dual effect: drop in dose‐affecting incidents and increased reporting of process deviations Conclusion: Analysis of reported incidents and review by the departmental QA committee is an essential part of any QA program. By defining the fault trees and applying FMEA to the reported incidents, we were able to reduce the RPN from an average of 150 for dose related incidents to 9, and for process variations from 295 to 28 on average. Event‐triggered revising of P&Ps and periodic review with staff of the existing P&P is an effective tool in incident reduction

Purpose: A collaborative quality initiative (CQI) has been developed in the state of Michigan to assess physician and patient reported outcomes to compare conformal and IMRT techniques for a specific cohort of breast and lung cancer patients. Here, we present a web‐based database that was designed to collect planning and delivery information to facilitate analysis of outcomes for the CQI. Methods: A web‐based database was built to capture key physics information, including dose that may be related to acute toxicities. An annual institutional questionnaire captures the technology available for these patients. A patient‐specific survey collects simulation, planning, and delivery information. To overcome differences in DVH file formats, a simple interface was developed where the user selects from a structure list, submits numeric data, and reviews the data summary. To analyze the delivery type, DICOM‐RT plan files are uploaded via a web interface. The data are anonymized and displayed for the user to verify that no protected health information is submitted. Results: Initial partner institutions tested and provided feedback on all aspects of the physics data collection. Institutions have shared customized programs for extracting DVH and DICOM‐RT data and documents for electronic workflow. Data submission began via the web portal in April 2012. There are 4 planning systems represented among the 14 institutions. Delivery techniques include static, dynamic and segmental MLC, Tomotherapy, and VMAT. As of February, data have been submitted for approximately 80% of the 815 eligible cases. Centers will be audited for data quality once per year. Conclusion: A system has been designed to capture high integrity simulation, plan, and delivery data for a CQI focused on breast and lung cancer. This information will be used to quantitatively evaluate the use of IMRT techniques in the state of Michigan and to permit dose‐based correlations to physician and patient‐rated toxicities. This work was funded by Blue Cross Blue Shield of Michigan.

Purpose: Over the past 3 years our institution has received 44 Customer Technical Bulletins (CTBs) from vendors that supply us with hardware of software used for patient care. We have ranked the failure modes presented to our institution in these CTBs using Failure Mode and Effects Analysis (FMEA) tools as described in the AAPM report TG‐100. Methods: FMEA applied to the failure modes comes up with a Risk Probability Number based on the severity, probability of occurrence and probability it will go undetected. In addition to FMEA, the adverse effects on our patient population are examined by looking at the number of people affected. For example, CTBs applying to dose calculations would affect 100% of our patients while CTBs applying to IMRT calculations will affect approximately 50% or our patient population. Results: Of the 44 CTBs received from vendors we identified nineteen with Risk Priority Numbers (RPN) greater than 200 and four of those had RPN greater than 300. Of the four with RPN greater than 300, two dealt with incorrect dose calculations due to incorrect commissioning of the treatment planning system, one with the CT datasets getting flipped and the last with isocenter being transferred incorrectly. Each of these failure pathways would have resulted in a systematic error that would have affected a large population of patients. For the failure modes with RPN greater than 200 the average RPN was reduced from 275 to 70 after modifying policy, checklists and improving clinical flow. Conclusion: Analysis of vendor CTBs and review by a departments QA committee is an essential part of any QA program. By applying FMEA and analyzing the fault trees discussed in these bulletins, we were able to reduce the RPN from an average of 275 to 70.

PURPOSE: To present a clinical procedure that readjusts catheters to its planned positions based on pretreatment computed tomography (CT) for patients undergoing high-dose-rate (HDR) prostate brachytherapy, and evaluate the magnitude and dosimetric impact of the adjustments.METHODS AND MATERIALS: Patients received a pretreatment verification CT (vCT) before each fraction. The vCT dataset was imported to the treatment-planning system and fused to the planning CT (pCT) by rigid-body registration based on the implanted fiducials within the prostate. Catheter positions in the vCT were then compared with catheter positions in the pCT in a reconstructed plane through each catheter. Any catheter with difference in penetration larger than 3 mm was manually adjusted by a radiation oncologist before treatment. To evaluate treatment quality, the patient's plan was applied to the vCT off-line and dose delivered to prostate and normal structures were compared with their planned value.RESULTS: Forty-four fractions of 13 consecutive patients were treated using this method. Thirty-nine fractions had at least one catheter adjusted before treatment. A total of 651 catheters were assessed, and 194 catheters (30%) were adjusted by an average amount of 5.8 +/- 1.9 mm. In eight fractions the prostate D-90 would have decreased by more than 10% from the planned value (with a maximum of 32%) if the catheter displacements were not rectified. After the adjustment, the maximum deviation of D-90 was 10.6%. The improvement in D-90 is 24% per 1 cm of time-averaged adjustment.CONCLUSIONS: Interfraction catheter motion occurs without any particular pattern. Using pretreatment CTs and restoring each catheter to its planned position ensures that the delivered treatment closely matches the treatment plan and therefore enhances the overall quality of the HDR treatment. The procedure can be readily implemented in any clinical setting. (C) 2013 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

Purpose: To evaluate the effect of using couch structures in IMRT planningMethods: Three TG‐119 IMRT plans (Head&Neck, Prostate, C‐shape hard) developed for commissioning the Varian Eclipse AAA 10.0.28 algorithm were delivered on a Varian 21EX with Exact Couch. This algorithm allows accounting for the effects of the treatment couch via a separate structure outside the external contour. Each plan was calculated twice (with and without couch), keeping monitor units and leaf motions the same to facilitate comparison. Plans were delivered to an ion chamber and an EBT2 film in a 30×3×20 cm3 phantom at two locations reflecting high and low dose regions per TG‐119. Additionally, 15 clinical cases (five each of 6MV H&N, 6MV prostate and 18MV prostate were delivered; four of the ten prostate cases included pelvic lymph node involvement. The film analysis (using in‐house software) required >95% points to pass a gamma criterion of 3%,3mm. Results: For the TG‐119 plans 99.1%±2.7% and 94.6%±19.9% of the points met the gamma 3%,3mm with and without the couch model respectively; the major contribution for the lower value (94.6%) was from the H&N plan for which only 85% of the points passed. Gamma results for clinical cases were: H&N (99.7%±0.9% and 97.4±7.9%), Prostate 6MV: (99.6%±1.8% and 94.7%±12.7%), Prostate 18MV results with and without the couch were nearly identical (99.8%±0.9% vs. 99.7%±1.1%, respectively). We also found the largest differences for posterior oblique beams traversing the couch rails: For 6MV prostate, there was no relative difference for beams striking the phantom only, 0.7% when treating entering through the couch, and 4.5% for beams traversing the rails. Conclusion: Including the couch structures is important for lower energies (6MV), especially for oblique beams traversing the couch rails. However, adjusting rail positions during delivery should improve agreement for algorithms which do not account for the couch.

Purpose: An important question rarely discussed in the CT vs. MRI simulation debate is whether MRI reference images provide an adequate image‐set to use with daily localization such as cone‐beam CT (CBCT). This study compares clinical couch shifts based on daily CBCT images to shifts measured from MR images as the reference dataset for prostate IMRT treatment. Methods: Eight patients undergoing a pilot study had MR imaging along with CT simulation with the intent of evaluating a MR‐simulation process. Patients had T1, T2 and bTFE (balanced Turbo Field Echo) sequences. The remainder of the treatment planning process continued using traditional procedures using CT. Therapists used only the CT scan as a reference for localization. Retrospectively, an observer measured shifts between daily CBCT images and MR reference images. Results: The differences in shift positions for the cohort between therapists and the observer are −0.16cm ± 0.25cm (AP), 0.04cm ± 0.19cm (SI), and — 0.01cm ± 0.14cm (LR). The mean group error for the therapists and the observer were less than 2 mm in all directions. Based on these shifts, the calculated margins for the therapists would be 0.87cm (AP), 0.65cm (SI), and 0.71cm (LR) and for the observer would be 1.1cm (AP), 0.66cm (SI), and 0.70cm (LR). For SI and LR directions both sets of margins are very close to one another. An outlier impacted the AP margin difference by 2.3mm and should be investigated further. This initial analysis suggests that each modality can be considered clinically sufficient for daily localization. Conclusion: The results of this study suggest that MR reference image‐sets can be used for daily image‐guided localization of prostate cancers with at least the same accuracy as current methods. MR simulation provides substantial soft‐tissue contrast and can improve tissue targeting in radiation oncology, as a Result further investigation is warranted.

The purpose of this work is to present the results of a margin reduction study involving dosimetric and radiobiologic assessment of cumulative dose distributions, computed using an image guided adaptive radiotherapy based framework. Eight prostate cancer patients, treated with 7–9, 6 MV, intensity modulated radiation therapy (IMRT) fields, were included in this study. The workflow consists of cone beam CT (CBCT) based localization, deformable image registration of the CBCT to simulation CT image datasets (SIM-CT), dose reconstruction and dose accumulation on the SIM-CT, and plan evaluation using radiobiological models. For each patient, three IMRT plans were generated with different margins applied to the CTV. The PTV margin for the original plan was 10 mm and 6 mm at the prostate/anterior rectal wall interface (10/6 mm) and was reduced to: (a) 5/3 mm, and (b) 3 mm uniformly. The average percent reductions in predicted tumor control probability (TCP) in the accumulated (actual) plans in comparison to the original plans over eight patients were 0.4%, 0.7% and 11.0% with 10/6 mm, 5/3 mm and 3 mm uniform margin respectively. The mean increase in predicted normal tissue complication probability (NTCP) for grades 2/3 rectal bleeding for the actual plans in comparison to the static plans with margins of 10/6, 5/3 and 3 mm uniformly was 3.5%, 2.8% and 2.4% respectively. For the actual dose distributions, predicted NTCP for late rectal bleeding was reduced by 3.6% on average when the margin was reduced from 10/6 mm to 5/3 mm, and further reduced by 1.0% on average when the margin was reduced to 3 mm. The average reduction in complication free tumor control probability (P+) in the actual plans in comparison to the original plans with margins of 10/6, 5/3 and 3 mm was 3.7%, 2.4% and 13.6% correspondingly. The significant reduction of TCP and P+ in the actual plan with 3 mm margin came from one outlier, where individualizing patient treatment plans through margin adaptation based on biological models, might yield higher quality treatments.

A commercial electron Monte Carlo (eMC) dose calculation algorithm has become available in Eclipse treatment planning system. The purpose of this work was to evaluate the eMC algorithm and investigate the clinical implementation of this system. The beam modeling of the eMC algorithm was performed for beam energies of 6, 9, 12, 16, and 20 MeV for a Varian Trilogy and all available applicator sizes in the Eclipse treatment planning system. The accuracy of the eMC algorithm was evaluated in a homogeneous water phantom, solid water phantoms containing lung and bone materials, and an anthropomorphic phantom. In addition, dose calculation accuracy was compared between pencil beam (PB) and eMC algorithms in the same treatment planning system for heterogeneous phantoms. The overall agreement between eMC calculations and measurements was within 3%/2 mm, while the PB algorithm had large errors (up to 25%) in predicting dose distributions in the presence of inhomogeneities such as bone and lung. The clinical implementation of the eMC algorithm was investigated by performing treatment planning for 15 patients with lesions in the head and neck, breast, chest wall, and sternum. The dose distributions were calculated using PB and eMC algorithms with no smoothing and all three levels of 3D Gaussian smoothing for comparison. Based on a routine electron beam therapy prescription method, the number of eMC calculated monitor units (MUs) was found to increase with increased 3D Gaussian smoothing levels. 3D Gaussian smoothing greatly improved the visual usability of dose distributions and produced better target coverage. Differences of calculated MUs and dose distributions between eMC and PB algorithms could be significant when oblique beam incidence, surface irregularities, and heterogeneous tissues were present in the treatment plans. In our patient cases, monitor unit differences of up to 7% were observed between PB and eMC algorithms. Monitor unit calculations were also preformed based on point-dose prescription. The eMC algorithm calculation was characterized by deeper penetration in the low-density regions, such as lung and air cavities. As a result, the mean dose in the low-density regions was underestimated using PB algorithm. The eMC computation time ranged from 5 min to 66 min on a single 2.66 GHz desktop, which is comparable with PB algorithm calculation time for the same resolution level.

The direct dose mapping (DDM) and energy/mass transfer (EMT) mapping are two essential algorithms for accumulating the dose from different anatomic phases to the reference phase when there is organ motion or tumor/tissue deformation during the delivery of radiation therapy. DDM is based on interpolation of the dose values from one dose grid to another and thus lacks rigor in defining the dose when there are multiple dose values mapped to one dose voxel in the reference phase due to tissue/tumor deformation. On the other hand, EMT counts the total energy and mass transferred to each voxel in the reference phase and calculates the dose by dividing the energy by mass. Therefore it is based on fundamentally sound physics principles. In this study, we implemented the two algorithms and integrated them within the Eclipse treatment planning system. We then compared the clinical dosimetric difference between the two algorithms for ten lung cancer patients receiving stereotactic radiosurgery treatment, by accumulating the delivered dose to the end-of-exhale (EE) phase. Specifically, the respiratory period was divided into ten phases and the dose to each phase was calculated and mapped to the EE phase and then accumulated. The displacement vector field generated by Demons-based registration of the source and reference images was used to transfer the dose and energy. The DDM and EMT algorithms produced noticeably different cumulative dose in the regions with sharp mass density variations and/or high dose gradients. For the planning target volume (PTV) and internal target volume (ITV) minimum dose, the difference was up to 11% and 4% respectively. This suggests that DDM might not be adequate for obtaining an accurate dose distribution of the cumulative plan, instead, EMT should be considered.

The recently released Novalis TX linac platform provides various image guided localization methods including a stereoscopic X-ray imaging technique (ExacTrac) and a volumetric cone beam computed tomography (CBCT) imaging technique. The ExacTrac combined with the robotic six dimensional (6D) couch provides fast and accurate patient setup based on bony structures and offers “snap shot” imaging at any point during the treatment to detect patient motion. The CBCT offers a three dimensional (3D), volumetric image of the patient's setup with visualization of anatomic structures. However, each imaging system has a separate isocenter, which may not coincide with each other or with the linac isocenter. The aim of this paper was to compare the localization accuracy between Exactrac and CBCT for single fraction spine radiosurgery treatments. The study was performed for both phantom and patients (96 clinical treatments of 57 patients). The discrepancies between the isocenter between the ExacTrac and CBCT in four dimensions (three translations and one rotation) were recorded and statistically analyzed using two-tailed t-test.

Image-guided adaptive radiotherapy requires deformable image registration to map radiation dose back and forth between images. The purpose of this study is to develop a novel method to improve the accuracy of an intensity-based image registration algorithm in low-contrast regions. A computational framework has been developed in this study to improve the quality of the 'demons' registration. For each voxel in the registration's target image, the standard deviation of image intensity in a neighborhood of this voxel was calculated. A mask for high-contrast regions was generated based on their standard deviations. In the masked regions, a tetrahedral mesh was refined recursively so that a sufficient number of tetrahedral nodes in these regions can be selected as driving nodes. An elastic system driven by the displacements of the selected nodes was formulated using a finite element method (FEM) and implemented on the refined mesh. The displacements of these driving nodes were generated with the 'demons' algorithm. The solution of the system was derived using a conjugated gradient method, and interpolated to generate a displacement vector field for the registered images. The FEM correction method was compared with the 'demons' algorithm on the computed tomography (CT) images of lung and prostate patients. The performance of the FEM correction relating to the 'demons' registration was analyzed based on the physical property of their deformation maps, and quantitatively evaluated through a benchmark model developed specifically for this study. Compared to the benchmark model, the 'demons' registration has the maximum error of 1.2 cm, which can be corrected by the FEM to 0.4 cm, and the average error of the 'demons' registration is reduced from 0.17 to 0.11 cm. For the CT images of lung and prostate patients, the deformation maps generated by the 'demons' algorithm were found unrealistic at several places. In these places, the displacement differences between the 'demons' registrations and their FEM corrections were found in the range of 0.4 and 1.1 cm. The mesh refinement and FEM simulation were implemented in a single thread application which requires about 45 min of computation time on a 2.6 GHz computer. This study has demonstrated that the FEM can be integrated with intensity-based image registration algorithms to improve their registration accuracy, especially in low-contrast regions.

Purpose: It is essential for radiation oncology departments to have comprehensive patient safety and quality programs. Two years ago we undertook a systematic review of our safety/QA program. Existing policies were updated and new policies created where necessary. One crucial component of any safety/QA program is continually updating it based on current information, the ‘check’ and ‘act’ portions of the Deming Cycle. We accomplished this with a transparent variance reporting system and a safety/QA committee reviewing and acting on reported variances. Methods: With 5 radiation oncology centers in our institution, we needed to devise a system that would allow anyone to report a variance and provide our QA committee the ability to review variances system‐wide. We developed the system using web‐based tools. The system allows individuals to report variances, anonymously or named, specify the nature of the variance and indicate the tools used to identify the variance. Results: In 2011, 285 variances were reported, 102 were reported by physicists, 86 anonymously, 71 by therapists and 26 by dosimetrists. We realized the need to develop clear classifications for variances. We added a high priority category, defined as variances which resulted in or had the potential to result in harm to a patient or when a policy is purposely overridden. Of the 285 variances reported, 5 were high priority. We created a process variance category, defined as variances where a specific clinical process is not followed. Of the 285 reported variances 155 were process variances. Conclusions: Reporting of variances through a centralized database is central toward developing a robust patient safety/quality assurance program. Anonymous reporting fosters a non‐punitive environment, and promotes the ‘safety culture’. The goal of such a system is to review trends in clinical processes and ultimately to improve safety/quality by reducing variances associated with these processes.

The cone-beam computed tomography (CBCT) imaging modality is an integral component of image-guided adaptive radiation therapy (IGART), which uses patient-specific dynamic/temporal information for potential treatment plan modification. In this study, an offline process for the integral component IGART framework has been implemented that consists of deformable image registration (DIR) and its validation, dose reconstruction, dose accumulation and dose verification. This study compares the differences between planned and estimated delivered doses under an IGART framework of five patients undergoing prostate cancer radiation therapy. The dose calculation accuracy on CBCT was verified by measurements made in a Rando pelvic phantom. The accuracy of DIR on patient image sets was evaluated in three ways: landmark matching with fiducial markers, visual image evaluation and unbalanced energy (UE); UE has been previously demonstrated to be a feasible method for the validation of DIR accuracy at a voxel level. The dose calculated on each CBCT image set was reconstructed and accumulated over all fractions to reflect the 'actual dose' delivered to the patient. The deformably accumulated (delivered) plans were then compared to the original (static) plans to evaluate tumor and normal tissue dose discrepancies. The results support the utility of adaptive planning, which can be used to fully elucidate the dosimetric impact based on the simulated delivered dose to achieve the desired tumor control and normal tissue sparing, which may be of particular importance in the context of hypofractionated radiotherapy regimens.

PURPOSE:To compare localization accuracies between an ExacTrac and cone beam computed tomography (CBCT) systems for single fraction spine adiosurgery. The work also aimed to evaluate the inherent systematic deviation of both ExacTrac and CBCT systems to achieve highly accurate localization in the spine radiosurgery. METHODS:ExacTrac and CBCT imaging systems were evaluated using the linac isocenter as the mutual reference point. First, a BB was placed in an anthropomorphic pelvic phantom. The phantom was localized with both imaging systems and the procedure was repeated 12 times. These results were used to devise a localization protocol using both imaging systems in spine radiosurgery, and employed for 51 patients (81 isocenters) prescribed for single fraction treatment. The displacement discrepancy between the isocenter and two systems were quantified in four dimensions (three translations, one rotation). A Student's two-tailed t-test was used to test for significant differences between the two imaging systems. RESULTS:The phantom study showed 1.4±0.5, 0.6±0.5, and 0.1±0.5 mm differences between the two imaging systems in the anterior/posterior (A/P), superior/inferior (S/I) and left/right (L/R) directions, respectively. The angular difference was minimal along all three axes. The patient study revealed similar isocenter discrepancies between ExacTrac and CBCT of 1.1 ± 0.7 mm, 1.0±0.9 mm, and 0.2±0.9 mm in the A/P, S/I, and L/R directions, respectively, with the A/P and S/I directions showing statistical significance ((t(80) = 13.5 and 7.6 respectively, p = 0.000). The couch yaw discrepancy was 0 ± 0.3°. Overall, 1 mm systematic differences were observed in the A/P and S/I directions between ExacTrac and CBCT localization systems, both in phantom and patient. A procedure was developed to mitigate this systematic discrepancy. CONCLUSIONS:These findings have justified our patient localization tolerance levels of 2 mm translation and 1 degree rotation for spine SRS treatment.