Fong de Los Santos, Luis E

AbstractPurposeTo study the feasibility of using the Integral Quality Monitoring (IQM) system for routine quality assurance (QA) of photon beams.MethodsThe IQM system is a commercially available dose delivery verification tool, which consists of a spatially sensitive large area transmission ion chamber, mounted on the Linac collimator, and a calculation algorithm to predict the signals in response to radiation beams. By comparing the measured and predicted signals the system verifies the accuracy of beam delivery. The ion chamber unit is a battery powered system including a dual‐electrometer, temperature and pressure sensors, and inclinometers. The feasibility of using the IQM system for routine QA tests was investigated by measuring constancy values of beam parameters, with specially designed tests fields, and comparing them with those determined by a conventional system.ResultsThe sensitivity of the beam output constancy measurements by the IQM system was found to agree with those measured by a Farmer type ion chamber placed in water phantoms to within 0.1% for typical daily output variation of ± 0.5% and ± 1%. The beam symmetry was measured with a 4 cm × 4 cm aperture at multiple off‐axis distances and was found to have a highly linear relationship with those measured in a water phantom scan for intentionally introduced asymmetry between ‐3% and +3%. The beam flatness was measured with a two‐field ratio method and was found to be linearly correlated with those measured by water phantom scan. The dosimetric equivalent of a picket fence test performed by the IQM system can serve as a constancy check of the multileaf collimator (MLC) bank positioning test.ConclusionsThe IQM system has been investigated for constancy measurements of various beam parameters for photon beams. The results suggest that the system can be used for most of the routine QA tests effectively and efficiently.

AbstractBackgroundAAPM Task Group (TG) 275 was charged with developing practical, evidence‐based recommendations for physics plan and chart review clinical processes for radiation therapy. As part of this charge, and to characterize practices and clinical processes, a survey of the medical physics community was developed and conducted. Detailed analyses and trends based on the survey that exceeded TG report length constraints are presented herein.AimsThe design, development, and detailed results of the TG‐ 275 survey as well as statistical analysis and trends are described in detail. This is complementary material to the TG 275 report.Methods and materialsThe survey consisted of 100 multiple‐choice questions divided into four main sections: 1) Demographics, 2) Initial Plan Check, 3) On‐Treatment, and 4) End‐of‐Treatment Chart Check. The survey was released to all AAPM members who self‐reported working in the radiation oncology field, and it was kept open for 7 weeks. Results were summarized using descriptive statistics. To study practice differences, tests of association were performed using data grouped by four demographic questions: 1) Institution Type, 2) Average number of patients treated daily, 3) Radiation Oncology Electronic Medical Record, and 4) Perceived Culture of Safety.ResultsThe survey captured 1370 non‐duplicate entries from the United States and Canada. Differences across practices were grouped and presented based on Process‐Based and Check‐Specific questions. A risk‐based summary was created to show differences amongst the four demographic questions for checks associated with the highest risk failure modes identified by TG‐275.ConclusionThe TG‐275 survey captured a baseline of practices on initial plan, on‐treatment, and end‐of‐treatment checks across a wide variety of clinics and institutions. The results of test of association showed practice heterogeneities as a function of demographic characteristics. Survey data were successfully used to inform TG‐275 recommendations.

AbstractThe American Association of Physicists in Medicine (AAPM) is a nonprofit professional society whose primary purposes are to advance the science, education, and professional practice of medical physics. The AAPM has more than 8000 members and is the principal organization of medical physicists in the US. The AAPM will periodically define new practice guidelines for medical physics practice to help advance the science of medical physics and to improve the quality of service to patients throughout the US. Existing medical physics practice guidelines will be reviewed for the purpose of revision or renewal, as appropriate, on their fifth anniversary or sooner. Each medical physics practice guideline represents a policy statement by the AAPM, has undergone a thorough consensus process in which it has been subjected to extensive review, and requires the approval of the Professional Council. The medical physics practice guidelines recognize that the safe and effective use of diagnostic and therapeutic radiology requires specific training, skills, and techniques, as described in each document. Reproduction or modification of the published practice guidelines and technical standards by those entities not providing these services is not authorized. The following terms are used in the AAPM practice guidelines: Must and must not: Used to indicate that adherence to the recommendation is considered necessary to conform to this practice guideline. While must is the term to be used in the guidelines, if an entity that adopts the guideline has shall as the preferred term, the AAPM considers that must and shall have the same meaning. Should and should not: Used to indicate a prudent practice to which exceptions may occasionally be made in appropriate circumstances.

AbstractPurposeTo investigate the dependency of dose‐volume histogram (DVH) behavior and precision on underlying discretization using shapes and dose distributions with known analytical DVHs for five commercial DVH calculators.MethodsDVHs and summary metrics were extracted from all five systems using synthetic cone and cylinder objects for which the true volume and DVH curves were known. Trends in the curves and metrics were explored by varying the underlying voxelization of the CT image, structure set, and dose grid as well by varying the geometry of the structure and direction of a linear dose gradient. Using synthetic structures allowed for comparison with ground truth DVH curves to assess their accuracy while an algorithm was additionally developed to assess the precision of each system. The precision was calculated with a novel algorithm that treats any “stair step” behavior in a DVH curve as an uncertainty band and calculates the width, characterized as a percent difference, of the band for various DVH metrics. The underlying voxelization was additionally changed and DVHs were extracted for two clinical examples. The details of how each system calculated DVHs were also investigated and tendencies in the calculated curves, metrics, and precision were related to choices made in the calculation methodology.ResultsCalculation methodology differences that had a noticeable impact on the DVH curves and summary metrics include supersampling beyond the input grids and interpretation of the superior and inferior ends of the structures. Among the systems studied, the median precision ranged from 0.902% to 3.22%, and interquartile ranges varied from 1.09% to 3.91%.ConclusionsCommercial dose‐evaluation solutions can calculate different DVH curves, structure volume measures, and dose statistics for the same input data due to differences in their calculation methodologies. This study highlights the importance of understanding and investigating the DVH calculation when considering a new clinical system and when using more than one system for data transfer.

AbstractWhile most Radiation Oncology clinics have adopted electronic charting in one form or another, no consensus document exists that provides guidelines for safe and effective use of the Radiation Oncology electronic medical records (RO‐EMR). Task Group 262 was formed to provide these guidelines as well as to provide recommendations to vendors for improving electronic charting functionality in future. Guidelines are provided in the following areas: Implementation and training for the RO‐EMR, acceptance testing and quality assurance (QA) of the RO‐EMR, use of the RO‐EMR as an information repository, use of the RO‐EMR as a workflow manager, electronic charting for brachytherapy and nonstandard treatments, and information technology (IT) considerations associated with the RO‐EMR. The report was based on a literature search by the task group, an extensive survey of task group members on their respective RO‐EMR practices, an AAPM membership survey on electronic charting, as well as group consensus.

PurposeThe purpose of this study was to demonstrate an objective quality control framework for the image review process.Methods and materialsA total of 927 cone‐beam computed tomography (CBCT) registrations were retrospectively analyzed for 33 bilateral head and neck cancer patients who received definitive radiotherapy. Two registration tracking volumes (RTVs) — cervical spine (C‐spine) and mandible — were defined, within which a similarity metric was calculated and used as a registration quality tracking metric over the course of treatment. First, sensitivity to large misregistrations was analyzed for normalized cross‐correlation (NCC) and mutual information (MI) in the context of statistical analysis. The distribution of metrics was obtained for displacements that varied according to a normal distribution with standard deviation of σ = 2 mm, and the detectability of displacements greater than 5 mm was investigated. Then, similarity metric control charts were created using a statistical process control (SPC) framework to objectively monitor the image registration and review process. Patient‐specific control charts were created using NCC values from the first five fractions to set a patient‐specific process capability limit. Population control charts were created using the average of the first five NCC values for all patients in the study. For each patient, the similarity metrics were calculated as a function of unidirectional translation, referred to as the effective displacement. Patient‐specific action limits corresponding to 5 mm effective displacements were defined. Furthermore, effective displacements of the ten registrations with the lowest similarity metrics were compared with a three dimensional (3DoF) couch displacement required to align the anatomical landmarks.ResultsNormalized cross‐correlation identified suboptimal registrations more effectively than MI within the framework of SPC. Deviations greater than 5 mm were detected at 2.8σ and 2.1σ from the mean for NCC and MI, respectively. Patient‐specific control charts using NCC evaluated daily variation and identified statistically significant deviations. This study also showed that subjective evaluations of the images were not always consistent. Population control charts identified a patient whose tracking metrics were significantly lower than those of other patients. The patient‐specific action limits identified registrations that warranted immediate evaluation by an expert. When effective displacements in the anterior–posterior direction were compared to 3DoF couch displacements, the agreement was ±1 mm for seven of 10 patients for both C‐spine and mandible RTVs.ConclusionsQualitative review alone of IGRT images can result in inconsistent feedback to the IGRT process. Registration tracking using NCC objectively identifies statistically significant deviations. When used in conjunction with the current image review process, this tool can assist in improving the safety and consistency of the IGRT process.