Medical physics external beam plan review: What contributes to the variability?

PURPOSE: In this article we report on the results of a survey of physics plan review practices conducted by the Cancer Care Ontario Communities of Practice and the variations in practice between and within centers. METHODS: The medical physicists at each center worked together to complete the survey and submit a single response for that center. A 4-point Likert scale, used to report the variation in practice at each center, was quantified into two parameters: "Intra-center variation", the distribution of responses within the center, and "Variation between centers", the difference between the center's response and the provincial mean. These metrics were correlated with center characteristics to identify factors that impacted on variations in practice. RESULTS: Bolus and heterogeneity correction were the only two items checked by all physicists in all centers. In more than half of the centers, image registration and DVH binning are not likely checked by physics. A significant difference in the variation between centers is observed for centers that used a single vendor's products. Centers that used an official checklist indicated higher levels and a wider range of Intra-center variation. Higher workload did not affect the variation in checking patterns between physicists in the same center. CONCLUSIONS: The effect of a center's resources on their checking practice suggest that local environment and workflow be accounted for when implementing TG275 guidelines. The observation that standardized checklists did not reduce checking variability point to the importance of following the checklist development guidelines in MPPG4 to avoid ineffective checklists.

Determine the therapeutic role of radiotherapy in administrative data: a data mining approach.

BACKGROUND: Clinical data gathered for administrative purposes often lack sufficient information to separate the records of radiotherapy given for palliation from those given for cure. An absence, incompleteness, or inaccuracy of such information could hinder or bias the study of the utilization and outcome of radiotherapy. This study has three specific purposes: 1) develop a method to determine the therapeutic role of radiotherapy (TRR); 2) assess the accuracy of the method; 3) report the quality of the information on treatment "intent" recorded in the clinical data in Ontario, Canada. A general purpose is to use this study as a prototype to demonstrate and test a method to assess the quality of administrative data. METHODS: This is a population based retrospective study. A random sample was drawn from the treatment records with "intent" assigned in treating hospitals. A decision tree is grown using treatment parameters as predictors and "intent" as outcome variable to classify the treatments into curative or palliative. The tree classifier was applied to the entire dataset, and the classification results were compared with those identified by "intent". A manual audit was conducted to assess the accuracy of the classification. RESULTS: The following parameters predicted the TRR, from the strongest to the weakest: radiation dose per fraction, treated body-region, disease site, and time of treatment. When applied to the records of treatments given between 1990 and 2008 in Ontario, Canada, the classification rules correctly classified 96.1% of the records. The quality of the "intent" variable was as follows: 77.5% correctly classified, 3.7% misclassified, and 18.8% did not have an "intent" assigned. CONCLUSIONS: The classification rules derived in this study can be used to determine the TRR when such information is unavailable, incomplete, or inaccurate in administrative data. The study demonstrates that data mining approach can be used to effectively assess and improve the quality of large administrative datasets.

A survey of Canadian medical physicists: software quality assurance of in-house software.

This paper reports on a survey of medical physicists who write and use in-house written software as part of their professional work. The goal of the survey was to assess the extent of in-house software usage and the desire or need for related software quality guidelines. The survey contained eight multiple-choice questions, a ranking question, and seven free text questions. The survey was sent to medical physicists associated with cancer centers across Canada. The respondents to the survey expressed interest in having guidelines to help them in their software-related work, but also demonstrated extensive skills in the area of testing, safety, and communication. These existing skills form a basis for medical physicists to establish a set of software quality guidelines.

The role of Cobalt-60 in modern radiation therapy: Dose delivery and image guidance.

The advances in modern radiation therapy with techniques such as intensity-modulated radiation therapy and image-guided radiation therapy (IMRT and IGRT) have been limited almost exclusively to linear accelerators. Investigations of modern Cobalt-60 (Co-60) radiation delivery in the context of IMRT and IGRT have been very sparse, and have been limited mainly to computer-modeling and treatment-planning exercises. In this paper, we report on the results of experiments using a tomotherapy benchtop apparatus attached to a conventional Co-60 unit. We show that conformal dose delivery is possible and also that Co-60 can be used as the radiation source in megavoltage computed tomography imaging. These results complement our modeling studies of Co-60 tomotherapy and provide a strong motivation for continuing development of modern Cobalt-60 treatment devices.

Temperature increases associated with polymerization of irradiated PAG dosimeters.

Polyacrylamide gel (PAG) dosimeters show considerable promise as three-dimensional dosimeters for the verification of complex dose distributions associated with conformal therapy. However, the potential of PAG dosimeters has not yet been borne out in clinical practice and it is apparent that basic investigations of these dosimeters are still required. The polymerization reactions in PAG dosimeters are exothermic and the heat given off by the reactions may influence polymerization reaction kinetics. We report the results of in situ measurements of local temperature increases in irradiated PAG resulting from heat generated by the radiation-induced exothermic polymerization reactions. Temperature changes proportional to the absorbed dose were observed in the irradiated gels, reaching a maximum of 12 degrees C under high-dose conditions, depending on the thermal boundary conditions. This has practical implications, for example, using small vials of PAG to calibrate large phantoms may not be appropriate since temperature differences during irradiation between the calibration vials and phantom may alter the morphology and quantity of the polymer formed, even when irradiated to the same dose. The inhibition of radiation-induced polymerization associated with low-level oxygen contamination is manifested by a delay in the onset of temperature rise during irradiation. The observed temperature changes are used to estimate the percentage conversion of double bonds from the bis/acrylamide monomers by polymerization reactions.