Application of repeat image analysis to radiation therapy imaging modalities as a quality improvement tool for image guided radiotherapy.

BACKGROUND: Repeat images contribute to excess patient dose and workflow inefficiencies and can be analyzed to identify potential areas for improvement within a program. Although routinely used in diagnostic imaging, repeat image analysis is not widely used in radiation therapy imaging, despite the role of imaging in the delivery of precise radiation treatments. PURPOSE: Repeat image analysis was performed for on-board cone beam CT imagers and CT simulators within a radiation therapy department. Both the rate of repeat images and the reasons for the repeat images were analyzed. METHODS: Data from nine conventional linear accelerators and three CT simulators were analyzed retrospectively over a 5-month period. Repeated images that were not part of the standard of care were considered repeat images. The repeat rate was expressed as the number of repeat scans as percentage of the total number of scans performed. The reasons for the repeats were collected and classified as either patient preparation, patient setup, patient motion, or machine error. These reasons were further classified into sub-categories. RESULTS: The overall repeat rate across the linear accelerators was 3.3%, with a maximum of 5% on any single machine. The repeat rate for the three CT simulators was 1.5%. The most common reasons for repeat images were patient preparation (incorrect bladder or rectal filling) and patient setup or positioning. Greater positioning challenges led to higher repeat rates on units that treat a large number of breast patients, palliative patients, or pediatric patients. CONCLUSIONS: Repeat image analysis can be applied within a radiation therapy department. Establishing baseline repeat rates and analyzing reasons for the repeat images can identify opportunities for improvements in terms of patient dose reduction and workflow efficiency for the program. Periodic repeat image analysis also permits monitoring the program for changes and for comparison against rates at other institutions.

The impact of COVID-19 workflow changes on radiation oncology incident reporting.

BACKGROUND: The Ottawa Hospital's Radiation Oncology program maintains the Incident Learning System (ILS)-a quality assurance program that consists of report submissions of errors and near misses arising from all major domains of radiation. In March 2020, the department adopted workflow changes to optimize patient and provider safety during the COVID-19 pandemic. PURPOSE: In this study, we analyzed the number and type of ILS submissions pre- and postpandemic precautions to assess the impact of COVID-19-related workflow changes. METHODS: ILS data was collected over six one-year time periods between March 2016 and March 2021. For all time periods, the number of ILS submissions were counted. Each ILS submission was analyzed for the specific treatment domain from which it arose and its root cause, explaining the impetus for the error or near miss. RESULTS: Since the onset of COVID-19-related workflow changes, the total number of ILS submissions have reduced by approximately 25%. Similarly, there were 30% fewer ILS submissions per number of treatment courses compared to prepandemic data. There was also an increase in the proportion of "treatment planning" ILS submissions and a 50% reduction in the proportion of "decision to treat" ILS submissions compared to previous years. Root cause analysis revealed there were more incidents attributable to "poor, incomplete, or unclear documentation" during the pandemic year. CONCLUSIONS: COVID-19 workflow changes were associated with fewer ILS submissions, but a relative increase in submissions stemming from poor documentation and communication. It is imperative to analyze ILS submission data, particularly in a changing work environment, as it highlights the potential and realized mistakes that impact patient and staff safety.

Development of a Curriculum for the Implementation of Stereotactic Radiation Therapy Programs in Middle-Income Countries.

PURPOSE: The aim of this work was to develop a curriculum to be used in the implementation of stereotactic radiation therapy programs in middle-income countries. The curriculum needed to be scalable and flexible to be easily adapted to local situations. METHODS: The curriculum was developed through a partnership between multidisciplinary teams from established clinics in both middle-income and high-income countries. The curriculum development followed a nonlinear progression, allowing greater flexibility throughout the process. A blended learning model was used, combining virtual and in-person interactions. RESULTS: The initial training plan was based on a needs assessment provided by the learners and on the experience of the facilitators with stereotactic radiotherapy. The needs assessment was refined during in-person site visits at each institution which highlighted aspects of the training, such as image guidance workflows and technical specifications, that were not previously emphasized in the curriculum. Both teams found that the in-person visits were important for training purposes, but aspects of the curriculum delivery such as treatment planning and patient selection were well suited to virtual platforms. The training addressed all aspects of the stereotactic program, from patient selection to treatment, and included a review of both technical and clinical workflows. CONCLUSION: The inclusion of contributions from both teams ensured that the curriculum covered the required elements of the stereotactic program implementation, met the needs of the learners, and was relevant to local practices. The nonlinear approach to the curriculum development allowed the flexibility to change the focus as the project progressed. The in-person visits were valuable in conducting a thorough needs assessment.

Contamination Resulting From a Broken 125I Seed During a Brachytherapy Procedure.

ABSTRACT: Brachytherapy programs within radiation therapy departments are subject to stringent radiation safety requirements in order to ensure the safety of the staff and patients. Training programs often include brachytherapy-specific radiation safety training modules that address the specific risks associated with radioactive sources, emergency procedures, and regulatory requirements specific to the use of radioisotopes. Unlike other uses of radioactive materials, brachytherapy uses sealed sources and therefore under routine operations does not encounter radioactive contaminants. This article presents an unusual clinical situation in which an 125I brachytherapy seed was damaged during routine clinical workflow, resulting in radioactive contamination within the clinical environment. Decisions made at the time of the incident resulted in contamination that spread beyond the initial location. The incident highlighted a shortcoming of the radiation safety program in preparing staff for the possibility of having to deal with unsealed radioactivity. Brachytherapy programs would be strengthened by including training specific to radioactive contamination in their emergency training to equip staff to respond to unexpected damage to the sealed sources.

Survey of patient-specific quality assurance practice for IMRT and VMAT.

A first-time survey across 15 cancer centers in Ontario, Canada, on the current practice of patient-specific quality assurance (PSQA) for intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) delivery was conducted. The objectives were to assess the current state of PSQA practice, identify areas for potential improvement, and facilitate the continued improvement in standardization, consistency, efficacy, and efficiency of PSQA regionally. The survey asked 40 questions related to PSQA practice for IMRT/VMAT delivery. The questions addressed PSQA policy and procedure, delivery log evaluation, instrumentation, measurement setup and methodology, data analysis and interpretation, documentation, process, failure modes, and feedback. The focus of this survey was on PSQA activities related to routine IMRT/VMAT treatments on conventional linacs, including stereotactic body radiation therapy but excluding stereotactic radiosurgery. The participating centers were instructed to submit answers that reflected the collective view or opinion of their department and represented the most typical process practiced. The results of the survey provided a snapshot of the current state of PSQA practice in Ontario and demonstrated considerable variations in the practice. A large majority (80%) of centers performed PSQA measurements on all VMAT plans. Most employed pseudo-3D array detectors with a true composite (TC) geometry. No standard approach was found for stopping or reducing frequency of measurements. The sole use of delivery log evaluation was not widely implemented, though most centers expressed interest in adopting this technology. All used the Gamma evaluation method for analyzing PSQA measurements; however, no universal approach was reported on how Gamma evaluation and pass determination criteria were determined. All or some PSQA results were reviewed regularly in two-thirds of the centers. Planning related issues were considered the most frequent source for PSQA failures (40%), whereas the most frequent course of action for a failed PSQA was to review the result and decide whether to proceed to treatment.

Improved X-Ray Safety, Quality Control, and Resource Management in Medical Imaging Using QATrack.

INTRODUCTION/BACKGROUND: Management of a quality assurance program in diagnostic imaging involves a variety of machine types, multiple vendors, and a large number of frontline staff who have different specializations. Standardizing tests across multiple platforms in the face of vendor recommendations, regulatory requirements, and professional practice protocols can present challenges to maintain a robust and coherent quality assurance program. The current work presents a unique application of an existing tool that can be used to manage a comprehensive quality assurance program in a diagnostic imaging department. MATERIALS AND METHODS: QATrack+ is an open source, quality assurance platform originally developed for and currently widely used in radiation therapy departments. The use of QATrack+ for quality assurance program management within a large diagnostic imaging department is a novel use of this tool. RESULTS AND DISCUSSION: QATrack+ was successfully implemented in a large, multisite diagnostic imaging department. The progression toward a single platform for the quality assurance program has addressed issues of end of life with previous software packages and has improved the standardization of testing across the institution. The configuration of the software has enabled frontline staff to be directly engaged in the quality control (QC) program, improving the efficiency of resource allocation for QC and promoting a strong safety culture and commitment to quality. Trending tools within QATrack+ allow for simplified review of tests and enable the early identification of potential failures. CONCLUSION: Originally developed for radiation therapy programs, QATrack+ is well suited to applications within diagnostic imaging. It is versatile and is easily adapted to the individual needs of a department for activities ranging from quality control testing, scheduling, test review, and data trending. It simplifies the standardization of quality control practices across platforms, thereby facilitating training and promoting involvement in the quality assurance program by all staff.

Streamlining Regulatory Activities Within Radiation Therapy Departments Using QATrack.

Radiation therapy departments are faced with the challenge of tracking numerous quality control tests as well as monitoring service events affecting radiation therapy treatment units. Service events, in particular, pose a challenge since the clinic must be able to provide evidence to the regulatory body that both the service work and any required follow-up tests were recorded and authorized by the appropriate staff. This article presents an integrated approach to tracking quality control tests and service event logs using QATrack+. The newly developed version of this quality assurance software integrates quality control tracking with the service event log, allowing a direct link between a service event and any initiating routine tests or follow-up tests that are performed. This improves the ability of a licensee to ensure compliance with regulations and permits a simple platform from which to access all machine equipment tests and service events. Furthermore, this improves the ability of a department to assess the service record of equipment and to identify trends in failure modes.

Wall correction factors, Pwall, for parallel-plate ionization chambers.

The EGSnrc Monte Carlo user-code CSnrc is used to calculate wall correction factors, Pwall,, for parallel-plate ionization chambers in photon and electron beams. A set of Pwall values, computed at the reference depth in water, is presented for several commonly used parallel-plate chambers. These values differ from the standard assumption of unity used by dosimetry protocols by up to 1.7% for clinical electron beams. Calculations also show that Pwall is strongly dependent on the depth of measurement and can vary by as much as 6% for a 6 MeV beam in moving from a depth of dref to a depth of R50. In photon beams, where there is limited information available regarding Pwall for parallel-plate chambers, CSnrc calculations show Pwall values of up to 2.4% at the reference depth over a range of photon energies. The Pwall values for photon beams are in good agreement with previous estimates of the wall correction but have much lower statistical uncertainties and cover a wider range of photon beam energies.

Wall correction factors, Pwall, for thimble ionization chambers.

The EGSnrc Monte Carlo user-code CSnrc is used to calculate wall correction factors, Pwall, for thimble ionization chambers in photon and electron beams. CSnrc calculated values of Pwall give closer agreement with previous experimental results than do the values from the standard formalism used in current dosimetry protocols. A set of Pwall values, computed at the reference depth in water, is presented for several commonly used thimble chambers. These values differ from the commonly used values by up to 0.8% for megavoltage photon beams, particularly for nominal beam energies below 6 MV. The sleeve effect, which is not currently taken into account by the TG-51 dosimetry protocol, is computed to be up to 0.3% and is in some cases larger than the Pwal1 correction itself. In electron beams, where dosimetry protocols assume a wall correction of unity, CSnrc calculations show Pwall values of up to 0.6% at the reference depth, depending on the wall material. Pwall is shown to be sensitive to the depth of measurement, varying by 2.5% for a graphite-walled cylindrical Farmer-like chamber between a depth of 0.5 cm and R50 in a 6 MeV electron beam.

CSnrc: correlated sampling Monte Carlo calculations using EGSnrc.

CSnrc, a new user-code for the EGSnrc Monte Carlo system is described. This user-code improves the efficiency when calculating ratios of doses from similar geometries. It uses a correlated sampling variance reduction technique. CSnrc is developed from an existing EGSnrc user-code CAVRZnrc and improves upon the correlated sampling algorithm used in an earlier version of the code written for the EGS4 Monte Carlo system. Improvements over the EGS4 version of the algorithm avoid repetition of sections of particle tracks. The new code includes a rectangular phantom geometry not available in other EGSnrc cylindrical codes. Comparison to CAVRZnrc shows gains in efficiency of up to a factor of 64 for a variety of test geometries when computing the ratio of doses to the cavity for two geometries. CSnrc is well suited to in-phantom calculations and is used to calculate the central electrode correction factor Pcel in high-energy photon and electron beams. Current dosimetry protocols base the value of Pcel on earlier Monte Carlo calculations. The current CSnrc calculations achieve 0.02% statistical uncertainties on Pcel, much lower than those previously published. The current values of Pcel compare well with the values used in dosimetry protocols for photon beams. For electrons beams, CSnrc calculations are reported at the reference depth used in recent protocols and show up to a 0.2% correction for a graphite electrode, a correction currently ignored by dosimetry protocols. The calculations show that for a 1 mm diameter aluminum central electrode, the correction factor differs somewhat from the values used in both the IAEA TRS-398 code of practice and the AAPM's TG-51 protocol.

An EGSnrc investigation of cavity theory for ion chambers measuring air kerma.

The EGSnrc system is used to compare the response of an aluminum-walled thimble chamber to that of a graphite-walled thimble chamber for a 60Co beam. When compared to previous experimental results, the EGSnrc values of the ratios of chamber response differ by as much as 0.7% from the experiment. However, it is shown that this difference can be more than accounted for by switching from using the graphite mean excitation energy of 78 eV used in dosimetry protocols to the value of 86.8 eV suggested by more recent stopping-power experiments. This suggests that the uncertainty analysis of Monte Carlo results must be done more carefully, by taking into account uncertainties in the underlying basic data such as the electron and photon cross sections. In comparison to Spencer-Attix cavity theory for a thick-walled ion chamber, the Monte Carlo calculated values of the chamber response differ from the expected ones by 0.15% and 0.01% for the graphite and aluminum chambers, respectively, which are comparable to previously reported values for the Spencer-Attix correction factors. EGSnrc is also used to investigate the effect on the chamber response of thin dag layers on the inside of the aluminum wall. There is good agreement between the calculated and measured changes in chamber response versus the thickness of the dag. The results are compared to the predictions of the Almond-Svensson extension of cavity theory and show that the theory does not correctly predict the chamber response in the presence of thin dag layers. This finding is in agreement with previously reported experimental results. It is demonstrated that the values of alpha, the fraction of ionizations in the gas arising from electrons generated in the dag layer, used in the theory, are not the source of the disagreement.