An international review of patient safety measures in radiotherapy practice

Development and psychometric validation of a patient safety assessment tool in German Radiation Oncology: the PaSaGeRO Study protocol

INTRODUCTION

Ensuring patient safety in radiation oncology is crucial for delivering high-quality healthcare. Patient safety indicators (PSIs) provide a mechanism for identifying, quantifying and evaluating risks and the effectiveness of safety measures. However, there is currently no specialised set of PSIs tailored for radiation oncology in Germany. This study seeks to: (1) create PSIs specifically designed for radiation oncology settings, (2) develop and psychometrically validate an instrument for assessing safety in German radiation oncology facilities and (3) evaluate the feasibility of implementing this instrument in routine clinical practice. The finalised questionnaire will serve as a self-assessment instrument for radiation oncology departments, aiding them in evaluating their efficacy in ensuring patient safety, prioritising safety interventions and tracking performance over time.

METHODS AND ANALYSIS

We are undertaking a 3-year, mixed methods study to address our objectives. For the identification of PSIs, we will conduct a comprehensive review on the PubMed database, along with reviewing national and international guidelines and recommendations. To refine the initial set of indicators, we will consult with experts, including physicians, medical physicists, nurses, administrators and radiation therapists through focus groups. We will employ a Delphi study for the final consensus and selection of indicators. Additionally, the perspectives of patients will be incorporated by formation of a project patient's committee which meets throughout the project phases. We will reformulate the identified PSIs into questionnaire items. The questionnaire's clarity and comprehensibility will be validated through cognitive interviews, followed by psychometric testing in a pilot group of over 150 participants from German radiation oncology departments. The final version of the questionnaire will then be implemented in routine healthcare settings and we will interview individual users about their experiences with the questionnaire in semistructured interviews. We will convene a subsequent expert workshop to discuss the study results and explore avenues for the questionnaire's broader implementation. The finalised questionnaire will be made accessible via a web app. We hereby present the study potocol as a pre-results report.

ETHICS AND DISSEMINATION

Ethical approval for this study was granted by the Hamburg Ethics Committee (Approval Number: 2023-101018-BO-ff). This trial is registered by the ARO (Arbeitsgemeinschaft Radioonkologie /working group for radiation oncology of the German Cancer Society), protocol number 2023-03 and in the German register for clinical trials with the number DRKS00034690. Study results will be published in conference papers and talks as well as journal papers with focus on open access journals. The results will be also disseminated during the implementation workshop in phase III, which will involve a diverse group of stakeholders.

TRIAL REGISTRATION NUMBER

DRKS00034690.

Re-evaluation of the prospective risk analysis for artificial-intelligence driven cone beam computed tomography-based online adaptive radiotherapy after one year of clinical experience

Cone-beam computed tomography (CBCT)-based online adaptation is increasingly being introduced into many clinics. Upon implementation of a new treatment technique, a prospective risk analysis is required and enhances workflow safety. We conducted a risk analysis using Failure Mode and Effects Analysis (FMEA) upon the introduction of an online adaptive treatment programme (Wegener et al., Z Med Phys. 2022). A prospective risk analysis, lacking in-depth clinical experience with a treatment modality or treatment machine, relies on imagination and estimates of the occurrence of different failure modes. Therefore, we systematically documented all irregularities during the first year of online adaptation, namely all cases in which quality assurance detected undesired states potentially leading to negative consequences. Additionally, the quality of automatic contouring was evaluated. Based on those quantitative data, the risk analysis was updated by an interprofessional team. Furthermore, a hypothetical radiation therapist-only workflow during adaptive sessions was included in the prospective analysis, as opposed to the involvement of an interprofessional team performing each adaptive treatment. A total of 126 irregularities were recorded during the first year. During that time period, many of the previously anticipated failure modes (almost) occurred, indicating that the initial prospective risk analysis captured relevant failure modes. However, some scenarios were not anticipated, emphasizing the limits of a prospective risk analysis. This underscores the need for regular updates to the risk analysis. The most critical failure modes are presented together with possible mitigation strategies. It was further noted that almost half of the reported irregularities applied to the non-adaptive treatments on this treatment machine, primarily due to a manual plan import step implemented in the institution's workflow.

ARCHERY: a prospective observational study of artificial intelligence-based radiotherapy treatment planning for cervical, head and neck and prostate cancer - study protocol

INTRODUCTION

Fifty per cent of patients with cancer require radiotherapy during their disease course, however, only 10%-40% of patients in low-income and middle-income countries (LMICs) have access to it. A shortfall in specialised workforce has been identified as the most significant barrier to expanding radiotherapy capacity. Artificial intelligence (AI)-based software has been developed to automate both the delineation of anatomical target structures and the definition of the position, size and shape of the radiation beams. Proposed advantages include improved treatment accuracy, as well as a reduction in the time (from weeks to minutes) and human resources needed to deliver radiotherapy.

METHODS

ARCHERY is a non-randomised prospective study to evaluate the quality and economic impact of AI-based automated radiotherapy treatment planning for cervical, head and neck, and prostate cancers, which are endemic in LMICs, and for which radiotherapy is the primary curative treatment modality. The sample size of 990 patients (330 for each cancer type) has been calculated based on an estimated 95% treatment plan acceptability rate. Time and cost savings will be analysed as secondary outcome measures using the time-driven activity-based costing model. The 48-month study will take place in six public sector cancer hospitals in India (n=2), Jordan (n=1), Malaysia (n=1) and South Africa (n=2) to support implementation of the software in LMICs.

ETHICS AND DISSEMINATION

The study has received ethical approval from University College London (UCL) and each of the six study sites. If the study objectives are met, the AI-based software will be offered as a not-for-profit web service to public sector state hospitals in LMICs to support expansion of high quality radiotherapy capacity, improving access to and affordability of this key modality of cancer cure and control. Public and policy engagement plans will involve patients as key partners.

Feasibility study of a scintillation sheet-based detector for fluence monitoring during external photon beam radiotherapy

PURPOSE

This study evaluated the properties of a scintillation sheet-based dosimetry system for beam monitoring with high spatial resolution, including the effects of this system on the treatment beam. The dosimetric characteristics and feasibility of this system for clinical use were also evaluated.

METHODS

The effects of the dosimetry system on the beam were evaluated by measuring the percentage depth doses, dose profiles, and transmission factors. Fifteen treatment plans were created, and the influence of the dosimetry system on these clinical treatment plans was evaluated. The performance of the system was assessed by determining signal linearity, dose rate dependence, and reproducibility. The feasibility of the system for clinical use was evaluated by comparing intensity distributions with reference intensity distributions verified by quality assurance.

RESULTS

The spatial resolution of the dosimetry system was found to be 0.43 mm/pixel when projected to the isocenter plane. The dosimetry system attenuated the intensity of 6 MV beams by about 1.1%, without affecting the percentage depth doses and dose profiles. The response of the dosimetry system was linear, independent of the dose rate used in the clinic, and reproducible. Comparison of intensity distributions of evaluation treatment fields with reference intensity distributions showed that the 1%/1 mm average gamma passing rate was 99.6%.

CONCLUSIONS

The dosimetry system did not significantly alter the beam characteristics, indicating that the system could be implemented by using only a transmission factor. The dosimetry system is clinically suitable for monitoring treatment beam delivery with higher spatial resolution than other transmission detectors.

Safety in radiation oncology (SAFRON): Learning about incident causes and safety barriers in external beam radiotherapy

PURPOSE

Safety in Radiation Oncology (SAFRON) is a reporting and learning system on radiotherapy and radionuclide therapy incidents and near misses. The primary aim of this paper is to examine whether any discernible patterns exist in the causes of reported incidents and safety barriers within the SAFRON system concerning external beam radiotherapy.

METHODS AND MATERIALS

This study focuses on external beam radiotherapy incidents, reviewing 1685 reports since the inception of SAFRON until December 2021. Reports that did not identify causes of incidents and safety barriers were excluded from the final study population.

RESULTS

Simple two-dimensional radiotherapy or electron beam therapy were represented by 97 reports, three-dimensional conformal radiotherapy by 39 reports, modulated arc therapy by 12 reports, intensity modulated radiation therapy by 11 reports, stereotactic radiosurgery by 4 reports, and radiotherapy with protons or other particles by 1 report, while for 92 of them, no information on treatment method had been provided. Most of the reported incidents were minor incidents and were discovered by the radiation therapist. Inadequate direction/information in staff communication was the most frequently reported cause of incident, and regular independent chart check was the most common safety barrier.

CONCLUSIONS

The results indicate that the majority of incidents were reported by radiation therapists, and the majority of these incidents were classified as minor. Communication problems and failure to follow standards/procedures/practices were the most frequent causes of incidents. Furthermore, regular independent chart checking was the most frequently identified safety barrier.

Risk management patterns in radiation oncology-results of a national survey within the framework of the Patient Safety in German Radiation Oncology (PaSaGeRO) project

PURPOSE

Risk management (RM) is a key component of patient safety in radiation oncology (RO). We investigated current approaches on RM in German RO within the framework of the Patient Safety in German Radiation Oncology (PaSaGeRO) project. Aim was not only to evaluate a status quo of RM purposes but furthermore to discover challenges for sustainable RM that should be addressed in future research and recommendations.

METHODS

An online survey was conducted from June to August 2021, consisting of 18 items on prospective and reactive RM, protagonists of RM, and self-assessment concerning RM. The survey was designed using LimeSurvey and invitations were sent by e‑mail. Answers were requested once per institution.

RESULTS

In all, 48 completed questionnaires from university hospitals, general and non-academic hospitals, and private practices were received and considered for evaluation. Prospective and reactive RM was commonly conducted within interprofessional teams; 88% of all institutions performed prospective risk analyses. Most institutions (71%) reported incidents or near-events using multiple reporting systems. Results were presented to the team in 71% for prospective analyses and 85% for analyses of incidents. Risk conferences take place in 46% of institutions. 42% nominated a manager/committee for RM. Knowledge concerning RM was mostly rated "satisfying" (44%). However, 65% of all institutions require more information about RM by professional societies.

CONCLUSION

Our results revealed heterogeneous patterns of RM in RO departments, although most departments adhered to common recommendations. Identified mismatches between recommendations and implementation of RM provide baseline data for future research and support definition of teaching content.

Development and multi-institutional validation of a convolutional neural network to detect vertebral body mis-alignments in 2D x-ray setup images

BACKGROUND

Misalignment to the incorrect vertebral body remains a rare but serious patient safety risk in image-guided radiotherapy (IGRT).

PURPOSE

Our group has proposed that an automated image-review algorithm be inserted into the IGRT process as an interlock to detect off-by-one vertebral body errors. This study presents the development and multi-institutional validation of a convolutional neural network (CNN)-based approach for such an algorithm using patient image data from a planar stereoscopic x-ray IGRT system.

METHODS

X-rays and digitally reconstructed radiographs (DRRs) were collected from 429 spine radiotherapy patients (1592 treatment fractions) treated at six institutions using a stereoscopic x-ray image guidance system. Clinically-applied, physician approved, alignments were used for true-negative, "no-error" cases. "Off-by-one vertebral body" errors were simulated by translating DRRs along the spinal column using a semi-automated method. A leave-one-institution-out approach was used to estimate model accuracy on data from unseen institutions as follows: All of the images from five of the institutions were used to train a CNN model from scratch using a fixed network architecture and hyper-parameters. The size of this training set ranged from 5700 to 9372 images, depending on exactly which five institutions were contributing data. The training set was randomized and split using a 75/25 split into the final training/ validation sets. X-ray/ DRR image pairs and the associated binary labels of "no-error" or "shift" were used as the model input. Model accuracy was evaluated using images from the sixth institution, which were left out of the training phase entirely. This test set ranged from 180 to 3852 images, again depending on which institution had been left out of the training phase. The trained model was used to classify the images from the test set as either "no-error" or "shifted", and the model predictions were compared to the ground truth labels to assess the model accuracy. This process was repeated until each institution's images had been used as the testing dataset.

RESULTS

When the six models were used to classify unseen image pairs from the institution left out during training, the resulting receiver operating characteristic area under the curve values ranged from 0.976 to 0.998. With the specificity fixed at 99%, the corresponding sensitivities ranged from 61.9% to 99.2% (mean: 77.6%). With the specificity fixed at 95%, sensitivities ranged from 85.5% to 99.8% (mean: 92.9%).

CONCLUSION

This study demonstrated the CNN-based vertebral body misalignment model is robust when applied to previously unseen test data from an outside institution, indicating that this proposed additional safeguard against misalignment is feasible.

Patient safety as a global health priority

Patient safety is a discipline that has arisen in response to the increasing complexity of health care delivery and the associated increase in patient harm. Adverse health care events are a serious problem, causing significant harm to the patient and increasing health care costs. The World Health Organization has identified patient safety as one of the key priorities for world health. The current review presents the historical background that led to the formation of the discipline of patient safety, the determinants of adverse events in medical practice, and the main tools for dealing with them.

Quality Improvement Process with Incident Learning Program Helped Reducing Transcriptional Errors on Telecobalt Due to Mismatched Parameters in Different Generations

Purpose

Higher frequency of transcriptional errors in the radiotherapy electronic charts for patients on telecobalt was noted. We describe the impact of the quality improvement (QI) initiative under the department's incident learning program (ILP).

Materials and Methods

The multidisciplinary quality team under ILP was formed to identify the root cause and introduce methods to reduce (smart goal) the current transcription error rate of 40% to <5% over 12 months. A root cause analysis including a fishbone diagram, Pareto chart, and action prioritization matrix was done to identify key drivers and interventions. Plan-Do-Study-Act (PDSA) Cycle strategy was undertaken. The primary outcome was percentage charts with transcriptional errors per month. The balancing measure was "new errors" due to interventions. All errors were identified and corrected before patient treatment.

Results

The average baseline error rate was 44.14%. The two key drivers identified were education of the workforce involved and mechanical synchronization of various machine parameters. PDSA cycle 1 consisted of an education program and sensitization of the staff, post which the error rates dropped to 5.4% (t-test P = 0.03). Post-PDSA cycle 2 (synchronization of machine parameters), 1, 3, and 6 months and 1 year, the error rates were sustained to 5%, 4%, 3%, and 4% (t-test P > 0.05) with no new additional errors.

Conclusions

With various generations of machines and technologies that are not synchronized, the proneness of transcription errors can be very high which can be identified and corrected with a typical QI process under ILP.

A systems-based operational assessment of external beam radiotherapy

PURPOSE

Advanced technologies have led to improvements in modern radiotherapy over the years. However, adoption of advanced technologies can present challenges to existing clinical operations and negatively impact safety. The purpose of this work is to perform an assessment of modern radiotherapy for the operational objectives of safety, efficiency, and financial viability.

METHODS

This work focuses on external beam radiotherapy (EBRT). The operational assessment included department management, treatment planning, treatment delivery, and associated workflows for three equipment configurations of Ethos, Halcyon, and TrueBeam with the ARIA information system, Eclipse treatment planning, and IDENTIFY surface guidance. Systems-theoretic process analysis (STPA) was used to analyze the related workflows. Control actions, unsafe contexts of those control actions, and associated causal scenarios that can lead to unsafe radiation and non-radiation physical injury (safety objective), reduced treatment capacity (efficiency objective), and costs that exceed budget (financial viability objective) were identified.

RESULTS

The number of control actions (and causal scenarios) were 18 (254), 18 (267), and 20 (267) for the equipment configurations of Halcyon, TrueBeam, and Ethos, respectively. The extent that safety, efficiency, and financial viability were impacted is similar across the different equipment configurations but there were some noteworthy differences related to information transfer and workflow bottlenecks potentially impacting access to care. Seventy five percent of the scenarios across all three configurations were related to safety. Overall, 29% of the scenarios impacted more than one operational objective and 48% were related to human decisions during the process of care. Planned or unplanned process changes were responsible for 8% of the causal scenarios.

CONCLUSIONS

Broad-based clinical improvements may be realized by addressing causal scenarios that impact multiple objectives. Redesigning the roles and responsibilities of the clinical team and some aspects of the radiotherapy workflow may be helpful to fully realize the benefits of advanced technologies. Radiotherapy may benefit from additional tools to improve the consistency between decisions and actions when system or process changes occur. This article is protected by copyright. All rights reserved.

Incident review in radiation oncology

By its very nature, radiation oncology is a complex, multi-profession dynamic modality of cancer treatment. There are multiple steps with many handovers of work and many opportunities for patient safety to be compromised. Patient safety events can manifest as either actual incidents or near miss/close call events. Reporting and learning from these events is key to quality improvement and patient safety. In this paper, we aim to provide an overview of radiation oncology incident reporting and learning systems. We review the importance of the use of a standardized taxonomy and classification that is specific to radiation oncology workflow, the international systems in current use and the current reporting requirements in Australia and New Zealand. Equally important is the culture that exists alongside the incident learning system. A just culture, where support for reporting exists and there is an adaptive responsive environment to learn and improve patient safety. The incident learning and patient safety system requires constant effort to make it a success. We describe potential measures of safety culture and of relative patient safety and recommend their routine use. We offer this review to stimulate the effort towards a binational voluntary incident learning system, a key pillar for the improvement in patient safety in radiation oncology.

How often does it happen? A review of unintended, unnecessary and unavoidable high-dose radiation exposures

High-dose radiation exposures of humans occur every year around the world, and may lead to harmful tissue reactions. This review aims to look at the available information sources that can help answering the question of how often these events occur yearly on a global scale. In the absence of comprehensive databases of global occurrence, publications on radiation accidents in all uses of radiation and on rates of high-dose events in different medical uses of radiation have been reviewed. Most high-dose radiation exposures seem to occur in the medical uses of radiation, reflecting the high number of medical exposures performed. In therapeutic medical uses, radiation doses are purposely often given at levels known to cause deterministic effects, and there is a very narrow range in which the medical practitioner can operate without causing severe unacceptable outcomes. In interventional medical uses, there are scenarios in which the radiation dose given to a patient may reach or exceed a threshold for skin effects, where this radiation dose may be unavoidable, considering all benefits and risks as well as benefits and risks of any alternative procedures. Regardless of if the delivered dose is unintended, unnecessary or unavoidable, there are estimates published of the rates of high-dose events and of radiation-induced tissue injuries occurring in medical uses. If this information is extrapolated to a global scenario, noting the inherent limitations in doing so, it does not seem unreasonable to expect that the global number of radiation-induced injuries every year may be in the order of hundreds, likely mainly arising from medical uses of radiation, and in particular from interventional fluoroscopy procedures and external beam radiotherapy procedures. These procedures are so frequently employed throughout the world that even a very small rate of radiation-induced injuries becomes a substantial number when scaled up to a global level.

Safety culture to improve accidental event reporting in radiotherapy

BACKGROUND AND PURPOSE

The potential for unintended and adverse radiation exposure in radiotherapy (RT) is real and should be studied because RT is a highly complex, multistep process, which requires input from numerous individuals from different areas and steps of the RT workflow. The 'Incident' (I) is an event the consequence of which is not negligible from the point of view of protection or safety. A 'near miss' (NM) is defined as an event that is highly likely to happen but did not occur. The purpose of this work is to show that through systematic reporting and analysis of these adverse events, their occurrence can be reduced.

MATERIALS AND METHODS

Staff were trained to report every type of unintended and adverse radiation exposure and to provide a full description of it.

RESULTS

By 2018, 110 worksheets had been collected, with an average of 6.1 adverse events per year (with 780 patients treated per year, meaning an average incident rate of 0.78%). In 2001-2009, 37 events were registered (13 I and 24 NM), the majority of them were in the decision phase (12/37), while in 2010-2013, there were 42 (1 I and 41 NM) in both the dose-calculation and transfer phase (19/42). In 2014-2018, 31 events (1 I and 30 NM) were equally distributed across the phases of the RT process. In 9/15 cases of I, some checkpoint was introduced.

CONCLUSION

The complexity of the RT workflow is prone to errors, and this must be taken into account by encouraging a safety culture. The aim of this paper is to present the collected incidents and near misses and to show how organization and practice were modified by the acquired knowledge.

An Investigation of Radiation Treatment Learning Opportunities in Relation to the Radiation Oncology Electronic Medical Record: A Single Institution Experience

Purpose

A modern radiation oncology electronic medical record (RO-EMR) system represents a sophisticated human-computer interface with the potential to reduce human driven errors and improve patient safety. As the RO-EMR becomes an integral part of clinical processes, it may be advantageous to analyze learning opportunities (LO) based on their relationship with the RO-EMR. This work reviews one institution's documented LO to: (1) study their relationship with the RO-EMR workflow, (2) identify best opportunities to improve RO-EMR workflow design, and (3) identify current RO-EMR workflow challenges.

Methods and Materials

Internal LO reports for an 11-year contiguous period were categorized by their relationship to the RO-EMR. We also identify the specific components of the RO-EMR used or involved in each LO. Additionally, contributing factor categories from the ASTRO/AAPM sponsored Radiation Oncology Incident Learning System's (RO-ILS) nomenclature was used to characterize LO directly linked to the RO-EMR.

Results

A total of 163 LO from the 11-year period were reviewed and analyzed. Most (77.2%) LO involved the RO-EMR in some way. The majority of the LO were the results of human/manual operations. The most common RO-EMR components involved in the studied LO were documentation related to patient setup, treatment session schedule functionality, RO-EMR used as a communication/note-delivery tool, and issues with treatment accessories. Most of the LO had staff lack of attention and policy not followed as 2 of the highest occurring contributing factors.

Conclusions

We found that the majority of LO were related to RO-EMR workflow processes. The high-risk areas were related to manual data entry or manual treatment execution. An evaluation of LO as a function of their relationship with the RO-EMR allowed for opportunities for improvement. In addition to regular radiation oncology quality improvement review and policy update, automated functions in RO-EMR remain highly desirable.

Patient Safety Culture and Associated Factors Among Health-Care Providers in the University of Gondar Comprehensive Specialized Hospital, Northwest Ethiopia

Introduction

Patient safety is an issue of global concern; however, health-care organizations have lately observed to pay more attention to the importance of establishing a culture of safety. The study aimed to assess the level of patient safety culture and associated factors among health-care providers at the University of Gondar comprehensive specialized hospital, Northwest Ethiopia, 2020.

Methods

A cross-sectional study design supported by the qualitative approach was conducted from March 15 to May 15/2020. A stratified simple sampling technique was used to select 575 study participants. The standardized tool, which measures 12 safety culture dimensions, was used for data collection. Bivariate and multivariable linear regression analyses performed using SPSS version 23. The significance level was obtained at 95% CI and p-value <0.05. For the qualitative part, a semi-structured interview guide with probing was used. Data were analyzed thematically using open code software version 4.02.

Results

The overall level of positive patient safety culture was 45.3% (95% CI: 44.7, 45.9) with a response rate of 92.2%. Factor analysis indicated that female, masters, participation in patient safety program, adverse event report, hospital management encourage reporting event and resource were positively associated with the patient safety culture. Whereas divorced/widowed, midwives, anesthetist, medicine, pediatrics, emergency, outpatient, pharmacy, direct contact with patients, and hospital management blame when medical errors happened were negatively associated. The in-depth interview revealed that teamwork, health-care professionals’ attitude toward patient safety and patient involvement as important factors that influence patient safety culture.

Conclusions and Recommendations

The overall level of positive patient safety culture was low. All variables except age, training, working hour, and working experience were factors significantly associated with the patient safety culture. Health-care policy-makers and managers should consider patient safety culture a top priority, and also create a blame-free environment that promotes event reporting.

Usability testing of radiotherapy systems as a medical device evaluation tool to inform hospital procurement decision-making

PURPOSE

Poor usability designs of radiotherapy systems can contribute to use errors and adverse events. Therefore, we evaluated the usability of two radiotherapy systems through radiation therapists' performance, workload, and experience that can inform hospital procurement decision-making about the selection of appropriate radiotherapy system for radiation therapist use.

METHODS

We performed a comparative usability study for two radiotherapy systems through user testing. Thirty radiation therapists participated in our study, in which four typical operational tasks were performed in two tested radiotherapy systems. User performance was measured by task completion time and completion difficulty level. User workloads were measured by perceived and physiological workload using NASA-TLX questionnaires and eye motion data. User experience was measured by the USE questionnaire.

RESULTS

Significantly less task completion time and an easier task completion difficulty level were shown with the Varian Trilogy than with the XHA600E. The study results suggest that higher perceived and physiological workloads were experienced with the XHA600E than with the Varian Trilogy. Radiation therapists reported better user experience with the Varian Trilogy than with the XHA600E. Five paired t-tests regarding user performance, user workload, and user experience between the Varian Trilogy and the XHA600E were performed, showing that the Varian Trilogy radiotherapy system has a better usability design than the XHA600E radiotherapy system.

CONCLUSIONS

Based on study results, we confirmed that the Varian Trilogy radiotherapy system has a better usability design than the XHA600E radiotherapy system. Furthermore, the study results provide valuable evidence for hospital procurement decision-making regarding the selection of a suitable radiotherapy system for radiation therapists to use.

Use of a Checklist Approach on a Telecobalt in an Attempt to Reduce Human Errors in Radiotherapy Delivery and Improve Therapeutic Ratio

Background:

The process of radiotherapy treatment planning and delivery involves multiple steps and professionals causing it to be prone to errors. Radiotherapy centers equipped with old telecobalt machines have certain peculiar challenges to workflow. We designed and tested a checklist for radiotherapy technicians (RTTs) to reduce chances of error during treatment delivery on a telecobalt machine.

Materials and Methods:

A physical checklist was designed for RTTs to use in the pretreatment pause using a template advocated by the American Association of Physicists in Medicine. It was tested on 4 RTTs over 1000 radiotherapy delivery sittings.

Results:

The checklist helped to rectify 41 documentary lapses and 28 errors in radiotherapy treatment parameters while also identifying 12 instances where treatment plan modifications were due and 30 where the patient was due for review by the radiation oncologist. The average time to go through the checklist was between 2.5 and 3 min.

Conclusions:

The development and use of the checklist has helped in reducing errors and also improving workflow in our department. It is recommended to utilize such physical checklists in all radiotherapy centers with telecobalt machines. The success of the checklist depends upon leadership, teamwork, acceptance of a need to inculcate a “safety culture,” with voluntary error-reporting and a willingness to learn from such errors.

Clinical paradigms and challenges in surface guided radiation therapy: Where do we go from here?

Surface guided radiotherapy (SGRT) is becoming a routine tool for patient positioning for specific clinical sites in many clinics. However, it has not yet gained its full potential in terms of widespread adoption. This vision paper first examines some of the difficulties in transitioning to SGRT before exploring the current and future role of SGRT alongside and in concert with other imaging techniques. Finally, future horizons and innovative ideas that may shape and impact the direction of SGRT going forward are reviewed.

The journey towards safer radiotherapy: are we on a road to nowhere?

Background:

Harnessing available knowledge and learning from our errors are prerequisites of delivering on the challenge of improving patient safety. Towards Safer Radiotherapy, published in 2008, was a response from the UK’s (UK) radiotherapy community to concerns arising from high profile errors. The report was a driver for the development of a national reporting and learning system for radiotherapy.

Materials and methods:

A literature review was conducted covering the years from 2009 to 2020. Search terms used were radiotherapy errors, patient safety, incident learning, human factors and trend analysis. A total of 10 papers reported recommendations or implementation of changes to service delivery models following systematic error analysis. None of these were from UK service providers.

Conclusions:

Twelve years on from the publication of Towards Safer Radiotherapy, there is little evidence of impact on safety culture within the UK radiotherapy community. Although the UK has a large radiotherapy error dataset, there remain unanswered questions about the impact on the safety culture in radiotherapy.

Real-time in vivo dosimetry system based on an optical fiber-coupled microsized photostimulable phosphor for stereotactic body radiation therapy

PURPOSE

To develop an in vivo dosimeter system for stereotactic body radiation therapy (SBRT) that can perform accurate and precise real-time measurements, using a microsized amount of a photostimulable phosphor (PSP), BaFBr:Eu²⁺ .

METHODS

The sensitive volume of the PSP was 1.26 × 10^-5  cm³ . The dosimeter system was designed to apply photostimulation to the PSP after the decay of noise signals, in synchronization with the photon beam pulse of a linear accelerator (LINAC), to eliminate the noise signals completely using a time separation technique. The noise signals included stem signals, and radioluminescence signals generated by the PSP. In addition, the dosimeter system was built on a storage-type dosimeter that could read out a signal after an arbitrary preset number of photon beam pulses were incident. First, the noise and photostimulated luminescence (PSL) signal decay times were measured. Subsequently, we confirmed that the PSL signals could be exclusively read out within the photon beam pulse interval. Finally, using a water phantom, the basic characteristics of the dosimeter system were demonstrated under SBRT conditions, and the feasibility for clinical application was investigated. The reproducibility, dose linearity, dose-rate dependence, temperature dependence, and angular dependence were evaluated. The feasibility was confirmed by measurements at various dose gradients and using a representative treatment plan for a metastatic liver tumor. A clinical plan was created with a two-arc beam volumetric modulated arc therapy using a 10 MV flattening filter-free photon beam. For the water phantom measurements, the clinical plan was compiled into a plan with a fixed gantry angle of 0°. To evaluate the energy dependence during SBRT, the percent depth dose (PDD) was measured and compared with those calculated via Monte Carlo (MC) simulations.

RESULTS

All the PSL signals could be read out while eliminating the noise signals within the minimum pulse interval of the LINAC. Stable real-time measurements could be performed with a time resolution of 56 ms (i.e., number of pulses = 20). The dose linearity was good in the dose range of 0.01-100 Gy. The measurements agreed within 1% at dose rates of 40-2400 cGy/min. The temperature and angular dependence were also acceptable since these dependencies had only a negligible effect on the measurements in SBRT. At a dose gradient of 2.21 Gy/mm, the measured dose agreed with that calculated using a treatment planning system (TPS) within the measurement uncertainties due to the probe position. For measurements using a representative treatment plan, the measured dose agreed with that calculated using the TPS within 0.5% at the center of the beam axis. The PDD measurements agreed with the MC calculations to within 1% for field sizes <5 × 5 cm² .

CONCLUSION

The in vivo dosimeter system developed using BaFBr:Eu²⁺ is capable of real-time, accurate, and precise measurement under SBRT conditions. The probe is smaller than a conventional dosimeter, has excellent spatial resolution, and can be valuable in SBRT with a steep dose distribution over a small field. The developed PSP dosimeter system appears to be suitable for in vivo SBRT dosimetry.

Common Error Pathways in CyberKnife™ Radiation Therapy

Purpose/Objectives: Stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT) may be considered “high risk” due to the high doses per fraction. We analyzed CyberKnife™ (CK) SRS and SBRT-related incidents that were prospectively reported to our in-house incident learning system (ILS) in order to identify severity, contributing factors, and common error pathways.

Material and Methods: From 2012 to 2019, 221 reported incidents related to the 4,569 CK fractions delivered (5.8%) were prospectively analyzed by our multi-professional Quality and Safety Committee with regard to severity, contributing factors, as well as the location where the incident occurred (tripped), where it was discovered (caught), and the safety barriers that were traversed (crossed) on the CK process map. Based on the particular step in the process map that incidents tripped, we categorized incidents into general error pathways.

Results: There were 205 severity grade 1–2 (did not reach patient or no clinical impact), 11 grade 3 (clinical impact unlikely), 5 grade 4 (altered the intended treatment), and 0 grade 5–6 (life-threatening or death) incidents, with human performance being the most common contributing factor (79% of incidents). Incidents most commonly tripped near the time when the practitioner requested CK simulation (e.g., pre-CK simulation fiducial marker placement) and most commonly caught during the physics pre-treatment checklist. The four general error pathways included pre-authorization, billing, and scheduling issues (n= 119); plan quality (n= 30); administration of IV contrast during simulation or pre-medications during treatment (n= 22); and image guidance (n= 12).

Conclusion: Most CK incidents led to little or no patient harm and most were related to billing and scheduling issues. Suboptimal human performance appeared to be the most common contributing factor to CK incidents. Additional study is warranted to develop and share best practices to reduce incidents to further improve patient safety.

[A Human Factors Study Using VTA for Incident Cases in Radiotherapy]

In recent years, workload has increased with higher precision of radiotherapy. Although both efficiency and thoroughness of treatment are crucial, in such conditions, human error is easy to occur. In this study, five incident cases that occurred in four facilities were studied and analyzed from the viewpoint of human factors that contribute to errors using variation tree analysis. We also analyzed resilience (the ability to return to one's original state even if the system deviates from a stable state), which has attracted attention in recent safety research. There were potential factors represented by patient factors in all cases. These factors caused deviations from standard operations, and incidents occurred due to unfamiliar situations and operations. Furthermore, in four of the five cases, the cause of the incident was a resilience action or judgment that was deemed to have required "some sort of ingenuity or adjustment." It was found that human error occurred due to multiple simultaneous occurrences of potential factors, i.e., patient and human factors such as high workload, impatience, and work interruptions. A reduction in human errors can be achieved by avoiding time pressure and multitasking, creating work environment and working conditions that make resilience work well, revising ambiguous rules and procedures, and promoting standardized working methods.

New model for explaining the over-response phenomenon in percentage of depth dose curve measured using inorganic scintillating materials for optical fiber radiation sensors

Inorganic scintillating material used in optical fibre sensors (OFS) when used as dosimeters for measuring percentage depth dose (PDD) characteristics have exhibited significant differences when compared to those measured using an ionization chamber (IC), which is the clinical gold standard for quality assurance (QA) assessments. The percentage difference between the two measurements is as high as 16.5% for a 10 × 10 cm² field at 10 cm depth below the surface. Two reasons have been suggested for this: the presence of an energy effect and Cerenkov radiation. These two factors are analysed in detail and evaluated quantitatively. It is established that the influence of the energy effect is only a maximum of 2.5% difference for a beam size 10 × 10 cm² compared with the measured ionization chamber values. And the influence of the Cerenkov radiation is less than 0.14% in an inorganic scintillating material in the case of OFS when using Gd₂O₂S:Tb as the luminescent material. Therefore, there must be other mechanisms leading to over-response. The luminescence mechanism of inorganic scintillating material is theoretically analysed and a new model is proposed and validated that helps explain the over-response phenomenon.

Optimizing efficiency and safety in external beam radiotherapy using automated plan check (APC) tool and six sigma methodology

PURPOSE

To develop and implement an automated plan check (APC) tool using a Six Sigma methodology with the aim of improving safety and efficiency in external beam radiotherapy.

METHODS

The Six Sigma define-measure-analyze-improve-control (DMAIC) framework was used by measuring defects stemming from treatment planning that were reported to the departmental incidence learning system (ILS). The common error pathways observed in the reported data were combined with our departmental physics plan check list, and AAPM TG-275 identified items. Prioritized by risk priority number (RPN) and severity values, the check items were added to the APC tool developed using Varian Eclipse Scripting Application Programming Interface (ESAPI). At 9 months post-APC implementation, the tool encompassed 89 check items, and its effectiveness was evaluated by comparing RPN values and rates of reported errors. To test the efficiency gains, physics plan check time and reported error rate were prospectively compared for 20 treatment plans.

RESULTS

The APC tool was successfully implemented for external beam plan checking. FMEA RPN ranking re-evaluation at 9 months post-APC demonstrated a statistically significant average decrease in RPN values from 129.2 to 83.7 (P < .05). After the introduction of APC, the average frequency of reported treatment-planning errors was reduced from 16.1% to 4.1%. For high-severity errors, the reduction was 82.7% for prescription/plan mismatches and 84.4% for incorrect shift note. The process shifted from 4σ to 5σ quality for isocenter-shift errors. The efficiency study showed a statistically significant decrease in plan check time (10.1 ± 7.3 min, P = .005) and decrease in errors propagating to physics plan check (80%).

CONCLUSIONS

Incorporation of APC tool has significantly reduced the error rate. The DMAIC framework can provide an iterative and robust workflow to improve the efficiency and quality of treatment planning procedure enabling a safer radiotherapy process.

A Facile One-Pot Synthesis of Water-Soluble, Patchy Fe3O4-Au Nanoparticles for Application in Radiation Therapy

A facile one-pot synthesis route for the preparation of water-soluble, biocompatible patchy Fe3O4-Au nanoparticles (Fe3O4-Au pNPs) was developed. Biocompatibility was attained through surface functionalization with 1-methyl-3-(dodecylphosphonic acid) imidazolium bromide. The morphology, composition, crystal structure and magnetic properties of the Fe3O4-Au pNPs were investigated by conducting experiments with transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and superconducting quantum interference device, respectively. Internalization of the Fe3O4-Au pNPs by MCF-7 cells occurred via endocytosis. The performance of the Fe3O4-Au pNPs as X-ray radiosensitizer in tumor cells was compared with that of gold nanocluster and Fe3O4 NPs. For this reason, MCF-7, A549 and MCF-10A cells were loaded with the respective kind of nanoparticles and treated with X-rays at doses of 1, 2 or 3 Gy. The nanoparticle-induced changes of the concentration of the reactive oxygen species (ROS) were detected using specific assays, and the cell survival under X-ray exposure was assessed employing the clonogenic assay. In comparison with the gold nanocluster and Fe3O4 NPs, the Fe3O4-Au pNPs exhibited the highest catalytic capacity for ROS generation in MCF-7 and A549 cells, whereas in the X-ray-induced ROS formation in healthy MCF-10A cells was hardly enhanced by the Fe3O4 NPs and Fe3O4-Au pNPs. Moreover, the excellent performance of Fe3O4-Au pNPs as X-ray radiosensitizers was verified by the quickly decaying radiation dose survival curve of the nanoparticle-loaded MCF-7 and A549 cells and corroborated by the small values of the associated dose-modifying factors.

An Audit for Radiotherapy Planning and Treatment Errors From a Low-Middle-Income Country Centre

AIMS

To report the findings of an audit for radiotherapy errors from a low-middle-income country (LMICs) centre. This would serve as baseline data for radiotherapy error rates, their severity and causes, in such centres where modern error reporting and learning processes still do not exist.

MATERIALS AND METHODS

A planned cross-sectional weekly audit of electronic radiotherapy charts at the radiotherapy planning and delivery step for all patients treated with curative intent was conducted. Detailed analysis was carried out to determine the step of origin of error, time and contributing factors. They were graded as per indigenous institutional (TMC) radiotherapy error grading (TREG) system and the contributing factors identified were prioritised using the product of frequency, severity and ease of detection.

RESULTS

In total, 1005 consecutive radically treated patients' charts were audited, 67 radiotherapy errors affecting 60 patients, including 42 incidents and 25 near-misses were identified. Transcriptional errors (29%) were the most common type. Most errors occurred at the time of treatment planning (59.7%), with "plan information transfer to the radiation oncology information system" being the most frequently affected sub-step of the radiotherapy process (47.8%). More errors were noted at cobalt units (52/67; 77.6%) than at linear accelerators. Trend analysis showed an increased number of radiotherapy incidents on Fridays and near-misses on Mondays. Trend for increased radiotherapy errors noted in the evening over other shifts. On severity grading, most of the errors (54/60; 90%) were clinically insignificant (grade I/II). Inadequacies and non-adherence towards standard operating procedures, poor documentation and lack of continuing education were the three most prominent causes.

CONCLUSION

Preliminary data suggest a vulnerability of LMIC set-up to radiotherapy errors and emphasises the need for the development of longitudinal prospective processes, such as voluntary reporting and a continued education system, to ensure robust and comprehensive safe practises on par with centres in developed countries.

Absence of correlation between radiation-induced CD8 T-lymphocyte apoptosis and sequelae in patients with prostate cancer accidentally overexposed to radiation

Purpose

454 patients with prostate adenocarcinoma were accidentally overexposed to radiation in Epinal hospital, France, between August 1999 and January 2007. We aimed toevaluate whether radiation-induced CD4 or CD8 T-lymphocyte apoptosis (RILA) correlates with the severity of radiation toxicity.

Methods

Between 2007 and 2013, all patients who received more than 108% of the prescribed radiation dose, after correction of the treatment plan, were convened, and blood was sampled at 6-months follow-up. Maximal Digestive toxicity (MDT) and maximal urinary toxicity (MUT) were graded using the Common Terminology Criteria for Adverse Events (NCI-CTCAE) v3.0 scale. RILA was assessed using flow cytometry.

Results

245 patients were included in our study. After a median follow-up of 4.8 years, the MDT and MUT reached grade 3-4 in 37 patients and 56 patients, respectively. Patients with prostatectomy exhibited a statistically higher grade of MUT compared with those treated with definitive radiotherapy (p=0.03). The median RILA values were 11.8% and 15.3% for CD4 and CD8 T-lymphocytes, respectively. We found no significant correlation between CD4 or CD8 RILA and either MDT or MUT.

Conclusion

RILA does not correlate with the inter-individual variation in MDT or MUT in the largest cohort of patients overexposed to radiation. The magnitude of the overdosage probably overrides biological predictors of toxicity, including individual radiosensitivity.

Root Cause Analysis of Oncology Adverse Events in the Veterans Health Administration

PURPOSE

Oncology providers are leaders in patient safety. Despite their efforts, oncology-related medical errors still occur, sometimes resulting in patient injury or death. The Veterans Health Administration (VHA) National Center of Patient Safety used data obtained from root cause analysis (RCA) to determine how and why these adverse events occurred in the VHA, and how to prevent future reoccurrence. This study details the types of oncology adverse events reported in VHA hospitals and their root causes and suggests actions for prevention and improvement.

METHODS

We searched the National Center for Patient Safety adverse event reporting database for RCA related to oncology care from October 1, 2013, to September 8, 2017, to identify event types, root causes, severity of outcomes, care processes, and suggested actions. Two independent reviewers coded these variables, and inter-rater agreement was calculated by κ statistic. Variables were evaluated using descriptive statistics.

RESULTS

We identified 48 RCA reports that specifically involved an oncology provider. Event types included care delays (39.5% [n = 19]), issues with chemotherapy (25% [n = 12]) and radiation (12.5% [n = 6]), other (12.5% [n = 6]), and suicide (10.5% [n = 5]). Of the 48 events, 27.1% (n = 13) resulted in death, 4.2% (n = 2) in severe harm, 18.8% (n = 9) in temporary harm, 20.8% (n = 10) in minimal harm, and 2.1% (n = 1) in no harm. The majority of root causes identified a need to improve care processes and policies, interdisciplinary communication, and care coordination.

CONCLUSION

This analysis highlights an opportunity to implement system-wide changes to prevent similar events from reoccurring. These actions include comprehensive cancer clinics, usability testing of medical equipment, and standardization of processes and policies. Additional studies are necessary to assess oncologic adverse events across specialties.

Incident learning in radiation oncology: A review

Incident learning is a key component for maintaining safety and quality in healthcare. Its use is well established and supported by professional society recommendations, regulations and accreditation, and objective evidence. There is an active interest in incident learning systems (ILS) in radiation oncology, with over 40 publications since 2010. This article is intended as a comprehensive topic review of ILS in radiation oncology, including history and summary of existing literature, nomenclature and categorization schemas, operational aspects of ILS at the institutional level including event handling and root cause analysis, and national and international ILS for shared learning. Core principles of patient safety in the context of ILS are discussed, including the systems view of error, culture of safety, and contributing factors such as cognitive bias. Finally, the topics of medical error disclosure and second victim syndrome are discussed. In spite of the rapid progress and understanding of ILS, challenges remain in applying ILS to the radiation oncology context. This comprehensive review may serve as a springboard for further work.

A nationwide investigation of radiation therapy event reporting-and-learning systems: Can standards be improved?

INTRODUCTION

Variation exists between event reporting-and-learning systems utilised in radiation therapy. Due to the impact of errors associated with this field of medicine, evidence-based and rigorous systems are imperative. The implementation of such systems facilitates the reactive enhancement of patient safety following an event. The purpose of this study was to evaluate Irish event reporting-and-learning procedures against the current literature using a developed evidence-based process map, and to propose recommendations as to how the national standard could be improved.

METHODS

Radiation Therapy Service Managers of all Irish radiation therapy institutions (n = 12) were invited to participate in an anonymous online questionnaire. Included in the questionnaire was a reporting-and-learning process map developed from evidence-based literature, which was used to assess the institution's practice through the use of vignettes. Frequency analysis of closed-ended questions and thematic analysis of open-ended questions was performed to assess the data.

RESULTS

A 91.7% response rate was achieved. The following areas were found to have the most variation with the evidence-based process map: event classification, external reporting, and dissemination of lessons-learned to a wider audience. Recommendations to standardise practice were made.

CONCLUSION

Opportunities for improvement exist within event reporting-and-learning systems of Irish radiation therapy institutions and recommendations have been made on these. These findings can provide learning for other countries with similar reporting systems.

The effects of a lean transition on process times, patients and employees

Purpose Treatment delays must be avoided, especially in oncology, to assure sustainable high-quality health care and increase the odds of survival. The purpose of this paper is to hypothesize that waiting times would decrease and patients and employees would benefit, when specific lean interventions are incorporated in an organizational improvement approach. Design/methodology/approach In 2013, 15 lean interventions were initiated to improve flow in a single radiotherapy institute. Process/waiting times, patient satisfaction, safety, employee satisfaction, and absenteeism were evaluated using a mixed methods methodology (2010-2014). Data from databases, surveys, and interviews were analyzed by time series analysis, χ², multi-level regression, and t-tests. Findings Median waiting/process times improved from 20.2 days in 2012 to 16.3 days in 2014 ( p<0.001). The percentage of palliative patients for which waiting times had exceeded Dutch national norms (ten days) improved from 35 (six months in 2012: pre-intervention) to 16 percent (six months in 2013-2014: post-intervention; p<0.01), and the percentage exceeding national objectives (seven days) from 22 to 17 percent ( p=0.44). For curative patients, exceeding of norms (28 days) improved from 17 (2012) to 8 percent (2013-2014: p=0.05), and for the objectives (21 days) from 18 to 10 percent ( p<0.01). Reported safety incidents decreased 47 percent from 2009 to 2014, whereas safety culture, awareness, and intention to solve problems improved. Employee satisfaction improved slightly, and absenteeism decreased from 4.6 (2010) to 2.7 percent (2014; p<0.001). Originality/value Combining specific lean interventions with an organizational improvement approach improved waiting times, patient safety, employee satisfaction, and absenteeism on the short term. Continuing evaluation of effects should study the improvements sustainability.

Comparison of dicentric dose response curves of 6MV LINAC X-rays and 60Co γ-rays for biodosimetry application

In vitro Dicentric (DC) dose response curves of 6MV X-rays (3Gy/min) and ⁶⁰Co γ-rays (0.63Gy/min) were generated and compared (intra-laboratory) to understand their similarities and differences. Human peripheral blood samples exposed to ten different doses (0, 0.05, 0.1, 0.25, 0.5, 1, 2, 3, 4 and 5Gy) of 6MV X-rays and ⁶⁰Co γ-rays were subjected to Dicentric Chromosome Assay (DCA) and dicentrics, excess acentric fragments (AF) and chromatid breaks (CB) were scored. Totally about 31,553 metaphase spreads were scored for the purpose. Dose response curves of both radiation qualities were almost same except for a 13.8% higher β value for 6MV X-rays. However, blind tests results revealed that both these curves are biologically equivalent and exhibited good dose prediction accuracy for the entire dose range. This demonstrated the feasibility of interchangeable use of these curves in biodosimetry. Consequently it has been suggested that LINAC facilities worldwide can be roped in for biodosimetry capacity augmentation towards managing nuclear emergency situations involving γ-radiation exposures.

Safety Considerations in Stereotactic Body Radiation Therapy

Although many error pathways are common to both stereotactic body radiation therapy (SBRT) and conventional radiation therapy, SBRT presents a special set of challenges including short treatment courses and high-doses, an enhanced reliance on imaging, technical challenges associated with commissioning, special resource requirements for staff and training, and workflow differences. Emerging data also suggest that errors occur at a higher rate in SBRT treatments. Furthermore, when errors do occur they often have a greater effect on SBRT treatments. Given these challenges, it is important to understand and employ systematic approaches to ensure the quality and safety of SBRT treatment. Here, we outline the pathways by which error can occur in SBRT, illustrated through a series of case studies, and highlight 9 specific well-established tools to either reduce error or minimize its effect to the patient or both.

Implementation of Nanoparticles in Cancer Therapy

Cancer is a wide group of diseases and generally characterized by uncontrolled proliferation of cells whose metabolic activities are disrupted. Conventionally, chemotherapy, radiotherapy, and surgery are used in the treatment of cancer. However, in theory, even a single cancer cell may trigger recurrence. Therefore, these treatments cannot provide high survival rate for deadly types. Identification of alternative methods in treatment of cancers is inevitable because of adverse effects of conventional methods. In the last few decades, nanotechnology developed by scientists working in different disciplines—physics, chemistry, and biology—offers great opportunities. It is providing elimination of both circulating tumor cells and solid cancer cells by targeting cancer cells. In this chapter, inadequate parts of conventional treatment methods, nanoparticle types used in new treatment methods of cancer, and targeting methods of nanoparticles are summarized; furthermore, recommendations of future are provided.

Water-equivalent fiber radiation dosimeter with two scintillating materials

An inorganic scintillating material plastic optical fiber (POF) dosimeter for measuring ionizing radiation during radiotherapy applications is reported. It is necessary that an ideal dosimeter exhibits many desirable qualities, including water equivalence, energy independence, reproducibility, dose linearity. There has been much recent research concerning inorganic dosimeters. However, little reference has been made to date of the depth-dose characteristics of dosimeter materials. In the case of inorganic scintillating materials, they are predominantly non water-equivalent, with their effective atomic weight (Z_eff) being typically much greater than that of water. This has been a barrier in preventing inorganic scintillating material dosimeter from being used in actual clinical applications. In this paper, we propose a parallel-paired fiber light guide structure to solve this problem. Two different inorganic scintillating materials are embedded separately in the parallel-paired fiber. It is shown that the information of water depth and absorbed dose at the point of measurement can be extracted by utilizing their different depth-dose properties.

Optical fibre sensors: their role in in vivo dosimetry for prostate cancer radiotherapy

Review is made of dosimetric studies of current optical fibre technology in radiotherapy for therapeutic applications, focusing particularly on in vivo dosimetry for prostate radiotherapy. We present the various sensor designs along with the main advantages and disadvantages associated with this technology. Optical fibres are ideally placed for applications in radiotherapy dosimetry; due to their small size they are lightweight and immune to electromagnetic interferences. The small dimensions of optical fibres allows it to be easily guided within existing brachytherapy equipment; for example, within the seed implantation needle for direct tumour dose analysis, in the urinary catheter to monitor urethral dose, or within the biopsy needle holder of the transrectal ultrasound probe to monitor rectal wall dose. The article presents the range of optical fibre dosimeter designs along with the main dosimetric properties required for a modern in vivo dosimetry system to be utilised in a clinical environment.

EPID based in vivo dosimetry system: clinical experience and results

Mandatory in several countries, in vivo dosimetry has been recognized as one of the next milestones in radiation oncology. Our department has implemented clinically an EPID based in vivo dosimetry system, EPIgray, by DOSISOFT S.A., since 2006. An analysis of the measurements per linac and energy over a two‐year period was performed, which included a more detailed examination per technique and treatment site over a six‐month period. A comparison of the treatment planning system doses and the doses estimated by EPIgray shows a mean of the differences of 1.9% (±5.2%) for the two‐year period. The 3D conformal treatment plans had a mean dose difference of 2.0% (±4.9%), while for intensity‐modulated radiotherapy and volumetric‐modulated arc therapy treatments the mean dose difference was −3.0 (±5.3%) and −2.5 (±5.2%), respectively. In addition, root cause analyses were conducted on the in vivo dosimetry measurements of two breast cancer treatment techniques, as well as prostate treatments with intensity‐modulated radiotherapy and volumetric‐modulated arc therapy. During the breast study, the dose differences of breast treatments in supine position were correlated to patient setup and EPID positioning errors. Based on these observations, an automatic image shift correction algorithm is developed by DOSIsoft S.A. The prostate study revealed that beams and arcs with out‐of‐tolerance in vivo dosimetry results tend to have more complex modulation and a lower exposure of the points of interest. The statistical studies indicate that in vivo dosimetry with EPIgray has been successfully implemented for classical and complex techniques in clinical routine at our institution. The additional breast and prostate studies exhibit the prospects of EPIgray as an easy supplementary quality assurance tool. The validation, the automatization, and the reduction of false‐positive results represent an important step toward adaptive radiotherapy with EPIgray.

PACS number(s): 87.53.Bn, 87.55.Qr, 87.56.Fc, 87.57.uq