ICRP publication 112. A report of preventing accidental exposures from new external beam radiation therapy technologies

A feasibility study of dosimetry for breast cancer radiotherapy based on body surface changes

BACKGROUND

The requirement for precise and effective delivery of the actual dose to the patient grows along with the complexity of breast cancer radiotherapy. Dosimetry during treatment has become a crucial component of guaranteeing the efficacy and security.

PURPOSE

To propose a dosimetry method during breast cancer radiotherapy based on body surface changes.

METHODS

A total of 29 left breast cancer radiotherapy cases were retroactively retrieved from an earlier database for analysis. Non-rigid image registration and dose recalculation of the planning computed tomography (CT) referring to the Cone-beam computed tomography were performed to obtain dose changes. The study used 3D point cloud feature extraction to characterize body surface changes. Based on the correlation proof, a mapping model is developed between body surface changes and dose changes using neural network framework. The MSE metrics, the Euclidean distances of feature points and the 3D gamma pass rate metric were used to assess the prediction accuracy.

RESULTS

A strong correlation exist between body surface changes and dose changes (first canonical correlation coefficient = 0.950). For the dose deformation field and dose amplitude difference in the test set, the MSE of the predicted and actual values were 0.136 pixels and 0.229 cGy, respectively. After deforming the planning dose into a deformed one, the feature points' Euclidean distance between it and the recalculated dose changes from 9.267 ± 1.879 mm to 0.456 ± 0.374 mm. The 3D gamma pass rate of 90% or higher for the 2 mm/2% criteria were achieved by 80.8% of all cases, with a minimum pass rate of 75.9% and a maximum pass rate of 99.6%. Pass rate for the 3 mm/2% criteria ranged from 87.8% to 99.8%, with 92.3% of the cases having a pass rate of 90% or higher.

CONCLUSIONS

This study provides a dosimetry method that is non-invasive, real-time, and requires no additional dose for breast cancer radiotherapy.

Commissioning and clinical implementation of an independent dose calculation system for scanned proton beams

PURPOSE

Experimental patient-specific QA (PSQA) is a time and resource-intensive process, with a poor sensitivity in detecting errors. Radiation therapy facilities aim to substitute it by means of independent dose calculation (IDC) in combination with a comprehensive beam delivery QA program. This paper reports on the commissioning of the IDC software tool myQA iON (IBA Dosimetry) for proton therapy and its clinical implementation at the MedAustron Ion Therapy Center.

METHODS

The IDC commissioning work included the validation of the beam model, the implementation and validation of clinical CT protocols, and the evaluation of patient treatment data. Dose difference maps, gamma index distributions, and pass rates (GPR) have been reviewed. The performance of the IDC tool has been assessed and clinical workflows, simulation settings, and GPR tolerances have been defined.

RESULTS

Beam model validation showed agreement of ranges within ± 0.2 mm, Bragg-Peak widths within ± 0.1 mm, and spot sizes at various air gaps within ± 5% compared to physical measurements. Simulated dose in 2D reference fields deviated by -0.3% ± 0.5%, while 3D dose distributions differed by 1.8% on average to measurements. Validation of the CT calibration resulted in systematic differences of 2.0% between IDC and experimental data for tissue like samples. GPRs of 99.4 ± 0.6% were found for head, head and neck, and pediatric CT protocols on a 2%/2 mm gamma criterion. GPRs for the adult abdomen protocol were at 98.9% on average with 3%/3 mm. Root causes of GPR outliers, for example, implants were identified and evaluated.

CONCLUSION

IDC has been successfully commissioned and integrated into the MedAustron clinical workflow for protons in 2021. IDC has been stepwise and safely substituting experimental PSQA since February 2021. The initial reduction of proton experimental PSQA was about 25% and reached up to 90% after 1 year.

Technical note: A universal worksheet for failure mode and effects analysis-A project of the Japanese College of Medical Physics

BACKGROUND

Failure mode and effects analysis (FMEA), which is an effective tool for error prevention, has garnered considerable attention in radiotherapy. FMEA can be performed individually, by a group or committee, and online.

PURPOSE

To meet the needs of FMEA for various purposes and improve its accessibility, we developed a simple, self-contained, and versatile web-based FMEA risk analysis worksheet.

METHODS

We developed an FMEA worksheet using Google products, such as Google Sheets, Google Forms, and Google Apps Script. The main sheet was created in Google Sheets and contained elements necessary for performing FMEA by a single person. Automated tasks were implemented using Apps Script to facilitate multiperson FMEA; these functions were built into buttons located on the main sheet.

RESULTS

The usability of the FMEA worksheet was tested in several situations. The worksheet was feasible for individual, multiperson, seminar, meeting, and online purposes. Simultaneous online editing, automated survey form creation, automatic analysis, and the ability to respond to the form from multiple devices, including mobile phones, were particularly useful for online and multiperson FMEA. Automation enabled through Google Apps Script reduced the FMEA workload.

CONCLUSIONS

The FMEA worksheet is versatile and has a seamless workflow that promotes collaborative work for safety.

Recommendations for stereotactic body radiation therapy for spine and non-spine bone metastases. A GETUG (French society of urological radiation oncolgists) consensus using a national two-round modified Delphi survey

Background and purpose

The relevance of metastasis-directed stereotactic body radiation therapy (SBRT) remains to be demonstrated through phase III trials. Multiple SBRT procedures have been published potentially resulting in a disparity of practices. Therefore, the french society of urological radiation oncolgists (GETUG) recognized the need for joint expert consensus guidelines for metastasis-directed SBRT in order to standardize practice in trials carried out by the group.

Materials and methods

After a comprehensive literature review, 97 recommendation statements were created regarding planning and delivery of spine bone (SBM) and non-spine bone metastases (NSBM) SBRT. These statements were then submitted to a national online two-round modified Delphi survey among main GETUG investigators. Consensus was achieved if a statement received ≥ 75 % agreements, a trend to consensus being defined as 65-74 % agreements. Any statement without consensus at round one was re-submitted in round two.

Results

Twenty-one out of 29 (72.4%) surveyed experts responded to both rounds. Seventy-five statements achieved consensus at round one leaving 22 statements needing a revote of which 16 achieved consensus and 5 a trend to consensus. The final rate of consensus was 91/97 (93.8%). Statements with no consensus concerned patient selection (3/19), dose and fractionation (1/11), prescription and dose objectives (1/9) and organs at risk delineation (1/15). The voting resulted in the writing of step-by-step consensus guidelines.

Conclusion

Consensus guidelines for SBM and NSBM SBRT were agreed upon using a validated modified Delphi approach. These guidelines will be used as per-protocole recommendations in ongoing and further GETUG clinical trials.

Natural language processing and machine learning to assist radiation oncology incident learning

PURPOSE

To develop a Natural Language Processing (NLP) and Machine Learning (ML) pipeline that can be integrated into an Incident Learning System (ILS) to assist radiation oncology incident learning by semi-automating incident classification. Our goal was to develop ML models that can generate label recommendations, arranged according to their likelihoods, for three data elements in Canadian NSIR-RT taxonomy.

METHODS

Over 6000 incident reports were gathered from the Canadian national ILS as well as our local ILS database. Incident descriptions from these reports were processed using various NLP techniques. The processed data with the expert-generated labels were used to train and evaluate over 500 multi-output ML algorithms. The top three models were identified and tuned for each of three different taxonomy data elements, namely: (1) process step where the incident occurred, (2) problem type of the incident and (3) the contributing factors of the incident. The best-performing model after tuning was identified for each data element and tested on unseen data.

RESULTS

The MultiOutputRegressor extended Linear SVR models performed best on the three data elements. On testing, our models ranked the most appropriate label 1.48 ± 0.03, 1.73 ± 0.05 and 2.66 ± 0.08 for process-step, problem-type and contributing factors respectively.

CONCLUSIONS

We developed NLP-ML models that can perform incident classification. These models will be integrated into our ILS to generate a drop-down menu. This semi-automated feature has the potential to improve the usability, accuracy and efficiency of our radiation oncology ILS.

Usability of detecting delivery errors during treatment of prostate VMAT with a gantry-mounted transmission detector

Volumetric‐modulated arc therapy (VMAT) requires highly accurate control of multileaf collimator (MLC) movement, rotation speed of linear accelerator gantry, and monitor units during irradiation. Pretreatment validation and monitoring of these factors during irradiation are necessary for appropriate VMAT treatment. Recently, a gantry mounted transmission detector “Delta⁴ Discover® (D4D)” was developed to detect errors in delivering doses and dose distribution immediately after treatment. In this study, the performance of D4D was evaluated. Simulation plans, in which the MLC position was displaced by 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mm from the clinically used original plans, were created for ten patients who received VMAT treatment for prostate cancer. Dose deviation (DD), distance‐to‐agreement (DTA), and gamma index analysis (GA) for each plan were evaluated by D4D. These results were compared to the results (DD, DTA and GA) measured by Delta⁴ Phantom + (D4P). We compared the deviations between the planned and measured values of the MLC stop positions A‐side and B‐side in five clinical cases of prostate VMAT during treatment and measured the GA values. For D4D, when the acceptable errors for DD, DTA, and GA were determined to be ≤3%, ≤2 mm, and ≤3%/2 mm, respectively, the minimum detectable errors in the MLC position were 2.0, 1.5, and 1.5 mm based on DD, DTA, and GA respectively. The corresponding minimum detectable MLC position errors were 2.0, 1.0, and 1.5 mm, respectively, for D4P. The deviation between the planned and measured position of MLC stopping point of prostate VMAT during treatment was stable at an average of −0.09 ± 0.05 mm, and all GA values were above 99.86%. In terms of delivering doses and dose distribution of VMAT, error detectability of D4D was comparable to that of D4P. The transmission‐type detector “D4D” is thus suitable for detecting delivery errors during irradiation.

Evaluation of automated pre-treatment and transit in-vivo dosimetry in radiotherapy using empirically determined parameters

Background and purpose

First reports on clinical use of commercially automated systems for Electronic Portal Imaging Device (EPID)-based dosimetry in radiotherapy showed the capability to detect important changes in patient setup, anatomy and external device position. For this study, results for more than 3000 patients, for both pre-treatment verification and in-vivo transit dosimetry were analyzed.

Materials and methods

For all Volumetric Modulated Arc Therapy (VMAT) plans, pre-treatment quality assurance (QA) with EPID images was performed. In-vivo dosimetry using transit EPID images was analyzed, including causes and actions for failed fractions for all patients receiving photon treatment (2018-2019). In total 3136 and 32,632 fractions were analyzed with pre-treatment and transit images respectively. Parameters for gamma analysis were empirically determined, balancing the rate between detection of clinically relevant problems and the number of false positive results.

Results

Pre-treatment and in-vivo results depended on machine type. Causes for failed in-vivo analysis included deviations in patient positioning (32%) and anatomy change (28%). In addition, errors in planning, imaging, treatment delivery, simulation, breath hold and with immobilization devices were detected. Actions for failed fractions were mostly to repeat the measurement while taking extra care in positioning (54%) and to intensify imaging procedures (14%). Four percent initiated plan adjustments, showing the potential of the system as a basis for adaptive planning.

Conclusions

EPID-based pre-treatment and in-vivo transit dosimetry using a commercially available automated system efficiently revealed a wide variety of deviations and showed potential to serve as a basis for adaptive planning.

Development, implementation, and associated challenges of a new HDR brachytherapy program

Developing any new radiation oncology program requires planning and analysis of the current state of the facility and its capacity to take on another program. Staff must consider a large number of factors to establish a feasible, safe, and sustainable program. We present a simple and generic outline that lays out the process for developing and implementing a new HDR brachytherapy program in any setting, but with particular emphasis on challenges associated with starting the program in a limited resource setting. The sections include feasibility of a program, starting cases, machine and equipment selection, and quality and safety.

Patient safety in radiation oncology in Spain: a need to change

PURPOSE

The Working Group on Patient Safety and Quality of the Spanish Society of Radiation Oncology, revised the most relevant national and international recommendations, selecting a series of important aspects for patient safety, evaluating whether they are included in Spanish legislation MATERIALS AND METHODS: We have considered a concept as relevant to the patient safety in radiotherapy if so defined in at least 8 of the 16 documents reviewed.

RESULTS

12 subjects were selected: training and qualification, human resources, protocols, safety culture, communication, peer review, accreditation: audits, checklists, areas without interruptions, maps of processes and risks, prospective risk analysis, notification, registration and incident learning, and quality control of the equipment.

CONCLUSIONS

At the legislative level, as well as the professional organizations and the health center directorates, the implementation of safety culture must continue to be fostered. Only in this environment will the tools and measures to increase patient safety be effective. The current Spanish legislation must be revised and updated, in accordance with directive 2013/59/EURATOM and the Patient Safety Strategy 2015-2020 of the Spanish National Health System, introducing the obligation to perform risk analysis and incidents management. Audits and accreditations must be carried out, thus raising the general level of practice of the specialty. In this process, the Spanish Society of Radiation Oncology must continue playing its fundamental role, collaborating with the institutions and the rest of the scientific societies involved in the radiotherapy process, issuing recommendations on patient safety and disseminating the safety culture in our specialty.

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.

A validation study of a dedicated software for an automated in vivo dosimetry control in radiotherapy

In vivo dosimetry (IVD) is the last step of a radiotherapy quality control program aimed to ensure that the dose delivered is in agreement with that prescribed. IVD procedures based on single detectors are time-consuming and impossible to use for the modern radiotherapy techniques, based on static or kinetic beams (modulated in intensity fluence); this means that more efficient and practical methods are highly recommended. The practical method SOFTDISO, based on the use of electronic portal image device (EPID), provides two tests (i) the R ratio between the reconstructed and the planned isocenter doses to verify an agreement within 5% and (ii) the γ-analysis of the EPID images, to verify γ% ≥ 90% and γ_mean ≤ 0.4. This paper reports the results of 11,357 IVD tests carried out for 823 patients treated by three-dimensional conformal radiation therapy and volumetric modulated arc therapy techniques. In particular, the dose disagreements are reported distinguishing two kinds of causes, those of (i) class 1 that includes the errors due to inadequate quality controls and (ii) the class 2, due to patient morphological changes. About the tests out of tolerance, 6% were by VMAT and 21% by 3DCRT, but taking into account the only class 1 of errors, i.e., removing the causes of class 2, only 7% of patients examined presented at least one of the three mean indexes out of tolerance. The workload for IVD on 9 patients/day per linac is about 52 min/day but recently, a new automated SOFTDISO version has been implemented to reduce the time to about 34 min/day.

Intensity-modulated radiation therapy: a review with a physics perspective

Intensity-modulated radiation therapy (IMRT) has been considered the most successful development in radiation oncology since the introduction of computed tomography into treatment planning that enabled three-dimensional conformal radiotherapy in 1980s. More than three decades have passed since the concept of inverse planning was first introduced in 1982, and IMRT has become the most important and common modality in radiation therapy. This review will present developments in inverse IMRT treatment planning and IMRT delivery using multileaf collimators, along with the associated key concepts. Other relevant issues and future perspectives are also presented.

A Feasibility Study for in vivo Dosimetry Procedure in Routine Clinical Practice

Purpose:

The aim of the in vivo dosimetry, during the fractionated radiation therapy, is the verification of the correct dose delivery to patient. Nowadays, in vivo dosimetry procedures for photon beams are based on the use of the electronic portal imaging device and dedicated software to elaborate electronic portal imaging device images.

Methods:

In total, 8474 in vivo dosimetry tests were carried out for 386 patients treated with 3-dimensional conformal radiotherapy, intensity-modulated radiotherapy, and volumetric modulated arc therapy techniques, using the SOFTDISO. SOFTDISO is a dedicated software that uses electronic portal imaging device images in order to (1) calculate the R index, that is, the ratio between daily reconstructed dose and the planned one at isocenter and (2) perform a γ-like analysis between the signals, S, of a reference electronic portal imaging device image and that obtained in a daily fraction. It supplies 2 indexes, the percentage γ% of points with γ < 1 and the mean γ value, γ_mean. In γ-like analysis, the pass criteria for the signals agreement ΔS% and distance to agreement Δd have been selected based on the clinical experience and technology used. The adopted tolerance levels for the 3 indexes were fixed in 0.95 ≤ R ≤ 1.05, γ% ≥ 90%, and γ_mean ≤ 0.5.

Results:

The results of R ratio, γ-like, and a visual inspection of these data reported on a monitor screen permitted to individuate 2 classes of errors (1) class 1 that included errors due to inadequate standard quality controls and (2) class 2, due to patient morphological changes. Depending on the technique and anatomical site, a maximum of 18% of tests had at least 1 index out of tolerance; once removed the causes of class-1 errors, almost all patients (except patients with 4 lung and 2 breast cancer treated with 3-dimensional conformal radiotherapy) presented mean indexes values (R¯, γ¯%, and γ¯mean ) within tolerance at the end of treatment course. Class-2 errors were found in some patients.

Conclusions:

The in vivo dosimetry procedure with SOFTDISO resulted easily implementable, able to individuate errors with a limited workload.

Experimental verification of a 3D in vivo dose monitoring system based on EPID

Purpose

To evaluate the Edose system, a novel three-dimensional (3D) in vivo dose monitoring system based on electronic portal imaging device (EPID), prior to clinical application, we analyzed the preliminary clinical data using Edose system in patients receiving intensity-modulated radiation therapy (IMRT).

Materials and methods

After the physical modeling, the measured results from the Edose system were examined in homogeneous and inhomogeneous phantoms, respectively. To verify the accuracy of the Edose system, we compared its results with testing results from ionization chamber, measurement matrix (Delta4) and dosimetric films. The dosimetric performance of the Edose system was evaluated in 12 randomly selected patients with IMRT and VMAT, and the measured results were compared with the treatment plans.

Results

Compared with the measured results, the dose difference at the center of target volume was (0.12±0.91)% and (0.03±0.85)%, the γ pass rate was (94.18±1.69)% and (95.24±1.62)% (3mm/3%)for homogeneous and inhomogeneous phantoms, respectively. For IMRT patients, the dose difference at the center of target volume was (0.75±1.53)%, and the γ pass rates were (89.11±3.24)% (3mm/3%) and (96.40±1.47)% (3mm/5%), respectively. Compared with the results of DVH, the maximum differences of PTVs and mostly organs at risk were all within 3%. For VMAT patients, the γ pass rates were (93.04 ± 2.62)% (3mm/3%) and (97.92 ± 1.38)% (3mm/5%), respectively.

Conclusions

In vivo dose monitoring may further improve the safety and quality assurance for radiation therapy. But rigorous clinical testing is required before putting the existing commercial systems into clinical application. In addition, more clinical experiences and better workflows for using the Edose system are needed.

Failure modes and effects analysis of total skin electron irradiation technique

PURPOSE

Total skin electron irradiation (TSEI) is a radiotherapy technique which consists of an homogeneous body surface irradiation by electrons. This treatment requires very strict technical and dosimetric conditions, requiring the implementation of multiple controls. Recently, the Task Group 100 report of the AAPM has recommended adapting the quality assurance program of the facility to the risks of their processes.

MATERIALS AND METHODS

A multidisciplinary team evaluated the potential failure modes (FMs) of every process step, regardless of the management tools applied in the installation. For every FM, occurrence (O), severity (S) and detectability (D) by consensus was evaluated, which resulted in the risk priority number (RPN), which permitted the ranking of the FMs. Subsequently, all the management tools used, related to the TSEI process, were examined and the FMs were reevaluated, to analyze the effectiveness of these tools and to propose new management tools to cover the greater risk FMs.

RESULTS

361 FMs were identified, 103 of which had RPN ≥80, initially, and 41 had S ≥ 8. Taking this into account the quality management tools FMs were reevaluated and only 30 FMs had RPN ≥80. The study of these 30 FMs emphasized that the FMs that involved greater risk were related to the diffuser screen placement and the patient's position during treatment.

CONCLUSIONS

The quality assurance program of the facility has been adapted to the risk of this treatment process, following the guidelines proposed by the TG-100. However, clinical experience continually reveals new FMs, so the need for periodic risk analysis is required.

Characterization of Water-Clear Polymeric Gels for Use as Radiotherapy Bolus

Our purpose was to investigate polymeric gels for use as a highly transparent radiotherapy bolus and determine the relevant physical and dosimetric properties. We first quantified tensile properties (maximum stress, strain, and Young modulus) for various polymeric gels, along with a commercial bolus product in order to illustrate the wide variety of potential materials. For a select polymeric gel with tensile properties similar to currently used radiotherapy bolus, we also evaluated mass and electron density, effective atomic number, optical transparency, and percent depth dose in clinical megavoltage photon and electron beams. For this polymeric gel, mass density was 872 ± 12 and 896 ± 13 g/cm³ when measured via weight/volume and computed tomography Hounsfield units, respectively. Electron density was 2.95 ± 0.04 ×10²³ electrons/cm³. Adding fused silica (9% by weight) increases density to that of water. The ratio of the effective atomic number to that of water without and with added silica was 0.780 and 0.835 at 1 MeV, 0.767 and 0.826 at 6 MeV, and 0.746 and 0.809 at 20 MeV. Percent depth dose for 6 MV photons was within 2% of water within the first 2.5 cm and after scaling by the density coincided within 1% out to >7 cm. For 6 and 20 MeV electrons, after scaling for density D_80% was within 1.3 and 1.5 mm of water, respectively. The high transparency and mechanical flexibility of polymeric gels indicate potential for use as a radiotherapy bolus; differences in density from water may be managed via either using “water equivalent thickness” or by incorporating fused silica into the material.

Failure mode and effects analysis of skin electronic brachytherapy using Esteya® unit

Purpose

Esteya^® (Nucletron, an Elekta company, Elekta AB, Stockholm, Sweden) is an electronic brachytherapy device used for skin cancer lesion treatment. In order to establish an adequate level of quality of treatment, a risk analysis of the Esteya treatment process has been done, following the methodology proposed by the TG-100 guidelines of the American Association of Physicists in Medicine (AAPM).

Material and methods

A multidisciplinary team familiar with the treatment process was formed. This team developed a process map (PM) outlining the stages, through which a patient passed when subjected to the Esteya treatment. They identified potential failure modes (FM) and each individual FM was assessed for the severity (S), frequency of occurrence (O), and lack of detection (D). A list of existing quality management tools was developed and the FMs were consensually reevaluated. Finally, the FMs were ranked according to their risk priority number (RPN) and their S.

Results

146 FMs were identified, 106 of which had RPN ≥ 50 and 30 had S ≥ 7. After introducing the quality management tools, only 21 FMs had RPN ≥ 50. The importance of ensuring contact between the applicator and the surface of the patient’s skin was emphasized, so the setup was reviewed by a second individual before each treatment session with periodic quality control to ensure stability of the applicator pressure. Some of the essential quality management tools are already being implemented in the installation are the simple templates for reproducible positioning of skin applicators, that help marking the treatment area and positioning of X-ray tube.

Conclusions

New quality management tools have been established as a result of the application of the failure modes and effects analysis (FMEA) treatment. However, periodic update of the FMEA process is necessary, since clinical experience has suggested occurring of further new possible potential failure modes.

The report of Task Group 100 of the AAPM: Application of risk analysis methods to radiation therapy quality management

The increasing complexity of modern radiation therapy planning and delivery challenges traditional prescriptive quality management (QM) methods, such as many of those included in guidelines published by organizations such as the AAPM, ASTRO, ACR, ESTRO, and IAEA. These prescriptive guidelines have traditionally focused on monitoring all aspects of the functional performance of radiotherapy (RT) equipment by comparing parameters against tolerances set at strict but achievable values. Many errors that occur in radiation oncology are not due to failures in devices and software; rather they are failures in workflow and process. A systematic understanding of the likelihood and clinical impact of possible failures throughout a course of radiotherapy is needed to direct limit QM resources efficiently to produce maximum safety and quality of patient care. Task Group 100 of the AAPM has taken a broad view of these issues and has developed a framework for designing QM activities, based on estimates of the probability of identified failures and their clinical outcome through the RT planning and delivery process. The Task Group has chosen a specific radiotherapy process required for "intensity modulated radiation therapy (IMRT)" as a case study. The goal of this work is to apply modern risk-based analysis techniques to this complex RT process in order to demonstrate to the RT community that such techniques may help identify more effective and efficient ways to enhance the safety and quality of our treatment processes. The task group generated by consensus an example quality management program strategy for the IMRT process performed at the institution of one of the authors. This report describes the methodology and nomenclature developed, presents the process maps, FMEAs, fault trees, and QM programs developed, and makes suggestions on how this information could be used in the clinic. The development and implementation of risk-assessment techniques will make radiation therapy safer and more efficient.

Multi-institutional application of Failure Mode and Effects Analysis (FMEA) to CyberKnife Stereotactic Body Radiation Therapy (SBRT)

Background

A multidisciplinary and multi-institutional working group applied the Failure Mode and Effects Analysis (FMEA) approach to assess the risks for patients undergoing Stereotactic Body Radiation Therapy (SBRT) treatments for lesions located in spine and liver in two CyberKnife® Centres.

Methods

The various sub-processes characterizing the SBRT treatment were identified to generate the process trees of both the treatment planning and delivery phases. This analysis drove to the identification and subsequent scoring of the potential failure modes, together with their causes and effects, using the risk probability number (RPN) scoring system. Novel solutions aimed to increase patient safety were accordingly considered.

Results

The process-tree characterising the SBRT treatment planning stage was composed with a total of 48 sub-processes. Similarly, 42 sub-processes were identified in the stage of delivery to liver tumours and 30 in the stage of delivery to spine lesions. All the sub-processes were judged to be potentially prone to one or more failure modes. Nineteen failures (i.e. 5 in treatment planning stage, 5 in the delivery to liver lesions and 9 in the delivery to spine lesions) were considered of high concern in view of the high RPN and/or severity index value.

Conclusions

The analysis of the potential failures, their causes and effects allowed to improve the safety strategies already adopted in the clinical practice with additional measures for optimizing quality management workflow and increasing patient safety.

Reported radiation overexposure accidents worldwide, 1980-2013: a systematic review

BACKGROUND

Radiation overexposure accidents are rare but can have severe long-term health consequences. Although underreporting can be an issue, some extensive literature reviews of reported radiation overexposures have been performed and constitute a sound basis for conclusions on general trends. Building further on this work, we performed a systematic review that completes previous reviews and provides new information on characteristics and trends of reported radiation accidents.

METHODS

We searched publications and reports from MEDLINE, EMBASE, the International Atomic Energy Agency, the International Radiation Protection Association, the United Nations Scientific Committee on the Effects of Atomic Radiation, the United States Nuclear Regulatory Commission, and the Radiation Emergency Assistance Center/Training Site radiation accident registry over 1980-2013. We retrieved the reported overexposure cases, systematically extracted selected information, and performed a descriptive analysis.

RESULTS

297 out of 5189 publications and reports and 194 records from the REAC/TS registry met our eligibility criteria. From these, 634 reported radiation accidents were retrieved, involving 2390 overexposed people, of whom 190 died from their overexposure. The number of reported cases has decreased for all types of radiation use, but the medical one. 64% of retrieved overexposure cases occurred with the use of radiation therapy and fluoroscopy. Additionally, the types of reported accidents differed significantly across regions.

CONCLUSIONS

This review provides an updated and broader view of reported radiation overexposures. It suggests an overall decline in reported radiation overexposures over 1980-2013. The greatest share of reported overexposures occurred in the medical fields using radiation therapy and fluoroscopy; this larger number of reported overexposures accidents indicates the potential need for enhanced quality assurance programs. Our data also highlights variations in characteristics of reported accidents by region. The main limitation of this study is the likely underreporting of radiation overexposures. Ensuring a comprehensive monitoring and reporting of radiation overexposures is paramount to inform and tailor prevention interventions to local needs.

Redesign of process map to increase efficiency: Reducing procedure time in cervical cancer brachytherapy

PURPOSE

To increase intraprocedural efficiency in the use of clinical resources and to decrease planning time for cervical cancer brachytherapy treatments through redesign of the procedure's process map.

METHODS AND MATERIALS

A multidisciplinary team identified all tasks and associated resources involved in cervical cancer brachytherapy in our institution and arranged them in a process map. A redesign of the treatment planning component of the process map was conducted with the goal of minimizing planning time. Planning time was measured on 20 consecutive insertions, of which 10 were performed with standard procedures and 10 with the redesigned process map, and results were compared. Statistical significance (p < 0.05) was measured with a two-tailed t test.

RESULTS

Twelve tasks involved in cervical cancer brachytherapy treatments were identified. The process map showed that in standard procedures, the treatment planning tasks were performed sequentially. The process map was redesigned to specify that contouring and some planning tasks are performed concomitantly. Some quality assurance tasks were reorganized to minimize adverse effects of a possible error on procedure time. Test dry runs followed by live implementation confirmed the applicability of the new process map to clinical conditions. A 29% reduction in planning time (p < 0.01) was observed with the introduction of the redesigned process map.

CONCLUSIONS

A process map for cervical cancer brachytherapy was generated. The treatment planning component of the process map was redesigned, resulting in a 29% decrease in planning time and a streamlining of the quality assurance process.

Results of 1 year of clinical experience with independent dose calculation software for VMAT fields

It is widely accepted that a redundant independent dose calculation (RIDC) must be included in any treatment planning verification procedure. Specifically, volumetric modulated arc therapy (VMAT) technique implies a comprehensive quality assurance (QA) program in which RIDC should be included. In this paper, the results obtained in 1 year of clinical experience are presented. Eclipse from Varian is the treatment planning system (TPS), here in use. RIDC were performed with the commercial software; Diamond^® (PTW) which is capable of calculating VMAT fields. Once the plan is clinically accepted, it is exported via Digital Imaging and Communications in Medicine (DICOM) to RIDC, together with the body contour, and then a point dose calculation is performed, usually at the isocenter. A total of 459 plans were evaluated. The total average deviation was -0.3 ± 1.8% (one standard deviation (1SD)). For higher clearance the plans were grouped by location in: Prostate, pelvis, abdomen, chest, head and neck, brain, stereotactic radiosurgery, lung stereotactic body radiation therapy, and miscellaneous. The highest absolute deviation was -0.8 ± 1.5% corresponding to the prostate. A linear fit between doses calculated by RIDC and by TPS produced a correlation coefficient of 0.9991 and a slope of 1.0023. These results are very close to those obtained in the validation process. This agreement led us to consider this RIDC software as a valuable tool for QA in VMAT plans.

Long term OSLD reader stability in the ACDS level one audit

The Australian Clinical Dosimetry Service (ACDS) has demonstrated the capacity to perform a basic dosimetry audit on all radiotherapy clinics across Australia. During the ACDS’s three and a half year trial the majority of the audits were performed using optically stimulated luminescence dosimeters (OSLD) mailed to facilities for exposure to a reference dose, and then returned to the ACDS for analysis. This technical note investigates the stability of the readout process under the large workload of the national dosimetry audit. The OSLD readout uncertainty contributes to the uncertainty of several terms of the dose calculation equation and is a major source of uncertainty in the audit. The standard deviation of four OSLD readouts was initially established at 0.6 %. Measurements over 13 audit batches—each batch containing 200−400 OSLDs—showed variability (0.5−0.9 %) in the readout standard deviation. These shifts have not yet necessitated a change to the audit scoring levels. However, a standard deviation in OSLD readouts greater than 0.9 % will change the audit scoring levels. We identified mechanical wear on the OSLD readout adapter as a cause of variability in readout uncertainty, however, we cannot rule out other causes. Additionally we observed large fluctuations in the distribution of element correction factors (ECF) for OSLD batches. We conclude that the variability in the width of the ECF distribution from one batch to another is not caused by variability in readout uncertainty, but rather by variations in the OSLD stock.

Characterization of MOSkin detector for in vivo skin dose measurement during megavoltage radiotherapy

In vivo dosimetry is important during radiotherapy to ensure the accuracy of the dose delivered to the treatment volume. A dosimeter should be characterized based on its application before it is used for in vivo dosimetry. In this study, we characterize a new MOSFET‐based detector, the MOSkin detector, on surface for in vivo skin dosimetry. The advantages of the MOSkin detector are its water equivalent depth of measurement of 0.07 mm, small physical size with submicron dosimetric volume, and the ability to provide real‐time readout. A MOSkin detector was calibrated and the reproducibility, linearity, and response over a large dose range to different threshold voltages were determined. Surface dose on solid water phantom was measured using MOSkin detector and compared with Markus ionization chamber and GAFCHROMIC EBT2 film measurements. Dependence in the response of the MOSkin detector on the surface of solid water phantom was also tested for different (i) source to surface distances (SSDs); (ii) field sizes; (iii) surface dose; (iv) radiation incident angles; and (v) wedges. The MOSkin detector showed excellent reproducibility and linearity for dose range of 50 cGy to 300 cGy. The MOSkin detector showed reliable response to different SSDs, field sizes, surface, radiation incident angles, and wedges. The MOSkin detector is suitable for in vivo skin dosimetry.

PACS number: 87.55.Qr

Incident Learning and Failure-Mode-and-Effects-Analysis Guided Safety Initiatives in Radiation Medicine

By combining incident learning and process failure-mode-and-effects-analysis (FMEA) in a structure-process-outcome framework we have created a risk profile for our radiation medicine practice and implemented evidence-based risk-mitigation initiatives focused on patient safety. Based on reactive reviews of incidents reported in our departmental incident-reporting system and proactive FMEA, high safety-risk procedures in our paperless radiation medicine process and latent risk factors were identified. Six initiatives aimed at the mitigation of associated severity, likelihood-of-occurrence, and detectability risks were implemented. These were the standardization of care pathways and toxicity grading, pre-treatment-planning peer review, a policy to thwart delay-rushed processes, an electronic whiteboard to enhance coordination, and the use of six sigma metrics to monitor operational efficiencies. The effectiveness of these initiatives over a 3-years period was assessed using process and outcome specific metrics within the framework of the department structure. There has been a 47% increase in incident-reporting, with no increase in adverse events. Care pathways have been used with greater than 97% clinical compliance rate. The implementation of peer review prior to treatment-planning and use of the whiteboard have provided opportunities for proactive detection and correction of errors. There has been a twofold drop in the occurrence of high-risk procedural delays. Patient treatment start delays are routinely enforced on cases that would have historically been rushed. Z-scores for high-risk procedures have steadily improved from 1.78 to 2.35. The initiatives resulted in sustained reductions of failure-mode risks as measured by a set of evidence-based metrics over a 3-years period. These augment or incorporate many of the published recommendations for patient safety in radiation medicine by translating them to clinical practice.

Application of failure mode and effects analysis (FMEA) to pretreatment phases in tomotherapy

The aim of this paper was the application of the failure mode and effects analysis (FMEA) approach to assess the risks for patients undergoing radiotherapy treatments performed by means of a helical tomotherapy unit. FMEA was applied to the preplanning imaging, volume determination, and treatment planning stages of the tomotherapy process and consisted of three steps: 1) identification of the involved subprocesses; 2) identification and ranking of the potential failure modes, together with their causes and effects, using the risk probability number (RPN) scoring system; and 3) identification of additional safety measures to be proposed for process quality and safety improvement. RPN upper threshold for little concern of risk was set at 125. A total of 74 failure modes were identified: 38 in the stage of preplanning imaging and volume determination, and 36 in the stage of planning. The threshold of 125 for RPN was exceeded in four cases: one case only in the phase of preplanning imaging and volume determination, and three cases in the stage of planning. The most critical failures appeared related to (i) the wrong or missing definition and contouring of the overlapping regions, (ii) the wrong assignment of the overlap priority to each anatomical structure, (iii) the wrong choice of the computed tomography calibration curve for dose calculation, and (iv) the wrong (or not performed) choice of the number of fractions in the planning station. On the basis of these findings, in addition to the safety strategies already adopted in the clinical practice, novel solutions have been proposed for mitigating the risk of these failures and to increase patient safety.

Categorizing accident sequences in the external radiotherapy for risk analysis

Purpose

This study identifies accident sequences from the past accidents in order to help the risk analysis application to the external radiotherapy.

Materials and Methods

This study reviews 59 accidental cases in two retrospective safety analyses that have collected the incidents in the external radiotherapy extensively. Two accident analysis reports that accumulated past incidents are investigated to identify accident sequences including initiating events, failure of safety measures, and consequences. This study classifies the accidents by the treatments stages and sources of errors for initiating events, types of failures in the safety measures, and types of undesirable consequences and the number of affected patients. Then, the accident sequences are grouped into several categories on the basis of similarity of progression. As a result, these cases can be categorized into 14 groups of accident sequence.

Results

The result indicates that risk analysis needs to pay attention to not only the planning stage, but also the calibration stage that is committed prior to the main treatment process. It also shows that human error is the largest contributor to initiating events as well as to the failure of safety measures. This study also illustrates an event tree analysis for an accident sequence initiated in the calibration.

Conclusion

This study is expected to provide sights into the accident sequences for the prospective risk analysis through the review of experiences.

Application of failure mode and effects analysis to treatment planning in scanned proton beam radiotherapy

Background

A multidisciplinary and multi-institutional working group applied the Failure Mode and Effects Analysis (FMEA) approach to the actively scanned proton beam radiotherapy process implemented at CNAO (Centro Nazionale di Adroterapia Oncologica), aiming at preventing accidental exposures to the patient.

Methods

FMEA was applied to the treatment planning stage and consisted of three steps: i) identification of the involved sub-processes; ii) identification and ranking of the potential failure modes, together with their causes and effects, using the risk probability number (RPN) scoring system, iii) identification of additional safety measures to be proposed for process quality and safety improvement. RPN upper threshold for little concern of risk was set at 125.

Results

Thirty-four sub-processes were identified, twenty-two of them were judged to be potentially prone to one or more failure modes. A total of forty-four failure modes were recognized, 52% of them characterized by an RPN score equal to 80 or higher. The threshold of 125 for RPN was exceeded in five cases only. The most critical sub-process appeared related to the delineation and correction of artefacts in planning CT data. Failures associated to that sub-process were inaccurate delineation of the artefacts and incorrect proton stopping power assignment to body regions. Other significant failure modes consisted of an outdated representation of the patient anatomy, an improper selection of beam direction and of the physical beam model or dose calculation grid. The main effects of these failures were represented by wrong dose distribution (i.e. deviating from the planned one) delivered to the patient. Additional strategies for risk mitigation, easily and immediately applicable, consisted of a systematic information collection about any known implanted prosthesis directly from each patient and enforcing a short interval time between CT scan and treatment start. Moreover, (i) the investigation of dedicated CT image reconstruction algorithms, (ii) further evaluation of treatment plan robustness and (iii) implementation of independent methods for dose calculation (such as Monte Carlo simulations) may represent novel solutions to increase patient safety.

Conclusions

FMEA is a useful tool for prospective evaluation of patient safety in proton beam radiotherapy. The application of this method to the treatment planning stage lead to identify strategies for risk mitigation in addition to the safety measures already adopted in clinical practice.

Radiotherapy pre-treatment dose validation: A second verification of monitor units (MU) with a commercial software

Inversely planned intensity-modulated radiotherapy (IMRT) and stereotactic small field radiotherapy should be verified before treatment execution. A second verification is carried out for planned treatments in IMRT and 3D conformal radiotherapy (3D-CRT) using a monitor verification commercial dose calculation management software (DCMS). For the same reference point the ion-chamber measured doses are compared for IMRT plans. DCMS (Diamond) computes dose based on modified Clarkson integration, accounting for multi-leaf collimators (MLC) transmission and measured collimator scatter factors. DCMS was validated with treatment planning system (TPS) (Eclipse 6.5 Version, Varian, USA) separately. Treatment plans computed from TPS are exported to DCMS using DICOM interface. Doses are re-calculated at selected points for fields delivered to IMRT phantom (IBA Scanditronix Wellhofer) in high-energy linac (Clinac 2300 CD, Varian). Doses measured at central axis, for the same points using CC13 (0.13 cc) ion chamber with Dose 1 Electrometer (Scanditronix Wellhofer) are compared with calculated data on DCMS and TPS. The data of 53 IMRT patients with fields ranging from 5 to 9 are reported. The computed dose for selected monitor units (MU) by Diamond showed good agreement with planned doses by TPS. DCMS dose prediction matched well in 3D-CRT forward plans (0.8 ± 1.3%, n = 37) and in IMRT inverse plans (-0.1 ± 2.2%, n = 37). Ion chamber measurements agreed well with Eclipse planned doses (-2.1 ± 2.0%, n = 53) and re-calculated DCMS doses (-1.5 ± 2.6%, n = 37) in phantom. DCMS dose validation is in reasonable agreement with TPS. DCMS calculations corroborate well with ionometric measured doses in most of the treatment plans.

Recommendations for safer radiotherapy: what's the message?

Radiotherapy, with close to a million courses delivered per year in North America, is a very safe and effective intervention for a devastating disease. However, although rare, several deeply regrettable incidents have occurred in radiotherapy and have rightly been the subject of considerable public interest. Partly in response to reports of these incidents a variety of authoritative organizations across the globe has harnessed the expertise amongst their members in attempts to identify the measures that will make radiotherapy safer. While the intentions of all these organizations are clearly good it is challenging for the health care providers in the clinic to know where to start with so much advice coming from so many directions. Through a mapping exercise we have identified commonalities between recommendations made in seven authoritative documents and identified those issues most frequently cited. The documents reviewed contain a total of 117 recommendations. Using the 37 recommendations in "Towards Safer Radiotherapy" as the initial base layer, recommendations in the other documents were mapped, adding to the base layer to accommodate all the recommendations from the additional six documents as necessary. This mapping exercise resulted in the distillation of the original 117 recommendations down to 61 unique recommendations. Twelve topics were identified in three or more of the documents as being pertinent to the improvement of patient safety in radiotherapy. They are, in order of most to least cited: training, staffing, documentation, incident learning, communication, check lists, quality control and preventive maintenance, dosimetric audit, accreditation, minimizing interruptions, prospective risk assessment, and safety culture. This analysis provides guidance for the selection of those activities most likely to enhance safety and quality in radiotherapy based on the frequency of citation in selected recent authoritative literature.

Medical physics staffing for radiation oncology: a decade of experience in Ontario, Canada

The January 2010 articles in The New York Times generated intense focus on patient safety in radiation treatment, with physics staffing identified frequently as a critical factor for consistent quality assurance. The purpose of this work is to review our experience with medical physics staffing, and to propose a transparent and flexible staffing algorithm for general use. Guided by documented times required per routine procedure, we have developed a robust algorithm to estimate physics staffing needs according to center‐specific workload for medical physicists and associated support staff, in a manner we believe is adaptable to an evolving radiotherapy practice. We calculate requirements for each staffing type based on caseload, equipment inventory, quality assurance, educational programs, and administration. Average per‐case staffing ratios were also determined for larger‐scale human resource planning and used to model staffing needs for Ontario, Canada over the next 10 years. The workload specific algorithm was tested through a survey of Canadian cancer centers. For center‐specific human resource planning, we propose a grid of coefficients addressing specific workload factors for each staff group. For larger scale forecasting of human resource requirements, values of 260, 700, 300, 600, 1200, and 2000 treated cases per full‐time equivalent (FTE) were determined for medical physicists, physics assistants, dosimetrists, electronics technologists, mechanical technologists, and information technology specialists, respectively.

PACS numbers: 87.55.N‐, 87.55.Qr