CONTEMPORARY COLLECTIVE EFFECTIVE DOSE TO THE POPULATION FROM X-RAY AND NUCLEAR MEDICINE EXAMINATIONS-CHANGES OVER LAST 10 YEARS IN FINLAND.

Contemporary collective effective doses to the population from x-ray and nuclear medicine examinations in Finland in 2018 was estimated. The estimated effective dose per caput from x-ray examinations increased from year 2008 to 2018 respectively from 0.45 mSv to 0.72 mSv and from nuclear medicine examinations from 0.03 mSv to 0.04 mSv. The proportional dose due to CT examinations of the total collective effective dose from all x-ray examinations increased from 58% in 2008 to 70% in 2018 and the dose did not change substantially in total when new conversion factors were applied. The collective effective dose from conventional plain radiography did not change substantially during the last ten years while the new (ICRP 103) tissue weighting factors were taken into use in 2018, however frequencies of examinations in total decreased. The collective effective dose from CT in nuclear medicine tripled between 2009 and 2018.

CONTEMPORARY RADIATION DOSES IN INTERVENTIONAL CARDIOLOGY: A NATIONWIDE STUDY OF PATIENT SKIN DOSES IN FINLAND.

In contemporary interventional cardiology, for typical elderly patients, the most severe radiation-related harm to patients can be considered to come from skin exposures. In this paper, maximum local skin doses in cardiological procedures are explored with Gafchromic film dosimetry. Film and reader calibrations and reading were performed at the Secondary Standards Dosimetry Laboratory of the Radiation and Nuclear Safety Authority (STUK), and data were gathered from seven hospitals in Finland. As alert levels for early transient erythema, 200 Gycm2 kerma area product (KAP) and 2000 mGy air kerma levels for transcatheter aortic valve implantations (TAVI) procedures are proposed. The largest doses were measured in TAVI (4158.8 mGy) and percutaneous coronary interventions (PCI) (941.68 mGy). Accuracies of the GE DoseWatch and Siemens CareMonitor skin dose estimates were reasonable, but more results are needed to reliably assess and validate the tools' capabilities and reliabilities. Uncertainty of the Gafchromic dosimetry was estimated as 9.1% for a calibration with seven data points and 19.3% for a calibration with five data points.

CONTEMPORARY RADIATION DOSES IN INTERVENTIONAL CARDIOLOGY: A NATIONWIDE STUDY OF PATIENT DOSES IN FINLAND.

The amount of interventional procedures such as percutaneous coronary intervention (PCI), transcatheter aortic valve implantation (TAVI), pacemaker implantation (PI) and ablations has increased within the previous decade. Simultaneously, novel fluoroscopy mainframes enable lower radiation doses for patients and operators. Therefore, there is a need to update the existing diagnostic reference levels (DRLs) and propose new ones for common or recently introduced procedures. We sought to assess patient radiation doses in interventional cardiology in a large sample from seven hospitals across Finland between 2014 and 2016. Data were used to set updated national DRLs for coronary angiographies (kerma-air product (KAP) 30 Gycm2) and PCIs (KAP 75 cm2), and novel levels for PIs (KAP 3.5 Gycm2), atrial fibrillation ablation procedures (KAP 25 Gycm2) and TAVI (KAP 90 Gycm2). Tentative KAP values were set for implantations of cardiac resynchronization therapy devices (CRT, KAP 22 Gycm2), electrophysiological treatment of atrioventricular nodal re-entry tachycardia (6 Gycm2) and atrial flutter procedures (KAP 16 Gycm2). The values for TAVI and CRT device implantation are published for the first time on national level. Dose from image acquisition (cine) constitutes the major part of the total dose in coronary and atrial fibrillation ablation procedures. For TAVI, patient weight is a good predictor of patient dose.

Medical imaging dose optimisation from ground up: expert opinion of an international summit.

As in any medical intervention, there is either a known or an anticipated benefit to the patient from undergoing a medical imaging procedure. This benefit is generally significant, as demonstrated by the manner in which medical imaging has transformed clinical medicine. At the same time, when it comes to imaging that deploys ionising radiation, there is a potential associated risk from radiation. Radiation risk has been recognised as a key liability in the practice of medical imaging, creating a motivation for radiation dose optimisation. The level of radiation dose and risk in imaging varies but is generally low. Thus, from the epidemiological perspective, this makes the estimation of the precise level of associated risk highly uncertain. However, in spite of the low magnitude and high uncertainty of this risk, its possibility cannot easily be refuted. Therefore, given the moral obligation of healthcare providers, 'first, do no harm,' there is an ethical obligation to mitigate this risk. Precisely how to achieve this goal scientifically and practically within a coherent system has been an open question. To address this need, in 2016, the International Atomic Energy Agency (IAEA) organised a summit to clarify the role of Diagnostic Reference Levels to optimise imaging dose, summarised into an initial report (Järvinen et al 2017 Journal of Medical Imaging 4 031214). Through a consensus building exercise, the summit further concluded that the imaging optimisation goal goes beyond dose alone, and should include image quality as a means to include both the benefit and the safety of the exam. The present, second report details the deliberation of the summit on imaging optimisation.

Patient safety in external beam radiotherapy, results of the ACCIRAD project: Recommendations for radiotherapy institutions and national authorities on assessing risks and analysing adverse error-events and near misses.

The ACCIRAD project, commissioned by the European Commission (EC) to develop guidelines for risk analysis of accidental and unintended exposures in external beam radiotherapy (EBRT), was completed in the year 2014. In 2015, the "General guidelines on risk management in external beam radiotherapy" were published as EC report Radiation Protection (RP)-181. The present document is the third and final report of the findings from the ACCIRAD project. The main aim of this paper is to describe the key features of the risk management process and to provide general guidelines for radiotherapy departments and national authorities on risk assessment and analysis of adverse error-events and near misses. The recommendations provided here and in EC report RP-181 are aimed at promoting the harmonisation of risk management systems across Europe, improving patient safety, and enabling more reliable inter-country comparisons.

Feasibility of setting up generic alert levels for maximum skin dose in fluoroscopically guided procedures.

PURPOSE: The feasibility of setting-up generic, hospital-independent dose alert levels to initiate vigilance on possible skin injuries in interventional procedures was studied for three high-dose procedures (chemoembolization (TACE) of the liver, neuro-embolization (NE) and percutaneous coronary intervention (PCI)) in 9 European countries. METHODS: Gafchromic® films and thermoluminescent dosimeters (TLD) were used to determine the Maximum Skin Dose (MSD). Correlation of the online dose indicators (fluoroscopy time, kerma- or dose-area product (KAP or DAP) and cumulative air kerma at interventional reference point (Ka,r)) with MSD was evaluated and used to establish the alert levels corresponding to a MSD of 2 Gy and 5 Gy. The uncertainties of alert levels in terms of DAP and Ka,r, and uncertainty of MSD were calculated. RESULTS: About 20-30% of all MSD values exceeded 2 Gy while only 2-6% exceeded 5 Gy. The correlations suggest that both DAP and Ka,r can be used as a dose indicator for alert levels (Pearson correlation coefficient p mostly >0.8), while fluoroscopy time is not suitable (p mostly <0.6). Generic alert levels based on DAP (Gy cm2) were suggested for MSD of both 2 Gy and 5 Gy (for 5 Gy: TACE 750, PCI 250 and NE 400). The suggested levels are close to the lowest values published in several other studies. The uncertainty of the MSD was estimated to be around 10-15% and of hospital-specific skin dose alert levels about 20-30% (with coverage factor k = 1). CONCLUSIONS: The generic alert levels are feasible for some cases but should be used with caution, only as the first approximation, while hospital-specific alert levels are preferred as the final approach.

Patient dose monitoring and the use of diagnostic reference levels for the optimization of protection in medical imaging: current status and challenges worldwide.

Optimization is one of the key concepts of radiation protection in medical imaging. In practice, it involves compromising between the image quality and dose to the patient; the dose should not be higher than necessary to achieve an image quality (or diagnostic information) needed for the clinical task. Monitoring patient dose is a key requirement toward optimization. The concept of diagnostic reference level (DRL) was introduced by the International Commission on Radiological Protection as a practical tool for optimization. Unfortunately, this concept has not been applied consistently worldwide. To review the current strengths and weaknesses worldwide and to promote improvements, the International Atomic Energy Agency organized a Technical Meeting on patient dose monitoring and the use of DRLs on May 2016. This paper reports a summary of the findings and conclusions from the meeting. The strengths and weaknesses were generally different in less-developed countries compared with developed countries. Possible improvements were suggested in six areas: human resources and responsibilities, training, safety and quality culture, regulations, funding, and tools and methods. An overall conclusion was that radiation protection requires a patient-centric approach and a transfer from purely reactive to increasingly proactive optimization, whereby the best outcome is expected from good teamwork.

Excess of Radiation Burden for Young Testicular Cancer Patients using Automatic Exposure Control and Contrast Agent on Whole-body Computed Tomography Imaging.

BACKGROUND: The aim of the study was to assess patient dose from whole-body computed tomography (CT) in association with patient size, automatic exposure control (AEC) and intravenous (IV) contrast agent. PATIENTS AND METHODS: Sixty-five testicular cancer patients (mean age 28 years) underwent altogether 279 whole-body CT scans from April 2000 to April 2011. The mean number of repeated examinations was 4.3. The GE LightSpeed 16 equipped with AEC and the Siemens Plus 4 CT scanners were used for imaging. Whole-body scans were performed with (216) and without (63) IV contrast. The ImPACT software was used to determine the effective and organ doses. RESULTS: Patient doses were independent (p < 0.41) of patient size when the Plus 4 device (mean 7.4 mSv, SD 1.7 mSv) was used, but with the LightSpeed 16 AEC device, the dose (mean 14 mSv, SD 4.6 mSv) increased significantly (p < 0.001) with waist cirfumference. Imaging with the IV contrast agent caused significantly higher (13% Plus 4, 35% LightSpeed 16) exposure than non-contrast imaging (p < 0.001). CONCLUSIONS: Great caution on the use of IV contrast agent and careful set-up of the AEC modulation parameters is recommended to avoid excessive radiation exposure on the whole-body CT imaging of young patients.

Patient safety in external beam radiotherapy, results of the ACCIRAD project: Current status of proactive risk assessment, reactive analysis of events, and reporting and learning systems in Europe.

PURPOSE: To describe the current status of implementation of European directives for risk management in radiotherapy and to assess variability in risk management in the following areas: 1) in-country regulatory framework; 2) proactive risk assessment; (3) reactive analysis of events; and (4) reporting and learning systems. MATERIAL AND METHODS: The original data were collected as part of the ACCIRAD project through two online surveys. RESULTS: Risk assessment criteria are closely associated with quality assurance programs. Only 9/32 responding countries (28%) with national regulations reported clear "requirements" for proactive risk assessment and/or reactive risk analysis, with wide variability in assessment methods. Reporting of adverse error events is mandatory in most (70%) but not all surveyed countries. CONCLUSIONS: Most European countries have taken steps to implement European directives designed to reduce the probability and magnitude of accidents in radiotherapy. Variability between countries is substantial in terms of legal frameworks, tools used to conduct proactive risk assessment and reactive analysis of events, and in the reporting and learning systems utilized. These findings underscore the need for greater harmonisation in common terminology, classification and reporting practices across Europe to improve patient safety and to enable more reliable inter-country comparisons.

Cancer Death Risk Related to Radiation Exposure from Computed Tomography Scanning Among Testicular Cancer Patients.

BACKGROUND: A study of the computed tomography (CT) imaging related effective doses and radiation-related cancer death risk. PATIENTS AND METHODS: Estimate effective doses were computed from CT scans of testicular cancer patients treated and followed-up in Turku University Hospital, South Western Finland. Association between effective doses from follow-up CT scans and radiation-induced cancer death was examined using United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) 2008 formula. RESULTS: Mean effective dose per CT abdomen was 9.32 (standard deviation, SD 3.89) mSv and for whole-body CT it was 14.24 (SD 6.84) mSv. During follow-up of 6 years, the patients were estimated to undergo 12 to 14 abdominal/whole-body CTs and the corresponding risk estimates were 0.11 and 1.14, respectively. The risk of estimated radiation-induced cancer deaths (RICD in %) computed for mean effective doses was lower in patients diagnosed at older age, being 0.61 for 10-19 years age and 0.04 for 40-49 years age at the diagnosis. CONCLUSION: Patient radiation exposure in CT imaging is associated with the type of CT device and imaging protocols, which should be periodically updated and reviewed to minimize individual exposure. Using the UNSCEAR modelling 2 % risk for radiation related cancer death was attributed to diagnostic exposure of study patients. Age at the diagnosis was associated with CT imaging related radiation exposure. The highest exposure was estimated to the youngest patients.

Patient safety in external beam radiotherapy - guidelines on risk assessment and analysis of adverse error-events and near misses: introducing the ACCIRAD project.

In 2011 the European Commission launched a tender to develop guidelines for risk analysis of accidental and unintended exposures in external beam radiotherapy. This tender was awarded to a consortium of 6 institutions, including the ESTRO, in late 2011. The project, denominated "ACCIRAD", recently finished the data collection phase. Data were collected by surveys administered in 38 European countries. Results indicate non-uniform implementation of event registration and classification, as well as incomplete or zero implementation of risk assessment and events analysis. Based on the survey results and analysis thereof, project leaders are currently drafting proposed guidelines entitled "Guidelines for patient safety in external beam radiotherapy - Guidelines on risk assessment and analysis of adverse-error events and near misses". The present article describes the aims and current status of the project, including results of the surveys.

How can a cost/benefit ratio be optimized for an output measurement program of external photon radiotherapy beams?

We estimated cost/benefit ratios for different quality control programs of radiation output measurements of medical linear accelerators. The cost/benefit ratios of quality control (QC) programs (a combination of output measurement time interval and measurement action levels) were defined as workload divided by achievable dose accuracy. Dose accuracy was assumed to be inversely proportional to the 99% confidence limit of shifts of total treatment doses and workload as inversely proportional to the output measurement time interval. Our previously reported method was used to estimate the distribution of shifts of total treatment doses due to changes in accelerator radiation output (Gy/MU). The confidence limits of dose shifts were estimated for different QC programs and for different levels of output measurement reproducibility. Output shifts used in the estimations had previously been observed for four linear accelerators over 5 years. We observed that the cost/benefit ratio increases remarkably when the output measurement time interval is less than 1 month. The ratio depends strongly on the action levels and reproducibility of the QC measurements. Improvement of these factors optimizes the cost/benefit ratio by a factor of several times. The most cost-effective output measurement time interval to achieve 99% confidence limits of ±2, ±2.5 or ±3% for dose shifts ranged from 0.25 month to as much as 6 months depending on the factors given above and the intended accuracy level. It is several times more cost effective to increase dose accuracy by lowering the action levels of the QC measurements and by attempting to improve their reproducibility than by simply shortening the time interval of the output measurements. Methods improving utilization and interpretation of the results of the QC measurements play a key role in further optimization of cost/benefit ratios in dosimetric QC.

Clinical audits and regulatory inspections--double efforts and expenses for radiation protection?

BACKGROUND: Clinical audit as a systematic examination of medical procedures improves the quality and outcome of patient care. The purpose of a regulatory inspection is to check and verify that the operation and facilities are in full conformance with all legal requirements. PURPOSE: To examine the content of the clinical audits and regulatory inspections of radiological procedures and whether these overlap, and to evaluate the costs to radiological units. MATERIAL AND METHODS: Clinical audits were carried out at each imaging unit of Helsinki University Hospital (HUS) Medical Imaging Center in Finland in 2004 and 2005. The regulatory inspections were carried out after the clinical audits from 2005 to late 2007. The contents of the clinical audit and inspection reports were analyzed statistically and by content analysis. The results of the audits and the inspections were compared to analyze the overlaps, differences, and costs. RESULTS: The validity and conditions of the safety license, lines of authority, and responsibilities for the use of radiation and patient doses caused by different examinations were evaluated in both audits and inspections. The coverage and frequency of quality control procedures were monitored in every audit and inspection, but inspectors, in addition, checked radiation output. The costs of clinical audit and inspection were under 20 cents per radiological procedure. The auditors gave 98 recommendations, while inspectors gave 62 recommendations and 25 requirements. In clinical audits most of the recommendations concerned guidelines for examining a patient. In the inspections most recommendations were in the category of quality assurance activities. CONCLUSION: The clinical audits and regulatory inspections were cheap and had few overlapping topics, but several differences were apparent: in clinical audits, a broader and deeper view of the clinical procedures was taken by comparison with good practices, while regulatory inspections have mainly verified conformance to basic regulatory requirements.

A direct method for air kerma-length product measurement in CT for verification of dose display calibrations.

The dose display values of computed tomography (CT) devices are used for patient dose estimation and as a tool for optimisation. Therefore, the dose display value accuracy should be verified. In practice, this means doing measurements in the standard phantoms and comparing results with the dose display values. The traditional method for measuring CT dose enables measurements only for one axial rotation, and there has not been a method for measuring the dose of a complete helical scan sequence. In this work, a new method for a direct measurement of the dose of a complete helical sequence is developed and tested. Results show that this method is practical and that the accuracy of the modern CT devices seems to be at the sufficient level, so that the dose display values can be used for patient dose estimation.

Portable TL dosemeter--ESD phantom combination for chest and lumbar spine radiography.

A thermoluminescence dosemeter (TLD)-entrance surface dose (ESD) phantom combination was calibrated in terms of air-kerma in IEC RQR X-ray radiation qualities between 50 and 150 kV. The ESD phantom was designed and constructed as a part of the work. With the combination, air-kermas were measured for four radiological examinations (two chest and two lumbar spine examinations in two hospitals), and converted to ESDa using Monte-Carlo calculated BSF data tabulated for different tube voltages, filtrations and beam diameters at 1 m distance. The results agreed with the ionisation-chamber measurements within the reported overall uncertainty of the TLD method. In the calibration, the ESD phantom can be replaced by the ISO water slab phantom unaffecting the reported overall uncertainty. Backscatter-related parameters for the ISO water slab phantom and the newly designed ESD phantom were determined for the IEC RQR qualities used in the secondary standard dosimetry laboratory of STUK at 1 m distance, including an approximate Hp(10)/Hp(0.07) ratio.

Accuracy of central axis dose calculations for photon external radiotherapy beams in Finland: the quality of local beam data and the use of averaged data.

PURPOSE: The accuracy of central axis dose calculation was evaluated for 48 photon beams from 28 linear accelerators at nine centres in Finland. In addition, inter-accelerator consistency of beam data was evaluated for Varian Clinac 600 CDs and 2100 CDs, and averaged data sets were generated for output factors (OFs) and percentage depth doses (PDDs). The averaged data sets obtained were used to identify potential dosimetry reasons for local errors. MATERIALS AND METHODS: Agreement between measured and calculated doses was determined at isocentre at 10 cm depth in water for nine different sized open square and rectangular fields. Averaged OFs were determined for nominal energies of 4, 6, 10, 15 and 18 MV both at d(max) and at a 10-cm depth. In order to develop a function for the OF data, OFs for square fields were parameterised through empirical model fitting. The feasibility of a simple equivalent square collimator formula was also evaluated for the presentation of OFs for rectangular fields. Averaged PDDs were determined at a 10-cm depth. RESULTS: The difference between measured and calculated doses exceeded +/-3%, +/-2% and +/-1% for 3, 6 and 35 of the investigated 48 beams, respectively. The differences were due to errors observed in both OFs and depth dose data. When the agreement between dose calculation and measurement was within +/-1%, inter-accelerator differences in OFs were within +/-1.0% at both the depth of dose maximum and at 10 cm for Clinac 600 CDs and also for 2100 CDs. Differences in PDDs were within +/-1.2%. CONCLUSIONS: The importance of quality control for beam data was demonstrated by showing significant errors in measured data. For Clinac 600 and 2100 CDs, the quality control can be accurately performed by comparing local data to averaged reference data. Robust averaged data sets were obtained for 6, 15 and 18 MV beams of Clinac 2100 CDs.

The influence of output measurement time interval and tolerance on treatment dose deviation in photon external beam radiotherapy.

A method was developed to estimate the spread of treatment doses due to a given output measurement, time interval and action level in external photon beam radiotherapy. The method exploits empirical or simulated data of both output stability and the reproducibility of the absolute output measurements and relative constancy checks. The spread of an output and the probability that an output is outside the predefined tolerance limits were estimated for different quality control procedures of the output. The use of internationally recommended output measurement intervals of 3, 1 and 0.25 months together with an action level of +/-2% results in the out-of-tolerance probability up to 49%, 26% and 3%, respectively, while the output is kept within up to +/-5.5%, +/-4.0% and +/-2.0%, respectively. It was also found that the action level has more prominent relative influence than the measurement interval. The results suggest that similar treatment quality can be achieved by doubling the output measurement time interval and lowering the action level from +/-2% to +/-1.5% and the constancy check action level from +/-3% to +/-2%.

Analysis of quality control data of eight modern radiotherapy linear accelerators: the short- and long-term behaviours of the outputs and the reproducibility of quality control measurements.

Quality control (QC) data of radiotherapy linear accelerators, collected by Helsinki University Central Hospital between the years 2000 and 2004, were analysed. The goal was to provide information for the evaluation and elaboration of QC of accelerator outputs and to propose a method for QC data analysis. Short- and long-term drifts in outputs were quantified by fitting empirical mathematical models to the QC measurements. Normally, long-term drifts were well (< or =1%) modelled by either a straight line or a single-exponential function. A drift of 2% occurred in 18 +/- 12 months. The shortest drift times of only 2-3 months were observed for some new accelerators just after the commissioning but they stabilized during the first 2-3 years. The short-term reproducibility and the long-term stability of local constancy checks, carried out with a sealed plane parallel ion chamber, were also estimated by fitting empirical models to the QC measurements. The reproducibility was 0.2-0.5% depending on the positioning practice of a device. Long-term instabilities of about 0.3%/month were observed for some checking devices. The reproducibility of local absorbed dose measurements was estimated to be about 0.5%. The proposed empirical model fitting of QC data facilitates the recognition of erroneous QC measurements and abnormal output behaviour, caused by malfunctions, offering a tool to improve dose control.