Report of IRPA task group on issues and actions taken in response to the change in eye lens dose limit.

In 2018, the International Radiation Protection Association (IRPA) established its third task group (TG) on the implementation of the eye lens dose limit. To contribute to sharing experience and raising awareness within the radiation protection community about protection of workers in exposure of the lens of the eye, the TG conducted a questionnaire survey and analysed the responses. This paper provides an overview of the results of the questionnaire.

Overdiagnosis and overimaging: an ethical issue for radiological protection.

AIMS AND OBJECTIVES: This study aimed to analyse the key factors that influence the overimaging using X-ray such as self-referral, defensive medicine and duplicate imaging studies and to emphasize the ethical problem that derives from it. MATERIALS AND METHODS: In this study, we focused on the more frequent sources of overdiagnosis such as the total-body CT, proposed in the form of screening in both public and private sector, the choice of the most sensitive test for each pathology such as pulmonary embolism, ultrasound investigations mostly of the thyroid and of the prostate and MR examinations, especially of the musculoskeletal system. RESULTS: The direct follow of overdiagnosis and overimaging is the increase in the risk of contrast media infusion, radiant damage, and costs in the worldwide healthcare system. The theme of the costs of overdiagnosis is strongly related to inappropriate or poorly appropriate imaging examination. CONCLUSIONS: We underline the ethical imperatives of trust and right conduct, because the major ethical problems in radiology emerge in the justification of medical exposures of patients in the practice. A close cooperation and collaboration across all the physicians responsible for patient care in requiring imaging examination is also important, balancing possible ionizing radiation disadvantages and patient benefits in terms of care.

Towards a strategic research agenda for social sciences and humanities in radiological protection.

Reflecting a change in funding strategies for European research projects, and a commitment to the idea of responsible research and innovation in radiological protection (RP), a collective of research institutes and universities have developed a prospective Strategic Research Agenda (SRA) for Social Sciences and Humanities (SSH) in radiological protection. This is the first time such a research agenda has been proposed. This paper identifies six research lines of interest and concern: (1) Effects of social, psychological and economic aspects on RP behaviour; (2) Holistic approaches to the governance of radiological risks; (3) Responsible research and innovation in RP; (4) Stakeholder engagement and participatory processes in RP research, development, policy and practice; (5) Risk communication; and (6) RP cultures. These topics were developed through broad stakeholder consultation, in conjunction with activities carried out in the framework of various projects and initiatives (EU H2020 CONCERT programme, the EU FP7 projects OPERRA, PREPARE and EAGLE, the 2015-2018 RICOMET series of conferences, and the 2014 and 2016 International Symposia on Ethics of Environmental Health); as well as through dialogues with members of the European radiation protection research communities. The six research lines open opportunities to integrate a range of key social and ethical considerations into RP, thereby expanding research opportunities and programmes and fostering collaborative approaches to research and innovation.

Should the automatic exposure control system of CT be disabled when scanning patients with endoaortic stents or mechanical heart valves? A phantom study.

OBJECTIVES: To estimate the impact of endoaortic stents/mechanical heart valves on the output of an automatic exposure control (AEC) system and CT radiation dose. METHODS: In this phantom study, seven stents and two valves were scanned with varying tube voltage (80/100/120 kVp), AEC activation (enabled/disabled) and prosthesis (present/absent), for a total of 540 scans. For each prosthesis, the dose-length product (DLP) was compared between scans with the AEC enabled and disabled. Percentage confidence levels for differences due to the prosthesis were calculated. RESULTS: Differences between results with the AEC enabled and disabled were not statistically significant (p ≥ 0.059). In the comparison with and without the prosthesis, DLP was unchanged at 80 kVp and 100 kVp, while a slight increase was observed at 120 kVp. The radiation dose varied from 1.8 mGy to 2.4 mGy without the prosthesis and from 1.8 mGy to 2.5 mGy with the prosthesis (confidence level 37-100%). CONCLUSIONS: The effect of the prosthesis on the AEC system was negligible and not clinically relevant. Therefore, disabling the AEC system when scanning these patients is not likely to provide a benefit. KEY POINTS: • CT-AEC system is not impaired in patients with endoaortic prostheses/heart valves. • Negligible differences may be observed only at 120 kVp. • Disabling the AEC system in these patients is not recommended.

Report of IRPA task group on the impact of the eye lens dose limits.

In 2012 IRPA established a task group (TG) to identify key issues in the implementation of the revised eye lens dose limit. The TG reported its conclusions in 2013. In January 2015, IRPA asked the TG to review progress with the implementation of the recommendations from the early report and to collate current practitioner experience. This report presents the results of a survey on the view of the IRPA professionals on the new limit to the lens of the eye and on the wider issue of tissue reactions. Recommendations derived from the survey are presented. This report was approved by IRPA Executive Council on 31 January 2017.

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.

Collimator angle influence on dose distribution optimization for vertebral metastases using volumetric modulated arc therapy.

PURPOSE: The cylindrical symmetry of vertebrae favors the use of volumetric modulated are therapy in generating a dose "hole" on the center of the vertebrae limiting the dose to the spinal cord. The authors have evaluated if collimator angle is a significant parameter for dose distribution optimization in vertebral metastases. METHODS: Three patients with one-three vertebrae involved were considered. Twenty-one differently optimized plans (nine single-arc and 12 double-arc plans) were performed, testing various collimator angle positions. Clinical target volume was defined as the whole vertebrae, excluding the spinal cord canal. The planning target volume (PTV) was defined as CTV+5 mm. Dose prescription was 5 x 4 Gy(2) with normalization to PTV mean dose. The dose at 1 cm(3) of spinal cord was limited to 11.5Gy. RESULTS: The best plans in terms of target coverage and spinal cord sparing were achieved by two arcs and Arcl-80 degrees and Arc2-280 degrees collimator angles for all the cases considered (i.e., leaf travel parallel to the spinal cord primary orientation). If one arc is used, only 80 degrees reached the objectives. CONCLUSIONS: This study demonstrated the role of collimation rotation for the vertebrae metastasis irradiation, with the leaf travel parallel to the spinal cord primary orientation to be better than other solutions. Thus, optimal choice of collimator angle increases the optimization freedom to shape a desired dose distribution.

IRPA GUIDANCE-THE ROLE OF STAKEHOLDERS, RADIATION PROTECTION CULTURE AND ETHICS IN EMERGENCY PREPAREDNESS.

The International Radiation Protection Association, IRPA, promotes the excellence in radiation protection by providing benchmarks of good practice, as well as enhancing professional competence and networking. In relation to emergency situations, including post-accident and recovery phases, a key issue is the ability of the system of protection to take a broader view of societal values, along with the need to develop processes which support and respect the dignity and well-being of the affected populations. Regarding the various situations of radiation exposure, IRPA's activities include aspects which can contribute to medical preparedness in radiation emergencies, focusing particularly on stakeholder engagement, radiation protection culture, the ethical dimensions of radiation protection and public understanding of risks. As it is a combination of science, experience, ethical and social values, radiation protection culture promotes radiation risk awareness in the different exposure situations, including the implementation of countermeasures in radiation and nuclear emergencies and post-accident situations, with attention also on medical countermeasures.

The role played by stakeholders in the public debate that brought Italy out of the club of nuclear energy producers.

In 1964, Italy was the fourth largest world producer of electricity generated by nuclear reactors, second in Europe only to United Kingdom. In subsequent years, various controversial political events contributed towards drastically slowing down the development of the Italian national nuclear program. The 1986 Chernobyl Nuclear Power Plant accident, which caused a public outcry all over Europe, had particularly serious repercussions in Italy. In a controversial referendum, held in November 1987, Italian citizens voted to repeal three laws promoting the installation of nuclear power plants (NPP) on Italian soil and allowing the National Institute for Electrical Energy (ENEL) to participate in the construction of NPP's abroad. This work analyzes the reasons for that decision and the communication strategies of the stakeholders that took part in the public debate on nuclear energy during the weeks following the Chernobyl accident. Drawing from the methodologies used in media studies, a quantitative and qualitative analysis of two leading Italian newspapers was performed. The results reveal that a variety of stakeholders, upholding different values and interests, took part in the debate. There being no tradition of a public dialogue and participation in Italy, the debate was polarized to a "yes/no choice," which eventually caused Italy to abandon the production of nuclear power for civilian use.

Modelling urinary excretion of molybdenum after oral and intravenous administration of stable tracers.

An extensive study using stable isotopes of molybdenum as tracers was undertaken to investigate intestinal uptake, systemic kinetics and urinary excretion of molybdenum in healthy human volunteers. In total 63 experiments with 17 volunteers were performed administering the tracers in different chemical forms and measuring their concentrations in blood plasma and urine samples by means of activation analysis and mass spectrometry. Molybdenum was eliminated very rapidly from the circulation. The amount eliminated via the renal pathway was observed to be dependent on several factors, such as form and modality of administration and also the total amount of circulating molybdenum. The fact that the urinary excretion patterns diverged significantly from the current predictions of the International Commission on Radiological Protection model might be relevant when using the model for retrospective intake assessments in case of an accident. On the basis of the experimental data, a more realistic compartmental structure has been presented.

EXTRAPOLATION TECHNIQUES EVALUATING 24 HOURS OF AVERAGE ELECTROMAGNETIC FIELD EMITTED BY RADIO BASE STATION INSTALLATIONS: SPECTRUM ANALYZER MEASUREMENTS OF LTE AND UMTS SIGNALS.

International and national organizations have formulated guidelines establishing limits for occupational and residential electromagnetic field (EMF) exposure at high-frequency fields. Italian legislation fixed 20 V/m as a limit for public protection from exposure to EMFs in the frequency range 0.1 MHz-3 GHz and 6 V/m as a reference level. Recently, the law was changed and the reference level must now be evaluated as the 24-hour average value, instead of the previous highest 6 minutes in a day. The law refers to a technical guide (CEI 211-7/E published in 2013) for the extrapolation techniques that public authorities have to use when assessing exposure for compliance with limits. In this work, we present measurements carried out with a vectorial spectrum analyzer to identify technical critical aspects in these extrapolation techniques, when applied to UMTS and LTE signals. We focused also on finding a good balance between statistically significant values and logistic managements in control activity, as the signal trend in situ is not known. Measurements were repeated several times over several months and for different mobile companies. The outcome presented in this article allowed us to evaluate the reliability of the extrapolation results obtained and to have a starting point for defining operating procedures.

MASS MEDIA COMMUNICATION OF EMERGENCY ISSUES AND COUNTERMEASURES IN A NUCLEAR ACCIDENT: FUKUSHIMA REPORTING IN EUROPEAN NEWSPAPERS.

This paper presents the results of a large study of 1340 articles published by two major newspapers in six European countries (Belgium, Italy, Norway, Slovenia, Spain and Russia) in the first 2 months after the Fukushima Daiichi nuclear disaster. The focus of the analysis is on the application and overall impact of protective actions, both during the emergency phase and later, how the newspapers describe those actions, which differences were apparent between countries and what recommendations can be extracted in order to improve general communication about these issues. A clear lesson is that, even under uncertainty and recognising limitations, responsible authorities need to provide transparent, clear and understandable information to the public and the mass media right from the beginning of the early phase of any nuclear emergency. Clear, concise messages should be given. Mass media could play a key role in reassuring the public if the countermeasures are clearly explained.

Angular dependence of the TL reading of thin alpha-Al2O3:C dosemeters exposed to different beta spectra.

The angular dependence of the thermoluminescent (TL) signal of thin alpha-Al2O3:C dosemeters was investigated for a series of beta-emitting radionuclides commonly employed in nuclear medicine and characterised by different mean energies (99Tc, 177Lu, 90Sr/90Y and 90Y). Irradiations were performed in a controlled geometry, using a properly designed irradiator intended to realistically reproduce the situation of exposure of hospital personnel to beta-emitting pharmaceuticals. Under the conditions of extended source and short source to detector distance, the TL signal of thin alpha-Al2O3:C layers per unit irradiation time was observed to be independent on the angle of incidence within acceptable limits, particularly for those radionuclides with maximum energy >500 keV. This property may be easily explained by using simple physical considerations, such as the limited thickness of the dosemeters. The results confirm that these detectors are suitable for beta-ray extremity dose measurements, when the photon contribution is negligible, as in the case considered.

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.

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.

Application of failure mode and effects analysis to intraoperative radiation therapy using mobile electron linear accelerators.

PURPOSE: Failure mode and effects analysis (FMEA) represents a prospective approach for risk assessment. A multidisciplinary working group of the Italian Association for Medical Physics applied FMEA to electron beam intraoperative radiation therapy (IORT) delivered using mobile linear accelerators, aiming at preventing accidental exposures to the patient. METHODS AND MATERIALS: FMEA was applied to the IORT process, for the stages of the treatment delivery and verification, 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, based on the product of three parameters (severity, frequency of occurrence and detectability, each ranging from 1 to 10); 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. RESULTS: Twenty-four subprocesses were identified. Ten potential failure modes were found and scored, in terms of RPN, in the range of 42-216. The most critical failure modes consisted of internal shield misalignment, wrong Monitor Unit calculation and incorrect data entry at treatment console. Potential causes of failure included shield displacement, human errors, such as underestimation of CTV extension, mainly because of lack of adequate training and time pressures, failure in the communication between operators, and machine malfunctioning. The main effects of failure were represented by CTV underdose, wrong dose distribution and/or delivery, unintended normal tissue irradiation. As additional safety measures, the utilization of a dedicated staff for IORT, double-checking of MU calculation and data entry and finally implementation of in vivo dosimetry were suggested. CONCLUSIONS: FMEA appeared as a useful tool for prospective evaluation of patient safety in radiotherapy. The application of this method to IORT lead to identify three safety measures for risk mitigation.

Nonlinear compartmental model of 18F-choline.

INTRODUCTION: This work develops a compartmental model of (18)F-choline in order to evaluate its biokinetics and so to describe the temporal variation of the radiopharmaceuticals' uptake in and clearance from organs and tissues. METHODS: Ten patients were considered in this study. A commercially available tool for compartmental analysis (SAAM II) was used to model the values of activity concentrations in organs and tissues obtained from PET images or from measurements of collected blood and urine samples. RESULTS: A linear compartmental model of the biokinetics of the radiopharmaceutical was initially developed. It features a central compartment (blood) exchanging with organs. The structure describes explicitly liver, kidneys, spleen, blood and urinary excretion. The linear model tended to overestimate systematically the activity in the liver and in the kidney compartments in the first 20 min post-administration. A nonlinear process of kinetic saturation was considered, according to the typical Michaelis-Menten kinetics. Therefore nonlinear equations were added to describe the flux of (18)F-choline from blood to liver and from blood to kidneys. The nonlinear model showed a tendency for improvement in the description of the activity in liver and kidneys, but not for the urine. CONCLUSIONS: The simple linear model presented is not able to properly describe the biokinetics of (18)F-choline as measured in prostatic cancer patients. The introduction of nonlinear kinetics, although based on physiologically plausible assumptions, resulted in nonsignificant improvements of the model predictive power.

A compartmental model for biokinetics and dosimetry of 18F-choline in prostate cancer patients.

UNLABELLED: PET with (18)F-choline ((18)F-FCH) is used in the diagnosis of prostate cancer and its recurrences. In this work, biodistribution data from a recent study conducted at Skåne University Hospital Malmö were used for the development of a biokinetic and dosimetric model. METHODS: The biodistribution of (18)F-FCH was followed for 10 patients using PET up to 4 h after administration. Activity concentrations in blood and urine samples were also determined. A compartmental model structure was developed, and values of the model parameters were obtained for each single patient and for a reference patient using a population kinetic approach. Radiation doses to the organs were determined using computational (voxel) phantoms for the determination of the S factors. RESULTS: The model structure consists of a central exchange compartment (blood), 2 compartments each for the liver and kidneys, 1 for spleen, 1 for urinary bladder, and 1 generic compartment accounting for the remaining material. The model can successfully describe the individual patients' data. The parameters showing the greatest interindividual variations are the blood volume (the clearance process is rapid, and early blood data are not available for several patients) and the transfer out from liver (the physical half-life of (18)F is too short to follow this long-term process with the necessary accuracy). The organs receiving the highest doses are the kidneys (reference patient, 0.079 mGy/MBq; individual values, 0.033-0.105 mGy/MBq) and the liver (reference patient, 0.062 mGy/MBq; individual values, 0.036-0.082 mGy/MBq). The dose to the urinary bladder wall of the reference patient varies between 0.017 and 0.030 mGy/MBq, depending on the assumptions on bladder voiding. CONCLUSION: The model gives a satisfactory description of the biodistribution of (18)F-FCH and realistic estimates of the radiation dose received by the patients.

Spatial distribution of beta extremity doses in nuclear medicine: a feasibility study with thin alpha-Al2O3:C TLDs.

Exposures to the extremities have increased due to new therapeutic protocols involving beta sources. In this study, thermoluminescent dosimeters based on alpha-Al(2)O(3):C were used to map the dose distribution to the extremities of physicians and paramedical personnel handling beta emitters. The results showed a strong inhomogeneous dose distribution between different phalanxes, fingers and hands of all the investigated subjects, without an indication of systematic trends in the dose patterns. Consequently, conventional dosimetric practices, based on the use of wrist or ring dosimeters, may be not suitable for providing reliable assessments of the inhomogeneous doses received at the fingertip.

Radiation Physics for Nuclear Medicine

The field of nuclear medicine is expandingrapidly, with the development of exciting new diagnostic methodsand treatments relevant to a variety of diseases. This growth isclosely associated with significant advances in radiation physics.In this book, acknowledged experts explain the basic principles ofradiation physics in relation to nuclear medicine and examineimportant novel approaches in the field. The first section isdevoted to what might be termed the "building blocks" of nuclearmedicine, including the mechanisms of interaction between radiationand matter and Monte Carlo codes. In subsequent sections, radiationsources for medical applications, radiopharmaceutical developmentand production, and radiation detectors are discussed in detail.New frontiers are then explored, including the PET magnifyingprobe, improved algorithms for image reconstruction, biokineticmodels, and voxel phantoms for internal dosimetry. Both traineesand experienced practitioners and researchers will find this bookto be an invaluable source of up-to-date information.