Justification in clinical radiological practice: a survey among staff of five London hospitals

This study represents a survey performed among staff who, according to the Ionising Radiation (Medical Exposures) Regulations of 2000 (IRMER), are responsible for justifying radiological examinations in the UK. The aim of the survey is to map the current situation regarding knowledge of risks from X-ray exposures and the criteria used for their justification. An anonymous electronic questionnaire was emailed to 219 radiologists and radiographers of five National Health Service hospitals. The questions were designed to investigate the way the sample group defines/assesses risk and benefit when justifying medical exposures, and to test their knowledge on radiation doses, risk communication, and on relevant national legislation. The majority of the respondents are aware of the relevant legislation/guidelines. Patient's medical condition, age and sex, and alternative techniques using less or no ionising radiation are the main criteria used for justification. However, when estimating the effective dose of various examinations in chest radiograph equivalents, the majority of the responses were incorrect. Although there is good knowledge of legislation around justification of medical exposures, there seems to be a lack of knowledge on radiation doses and risks among IRMER practitioners.     

Management of patient dose in radiology in the UK

Programmes to manage patient dose in radiology are becoming a higher priority as the number of imaging examinations and the proportion of higher dose computed tomography (CT) and complex interventional procedures all continue to rise. Such programmes have a number of components and their implementation in UK hospitals, which have been developing such programmes over two decades, is described. As part of any programme to manage patient doses, elements should be in place for both justification and optimisation. The system for justification needs to be robust in order to minimise the number of unnecessary procedures and requires the provision of training in radiation protection for medical and other staff to ensure that they understand the risks. Optimisation of X-ray techniques requires performance tests on equipment at installation and regularly thereafter, linked to surveys of patient doses. Confirming the performance of the available options on fluoroscopy and CT equipment is essential and the information obtained should be available to radiographers and radiologists, so they can make informed choices in developing imaging protocols. Patient doses should be compared with diagnostic reference levels set in terms of measured dose quantities to allow the identification of equipment that is giving higher doses. Taking the next step of analysing results to determine the reasons for high doses is crucial and requires a link with the equipment performance tests and an understanding of the underlying physics. Medical physics services play an important role at the hub of the dose management programme for carrying out tests, organising surveys, making recommendations on optimisation strategies and training other staff in radiation protection, performance testing and dose reduction. Programmes for management of patient doses in UK hospitals were first set up in the late 1980s by medical physicists and have been developed since that time to keep pace with the developments in technology. Regional departments serving several hundred or a thousand X-ray units form the model followed in most regions. This paper describes the form of patient dose management programmes in the UK. It also gives guidance that might be useful to others that are now embarking on the same journey.     

Optimisation of X-ray examinations in Lithuania: start of implementation in mammography

Optimisation of medical X-ray examinations is very important for the enhancement of the reliability of the examination and for the reduction of the radiation dose to patients. Results of investigations of doses to patients during mammography using thermoluminescence dosemeters at different hospitals are presented together with a brief overview of the situation for mammography in Lithuania. It is shown that the entrance surface air kerma varies in a broad range and differed from hospital to hospital. Nevertheless the calculated values of average glandular dose (AGD) for a 'standard' breast being relatively high were comparable with those (3.2 mGy per exposure at net optical density 1.4) currently accepted by international authorities. Differences in AGD values evaluated at different hospitals demonstrate the existing potential for optimisation of the mammography screening procedures. The results of this investigation will be included in a database for patient doses in Lithuania and used for establishing a national reference dose level for mammography. Currently, reference levels recommended by international authorities are used in Lithuania.     

Patient exposure in medical X-ray imaging in Europe

Patients are exposed to X rays when undergoing medical examinations in diagnostic radiology. Exposure data acquired and assessed in Germany for the year 1997 resulted in a mean annual effective dose of 2 +/- 0.5 mSv per head of the population, thereby reaching or exceeding the average level of environmental radiation in many cases. The underlying frequency of medical X-ray examinations was approximately 136 million, i.e. approximately 1.7 examinations annually per head of the population. For comparison, corresponding data of other countries were extracted from the UNSCEAR 2000 report or originate from the literature. Data analysis shows significant differences in national radiological practices and a very uneven distribution of patient doses amongst the world population. The mean annual effective dose per head of the population varies by up to a factor of 60 between health care level I and IV countries, and still by a factor of approximately 6 within health care level I countries. While projection radiography has succeeded in reducing dose consumption, computed tomography and radiological interventions have given rise to a significant growth of patient exposure, and interventional radiology can even exceed thresholds for deterministic radiation effects. Patient exposure is further shown to result from misadministration and retakes of X-ray examinations, usually not registered, as well as from technical failures of X-ray facilities, which can cause significantly enhanced exposure times. Corresponding data are presented and comments are made on the international situation of non-harmonised data collection on patient exposure as well as of parameters affecting the assessment of exposure and risk.     

Priorities in optimisation of medical X-ray imaging--a contribution to the debate

A simplistic approach to optimising medical imaging is to use the lowest effective dose to the patient that does not jeopardise a correct diagnosis. With limited resources and over 1000 different types of X-ray examinations, it is not always easy to set the right priorities and to decide how to perform the optimisation. Recent research shows that the 'Rose model' for the detection of specific structures does not hold for realistic backgrounds. A reasonable conclusion regarding methods for optimisation is therefore not to use contrast-detail phantoms. Phantoms producing clinically realistic background images or real clinical images-modified with respect to quantum noise levels-are preferred. The images should be evaluated using visual grading or receiver operating characteristic methods. The quality of many common X-ray investigations, performed with projection techniques, is not limited by quantum noise. For these, the radiation dose to the patient can be lowered without seriously affecting the outcome of the detection task. For computed tomography (CT) investigations, the obscuring effect of anatomical structures and anatomical noise is less pronounced than in projection techniques. For CT, true optimisation in terms of a trade-off between radiation dose and image quality is therefore more likely to be effective. Both the number of CT examinations performed per year and the effective dose per examination are increasing owing to the technical advances in CT--jointly leading to a steady increase in the collective dose from CT examinations. Moreover, the smaller influence of the anatomical background in CT gives a high correlation between detection tasks and radiation dose. Thus, a reasonable view to take on which examinations to optimise is to give priority to CT examinations. The recommended distribution of a full working week for optimisation, based on the relative lifetime risk of lethal cancer from diagnostic X rays and the total collective dose from CT, is to use three out of five days to optimise CT examinations, of which one day should be devoted to paediatric CT.     

Assessment of patient organ dose in CT virtual colonoscopy for bowel cancer screening

Justification and optimisation form the basic elements for the radiological protection of individuals for medical exposures. Justification includes the assessment of patient organ doses from which radiation risks are deduced. Medical radiation exposures are justified only in the case of a sufficient net benefit. For screening examinations, such as CT virtual colonoscopy, this implies that patient organ doses should be relatively low to minimise the radiation detriment. Image quality should be sufficient to maximise the potential diagnostic benefits. The Medical Exposures Directive places special attention on medical exposures as part of health screening programmes and examinations involving high individual doses to the patient, both of which apply to CT virtual colonoscopy. Technical factors were recorded for a series of patients having virtual colonoscopy on a CT scanner. In addition, the dose-length product was assessed. Patient organ doses were deduced using a CT dose calculation program. The typical effective dose was 7.5 mSv for male patients and 10.2 mSv for female patients. The effective dose is higher for female patients, as some gender-specific organs are irradiated during virtual colonoscopy. Each patient has two series of scans resulting in doses of 15 mSv for male patients and 20 mSv for female patients.     

Results of a patient dose survey on diagnostic radiology in Lithuania

One of the most effective means towards optimisation of radiation protection for patients undergoing radiodiagnostic examinations are the diagnostic reference levels. In order to ensure the effective use of these levels, they have to be set properly. National characteristics, such as the conditions of the radiological equipments, the training of the staff, the availability of quality assurance systems, etc., have to be taken into account when these levels are established. Measurements under real conditions were considered as the best tools to achieve these reference levels. With an aim to establish the Lithuanian national diagnostic reference levels, the nationwide survey of entrance surface doses received by the patients during the most typical X-ray examinations has been performed. The most common types of examinations, such as chest PA, skull PA and LAT, abdomen AP, lumbar spine AP and LAT, thorax spine AP and LAT, and hip joint AP, were included in the list of procedures under consideration. Hospitals of different size and levels using different X-ray machines were represented in the survey. The standard thermoluminescence dosemeter techniques with pellets attached to the skin of the patient in the centre of radiation field were applied. The data were analysed statistically, and the averages and 75th percentile were calculated. The results show that the Lithuanian diagnostic reference levels might be rather close to the ones promoted by the International Atomic Energy Agency and the European Commission.     

Estimating cancer risks to adults undergoing body CT examinations

The purpose of the study is to estimate cancer risks from the amount of radiation used to perform body computed tomography (CT) examination. The ImPACT CT Patient Dosimetry Calculator was used to compute values of organ doses for adult body CT examinations. The radiation used to perform each examination was quantified by the dose-length product (DLP). Patient organ doses were converted into corresponding age and sex dependent cancer risks using data from BEIR VII. Results are presented for cancer risks per unit DLP and unit effective dose for 11 sensitive organs, as well as estimates of the contribution from 'other organs'. For patients who differ from a standard sized adult, correction factors based on the patient weight and antero-posterior dimension are provided to adjust organ doses and the corresponding risks. At constant incident radiation intensity, for CT examinations that include the chest, risks for females are markedly higher than those for males, whereas for examinations that include the pelvis, risks in males were slightly higher than those in females. In abdominal CT scans, risks for males and female patients are very similar. For abdominal CT scans, increasing the patient age from 20 to 80 resulted in a reduction in patient risks of nearly a factor of 5. The average cancer risk for chest/abdomen/pelvis CT examinations was ～26 % higher than the cancer risk caused by 'sensitive organs'. Doses and radiation risks in 80 kg adults were ～10 % lower than those in 70 kg patients. Cancer risks in body CT can be estimated from the examination DLP by accounting for sex, age, as well as patient physical characteristics.     

First results on patient dose measurements from conventional diagnostic radiology procedures in Serbia and Montenegro

The objective of this work is to assess patient doses for the most frequent X-ray examinations for the first time in Serbia and Montenegro. A total of 510 procedures for 11 different examination categories in 3 general hospitals were analysed. Mean and median entrance surface air kerma (ESAK) and kerma area product (KAP) values followed by mean effective doses were reported. Using X-ray tube output data, ESAK for each radiographic examination was calculated, as well as the effective dose for each patient. Except for chest PA examination, all estimated doses are less than stated European and International Atomic Energy Agency (IAEA) reference levels for simple radiographic examinations. For complex examinations involving fluoroscopy and radiography total KAP was measured and contributions from fluoroscopy and radiography were assessed. The study of KAP confirms that the dose level for complex fluoroscopy investigations is closely related to the technique and individual patient variation in terms of fluoroscopy time and number of radiography exposures. The obtained values are comparable to those reported in the UK. Survey data are aimed aid development of a national quality control and radiation protection programme for medical exposures.     

Number of X-ray examinations performed on paediatric and geriatric patients compared with adult patients

The age of the patient is of prime importance when assessing the radiological risk to patients due to medical X-ray exposures and the total detriment to the population due to radiodiagnostics. In order to take into account the age-specific radiosensitivity, three age groups are considered: children, adults and the elderly. In this work, the relative number of examinations carried out on paediatric and geriatric patients is established, compared with adult patients, for radiodiagnostics as a whole, for dental and medical radiology, for 8 radiological modalities as well as for 40 types of X-ray examinations. The relative numbers of X-ray examinations are determined based on the corresponding age distributions of patients and that of the general population. Two broad groups of X-ray examinations may be defined. Group A comprises conventional radiography, fluoroscopy and computed tomography; for this group a paediatric patient undergoes half the number of examinations as that of an adult, and a geriatric patient undergoes 2.5 times more. Group B comprises angiography and interventional procedures; for this group a paediatric patient undergoes a one-fourth of the number of examinations carried out on an adult, and a geriatric patient undergoes five times more.     

Evaluation of exposure parameters in plain radiography: a comparative study with European guidelines

Typical distribution of exposure parameters in plain radiography is unknown in Portugal. This study aims to identify exposure parameters that are being used in plain radiography in the Lisbon area and to compare the collected data with European references [Commission of European Communities (CEC) guidelines]. The results show that in four examinations (skull, chest, lumbar spine and pelvis), there is a strong tendency of using exposure times above the European recommendation. The X-ray tube potential values (in kV) are below the recommended values from CEC guidelines. This study shows that at a local level (Lisbon region), radiographic practice does not comply with CEC guidelines concerning exposure techniques. Further national/local studies are recommended with the objective to improve exposure optimisation and technical procedures in plain radiography. This study also suggests the need to establish national/local diagnostic reference levels and to proceed to effective measurements for exposure optimisation.     

Implementation of DRLs in the UK

This article describes the system of regulation and practical guidance that has been developed in the UK for implementing the requirement in the EC Medical Exposure Directive that all Member States shall promote the establishment and use of diagnostic reference levels (DRLs) for medical X-ray examinations. In particular, it describes the role of two national patient dose databases maintained by NRPB, which provide important sources of information on which formally adopted numerical values for 'national DRLs' will be based. One database deals with radiographic and fluoroscopic examinations and the recommended 'national reference doses' from the latest review of this database are discussed. The other database deals specifically with computed tomography (CT) examinations, which now account for 50% of the collective dose to the UK population from all medical X rays and are consequently of particular radiation protection concern. The first analysis of this CT database is still underway, but some encouraging indications of a reduction in patient dose for some CT examinations are reported. Progress in formally adopting numerical values for 'national DRLs', as required by the UK regulations, and the provision of authoritative guidance on the implementation of DRLs at the local level, are also discussed.     

Characterization of workplaces in interventional radiology using active dosemeters ALARA OD

Because of progressive development and extended use of interventional radiology (IR) procedures it is highly recommended that all individuals involved in the process should be aware of the potential for both stochastic and deterministic effects due to occupational exposure. IR procedures are performed in such a manner that certain number of medical staff are always needed near the patient, near the X-ray unit. The new challenge to regular radiation protection is to ensure 'safe' working environment in such radiation X-ray field geometry. In this work the patient is physically regarded as a secondary radiation source emitting scattered X-rays. Passive dosemeters will give us clear data only about the monthly integrated occupational dose; there is concern over the frequency and duration, actual pattern of receiving this dose. We have developed active electronic dosemeter (AED) device, which provides additional dosimetry data about the frequency and duration of professional low level X-ray exposure burden.     

Health Canada's approach to manage risks to populations at risk during a radiological emergency

The approach that Health Canada uses to manage risks to individuals and to populations who might be exposed to ionising radiation is based upon the risk management paradigm. The paradigm differs little between an emergency and a non-emergency situations. In both events, technical experts assess the risk by determining the exposure to the source of radiation. They usually calculate the radiation dose and then assess the potential for any health effects. The initial technical assessments often use scoping calculations. The calculations for children recognise that they are smaller and have different metabolic rates and different behaviour from adults. However, most rigorous quantitative models for dosimetry do not differentiate between children and adults. The risk assessments that were conducted to evaluate the contamination of Canadians who were in London during the Litvenenko poisoning are a good example to illustrate this general approach. The scoping risk assessment concluded that the risks to children and adults were low. No Canadian children were exposed to polonium during this event and, to date, there have been no radiation emergencies in Canada where children have been exposed to a significant source of radiation. Therefore, the comparisons between theory and practice are very limited and conclusions are drawn from international experience and other incidents or sources of radiation exposure such as radon and medical exposures.     

Evaluation of personal doses associated with the use of mobile X-rays in a Brazilian hospital

In Brazilian public hospitals, the number of patients needing assistance is often much greater than the capacity of the hospital. In such situations, medical procedures are performed as quickly as possible, and mobile X-ray equipment is used intensively. This equipment is used for several types of examination, in different areas of the hospital. During the examination procedure, apart from the radiology technicians involved, there are always other people in the room who are also exposed to the radiation scattered by the patient. The objective of this study was to determine the exposure, due to the use of mobile X-ray equipment, of hospital personnel, divided into two categories named 'monitored' and 'non-monitored'. Evaluation of 413 radiographies was performed, the vast majority of them being chest examinations (75 %). During the procedures, specific information was collected to allow measurement in simulated situations. Air kerma rates were measured at different distances from the mobile X-ray equipment using an ionisation chamber and an acrylic phantom with dimensions of 30×30×15 cm(3). From the results, it was possible to estimate the personal dose equivalent received by the individuals in the room during the procedure and to determine the dose maps associated with the use of the mobile X-ray equipment. The results obtained in this study were in accordance with dose limits, but some observed situations were considered critical.     

Evaluation of patient exposure in computerised tomogram in Poland

The increasing number of computerised tomography (CT) procedures performed in Poland in recent years has resulted in a growing contribution of these examinations to the whole exposure of the population to ionising radiation from medical sources. (The number of CT examinations in Poland was 170,000 in 1995 and 460,000 in 1999.) An evaluation is presented of doses to patients in CT examinations performed with different types of CT unit. To evaluate the exposure to patients dose linear product (DLP) was measured using a NOMEX dosemeter with a pencil chamber (PTW, Frieburg) and the cylindrical PMMA phantoms 'head' and 'body'. CTDI values were evaluated according to current methodology as described in European Guidelines (EUR 16262). The measurements were performed for seven types of CT unit made by different companies. The CTDI values were also compared to reference levels recommended by IAEA. In conclusion it was found that the value of collective effective dose (2200 man.Sv), has increased in Poland nearly 4 times in comparison to 1995, whereas the number of CT examinations increased nearly 3 times in this period. For most of the 'controlled' CT scanners the values of CTDI in head procedures are near to or higher than the IAEA Reference Level (50 mGy); this can result from the protocols, which are chosen without a dose analysis.     

Accreditation in radiation protection for cardiologists and interventionalists

Training in radiation protection is widely recognised as one of the basic components of optimisation programmes for medical exposures. Occupational and patient radiation risks in interventional radiology can be quite high and international bodies have shown concern on this item. Following recommendations of the International Commission on Radiological Protection and in accordance with the European Directive on medical exposures, some initiatives for training in radiation protection took place in Spain and Luxembourg. These provided practitioners of interventional radiology adequate theoretical and practical training in radiation protection. The main outcome of the pilot courses organised to this end is discussed, concluding its suitability to implement the European Directive in practice.     

Determination of the dose to persons assisting when X-radiation is used in medicine, dentistry and veterinary medicine

During medical X-ray examinations of patients, humans as well as animals, voluntarily assisting persons are frequently needed in order to calm down the patient or animal. Typical exposure situations have been identified and measurements were performed in the fields of scattered X-rays. The personal dose equivalent H(p)(10) for persons assisting knowingly and willingly in X-ray examinations in dentistry, and human and veterinary medicine was measured. The typical dose values, measured above the protective lead apron, are in the order of a few microsieverts.     

A review of the scientific basis for radiation protection of the patient

The use of ionising radiation in medicine is the single largest man-made source of population exposure. Individual and collective doses to patients arising from the medical use of ionising radiations continue to rise significantly year on year. This is due to the increasing use of medical imaging procedures in modern healthcare systems as well as the continued development of new high dose techniques. This paper reviews the scientific basis for the principles of radiation protection as defined by the International Commission on Radiological Protection. These principles attempt to include exposures arising from both medical and non-medical applications within a common framework and have evolved over many years and changing socio-economic considerations. In particular, the concepts of justification and ALARA (doses should be as low as reasonably achievable), which underpin the principles for medical exposures are assessed in terms of their applicability to the scientific process and relevance to a rapidly changing technologically-led healthcare system. Radiation protection is an integral component of patient safety in medical practices and needs to be evidence based and amenable to the scientific process. The limitations imposed by the existing philosophy of radiation protection to the development of a quantitative framework for adequately assessing the performance of medical imaging systems are highlighted. In particular, medical practitioners will require quantitative guidance as to the risk-benefits arising from modern X-ray imaging methods if they are to make rational judgements as to the applicability of modern high-dose techniques to particular diagnostic and therapeutic tasks. At present such guidance is variable due to the lack of a rational framework for assessing the clinical impact of medical imaging techniques. The possible integration of radiation protection concepts into fundamental bio-medical imaging research activities is discussed.