[en] Over the course of several meetings the HERCA-Working Group (WG) 'Medical Applications' has discussed the exposure of asymptomatic individuals in health care. In particular, the discussions focused on the issue of the early detection of severe diseases, by use of X-rays, for those who do not present with symptoms. An important and established example is the use of X-ray mammography to detect early breast cancer and this has traditionally been referred to as screening. An emerging application is the use of computed tomography in a range of circumstances, some of which may be better described as a separate category of medical exposure as they are neither diagnostic nor screening in the accepted sense. The discussions have indicated that it is pivotal to clearly define the relevant terms generally applied and to clearly differentiate these terms from diagnostic examinations used in health care. In this context, it is important to note, that the revision of the Euratom Basic Safety Standards (Euratom BSS) Directive is under way and addresses in particular medical radiological procedures on asymptomatic individuals, intended to be performed for early detection of disease (Draft Proposal 29 September 2011 Article 54). Hereby, two types of examinations of asymptomatic individuals, (that in some cases have both been referred to as screening) are addressed: (1) exposures as part of screening programmes and (2) exposures associated with individual health assessment. On adoption, this directive will have significant implications for and a substantial impact on the work of the radiation protection authorities in Europe. In this position paper the WG 'Medical Applications' proposes a clear distinction between screening and radiological procedures as part of an individual health assessment and highlights special requirements for the latter. Finally, the impact on the work of radiation protection authorities in Europe is addressed

[en] The target group of the German mammography screening program, conducted according to the European guidelines, is clearly defined: all women aged 50 to 69 years without evidence of breast cancer are invited to screening mammography every two years. In the present study the question was raised whether breast cancer screening by means of mammography is - from the point of view of radiation hygiene - justified also for women under 50 years of age. Based on current radio-epidemiological breast cancer studies, the excess lifetime risk (ELR) to incur or die from breast cancer of a 40, 45 and 50 year old woman was assessed. Different risk models were used to estimate the radiation risk, e.g. models given for the 'Life Span Study' of the atomic bomb survivors and the risk model given in the recent Biological Effects of Ionizing Radiation (BEIR) VII report. The benefit risk ratio was defined as the ratio of the number of 'saved lives' due to screening to the number of deaths due to 'radiation induced breast cancer'. All estimations were based on the assumption that screening is taking place up to the age of 69 years, with screening examinations being performed annually up to the age of 50 and every two years from the age of 50 onwards. The glandular dose per two-view mammography investigation was assumed to be 4 mGy. The benefit due to mammography screening was assumed to be 25% for all age groups. Assuming screening from the age of 40 or 45 years, the ELR of breast cancer is on average about 3.5 or 2 times as high compared to the ELR associated with screening starting from the age of 50 years. In comparison to the benefit risk ratio, which results for women participating in a mammography screening from the age of 50 years, the benefit risk ratio for women starting with screening already from the age of 40 or 45 years is reduced by a factor of 3 or 2. With the present data - with regard to both, the benefit and the radiation risk - it appears not to be justified to expose women from the age of 40 years to the additional radiation exposure associated with a mammography screening. (orig.)

[en] Purpose: To evaluate the clinical value of diffusion-weighted magnetic resonance imaging (DW-MRI) to monitor response of primary carcinoma of the rectum to preoperative chemoradiation by measuring tumor apparent diffusion coefficient (ADC). Materials and methods: Diffusion data of nine patients undergoing preoperative combined chemoradiation for clinical staged T3, N_0-2, M₀ carcinoma of the rectum were analyzed. Diffusion-weighted echo-planar MR images were obtained prior to and at specified intervals during chemoradiation and ADCs calculated from acquired tumor images. Results: Comparison of mean ADC and cumulative radiation dose showed a significant decrease of mean ADC at the 2nd (P=0.028), 3rd (P=0.012), and 4th (P=0.008) weeks of treatment. Cytotoxic edema and fibrosis were considered as reasons for ADC decrease. Conclusion: This study demonstrated tumor ADC changes via detection of therapy-induced alterations in tumor water mobility. Our results indicate that diffusion-weighted imaging may be a valuable clinical tool to diagnose the early stage of radiation-induced fibrosis

[en] The introduction of positron emission tomography (PET)/magnetic resonance (MR) systems into medical practice in the foreseeable future may not only lead to a gain in clinical diagnosis compared to PET/computed tomography (CT) imaging due to the superior soft-tissue contrast of the MR technology but can also substantially reduce exposure of patients to ionizing radiation. On the other hand, there are also risks and health effects associated with the use of diagnostic MR devices that have to be considered carefully. This review article summarizes biophysical and biological aspects, which are of relevance for the assessment of health effects related to the exposure of patients to both ionizing radiation in PET and magnetic and electromagnetic fields in MR. On this basis, some considerations concerning the justification and optimization of PET/MR examinations are presented - as far as this is possible at this very early stage. Current safety standards do not take into account synergistic effects of ionizing radiation and magnetic and electromagnetic fields. In the light of the developing PET/MR technology, there is an urgent need to investigate this aspect in more detail for exposure levels that will occur at PET/MR systems. (orig.)

[en] Purpose: Accelerated partial breast radiotherapy with low-energy photons from a miniature X-ray machine is undergoing a randomized clinical trial (Targeted Intra-operative Radiation Therapy [TARGIT]) in a selected subgroup of patients treated with breast-conserving surgery. The steep radial dose gradient implies reduced tumor cell control with increasing depth in the tumor bed. The purpose was to compare the expected risk of local recurrence in this nonuniform radiation field with that after conventional external beam radiotherapy. Methods and Materials: The relative biologic effectiveness of low-energy photons was modeled using the linear-quadratic formalism including repair of sublethal lesions during protracted irradiation. Doses of 50-kV X-rays (Intrabeam) were converted to equivalent fractionated doses, EQD2, as function of depth in the tumor bed. The probability of local control was estimated using a logistic dose-response relationship fitted to clinical data from fractionated radiotherapy. Results: The model calculations show that, for a cohort of patients, the increase in local control in the high-dose region near the applicator partly compensates the reduction of local control at greater distances. Thus a 'sphere of equivalence' exists within which the risk of recurrence is equal to that after external fractionated radiotherapy. The spatial distribution of recurrences inside this sphere will be different from that after conventional radiotherapy. Conclusions: A novel target volume concept is presented here. The incidence of recurrences arising in the tumor bed around the excised tumor will test the validity of this concept and the efficacy of the treatment. Recurrences elsewhere will have implications for the rationale of TARGIT

[en] Technical developments in both magnetic resonance imaging (MRI) and computed tomography (CT) have helped to reduce scan times and expedited the development of dynamic contrast-enhanced (DCE) imaging techniques. Since the temporal change of the image signal following the administration of a diffusible, extracellular contrast agent (CA) is related to the local blood supply and the extravasation of the CA into the interstitial space, DCE imaging can be used to assess tissue microvasculature and microcirculation. It is the aim of this review to summarize the biophysical and tracer kinetic principles underlying this emerging imaging technique offering great potential for non-invasive characterization of tumour angiogenesis. In the first part, the relevant contrast mechanisms are presented that form the basis to relate signal variations measured by serial CT and MRI to local tissue concentrations of the administered CA. In the second part, the concepts most widely used for tracer kinetic modelling of concentration-time courses derived from measured DCE image data sets are described in a consistent and unified manner to highlight their particular structure and assumptions as well as the relationships among them. Finally, the concepts presented are exemplified by the analysis of representative DCE data as well as discussed with respect to present and future applications in cancer diagnosis and therapy. Depending on the specific protocol used for the acquisition of DCE image data and the particular model applied for tracer kinetic analysis of the derived concentration-time courses, different aspects of tumour angiogenesis can be quantified in terms of well-defined physiological tissue parameters. DCE imaging offers promising prospects for improved tumour diagnosis, individualization of cancer treatment as well as the evaluation of novel therapeutic concepts in preclinical and early-stage clinical trials. (orig.)

[en] Tissue perfusion is frequently determined from dynamic contrast-enhanced CT or MRI image series by means of the steepest slope method. It was thus the aim of this study to systematically evaluate the reliability of this analysis method on the basis of simulated tissue curves. 9600 tissue curves were simulated for four noise levels, three sampling intervals and a wide range of physiological parameters using an axially distributed reference model and subsequently analysed by the steepest slope method. Perfusion is systematically underestimated with errors becoming larger with increasing perfusion and decreasing intravascular volume. For curves sampled after rapid contrast injection with a temporal resolution of 0.72 s, the bias was less than 23% when the mean residence time of tracer molecules in the intravascular distribution space was greater than 6 s. Increasing the sampling interval and the noise level substantially reduces the accuracy and precision of estimates, respectively. The steepest slope method allows absolute quantification of tissue perfusion in a computationally simple and numerically robust manner. The achievable degree of accuracy and precision is considered to be adequate for most clinical applications. (orig.)

[en] X-ray procedures have a substantial impact not only on patient care but also on man-made radiation exposure. Since a reliable risk-benefit analysis of medical X-rays can only be performed for diagnosis-related groups of patients, we determined specific exposure data for patients with the ten most common types of cancer. For all patients with the considered cancers undergoing medical X-ray procedures in a maximum-care hospital between 2000 and 2005, patient- and examination-specific data were retrieved from the hospital/radiology information system. From this data, the cumulative 5-year effective dose was estimated for each patient as well as the mean annual effective dose per patient and the mean patient observation time for each cancer site. In total, 151,439 radiographic, fluoroscopic, and CT procedures, carried out in 15,866 cancer patients (age, 62 ± 13 years), were evaluated. The mean 5-year cumulative dose varied between 8.6 mSv (prostate cancer) and 68.8 mSv (pancreas cancer). Due to an increasing use of CT scans, the mean annual effective dose per patient increased from 13.6 to 18.2 mSv during the 6-year period. Combining the results obtained in this study for a particular hospital with cancer incidence data for Germany, we estimated that cancer patients having X-ray studies constitute at least 1% of the population but receive more than 10% of the total effective dose related to all medical X-ray procedures performed nationwide per year. A large fraction of this dose is radiobiologically ineffective due to the reduced life expectancy of cancer patients.

[en] On 5 December 2013, the Council of the European Union adopted Council Directive 2013/59/Euratom laying down basic safety standards for protection against the dangers arising from exposure to ionising radiation.1 Member States have to transpose the new Basic Safety Standards Directive (BSS Directive) into their national legal systems by 6 February 2018 at the latest. At the 13. meeting of the Board of HERCA (BoH) in Vilnius in June 2014, a proposal to establish a special Task Force (TF) to make proposals in relation to HERCA activities in support of the transposition and implementation of the new Euratom BSS Directive was agreed. The BSS-TF was established, commenced its work on the basis of a 'non-questionnaire' and a discussion document. It met on one occasion on 7 October 2014 and agreed an action plan for consideration by the BoH. The agreed action plan proposal was approved by the BoH on the occasion of its 14. meeting in Stockholm, on 21-22 October 2014. The approved Action Plan covers the following areas: - Identification of HERCA's role in the transposition of the new Euratom BSS; - Definition of actions for HERCA in relation to the transposition of the BSS; - Coordination between HERCA and the EC in relation to BSS transposition activities. The Actions identified relate to several subject areas: Emergency preparedness and response; Medical exposures; Radon; Non-medical imaging exposures; RPE/RPO; General exchange of information. HERCA is a voluntary association, in which the Heads of European Radiological Protection Competent Authorities work together in order to identify common issues and propose practical solutions for these issues. It has no statutory role in relation to the transposition of the Euratom BSS. However, additional work by HERCA can support the transposition process as indicated in the Action Plan. Uniform transposition or implementation in the Member States is not an objective of HERCA activities. Clearly it will remain a matter for individual Member States as to the extent to which they avail of HERCA's work in transposing the BSS into their national regulations