[en] At the Norwegian Radiation Protection Authority, an inspection body dedicated to the national breast cancer screening programme has been established. This report contains results from the acceptance tests and status control carried out during the first year of the project. The results show that the equipment is performing properly, and that the image quality is fully satisfactory at all sites. 10 refs., 13 figs., 2 tabs

[en] The γ-decay from states with low spin at high excitation energy has been studied using the (³He,³He)¹⁶²Dy and (³He,⁴He)¹⁶²Dy reactions. The γ-ray spectra obtained in the two reactions are almost identical and do not reveal any reaction dependence

[en] The Norwegian Radiation Protection Authority and the Norwegian Radium Hospital have in collaboration carried out a survey of the mammography centers in use between December 1993 and March 1994 (45 units at 41 centers). The scope of the project was to gain experience with, and to evaluate different methods for assessment of image quality. The scope was also to get an overview of the mammography practice in Norway. There were large variations in the utilisation of the equipment, which influence the image quality and probably the diagnostic accuracy. Substantial differences in equipment performance were also found. The report presents the results of the technical measurement from the survey. 18 refs., 20 figs., 4 tabs

[en] This report describes a method for assessing the total performance in mammography based on Receiver Operating Characteristic (ROC) analysis. In the time period from December 1993 to March 1994 the method was applied to assess the total performance of all the 45 Norwegian mammography laboratories operative at that time. Image quality characteristics in each laboratory was established by use of well-known phantoms

[en] To develop a method for receiver operating characteristics (ROC) studies in mammography. Material and Methods: We developed a phantom based on excised breast tissue and overlay tiles that could be arranged in an arbitrary pattern across the surface of the breast tissue. Some of the tiles contained structures simulating calcifications or masses that produced image contrast near the experimentally determined detection threshold. Based on this phantom, a methodology for performing ROC studies in mammography was developed. The ROC curves were constructed from reporting schemes filled in by radiologists at five different laboratories. The curves were determined by a novel method: a non-linear least-squares fit of a mathematical model to the data. Results: There were large differences among the areas under the ROC curves obtained from the five laboratories. (orig.)

[en] The performance of 45 mammography units in Norway has been compared by means of two commercial phantoms, a Nordic phantom and another used as a part of the American College of Radiology accreditation system (ACR). Three images of both phantoms were obtained from each unit, and corresponding dose measurements and sensiometric tests were performed. The results were evaluated according to Nordic recommendations and the phantom image quality criteria set by ACR. Large variations were found, although glandular doses were all kept below 2 mGy. The contrast and sensitivity of the film were shown to influence the image contrast and the dose considerably. Image quality criteria based on image quality parameters that can be assessed with technical phantoms are discussed. These should be separately linked to grid and non-grid techniques, and might be used as references for future quality control programmes based on these phantoms. (author)

[en] To assess the image quality at different mammography laboratories. Material and Methods: Two commercial mammographic test phantoms and one phantom based on excised mammary tissue were used in an assessment of the imaging chain and total performance at 45 Norwegian mammography laboratories. The breast-tissue phantom was used for a receiver operating characteristics (ROC) analysis. This was carried out by putting overlays with identifiable regions (some of which contained a cluster of simulated calcifications) on top of the mammary tissue, and then having a radiologist report the confidence of a finding for each region. Results and Conclusion: The areas under the ROC curves were in general high. In nearly all the laboratories, performance was improved when a magnification technique was applied. There were wide variations among the laboratories in total performance as measured by the area under the ROC curve, and also in the physical parameters derived by means of the commercial phantoms. In general, a good ROC performance was associated with a good physical performance in the imaging chain. (orig.)

[en] At the CART demonstrator in Oslo development of the radiotherapy simulator is going on. The main goal is to develop equipment and data programs to produce CT images at the simulator. A special detector to be applied for acquisition of transmission profiles is developed. Other activities are development of a system for applications of digitized image intensifier output as e.g. image enhancement, edge detection and digital longitudinal tomography (tomosyntheses). 7 refs.; 3 figs

[en] The γ-decay from states with low spin and high excitation energy has been studied using the ¹⁶³Dy(τ,α)¹⁶²Dy and ¹⁶²Dy(τ,τ')¹⁶²Dy reactions. For excitation energies above 4.5 MeV the γ-ray spectra obtained in the two reactions are almost identical, revealing no reaction dependence. (orig.)

[en] The γ-decay following the ²⁷Al(tau,α), ²⁷Al(tau,tau) and ²⁷Al(tau,t) reactions has been studied using Esub(tau)=45 Mev. For all three reactions a maximum mean γ-ray multiplicity of < Mγ>=1.8+-0.2 is observed, in good agreement with the Fermi gas model. The variation of < Msub(γ)> with excitation energy for the ²⁷Al(tau,tau)²⁷Al reaction, however, shows considerable deviations from the decay pattern expected for a statistical system. From a comparison with other reaction channels, we suggest that the selectivity in the excitation of states in the inelastic process is responsible for this non-statistical pattern. (orig).