A variety of radiation sources exist at the Department of Radiology and the Department of Nuclear Medicine at Karolinska University Hospital Huddinge. Radiation sources can also be found in areas outside of these departments due to the wide use of mobile xray machines and fluoroscopic c-arm equipment and also due to the movement of patients that have received diagnostic or therapeutic doses of radionuclides. In a proposal for a new legislation from the Swedish Radiation Protection Authority (SSI), which was later issued as legislation SSI FS 2005:6, the effective doses of the general public from a practice using ionising radiation need to be kept below stated limit of 0.1 mSv/year. This project was performed to verify the dose limit for individuals of the general public in the above mentioned practices. Long-term measurements with TL-dosimeters were utilised to carry out the environmental monitoring of the areas throughout the Departments of Radiology and Nuclear Medicine. To assess the contribution of ionising radiation from rooms housing mobile fluoroscopic c-arm equipment to surrounding areas, a tissue equivalent phantom of size (30×30×20 cm3) was employed to simulate a patient and the scattered radiation was monitored by using area monitors, such as portable proportional counters. The annual effective doses were calculated in terms of personal dose equivalent as well as ambient dose equivalent monitored using TL-dosimeters and area monitors, respectively. The stated limit of 0.1 mSv/year to the general public was verified by risk analysis. An attempt to create a method for determining the amount of radiation shielding in terms of lead equivalence in walls, doors, protective glasses of manoeuvre rooms and cupboards of diagnostic x-ray labs was also performed using a radiation point source of 99mTc and a NaI scintillation detector. Depending on the accuracy in the measurements the amount of lead deviated slightly from the expected 2 mm value based on the former legislation SSI FS 1991:1.

Gamma-ray spectrometry measurements performed on site, or “in situ”, is a widely used and powerful method that can be employed both to identify and quantify ground deposited radionuclides. The purpose of this thesis is to improve the calibration of high purity germanium (HPGe) detectors for in situ measurements, and calculate the combined uncertainty and potential systematic effects. An improved semi-empirical calibration method is presented, based on a novel expression for the intrinsic detector efficiency that includes both the energy and angular response of the detector. A three-layer model for the description of the depth distribution of the radionuclide and the soil density is proposed. The combined uncertainty of intrinsic detector efficiency calibrations and in situ measurements according to the proposed method was estimated. The uncertainty in the intrinsic detector efficiency was found to be 5.1 and 8.1% (coverage factor k=1, i.e. for a confidence interval of about 68%), for the two detectors calibrated. These numbers were, however, at a later stage reduced to 3.7 and 4.2%, using a revised expression for the intrinsic detector efficiency. For in situ measurements, the combined standard uncertainty was found to be 15-20% (k=1), based on the original expression for the intrinsic detector efficiency. Monte Carlo models of the two detectors were created and Monte Carlo calculated values for intrinsic detector efficiency were compared with experimental data. As a discrepancy was found, a thorough investigation of the detector response was performed. Scanning of the detector surface with a collimated 59.5 keV photon beam revealed the detector response to be highly irregular over the detector surface. It was concluded that the efficiency deficit of the detector could most likely be attributed to an increase in dead layer thickness compared with manufacturer supplied data. The thickness of the dead layer was estimated to be 1.5-1.9 mm, whereas the nominal value was 0.7 mm. Radiographs of the detectors were produced that provided valuable information about the physical dimensions of the germanium crystal, as well as its actual location within the detector housing. The Monte Carlo models were employed to calculate in situ measurement efficiencies for measurements of 137Cs deposition from the Chernobyl fallout. Results from the Monte Carlo simulations were compared both with the semi-empirical method and with soil sample data, and satisfactory agreement was confirmed. It was then proceeded to employ the Monte Carlo model to calculate the effect on in situ measurement results by two influencing parameters: ground curvature and activity in trees. Neither of these parameters was found to influence the result by more than about 25%. This deviation is comparable with the measurement uncertainty, and should not deter from measurements in such terrain.

Reference radiation fields for x-ray qualities are described by the International Organization of Standards (ISO). This study describes the procedure to establish nine different low energy X-ray qualities at the national metrology laboratory, Swedish Radiation Protection Authority, following the document ISO 4037. Measurements of tube voltage, half-value layer, mean energy and spectral resolution have been performed for qualities N-15, N-20, N-25, N-30, N-40, L-20, L-30, L-35 and L-55. Furthermore, dose equivalent conversion coefficients for operational quantities ambient dose equivalent, personal dose equivalent and directional dose equivalent have been calculated by folding the mono-energetic conversion factors with measured spectral distributions of the x-ray qualities. The spectral distributions were unfolded from pulse-height distributions to photon distributions using simulated data of the semi-conductor detector used for measurements, generated with the Monte Carlo code PENELOPE.

Numerous scenarios exist whereby radioactive particulates are transported between spatially separated points of interest. An example of this phenomenon is, in the aftermath of a Radiological Dispersal Device (RDD) detonation, the resuspension of radioactive particulates from the resultant fallout field. Quantifying the spatial distribution of radioactive particulates allow for the calculation of potential radiation doses that can be incurred from exposure to such particulates. Presently, there are no simulation techniques that link radioactive particulate transport with subsequent radiation field determination and so this thesis develops a coupled Computational Fluid Dynamics (CFD) and Monte Carlo (MC) Radiation Transport approach to this problem. Via particulate injections, the CFD simulation defines the spatial distribution of radioactive particulates and this distribution is then employed by the MC Radiation Transport simulation to characterize the resultant radiation field. GAMBIT/FLUENT are employed for the CFD simulations while MCNPX is used for the MC Radiation Transport simulations. / UOIT

Radiation therapy with light ions improves treatment outcome for a number of tumor types. The advantageous dose distributions of light ion beams en-able exceptional target conformity, which assures high dose delivery to the tumor while minimizing the dose to surrounding normal tissues. The demand of high target conformity necessitates development of accurate methods to calculate absorbed dose distributions. This is especially important for heavy charged particle irradiation, where the patient is exposed to a complex radia-tion field of primary and secondary ions. The presented approach combines accurate Monte Carlo calculations using the SHIELD-HIT07 code with a fast analytical pencil beam model, to pro-vide dose distributions of light ions. The developed model allows for ana-lytical descriptions of multiple scattering and energy loss straggling proc-esses of both primary ions and fragments, transported in tissue equivalent media. By applied parameterization of the radial spread of fragments, im-proved description of radial dose distributions at every depth is obtained. The model provides a fast and accurate tool of practical value in clinical work. Compared to conventional radiation modalities, an enhanced tissue response is seen after light ion irradiation and biological optimization calls for accu-rate model description and prediction of the biological effects of ion expo-sure. In a joint study, the performance of some radiobiological models is compared for facilitating the development towards more robust and precise models. Specifically, cell survival after exposure to various ion species is modeled by a fast analytical cellular track structure approach in conjunction with a simple track-segment model of ion beam transport. Although the stud-ies show that descriptions of complex biological effects of ion beams, as given by simple radiobiological models, are approximate, the models may yet be useful in analyzing clinical results and designing new strategies for ion therapy.

Introduktion Medicinsk vetenskap och sjukvårdens möjligheter att hjälpa utvecklas ständigt. Sjukvården idag kan i många fall ställa rätt diagnos och ge en effektiv behandling för att bota den som drabbats av ohälsa. Radiologiska undersökningar är ett viktigt hjälpmedel men innebär också risker i form av strålning samt felaktigt resursanvändande. Syfte Syftet med förbättringsarbetet var att skapa en bättre användning av radiologi och följsamhet till medicinska riktlinjer så att patienten får rätt undersökning utifrån sitt behov samt att resur-ser nyttjas mer optimalt. Målsättningen var att öka andelen berättigade undersökningar. Syftet med studien av förbättringsarbetet var att få en förståelse för vilka faktorer som påverkar remittentens val av radiologisk undersökning och därmed berättigandegraden vilka aktiviteter i förbättringsarbetet påverkar berättigandegraden och på vilket sätt Metod Interventioner i form av utbildning och mätningar användes för att höja berättigandegraden. Bedömning av berättigandegraden gjordes av en ST-läkare. En fallstudie med kvalitativ ansats genomfördes och fokusgruppintervju användes för att stu-dera förbättringsarbetet. Resultat Studien visar att berättigandegraden ökar något som ett resultat av de valda interventionerna. Utbildningen på plats gav också upplevda positiva effekter i form av bättre kunskap och lä-rande för deltagare. Analysen visade att osäkerhet som läkare upplever i sitt arbete med patienten kan härledas till kategorierna kunskap och krav. Diskussion/Slutsats Utbildning genomförd av radiologispecialist har visat sig vara framgångsrikt koncept. Mät-ningar som metod för lärande och förändring uppfattades istället som mätning för uppföljning. Förbättrad kunskap kring vilka faktorer som styr läkares val av undersökning har uppnåtts och områden för fortsatt förbättring har identifierats / Introduction Medical science and medical facilities and clinical possibilities to help patients evolve con-stantly. Healthcare today can often make the diagnosis and provide effective treatment to cure the victim of ill health. Radiological surveys are an important tool but also provide risks in the form of radiation, and improper use of resources. Purpose The purpose of the improvement work was to create a better use of radiology and adherence to medical guidelines so that the patient gets the right for increase based on their needs and resources will be used more optimally. The goal was to increase the proportion of eligible studies. The purpose of the study of the improvement was to gain an understanding of what factors affect physicians choice of radiological investigation and thereby provide entitlement degree which activities in the improvement process affects eligibility degree and in what way Method Interventions in the form of education and measurements used to improve eligibility rate. As-sessment of the eligibility rate was made by a resident physician. A case study with a qualitative approach was implemented and focus-group interviews were used to study the improvement process. Results Results indicates that the eligibility rate increased slightly as a result of the selected interven-tions. Education in place, however, gave perceived benefits in terms of improved knowledge and learning for participants. The analysis showed that the uncertainty that physicians experience in their work with pa-tients can be attributed to the categories of knowledge and requirements. Discussion / Conclusion Education conducted by a radiology specialist has is shown to be a successful concept. Meas-urements as a method of learning and change were perceived as measurement for monitoring. Improved knowledge about the determinants of physician choice of survey has been achieved and areas for further improvement are identified.

Acquired data from dynamic contrast enhanced MRI measurements can be used to non-invasively assess tumour vascular characteristics through pharmacokinetic modelling. The modelling requires an arterial input function which is the concentration of contrast agent in the blood reaching the volume of interest as a function of time. The aim of this work is testing and optimizing a turboFLASH sequence to appraise its suitability for measuring the arterial input function by measuring phase. Contrast concentration measurements in a phantom were done with both phase and relaxivity techniques. The results were compared to simulations of the experiment conditions to compare the conformance. The results using the phase technique were promising, and the method was carried on to in-vivo testing. The in-vivo data displayed a large signal loss which motivated a new phantom experiment to examine the cause of this signal reduction. Dynamic measurements were made in a phantom with pulsatile flow to mimic a blood vessel with a somewhat modified turboFLASH sequence. The conclusions drawn from analyzing the data were used to further improve the sequence and this modified turboFLASH sequence was tested in an in-vivo experiment. The obtained concentration curve showed significant improvement and was deemed to be a good representation of the true blood concentration. The conclusion is that phase measurements can be recommended over relaxivity based measurements. This recommendation holds for using a slice selective saturation recovery turboFLASH sequence and measuring the arterial input function in the neck. Other areas of application need more thorough testing.

Advances in coronary Computed Tomography Angiography (CTA) have resulted in a boost in the use of this new technique in recent years, creating a challenge for radiologists due to the increasing number of exams and the large amount of data for each patient. The main goal of this study was to develop a computer tool to facilitate coronary CTA analysis by combining knowledge of medicine and image processing, and to evaluate the performance in clinical settings. Firstly, a competing fuzzy connectedness tree algorithm was developed to segment the coronary arteries and extract centerlines for each branch. The new algorithm, which is an extension of the “virtual contrast injection” (VC) method, preserves the low-density soft tissue around the artery, and thus reduces the possibility of introducing false positive stenoses during segmentation. Visually reasonable results were obtained in clinical cases. Secondly, this algorithm was implemented in open source software in which multiple visualization techniques were integrated into an intuitive user interface to facilitate user interaction and provide good over­views of the processing results. An automatic seeding method was introduced into the interactive segmentation workflow to eliminate the requirement of user initialization during post-processing. In 42 clinical cases, all main arteries and more than 85% of visible branches were identified, and testing the centerline extraction in a reference database gave results in good agreement with the gold standard. Thirdly, the diagnostic accuracy of coronary CTA using the segmented 3D data from the VC method was evaluated on 30 clinical coronary CTA datasets and compared with the conventional reading method and a different 3D reading method, region growing (RG), from a commercial software. As a reference method, catheter angiography was used. The percentage of evaluable arteries, accuracy and negative predictive value (NPV) for detecting stenosis were, respectively, 86%, 74% and 93% for the conventional method, 83%, 71% and 92% for VC, and 64%, 56% and 93% for RG. Accuracy was significantly lower for the RG method than for the other two methods (p<0.01), whereas there was no significant difference in accuracy between the VC method and the conventional method (p = 0.22). Furthermore, we developed a fast, level set-based algorithm for vessel segmentation, which is 10-20 times faster than the conventional methods without losing segmentation accuracy. It enables quantitative stenosis analysis at interactive speed. In conclusion, the presented software provides fast and automatic coron­ary artery segmentation and visualization. The NPV of using only segmented 3D data is as good as using conventional 2D viewing techniques, which suggests a potential of using them as an initial step, with access to 2D reviewing techniques for suspected lesions and cases with heavy calcification. Combining the 3D visualization of segmentation data with the clinical workflow could shorten reading time.

PURPOSE: To determine the management performance indicators most frequently utilized in academic radiology departments in the United States. MATERIALS AND METHODS: This investigation met the criteria for an exemption from institutional review board approval. A cross-sectional study in which a validated national survey was sent to members of the Society of Chairmen of Academic Radiology Departments (SCARD) was conducted. The survey was designed to examine the following six categories of 28 performance indicators: (a) general organization, (b) volume and productivity, (c) radiology reporting, (d) access to examinations, (e) customer satisfaction, and (f) finance. A total of 158 variables were included in the analysis. Summary statistics, the 2 test, rank correlation, multiple regression analysis, and analysis of variance were used. RESULTS: A response rate of 42% (55 of 132 SCARD members) was achieved. The mean number of performance indicators used by radiology departments was 16 ± 6.35 (standard deviation). The most frequently utilized performance indicators were as follows: (a) productivity, in terms of examination volume (78% [43 departments]) and examination volume per modality (78% [43 departments]); (b) reporting, in terms of report turnaround (82% [45 departments]) and transcription time (71% [39 departments]); (c) access, in terms of appointment access to magnetic resonance imaging (80% [44 departments]); (d) satisfaction, in terms of number of patient complaints (84% [46 departments]); and (e) finance, in terms of expenses (67% [37 departments]). Regression analysis revealed that the numbers of performance indicators in each category were statistically significant in predicting the total number of performance indicators used (P < .001 for all). Numbers of productivity and financial indicators were moderately correlated (r = 0.51). However, there were no statistically significant correlations between the numbers of performance indicators used and hospital location, hospital size, or department size (P > .4 for all). CONCLUSION: Assessing departmental performance with a wide range of management indicators is not yet an established and standardized practice in academic radiology departments in the United States. Among all indicators, productivity indicators are the most frequently used.

This Thesis deals with the option of employing the Armed Forces of the Czech Republic (ACR) when a radiation emergency is imminent. Primarily, it focuses on evaluation of selected devices designed for radiation reconnaissance; summarising of radiation protection related legislation; and study of approved procedures. At its beginning, this Thesis tracks the origin of early detection systems at the territory of the then Czechoslovak Socialist Republic and their gradual evolution into the the existing form. From the radiation emergency point of view, this nationwide system represents a priceless help for monitoring of radioactive contamination dispersion and for warning. The following part sums up basic information on what is an ionizing radiation, how it comes into being and which basic quantities describe it. This part also contains basic type distinction, description of consequences for human organism and the most significant interactions of sources of ionizing radiation that could be misused with the most probability. This specific topic is introduced here because of the subsequent part of this Thesis being named Radiological Dispersion Device, or the dirty bomb. The significant part of this Thesis is the summary and classification of related legislation. The first documents referred to are two international standards. Publication 103 the 2007 Recommendations of the International Commission on Radiological Protection is dealing, inter alia, with dosing limits determining dose levels in planned exposure situations and reference levels used for emergency exposure situations and existing exposure situations. Publication 96 Protecting People against Radiation Exposure in the Event of a Radiological Attack is more substantial for this Thesis since it partly copes with the protection of front-line units including Integrated Rescue System (IRS) components and it specifies maximum exposure time for intervening personnel. Based on the IRS Catalogue of Typical Activities (STC 01/IZS), Materialised and Verified Use of a Radiological Weapon, the ACR would be one of the intervening components in such an attack. This Thesis analyses in detail individual ACR procedures starting with activities before employment, through threat prevention, event reaction to post-event activities like decontamination followed by monitoring of personnel contamination and their health condition. The practical part deals mainly with one of the Thesis´s goals which was evaluation of selected dosimetric devices used by the military for radiation reconnaissance. For this purpose, the quantitative research processing their main parameters was applied. The analysis within a selected sample was used for comparing and the sumary index IVi then showed the status of device applicability for contemporary use in radiation emergency. The pre-defined goals of this Thesis have been met implementing the above methods. The comparison of individual devices and their evaluation in respect to their applicability in joint radiation emergency operation with other IRS components has been carried out via discussion. It has been found out that some of the devices are obsolete and do not comply with the requirements for this job. This fact reflects the reality that these devices were designed in the period of a potential nuclear war. This corresponds with their robust structure and high level of sensitivity which is not desirable for a radiation emergency. The most severe problem, however, seems to be the fact that some devices measure quantities in old, no more used, units which could cause misinterpretation. On the other hand, other devices are modern, sensitive at low levels of dose input and offer real-time information on a well organised LCD display. To answer the question of ACR´s readiness to intervene in a radiation emergency one has to say that the ACR is ready to meet its rescue and consequence management tasks at a satisfactory level.