Introduction The purpose of this study was to quantify the reduction in patient radiation dose by X-ray imaging technology using image noise reduction and system settings for neuroangiography and to assess its impact on the working habits of the physician. Methods Radiation dose data from 190 neuroangiographies and 112 interventional neuroprocedures performed with state-of-the-art image processing and reference system settings were collected for the period January–June 2010. The system was then configured with extra image noise reduction algorithms and system settings, which enabled radiation dose reduction without loss of image quality. Radiation dose data from 174 neuroangiographies and 138 interventional neuroprocedures were collected for the period January–June 2012. Procedures were classified as diagnostic or interventional. Patient radiation exposure was quantified using cumulative dose area product and cumulative air kerma. Impact on working habits of the physician was quantified using fluoroscopy time and number of digital subtraction angiography (DSA) images. Results The optimized system settings provided significant reduction in dose indicators versus reference system settings (p<0.001): from 124 to 47 Gy cm² and from 0.78 to 0.27 Gy for neuroangiography, and from 328 to 109 Gy cm² and from 2.71 to 0.89 Gy for interventional neuroradiology. Differences were not significant between the two systems with regard to fluoroscopy time or number of DSA images. Conclusion X-ray imaging technology using an image noise reduction algorithm and system settings provided approximately 60% radiation dose reduction in neuroangiography and interventional neuroradiology, without affecting the working habits of the physician.

Study Design.: Prospective observational study. Objective.: To assess staff and patient radiation exposure during augmented reality surgical navigation in spine surgery. Summary of Background Data.: Surgical navigation in combination with intraoperative three-dimensional imaging has been shown to significantly increase the clinical accuracy of pedicle screw placement. Although this technique may increase the total radiation exposure compared with fluoroscopy, the occupational exposure can be minimized, as navigation is radiation free and staff can be positioned behind protective shielding during three-dimensional imaging. The patient radiation exposure during treatment and verification of pedicle screw positions can also be reduced. Methods.: Twenty patients undergoing spine surgery with pedicle screw placement were included in the study. The staff radiation exposure was measured using real-time active personnel dosimeters and was further compared with measurements using a reference dosimeter attached to the C-arm (i.e., a worst-case staff exposure situation). The patient radiation exposures were recorded, and effective doses (ED) were determined. Results.: The average staff exposure per procedure was 0.21 ± 0.06 μSv. The average staff-to-reference dose ratio per procedure was 0.05% and decreased to less than 0.01% after a few procedures had been performed. The average patient ED was 15.8 ± 1.8 mSv which mainly correlated with the number of vertebrae treated and the number of cone-beam computed tomography acquisitions performed. A low-dose protocol used for the final 10 procedures yielded a 32% ED reduction per spinal level treated. Conclusion.: This study demonstrated significantly lower occupational doses compared with values reported in the literature. Real-time active personnel dosimeters contributed to a fast optimization and adoption of protective measures throughout the study. Even though our data include both cone-beam computed tomography for navigation planning and intraoperative screw placement verification, we find low patient radiation exposure levels compared with published data. Level of Evidence: 3

In accordance with recommendations by the International Commission on Radiological Protection, the current European Basic Safety Standards has adopted a reduced occupational eye lens dose limit of 20 mSv yr ^–1 . The radiation safety implications of this dose limit is of concern for clinical staff that work with relatively high dose x-ray angiography and interventional radiology. Presented in this work is a thorough assessment of the occupational eye lens dose based on clinical measurements with active personal dosimeters worn by staff during various types of procedures in interventional radiology, cardiology and neuroradiology. Results are presented in terms of the estimated equivalent eye lens dose for various medical professions. In order to compare the risk of exceeding the regulatory annual eye lens dose limit for the widely different clinical situations investigated in this work, the different medical professions were separated into categories based on their distinct work pattern: staff that work (a) regularly beside the patient, (b) in proximity to the patient and (c) typically at a distance from the patient. The results demonstrate that the risk of exceeding the annual eye lens dose limit is of concern for staff category (a), i.e. mainly the primary radiologist/cardiologist. However, the results also demonstrate that the risk can be greatly mitigated if radiation protection shields are used in the clinical routine. The results presented in this work cover a wide range of clinical situations, and can be used as a first indication of the risk of exceeding the annual eye lens dose limit for staff at other medical centres.

Purpose: To develop an analytical model for bremsstrahlung production in a thick x‐ray target (i.e., the x‐ray tube anode) that takes into account the intrinsic bremsstrahlung angular distribution.Methods: X‐ray spectrum models developed from theoretical principles have traditionally treated the angular distribution of the bremsstrahlung production as spherically uniform. This assumption stems from the rationale that electrons promptly attain a diffuse directional distribution in an x‐ray target due to multiple scattering, thereby effectively masking the intrinsic bremsstrahlung angular distribution. In this work, a model that explicitly accounts for the angular distribution of the bremsstrahlung production is presented. The model combines Monte Carlo‐calculated depth, energy, and angular distributions of electrons penetrating the x‐ray target, and incorporates theoretical results for the differential bremsstrahlung cross section. The effects of using different simplified model assumptions for the electron penetration and the intrinsic bremsstrahlung angular distribution are analyzed for tungsten and molybdenum targets in the energy range 20–300 keV.Results: Typical assumptions of previous models are shown to introduce errors in calculated spectra. Particularly, it is shown that predictions of fluence and air kerma free‐in‐air can be overestimated by 15–30% (2–3% in aluminum half‐value layer thickness) for clinically relevant beam qualities. The present model is able to reproduce comprehensive Monte Carlo calculations of the bremsstrahlung production generally to within 1%.Conclusions: The bremsstrahlung model developed in this work is an improvement over previous models in that the main features of the electron penetration and the resulting bremsstrahlung are considered in detail. The model can be used for more accurate predictions of the energy and angular distribution of x rays emitted from an x‐ray tube.

Purpose: To present and validate a complete x‐ray emission model (bremsstrahlung and characteristic x‐ray emission) for the energy range 20–300 kV.Methods: An analytical x‐ray spectrum model that combines the bremsstrahlung emission model developed in Part I with a previously developed characteristic x‐ray emission model is validated by comparison with Monte Carlo calculations, published measured spectra, and models developed by other authors. Furthermore, the assumptions and limitations of previous spectrum models are summarized, and their predictions are compared with results obtained by Monte Carlo simulations of x rays emitted from tungsten and molybdenum targets.Results: The model is able to reproduce narrow‐beam Monte Carlo calculations to within 0.5% in terms of the first and second aluminum half‐value layer thickness (HVL). Compared with measured spectra, the difference in HVL is < 2% for typical diagnostic and therapeutic beam qualities available at primary standard laboratories. Compared with previous spectrum models, the present model performs especially well for low kilovoltage x‐ray beams (below 50 kV), and is reliable for a wider range of take‐off angles, that is, the angle between the target surface and the direction of emission. The difference in model and Monte Carlo predictions of the energy‐fluence weighted air kerma (i.e., the photon energy absorption in air) is < 0.5% using the present model, while previous spectrum models can differ by more than 10%.Conclusions: The x‐ray emission model developed in this work has been validated against Monte Carlo calculations and measured results. The model provides an efficient alternative to comprehensive Monte Carlo simulations and is an improvement over previous models. The model can be used to predict both central‐ and off‐axis spectra, as well as off‐axis effects such as the (anode) heel effect.