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PhD Defence Joris van Dijk

Image quality and radiation dose in cardiac imaging

Coronary artery disease is a major cause of death accounting for 8% of all deaths in the Netherlands. This disease can be detected in an early stage by cardiac imaging. However, this detection comes at the price of a relatively high radiation dose which is potentially harmful for the patient. Despite multiple widely-shared incentives in the last decade to optimize and revise protocols, the radiation dose from cardiac imaging remains relatively high and differs considerably between imaging centers. Recommended activity protocols have remained unchanged for decades, despite advancements in both hard- and software, and guidelines are sometimes outdated. Better adoption and further refinement of best practices and new techniques, such as patient tailored low-activity protocols and new X-ray equipment, can therefore contribute to reducing the cumulative radiation dose from medical imaging while maintaining or even improving image quality.

In this thesis, we showed that a body-weight dependent activity protocol results in a stable and higher image quality across all patients in SPECT myocardial perfusion imaging (MPI) (Chapter 2). Moreover, tracer activities can further be reduced significantly (Chapter 3) without affecting the diagnostic outcome (Chapter 6). These achievements are feasible in all types of SPECT cameras (Chapter 4 and 5). In the same way, also in Rb-82 PET MPI significant dose reductions can be achieved without affecting diagnostic outcome (Chapter 7) and tailoring the radiation exposure to the patient also reduced the variability in CT coronary angiography image quality (Chapter 8). Additional technical features may also help: while attenuation correction proved to be helpful in reducing overall radiation exposure (Chapter 10), software-based motion correction seemed less useful for SPECT MPI (Chapter 9).  Final, new technical developments also help to reduce radiation dose in invasive cardiac procedures (Chapter 11) while the visibility of coronary artery calcifications during invasive coronary angiography remains very low (Chapter 12).