The temporal resolution has been further improved by roughly a factor of two by adding a second CT beamline (source/detector pair) on the gantry of some scanners, thus reducing motion artifacts. Gantry speed improvements alone cannot meet the high demands of imaging the coronaries robustly at all cardiac phases. Temporal resolution has been improved as gantry periods have fallen further (to approximately one fourth s/rot), but progress along this direction has slowed since doubling the gantry speed quadruples the G-forces and places immense mechanical requirements on the gantry. In recent years, great strides have been made toward addressing the four challenges listed above. Remaining challenges included motion artifacts, banding artifacts (due to misregistration and contrast dynamics), calcium blooming, and noise (for high body mass index patients). When combined with the administration of heart rate lowering medications, 64-slice scanners proved to be quite effective at ruling out coronary artery disease (CAD) in many patients. By 2005, 64-slice scanners with faster gantry rates (approximately 0.35 s), higher coverage (approximately 4 cm), better spatial resolution (approximately 0.5 mm), and prospective gating techniques were available and enabled robust coronary imaging in a routine clinical setting in as few as five heartbeats. Multi-slice scanner technology developed quickly thereafter. Pioneering work in imaging the heart using 4-slice, 0.5 s-gantry CT scanners required long breath holds (30 s), gave spatial resolution of between 1.3 and 3.3 mm in the axial direction, and delivered a relatively high radiation dose due to the retrospective nature of the gating. A combination of these techniques could avoid repeat scans for subtraction techniques.Ĭardiac CT angiography (CCTA) has come a long way since its introduction near the turn of the century. In addition, DL techniques have shown great promise to correct for blooming artifacts. The partial volume effect can be minimized by increasing the CT spatial resolution through higher-resolution CT hardware or advanced high-resolution CT reconstruction. The partial volume effect is the leading cause of blooming artifacts. The proposed solutions are classified as high-resolution CT hardware, high-resolution CT reconstruction, subtraction techniques and post-processing techniques, with a special emphasis on deep learning (DL) techniques. The main reported causes of blooming artifacts are the partial volume effect, motion artifacts and beam hardening. More than 30 journal publications were identified with specific relevance to blooming artifacts. The claims from literature are compared and interpreted, aiming at narrowing down the root causes and most promising solutions for blooming artifacts. A literature survey was performed covering any publications with a specific interest in calcium blooming and stent blooming in cardiac CT. This review paper aims to summarize cardiac CT blooming artifacts, how they present clinically and what their root causes and potential solutions are.
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