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Objectives: Thanks to its lack of allergic reactions and renal toxicity, CO 2 represents an alternative to iodine as a contrast medium for peripheral subtraction angiography. Since CO 2 has a lower and negative contrast than iodine, postprocessing DSA and stacking are mandatory. So, it seems that higher doses than traditional iodine angiography are required. We addressed the dosimetric aspects of CO 2 angiography for two different commercial DSA-apparatus. Materials and Methods: Two different radiological suites were analyzed by recreating the same setup on all the apparatuses: we used a PMMA slabs phantom with a MPD Barracuda dosimeter on its side to collect all radiological parameters. Results: Results show that the irradiation parameters were left completely unchanged between the traditional and CO 2 angiographic programs. Conclusions: This leads to thinking that these CO 2 protocols do not operate on the X-ray emission, but only differ on image manipulation. The possibility of improvements by changing radiological parameters are still not explored and really promising.

The aim of this in vitro study was to evaluate the feasibility of movement compensation for CO2 coronary angiography. The use of CO2 as a contrast medium for coronary angiography in a routine clinical setting is still premature. Nonetheless, the gas can solve most of the problems related to iodine contrast-induced nephropathy and can be safely used for patients with renal insufficiency. In a previous work [I. Corazza et al., AIP Adv. 8(1), 015225 (2018)], we demonstrated that an adequate setting of the CO2 injection parameters (pressures and volumes) allows gas injection into the coronaries, avoiding reflux into the aorta and cerebral circulation. A mechanical mock simulating coronary circulation and movement was used to simulate different CO2 injection conditions. Simultaneous acquisition of ECG and optical images allowed synchronous frame extraction for post-processing analysis, like masking and stacking processes. A single test with a radiological apparatus was done to demonstrate the feasibility of the technique. By injecting CO2 at a pressure between the dicrotic notch and diastolic value, no reflux into the aorta was observed and the new software yielded final optical images of clinical quality after about 8 seconds of injection. The feasibility test under the X-ray apparatus gave promising results. CO2 coronary angiography is still far from becoming a clinical standard, but our bench evaluation demonstrates that if the injection parameters are well-controlled and physiological values known, CO2 can be used as a contrast agent not only for the lower part of the body, but also for the coronary arteries, respecting basic safety standards.

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