The aim of this study was to carry out a bench evaluation of the biomechanical feasibility of carbon dioxide (CO2) coronary arteriography. Many patients among the aging population of individuals requiring cardiac intervention have underlying renal insufficiency making them susceptible to contrast-induced nephropathy. To include those patients, it is imperative to find an alternative and safe technique to perform coronary imaging on cardiac ischemic patients. As CO2 angiography has no renal toxicity, it may be a possible solution offering good imaging with negligible collateral effects. Theoretically, by carefully controlling the gas injection process, new automatic injectors may avoid gas reflux into the aorta and possible cerebral damage. A feasibility study is mandatory. A mechanical mock of the coronary circulation was developed and employed. CO2 was injected into the coronary ostium with 2 catheters (2F and 6F) and optical images of bubbles flowing inside the vessels at different injection pressures were recorded. The gas behavior was then carefully studied for quantitative and qualitative analysis. Video recordings showed that CO2 injection at a precise pressure in the interval between the arterial dicrotic notch and the minimum diastolic value does not result in gas reflow into the aorta. Gas reflow was easier to control with the smaller catheter, but the gas bubbles were smaller with different vascular filling. Our simulation demonstrates that carefully selected injection parameters allow CO2 coronary imaging without any risk of gas reflux into the aorta.
Carbon dioxide angiography is based on the visualization (i.e., the radiographic contrast) of gas bubbles injected in blood vessels. By using an experimental X-ray bench, the energy response of a flat panel detector has been measured (Varian CB4030) and, with a dedicated phantom and a software simulation, the image contrast of vessels is injected with Iodine and CO 2. Moreover, the dynamical behavior of a moving gas bubble has been studied with the software simulator. The results show that the contrast generated by carbon dioxide is about one fourth of that obtained with iodine, demonstrating that CO 2 angiography should use different radiological settings with respect to iodine angiography. In particular, a kVp increase has a lower reduction of contrast-to-noise-ratio (CNR) with carbon dioxide than with iodinated contrast medium (CM), suggesting possible technological improvements both on radiological emission and image enhancement methods.
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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