Image quality assessment of high concentration contrast agent Iomeron-400 with Iomeron-350 and Ultravist-370 in ultra-high resolution coronary CT angiography using photon-counting detector CT

Background With the cutting-edge photon-counting detector CT (PCD-CT) technology improved image resolution is enabled in the form of ultra-high resolution (UHR) scans. However, contrast agent characteristics -especially iodine concentration – still greatly impact image quality (IQ). Aims We aimed to compare three contrast agents (Iomeron 400, Iomeron 350, and Ultravist 370) and to determine the optimal choice for diagnostic performance in UHR coronary computed tomography angiography (cCTA) Methods We retrospectively included patients who were scanned with UHR cCTA in our center. We used clinical indication (patients with high coronary calcium score or patients with prior coronary revascularization with stents), and overall IQ to match patients across the three contrast agent groups. Assessed quantitative IQ parameters were intraluminal attenuation, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and image noise (IN). Results We included a total of 123 patients into the final analysis. The three contrast agents were evenly distributed among patients (n=41 in each group). There were no significant differences across groups in baseline patient characteristics such as age, sex, BMI, or heart rate. Contrast administration protocols did not differ significantly in flow rate (mean 5.0±0.3 ml/sec across groups; p=0.81). However, we observed a slight difference in injected contrast volume: Iomeron 400 (85.2±8.0 ml), Iomeron 350 (87.0±6.9 ml), and Ultravist 370 (87.9±4.9 ml; p=0.23). Iodine delivery rate was significantly higher using Iomeron 400 (1990.2±109.1 mg/sec) compared to Iomeron 350 (1732.9±102.1 mg/sec) and Ultravist 370 (1822.9±106.0 mg/sec; p<0.05). We found that Iomeron 400 had significantly higher intraluminal attenuation in distal coronary arteries (525.8±109.0 HU) compared to Iomeron 350 (487.7±186.3 HU) and Ultravist 370 (428.5±107.9 HU; p<0.05). We measured higher proximal artery attenuation in the Iomeron 400 group (553.1±107.8 HU vs. 502.1±75.4 and 506.1±86.5 HU; p=0.0842). Likewise, we observed similar trends in the ascending aorta (577.1±105.8 vs. 524.7±82.1 and 523.5±88.9 HU; p=0.0733). Despite the attenuation differences, we found no significant differences in SNR (8.1±2.0 vs. 7.6±1.8 vs. 7.4±1.8; p=0.2358), CNR (9.2±2.2 vs. 9.0±2.1 vs. 8.9±2.1; p=0.7855), or IN (63.4±13.2 vs. 64.2±16.4 vs. 61.9±18.0; p=0.7624). All groups had high diagnostic IQ, with scans rated either as excellent or as good. Our analysis revealed that Iomeron 400 resulted with higher attenuation values without an increase in radiation dose or heart rate variability. Conclusions Our study concluded that in UHR cCTA imaging Iomeron 400 mg iodine/ml is superior to lower iodine concentration contrast media for coronary stenosis assessment, based on quantitative IQ and IQ. Our results support prioritizing Iomeron 400 for UHR coronary imaging using PCD-CT.