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2499. Reduced-Iodine-Dose Dual-Energy Coronary CT Angiography Compared with Conventional CT: Non-Inferiority Study
Authors * Denotes Presenting Author
  1. David Rotzinger *; Lausanne University Hospital
  2. Salim Si-Mohamed; Lyon University Hospital
  3. Fabio Becce; Lausanne University Hospital
  4. Loic Boussel; Lyon University Hospital
  5. Reto Meuli; Lausanne University Hospital
  6. Philippe Douek; Lyon University Hospital
Objective:
To quantitatively evaluate the impact of virtual monochromatic images (VMI) on reduced-iodine coronary CT angiography (CCTA) regarding accuracy and precision of coronary lumen area measurements in vitro, and secondly to assess the image quality in vivo, compared with conventional CT obtained with regular iodine dose.

Materials and Methods:
A phantom simulating the coronary lumen attenuation of regular and reduced iodine injection protocols was used to determine the accuracy and precision of automated lumen area measurements for various acquisition parameters or VMI energy levels (40-130 keV, in 15 keV increments). The clinical study retrospectively included 203 patients (mean age, 51.7±16.8 years) who underwent CCTA with either standard (group A, n=103) or reduced (group B, n=100) iodine delivery rate and volume. Conventional CCTA images (group A) were qualitatively and quantitatively compared with 55 keV VMI (group B). The location of the venous catheter was recorded.

Results:
In the phantom study, reduced-iodine spectral CT with 55 keV VMI reconstructions performed better than regular iodine conventional CT, with a segmentation accuracy of 0.341 mm2 and 1.621 mm2, respectively (p<0.05), and a precision of 0.675 mm2 and 1.146 mm2, respectively (p<0.05). When analyzing multiple VMI energy levels, the highest segmentation precision and accuracy was achieved at lower VMI energy levels (i.e., 40 and 55 keV), regardless of the patient size and constrast medium concentration. In vivo, the mean contrast medium volume was 71.8±11.9 mL and 41.2±8.2 mL, respectively, (p<0.001). The rate of diagnostic CCTA in groups A and B was 88.4% (n=91/103) and 89% (n=89/100), respectively, and non-inferiority of protocol B was inferred since the lower bond of the 95% confidence interval of the difference did not cross the pre-specified 10% non-inferiority margin. Contrast-to-noise ratios (CNR) of lumen versus fat and muscle were higher in group B (p<0.001), and similar for lumen versus calcium (p=0.423). Finally, the venous catheters were more often placed on the forearm or hand in group B (p<0.001)

Conclusion:
In vitro, low keV VMI improve vessel area quantification. In vivo, low keV VMI allows for a 40% iodine dose and injection rate reduction while maintaining diagnostic image quality, and improve the CNR between lumen versus fat and muscle.