Iterative Model Reconstruction in Patients Undergoing CT before Transcatheter Aortic Valve Implantation: Reduction of Radiation and Contrast volume

Background: Iterative Model Reconstruction (IMR) allows for a remarkable noise reduction of computed tomography (CT) images. This permits the use of low tube voltage (80kVp), which reduces radiation and increases image contrast, while allowing to reduce contrast volume. Elderly patients with severe aortic stenosis undergoing CT before transcatheter aortic valve implantation (TAVI) may benefit from a reduce volume and rate of contrast administration.

Objective: To assess the performance of IMR during CT before TAVI compared with previous generation iterative image reconstruction (iDose).

Methods: 256-slice CT scans were acquired using IMR in 58 patients and iDose in 14 patients. The IMR protocol used: 80kVp, 1229mAs with 30-45ml contrast at 2.7-3.5ml/s, the iDoise⁴ protocol was: 100kVp, 1301mAs with 75-90ml contrast at 4-5 ml/s. Signal to noise ratio (SNR) and contrast-to-noise ratio (CNR), were measured on CT images at the level of the annulus and external iliac arteries. Subjective image quality was graded as (1 [poor] to 5 [excellent])

Results: The use of IMR resulted in a significant reduction of contrast medium volume (39±8 ml vs. 79±8 ml; P < 0.001), contrast infusion rate (3.0 ± 0.3 ml/s vs. 4.4 ± 0.5, ml/s; P < 0.001) and radiation dose (17±6 mSv vs. 32±13 mSv, P < 0.001) and in a significant increase in SNR (19±8 vs. 13±7; P < 0.001) and CNR (25±9 vs. 16±7, P < 0.001) at the level of the iliac arteries, compared to iDose. All patients of both groups showed a[4-5] subjective image quality at level of the aortic annulus and at level of Iliac arteries. SNR and CNR were similar in both groups at the level of aortic annulus: 19±9 Vs. 18±7 (p=0.7) and 25±11 Vs. 22±9 (p=0.5).

Conclusions: Combining IMR with 80kVp significantly reduces contrast volume, infusion rate and radiation while improving CT image quality before TAVI.