Contrast dose optimization in Transcatheter Aortic Valve Implantation (TAVI) planning Computed Tomography Angiography (CTA)

Purpose: Optimized contrast material (CM) administration protocols are required to maximize the diagnostic yield of Computed Tomography Angiography (CTA) studies. The purpose of this study is to evaluate image quality improvement in Pre-Transcatheter Aortic Valve Intervention (TAVI) planning CTA studies after instituting a new body mass index (BMI) based CM protocol compared to a prior CM protocol which had less gradation in larger patients.

Methods/Materials: We retrospectively assessed 120 randomly selected age and sex-matched patients who had a Pre-TAVI CTA at our institution between 2020-23, n=60 prior to CM protocol change and n=60 after. The initial CM protocol was 50cc for BMI range 17.5-28.4 kg/m2 (Small/Average, n=14), 75cc for BMI ranges of 28.5-33.4 kg/m2 (Large, n=15) and 33.5-39.4 kg/m2 (XL, n=16), and 100cc for BMI >39.4 kg/m2 (XXL, n=15). The new protocol used the same dose for Small/Average (50 cc, n=15) and Large (75 cc) groups. CM dose was increased from 75cc to 100cc for XL (n=20) and 125-160cc was used for XXL (n=9) at the radiologist’s discretion, based on desired flow-rate. Tube voltage was set to 100 kVp for small/average patients and 120 kVp for all others. Scans were obtained on a Revolution CT (GE Healthcare, Waukesha) with automated tube current modulation. Contrast material was Omnipaque 350 ®. Attenuation (HU) at the aortic root was measured, with ≥ 250 HU considered satisfactory. Average HU values per size group pre- and post-intervention were compared with Student’s t-test. Independent samples t-test was used to compare scan satisfaction by binarizing outcomes as 1=satisfactory and 0=unsatisfactory.

Results: Mean attenuation values for each size group pre- and post-intervention were as follows: Small/Average: 383.6±56.8 vs. 368.1±41.4 (p=0.4041), Large: 323.3±50.2 vs. 321.3±40.1 (p=0.9021), XL: 280.3±37.8 vs. 351.6±59.0 (p=0.0002) and XXL: 264.9±46.1 vs. 328.2±66.2 (p=0.0112). Percentage of satisfactory scans in the XL group increased from 69% to 95% (p=0.0364), and from 40% to 100% (p=0.0019) in the XXL group.

Conclusions: Adoption of a higher dose CM administration protocol yielded significant improvement in image quality in larger patients.