Transcatheter aortic valve implantation (TAVI) planning CT on 8-cm detector scanners: Proper dose control by combined use of two deep-learning reconstruction algorithms

Abstract

Purpose: To explore the feasibility of transcatheter aortic valve implantation (TAVI) planning computed tomography (CT) on single-source 8-cm detector scanners with proper dose control by using two deep-learning reconstruction algorithms.

Methods: Reduced-dose TAVI planning CT was simulated by replacing routine aortic CT angiography (CTA) with a reduced-dose aortic CTA and a reduced-dose coronary CTA (Group A, n = 82), while keeping the total dose unchanged. Each of the two CTA scans was processed with a different deep-learning reconstruction algorithm. Routine-dose coronary CTA (Group B, n = 86) and routine-dose aortic CTA (Group C, n = 77) with hybrid iterative reconstruction were used as reference for evaluating the acceptability for surgical planning (A vs. B for aortic valve; A vs. C for access route) and for comparing both the diagnostic and objective image quality (A vs. B for coronary arteries; A vs. C for aortoiliac arteries).

Results: The mean effective dose in Group A was 8.22 ± 0.83 mSv, representing a 57% reduction of the routine-dose TAVI planning CT, that is, a routine-dose coronary CTA plus a routine-dose aortic CTA on the same scanner model. With respect to B and C, images in A were scored higher for evaluating the aortic valve (p = 0.045) and the access route (p = 0.014) and for diagnosing the thoracic aorta and iliac segments (p < 0.050), while the diagnostic confidence were comparable on the coronary arteries (p > 0.050), abdominal aorta (p = 0.276), and femoral segment (p = 0.816). The image noise in A was found to be 21%-55% lower, leading to a significant increase in contrast-to-noise ratio (CNR) by 63%-114% (p < 0.050).

Conclusion: Reduced-dose TAVI planning CT is feasible on 8-cm detector scanners by using deep-learning reconstruction algorithms, showing promise of implementing the examination in imaging settings that are more commonly accessible.

Keywords: computed tomography angiography; deep learning reconstruction; radiation dose; transcatheter aortic valve implantation.

FIGURE 1

Flowchart of the study design. CABG, coronary artery bypass graft; CCTA, coronary CT angiography; CT, computed tomography; DLP, dose‐length product; PCI, percutaneous coronary revascularization; TAVI, transcatheter aortic valve implantation.

FIGURE 2

Evaluation of the aortic valve and aortic annulus on CT images. (a) and (d): TAVI assessment of valvular cusp (blue line) and aortic annulus levels (green line) in the coronal view; (b) and (e): aortic valve images at the valvular cusp level; (c) and (f): aortic valve images at the aortic annulus level. Upper row: the coronal and axial CTA images of a 69‐year‐old man (BMI, 21 kg m⁻², HR, 77 bpm) in group A; lower row: the coronal and axial CTA images of a 59‐year‐old man (BMI, 22 kg m⁻², HR, 68 bpm) in group B (WW/WL = 800/200 HU). Group A: reduced‐dose TAVI planning CT; Group B: routine‐dose CCTA; BMI, body mass index; CCTA, coronary CT angiography; CT, computed tomography; CTA, CT angiography; HR, heart rate; TAVI, transcatheter aortic valve implantation.

FIGURE 3

CT images of the aortic‐iliac‐femoral vasculature illustrating the access route with enlarged axial views of different sites. The display window level setting is WW/WL = 350/40 HU. (a) and (c) represent the right aortoiliac artery access route, and (b) and (d) represent the left aortoiliac artery access route. AOR A, aortic arch; ASC AO, ascending aorta; CFA, common femoral artery; CIA, common iliac artery; CT, computed tomography; EIA, external iliac artery; IABD AO, infrarenal abdominal aorta; SABD AO, suprarenal abdominal aorta; THOR AO, thoracic aorta.

FIGURE 4

Comparison of the CCTA images between groups A and B. (a) the VR and CPR images of a 59‐year‐old woman (BMI, 24.44 kg m⁻², HR, 52 bpm) in group A (reduced‐dose TAVI planning CT); (b) the VR and CPR images of a 65‐year‐old woman (BMI, 23 kg m⁻², HR, 55 bpm) in group B (routine‐dose CCTA). Both patients were identified with calcified plaques (white arrow) on the LAD. CCTA, coronary CT angiography; CPR, curved planar reconstruction; CT, computed tomography; CTA, CT angiography; LAD, left anterior descending; LCX, left circumflex; RCA, right coronary artery; TAVI, transcatheter aortic valve implantation; VR, volume rendering.

FIGURE 5

Box plot of image noise (a) and contrast‐noise‐ratio (b) measured at different sites. **: p < 0.001, statistically significant difference. Group A: reduced‐dose TAVI planning CT; Group B: routine‐dose CCTA; Group C: routine‐dose aortic CTA. CCTA, coronary CT angiography; CT, computed tomography; CTA, CT angiography; TAVI, transcatheter aortic valve implantation.