Reduced exposure using asymmetric cone beam processing for wide area detector cardiac CT

Abstract

The purpose of this study was to estimate dose reduction after implementation of asymmetrical cone beam processing using exposure differences measured in a water phantom and a small cohort of clinical coronary CTA patients. Two separate 320 × 0.5 mm detector row scans of a water phantom used identical cardiac acquisition parameters before and after software modifications from symmetric to asymmetric cone beam acquisition and processing. Exposure was measured at the phantom surface with Optically Stimulated Luminescence (OSL) dosimeters at 12 equally spaced angular locations. Mean HU and standard deviation (SD) for both approaches were compared using ROI measurements obtained at the center plus four peripheral locations in the water phantom. To assess image quality, mean HU and standard deviation (SD) for both approaches were compared using ROI measurements obtained at five points within the water phantom. Retrospective evaluation of 64 patients (37 symmetric; 27 asymmetric acquisition) included clinical data, scanning parameters, quantitative plus qualitative image assessment, and estimated radiation dose. In the water phantom, the asymmetric cone beam processing reduces exposure by approximately 20% with no change in image quality. The clinical coronary CTA patient groups had comparable demographics. The estimated dose reduction after implementation of the asymmetric approach was roughly 24% with no significant difference between the symmetric and asymmetric approach with respect to objective measures of image quality or subjective assessment using a four point scale. When compared to a symmetric approach, the decreased exposure, subsequent lower patient radiation dose, and similar image quality from asymmetric cone beam processing supports its routine clinical use.

Simulated 50 % radiation dose reduction in coronary CT angiography using adaptive iterative dose reduction in three-dimensions (AIDR3D)

“…Dose reduction in cardiac CT [21, 22] using iterative reconstruction methods have been extensively investigated [9, 11–13, 17, 18, 30]. One group of studies compares metrics of image quality (e.g.…”

“…All patients were imaged with axial 320 × 0.5 mm detector row CT [20, 21] (AquilionONE, Toshiba Medical Systems Corporation, Japan) using asymmetric cone beam reconstruction [22]. All scanning was done within 1 heart beat using prospective ECG gating except for one subject who underwent 2-beat retrospective ECG-gated CCTA for an evaluation of cardiomyopathy.…”

Prognostic Value of Coronary Computed Tomography (CT) Angiography and Coronary Artery Calcium Score Performed Before Revascularization

“…Imaging using the 320‐detector row CT paralleled the 64‐detector row CT protocol, with the following differences: the first‐generation 320×0.5‐mm scanner (Aquilion ONE, Toshiba Medical Systems Corporation) operated on the v4.51 software platform; and the craniocaudual field of view was tailored to the smallest exposure (10, 12, 12.8, 14, or 16 cm) that encompassed the heart. The default tube voltage was 120 kV.…”

Diagnostic Value of 320-Slice Coronary CT Angiography in Coronary Artery Disease: A Systematic Review and Meta-Analysis

“…Steigner et al in their early study reported that narrowing the phase window to 10% in prospectively ECG-triggered 320-slice CCTA resulted in low radiation dose of 5.3 mSv while still achieving diagnostic images in more than 95% of patients [33]. For a 10% phase window width, more than 20% dose reduction was achieved with use of the asymmetric approach when compared to the standard symmetric approach (4.05 mSv vs 5.33 mSv) as shown in a recent study conducted by Bedayat et al [34]. Tung et al based on their single centre experience concluded that up to 80% reduction in median radiation dose in CCTA down to 2.18 mSv from the initial installation to the most recent experience of using 320-slice CT using different approaches comprising narrowing phase window width, minimising scan length, application of advanced tube current modulation and advanced image reconstruction algorithms [35].…”