A New Contrast Enhancement Protocol for Subtraction Coronary Computed Tomography Requiring a Short Breath-Holding Time

Rationale and Objectives We have developed a new contrast enhancement protocol for subtraction coronary computed tomography (SCCTA) requiring a short breath-holding time. In the protocol, test and main boluses were sequentially and automatically injected, and correct timings for pre-contrast and contrast-enhanced scans for main bolus were automatically determined only by the test bolus tracking. Combined with a fixed short main bolus injection for 7 seconds, the breath-holding time was shortened as possible. The purpose of this study was to evaluate whether use of this new protocol produced adequate quality images, taking into account calcified lesions and in-stent lumens. Materials and Methods Patients ( n  = 127) with calcium scores of >400 Agatston units or a history of stent placement were enrolled. Breath-holding times were recorded, and image quality was visually evaluated by two observers. Results The mean ± standard deviation breath-holding time was 13.2 ± 0.6 seconds. The mean ± SD computed tomography (CT) number of coronary arteries for the pre-contrast scan was sufficiently low [99.2 ± 32.2 Hounsfield units (HU)] and, simultaneously, that for SCCTA was 367.0 ± 77.2 HU. The rate of segments evaluated as unreadable was sufficiently low (3.8%). Conclusions Use of the SCCTA protocol was efficient and allowed for a shorter breath-holding time and adequate diagnostic accuracy of SCCTA images, including images of calcified and stent implantation segments.