AJR:196, June 2011 W729 rotation time, because image reconstruction requires 180° [2]; 320-MDCT uses multiseg- ment reconstruction to improve the effective temporal resolution by using data from more than one R-R interval of the cardiac cycle to reconstruct an image [5]. Using this method, an effective temporal resolution of 87.5 milli- seconds can be obtained if two-segment recon- structions are used, compared with the tempo- ral resolution of a dual-source scanner, which ranges from 75 to 83 milliseconds [2, 5]. The trade-off for using multisegment reconstruc- tion is higher radiation dose to the patient as a result of longer exposure time. With 16 cm of craniocaudal coverage per gantry rotation, 320-MDCT enables scan- ning of the whole heart in a single heartbeat, thereby eliminating the “stair-step” artifact [3]. This artifact occurs as a result of sub- volume cardiac imaging over multiple gantry rotations, leading to nonoverlapping recon- struction intervals [6]. All scan data can be Coronary Image Quality of 320- MDCT in Patients With Heart Rates Above 65 Beats per Minute: Preliminary Experience Allan B. Lee 1 Dee Nandurkar 1 Michal E. Schneider-Kolsky 2 Marcus Crossett 1,3 Sujith K. Seneviratne 3 James D. Cameron 3 John M. Troupis 1,3 Lee AB, Nandurkar D, Schneider-Kolsky ME, et al. 1 Department of Diagnostic Imaging, Monash Medical Centre, Southern Health, 246 Clayton Rd, Clayton, Victoria 3168, Australia. Address correspondence to J. M. Troupis (John.Troupis@southernhealth.org.au). 2 Department of Medical Imaging and Radiation Sciences, Faculty of Medicine, Nursing and Health Sciences, Monash University, Melbourne, Australia. 3 MonashHEART, Southern Health and Department of Medicine, Monash University, Monash Cardiovascular Research Centre, Clayton, Victoria, Australia. Cardiopulmonary฀Imaging฀•฀Original฀Research WEB This is a Web exclusive article. AJR 2011; 196:W729–W735 0361–803X/11/1966–W729 © American Roentgen Ray Society C ardiac CT is a rapidly evolving noninvasive technique used in the detection and assessment of coronary artery disease. The im- ages produced by cardiac CT need to be of high quality for it to be a sensitive and diag- nostic tool. Patient-specific factors such as high heart rate may degrade the image quality of cardi- ac CT [1]. High-quality images free of cardi- ac motion artifact may be obtained by slow- ing the heart rate [2]. The current practice is aimed at decreasing the heart rate to below 65 beats/min, often with β-blocker medica- tion, before cardiac CT [3, 4]. Alternatively, the temporal resolution of the scanner needs to be fast enough to freeze the heart motion [3]. The temporal resolution of the scanner is limited by the gantry rotation time, which is the time needed to complete a 360° revolu- tion. The temporal resolution of a single tube and detector system is one half of the gantry Keywords: 320-MDCT, cardiac CT, heart rate above 65 beats/min DOI:10.2214/AJR.10.5252 Received July 2, 2010; accepted after revision November 7, 2010. OBJECTIVE. High heart rate may negatively influence the image quality of cardiac CT. The technical advances of 320-MDCT may overcome issues with poor image quality associated with high heart rate. This study aimed to evaluate the coronary image quality of 320-MDCT in patients with heart rates above 65 beats/min. MATERIALS฀ AND฀ METhODS. Patients who presented for cardiac CT were divided into two groups according to heart rate, either greater than 65 beats/min or less than or equal to 65 beats/min. Two radiologists were blinded to the patient groups and evaluated images of 15 coronary artery segments per patient using 320-MDCT with consensus agreement. The image quality was scored subjectively as 1 or 2 (diagnostic quality) or 3 (poor quality and nondiagnostic). RESULTS. There were no statistically significant differences between the two groups in terms of age, sex, and body mass index ( p > 0.05). The median heart rate was 70 beats/ min (range, 67–110 beats/min) for the group with heart rate greater than 65 beats/min and 60 beats/min (range, 48–65 beats/min) for the group with heart rate less than or equal to 65 beats/min ( p < 0.001). In patients with heart rates greater than 65 beats/min, diagnostic quality images (scores of 1 or 2) were obtained in 95.6% of the analyzed segments, compared with 96.9% in the group with heart rate less than or equal to 65 beats/min ( p = 0.7). CONCLUSION. Our initial evaluation suggests that coronary artery images of diagnostic quality can be obtained using 320-MDCT in most patients with heart rates greater than 65 beats/min, in percentages similar to those for patients with heart rates less than or equal to 65 beats/min. This finding may be the result of the inherent image acquisition and reconstruction technique of 320-MDCT. Lee et al. 320-MDCT in Patients With Elevated Heart Rates Cardiopulmonary Imaging Original Research Downloaded from www.ajronline.org by 52.73.204.196 on 05/17/22 from IP address 52.73.204.196. Copyright ARRS. For personal use only; all rights reserved