Feasibility of Selective Catheter-Directed Coronary Computed Tomography Angiography Using Ultralow-Dose Intracoronary Contrast Injection in a Swine Model Youngtaek Hong, BS,* Sanghoon Shin, MD,† Hyung-Bok Park, MD,‡§ Byoung Kwon Lee, MD,k Reza Arsanjani, MD,¶ Bríain ó Hartaigh, PhD,# Seongmin Ha, BS,# Yeonggul Jang, BS,* Byunghwan Jeon, BS,* Sunghee Jung, BS,* Se-Il Park, PhD,** Ji Min Sung, PhD,†† Hackjoon Shim, PhD,‡‡ and Hyuk-Jae Chang, MD, PhD§¶¶ Objective: Selective catheter-directed intracoronary contrast injected coronary computed tomography angiography (selective CCTA) has recently been intro- duced for on-site evaluation of coronary artery disease during coronary artery catheterization. In this study, we aimed to develop a feasible protocol for selective CCTA using ultralow-dose contrast medium as compared with conventional intravenous CCTA (IV CCTA). Materials and Methods: A novel combined system incorporating coronary angiography and a 320-detector row computed tomographic scanner was used to study 4 swine (35–40 kg) under animal institutional review board approval. A selective CCTA scan was simultaneously performed with an injection of 13.13 mgI/mL of modulated contrast medium at multiple different injection rates including 2, 3, and 4 mL/s and different total injection volumes of either 20 or 30 mL. Intravenous CCTA was performed with 60 mL of contrast medium, followed by 30 mL of saline chaser at 5 mL/s. Coronary mean and peak intensity, transluminal attenuation gradient, as well as 3-dimensional maximum intensity projections were obtained. Results: Attenuation values (mean ± standard error, in Hounsfield units [HUs]) of selective CCTA for the left anterior descending (LAD) and right coronary ar- tery (RCA) using the various combinations of injection rates and total injection volumes were as follows: 20 mL at 2 mL/s (LAD, 270.3 ± 20.4 HU; RCA, 322.6 ± 7.4 HU), 20 mL at 3 mL/s (LAD, 262.9 ± 20.4 HU; RCA, 264.7 ± 7.4 HU), 30 mL at 3 mL/s (LAD, 276.8 ± 20.4 HU; RCA, 274.0 ± 7.4 HU), 20 mL at 4 mL/s (LAD, 268.0 ± 20.4 HU; RCA, 277.7 ± 7.4 HU), and 30 mL at 4 mL/s (LAD, 251.3 ± 20.4 HU; RCA, 334.7 ± 7.4 HU). The representative protocol of the selective CCTA studies produced results within the optimal en- hancement range (approximately 250-350 HU) for all segments, and comparison of transluminal attenuation gradient data with selective CCTA and IV CCTA studies demonstrated that the former method was more homogenous (-1.5245 and -1.7558 for LAD as well as 0.0459 and 0.0799 for RCA, respectively). Notably, the volume of iodine contrast medium used for selective CCTA was reported to be 1.09% (0.2 g) of IV CCTA (24 g). Conclusions: The current findings demonstrate the feasibility of selective CCTA using ultralow-dose intracoronary contrast injection. This technique may provide additional means of coronary evaluation in patients who may require strategic planning before a procedure using a combined modality system. Key Words: computed tomography, catheter, coronary angiography, contrast media (Invest Radiol 2015;50: 449–455) C onventional invasive coronary angiography has been established as the criterion standard for the evaluation and treatment of coronary artery disease (CAD). 1,2 However, it can only provide a 2-dimensional lumenographic evaluation. Additional imaging acquisition modali- ties such as intravascular ultrasound (IVUS) 3 and optical coherence tomography (OCT) 4 have been adjunctively used for evaluation of cross-sectional luminal area, atherosclerotic plaque burden, and plaque characterization. This information may be crucial for successful revas- cularization while minimizing the risk for complications. 5 Despite their efficacies, these modalities have several inherent limitations including high costs and high procedural risk based on their invasive nature. 6 Recently, intravenous coronary computed tomography angiogra- phy (IV CCTA) has emerged as an attractive alternative for accurate assessment of luminal stenosis 7,8 as well as atherosclerotic plaque mor- phology and vulnerability. 9,10 The CCTA has shown similar results in the assessment of minimal luminal area and area stenosis compared with IVUS in patients with acute chest pain, as well as providing hemo- dynamic information such as myocardial perfusion 11 and computed tomography (CT)-based fractional flow reserve 12 calculations. This anatomical and physiological information can be used for procedural planning before coronary intervention. Despite these advantages, the on-site CCTA is not frequently used during coronary artery cath- eterization owing to lack of access to the device, especially in cases where strategic stepwise approaches are needed for severe and com- plex CAD. 13 However, a recently introduced combined system in- corporating coronary angiography system (INFX-8000C; Toshiba Medical Systems Corporation, Otawara, Japan) and a 320-detector row CT scanner (Aquilion ONE ViSION Edition) enables the CT scan to be performed during coronary artery catheterization without the need to move the patient from the catheterization room to the CT room. In addition, it provides adjunctive information such as athero- sclerotic plaque features surrounding the luminal narrowing, hence combining noninvasive and invasive approaches that could further facilitate the coronary intervention. Received for publication August 30, 2014; and accepted for publication, after revision, February 1, 2015. From the *Brain Korea 21 PLUS Project for Medical Science, Yonsei University, Seoul; †Division of Cardiology, Department of Internal Medicine, National Health Insurance Service Ilsan Hospital, Goyang-si, Gyeonggi-do; ‡Cardiovascular Cen- ter, Myongji Hospital, Goyang-si; §Division of Cardiology, Department of Inter- nal Medicine, Severance Cardiovascular Hospital, Yonsei University College of Medicine; kDivision of Cardiology, Department of Internal Medicine, Heart Center, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, South Korea; ¶Division of Cardiology, Cedars-Sinai Medical Center, Los Angeles, CA; #Dalio Institute of Cardiovascular Imaging, New York- Presbyterian Hospital and the Weill Cornell Medical College, New York, NY; **Cardiovascular Product Evaluation Center, College of Medicine, Yonsei Uni- versity, Seoul; ††Department of Biostatistics, Bundang CHA Medical Center, Graduate School of Health and Welfare, CHA University, Seongnam; ‡‡Cardio- vascular Research Institute; §§Cardiovascular Product Evaluation Center, Yonsei University College of Medicine, Seoul; kkCHA University Graduate School of Health and Welfare, Seongnam-si; and ¶¶Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, South Korea. Conflicts of interest and sources of funding: Supported by the ICT R&D program of MSIP/IITP (10044910, Development of Multi-modality Imaging and 3D Simulation-Based Integrative Diagnosis-Treatment Support Software System for Cardiovascular Diseases). The authors report no conflicts of interest. Authors Hong and Shin contributed equally to this work as first authors. Reprints: Hyuk-Jae Chang, MD, PhD, Professor, Division of Cardiology, Department of Internal Medicine, Severance Cardiovascular Hospital, Yonsei University Col- lege of Medicine, 50 Yonsei-Ro, Seodaemun-gu, Seoul, 120–752, Republic of Korea. E-mail: hjchang@yuhs.ac. Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved. ISSN: 0020-9996/15/5007–0449 ORIGINAL ARTICLE Investigative Radiology • Volume 50, Number 7, July 2015 www.investigativeradiology.com 449 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.