title: CTA contrast enhancement of the aorta and pulmonary artery: the effect of saline chase injected at two different rates in a canine experimental model.
abstract: OBJECTIVE
  To investigate the effect of saline chase injected at 2 different rates on computed tomography (CT) angiography.
  
  
  METHODS
  This study was approved by our institutional animal study committee. Three injection protocols were used; contrast injection (24 mL, 0.8 mL/s) without saline chase (protocol A), contrast injection with saline chase injected at the same rate as the contrast medium (protocol B), and contrast injection with saline chase injected at half the rate (0.4 mL/s) of the contrast medium (protocol C). In the 3 dogs used in our study, each of the protocols was applied twice for every dog resulting in a total of 18 sessions of monitoring scans. CT images were acquired every second at the fixed level of the aorta and pulmonary artery (PA). The duration of plateau, plateau deviation, and peak arterial enhancement were computed and compared using the Kruskall-Wallis and Mann-Whitney U test.
  
  
  RESULTS
  Peak contrast enhancements were significantly more delayed with protocol B than with protocol A in both the PA (B: 48 seconds, A: 30 seconds, P=0.024) and aorta (B: 46 seconds, A: 38 seconds, P=0.024). The duration of enhancement plateau was longer with protocol B than with protocol A in PA (B: 14.8 seconds, A: 9.0 seconds, P=0.002) and in aorta (B: 16.2 seconds, A: 11.6 seconds, P=0.004). Protocol C had the longest duration of plateau in both PA (34.5 seconds, P=0.002) and aorta (33.8 seconds, P=0.004) with uniform plateau enhancement. The peak enhancement values of protocol C, however, were substantially lower than that of protocol A and B in both the PA (A: 262 HU, B: 239 HU, C: 191 HU, P=0.001) and aorta (A: 263 HU, B: 268 HU, C: 210 HU, P=0.001).
  
  
  CONCLUSIONS
  Saline chase prolongs the duration of plateau and delays peak enhancement of the pulmonary artery and aorta. Saline chase injected at half the rate of contrast medium injection allowed more uniform and prolonged plateau contrast enhancement than other protocols.
authors.affiliation: Department of Radiology and Institute of Radiation Medicine, Seoul National University College of Medicine, Jongno-gu, and Seoul National University Hospital, Healthcare Gangnam Center, Gangnam-gu, Seoul, South Korea.
authors.forename: Chang Hyun
authors.initials: CH
authors.lastname: Lee
authors.forename: Jin Mo
authors.initials: JM
authors.lastname: Goo
authors.forename: Kyongtae T
authors.initials: KT
authors.lastname: Bae
authors.forename: Hyun Ju
authors.initials: HJ
authors.lastname: Lee
authors.forename: Kwang Gi
authors.initials: KG
authors.lastname: Kim
authors.forename: Eun Ju
authors.initials: EJ
authors.lastname: Chun
authors.forename: Chang Min
authors.initials: CM
authors.lastname: Park
authors.forename: Jung-Gi
authors.initials: JG
authors.lastname: Im
mesh_terms: D000792:Angiography / Q000295:instrumentation*; D000818:Animals; D001011:Aorta / Q000473:pathology / Q000502:physiology*; D003287:Contrast Media; D004285:Dogs; D023421:Models, Animal; D011651:Pulmonary Artery / Q000473:pathology / Q000502:physiology*; D012965:Sodium Chloride / Q000008:administration & dosage*; D014057:Tomography, X-Ray Computed / Q000295:instrumentation*
chemical_list: D003287:Contrast Media; D012965:Sodium Chloride