Computed tomographic angiography facilitates the identification of complex cardiovascular malformations and provides, even for small animals, accurate information on the location, size, and number of intra- and extracardiac masses; density and characteristics of contrast enhancement; and delineation of adjacent anatomic structures.1–5
The main goal of CT angiography is to facilitate detection of pathological changes in the cardiovascular system by providing adequate and prolonged contrast enhancement within an anatomic ROI.6,7 The quality of contrast enhancement achieved is influenced by contrast medium–related factors (eg, concentration, volume, injection rate, injection bolus protocol, and whether a flush solution is used), patient-related factors (eg, cardiac output, cardiovascular circulation, age, and body weight), and CT scanning factors (eg, scan duration, equipment used [multi-detector- vs monodetector-row CT], scan delay [interval from initiation of contrast medium injection to image acquisition], and method used to control the timing of contrast medium arrival at the ROI [test bolus vs bolus-tracking method]).8–11
In human medicine, protocols for contrast medium injection have been evaluated for use in cardiac CT angiography. With a traditional uniphasic injection protocol, the resulting cardiac enhancement profile consists of a single peak in the degree of enhancement within the ROI followed by a rapid decrease once injection is complete. This profile reflects the rapid distribution of contrast medium away from the cardiovascular system.10 Consequently, nonuniform cardiovascular enhancement occurs during image acquisition when a uniphasic injection protocol is used.10 A modified version of the uniphasic injection protocol, the multiphasic approach, includes flushing with saline (0.9% NaCl) solution or diluted contrast medium after injection of the original contrast medium to prolong the duration of contrast enhancement.11 In veterinary medicine, a few CT protocols have been evaluated for contrast enhancement of the caudal vena cava, abdominal aorta, and pulmonary artery.8,10 However, to the authors’ knowledge, a protocol for performing cardiac CT angiography has not been reported for veterinary species.
A method is needed to help discriminate intra- and extracardiac structures in dogs better than is achieved with echocardiography. The purpose of the study reported here was to establish a protocol for CT angiography to facilitate cardiac examination, including dose and concentration of iodine to be used and total volume of contrast solution to be administered. We also sought to use information from TAC analyses to determine a scan delay that would allow adequate and consistent cardiovascular enhancement.
Supported in part by the Animal Medical Institute of Chonnam National University.
Presented in part at the American College of Veterinary Radiology Annual Scientific Conference, Savannah, Ga, October 2013.
Region of interest
Omnihexol 300, Korea United Pharm Co, Seoul, Republic of Korea.
Domitor, Orion Corp, Espoo, Finland.
Zoletil, Virbac, Carros, France.
BD Angiocath Plus, Becton Dickinson Infusion Therapy Systems Inc, Singapore, Republic of Singapore.
Somatom Emotion, Siemens Medical Systems, Erlangen, Germany.
VP-1200/1000, Votem, Chuncheon, Republic of Korea.
Medrad Vistron C-T Injector System, Medrad Inc, Indianola, Pa.
SPSS, version 20, IBM Corp, Armonk, NY.
SigmaPlot, version 10.0, Systat Software Inc, Calif.
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Characteristics of various formulations of iohexol solutions evaluated for use in performing cardiac CT angiography in 4 clinically normal Beagles.
|Iodine dose (mg/kg)||Dilution||Total volume (mL/kg)||Iodine concentration (mg/mL)||Total volume per dog (mL)*||Injection duration (s)*|
|300||Undiluted||1.0||300||11.50 ± 0.50||4.00 ± 0.00|
|1:1||2.0||150||23.00 ± 1.00||8.00 ± 0.00|
|1:2||3.0||100||34.50 ± 1.50||11.50 ± 0.50|
|1:3||4.0||75||46.00 ± 2.00||15.50 ± 0.50|
|400||Undiluted||1.3||300||14.75 ± 0.83||5.25 ± 0.43|
|1:1||2.7||150||29.50 ± 1.66||10.25 ± 0.43|
|1:2||4.0||100||44.25 ± 2.49||14.75 ± 0.83|
|1:3||5.3||75||59.00 ± 3.32||19.75 ± 0.83|
|800||Undiluted||2.7||300||29.75 ± 1.79||10.50 ± 0.50|
|1:1||5.3||150||59.50 ± 3.57||20.25 ± 1.30|
|1:2||8.0||100||89.25 ± 5.36||29.75 ± 1.79|
|1:3||10.7||75||119.00 ± 7.14||39.90 ± 2.62|
For all contrast imaging procedures, iohexol (300 mg/mL) was administered via a cephalic vein at a rate of 3 mL/s.
Values are mean ± SD.