Effect of Contrast Medium Injection Duration on Peak Enhancement and Time to Peak Enhancement of Canine Pulmonary Arteries

Abstract

Our goal was to investigate the effect of contrast medium injection duration on pulmonary artery peak enhancement and time to peak enhancement. Fourteen dogs were allocated into one of seven predefined weight categories, each category contained two dogs. Dogs in each weight category were assigned to group A or B. Animals in each group received a different contrast medium injection protocol. In group A, a fixed injection rate of 5 ml/s was used. In group B, the contrast injection rate was calculated as follows: flow rate= contrast volume/scan duration + 10s. Time to peak enhancement and peak enhancement of the main left and right pulmonary arteries were measured on single-level, dynamic CT images for a fixed time of 30s. Rank correlation (Spearman's) coefficients between injection duration and time to peak enhancement and between body weight and peak enhancement were calculated. For group A, there was a significant negative correlation between peak enhancement and weight (r = -0.94; P = 0.005), while for group B, there was no significant correlation (r = -0.64 and P = 0.18). There was a significant correlation between time to peak enhancement and injection duration in both groups (group A: r = 0.99; P = 0.006 and group B: r = 0.85; P = 0.02). In conclusion, injection duration is a key feature in a CT angiography injection protocol. A protocol with an injection duration adjusted to the scan duration seems to be particularly suitable for veterinary applications where a population with great weight variability is studied.

Invited Review—computed Tomographic Angiography (Cta) of the Thoracic Cardiovascular System in Companion Animals

“…U ntil recently, CT applications for the thorax were mostly limited to morphologic evaluation of the chest wall, mediastinum, vessels, and lung parenchyma for differentiating normal from pathological conditions in companion animals . With the increased availability of multidetector‐row CT (MDCT) scanners with up to 320 detector rows that allow image acquisition with high temporal and spatial resolution, the utilization of this modality will likely rise for evaluating the thoracic cardiovascular system in companion animals and has been used in initial case reports and studies …”

Comparison Between Bolus Tracking and Timing‐bolus Techniques for Renal Computed Tomographic Angiography in Normal Cats

“…17 With adjusted injection rates, injection durations tend to be longer producing enhancement profiles that are delayed and broader (i.e., last longer), thereby decreasing the likelihood of missing arterial enhancement at the scanned arterial phase. 9 With both techniques, there was no statistically significant difference in attenuation between ipsilateral renal arteries and veins at the scanned arterial phase. With the timing-bolus technique, this is likely due to the lack of arterial enhancement due to delayed arrival of contrast material in three of the nine patients.…”

Dynamic computed tomographic determination of scan delay for use in performing cardiac angiography in clinically normal dogs

“…The blood recirculation visibly enhanced with contrast medium may contribute to the overall pattern of contrast enhancement obtained during CT image acquisition. 8 When contrast medium is injected at a constant rate for a prolonged versus brief period, freshly injected contrast medium and recirculating contrast medium already dispersed through the body mix and accumulate, resulting in a more gradual increase in aortic enhancement with time. Without this recirculation, the TAC for aortic contrast enhancement would consist of a rapid increase followed by a uniform, steady-state plateau with a flat, broad peak as the rate of contrast medium clearance from the central blood compartment equilibrates with the injection rate of contrast medium.…”

“…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 intraand extracardiac structures in dogs better than is achieved with echocardiography.…”

“…(Am J Vet Res 2015;76:694-701) circulation, age, and body weight), and CT scanning factors (eg, scan duration, equipment used [multidetector-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][9][10][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.…”