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What is the effect of injection rate and recumbency on thoracic perfusion for CT?

AJVR 2024

Hyunju Hwang DVM, MS , Changhyeon Cho DVM , Myounghun Ki DVM , Wonbeom Jun PhD , Hackjoon Shi PhD , Jaehwan Ki DVM, PhD, and Kidong Eo DVM, PhD

Background: The study investigates the impact of scanning position and contrast medium injection rate on pulmonary CT perfusion (CTP) images in healthy Beagles. Aimed to establish reference ranges for perfusion parameters based on the pulmonary parenchymal location, contributing to differential diagnosis in small-breed dogs.

Methods: Involved 7 healthy Beagles undergoing CTP imaging under various conditions, including different recumbencies and injection rates. Parameters like initial time of venous enhancement, peak time of arterial enhancement, and peak enhancement values were measured.

Results: Significant variations in perfusion mapping parameters were observed based on the pulmonary parenchymal location. Dorsal recumbency showed lower peak arterial enhancement compared to sternal recumbency. No significant differences in perfusion mapping parameters were found based on position, except for pulmonary blood volume and time to peak.

Limitations: The study is limited by the small sample size and the focus on only healthy Beagles, which may not represent all canine breeds or diseased states.

Conclusions: The recommended CTP imaging approach in dogs is a low injection rate of 1.5 mL/s in sternal recumbency. This study provides valuable reference ranges for perfusion parameters, aiding in the application of pulmonary CTP imaging for veterinary patients.

Representative transverse thoracic postcontrast CT (A) and CT perfusion mapping images of pulmonary blood flow (mL/100 mg/min; B), pulmonary blood volume (mL/100 mg; C), mean transit time (s; D), time to maximum of residual function (s; E), and time to peak of tissue (s; F) of the dog described (Figure 1), positioned in sternal recumbency and given iohexol (Omnipaque; GE Healthcare; 300 mg iohexol/mL; 1 mL/kg, IV; 1.5 mL/s). The images were obtained at the level of bronchus bifurcation, with the dog in sternal recumbency. The dog’s right is toward the left in all images. A—window width, 1,500 HU; window level, −400 HU; 0.5-mm slice thickness. B–F— The color scale toward the right in each image represents the respective perfusion parameter from low (black) to high (red).

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