Intra-arterial contrast enhanced computed tomography of the deep digital flexor tendon and palmar veins in the distal forelimb in Jeju horses: Evaluating contrast-enhancing factors

Background: Few studies have investigated the adequate contrast enhancement (CE) evaluation depending on concentration, volume, and rate of administration of contrast media (CM) and the scan parameters in equine contrast enhanced computed tomography (CECT). Objectives: To investigate CE of the deep digital flexor tendon (DDFT) and veins depending on the computed tomography (CT) voltage and concentration, volume, and rate of CM administration during intra-arterial CECT of equine distal forelimbs. Study Design: In vivo experiments. Methods: Six horses underwent 54 CT scans. First, the CE of DDFT and veins was evaluated depending on the voltage (80 kV and 250 mA or 120 kV and 150 mA) and CM concentration (150, 120, or 90 mg I/mL in 50 mL of CM). Second, CE of DDFT and veins was evaluated depending on the CM volume (50, 100, or 150 mL) and administration rate (2, 4, or 6 mL/s) with a fixed iodine delivery rate (IDR; 300 or 180 mg I/s). Results: Contrast enhancement of DDFT was significantly higher at 80 kV of voltage and 150 mg I/mL of CM concentration (Median: 29.65; IQR: 1.74; p < 0.05). CE of the DDFT positively correlated with CM concentration (p < 0.001; r = 0.75). At 180 mg I/s IDR, contrast attenuation in the medial and lateral palmar veins significantly decreased at a CM of 30 mg I/mL, rate of 6 mL/s, and volume of 150 mL (median and IQR: 985.93 and 71.8 Hounsfield units [HU] and 988.73 and 41.16 HU, respectively); the CE was sufficient to distinguish between the vessels and the adjacent structures. Main Limitations: The number of animals was small. Conclusions: Our results suggest that a low CM concentration could yield sufficient CE of the DDFT and arteries with adjusted CT scanning parameters or volume and injection rate of CM.