Introduction
Computed tomography (CT) is a valuable diagnostic modality for images of the musculoskeletal system, particularly for osseous changes. Recently, with technological developments, CT has been used to generate images of adequate quality to evaluate soft tissues, especially with contrast enhancement (CE) (Jones et al. , 2019, Pauwels et al ., 2021, Puchalski et al. , 2009, van Hamel et al ., 2014). Sunagawa et al . reported that three-dimensional CT images identified ruptures of the flexor tendon in the hand and wrist in human adults (Sunagawa et al ., 2003). Likewise, equine CT and contrast-enhanced CT (CECT) reportedly generate adequate images to reveal lesions in the deep digital flexor tendon (DDFT) (Jones et al. , 2019, van Hamel et al ., 2014, Vallance et al.,  2012), indicating that CT is an excellent modality to evaluate bone and soft-tissue lesions.
Jeju horse is a native breed of Jeju island in Korea, with a mean height and body weight are 123.72 cm and 267.00 kg, respectively (Oh et al ., 2014, Kong et al ., 2011). Since being used for racing, the number and value of Jeju horses have increased, resulting in an increase in admissions to equine hospitals. However, research on diseases or diagnostic modalities in these horses remains limited.
MRI is still considered a golden standard for evaluating the musculoskeletal system. However, considering the prolonged anaesthesia duration (Jone et al. , 2019) and facility limitation, CECT can be an alternative diagnostic modality to MRI for assessing the equine distal limbs (Jones et al. , 2019, Puchalski et al ., 2007, Puchalski et al ., 2009, Puchalski 2012, van Hamel et al.,2014). To the best of our knowledge, no research has reported on the evaluation of CE in horses with different scanning parameters, concentrations, rates, and volumes of CM. In humans, low voltage and CM concentration can generate adequate CE to evaluate images in previous reports (Van Cauteren et al ., 2018). Several reports on CECT in horses used different CM concentrations (Puchalski et al ., 2007, Puchalski et al ., 2009, Puchalski et al. , 2017, Pauwelset al. , 2021, Vallance et al., 2012 a and b, van Hamel et al., 2014). In those reports, CM concentration, rate, and scanning parameters were 150−185 mg I/mL, 2−3 mL/s, and 120−140 kV, respectively. This report evaluated the CE of the DDFT and arteries using different CM concentrations, rates, volumes, and scanning parameters, providing practical information and the potential to use different scanning parameters and CM concentrations.