Combined assessment of blood flow and tissue perfusion in diabetic feet using intra-arterial 4D contrast CT angiography and perfusion

*Purpose: To employ dynamic computed tomography angiography (CTA) imaging and perfusion (CTP) imaging for improved anatomic and hemodynamic information in patients with foot ulcers for optimal treatment planning using low-volume intra-arterial contrast injections. *Materials and methods: Dynamic 4D CT data (Aquilion ONE Genesis, Canon) of the ankle and feet were acquired during intra-arterial digital subtraction angiography (IADSA) examinations of the lower extremities. During the IADSA examinations, a Simmons-2, 5 Fr Catheter (Cook Medical) was introduced into the external iliac. At the start of the CT acquisitions, two mL of contrast agent (Ultravist 370) diluted with 18 mL of saline was injected at a rate of 4.0 mL/s during 5 s. The combined CTA and CTP protocol consisted of multiple 160 mm axial series at 0.52 s tube rotation. Firstly, a 40 s continuous acquisition was performed, followed by 16 repeated acquisitions with a 2 s interphase delay and 7 acquisitions using a 5 s interval. Finally, 6 additional acquisitions were made at a 15 s interval to capture the tissue perfusion. The total scan time was 194 s. The foot was segmented into five volumes of interest (VOI), according to the angiosome concept. Their corresponding input arteries were determined, and time-attenuation curves (TAC) were automatically generated to calculate the arrival time of the contrast bolus (TTP). A voxelwise assessment of the blood flow was performed using the slope method and the arterial input function. Perfusion values (mL/g.s) of healthy tissue and wounds were compared using a Mann-Whitney U test (SPSS, IBM). *Results: Three patients with clinically suspected peripheral arterial disease showing small necrotic foot ulcers received a 4D CT examination combined with a IADSA examination. Blood flow was assessed successfully and based on the TTP values, arteries and veins could clearly be distinguished. In all patients, the perfusion values in the affected tissue were significantly higher (p< 0.001) compared to adjacent healthy areas (Table 1). *Conclusion: The 4D CT protocol combined with the minimal usage of contrast agent (2 mL) provides novel information as three phases (arterial, perfusion and venous) are captured in 3D.