tMIP-CTA Application in Infra-knee Artery Angiography for Diabetic Lower Extremity Disease

To investigate the feasibility of time-resolved maximum intensity projection computed tomography angiography (tMIP-CTA) in assessing below-the-knee arterial lesions in diabetic patients. A prospective study enrolled 79 patients (53 males, 26 females; mean age 71.6 ± 10.2 years) with diabetic foot and lower extremity vascular disease between June 2023 and May 2024. Standard lower extremity arterial CTA was performed, followed by a low-dose dynamic CTA scan after a 5-min delay. tMIP images were generated by fusing data points from the time when the maximum CT value was reached during the enhancement process. Patients were divided into three groups: Group A (D-CTA, optimal phase of dynamic CTA), Group B (tMIP-CTA, full-phase maximum intensity projection CTA), and Group C (S-CTA, standard CTA). Regions of interest (ROIs) were selected in the popliteal, anterior tibial, peroneal, posterior tibial, and tibiofibular trunk arteries. Arterial vessel CT values and image noise (IN) were measured, and signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. A 5-point scale was used for subjective scoring of each segment of the below-the-knee arteries. Statistical analyses were performed to compare objective indicators and subjective scores. Differences in below-the-knee arterial stenosis severity, collateral vessels, distal foot artery visualization, and lower extremity venous contamination were also compared. Group B exhibited significantly lower IN, higher muscle CT values, SNR, and CNR compared to groups A and C, with statistically significant differences (p < 0.05). The diagnosability rate of below-the-knee arteries was significantly higher in group B than in group C (p < 0.01). There were no significant differences in subjective scores for stenosis severity among the three groups for bilateral below-the-knee arteries. Strong inter-observer agreement was observed in subjective scoring of below-the-knee arterial image quality (weighted kappa values of 0.919, 0.957, and 0.960, respectively). Compared to group C, group B showed significantly reduced lower extremity venous contamination (p < 0.05) and a significantly higher number of visualized foot arteries (p < 0.05). The number of visualized collateral vessels was higher in group B than in group C, although the difference was not statistically significant. The tMIP-CTA technique significantly improves image quality in below-the-knee arterial imaging for patients with diabetic foot and lower extremity vascular disease. It offers higher reliability in assessing arterial stenosis and enhances the visualization of foot arteries and small collateral vessels.