Optimizing lower extremity CT angiography: A prospective study of individualized vs. fixed post-trigger delays in bolus tracking.

Purpose: To compare the contrast media opacification and diagnostic quality in lower-extremity runoff CT angiography (CTA) between bolus-tracking using conventional fixed trigger delay and patient-specific individualized post-trigger delay.

Methods: In this prospective study, lower-extremity runoff CTA was performed in two cohorts, using either fixed or individualized trigger delay. Both cohorts had identical CT protocols, contrast media applications, and image reconstructions. Objective image quality (mean contrast opacification in HU), and subjective image quality (5-point Likert-scale), were assessed in six vessels: abdominal aorta (AA), common iliac artery (CIA), superficial femoral artery (SFA), popliteal artery (PA), posterior tibial artery (PTA), and dorsalis pedis artery (DPA) by one rater for objective and two raters for subjective image quality. Objective image quality was analyzed using Student t-tests, while subjective ratings were compared with Fisher's exact test.

Results: Overall, 65 patients were included (mean age: 71 ± 14; 39 men), 35 in the individualized cohort and 30 in the fixed cohort. No differences were found between the groups regarding demographics or radiation exposure. Individualized trigger delay ranged from 2 to 23 s (mean: 8.7 ± 4.0 s) and was 10 s in the fixed cohort. The individualized cohort showed higher opacification in the peripheral arteries (PTA: 479 ± 140 HU vs. 379 ± 106 HU; p = 0.009; DPA: 477 ± 191 HU vs. 346 ± 137 HU; p = 0.009). Overall subjective "image quality" was rated higher in the individualized group ("excellent" or "good" in Rater 1: 97 % vs. 57 %; p < 0.001; and Rater 2: 89 % vs. 53 %; p = 0.002).

Conclusion: Individualized post-trigger delay enhances diagnostic quality, by improving vessel opacification in peripheral arteries and increasing subjective image quality in lower extremity runoff CTA.