Subtraction CT Angiography for the Evaluation of Lower Extremity Artery Disease with Severe Arterial Calcification

(1) Background: Peripheral arterial CT angiography (CTA) is an alternative to conventional angiography for diagnosing lower extremity artery disease (LEAD). However, severe arterial calcifications often hinder accurate assessment of arterial stenosis. This study evaluated the diagnostic performance of subtraction CTA with volume position matching compared to conventional CTA, using invasive digital subtraction angiography (DSA) as the gold standard. (2) Methods: Thirty-two patients with LEAD (mean age: 69.6 ± 10.8 years; M/F = 28:4) underwent subtraction CTA and DSA. The arterial tree was divided into 20 segments per patient, excluding segments with a history of bypass surgery. Subtraction was performed separately for each limb using volume position matching. Maximum intensity projections were reconstructed from both conventional and subtraction CTA data. Percent stenosis per arterial segment was measured using calipers and compared with DSA. Segments were classified as stenotic (>50% luminal narrowing) or not, with heavily calcified or stented segments assigned as incorrect. (3) Results: Of 640 segments, 636 were analyzed. Subtraction CTA and conventional CTA left 13 (2.0%) and 160 (25.2%) segments uninterpretable, respectively. Diagnostic accuracies (accuracy, precision, recall, macro F1 score) for subtraction CTA were 0.885, 0.884, 0.936, and 0.909, compared to 0.657, 0.744, 0.675, and 0.708 for conventional CTA. (4) Conclusions: Subtraction CTA with volume position matching is feasible and achieves high diagnostic accuracy in patients with severe calcific sclerosis.