Tomographic Ultrasound Angiography for Peripheral Artery Disease

Abstract

Introduction - Imaging the calf and foot arteries is essential prior to treatment of peripheral artery disease whether by angioplasty or surgical bypass [1]. Tomographic ultrasound (tUS) is a novel and entirely safe 3-D imaging modality, with no exposure to ionising radiation or nephrotoxic contrast. We compared sulphur hexafluoride (Sonovue) contrast enhanced tUS (CEtUS) with angiography for imaging the arteries below the knee. Methods - Eleven patients with PAD scheduled to undergo peripheral artery reconstruction or interventional procedures being assessed by CT, MR or catheter angiography, underwent CEtUS performed by an experienced vascular scientist within the same week. 2mL bolus injections of Sonovue were given intra-venously which allowed CEtUS of two calf or foot arteries per administration with a maximum of 5mL administered per patient. CEtUS and angiography images were then compared using the validated Society of Vascular Surgery (SVS) run off score, assuming angiography to be the gold standard. Results - The mean (±sd) score for the popliteal and tibio-peroneal trunk with angiography was 1.03±1.35 compared with 0.53±1.11 using CEtUS showing complete agreement. For the anterior and posterior tibial arteries, the mean scores for angiography and CEtUS were 0.89±1.17 and 1.28±1.29 respectively, with the score for angiography being 0.39±0.91 lower than that with CEtUS. Four peroneal arteries could not be identified due to vessel depth on ultrasound using an 11MHz transducer; this problem was resolved by changing to a 9MHz transducer. Mean score for the Plantar arch and dorsalis pedis was -0.43±1.05 demonstrating good agreement. An effective paired Wilcoxon test for the score difference between modalities demonstrates a p value of 0.9063 which is not significantly different (NS). Conclusion - CEtUS is a novel imaging modality that achieves clear peripheral and foot images without exposing patients to ionising radiation or nephrotoxic X-ray contrast media. Patients should be scanned with a 9MHz linear ultrasound transducer to ensure adequate penetration and visualisation of the deeper calf arteries. As surgeons can see and interpret these images, CEtUS may replace MR and CT angiography.