An ultrasound localization system for endovascular aortic aneurysm repair

Image guidance is crucial to minimally invasive surgery. This dissertation describes a novel ultrasound-based localization system to guide catheter based repair of abdominal aortic aneurysm. Chapter 1 provides background on the clinical significance of abdominal aortic aneurysm, the state of the art for interventional tool tracking and summarizes the technical contributions of this work. Chapter 2 describes the Ultrasound Localization System (ULS) in detail; it covers the real-time signal pathway from raw ultrasound data to location coordinates. The in vitro experiments show that the ULS is capable of tracking in water with 1.05 mm accuracy and with a layer of intervening pork tissue with 3.23 mm accuracy. Chapter 3 describes a pilot in vivo study using the ULS in conjunction with pre-operative CT imaging data to deploy a stent-graft in a live pig. The results showed tracking was feasible but pig bowel gas reduced system SNR. Chapter 4 describes a design revision to the ULS based on the pilot in vivo study and follows with further in vitro validation of the new design, presenting various filtering strategies to smooth motion in the presence of noise. Chapter 5 describes the second in vivo pig study, using the revised ULS described in the previous chapter as well as the third pig study, using a yet further rened version of the ULS and an intuitive, virtual "endoluminal" view. The results show that the ULS system is accurate to within 1 mm of fluoroscopy and capable of delivering aortic stent-grafts within 1 cm of the intended target. Chapter 6 concludes this dissertation and suggests future work, which is required to address ultrasound-tool miniaturization and image registration.