Free-hand 3D ultrasound imaging for vascular access.

Vascular access is required to draw the patient's blood into the dialysis machine and return the filtered blood to the patient during hemodialysis to treat end-stage renal disease. The most reliable vascular access is the arteriovenous fistula (AVF), which unfortunately may develop significant stenosis or obstruction as a major complication. To evaluate the AVF geometry for potential pathological features, this study aims to develop and validate a free-hand 3D ultrasound imaging system using conventional 2D ultrasound scanning with scanner motion data from an electromagnetic (EMT) sensor to spatially register the 2D image planes into a 3D image reconstruction. To temporally synchronize the 2D ultrasound images with the EMT motion data, we developed a scanning protocol that would be practical for clinical settings to simultaneously generate data features in both ultrasound scan data and EMT tracking data. The accuracy and reliability of free-hand 3D ultrasound imaging were assessed using a wire phantom and an AVF ultrasound phantom. The results show that the average normalized root mean square errors of the 3D reconstructed models compared to the wire phantom and the AVF phantom are 0.497 ± 0.144 % and 0.571 ± 0.127 %, respectively, which indicates a high degree of accuracy and consistency. This study demonstrated the efficacy and potential clinical feasibility of using a 2D ultrasound scanner and EMT sensing for free-hand 3D ultrasound imaging of AVF for vascular access monitoring.