Synthetic aperture imaging in ultrasound calibration
Published in SPIE Medical Imaging, 2014
Recommended citation: Ameri G, Baxter JS, McLeod A, Jayaranthe UL, Chen ECS, Peters TM, (2014). "Synthetic aperture imaging in ultrasound calibration"; in SPIE Medical Imaging: Image-Guided Procedures, Robotic Interventions, and Modeling, 90361I, pp. 401-406. https://doi.org/10.1117/12.2043899
Ultrasound calibration allows for ultrasound images to be incorporated into a variety of interventional applica tions. Traditional Z-bar calibration procedures rely on wired phantoms with an a priori known geometry. The line fiducials produce small, localized echoes which are then segmented from an array of ultrasound images from different tracked probe positions. In conventional B-mode ultrasound, the wires at greater depths appear blurred and are difficult to segment accurately, limiting the accuracy of ultrasound calibration. This paper presents a novel ultrasound calibration procedure that takes advantage of synthetic aperture imaging to reconstruct high resolution ultrasound images at arbitrary depths. In these images, line fiducials are much more readily and accu rately segmented, leading to decreased calibration error. The proposed calibration technique is compared to one based on B-mode ultrasound. The fiducial localization error was improved from 0.21mm in conventional B-mode images to 0.15mm in synthetic aperture images corresponding to an improvement of 29%. This resulted in an overall reduction of calibration error from a target registration error of 2.00mm to 1.78mm, an improvement of 11%. Synthetic aperture images display greatly improved segmentation capabilities due to their improved resolution and interpretability resulting in improved calibration.