Real-time B-mode ultrasound image simulation and artifacts modelling of needles and brachytherapy seeds

Abstract

The training of ultrasound guided interventional procedures could benefit from ultrasound simulators that synthesize realistic-looking B-mode images of tissue and interventional tools, such as the needle. For a prostate brachytherapy simulator in particular, both the needle and seed images need to be synthesized. In this thesis, we propose an interpolation-based method for simulating needle and seed B-mode images in real time. We parametrize a needle or a seed B-mode image as a function of its position and orientation. We collect needle and seed images under various spatial configurations in a water-tank using a needle guidance robot. Then we use multi-dimensional tensor-product interpolation to simulate images of needles and seeds with arbitrary poses and positions using collected images. After further processing, the interpolated needle and seed images are superimposed on top of phantom or tissue image backgrounds. The similarity between the simulated and the real images is measured using a correlation metric. The results are also compared to in vivo images. Images in both the transverse and the sagittal planes are simulated. Artifacts associated with the needle and seed are studied in detail by experiments and by physical models. It is demonstrated that the bright band pattern associated with the sagittal needle images could be interpreted using a plate reflection model; the bright tails associated with the transverse needle images could be analyzed by simulating the back-scattered stress field from a sphere.