Multimodal Prostate Registration Using Thin-Plate Splines from Automatic Correspondences

Registration is an important step during prostate biopsy with interventional Ultrasound (US) to project the Magnetic Resonance (MR) information of the corresponding slice of a pre-acquired MR volume of the same patient. This paper presents a method of deformable registration between US and MR prostate modalities using Thin-Plate Splines (TPS). The use of radial-basis functions such as splines is a typical approach for deformable registration wherein, TPS are more computationally efficient than Bsplines. However, registration with TPS employs strategic choice of correspondence points in the moving and reference images and therefore, has been rarely used by researchers for prostate registration. Aiming to deal with this issue, a novel method to automatically choose correspondence points (control points) based on the prostate geometry is presented in this paper. Shepard´s interpolation is used with the TPS in order to deal with the interpolation artifacts produced by reverse TPS transform. To evaluate the accuracy of our correspondence generation method, two intuitive geometric methods for prostate contour sampling are also implemented. Our registration results are validated using 4 patient datasets obtaining an average DSC of 0.97 ± 0.01.