B-splines Coupled with Quadrature Texture to Register Prostate Multimodal Images

Needle biopsy of the prostate is guided by Transrectal Ultrasound (TRUS) imaging. The TRUS images do not provide proper spatial localiza- tion of malignant tissues due to the poor sensitivity of TRUS to visualize early malignancy. Magnetic Reso- nance Imaging (MRI) has been shown to be sensitive for detection of early stage malignancy and therefore, a novel 2D deformable registration method that overlays pre-biopsy MRI onto TRUS images has been proposed. Method: The registration method involves B-spline de- formations with Normalized Mutual Information (NMI) as similarity measure computed from the tex- ture images obtained from the amplitude responses of the directional quadrature filter pairs. Registration ac- curacy of the proposed method is evaluated by com- puting the Dice Similarity coefficient (DSC) and 95% Hausdorff Distance (HD) values for 20 patient datasets and Target Registration Error (TRE) for 18 patients only where homologous structures are visible in both the TRUS and transformed MR images. Results: The proposed method and B-splines using NMI computed from intensities provide average TRE values of 2.64±1.37 mm and 4.43±2.77 mm respectively. Our J. Mitra*, R. Mart'i, A. Oliver, X. Llad'o, S. Ghose Universitat de Girona,Computer Vision and Robotics Group, Girona, Spain. E-mail: jhimlimitra@yahoo.com, marly@eia.udg.edu, aoliver@eia.udg.edu, llado@eia.udg.edu, soumyaghose@gmail.com J. C. Vilanova Cl'inica Girona, Girona, Spain. E-mail: kvilanova@comg.cat F. Meriaudeau *Universit'e de Bourgogne, Le2i-UMR CNRS 5158, Le Creusot, France. E-mail: fabrice.meriaudeau@u-bourgogne.fr method shows statistically significant improvement in TRE when compared to B-spline using NMI computed from intensities with Student's t-test p = 0.02. The proposed method shows 1.18 times improvement over Thin-plate splines registration with average TRE of 3.11±2.18 mm. The mean DSC and the mean 95% HD values obtained with the proposed method of B-spline with NMI computed from texture are 0.943±0.039 and 4.75 ± 2.40 mm respectively. Conclusions: The texture energy computed from the quadrature filter pairs provides better registration ac- curacy for multimodal images than raw intensities. Low TRE values of the proposed registration method adds to the feasibility of it being used during TRUS guided biopsy.