Accelerated Digitally Reconstructed Radiograph Generation Scheme for 2D to 3D Image Registration of Vertebrae Based on Sparse Sampling and Multi-Resolution

Recent advancements in spine surgery use image guided intervention systems to enhance surgical accuracy for incorporating pedicle screw constructs. Two-dimensional (2D) to three-dimensional (3D) image registration helps in treatment planning and verification by mapping the Digitally Reconstructed Radiograph (DRR) images, rendered from 3D CT volumetric data to 2D C-arm images. Conventional approach of ray casting which is followed for DRR generation helps to reduce the risk of wrong site surgery and provide superior accuracy. However, it consumes significant amount of time due to complex computational intensity. An effective method is proposed to reduce the time taken for DRR generation by exploiting the redundant information hidden in the CT images with the help of sparse sampling and multi-resolution using Discrete Wavelet Transform. Beginning with 2D to 3D image registration methods, this study emphasizes on acceleration of DRR by spatial and temporal resolution of sagittal slices of the CT data, while maintaining the quality consistent with that needed for image registration. This method was found to generate DRR at a much faster rate of 84%.