Soaring with TRILLI: An HW/SW Heterogeneous Accelerator for Multi-Modal Image Registration

3D rigid image registration is a pivotal procedure in computer vision that aligns a floating volume with a reference one to correct positional and rotational distortions. It serves either as a stand-alone process or as a pre-processing step for non-rigid registration, where the rigid part dominates the computational cost. Various hardware accelerators have been proposed to optimize its compute-intensive components: geometric transformation with interpolation and similarity metric computation. However, existing solutions fail to address both components effectively, as GPUs excel at image transformation, while FPGAs in similarity metric computation. To close this gap, we propose TRILLI, a novel Versal-based accelerator for image transformation and interpolation. TRILLI optimally maps each computational step on the proper heterogeneous hardware component. TRILLI achieves speedup of 5.32x against the top performing GPU-based solution, and an energy efficiency improvement of 36.75x against the most efficient one. Moreover, we integrate it with an FPGA-based similarity metric from literature to complete a rigid image registration step (i.e., transformation, interpolation, and similarity metric) attaining a speedup of 18.60x against the top performing GPU-based solution, while being 36.11x more efficient than the most energy efficient one.