Characterization of the Intel RealSense D415 stereo depth camera for motion-corrected CT imaging

![CDATA[A combination of non-contrast CT (NCCT) and CT Perfusion (CTP) imaging is the most common regime for evaluation of acute ischemic stroke patients. CTP-based image analysis is known to be compromised by patient head motion. However, there is currently no technique to compensate for intra-frame head motion during CTP acquisition. In this work, we investigated the feasibility of using the small form factor Intel RealSense D415 stereo depth camera to obtain accurate head pose estimates for intra-frame motion correction in CTP. First, we quantitatively evaluated head movement in a cohort of 72 acute stroke cases. Then we characterized the performance of the Intel D415 against ground-truth robotic motion and the clinically validated OptiTrack marker-based motion tracking system. The results showed that head motion during CTP imaging of acute stroke of patients is extremely common, with around 50% of patients moving > 5 mm and 1 deg and around 20% moving 10-100 mm and rotating 3-20 deg. The pose accuracy of the Intel for controlled robotic motion was approximately 5 mm and 2 deg. For translations and rotations, respectively. For human head motion using the OptiTrack as ground truth, the accuracy was approximately 4 mm (except for lateral motion) and 1.25 deg, respectively. Although poorer than what is needed clinically, there is a lot of potential to optimize performance and potentially achieve an accuracy consistently around 1 mm and 1 deg.]]