Correction of motion tracking errors for PET head rigid motion correction

Abstract

Objective. In positron emission tomography (PET) rigid motion correction, erroneous tracking information translates into reduced quality in motion corrected reconstructions. We aim to improve the accuracy of the motion tracking data, to improve the quality of motion corrected reconstructions.Approach. We developed a method for correction of marker/skin displacement over the skull, for tracking methods which require multiple markers attached on the subject head. Additionally, we correct for small magnitude (∼1-2 mm) residual translation tracking errors that can still be present after other corrections. We performed [¹⁸F]FDG scans in awake mice (n= 8) and rats (n= 8), and dynamic [¹⁸F]SynVesT-1 scans in awake mice (n= 8). Head tracking was performed with the point source tracking method, attaching 3-4 radioactive fiducial markers on the animals' heads. List-mode even-by-event motion correction reconstruction was performed using tracking data obtained from the point source tracking method (MC), tracking data corrected for marker displacement (MC-DC), and tracking data with additional correction for residual translation tracking errors (MC-DCT). Image contrast, and the image enhancement metric (IEM, with MC as reference) were calculated in these 3 reconstructions.Main results. In mice [¹⁸F]FDG scans, the contrast increased on average 3% from MC to MC-DC (IEM: 1.01), and 5% from MC to MC-DCT (IEM: 1.02). For mice [¹⁸F]SynVesT-1 scans the contrast increased 6% from MC to MC-DC (IEM: 1.03), and 7% from MC to MC-DCT (IEM: 1.05). In rat [¹⁸F]FDG scans contrast increased 5% (IEM: 1.04), and 9% (IEM: 1.05), respectively.Significance. The methods presented here serve to correct motion tracking errors in PET brain scans, which translates into improved image quality in motion corrected reconstructions.

Keywords: PET; brain; motion correction; motion tracking.