Abstract
Background / AimsPatient motion during positron emission tomography (PET) imaging can corrupt the image by causing blurring and quantitation error due to misalignment with the attenuation correction image. Data-driven techniques for tracking motion in PET imaging allow for retrospective motion correction, where motion may not have been prospectively anticipated.MethodsA two minute PET acquisition of a Hoffman phantom was acquired on a Bi- ograph mCT Flow, during which the phantom was rocked, simulating periodic motion with varying frequency. Motion was tracked using the sensitivity method, the axial centre-of-mass (COM) method, a novel 3D-COM method, and the principal component analysis (PCA) method. A separate two minute acquisition was acquired with no motion as a gold standard. The tracking signal was discretised into 10 gates using k-means clustering. Motion was modelled and corrected using the reconstruct-transform-add (RTA) technique, leveraging Multimodal Image Registration using Block-matching and Robust Regression (Mirorr) for rigid registration of non- attenuation-corrected 4D PET and Software for Tomographic Image Reconstruction (STIR) for PET reconstructions. Evaluation was performed by segmenting white matter (WM) and grey matter (GM) in the attenuation correction computed tomography (CT). The mean uptake in the region of GM was compared with that in the WM region. Additionally, the difference between the intensity distributions of WM and GM regions was measured with the t-statistic from a Welch's t-test.ResultsDifference in the mean distribution of WM to GM ranked the techniques in order of efficacy: no correction, sensitivity, axial-COM, 3D-COM, PCA, no motion. PCA correction had a great WM/GM separation measured by the t-value than the no motion scan. This was attributed to interpolation blurring during motion correction reducing class variance.ConclusionOf the techniques examined, PCA was found to be most effective for tracking rigid motion. The sensitivity and axial-COM techniques are mostly sensitive to axial motion, and so were ineffective in this phantom experiment. 3D-COM demonstrates improved transaxial motion sensitivity, but not to the level of effectiveness of PCA.
A Comparison of Techniques for PET Data-Driven Tracking of Head Motion
