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Correction of Head Movement on PET Studies: Comparison of Methods

¹ CSC–MRC Cyclotron Unit, Imperial College, Hammersmith Hospital, London, United Kingdom; and ² Hammersmith Imanet, Hammersmith Hospital, London, United Kingdom

View larger version (54K): [in this window] [in a new window]   FIGURE 1.  Different stages involved in realigning emission data with Polaris-based methods. MTfbf is a 1-stage process, where reconstructed frames (F1 and F2) are moved to position of the transmission scan (TR), using the average frame position derived from Polaris data. MT is a 1-stage process in which lines of response (LORs) are moved to the transmission scan position based on Polaris data. LMCfbf is a 2-stage process: First, LORs within a frame are realigned to average position in the frame using Polaris data; then reconstructed frames are moved to transmission scan position using the average frame position derived from Polaris data. For all methods, only 1 Polaris coordinate is shown for simplicity. Full details of the different methods are given in the text.

View larger version (34K): [in this window] [in a new window]   FIGURE 2.  (A) Plots of Polaris translation files (X, left–right; Y, anterior/posterior; Z, dorsal/ventral): x-axis time = min; y-axis from an arbitrary starting point = mm. a and b indicate large movements. (B) Time–activity curve and PET summated images of (from top to bottom): raw PET data, FBF realignment, MTfbf realignment, MT realignment, and LMCfbf realignment. CB = cerebellum; x-axis time = min; y-axis activity = kBq/mL.

View larger version (15K): [in this window] [in a new window]   FIGURE 3.  Time–activity curves (left) and RMSEs of motion (right) during scanning for each volunteer. (Left) , DS; , VS; , cerebellum; y-axis = kBq/mL; x-axis = min. (Right) y-axis = mm; x-axis = min.

View larger version (16K): [in this window] [in a new window]   FIGURE 4.  Noise levels (coefficient of variance, COV) in different regions after 5 different analyses: raw data, FBF realignment, and 3 Polaris methods (MTfbf, MT, LMCfbf). ANOVA showed significant effects of region, sample time, and method of analysis, with no interactions (error bars indicate SD; brackets indicate P < 0.05).

View larger version (17K): [in this window] [in a new window]   FIGURE 5.  Mean BPs for VS and DS ROIs (brackets indicate paired t test, P < 0.05).

View larger version (58K): [in this window] [in a new window]   FIGURE 6.  SPM comparisons of BP between first (A) and second (B) sampling periods. All voxels were significant at P < 0.01, uncorrected. Data are sagittal (top rows) and axial (bottom rows) glass brain views. Arrowheads indicate peak voxels in significant clusters.

View larger version (7K): [in this window] [in a new window]   FIGURE 7.  Measured BP in VS and DS ROI as ROI is moved a voxel at a time in the z-axis. Large changes in BP result from small changes in ROI position, demonstrating the susceptibility of measurements to movement.