Extended MRI-based PET motion correction for cardiac PET/MRI

Abstract

Purpose: A 2D image navigator (iNAV) based 3D whole-heart sequence has been used to perform MRI and PET non-rigid respiratory motion correction for hybrid PET/MRI. However, only the PET data acquired during the acquisition of the 3D whole-heart MRI is corrected for respiratory motion. This study introduces and evaluates an MRI-based respiratory motion correction method of the complete PET data.

Methods: Twelve oncology patients scheduled for an additional cardiac ¹⁸F-Fluorodeoxyglucose (¹⁸F-FDG) PET/MRI and 15 patients with coronary artery disease (CAD) scheduled for cardiac ¹⁸F-Choline (¹⁸F-FCH) PET/MRI were included. A 2D iNAV recorded the respiratory motion of the myocardium during the 3D whole-heart coronary MR angiography (CMRA) acquisition (~ 10 min). A respiratory belt was used to record the respiratory motion throughout the entire PET/MRI examination (~ 30-90 min). The simultaneously acquired iNAV and respiratory belt signal were used to divide the acquired PET data into 4 bins. The binning was then extended for the complete respiratory belt signal. Data acquired at each bin was reconstructed and combined using iNAV-based motion fields to create a respiratory motion-corrected PET image. Motion-corrected (MC) and non-motion-corrected (NMC) datasets were compared. Gating was also performed to correct cardiac motion. The SUV_max and TBR_max values were calculated for the myocardial wall or a vulnerable coronary plaque for the ¹⁸F-FDG and ¹⁸F-FCH datasets, respectively.

Results: A pair-wise comparison showed that the SUV_max and TBR_max values of the motion corrected (MC) datasets were significantly higher than those for the non-motion-corrected (NMC) datasets (8.2 ± 1.0 vs 7.5 ± 1.0, p < 0.01 and 1.9 ± 0.2 vs 1.2 ± 0.2, p < 0.01, respectively). In addition, the SUV_max and TBR_max of the motion corrected and gated (MC_G) reconstructions were also higher than that of the non-motion-corrected but gated (NMC_G) datasets, although for the TBR_max this difference was not statistically significant (9.6 ± 1.3 vs 9.1 ± 1.2, p = 0.02 and 2.6 ± 0.3 vs 2.4 ± 0.3, p = 0.16, respectively). The respiratory motion-correction did not lead to a change in the signal to noise ratio.

Conclusion: The proposed respiratory motion correction method for hybrid PET/MRI improved the image quality of cardiovascular PET scans by increased SUV_max and TBR_max values while maintaining the signal-to-noise ratio. Trial registration METC162043 registered 01/03/2017.

Keywords: 2-Dimensional image navigator; Binning; Motion correction; PET/MRI; Respiratory belt; Signal-to-noise ratio.