MEMS gating: A new dual gating technique for eliminating motion-related inaccuracies in PET imaging

Respiratory and cardiac motions may cause quantitative inaccuracies and hinder visual interpretation in positron emission tomography (PET) imaging. In practice, concurrent respiratory and cardiac gating is required to reliably image and identify small structures such as vulnerable coronary plaques. This study proposes a new microelectromechanical sensor (MEMS)-based gating method for eliminating motion-related artefacts. We used joint miniaturized tri-axial accelerometer and gyroscope sensors attached to the patients' chests to extract seismocardiographic (SCG) and gyrocardiographic (GCG) signals. Dual gating in cardiac patients was performed using 18F-fluorodeoxyglucose (FDG) as a tracer. The MEMS dual gating was configured and studied parallel to clinically approved methods for cardiac and respiratory gating: electrocardiography (ECG) and Real-time Position Management (RPM) systems, in PET acquisition of two atherosclerosis patients. Moreover, the radiopacity of the sensor readout-electronics was tested using a Ge-68 phantom before the clinical examinations. Accordingly, no metal artifacts were detected either in CT or PET images due to the motion sensor board, as investigated by two independent operators. Therefore, the MEMS gating board does not contain materials that could affect the visual or quantitative accuracy of PET images or CT-based attenuation correction (CTAC). Dual gated PET images were successfully reconstructed by using only cardiac and respiratory signals derived by MEMS sensors. The MEMS-gated images from the patient study were quantitatively compared to non-gated and gated images that were obtained with the reference methods. In conclusion, these results from the small patient group first imply that implementation of the MEMS gating approach is applicable in dual gated PET imaging and secondly show both qualitative and quantitative improvements in the obtained images. Thus, the first clinical experiences using MEMS cardiac-respiratory dual gating were promising and warrant for further investigations in PET imaging studies.