Patient motion on the GE Discovery CZT camera: Investigating the necessity of motion correction

Objectives Patient motion of >=13mm (2 pixels) has been shown to cause artifacts that may be misinterpreted as ischemia or scarring due to coronary artery disease. New dedicated cardiac cameras allow faster acquisition times, potentially decreasing patient motion. However, the new cameras simultaneously acquire all projection views and thus cannot provide the rotating cine view typically used with traditional SPECT cameras to detect and correct for motion. Knowledge of patient motion on new cameras is needed to guide development of acquisition protocols and quality assurance procedures. This investigation was undertaken to determine when patient motion initially occurs during acquisition on a dedicated cardiac SPECT camera and if the time of motion correlates with patient age.

Methods 100 cardiac stress acquisitions acquired in list mode for 8min on the GE Discovery NM 530c CZT camera were retrospectively studied. Patients were injected with 900MBq of 99mTc-tetrofosmin as part of standard clinical SPECT imaging and consented to further images on the CZT camera. Patients were consecutively selected to provide an approximately equal number of cases for age categories <50, 50-60, 60-70 and >70. Patient motion was quantified by displacement of the epicardium reconstructed in transverse and sagittal slices at each 1min interval over the 8min study. Significant motion was considered to be anything >=12mm (3 pixels).

Results Aggregate analysis of the 100 studies showed 10% had significant motion after 4 minutes of acquisition. Motion significantly increased (p<0.01) between 6 and 7 minutes of acquisition. No significant differences were found between the 4 age categories.

Conclusions These results suggest that image acquisition times of <=6min will avoid a significant increase in patient motion. However, even with shorter imaging times, a subset of patients (10%), not identifiable by age, still exhibit motion. This implies that, even with faster systems, identification of patient motion and application of motion correction may be necessary