To permit assessment by positron tomography of left ventricular mechanical function, methods were developed to measure ejection fraction and regional wall motion and produce realistic images of the beating heart from ECG-gated PET data.
Methods: Following red cell labeling with 15O-carbon monoxide, seven-slice PET data were collected in list mode and reformatted into 16 time frames. Volume-rendered cine images were created by the depth-weighted maximum-activity method. To determine the left ventricular ejection fraction, background was subtracted in voxels outside the heart and the cubic datasets were rotated to the angle with the best septal separation. Depth weighting was applied to stimulate a 99mTc study, and the beating images were rendered by summing counts along parallel projection rays. These techniques were validated in 16 patients by comparison with planar studies performed with 99mTc-red cells.
Results: Visual grading of regional wall motion yielded exact agreement between the PET and 99mTc methods in 62% of walls with agreement with one grade in 94%. Assessment of quantitative regional wall motion agreed closely with an independent threshold edge detection method.
Conclusion: PET techniques have been developed to measure left-ventricular ejection fraction and regional wall motion and to produce realistic beating images of the cardiac blood pool. This information can be obtained at the same time as measurements of perfusion and metabolism and in the same spatial orientation, thereby permitting quantitative assessment by positron tomography of global and regional mechanical function in relation to flow and metabolism.