Fourier analysis on ungated time-activity curves.

The frequency content of the ungated radionuclide time-activity curves for left and right ventricles was analyzed using a power spectrum estimation technique. This technique was applied to ten patients. It was observed that 75% of the contraction power of any ventricle was contained in the fundamental and at least 98% contained in the fundamental plus the first harmonic. Patients presenting bigeminy and trigeminy had a completely different spectrum distribution which calls for a different interpretation. Low frequency spectrum lines have been observed at breathing frequency. Up to 62% of the total power may be contained in those spectrum lines.