Advantages of list-mode acquisition of dynamic cardiac data [ECG-gated nuclear medicine imaging]

Conventional frame-mode acquisition of multigated blood-pool (MUGA) studies is an imprecise means to study cardiac dynamics in part because the energy and ECG waveform information is not retained Early methods for list-mode acquisition were also somewhat limited in that only the (x,y) coordinate, a timing pulse and an R-wave detect pulse were stored. The authors have extended list-mode capability to include full storage of the ECG waveform and the energy value associated with each spatial coordinate. The spatial coordinates (x and y), energy value (E), and an encoded physiologic/timing signal (p/t) are stored on an event-by-event basis as 8-bit values. These four bytes are streamed onto a hard disk storage device allowing even stress gated blood pool studies to be recorded. List-mode acquisition gives greater flexibility than frame-mode. Among the demonstrable advantages this flexibility provides are the ability to: (1) Measure and correct respirational displacement of the ventricle to minimize motion blurring; (2) Form gated sequences representing only a specific aberrancy for detection of ectopic ventricular foci; and (3) Use the stored multispectral energy information to perform scatter correction on the dynamic images. To conclusively demonstrate the improved resolution of the list-mode methodology, a dynamic phantom was used to simulate blurring due to respiration. The advantages of list-mode warrant its further use, and it may be especially valuable for wall thickness measurements.