Comparison of 2-dimensional and 3-dimensional cardiac 82Rb PET studies

Most new PET scanners have the capability to collect data in 3-dimensional (3D) (septa removed) mode. This allows many more detected events at the cost of increased random events and scatter. In the case of 82Rb imaging, the injected dose might have to be limited to avoid saturating the scanner. We present a comparison of 2-dimensional (2D) and 3D data collection for 82Rb cardiac studies using the ECAT EXACT scanner.

Resting 82Rb cardiac studies were collected in 2D and 3D modes for 33 consecutive patients. Four experienced physicians rated the images to determine if the different acquisition methods would lead to different patient care. A separate quantitative analysis was performed on data from multiple scans of a thoracic phantom filled to simulate cardiac and background radioactivity corresponding to 82Rb injections between 37 and 1740 MBQ:

The 2D and 3D studies were significantly different, with the image quality being poorer in the 3D studies. The scanner collected data at near its maximal counting rate for either 1480-MBq 2D or 37-MBq 3D acquisitions. Because the data collection was counting rate limited in either mode, and there are more random and scatter events in 3D mode, the 2D acquisitions resulted in more detected true events and a better signal-to-noise ratio.

Cardiac 82Rb studies should be performed in 2D mode when using the ECAT EXACT scanner.