If the imaging sessions are funded through a research account number then the number of imaging sessions approved will coincide with those funded. If the proposal is not approved, the PI is notified by the Center's Director of the main reasons why the proposal was not approved. The PI is then invited to the next PET Center's research meeting to address these concerns. Major concerns will require that the application be modified and resubmitted. 3D studies have increased sensitivity allowing reduced patient radiation exposure but are not as quantitative.
Individual investigators choose the mode that is best for their experiment.