Investigation of respiratory motion gating with geometric sensitivity in Allegro PET

Respiratory motion artifacts can be a significant factor that limits the PET image quality. To improve image quality, surveillance systems have been developed to track the movements of the subject during scanning. Gating techniques utilizing the tracking information, are able to compensate for subject motion, thereby improving lesion detection. In this paper, we present a gating method that utilizes the geometric sensitivity gating (GSG) of a 3D-PET scanner system operating in list event acquisition mode. The count rate from a given organ, as a result of the geometric sensitivity, will depend on the axial location of the organ. As a result the respiratory phase can be determined from count rate changes which are determined to suitable temporal resolution from the list-mode data stream. GSG method has several advantages over the existing methods; it only uses LOR events and is non-invasive, no additional hardware device systems are required and there is no additional patient preparation required. Using GATE (GEANT4 Application Tomographic Emission) and NCAT (NURBs(Non Uniform Rational B-Splines) Cardiac Torso) software packages with a configuration simulating a Philips Allegro PET system, realistic simulations of respiratory motion demonstrate that GSG can be used for respiratory gating. Clinical data have been acquired and also demonstrate that GSG is able to reduce respiratory motion artifact.