Methods and systems for scatter correction in positron emission tomography

A method of an imaging system, comprising:

• performing, with a first scanner, a first scan of a patient positioned in the imaging system;
• acquiring image data from the first scanner;
• generating a first image from the image data collected during the first scan;
• executing, with a processor, segmentation of the first image, wherein instructions for the processor are stored in a memory;
• generating a second, segmented image from the first image;
• identifying contours of one or more organs in the first image, wherein the organs are outside of a field of view (FOV) of a second scanner;
• acquiring a first emission activity from the FOV of the second scanner;
• executing instructions in the memory that instruct the processor to estimate a second emission activity from outside the FOV of the second scanner based on the second, segmented image;
• estimating a scatter correction based on each of the first emission activity and the second emission activity;
• and
• generating a third image based on the first emission activity and the scatter correction.

A computed tomography/positron emission tomography (CT/PET) system, comprising:

• a CT imaging system configured to acquire a CT image of a patient positioned in the CT/PET system;
• a PET imaging system configured to acquire emission activity within a field-of-view (FOV) of a scanner of the PET imaging system;
• a processor;
• and
• a memory storing executable instructions that when executed cause the processor to:
• segment the CT image and identify contours of one or more organs in the CT image lying outside the FOV;
• estimate an out-of-field (OOF) PET activity based on a radiotracer uptake estimated based on one or more of a size and shape of the identified contours;
• and
• generate a PET image based on the emission activity within the FOV of the scanner and corrected by the OOF PET activity,
• wherein the memory stores additional executable instructions that, when executed, cause the processor to estimate the radiotracer uptake based on an intensity ratio.