Abstract
Positron Emission Tomography (PET) is a non-invasive radiographic technique in the nuclear medicine, which can measure the organ function, and it has also been widely used for the detection of cancer cell. 3D acquisition mode removes the intra-plane septa. It increases the sensitivity of PET, however the scatter photons also increase hugely, that will blur the image contrast and decrease the quantification accuracy. There are many researches about scatter correction, but none of them is suitable for the complex clinic use. In this thesis we bring up a whole new scatter correction method. Beam stopper is made of high atomic number material and it will attenuate the primary beam while has almost no influence on scattered photons. By using a beam stopper device, we can compute the quantity of scatter photons from the blocked line-of-responses (LOR). With these scatter sample points, we can interpolate the total scatter distribution in a sinogram by the cubic-spline interpolation method. The performance was evaluated by experiment on a uniform water phantom and Monte Carlo simulation on EEC abdomen phantom and Zubal chest phantom. The results indicate the beam stopper method can improve the image contrast and the quantification accuracy obviously while no extra noise is induced even when the object is large or non-uniform. Besides, beam stopper method can deal with many kinds of scatter photons, such as single Compton scatter photons, multiple scatter photons and those originating from scanner out of field of view (OFOV). In sum, beam stopper method is a convenience, quick and effective scatter correction method for 3D PET.