Docent Lecture: Compton scatter correction in SPECT
by
Cathrine Jonsson(Karolinska University Hospital, Dept of Medical Physics)
→
Europe/Stockholm
FB55
FB55
Description
Clinical nuclear medicine imaging refers to techniques capable of visualizing the distribution of administered gamma emitting radiopharmaceuticals within a patient using external detectors. Performing tomography with a gamma camera, i.e. single photon emission tomography (SPECT), has potential to give a 3D representation of the true activity distribution. This opens up for deriving useful quantitative 3D functional indices to support the diagnostic evaluation. However, to quantitate the activity distribution requires corrections for various phenomena such as Compton scattering, attenuation, and in some cases septal penetration. Even with these corrections applied the limited spatial resolution of the device further put strains on how small objects that can be accurately quantified.
This lecture is devoted to scatter; how it hampers the images and methods proposed to correct for the phenomenon. In nuclear medicine imaging scatter generally refers to Compton scattered photons, elastic scattering being less important since the interaction process is much less likely to occur and since the scattering angles are generally much smaller. Detection of Compton scattered photons, which in a clinical SPECT investigation can be 30-40% of the detected photons in the photopeak energy window, result in degradation of the images both qualitatively and quantitatively. During the last three decades numerous correction methods has been proposed. A compilation of some of the presented approaches to correct for Compton scattered photons; from simple and easily implemented compensation methods to more sophisticated and complex correction algorithms implemented in iterative reconstruction algorithms will be presented. Focus will be on the methods strengths and weaknesses, ease in implementation and a discussion whether there is consensus regarding the method of choice in the clinic.