What is the approximate degree of deviation from 180 degrees associated with non-colinearity in PET imaging?

In positron emission tomography (PET) imaging, non-collinearity refers to the phenomenon where the emitted positron and the detected gamma photons do not travel exactly opposite to each other, deviating slightly from the expected 180-degree angle. This non-collinearity is primarily due to the positron's range within the tissue before annihilating with an electron, resulting in a small but measurable deviation.

The approximate degree of deviation associated with this non-collinearity is commonly accepted to be around 0.25 degrees. This value is significant in the context of PET imaging, as it affects the spatial resolution and accuracy of the reconstruction algorithms used to create images from the detected events. Understanding this deviation is critical for interpreting PET scans, as it helps in compensating for imperfections in the imaging process and improving overall image quality.

The other values reflect smaller or larger deviations that do not align with the actual measurement range observed in clinical practice. For instance, a degree of 0.10 would be considered too small to account for the effects of non-collinearity accurately, while 0.50 or 1.0 degrees would be excessive and not representative of the measurable deviation recognized in PET technology.