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[M A Lewis, Ph.D.]

http://www.iop.org/EJ/abstract/0031-9155/44/3/019

Craig S Levin and Edward J Hoffman 1999 Phys. Med. Biol. *44* 781-799


    Calculation of positron range and its effect on the fundamental
    limit of positron emission tomography system spatial resolution


*Abstract.* Developments in positron emission tomography (PET)
technology have resulted in systems with finer detector elements
designed to further improve spatial resolution. However, there is a
limit to what extent reducing detector element size will improve spatial
resolution in PET. The spatial resolution of PET imaging is limited by
several other factors, such as annihilation photon non-collinearity,
positron range, off-axis detector penetration, detector Compton scatter,
undersampling of the signal in the linear or angular directions for the
image reconstruction process, and patient motion. The overall spatial
resolution of the systems is a convolution of these components. Of these
other factors that contribute to resolution broadening, perhaps the most
uncertain, poorly understood, and, for certain isotopes, the most
dominant effect is from positron range. To study this latter effect we
have developed a Monte Carlo simulation code that models positron
trajectories and calculates the distribution of the end point
coordinates in water for the most common PET isotopes used: F, N, C and
O. In this work we present some results from these positron trajectory
studies and calculate what effect positron range has on the overall PET
system spatial resolution, and how this influences the choice of PET
system design parameters such as detector element size and system
diameter. We found that the fundamental PET system spatial resolution
limit set from detector size, photon non-collinearity and positron range
alone varied from nearly 1 mm FWHM (2 mm FWTM) for a 10-20 cm diameter
system typical for animal studies with F to roughly 4 mm FWHM (7 mm
FWTM) for an 80 cm diameter system typical for human imaging using O.






SERGIO.GARZAS wrote:

>Hello I am a student of physics from Spain. I must do a study about the 
>physics in PET. I´m looking for information about "positron range and 
>the processes that involves it", Can anybody help me sending articles 
>or information about it?
>
>Thank you in advance
>
>
>Sergio García Fernández
>
>
>
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