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. 2011 Aug 21:648 Supplement 1:S236-S240.
doi: 10.1016/j.nima.2010.11.092.

Fundamental Limits of Spatial Resolution in PET

William W Moses  1
Affiliations

Fundamental Limits of Spatial Resolution in PET

William W Moses. Nucl Instrum Methods Phys Res A. .

Abstract

The fundamental limits of spatial resolution in positron emission tomography (PET) have been understood for many years. The physical size of the detector element usually plays the dominant role in determining resolution, but the combined contributions from acollinearity, positron range, penetration into the detector ring, and decoding errors in the detector modules often combine to be of similar size. In addition, the sampling geometry and statistical noise further degrade the effective resolution. This paper describes quantitatively describes these effects, discusses potential methods for reducing the magnitude of these effects, and computes the ultimately achievable spatial resolution for clinical and pre-clinical PET cameras.

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Figures

Figure 1
Figure 1
Coincidence response function (coincidence rate versus position) between the two darker detector elements in a PET camera (camera dimensions are not to scale). This function is shown in the middle of the figure, with the y-axis being the position and the x-axis being the coincidence rate.
Figure 2
Figure 2
Radial Elongation. Gamma rays emanating from the source penetrate into the detector ring before they interact and are detected. Those impinging normally to the detector ring (travelling horizontallyin this figure) interact in the same crystal, independent of penetration depth, so the tangential projection of the source remains narrow. Those impinging at an oblique angle (travelling vertically in this figure) can interact several different crystals, depending on penetration depth, so the radial projection of the source becomes wide.
Figure 3
Figure 3
Sampling Error. The lines of response (lines connecting all detector–detector pairs). The dark spots at the perimeter are the locations of the 24 crystals. The sampling depends strongly on the position in the field of view, especially near the center. While the pixel at the exact center is very well sampled (has many LORs going through it), nearby pixels are very poorly sampled (only a few LORs go through them).
Figure 4
Figure 4
Contributions to Spatial Resolution. This figure shows diagramatically the contributions to spatial resolution in PET.
Figure 5
Figure 5
Three PET images taken with the same PET camera and reconstructed with the same spatial resolution. a) an object with activity in a small number of voxels, taken with 100,000 events. b) an object with activity in a large number of voxels, taken with 1,000,000 events. c) the same object as in b), but taken with 55,000,000 events.
See this image and copyright information in PMC

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