Directional resolution of limited-angle multi-pinhole SPECT cameras

Cuddy-Walsh, Sarah G.; Clackdoyle, Rolf; Wells, R. Glenn

doi:10.1109/nssmic.2014.7430996

Cited by 1 publication

(1 citation statement)

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“…Other variations include averaging | cos ψ i | over all (so a value of 1 at location x indicates data completeness) [24], and taking the maximum value of| sin ψ i | over all θ as an incompleteness metric [31]. The metric we propose here has been previously described in conference proceedings papers [18], [17], [19], [46] but as a heuristic approach to defining resolution in tomographic reconstructions. (Although incompleteness causes a blurring of the test-object features, we prefer to call this "poor tomographic recovery" rather than "poor resolution", because the effect scales with the size of the object which is not the usual meaning of "resolution.")…”

Section: Discussionmentioning

confidence: 99%

Quantification of Tomographic Incompleteness in Cone-Beam Reconstruction

Clackdoyle

Noo

2020

IEEE Trans. Radiat. Plasma Med. Sci.

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For situations of cone-beam scanning where the measurements are incomplete, we propose a method to quantify the severity of the missing information at each voxel. This incompleteness metric is geometric; it uses only the relative locations of all cone-beam vertices with respect to the voxel in question, and does not apply global information such as the object extent or the pattern of incompleteness of other voxels. The values are non-negative, with zero indicating "least incompleteness," i.e. minimal danger of incompleteness artifacts. The incompleteness value can be related to the severity of the potential reconstruction artifact at the voxel location, independent of reconstruction algorithm. We performed a computer simulation of x-ray sources along a circular trajectory, and used small multi-disk test-objects to examine the local effects of data incompleteness. The observed behavior of the reconstructed test-objects quantitatively matched the precalculated incompleteness values. A second simulation of a hypothetical SPECT breast imaging system used only 12 pinholes. Reconstructions were performed using analytic and iterative methods, and five reconstructed test-objects matched the behavior predicted by the incompleteness model. The model is based on known sufficiency conditions for data incompleteness, and provides strong predictive guidance for what can go wrong with incomplete cone-beam data.

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