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J Nucl Med. 2008; 49 (Supplement 1):406P
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Instrumentation & Data Analysis: Instrumentation

Instrumentation Posters

Sensitivity of slit-convergent-slat collimation

Caesar Ordonez1, Mark Holcomb1 and Wei Chang1

1 Diagnostic Radiology, Rush University Medical Center, Chicago, Illinois

1710

Objectives: Chang, et al. have shown recently that proper use of slit-slat collimation with parallel slats has potential for significant improvement in SPECT sensitivity. Further increase may be achieved with axially-convergent slats, which allows for larger detection solid angles. Here we derive a formula for the sensitivity of slit-convergent-slat (SCS) collimation, for use in the evaluation of SCS-collimator designs.

Methods: Accorsi, et al. have derived analytically a formula for the sensitivity of slit-slat collimation with parallel slats. A similar derivation for SCS collimation is more complicated because SCS sensitivity is not invariant under axial translation parallel to the slit. We therefore use an empirical, semi-analytic approach to find such a formula. The collimator is modeled as a multi-parameter system, with an initial set of values for the parameters. Holding all but one parameter fixed, the sensitivity is calculated for a range of values for that parameter. The sensitivity is the relative solid angle on the detector plane from a point source. The functional dependence of the sensitivity on the parameter is then obtained via least-squares fitting. The effects of septal penetration and scatter are ignored.

Results: The derived formula is well-defined in the space that lies between the slit-plate and the focal line of the convergent slats. It features an inverse relationship between focal length and sensitivity. In the limit as the focal length goes to infinity, the formula reduces to that for slit-slat collimation with parallel slats. Lastly, unlike the parallel-slat case, the sensitivity exhibits an additional dependence on the axial position of the source.

Conclusions: The formula is useful in our design and development of an advanced cardiac system, C-SPECT/CT-2, that will utilize SCS collimation for high-performance imaging.

Research Support: NIH





This Article
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Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Google Scholar
Right arrow Articles by Ordonez, C.
Right arrow Articles by Chang, W.
PubMed
Right arrow Articles by Ordonez, C.
Right arrow Articles by Chang, W.