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To gate or not to gate: Improved combined respiratory gated images through bootstrapped voxel based noise evaluation

¹ Pharmacology, UCLA, Los Angeles, California

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Objectives: Respiratory motion accounts for a large source of image degradation in PET imaging. Gating PET data for respiratory motion can improve image resolution, but increases statistical noise. Several methods have been employed to combine the data from separate respiratory bins, most utilizing linear or non-linear registration algorithms. We are proposing an alternate method for combining gated data, to create a final superior image, based on a voxel-by-voxel signal evaluation.

Methods: Some voxels benefit largely from the gating of the PET data (achieving improved resolution) while gating comes as a detriment to the signal of other voxels (i.e. the noise in the gated data outweighs the intended advantage). Our algorithm begins with a gated data set, and utilizing bootstrapped data sets and frequency analysis, determines the relative contribution of respiratory signal to noise for each voxel, and creates a final voxel value formed as a weighted combination of the gated and ungated voxel value. We tested our methods on both phantom and human gated PET data.

Results: Combined-gated images demonstrated overall improved resolution relative to ungated images, while maintaining improved noise characteristics relative to gated images. For example, in a human PET study a lung lesion was examined. The contrast-to-noise of the ungated, gated, and combined gated data in relative units was 1.00,0.55, and 0.75 respectively. The FWHM(mm) of the lesion in the superior-inferior dimension was 7.3, 5.3, and 5.5 respectively.

Conclusions: We have described a method to combine gated PET data to create superior PET images. It is straight forward to understand and implement, and protects against image degradation resulting from the implementation of respiratory gating. Similar methods could be extended to SPECT and low dose 4D CT.

This Article Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Kesner, A. Articles by Silverman, D. PubMed Articles by Kesner, A. Articles by Silverman, D.