Evaluation of missing data compensation methods by comparing to no-gap rotating data for a PET camera

Abstract

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Objectives: In PET cameras gaps between the detectors or defective detectors could create gaps in sinograms. In order to generate artifact-free images, especially with filtered backprojection methods that needed for quantitative reconstruction, the missing data in sinograms are estimated or measured by rotating camera during data acquisition. But rotating camera complicates the point-spread-function correction of the data that needed for improving spatial resolution. We have evaluated three gap filling methods: linear interpolation, constrained Fourier space, and forward project of the images reconstructed from incomplete data iteratively. We have compared reconstructed images from the gap-filled data to the images reconstructed from data without gaps acquired by rotating camera.

Methods: We acquired data for a point source, a 20-cm flood phantom, and the Hoffman brain phantom using the HOTPET camera that has a spatial resolution of about 3 mm. HOTPET consists of 12 independent modules that can be rotated and translated radially to alter the camera opening. Camera has the capability to be rotated during data acquisition and in standard operation it is rotated to fill the gaps in sinograms.

Results: Without gantry rotation or any missing data compensation, artifacts dominated images. Linear interpolation method showed the poorest results. Images reconstructed from gap-filled data by other two methods were artifact free but image quality was slightly degraded.

Conclusions: The forward project of the iterative images to fill the gaps produced the best results. The results also indicated that HOTPET camera may be operated without gantry rotation for the purpose of applying PSF correction.

Research Support: This work was supported in part by NIH Grant RO1 CA76246, NIH Grant RO1 EB00217, NIH Grant RO1 EB001038.