Reduction of respiratory motion artifacts in PET imaging of lung cancer by respiratory correlated dynamic PET: methodology and comparison with respiratory gated PET

Abstract

This study proposes a new method to reduce respiratory motion artifacts in PET images of lung cancer. The method is referred to as respiratory-correlated dynamic PET (RCDPET). RCDPET enables the acquisition of 4-dimensional PET data without the need for a respiratory tracking device. In this article, we compare this method with respiratory-gated PET (RGPET). Both methods provide the ability to correct for motion artifacts and more accurately quantitate radiotracer uptake within lung lesions. Both methods were evaluated in phantom studies and 1 patient.

Methods: With RCDPET, data are acquired in consecutive 1-s time frames. A point source attached to a rigid foam block is set on the patient's abdomen and is extended into the camera field of view at the level of the lesion by means of a low-density rod. The position of this source is used to track respiratory motion through the consecutive dynamic frames. Image frames corresponding to a user-selected lesion position within the breathing cycle, in correlation with the point source position, are then identified after scanning. The sinograms of the selected image frames are summed and then reconstructed using iterative reconstruction with segmented attenuation correction.

Results: The results from phantom studies with both RGPET and RCDPET were within 10% agreement, for both activity quantitation and image noise levels. In a clinical application, the quantitation of the SUV(max) and the lesion's size showed a 6% and 2% difference, respectively, between RCDPET and RGPET measurements.

Conclusion: RCDPET can be considered as a comparable, or alternative, method to RGPET in reducing the smearing effects due to respiration and improving quantitation of PET in the thorax. One advantage of RCDPET over RGPET is the ability to retrospectively reconstruct the PET data at any phase or amplitude in the breathing cycle.