Respiratory gating in PET/CT: A step in the right direction

Excerpt

Respiratory motion is inevitable in cardiac imaging with PET as the rest or stress myocardial perfusion imaging (MPI) takes about 6 minutes with ⁸²Rb and 10 to 15 minutes with ¹³N-ammonia and viability imaging 10 to 30 min with ¹⁸F-FDG.1 Figure 1 illustrates an example of respiratory motion between the end-inspiration and end-expiration phases in an ¹⁸F-FDG scan. All newer PET scanners are with CT and without transmission line sources.2 CT has shortened the time for the transmission scan for attenuation correction of the PET data from minutes to seconds and could also provide the important information of calcium scores and contrast-enhanced coronary artery CT images to help diagnose heart disease. CT, however, introduces a new problem of potential mis-registration of the CT and PET data due to its fast scan speed resulting in each CT image being a snapshot or a single phase of the heart in respiratory motion. A series of continuous respiratory phases of snapshot CT images may not be suitable for attenuation correction of the PET data. It is important to mitigate the impact of respiratory motion to improve cardiac PET image quality.

…