Qualitative and quantitative assessment of the effect of respiratory movement on right lung tumors in PET/CT images

For specific clinical diagnoses, positron emission tomography (PET) can detect more sites of disease than conventional anatomical imaging such as x-ray computed tomography (CT) or magnetic resonance imaging (MRI). Interpretation of PET can be difficult; however, PET images have few anatomical landmarks for determining the location of abnormal findings. Combining PET and CT images acquired sequentially on their separate devices provides a partial solution to this problem. In earlier years PET/CT has an important role in detecting tumors, planning radiation treatment and evaluating response to therapy. Differences in PET and CT imaging time, especially in the lung region, cause artifacts and errors in estimating tumor uptake and volume determination. The purpose of this paper was to investigate qualitative and quantitative errors due to respiratory artifacts on tumors of the lung. For this purpose, the XCAT phantom was used to simulate respiratory motion and also, STIR was used to apply attenuation maps on reconstruction of PET images. The evaluation of results was performed by ROI and SULmax parameters. The images from various methods of attenuation correction, indicated that respiratory motion on regions above the lungs is poorly. The best method is the Initial review of PET images to obtain the size and location of the tumor and then make a decision about the appropriate respiratory phase based on the size and location of the tumor for attenuation correction of PET images.