Abstract
Respiratory motion blurs the standardized uptake value (SUV) and leads to a further signal reduction and changes in the SUV maxima. 4D PET can provide accurate tumor localization as a function of the respiratory phase in PET/CT imaging. We investigated thoracic tumor motion by respiratory 4D CT and assessed its deformation effect on the SUV changes in 4D PET imaging using clinical patient data. Twelve radiation oncology patients with thoracic cancer, including five lung cancer patients and seven esophageal cancer patients, were recruited to the present study. The 4D CT and PET image sets were acquired and reconstructed for 10 respiratory phases across the whole respiratory cycle. The optical flow method was applied to the 4D CT data to calculate the maximum displacements of the tumor motion in respiration. Our results show that increased tumor motion has a significant degree of association with the SUVmax loss for lung cancer. The results also show that the SUVmax loss has a higher correlation with tumors located at lower lobe of lung or at lower regions of esophagus.
Highlights
PET/CT, which provides both functional and anatomical images simultaneously, has demonstrated to be advantageous for the diagnosis and treatment of cancer patients [1,2,3,4]
We developed a four-dimensional deformable image registration algorithm based on the optical flow method (OFM), which links all expiratory phases in the 4D CT
One example selected by maximum percentage difference (PD) is shown in the coronal view of the PET scan
Summary
PET/CT, which provides both functional and anatomical images simultaneously, has demonstrated to be advantageous for the diagnosis and treatment of cancer patients [1,2,3,4]. PET can be used in patient diagnosis for the initial tumor staging and restaging. The long acquisition time of PET imaging compared to CT anatomic imaging may cause problems in data registration for a diagnostic PET/CT scan. Additional challenges due to respiration in the thoracic section complicate the interpretation of PET images and lead to blurring and mis-registration artifacts between PET and CT scans [5]. The blurring of PET from the motion of respiration results in two main artifacts, an increase in the tumor size and reduction of standardized uptake value (SUV)
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