Abstract
Purpose4D-PET/CT imaging is an excellent solution for reducing the breathing-induced effects in both CT and PET images. In 4D-PET/CT, 4D-CT images are selected to match those of 4D-PET phase by phase and the corresponding phases are used for attenuation correction in 4D-PET. However, the high radiation dose that patients acquire while undergoing 4D-CT imaging for diagnostic purposes remains a concern. This study aims to assess low-dose interpolated CT (ICT) for PET attenuation correction (PETICT) in thoracic tumor volume delineation.Methods and MaterialsTwelve thoracic cancer patients (10 esophageal and 2 lung cancer cases) were recruited. All patients underwent 4D-PET/CT scans. The optical flow method based on image intensity gradient was applied to calculate the motion displacement in three dimensions for each voxel on two original extreme CT phases in the respiratory cycle, end-inspiration and end-expiration. The interpolated CTs were generated from two phases of the original 4D-CT using motion displacement.ResultsTumor motion due to respiration was estimated in the anterior-posterior dimension, the lateral dimension and the superior-inferior dimension by the optical flow method. The PETICT and ICT (4D-PET ICT/ICT) matched each other spatially in all the phases. The distortion of tumor shape and size resulting from respiratory motion artifacts were not observed in 4D-PETICT. The tumor volume measured by 4D-PET ICT/ICT correlated to the tumor volume measured by 4D-PET/CT (p = 0.98).Conclusions4D-PETICT consistently represented the interpretation of FDG uptake as effectively as 4D-PET. 4D-PET ICT/ICT is a low-dose alternative to 4D-CT and significantly improves the interpretation of PET and CT images, while solving the respiratory motion problem as effectively as 4D-PET/CT.
Highlights
Positron emission tomography/computed tomography (PET/CT) enables the precise localization and characterization of sites of radiotracer uptake for tumor detection
4D-PET attenuation correction (PETICT) consistently represented the interpretation of FDG uptake as effectively as 4D-PET. 4DPET interpolated CT (ICT)/ICT is a low-dose alternative to 4D-CT and significantly improves the interpretation of PET and CT images, while solving the respiratory motion problem as effectively as 4D-PET/CT
This study aims to assess the interpretation of 4D-PET using ICT for attenuation correction (AC) on 4D-PET/CT in the spatial matching of PET and CT, localization of tumors, quantification of tumor volume and quantitation of standardized uptake value (SUV) for clinical thoracic cancer patients
Summary
Positron emission tomography/computed tomography (PET/CT) enables the precise localization and characterization of sites of radiotracer uptake for tumor detection. The hybrid scanners combine anatomic and functional information to improve cancer diagnosis, tumor staging and restaging, and tumor response under treatment. They aid in target volume delineation in radiotherapy treatment planning, which is required to calculate the optimal radiation dose for the tumor and the surrounding normal tissues [1,2]. Motion artifacts on CT imaging introduce errors in localization and the overestimation of tumor volume due to blurring of the tumor volume, but can cause the underestimation of standardized uptake value (SUV) in PET quantification [5,6,7,8]. PET/CT imaging that uses Real-Time Position Management (RPM, Varian Medical Systems, Palo Alto, CA, USA), a respiratory motion monitoring system, is referred to as 4D (gated) PET/CT imaging and is an excellent solution for reducing breathing-induced effects on both CT and PET images [10,11,12,13]. 4D-CT with gates of equal amplitude, which
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