Thyroid Cancer and (FDG)PET/CT Scan

Summary

Participation Requirements

Description

Design and Methodology Study design:- It's a prospective study for the group of patients who will do F-18FDG PET/CT scan after negative whole body scan with elevated serum thyroglobulin Antibody or Thyroglobulin levels. Pre-study investigations:- All patients at this study should have histopathologi...

Design and Methodology Study design:- It's a prospective study for the group of patients who will do F-18FDG PET/CT scan after negative whole body scan with elevated serum thyroglobulin Antibody or Thyroglobulin levels. Pre-study investigations:- All patients at this study should have histopathological evidence of DTC serum TSH level serum TG & antiTG antibodies levels radioactiveiodine whole body scan (I-WBS) Neck ultrasound Blood glucose level Radioisotopes: Iodine-131 (I-131) is an important radioisotope of iodine as a major product of Uranium fission. It is a ?-emitting radionuclide with a maximum energy of 606 keV and an average energy of 191 keV. Average range of ?-particles in tissue is 0.8 mm and has a principal ?-ray of 364 keV. It has a radioactive decay half-life of about eight days. Only well-differentiated thyroid cancer cells concentrate radioiodine to a significant degree. F-18-fluoro-2-deoxyglucose (FDG) is a positron emitting radiotracer that is transported intracellularly and phosphorylated by hexokinase to FDG-6-PO4 through the same cellular membrane transport pathways as glucose. Unlike glucose, however, FDG-6-PO4 is subsequently trapped intracellularly due to lack of further metabolism from insufficient amounts of glucose phosphatase. After intravenous administration, this substrate accumulates in tumors during the uptake phase, and whole body imaging can then be performed to identify regions of high glycolytic activity. and can be used to characterize and localize many types of tumors as well as determining stage and sites of recurrent disease. Patient preparation Patients fasted for at least 6 hours before F-18FDG PET/CT imaging with the exception of water intake. The blood glucose level was measured before tracer injection. The blood glucose levels of all patients should be less than 150 mg/dL . An intravenous catheter was placed for radiopharmaceutical administration, After tracer injection, the patients rested on a comfortable chair during the 18F-FDG uptake period F-18FDG PET/CT Imaging PET/CT was initiated (45-60) min after injection of the F-18-FDG, Each patient received 400-610 MBq (11-16.5 mCi) of 18F-FDG intravenously. CT was performed before acquisition of the PET data in a single step with the patients supine. First, a scout scan was obtained to determine the axial range of the study. The scanning parameters for whole-body CT craniocaudal scanning are 130 kV, 80-120 mAs, 5-mm collimation, and a pitch of 1.6. During the scan, patients have to maintain shallow respiration. The subsequent 3-dimensional PET data acquisition included 4-6 bed positions, (4 min per bed position) over the same axial extent. The PET acquisition included a dead time correction and online delayed coincidence subtraction to correct for random coincidences. Rescaled CT images were used to produce attenuation correction values for the PET emission reconstruction.

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