Background: Positron Emission Tomography (PET) and Computed Tomography (CT) are devices used for diagnosis purposes. One of their helpful uses is in oncology. This study compares the effective dose of PET and CT scans for the brain and thyroid. Materials and Methods: One hundred individuals participated in this study: 50 patients with brain tumors and 50 with thyroid tumors. The tumors of each patient type are separated into two equal groups. Each group had twenty-five patients. The first group was evaluated using a PET scan, whereas the second group was inspected with a CT scan. The patients were previously diagnosed by an oncologist and then sent for PET/CT and CT scans. Before administering the radiopharmaceutical for PET, the blood glucose content is measured in all PET and CT patients who have been fasting for at least six hours. Results: The CT scan shows that the brain shows higher current (mAs) than the thyroid. The effective dose of x-ray reached the brain was the highest, followed by the thyroid. The scanning time (minutes) was significantly the highest in the thyroid, followed by the brain. There was no significant difference among the organs in effective dose or current (mAs). For PET scan, the effective dose (mSv), scan time (minute), radiation activity (mCi), and SUV (MBq/ml) shows a highly significant difference between the two studied organs (brain and thyroid). The effective dose shows to be the highest in the brain, followed by the thyroid. The brain, followed by the thyroid, was taken for the minimum examination time. The activity of the x-ray radiation in mCi was found in the thyroid and brain. The brain's standard uptake value (SUV) was higher than the thyroid's. The effective dose for the CT scan was significantly higher than the PET scan for the brain and thyroid. Conclusion: The effective dose obtained from the CT scan is higher than the PET scan for the brain and thyroid.

Received: date: 15\8\2022 Accepted: date: 05\9\2022