From the FDA Drug Label
- 6 Radiation Dosimetry Estimated radiation absorbed doses per injected activity for organs and tissues of adult patients following an intravenous administration of copper Cu 64 dotatate injection are shown in Table 1. Table 1. Estimated radiation absorbed dose per injected activity in selected organs with copper Cu 64 dotatate injection
- Mean of 5 patients. Target OrganMean *absorbed dose (mGy/MBq) Adrenals 0. 137 Brain 0.013 Breasts 0.013 Gallbladder wall 0.040 Lower large intestine wall 0.043 Small intestine 0.066 Stomach wall 0.019 Upper large intestine wall 0.022 Heart wall 0.019 Kidneys 0.139 Liver 0.161 Lungs 0.017 Muscle 0.019 Ovaries 0.019 Pancreas 0.093 Red marrow 0.027 Osteogenic cells 0.034 Skin 0.012 Spleen 0.115 Testes 0.014 Thymus 0.015 Thyroid 0.014 Urinary bladder wall 0.037 Uterus 0.
The radiation dose in a PET CT scan with IV contrast using 5.28 mCi Ga68-Dotatate cannot be directly calculated from the provided information, as the table provides estimated radiation absorbed doses per injected activity in mGy/MBq, and the administered dose is given in mCi. However, we can convert the administered dose from mCi to MBq (1 mCi = 37 MBq) and then calculate the estimated radiation absorbed dose for each organ.
- 5.28 mCi is equivalent to 195.36 MBq (5.28 mCi * 37 MBq/mCi).
- To calculate the estimated radiation absorbed dose for each organ, multiply the absorbed dose per injected activity (in mGy/MBq) by the administered activity (in MBq). For example, the estimated radiation absorbed dose for the adrenals would be 195.36 MBq * 0.137 mGy/MBq = 26.76 mGy. However, the total radiation dose from the PET CT scan also includes the dose from the CT scan, which is not provided in the drug label. Therefore, the total radiation dose from the PET CT scan with IV contrast using 5.28 mCi Ga68-Dotatate cannot be determined from the provided information 1.
From the Research
The radiation dose from this PET CT DOTATATE scan is estimated to be around 10 mSv, with the major part coming from internal irradiation due to the radiopharmaceutical Ga68-Dotatate and a minor part from the CT scan. The patient received 5.28 millicuries (mCi) of Ga68-Dotatate administered intravenously, which is a relatively low dose of radiation 2. Additionally, the patient received radiation exposure from the CT portion of the scan, though the exact CT dose is not specified in the report. The scan also involved IV contrast administration, which does not contribute significantly to the radiation dose. PET/CT scans combine nuclear medicine (the radioactive tracer) with computed tomography to provide both functional and anatomical information. The Ga68-Dotatate specifically binds to somatostatin receptors, making it useful for detecting neuroendocrine tumors. According to a recent study, the effective dose of a PET/CT scan with 18F-FDG is approximately 21.64 ± 5.20 mSv, with the CT component contributing around 42% of the overall effective radiation dose 3. However, the radiation dose from Ga68-Dotatate is expected to be lower than that of 18F-FDG. The radiation from this procedure is considered medically necessary for diagnostic purposes, and the benefits of accurate diagnosis typically outweigh the radiation risks for patients with suspected or known neuroendocrine tumors 4, 5.
Some key points to consider:
- The radiation dose from the Ga68-Dotatate is relatively low, with an estimated effective dose of around 6-7 mSv 6.
- The CT component of the scan contributes a minor part to the overall radiation dose, with an estimated effective dose of around 2-4 mSv 6.
- The use of IV contrast does not significantly contribute to the radiation dose.
- The benefits of accurate diagnosis with PET/CT scans outweigh the radiation risks for patients with suspected or known neuroendocrine tumors 4, 5.
- Recent studies have shown that the radiation dose to nuclear medicine staff, porters, nurses, and companions is below the recommended dose limit by the ICRP 2.