Amount of I-131 given for carcinoma of thyroid is
**Core Concept**
The treatment of thyroid carcinoma with radioactive iodine (I-131) is based on the principle of targeting cancer cells that take up iodine through the sodium-iodide symporter (NIS). This allows for a high dose of radiation to be delivered directly to the cancer cells while minimizing damage to surrounding healthy tissues.
**Why the Correct Answer is Right**
The amount of I-131 administered depends on various factors, including the type and stage of thyroid carcinoma, the patient's age and overall health, and the presence of residual thyroid tissue. The treatment is typically given in a single dose or divided into multiple fractions. The dose is calculated based on the patient's body weight, and the activity of I-131 is usually expressed in millicuries (mCi). For most cases of thyroid carcinoma, a dose of 100-200 mCi of I-131 is considered standard.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it is too low for most cases of thyroid carcinoma. A dose of 10-20 mCi would be more typical for diagnostic purposes or for patients with very low-risk disease.
* **Option B:** This option is incorrect because it is too high for most patients. While some patients may require higher doses, especially if they have bulky disease or are at high risk for recurrence, doses above 200 mCi are not typically used.
* **Option C:** This option is incorrect because it is not a valid unit of measurement for I-131 activity. The correct unit is millicuries (mCi).
**Clinical Pearl / High-Yield Fact**
When administering I-131 for thyroid carcinoma, it is essential to ensure that the patient is adequately hydrated and has access to a bathroom. This can help minimize the risk of radiation exposure to others and reduce the side effects of treatment.
**Correct Answer: C. 100-200 mCi**