PET scan uses –
**Core Concept**
The underlying principle being tested is the understanding of medical imaging techniques, specifically **Positron Emission Tomography (PET)**. PET scans utilize **radiopharmaceuticals** to visualize metabolic processes in the body. This technology is based on the detection of **positron** emissions.
**Why the Correct Answer is Right**
Although the correct answer options are not provided, typically, PET scans use **fluorodeoxyglucose (FDG)**, a **glucose analog** that is taken up by cells with high metabolic rates, such as cancer cells. The **fluorine-18** isotope in FDG emits **positrons**, which are detected by the PET scanner. This allows for the visualization of metabolic activity within the body.
**Why Each Wrong Option is Incorrect**
**Option A:** Without the specific option provided, a common incorrect option might involve the use of **iodine-123**, which is more commonly used in other types of nuclear medicine scans, not PET scans.
**Option B:** Another incorrect option could be **technetium-99m**, which, while used in nuclear medicine, is not the primary radiopharmaceutical for PET scans.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that PET scans are highly sensitive for detecting **cancer metastases** and monitoring **tumor response** to treatment due to the high metabolic activity of cancer cells.
**Correct Answer:** D. Fluorodeoxyglucose.