**Core Concept**
Gamma cameras are used in Nuclear Medicine to visualize and quantify the distribution of radioactive tracers within the body. This is achieved through the detection of gamma rays emitted by the tracer, allowing for the creation of images that can be used to diagnose and monitor various conditions.

**Why the Correct Answer is Right**
The gamma camera, also known as a scintillation camera, works by detecting the gamma rays emitted by the radioactive tracer. These gamma rays interact with a scintillator material, which converts them into visible light. This light is then detected by a photomultiplier tube and processed to create an image of the tracer distribution. The gamma camera is particularly useful for imaging organs and tissues that have a high metabolic rate, such as the thyroid and liver.

**Why Each Wrong Option is Incorrect**
**Option A:** A gamma camera is not primarily used for ultrasound imaging. Ultrasound machines use high-frequency sound waves to produce images, whereas gamma cameras rely on the detection of gamma rays.
**Option B:** A gamma camera is not used for magnetic resonance imaging (MRI). MRI machines use powerful magnets and radio waves to produce detailed images of the body, whereas gamma cameras rely on the detection of gamma rays.
**Option C:** A gamma camera is not used for computed tomography (CT) scans. CT scanners use X-rays to produce detailed images of the body, whereas gamma cameras rely on the detection of gamma rays.

**Clinical Pearl / High-Yield Fact**
The gamma camera is a crucial tool in Nuclear Medicine, allowing for the visualization and quantification of radioactive tracers in real-time. This can be particularly useful for diagnosing and monitoring conditions such as thyroid disorders, where the gamma camera can be used to image the uptake of radioactive iodine.

**Correct Answer: C. Gamma camera in Nuclear Medicine is used for imaging the distribution of radioactive tracers within the body.**