**Question:** All the given statements are true about PET scan except:

A. Positron Emission Tomography (PET) scan is a nuclear medicine technique for assessing the functional status of organs and tissues.
B. PET scan is a diagnostic tool used for identifying cancer.
C. PET scan requires ionizing radiation for its functioning.
D. PET scan is a non-invasive procedure that involves the use of injecting a radiopharmaceutical.

**Correct Answer:** C. PET scan requires ionizing radiation for its functioning.

**Core Concept:** Positron Emission Tomography (PET) scan is a nuclear medicine technique used to assess the functional status of organs and tissues by monitoring the distribution of radiopharmaceuticals within the body.

**Why the Correct Answer is Right:** PET scan is a non-invasive procedure that involves the administration of a radiopharmaceutical, which is a glucose analog labeled with a positron-emitting radioisotope, typically fluorine-18 fluorodeoxyglucose (FDG). When the radiopharmaceutical is taken up by the target tissue, it emits a positron, which interacts with an adjacent electron, creating a pair of annihilation photons that move in opposite directions. These photons are then detected by a scanner, creating a 3D image of the distribution and uptake of the radiopharmaceutical within the body.

**Why Each Wrong Option is Incorrect:**

A. Although PET scan is a nuclear medicine technique, it does not solely rely on ionizing radiation for its functioning. The radiopharmaceutical is the primary component that detects the functional status of organs and tissues.

B. PET scan is a diagnostic tool used for identifying cancer, but it is a broader technique that can assess the functional status of various organs and tissues, not just cancer diagnosis.

D. PET scan is a non-invasive procedure that involves the administration of a radiopharmaceutical, which helps to visualize functional information within the body, not the use of ionizing radiation.

**Clinical Pearl:** PET scan is a valuable diagnostic tool for evaluating various diseases, including cancer, neurodegenerative disorders, cardiovascular diseases, and neurological conditions. It provides valuable functional information about organs and tissues, aiding in diagnosis, staging, and treatment planning. However, ionizing radiation is not the primary focus of PET scan, but rather the administration of radiopharmaceuticals.