What is a PET Scan?, What is Metabolism?, What is Metabolic Activity?

 A PET scan (Positron Emission Tomography scan) is an advanced imaging test that helps doctors observe how tissues and organs are functioning in the body. Unlike CT or MRI, which show only structure, PET shows metabolic activity.

🔍 What is a PET Scan?

A PET scan uses a small amount of radioactive tracer—usually a form of glucose (FDG)—which is injected into a vein. The tracer accumulates in areas with high metabolic activity (such as cancer cells), and a special camera captures this activity.

🧠 Why is a PET Scan Done?

PET scans are commonly used for:

1. Cancer Diagnosis & Staging

   • Detect tumors

   • Check if cancer has spread

   • Monitor treatment response

2. Brain Disorders

   • Alzheimer’s disease

   • Epilepsy

   • Brain tumors

3. Heart Conditions

• Assess blood flow

• Identify damaged heart tissue

WHAT IS PET SCAN?

🛠️ How it Works (Step-by-Step)

1. Tracer Injection (e.g., FDG)

2. Wait Period (about 30–60 mins for tracer to spread)

3. Scan in PET/CT Machine

• Often combined with CT for anatomical details (called PET-CT)

🧪 What is Metabolism?

Metabolism refers to all the chemical reactions that occur in your body to keep it alive and functioning. These processes convert the food you eat into energy your body can use.

🔥 What is Metabolic Activity?

Metabolic activity means how active a cell, tissue, or organ is in terms of energy use. Cells that are growing, dividing, or repairing themselves use more energy—and therefore show higher metabolic activity.

🧠🫀 Examples of High Metabolic Activity:

• Brain (always active, even at rest)

• Heart (beats nonstop)

• Cancer cells (grow and divide rapidly)

• Inflamed/infected areas (immune cells active)

These areas will appear brighter on a PET scan because they absorb more of the glucose-based tracer.

🧊 Low Metabolic Activity:

• Resting muscles

• Fatty tissue

• Scar tissue

• Dead or damaged tissue

These use less energy and absorb less tracer, so they appear darker.