1.7 Medical Imaging

1.7 Medical Imaging

X-Rays

High-energy electromagnetic radiation passes through soft tissue but is blocked by hard tissue (bone, teeth).

Best for: Bones, teeth, detecting fractures.

Pros: Quick, cheap, widely available.

Cons: Radiation exposure (cancer risk if overused).

Computed Tomography

Multiple X-ray “slices” compiled by computer into detailed cross-sectional images.

Best for: Soft tissues (brain, chest, abdomen), tumors, internal bleeding.

Pros: Very detailed, can measure masses precisely.

Cons: Higher radiation than X-rays → cancer risk (esp. in children, multiple scans).

Magnetic Resonance Imaging

Strong magnets + radio waves → tissues emit signals → computer generates images.

Best for: Soft tissues, especially brain and tumors.

Pros: No radiation, very precise.

Cons: Expensive, time-consuming, noisy, uncomfortable, unsafe for patients with metal implants.

Special: fMRI shows blood flow and brain activity.

Positron Emission Tomography

Radioactive “tracers” injected → emit signals → computer shows physiology in real time.

Best for: Function of organs (not just structure). Used in cancer spread, heart disease, brain disorders.

Pros: Shows activity (metabolism, blood flow), not just structure.

Cons: Radioactive tracers needed, more complex than CT/MRI.

Ultrasonography

High-frequency sound waves bounce back → computer converts echoes into live images.

Best for: Pregnancy (fetal development), heart, blood flow, soft tissue diseases (e.g., gallbladder).

Pros: Safest (no radiation), real-time imaging.

Cons: Image quality depends on operator, can’t see through bone or gas.