Overview of Medical Imaging Techniques

Infrared Imaging

• Categorized as a passive imaging technique that detects heat given off by the body.
• Used to identify local variations in skin temperature, which may indicate poor circulation or the existence of tumours.
• Applied in locations like airports for rapid illness screening before symptoms manifest.
• Safety profile: Zero risk to the patient.

X-rays

• Uses ionizing electromagnetic waves that penetrate the body; skeletal structures absorb most radiation while soft tissue absorbs significantly less.
• Images are captured using photographic film or digital Charge Coupled Devices ($CCD$) detectors.
• Computerized Tomography ($CT$) scans utilize this technology to produce high-quality $3D$ images.
• Real-time visualization, such as swallowing, can be enhanced using a "barium meal" containing heavy elements.
• Safety profile: Low risk to the patient but high risk to radiographers (requiring protective clothing); not suitable for pregnant women.

Gamma Rays

• Involves injecting short half-life radionuclides into the body.
• External equipment maps the distribution of emitted gamma rays to construct $3D$ images of internal organs.
• Safety profile: Carries some risk to all individuals involved in the procedure.

Magnetic Resonance Imaging ($MRI$)

• Utilizes radio waves to generate high-quality images of internal structures.
• Safety profile: Low risk to the patient.

Ultrasound

• Uses sound frequencies well above the range of human hearing.
• Operates on the emission and detection of waves that reflect when they encounter changes in organ density.
• Produces low-quality, real-time images; primary application is in obstetrics to monitor unborn babies.
• Characteristics: Quick, inexpensive, and provides very low risk.

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