5.11 - Choosing a Medical Imaging Method

Infrared imaging of injuries and infections

• Infrared imaging finds injuries and infections by detecting temperature differences.
• Injured or infected areas are usually hotter than surrounding tissue, so they emit more infrared radiation.
• An infrared camera detects these differences in emitted infrared and turns them into an image, with the warmer areas standing out.

Uses and limitations

• Useful when many temperatures need to be taken quickly - e.g. using infrared cameras at airports to screen people for fevers.
• Completely safe.
• Only reveals surface temperature, so it can't show internal structure.

Choosing a medical imaging method

Doctors choose the method that gives a good enough image at the lowest risk to the patient, trading safety against the detail needed.

Strengths and risks of each method

• Ultrasound - Completely safe, but gives a fairly fuzzy image and can only image soft tissue, not bone.
• X-rays - Ionising and can damage cells, but give clear images of bone; CT scans give high-resolution images that ultrasound cannot.
• Gamma rays - Ionising, but can show how organs are functioning from the inside.
• Infrared imaging - Completely safe, but only reveals surface temperature.