Radio waves (low energy)
- Mobile phones increase head temp by 0.2 degrees.
- Pulse oximetry (can go through skin).
- Can find blood oxygenation and heart rate.
- Near infrared spectroscopy.
- Endoscopy with pills.
- Scanning laser with opthalmoscope.
- Photodynamic therapy.
- Treatment of jaundice in babies (blue light therapy/treatment)
X-Rays and Gamma Rays (High energy)
- CAT scan.
- Radio therapy.
X-Ray Image Sharpness
There are 2 main factors:
1. Distance from patient
2. Smaller scattering of rays by bone.
Emulsion is sensitive to x-rays and light.
2 layers increase the chance of the x-rays hitting a sensitive atom (silver). This darkens the film where x-rays get through.
Intensifiers produce a flash of light where hit by x-rays (less exposure)
Soft tissues can sometimes be imaged using contrast enhancers which are opaque to x-rays. For example:
- Barium meal (intestines)
- Aniogram (blood vessels)
Scattering of x-rays by bone can reduce the sharpness of the image. This can be reduced by using a lead grid. The lead grid lets x-rays at 90 degrees to the film through but absorbs scattered x-rays.
Digital x-ray cameras and films are becoming more common. Advantage:
- Don't need to be expensive.
- Can be reused.
Radioactive half life is the time for 50% of the original radioactive atoms to decay. It is also time for the radioactivity level to drop to 50%.
After 2 half lives the radioactivity level is down to 25% and then 12.5% and so on.
Biological half life is the time for biological process to remove 50% of the material from…