A2 Applied Science - Working Waves - Medical Physics

Medical Physics 

Radio waves (low energy)
- Mobile phones increase head temp by 0.2 degrees.

Infrared
- Pulse oximetry (can go through skin). 
- Can find blood oxygenation and heart rate. 
- Near infrared spectroscopy.
- Thermography.  

Visible light
- Endoscope 
- 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)
- X-radiography. 
- CAT scan. 
- Radio therapy.  

X-Ray Image Sharpness 

There are 2 main factors: 

1. Distance from patient 

2. Smaller scattering of rays by bone. 

X-Ray Imaging 

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.

Half Life

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…