AQA A2 Physics - Inside the Body Revision Notes

Inside the Body

XRays:
Lower energy x-rays are absorbed readily by the body, which makes them harmful as
they could ionise atoms in the body. A filter is used to remove these. X-Rays go
through the body and fall on a photographic plate. This forms an image.
Intensity passing through…

X-ray Production
X-rays are produced when high velocity electrons are decelerated (slowed or
stopped) or by a nucleus of an atom especially by high atomic number material, such
as the anode target in an X-ray tube. An electrically heated filament (cathode) within
the X-ray tube generates electrons that are accelerated…

Ultrasound:

Ultrasound consists of high frequency longitudinal waves above the range of human
hearing. Medical Frequencies are around 1 ­ 5MHz, and are used for diagnosis,
cleaning surgical instruments and cleaning teeth. Scanning equipment is very
portable, making it very useful for vets etc.

Production
The production process uses a…

Producing the image
An image is produced by waves reflected from parts of the body that are made of
different tissues. The image is built up by sending out pulses of ultrasound and
changing the beam direction so that it scans the body. Some energy is reflected
from any interface…

Magnetic Resonance Imaging (MRI):

Why is MRI Used
MRI produces a detailed image of the inside of the body. Images are much clearer
due to the image depending on the density of hydrogen nuclei in different parts of
the body, not on absorption or reflective properties of radiation or sound.…

Producing the field
The magnetic flux density inside the coil used in the MRI machine is given by


0NI
B= 2r


o r = Radius
o N = Number of turns
o I = Current
o 0 = Permeability of free space


Resistive coils produce the require fields would generate…

Endoscopy:
Advantages and Uses
Endoscopy can be used for direct observations inside the body using light
Flexible versions used to examine the gastrointestinal tract and the colon
Rigid versions are used in arthroscopy for examining and carrying out
operations on damage knee cartilage

The operation of an endoscope depends on…

Charge Coupled Devices (CCD's):

Advantages
Much more sensitive to light
Image can built up over a long time - can be hours or even days
Image consists of electrical signals so it can be enhanced electronically
Can be used to produce moving images without the need for chemical
processing
Now…