P13.5 X-rays in medicine Flashcards
How are X-rays produced?
They are produced in an X-ray tube when fast-moving electrons hit a target
How are radiographs produced?
A lightproof cassette containing a photographic film or a flat-panel detector is place on the other side of the patients
How does an X-ray actually work?
X-ray tube is switched on - X-rays from the tube pass through the part of the patients body
X-rays pass through soft tissue - they are absorbed by bones - teeth and metal objects that are not too thin
The parts of the detector that the X-rays reach become darker than other parts
So the bones appear lighter then the surrounding tissue - which appears dark
How can an organ that consists of soft tissue be seen on a radiograph?
It can be filled by a substance called a contrasts medium that absorbs X-rays easily
This enables the internal surfaces in the organ to be seen on the radiograph
How can other parts of the body not be damaged by X-rays?
Lead plates between the tube and the patient stop X-rays reaching other parts of the body
The X-rays reaching the patient pass through a gap between the plates
Why is lead used to block out X-rays?
Because it is a good absorber of X-rays
What is a flat-panel detector?
A small screen that contains a charge-coupled device (CCD)
The sensors in the CCD convert X-rays into light
The light rays then create electronic signals in the sensors that are sent to a computer - which displays a digital X-ray image
What is the radiation dose?
It is a measure of the damage done to their body by ionising radiation
What does the radiation dose depend on?
The type of radiation used
How long the body is exposed to it
The energy per second absorbed by the body from the radiation
What is the problem with radiation?
High doses of radiation kill living cells
Low doses can cause gene mutation and cancerous growth
What are some examples of background radiation?
From space
Radon gas
What are the differences between X-rays used in therapy and imaging?
X-rays for therapy are shorter in wavelength than X-rays used for imaging
Why are low energy X-rays suitable for imaging and not for therapy?
Low energy X-rays are used for imaging because the bones and teeth absorb the X-rays and pass through the soft tissue
Low-energy X-rays do not carry enough energy to destroy cancerous tumours
