x-rays in medicine Flashcards
(13 cards)
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
