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9 Cards in this Set
- Front
- Back
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Medical applications of Physics |
To understand this topic you need to understand: The use of x rays for diagnostic and treatment The use of ultrasound for diagnostic and treatment The use of lenses for the correction of defects of vision That the range of human hearing is about 20Hz-20000Hz The structure of the eye and how we correct defects in vision |
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X-Rays |
X-Rays are part of the electromagnetic spectrum. They have a high frequency and a very short wave length. The high frequency means they have a high energy and can cause ionisation. |
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Properties of X-Rays |
Affect photographic film- this means it can form a image on a X-ray plate or with a charged couple device (CCD). CCDs allow the image to be formed electronically. Absorbed by dense materials- can take shadow pictures of bones to detect breaks and fractures Transmitted by health tissues- used by computerised tomography (CT) scans to detect problems with tissue, e.g. disease or tumours High ionising power- used for killing cancer cells in radiotherapy |
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Precautions for X-Rays |
All uses of X-rays have the same precautions: Only use if necessary and use as low power as possible Use a focused beam during treatment so as not to exposes areas of the body not being treated or examined Technicians should take the X-rays from behind a screen or wear lead clothing Technicians should wear detection badges, which measure their exposure over time. |
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Ultrasound |
Ultrasound is sound waves greater than 20,000Hz (above the human hearing range). Electronic systems produce electrical oscillations, which are used to generate ultrasound waves. As ultrasonic waves pass for one medium into another they partly reflected at the boundary. The time taken for these reflections is a measure of how far away the boundary is. The reflected waves are usually processed to produce a visual image on the screen. |
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Use of Ultrasound in medicine |
The main use of ultra sound in medicine is in prenatal scans, but is used in other scans like testing for testicular cancer. An ultrasound pulse is sent into the body and this gets reflected back at different changes of density. So this can be used to get a image of the foetus. Ultrasound is used as it is non ionising so is safer. Ultrasound can also be used to breakup kidney stones which can then be passed out of the body in urine. This saves having to operate on the patients kidneys. |
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Ultrasound (detecting flaws and cracks) |
Some of the ultrasound waves are reflected back by the flaw or the crack within the structure. The time taken for the reflected wave to return is used to calculate the location of the crack. |
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Ultrasound (cleaning delicate objects) |
The vibrations caused by ultrasonic waves can be used in a liquid to dislodge dirt particles from the surface of an object. Using this method means is no danger of breakage and no need to take a object apart. |
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Comparison of scanning methods |
CT scans - image quality - very good Radiation exposure - longest exposure to ionising radiation
X-Rays - image quality- good Radiation exposure - short exposure
Ultrasound - image quality - average to excellent depending on equipment Radiation exposure - none
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