x-rays and ultrasound

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What are x rays ?	X-rays are part of the electromagnetic spectrum. They have a very short wavelength and cause ionisation
State 6 properties of X - rays	Properties of X-rays include: ■ they affect a photographic film in the same way as light ■They have a very short wavelength ■cause ionisation ■ they are absorbed by metal and bone ■ they are transmitted by soft tissue ■ their wavelength is of the same order of magnitude as the diameter of an atom.
State the uses of X-rays	• Detecting bone fractures • Detecting dental problems • Killing cancer cells • CT scanning
what happens to x rays inside the body ?	• X-rays are absorbed by bone • X-rays travel through / are transmitted by tissue / skin
State the risks of using x- rays	X-rays pose a risk / danger / hazard X-rays cause ionisation / damage to cells turn cells cancerous or kill cells
What precautions can be taken when X-ray machines and CT scanners are in use.	1. Patients are limited to the number of X-rays they are allowed to have 2. X-ray machines also produce relatively low energy X-rays 3. radiographers routinely leave the room, or stand behind a screen containing lead, or wear lead aprons
What is a CCD ?	A CCD is a charge-coupled device. Modern X-ray machines use CCDs instead of photographic film. The images are formed electronically, allowing them to be recorded and stored more easily than the images from photographic film.
How does a CT scan work ?	Computerised tomography (CT) scans involve taking a range of X-ray images from various positions. These are processed by a computer to build a three-dimensional (3D) image.
What are the advantages of a CT scan ?	• (images are) high quality or detailed or high resolution • (scan) produces a slice through the body • image can be viewed from any direction • an image can be made of any part (inside the body) • easier to diagnose or see a problem
What are the disadvantages of a CT scan ?	• (the X-rays used or scans) are ionising • mutate cells or cause mutations or increase chances of mutations • turn cells cancerous or produce abnormal growths • kill cells • metal/lead/glass/concrete shielding is needed
What is ultrasound and how is it generated ?	Electronic systems can be used to produce ultrasound waves, which have a frequency higher than the upper limit of hearing for humans.
What is the range of human hearing ?	The range of human hearing is about 20 Hz to 20 000 Hz.
How are images formed with ultrasound ?	Ultrasound waves are partially reflected when they meet a boundary between two different media. The time taken for the reflections to reach a detector can be used to determine how far away such a boundary is.
Show the calculation to determine the distance between interfaces in various media	s = v X t s is distance in metres, m v is speed in metres per second, m/s t is time in seconds, s
list the medical uses of ultrasound	• Pre-natal scanning • Imaging (a named body part). • removal of gall stones • removing plaque from teeth • repair of damaged tissue / muscle
Are there any risks to using ultrasound?	Ultrasound poses no risk / danger / hazard (to the user / patient). Ultrasound is not ionising
What precautions would you take with using ultrasound ?	The operator needs to take no precautions when making an ultrasound scan.
Describe how ultrasound waves can be used pre natal scanning	The human body is composed of different tissues such as muscle and skin. Ultrasound directed at the body will be partly reflected at the boundary between these different tissues. Used in pre-natal scanning to check that a foetus is developing normally and to take measurements of its growth.
How is ultrasound used to remove kidney stones	Kidney stones are solid crystals formed from substances found in urine. They can build up into large stones inside the kidney. These can then pass into the ureter and cause a blockage, accompanied by severe pain. High frequency ultrasound waves focused at a kidney stone cause it to vibrate, breaking it into small enough pieces to pass out in the urine.
Compare the medical use of ultrasound and X rays - bone fractures	Compared to ultrasound, X-rays have a much shorter wavelength (higher frequency). This means that X-ray photographs produce higher quality images than ultrasound scans. They show greater detail and clarity. This is vital in terms of detecting small bone fractures or abnormalities.
Compare the medical use of ultrasound and X rays - foetal scans	X-rays are ionising which means that X-rays damage living tissue and the DNA within cells. Rapidly dividing cells are particularly vulnerable to the effects of ionising radiation. This makes X-rays particularly damaging to a developing foetus. Ultrasound waves are not ionising, and so they are safe to use when performing a foetal scan.

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	Creado por david doran hace más de 7 años