Imaging
X-rays, MRI, CT/ CAT Scans, Ultrasound
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- Created by: Jemma
- Created on: 06-05-11 09:43
Imaging
X - Rays
Advantages
- Cheap and easy
- Can often be interpreted by any one (non - radiologist)
- Quick and readily available
- Good bone resolution
- Mobile lung and breast screening units are possible
Disadvantages
- Ionising radiation is harmful
- High - voltage supplies are a hazard
- Poor soft tissue resolution
- 2D images
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Imaging
MRI
Advantages
- Does not involve ionizing radiation
- Strong magnetic fields and radio waves not thought to be harmful
- Excellent soft tissue contrast
- 3D images
Disadvantages
- High cost
- Needs special facilities to have the equipment
- Need to take care that metal objects are not sucked in
- Patients with pacemakers cannot be scanned
- Some people feel claustrophobic
- Extremely noisy
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Imaging
CT or CAT Scanners
Advantages
- Provide more detail than conventional x - rays particularly for soft tissue
- Often more readily available than MRI in the UK
- 3D images
Disadvantages
- Very high radiation doses
- Much more expensive
- Patient has to be very still so image is focused
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Imaging
Ultrasounds
Advantages
- Safe
- Relatively cheap equipment
- More effective trhan X - Rays in producing images of sort tissue and some cancers
- Can be used in keyhole surgery
- Can measure blood flow and diagnosis of deep vein thrombosis (DVT)
Disadvantages
- Cannot see through bone
- Cannot visualise air filled spaces such as lungs as the sound waves are reflected at the tissue surface
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Imaging
X - Ray Facts
- Produced when electrons hit a metal, which in hospital x - ray tubes, is usually tungsten. The x - rays then pass through the body and onto either a film cassette or digital detector
- They use ionising radiation to produce a 2D image
- X - Rays are a type of electromagnetic radiation towards the high frequency end of the spectrum, which are absorbed by high atomic density materials
- Air in the bowels or lungs produce a dark/ black image + fat appears grey
- Used to look for suspected bone injury and can be used for diagnoses of pneumonia or some lung diseases including lung cancer
X - Ray machine An X - Ray
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Imaging
MRI Facts
- MRI - Magnetic Resonance Imaging
- Allows imaging of the interior body without x - rays or types of ionizing radiation
- Capable of showing fine detail of different tissues and can be used to diagnose conditions that can affect the brain and nervous system
- It can do this by producing a map which depends on the density of hydrogen in the body
- They produce images which are 2D slices through the body
- They allow you to see very small details which makes it an important tool for doctors
MRI scanner Example of a scan
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Imaging
CT and CAT Scans
- They use x - rays to produce images of one slice of the body at one time
- The patient lyes of the table and is moved through a doughnut shaped machine, this creates images that are slices through the patient
- It moves the x - ray tube and detector in a circle taking sliced x - ray images fromn all angles of the body
- The images are then processed by a computer which produce a cross sectional image
- CT/ CAT scans are ideal for examining sort tissue e.g. lungs, liver, kidneys, bladder and brain
CT scanner Example of a scan
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Imaging
Ultrasound
- Uses sound waves with frequencies between 1 and 10MHz to look inside of the body
- The frequencies above are too high to be heard by humans
- A gel is used so the probe makes good contact with the skin. The time taken indicates how deep in the tissue the ultrasound wave is being reflected
- Thought to be safe as does not use ionising radiation
- Computers can now generate 3D images and 4D videos can be made
Ultrasound Image
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