Imaging
- Created by: Dan Riley
- Created on: 08-05-14 09:07
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- IMAGING
- X-RAY
- The part of your body being pictured is positioned between the X-ray machine and photographic film.
- You have to hold still while the machine briefly sends electromagnetic waves (radiation) through your body exposing the film to reflect your internal structure.
- Advantages
- Cheap
- Quick to do
- Can be interpreted by a non-radiologist
- Readily available
- Good bone resolution
- Disadvantages
- Ionizing radiation is harmful
- Poor soft tissue resolution
- 2-D images
- Bones, tumors and other dense matter appear white or light because they absorb the radiation.
- Less dense soft tissues and breaks in the bones let radiation pass through, making these parts look darker on the X-ray film.
- CT OR CAT scans
- The CT scanner uses a rotating X-ray tube.
- The patient is moved through this moving beam which collects a series of images called tomograms.
- The computerised images are more detailed than normal X-rays and help show clear pictures of organs inside the body, blood vessels, bones and tumours.
- Advantages
- More readily available than MRI
- Provides more detailed images, specifically soft tissue
- 3-D images
- Disadvantages
- Very high radiation doses
- Very high cost
- Patient has to be very still so image is focused
- If patient is claustrophobic then they may need to be sedated
- MRI scans
- A strong magnetic field is created by passing electrical currents through the wire loops
- While this is happening, other coils in the magnet send and receive radio waves. This triggers protons in the body to align themselves.
- Once aligned, radio waves are absorbed by the protons, which stimulate spinning.
- Energy is released after "exciting" the molecules, which in turn emits energy signals that are picked up by the coil.
- This information is sent to a computer which processes all the signals and generates it into an image.
- This creates a 3-D image of the area being examined.
- Advantages
- Does not involve ionising radiation
- Strong magnetic fields and radio waves not thought to be harmful
- Excellent soft tissue resolution
- 3-D images
- Disadvantages
- High Cost
- Cannot scan patients with metal implants
- Unsuitable for claustrophobic or obese patients
- Ultrasound
- Ultrasound is transmitted and received using a probe.
- A gel is used to fill the gap between the probe and the skin.
- This is to prevent reflection at this surface.
- The waves that do penetrate are reflected off internal organs, barriers, layers of tissue and interfaces.
- The echo patter of the returning waves is picked up by the probe.
- The ultrasound is viewed as a real-time picture on a monitor.
- Advantages
- Safe- does not involve ionising radiation
- No known harmful side effects
- Good soft tissue resolution
- No-invasive
- Relatively cheap
- Disadvantages
- Cannot see though bone
- Cannot visualise air filled spaces, such as lungs, as the sound waves are reflected at the tissue surface
- X-RAY
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