Medical Imaging Flashcards
What are 4 ionizing radiation imaging techniques?
- Plain Radiographs (x-rays)
- Computer Topography
- Fluoroscopy
- Nuclear Medicine
What are 2 non-radiation imaging techniques?
- Magnetic Resonance Imaging (MRI)
- Ultrasonography (ultrasound)
What are 2 non-radiation imaging techniques?
- Magnetic Resonance Imaging (MRI)
- Ultrasonography (ultrasound)
What is ionizing radiation?
Radiation that carried enough energy to free electrons from atoms or molecules, thereby ionizing them.
It is high energy radiation with potential adverse health effects.
- Found further up the electromagnetic spectrum than non-ionizing radiation
What is a Sievert?
a unit of effective equivalent dose in the human 1 J/Kg
- the mSv is the unit used to describe the dose received by a patient for an ionizing radiation used in medical imaging
What is a grey?
A unit of dose in the human - 1 Joule per Kg
How many mSv does the average UK resident receive per annum?
= 2.5 mSv
How many mSv is received after an intraoral x-ray?
= 0.005 mSv
(1 days worth of radiation)
How many mSv is received after a computed tomography CT - chest ?
= 7 mSv
(2 years of radiation)
How many mSv is received after radiography - chest ?
= 0.1 mSv
(10 days of radiation)
What is the aim to produce with all imaging procedures?
= an image contrast
The imaging technique emphasizes certain contrast characteristics of anatomical structures allowing us to differentiated structures and determine which structures are abnormal.
In x-rays what does denser material (bone) show up as ?
Denser material = white
(Rays are blocked from reaching the film)
In x-rays what does less dense material show up as ?
Less dense = black
What colour would gas, fat, water and soft tissue show up on an x-ray?
= Black and grey
What colour would bone or metal show up on an x-ray?
= White
Why do x-rays need to be taken at different postions?
Anterior/ posterior and lateral x-rays have to be taken to allow a full 3D view of the area.
Therefore a CT scan is not needed.
What are 5 positives of x-rays?
- Fast
- Non - invasive
- Painless
- No special prep required
- No recovery time
What are 5 negatives of x-rays?
- Risk of radiation
- Can be low image quality
- Distortion
- Not good for viewing soft tissues
- Inappropriate during pregnancy
How do fleshy organs show up in a CT skan?
Fleshy organs area uniform in density
Computer enhanced techniques differentiate varying shades of grey.
What images are produced in CT scans?
Transverse / horizontal images produced
What are 6 positives of CT scans?
- Fast
- Non-invasive
- Painless
- No special prep required
- No recovery time
- Better for soft tissue
What are 3 negatives of CT scans?
- Higher radiation risk
- Contrast issues
- Inappropriate during pregnancy
What can a contrast medium be used for?
Can be used to examine structures that don’t have inherent contrast differences
e.g.
- radiopaque
- GI system
- Lungs (air)
- Urography
- Angiography - arterial system contrast
medium
What are 2 positives of a contrast medium?
- Excellent differentiation of tissues
- Sequential images - follow through
What are 6 negatives of contrast medium?
- Special preparation
- Adverse reactions
- Recovery time
- Invasive
- Slower
- Transverse
What is MRI imaging?
MRI scans essentially map the location of water and fat in the body
Detect differentiation of abnormal and different tissues.
What are 8 positives of MRI scans?
- Excellent differentiation of tissues
- Sequential images - follow through
- Any plane
- Images structures better without contrast
- Non invasive
- Detect abnormal tissues
- No risk to “normal” patients
- No radiation
What are 5 negatives of MRI scans?
- Scans take longer
- Patient has to remain completely still (hold
breath) - Bowel movements and heart in constant
motion - Distortion from metallic implants, fillings
- Cost
What is ultrasound?
A non invasive imaging that uses high frequency sound waves, echoes and reflections to generate an image.
What are positives of ultrasound?
- Quick
- Low cost
- Portable
- No radiation
- Risk free
- Use on “high risk” patients
- Live feedback - not static
- Biopsy
What are negatives of ultrasound?
- Varying quality
- Unable to cross tissue gas of tissues bone
boundary - Gas containing structures can obscure
deeper tissues - High degree of technical skill
How can treatments be changed to create a diagnosis method?
e.g. Radiography to Radiotherapy
Extremely high doses of ionising radiation concentrated at a target e.g. tumour
e.g. Ultrasound to Therapeutic Ultrasound
High amounts of focused waves aimed at e.g. breaking up a kidney stone
