Imaging Flashcards
what is an x-ray?
A electromagnetic packet of energy with an extremely short wavelength (0.1 - 10 nanometers)
Describe the process of X-ray production and image capture.
- electron gun fires high energy electrons at a heavy atomic material (usually tungsten).
- collision creates ‘breaking radiation’ = X-rays
- directed at target being photographed
- bone absorbs rays - others hit imaging film behind
- emulsion contains silver halide - forms clumps on films upon exposure
Why do different things appear different on X-rays?
- tissues absorb different amounts of radiation.
least absorption to most -
Air < fat < muscle < bone
How does an ultrasound work?
fires sonic waves (sound waves)
frequency - 2-18 megahertz
What can an ultrasound scan?
soft tissue - muscles, tendons, monitors embryonic development.
what are the strengths and weaknesses of ultrasound?
strengths - inexpensive, portable , no long term side effects
weaknesses - has trouble penetration bone& scanning gas pockets, operator dependant,
What is a CT scan?
series of 2D x-ray images around an axis of rotation, to create a 3D image.
what are the strength and weaknesses of CT?
Strengths - can see lots of different planes
can differentiate between tissues of similar density
Weaknesses - reactions to contrast dye.
cancer
What is fluoroscopy?
real time moving images of internal patient
xray source , fluorescent screen behind patient
What are the strengths and weaknesses of fluoroscopy?
strengths - moving objections
weaknesses - patient exposed to ionising radiation and X-rays
Describe iodinated contrast media.
IV radiocontrast containing Iodine
Enhances visibility.
is nephrotoxic - can result in kidney failure.
Extra fluids must be administered after to ‘flush’ system.