introduction to imaging MW % + Flashcards Preview

ME2308 Principles of Disease > introduction to imaging MW % + > Flashcards

Flashcards in introduction to imaging MW % + Deck (17)
Loading flashcards...

 What is an x-ray?

An electromagnetic packets of energy with a wavelength between 0.1 and 10 nm. 


Recall in general terms the principles of xray generation and image capture.

  • All x-ray machines contain X-ray tube envolped by a vacuum with a  cathode emitter and an anode target.
  • The cathode emitter is -ve charged, so emits -ve charged electrons and the electrons travel to the anode as it the opposite charge.
  • As the electrons hit the anode, energy is released in the form of photons which are then converted into X-ray beams.
  • These x-ray beams go through the patients body and an image is produced. 




What is attenuation?

  • The process by which radiation loses power as it travels through matter and interacts with it.
  • Increases with Z (atomic number)
  • Increases with density

  • Increases with thickness


What happens when X-Ray interacts with Matter?


Explain why different anatomical structures have different appearances on x-ray imaging?

  • Different stuctures within the body have different attenuation.
  • Fats have a lower attenuation coefficient compared to bones which have high attenuation coefficient.
  • So depending on how much radiation is absorbed, the image produced will be different.



What is Digital Radiography?

•Same xray tube generation

•Digital acquisition

•Networking of images

•Picture Archiving and Communication System


How does Ultrasound work?

  • Transmitts a high frequency sound pulses
  • Sound waves travel through the body until they hit a  boundary between tissues.
  • There some of the waves are reflected back and the rest travel again until they hit another boundary
  • The reflected waves are picked up by the probe and the machines calculates them and produces a 2D image


What is Barium and why is it used in Barium studies?

•A radio-opaque contrast agent used for outlining the gastro-intestinal tract

•The high atomic number of barium absorbs more x-ray photons than surrounding tissues


What are the complications of Barium use? 

•Bowel disturbance (very common)

•Colonic perforation at enema –Very rare (<1:25,000)


What is computed technology?

•Rotating x-ray tube

Multiple beams

•Single axis of rotation

•Often give Iodinated Contrast

•IV contrast can lead to kidney failure


What is the point of using iodinated contrast media?

  • It enhances the visibility of some structures within the body.




What are Radiation types?


Describe the scientific basis of the hazards of ionising radiation?

  • Ionising radiation is a wave which has sufficient energy to knock electrons out of atoms/molecules leaving them as negatively or postively charged.
  • This disrupts the chemical bonds within the tissues in the body,therefore it has health consequences.








Attenuation coefficients (comparision)

  • Air< Fat< Muscle< Bone


Barium in clinical investigation

•Swallow and meal - oesophagus, stomach and duodenum

•Small bowel study - small bowel

•Enema - large bowel



When is computed Tomography used?

•Extensive applications throughout the body


–Cancer staging and response to treatment

–Guidance for procedures

•Great for defining bony detail

•Exposure to radiation


Minimising Exposure

  • As the distance from a radiation source doubles, the exposure rate decreases by a factor of four
  • Use Shield to protect staff and patients

  • Minimise the time exposed to radiation