introduction to imaging MW % + Flashcards

1
Q

What is an x-ray?

A

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

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2
Q

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

A
  • 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.
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3
Q

What is attenuation?

A
  • 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
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4
Q

What happens when X-Ray interacts with Matter?

A
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5
Q

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

A
  • 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.
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6
Q

What is Digital Radiography?

A
  • Same xray tube generation
  • Digital acquisition
  • Networking of images
  • Picture Archiving and Communication System
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7
Q

How does Ultrasound work?

A
  • 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
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8
Q

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

A
  • 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
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9
Q

What are the complications of Barium use?

A
  • Bowel disturbance (very common)
  • Colonic perforation at enema –Very rare (<1:25,000)
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10
Q

What is computed technology?

A
  • Rotating x-ray tube
  • Multiple beams
  • Single axis of rotation
  • Often give Iodinated Contrast
  • IV contrast can lead to kidney failure
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11
Q

What is the point of using iodinated contrast media?

A
  • It enhances the visibility of some structures within the body.
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12
Q

What are Radiation types?

A
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13
Q

Describe the scientific basis of the hazards of ionising radiation?

A
  • 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.
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14
Q

Attenuation coefficients (comparision)

A
  • Air< Fat< Muscle< Bone< Contrast Agents/Metal implants
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15
Q

Barium in clinical investigation

A
  • Swallow and meal - oesophagus, stomach and duodenum
  • Small bowel study - small bowel
  • Enema - large bowel
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16
Q

When is computed Tomography used?

A

•Extensive applications throughout the body

–Trauma

–Cancer staging and response to treatment

–Guidance for procedures

  • Great for defining bony detail
  • Exposure to radiation
17
Q

Minimising Exposure

A
  • 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