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Year 1 - Organisation of the Body > 7.7 Imaging > Flashcards

7.7 Imaging Flashcards

1
Q
  • Who discovered the properties of X-rays?
A

Willhelm Conrad Roentigen in 1895

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2
Q

What are X-rays and how are they generated?

A
  • Part of the EM spectrum, very short wavelength (0.1-1 angstrom units)
  • Generated by high energy electrons striking a tungsten target within a vacuum tube
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3
Q

What are the different types of imaging?

A
  • Plain X-ray
  • Barium radiology
  • Ultrasound
  • Angiography
  • Computed tomography (CT)
  • Magnetic resonance imaging (MRI)
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4
Q

How do X-rays work?

A
  • Transmitted beam is recorded on an X-ray film
  • Image phosphor read by a computer (CR)
  • Direct digitisation (DR)
  • Image intensifier
  • Stored on the picture archiving and communication system (PACS)
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5
Q

What are the advantages of plain X-rays?

A
  • Quick
  • Cheap
  • Great detail
  • Widely available
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6
Q

What are the disadvantages of plain X-rays?

A
  • 2D representation only
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7
Q

How are the risks of diagnostic radiology managed?

A
  • Doses are kept As Low As Reasonably Achievable (ALARA)
  • Radiation techniques should be avoided in pregnant and potentially pregnant women
  • Non-radiation techniques should be used where possible and appropriate
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8
Q

What units are used to measure effective doses of radiation?

A

mSv (milli-Sieverts) - lifetime risk of fatal cancer 5-5.9% per Sv - there is a small risk, but it is managed

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9
Q

What is the frequency used in high frequency ultrasound?

A

2-15MHz

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10
Q

What is doppler ultrasound techniques?

A

Use the doppler effect to measure the movement and volume of blood through veins and arteries

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11
Q

What are the advantages of ultrasound?

A
  • High quality information about soft tissues
  • No ionising radiation
  • Inexpensive (5-50% cost of a CT)
  • Flow information available
  • Easily portable and lots of variable sizes
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12
Q

What are the disadvantages of ultrasound?

A
  • Gas and bone block US beam
  • Obesity degrades image quality
  • Operator dependant
  • Pixel brightness is not quantitative
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13
Q

What is scintigraphy?

A

Where a scintillation counter or similar methods are used to obtain images of organs that have taken up radioactive tracers, or records of their activity.

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14
Q

What is the most common radionucleotide used in scintigraphy?

A

Technetium - 99m

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15
Q

What are the principles of scintigraphy?

A
  • Radiation emitting
  • External solid state detector
  • Data collection, then image generation and display
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16
Q

Why is ^99m Tc used?

A

Short half life, but long enough to allow for uptake and detection within the body (6 hours)

17
Q
  • What is bone scintigraphy?
A

A method of viewing bones as ^99m Tc is taken up by osteoblasts, just need to wait for the soft tissue phase to pass. Take image 3-4 hours after injection.

18
Q
  • What else can scintigraphy be used for?
A

Renal imaging - able to detect whether kidneys are obstructed or not

19
Q

What is PET imaging?

A

Positron Emission Tomography

  • A radioactive dye is ingested that accumulates at areas of increased metabolic activity
  • Dye emits positrons that will annihilate with electrons and release photons which can then be detected
20
Q

What is PET-CT?

A

This is where PET and CT scans are combined together in a POWERFUL diagnostic tool

21
Q
  • Who created CT??
A

Godfrey Hounsfield, won the Nobel prize in 1979

22
Q

What is CT?

A

Computed Tomography

  • Attenuation of transmitted X-rays measured by electronic detectors
  • Produces detailed images of internal structures, including bone and soft tissue
23
Q

What is multi-slice CT?

A

This is where multiple CT solid state detectors rotate around the patient (0.5s rotation speed, 0.5-0.625mm slice thickness).

24
Q

What units are used in CT?

A

Hounsfield units

25
Q

What are the HU principles for CT?

A

Bone: +1000 HU
Water: 0 HU
Air: -1000 HU

26
Q

What is MRI?

A 
Magnetic Resonance Imaging 
- 1.5 Tesla (30000x Earth's field)
- Radiofrequency of 63.9MHz
- 2D and 3D images
A large magnet aligns the protons of hydrogen atoms within the body, then the radio waves causes them to rotate. Once turned off, the protons relax and emit radio waves which can be picked up by the detectors, forming an image - different hydrogen atoms in different tissues have different energies, resulting in different results/colours and consistencies on the image.
27
Q

What are the basics of MRI?

A
  • High strength magnet
  • Shim coils
  • Gradient coils
  • Radiofrequency coils
  • Computers are used to control gradient and RF coils, reconstruct images
  • Creates both 2D and 3D images
28
Q

What is functional MRI/fMRI?

A

A variation of MRI that looks at blood flow, as oxyHB and deoxyHB have different signal intensities - can be used to see which areas of the brain are used to control different actions, as when activated will have a higher blood flow to that area.

29
Q

What is x-ray attenuation?

A

The reduction of intensity of the beam as it is absorbed by/transverses matter.

30
Q

What are the colours of different tissues in CT and x-ray?

A

Bone: White (absorbs most)
Fat: Varied shades of grey
Soft tissues: Varied shades of grey
Air: Black (absorbs least)

CT works on x-ray principles so same colours seen

31
Q

What is radiography?

A

The use of ionising and non-ionising radiation in imaging and viewing the internal forms of objects.

32
Q

What is angiography?

A

A method of imaging the inside/lumen of various body cavities, in particular blood vessels and chambers of the heart. Uses x ray imaging - contrast agents are used to allow the lumen to show up

33
Q

What are contrast agents?

A

Substances used to increase contrast of different structures within the body, absorbs or alters electromagnetism or ultrasound, resulting in a different colour seen in the screen.

34
Q

What are radiopharmaceuticals?

A

Substances used for imaging that emit radiation themselves, so are able to be viewed using specific detectors (almost always gamma radiation).

35
Q

What is the main use of radiography/x-rays?

A

Most frequently used to image bones, but chest x-rays are also common.

36
Q

What is the main use of CT scans?

A

To take highly detailed images of the brain and other internal soft tissues.

37
Q

What is the main use of ultrasound?

A

Imaging and visualising (done live) of foetuses and other soft tissues when high quality is necessarily needed.

38
Q

What is the main use of nuclear medicine?

A

Imaging of digestive systems or other circulatory systems, often to look for blockages

Year 1 - Organisation of the Body (20 decks)

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