X-Ray Flashcards

1
Q

What is attenuation?

A

the reduction of the force/ energy of X-rays

- increases with higher atomic number and density

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2
Q

What is the difference between transmission and emission imaging?

A

Transmission = radiation is directed through the patient. Transmission is collected essentially showing a map of attenuation. Good at showing structure, especially between tissues of different densities or atomic number
Emission imaging = radiation is administered to a patient as a tracer. Emitted radiation is detected outside the patient.

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3
Q

What are the different detectors in planar X-ray?

A

Film hardcopy - film processor with tanks of chemicals. High resolution.
Computed radiology computer copy - digital enhancement and archiving
Digital radiology - flat panel detector, fully digitalised.

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4
Q

How are mammography X-rays done?

A
  • use a compression plate to reduce breast thickness, improving the resolution and lowing radiation dose.
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5
Q

What is fluoroscopy?

A

Real-time imaging involving injecting dye into an artery. Allows you to see blood flow inside vessels.

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6
Q

Limitations of planar x-ray

A
  • cant distinguish between overlying tissues

- tissues other than those being observed reduce the contrast

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7
Q

How is a CT scan carried out?

A

Patient lays inside the aperture of the machine.
An X-ray tube rotates around the patient very quickly - helical scanning
Fires x-rays each rotation - detected to give image.

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8
Q

How can CT be used to measure disease progression?

A
  • measure the size of the left inguinal lmyph node
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9
Q

How does nuclear medicine/emission imaging work?

A
  • radioactive tracer is injected - patient emits gamma rays

- imaging depends on metabolism of the tracer.

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10
Q

What is gamma camera imaging?

A
  • uses single photon emitting radionuclides - decay with direct emission of gamma rays
  • can operate in 2d (planar) or 3d (SPECT)
  • most common radionuclide is Tc-99m
  • records gamma rays and collects image over time
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11
Q

What is SPECT?

A
  • single-photon emission computed tomography

- Acquires up to 64 images from around the head

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12
Q

What is FDG?

A
  • the most commonly used tracer in PET scans

- a glucose analogue, enters the cells in the same way

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13
Q

How does PET scanning work?

A
  • Injected radionuclides emit a positron as they decay. When the positron meets an electron, there is an annihilation event, where two gamma rays are produced.
  • These are detected by a ring of scintillation detectors
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14
Q

What combinations of imaging can you do in hybrid imaging?

A

PET-CT
SPECT - CT
PET-MR

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15
Q

Which technique has the best resolution?

Best to worst

A
  • X-RAY
  • CT
  • PET
  • PLANAR- NM
  • SPECT
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16
Q

Which technique has the best contrast?

Best to worst

A
  • PET
  • SPECT
  • PLANAR-NM
  • CT
  • X-RAY
17
Q

What is attenuation correction?

A

Occurs in PET-CT.

  • gamma rays coming from the centre of the patient will travel through more tissue, meaning they are attenuated more
  • CT image is used as an attenuation map to correct the PET image.