Imaging, infection, inflam and ca Flashcards

1
Q

Scientific basis of PET

A
  • Type of molecular imaging
  • Uses radionuclides that decay by positron emission.
  • Proton -> neutron + positron
  • Can be used for absolute quantitation but requires arterial samples
  • Gamma rays emitted indirectly by a PET radionuclide are introduced into the body on a biologically active molecule
  • A 3D image can be seen by a PET-CT
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2
Q

Ideal isotope for labelling

A
  • Need short half-life, similar to length of examination
  • Needs to be a gamma emitter
  • Should be readily available at hosp. site
  • Can be easily bound to pharmaceutical component
  • Easy to prepare
  • Examples: F18, is commonly used. C11 is used for prostate
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3
Q

Scientific basis for MRI

A
  • Strong magnetic field aligns protons in the body in one direction
  • Radiofrequency pulse displaces protons and images created by displaying time taken for protons to ‘relax’ back to original alignment
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4
Q

Indications for MRI-specific contrast agents

A
  • Excellent bone and soft tissue detail
  • Vessel can be demonstrated
  • Brain, spine and MSK
  • Abdo and pelvis
  • Cardiac imaging
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5
Q

Contraindications for MRI-specific contract agents

A
  • Claustrophobic and noisy
  • Motion artefact
  • Cannot image patients with pacemakers, aneurysm clips unless they’re compatible with an MRI
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6
Q

Example of contrast agent used in MRI

A
  • Gadolinium DTPA
  • IV contrast medium, causes changes in local magnetic field and alters tissue signal
  • Vascular lesion and some tumours can be more easily seen
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7
Q

Patient safety issue specific to MRI

A
  • Pacemakers, aneurysm clips
  • Projectile risk, metal in room being pulled over and hitting patient
  • Claustrophobia and discomfort
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8
Q

Clinical applications of imaging for diagnosis

A
  • Make initial diagnosis
  • Stage disease
  • Monitor response to treatment
  • Evaluate residual mass after treatment: always going to be residual mass. It’s just whether it’s cancerous or scar tissue
  • Assess when there is concern of relapse
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9
Q

Pros and cons of population screening with radiological testing

A
  • Should detect disease at an early stage where treatment can alter outcome
  • Test should cause no harm
  • High sensitivity/specificity
  • Benefit to individual and population should outweigh cost
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10
Q

Guidelines used judicious use of imaging

A

ALARA, as low as reasonably possible

  • Ensure whether examination is necessary
  • Need enough clinical infor for appropriate protocol
  • Minimise repeat examination
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11
Q

Detection of gamma radiation and production of digital image by gamma camera

A

Gamma ray is emitted from the patient, image crystal produces flashes of light
This is displayed as an image

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12
Q

Detection of gamma radiation and production of digital image by PET

A
  • Dual head gamma camera
  • PET tracers emit positrons that annihilate with electron that cause 2 gamma photons to be emitted in opposite directions
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13
Q

Detection of gamma radiation and production of digital image by SPECT

A
  • Gamma cameras rotate around area of interest
  • Also uses a radionuclide tracer
  • Tracers in SPECT emit gamma radiation which is measured directly and gets a 3D image
  • Used in brain, cardiac and lung
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14
Q

Currency of radiation

A
  • Emission energy - keV

- PET scans 50-300 keV

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15
Q

Examples of diseases you can diagnose

A
  • Inflammation: rhematoid arthritis, aortitis (tram tract activity in scnas), ulcerative colitis
  • You can also stage a tumour
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