EM Notes – Nuclear Medicine

Cardiac Scans

201Tl (Thallium)

  1. Thallium acts as K+ analogue.
  2. Taken up by myocardial cells and reveals myocardial perfusion.
  3. Can do stress testing with exercise or dipyridamole.
  4. “Cold” spots show areas of ischaemia, if irreversible infact
  5. Higher radiation dose than sestamibi scan.

99mTc (Technetium) sestamibi

  1. 99mTc decay (isomeric transition to 99Tc) detected using a gamma camera for single photon emission computed tomography (SPECT)
  2. Acute imaging (while patient having chest pain) highly sensitive for sig. IHD.
  3. Imaging performed 60-90min post-radioisotope injection.
  4. Scanning can be performed up to 5hr after injection.
  5. Images acquired at rest and after stressing (exercise or pharmacologically).
  6. Scans compared to find ischaemic/infracted areas and & wall motion abnormalities
  7. 99mTc sestamibi has T½ of 6hrs so may need rpt dosages.

99mTc tetrofosmin

  1. Longer T½ than sestamibi so only 1 injection needed.

99mTc pyrophosphate

  1. Early (1st 7d) diagnosis of AMI
  2. Necrotic tissue takes up radioisotope and forms a “hot” spot.

99mTc labeled RBC

  1. Gated cardiac blood pool scan
  2. Looks at ejection fraction, wall motion, regurgitation fraction
  3. Used prognostically in AMI, pre-chemo, or for SOB investigation.

Other Tc Scans

  1. V/Q scan
  2. Labelled RBC scans for GIT bleeding
  3. Bone scans – detects 95% #s at 72hr, also detects Ca, mets, arthritis, infection & avascular necrosis
  4. DTPA, DMSA & MAG3 renal scans

111Indium WBC

  1. Shows areas of acute infection/inflammation

67Gallium

  1. Binds lactoferrin & transferrin
  2. Shows areas of chronic infection/inflammation, PCP in immunosuppressed.

Positron Emission Tonmography (PET)

  1. Positrons (e+) from 11C, 15O, 13N, 18F collide with an e- 2 x gamma rays as particles annihilated.
  2. Uses: Localisation of epileptic foci, myocardial function, brain area activity (glucose utilization)
  3. Can be used to measure: local blood flow, metabolic activity, drug movement, neurotransmitter receptors, enzymes
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