myocardial perfusion imaging

thallium (Tl) 201
- acts as potassium analog
- dose 3.0 - 5.0 mCi at peak exercise
- 4% of injected dose --> myocardium
- imaging: "exercise" (5-10 min), "redistribution" (3-4 hrs)
- views: anterior, LAO 45', left lateral
- interpretation:
  - normal
  - reversible abnl ==> exercise-induced ischemia
  - nonreversible abnl ==> prior MI
  - reverse redistribution ==> normal areas wash out faster
  - lung activity ==> LV failure during exercise
Tc99m sestamibi
- myocardial uptake proportional to perfusion
- no redistribution
- dose 25mCi
- imaging: optimal at 1hr but maybe satisfactory out to three hours