Radiopharmaceuticals for Cardiac Imaging
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What is the sequence of events in CAD?
- Endothelial inflammation
- Plaque formation
- Flow limiting CA stenoiss
- Ventricular dysfunction
- ECG abnormality
- Chest pain
What are the 4 cardiac imaging SPECT agents?
1. Tl 201 Thallous Chloride
2. Sestamibi<Cardiolite> (used for heart and breast img)
3. Tetrofosmin <Myoview>(used for heart img)
How is sestamibi labeled?
1. Add Tc 04 to kit and heat in boiling water for 10 min
Tc04 + citrate ------> Tc Citrate
2. Copper complex is broken; free MIBI ligands displace citrate forming Tc Sestamibi
**MIBI is an oily liquid that has to be compounded to coppper**
How is tetrofosmin labeled?
1. Add up to 240 mCi of Na99mTcO4 in 4-8 mL in kit.
2. Remove 2ml of N2 gas from vial to admit air.
3. Incubate 15min, use w/n 12 hrs.
*Hydrogen radical H+ and hydrated electron e- are reducing species. Letting air into the vial allowes O2 to scavenge the reducing species*
*Tetrofosmin is mixed with gluconate to keep it soluble*
What are 3 PET imaging agents?
- 1.Rb 82
- 2. F18-FDG
- 3. N-13 Ammonia
Thallium has what type of transport and heart retention?
- Active transport
- -K+ analog, remains in heart longer than K+
Which PET agents are perfusion markers and which are viability markers?
- Blood flow markers:
- -N13 Ammonia
What are the 2 requirements for a MYOCARDIAL PERFUSION agent?
- 1. High first pass extraction
- 2. Remain fixed in the heart long enough to image
What is the typical blood flow for rest and stress?
- REST: .6-.8 mL/min/g
- STRESS: 3-4 mL/min/g
What are the 3 axis for cardiac tomography?
- 1. Short axis
- 2. Vertical long axis
- 3. Horizontal long axis
How does adenosine and dipyridamole work?
- Both are vasodilators
- Increase CA blood flow 4-5x
- *Adenosine directly stimulates CA receptors WHILE
- dipyridamole blocks adenosine re-uptake
**Caffiene BAD bc it blocks adenosine from reaching receptors...stop 12 hrs prior**
How is a Thallium redistribution study performed and what are the problems with it?
- 1. STRESS: Inject 3-4 mCi; DTST 15 min
- 2. WAIT 2.5-4 hr; take rest images
- Sensitivity is high but specificity is low
What are the infusion rates for regadenosine, adenosine, dipyridamole?
regadenosine: BOLUS (inj given after)
dipyridamole: 4 min (inj given after)
adenosine: 6 min (inj given half way)
How are cardiac images interpreted?
- 1. Extent: Large, med, or small
- 2. Severity: marked, moderate, mild, or questionable.
- 3. Reversibility:
- Ischemia: completely reversible-partially reversible
- Scar: permanent (not reversible)
- 4. Interpretation can be:
- -Qualitative, semi-quantitative, quantitative
Is survival better with revascularization or medical therapy?
What are 3 benefits of PET perfusion studies?
- 1. Less attenuation artifacts
- 2. Quantitative
- 3. High signal to noise ratio
Name the study sequence for Rb82 Chloride stress test
- 1. Rest CT
- 2. Rest Study (40 mCi)
- 3. Stress Study (Regadenosine + 2nd inj)
- 4. Stress CT
What is special about F18 Flurpidaz?
- Has a higher 1st pass extraction flow compared to MIBI and Tl 201
- CAN DO exercise study
What are the 3 goals of Myocardial Ventriculography?
- 1. Assess ventricular wall motion abnormalities
- (Hypokenesis, akenesis, dyskenesis)
- 2. Assess systolic wall thickening
- 3. Measure EF and volumes
What are the 2 types of Myocardial Ventriculography studies?
- 1. FIRST-PASS Angiogram Study
- -IV bolus TcO4
- evaluate R and L EF
- 2. ECG Gated Equilibrium Study (MUGA)
- -IV inj of RBC's, MIBI, Tetrofosmin
- -Assess L EF only!!
What are the 2 methods of tagging 99m Tc to RBC's?
- 1. In Vivo
- -Inject Sn-PYP (Sn associates with hemoglobin, reducing the Tc and allowing it to tag to hemoglobin)
- -Wait 20 min
- -Inj 30 mCi of TcO4
- 2. Modified In Vivo Method
- -Inject PYP; wait 20 min
- -Remove 10mL blood w/ heparinized syringe containing 30 mCi of TcO4
- -Incubate 10 min; reinject pt.
State the formula for EF
What is the purpose of Viability assessment?
Determine if revascularization would benefit the patient
SPECT : Tl201 Thallium Chloride (Rest/Redistribution Study)
PET: N13 or F18 FDG (Perfusion/ Metabolism Study)
How do you perform a PET perfusion study with N13 Ammonia?
- 1. High carb meal
- 2. Inject 25 mCi
- 3. Acquire CT image
- 4. Wait 4 min to allow blood clearance
- 5. Acquire PET images
**Follow with F-18 FDG Metabolism Study (make sure glucose is within range; inj 15 mCi)**
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