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14 Cards in this Set

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What is considered the "gold standard" for diagnosing cororany arterial blockage?
Cardiac Catheterization
why then is it not done as much as nm MPI?
It is invasive, time consuming, high pt radiation dose and has a high incidence of complications
When doing a thallium cardiac perfusion study what is the dose and what is its energy level for imaging?
Tl-201 Thallous Chloride 3-4 mCi
68-80.3 keV
it is cyclotron produced

How is it localized?
Thallium behaves in the body like potassium and is absorbed well into myocardiac muscle through active transport
uptake occurs 5-10 min post inj and washes out in 4 hrs
Can the patient eat anything after the Thallium stress while waiting for the rest redistribution imaging 3 hrs later?
no, if they eat the thallium will redistribute to the stomach
What was the primary reason MPI was changed from Tl-201 to Tc99m?
Tl201 has a relatively long half life, resulting in high pt dose, so less is administered which results in lower count rate and also the energy level is too low for optimal camera efficiency
How does Sestamibi localize?
It passes cell membranes passively, the driving force is negative membrane potential, uptake depends upon regional blood flow.
It further accumulates, once it is intracellular, into the mitocondrias
Why do you have to reinject a 2nd dose with sestamibi and not with Tl201 between stress and redistribution?
thallium redistributes well in the myocardiaum and sestamibi does not
Why is the 2nd dose 3 times higher than the 1st in sestamibi MPI?
The higher dose for the second part of the test is required to obscure the activity from the first part of the test
Why would it be a bad idea to use Tc-99m first in the dual isotope techniques with Tl-201?
Because of all the scatter from the Tc since Tl is lower peak
What is the one advantage to using myoview over sestamibi?
It has a more rapid clearance time from the myocardium, making same day imaging more effective
What is the patient prep for MPI with adenosine?
NPO for at least 3 hrs
no theophylline, aminophylline or caffine containing drugs
what is the procedure for infusion and isotope injection?
administered intravenously for 6 min with pt lying down, isotope injected after 3 min
vital signs monitored constantly until 5 min after stop of infusion
What is one problem with using adenosine?
Side effects can be severe (chief complaint is headache)
what is the remedy?
injection of aminophylline
side efffects do not last long and usually terminate after infusion has stopped
How is Dipyridamole (persantine) administered?
Dipyridamole is also a vasodialator and is probably used in chemical stress testing more than the other available drugs. It preferentially dialates the good coronary arteries. It differs from adenosine by its longer half life of 15 – 30 minutes. It works by blocking adenosine receptor sites causing an increase of free adenosine in the blood.
The dipyridamole is administered intravenously by a properly trained nurse or technologist for 4 minutes. The isotope is injected 7 – 9 minutes after the infusion has completed. Vital signs are taken every minute during the infusion and 15 minutes post infusion. 
Why will dipyridamole (persantine) not work on a malnourished patient?
persantine is carried in the blood by albumin and in a malnourished pt the albumin is very low
How does dobutamine work?
Dobutamine works by increasing the muscular contraction of the heart and increasing the demand for oxygen. It has a 2 minute plasma half life. This drug may be chosen for a patient with contraindications for use of a vasodialator. For instance, a patient who cannot be taken off of aminophylline can be stressed using dobutamine.
The dobutamine is administered intravenously by a properly trained nurse for approximately 16 minutes with the patient lying down. The isotope is injected during the 13th minute of infusion. Vital signs are taken every minute during the infusion and 5 minutes post infusion.
why is this the least favorable choice for stress testing?
Side effects of dobutamine can be severe and up to 70% of patient experience them. This incidence of side effects of dobutamine makes it the least favorable choice for chemical stress testing. The risk/benefit ratio must be considered before this drug can be used. An intravenous beta blocker can be used to counteract the effects of dobutamine.