Nuclear Cardiology review

Flashcards from Nuclear Cardiology Review slideshow

What Radiopharmaceuticals are used in Nuclear Cardiology

Thallium-201

Tc-99m Sestamibi (Cardiolite)

Tc-99m Tetrofosmin (Myoview)

PET: Rubidium-82 chloride, Oxygen-15 water, Nitrogen-13 ammonia

What is the dose for dipyridamole/persantine?

0.56mg/kg in 50ml of saline over 4min

What is the dose for adenosine?

0.140mg/kg/min for four minutes

What is the dose for regadenosine/lexiscan?

0.4mg (5.0 ml)

When is the tracer injected for a pharmacological test using adenosine/adenoscan?

During 3rd minute of infusion

When is the tracer injected during a pharmacological stress test using regadenosine/lexiscan?

20-30sec post injection of pharmacological drug

When is the tracer injected for a stress test using dipyridimole/persantine?

3-5min post completion of injection

When is the tracer injected during a chemical stress test using dobutamine/dobutrex?

1min after max tolerated dose

infusion should continue for at least 1 min

What medication can be given to reverse the side effects of coronary vasodilators during a chemical stress test?

Aminophylline

What can be given to reverse the side effects of dobutamine/dobutrex?

Beta blockers

Name two radiopharmaceuticals used to assess viability

Thallium-201 and F-18 FDG

What are three advantages of Tl-201 imaging?

Redistribution into ischemic tissue over time

increased lung activity after exercise is a marker for CAD

absence of significant hepatobiliary activity.

What are four disadvantages of Tl-201 imaging?

Long half-life limits dose

low dose results in poor count rate

low energy poorly suited for imaging

gated SPECT problematic because of redistribution.

Are Tl-201 studies typically gated or nongated? why?

nongated

due to redistribution

What is reinjection in Tl-201 imaging?

Injecting 1-1.5 mCi of Tl-201 prior to rest imaging to demonstrate reversible ischemia more readily, increasing senstiivity of stress/redistribution

When does imaging begin after stress with TI-201?

5-10 minutes post injection

What happens if you wait too long to image after stress with TI-201?

False negative result due to redistribution

When is imaging performed for rest images with TI-201?

3-4 hours post injection

What are the instructions for the patient between stress and rest imaging when using tl-201?

Patient should fast or have a light meal only (clear liquids) and avoid physical activity.

Why should the pt be instructed to fast or have a light meal of clear liquids only between stress and rest scans usign tl-201?

eating between scans can have a negative effect on redistribution

• Glucose ingestion results in increased clearance of tl from myocardium

What are seven advantages of Tc agents over Tl-201?

Tc-99m has more optimal energy

higher injected dose = more photons = better sensitivity

higher target-to-background ratio

more rapid acquisition

improved resolution

more favorable dosimetry

fixed distribution provides flexibility and permits SPECT gated studies

What are the disadvantages of Tc agents over Tl? (4)

Slightly lower blood clearance than Tl

Two doses required

activity in the liver, biliary, and bowel can cause artifacts

Myocardial extraction lower than Tl

T/F: its important that pts continue to exercise for at least 1 minute post injection of the tracer

true

How are tc agents produced?

generator/kit

What is the half life of Tc agents?

6.02 hrs

What is the energy of Tc agents?

140keV

What is the mechanism of localization of Tc agents?

passive diffusion

What is the mechanism of localization for Tc Agents?

Passive diffusion

By which route is Tc-99m Sestamibi cleared from the body?

Hepatobiliary - large intestine

How is Tc-99m Tetrofosmin cleared from the body?

Hepatobiliary - gallbladder

What is a typical dose of Tc-99m Sestamibi?

10-30mCi

What is a typical dose of Tc-99m tetrofosmin?

5-24mCi

How do the doses compare when using a 1-day protocol vs a 2-day protocol?

1-day: smaller dose used in 1st imaging study and larger dose in 2nd imaging study

2-day: larger dose used for both studies

What are the imaging times post-injection for Sestamibi and Tetrofosmin?

Stress: 15-60 minutes post injection

Rest: 30-90 minutes post injection.

What are the advantages of tetrofosmin over Sestamibi in MPI imaging?

imaging can begin earlier bc:

• rapid uptake

• faster background from liver and Lung

What is the critical organ of sestamibi?

large intestine

What is the critical organ of tetrofosmin?

gallbladder

How long after injection can images be acquired?

up to 4 hrs post inj

How is imaging time selected when using Sestamibi and tetrofosmin for MPI imaging?

to minimize interfering liver, GB and bowel activity

What is the dual isotope procedure for MPI imaging?

2.5mCi of Tl-201 @ rest

• wait 10-15min before imaging

22-25mCi of Tc-based agent @ stress

• wait time varies btween 30-60min (depending on isotope)

What is the advantage of the Dual isotope method?

advantage of combining unique characteristic of Tl to assess myocardial viability

Name three PET MPI Radiopharmaceuticals

Rubidium-82 chloride

Oxygen-15 water

Nitrogen-13 ammonia

Which PET MPI radiopharmaceutical is not cyclotron produced?

rubidium??

In PET MPI Interpretation, what indicates Ischemia?

A defect on stress with normal rest

In PET MPI Interpretation, what indicates MI?

A defect on both stress and rest

For an MPI test to be “adequate”, patients should achieve at least ____of their maximum HR

85%

How is a pts 85% of their max HR calculated?

(220-patients age) x .85 =

Exercise is limited to a HR of 120-130/min for which patients?

pts who had recent MI

When using the exercise protocol for pts who had a recent MI, their max heart rate should be limited to:

120-130/min

What is the target HR for a 50yr male pt?

139

[(220-50) x .85 = 139 bpm]

At what radiation limit does the treadmill need to be shut down?

>2mR/hr

Name three Coronary Vasodilating Agents, including their chemical name.

Dipyridamole (Persantine)

Adenosine (Adenoscan, Adenocard)

Regadenoson (Lexiscan)

What is the biological half life of Dipyridamole (Persantine)?

hours

What is the biological half life of Adenosine (Adenoscan, Adenocard)?

10 sec

What is the biological half life of Regadenoson (Lexiscan)?

30min

Which coronary vasodialator(s) is preferred, and why?

Adenosine or regadenoson bc they have short biological half life compared to dipyridamole

What type of agent is dobutamine (dobutrex)?

Cardiac Positive Inotropic and Chronotropic Agent

When would Dobutamine typically be used instead of a coronary vasodilating agent?

When a patient has asthma, or is actively wheezing

What are some alternative names for Gated Blood Pool Imaging?

MUGA (multigated blood pool acquisition)

RVG (radionuclide ventriculography)

ERNA or RNA (equilibrium radionuclide angiography)

Name the 5 indications for a MUGA study

Assessment of cardiac function in chemotherapy patients

detection or assessment of CAD

MI

detection or assessment of CHF

Evaluation of function in patients with valvular disease

What are the two most common indications for RVG’s/MUGA’s/gated blood pool imaging?

evaluate ventricular function and EF in pts having chemotherapy

What result from a RVG study would be an indication to discontinue chemo?

If there is a drop of EF of >15%

What are the three methods for tagging Tc-99m labeled RBC's, and their labeling efficiency percentage?

In vitro (95%)

Modified (90%)

In vivo (85%)

T/F: before a MUGA procedure, An ECG rhythm strip should be obtained before injection. And why or why not?

true

Rapid a-fib or frequent PVC’s are a contraindication to the study.

What are the absolute contraindications for MUGA studies?

Rapid atrial fibrillation or frequent PVC’s

If there is a Tall P or T-wave (double gating) on the ECG, what can be done to troubleshoot?

move leg lead closer to heart

What can be done if the R-waves are inverted?

leads are criss crossed (?)

How can you increase the R-wave height on an ECG strip?

move black and red leads closer

During a gated study, 24 images per cardiac cycle are obtained. What is the length of time per image?

a)3.8 msec

b)38 msec

c)4.1 msec

d)41 msec

38 msec

What is the Ejection Fraction Formula?

EF = (Net diastolic counts - net systolic counts) / net diastolic counts

x 100

Calculate EF if ED = 90,400, and ES = 40,000

55.7%

What is the normal range for LVEF?

55-75%

What is the normal range for RVEF?

>40%

What level of decrease in LVEF in Chemotherapy Patients could indicate cardiotoxicity?

Decrease in LVEF below 50% or drop in LVEF of 5% or more

What is a normal range of increase for LVEF on a stress MUGA or first pass study?

Should have 5 % increase in LVEF from rest to stress 

What causes an overestimation in EF?

Too much background subtraction

What causes underestimation in EF?

Too little background

including the left atrium in the left ventricle ROI in systole

Name the four indications for a First Pass Study.

Evaluation of patients with left ventricular dysfunction

interventricular shunts

myocardial ischemia

infarction.

What are advantages of a First Pass Study?

Tracer activity is limited to one chamber at a time, making it easy to define ROI’s

background is decreased

rapidly completed.

What are the disadvantages of a first pass study?

counting statstics are low bc of count rate limitations on rountine gamma cameras

Special high-count rate capable cameras are optimal but not widely available

What radiopharmaceutical is used for a First Pass Study?

Almost any Tc-99m radiopharmaceutical (besides MAA)

Why is Tc-99m pertechnetate or Tc99m DTPA prefered for a first pass study?

bc is Rapidly excreted through the kidneys

Using a MPI Tc agent, first pass study can be followed by a ______

gated SPECT

Using Tc-99m labeled RBCs, a first pass study can be followed by a  ______

MUGA

What is visualized during a good bolus injection path on a first pass study?

sequential visualization of the superior vena cava, right atrium, right ventricle, pulmonary artery to lungs, pulmonary veins, left atrium, left ventricle, and aorta

How is Hibernating Myocardium defined?

Severely, chronically ischemic tissue that is viable but appears to be nonfunctioning and has decreased perfusion

Why is it important to identify hibernating myocardium?

Because hibernating myocardium has a high likelihood of benefiting from revascularization.

What 2 PET radio pharmaceuticals can be used for viability imaging?

Tl-201

F-18 FDG

Which PET radiopharmaceutical is considered the gold standard in Viability?

F-18 FDG

What is the TI-201 Imaging Protocol for Viability studies?

dose: 2.5-3.0mCi of Tl @ rest (no stress)

1. Imaging 10-15 minutes post injection

2. redistribution (delay) images at 3-4 hours

3. if indicated: 24-hour delay or reinjection,

If ischemic areas fill in on initial 3-4hr delay viability images using Tl-201, what is done next?

nothing - exam is complete

If ischemic areas do not fill in on initial 3-4hr delay viability images using Tl-201, what is done next?

perform 24hr delay images or reinjection protocol

How are viability images usign Tl-201 interpreted?

Tl-201 uptake on delay or after injection = viable myocardium

How is F-18 FDG produced?

cyclotron

What is the positron range of F-18 FDG?

0.3mm

What is the mechanism of localization of F-18 FDG?

metabolic trapping

What is the critical organ of F-18 FDG?

bladder

What is the SNM ideal blood glucose for viability imaging?

between120-160 mg/dl

What should be done if BS is less than 120mg/dl?

administer oral glucose

What is the Viability Imaging protocol using FDG ?

glucose, if indicated

dose: 5-15 mCi F-18 FDG

• IV inj. 45 min post glucose loading

• PET images 30-60 minutes post-injection