Dual Radionuclide Stress Test

[Mark How <mhow@stanford.edu>]

Hello,

A dual radionuclide stress test is done in nuclear medicine to assess 

coronary artery disease. Typically, a fasting patient is injected with 3.5 

mCi of Tl-201 at rest and the heart is imaged with a SPECT camera 

acquisition (patient lies on his/her back on an imaging couch and a camera 

moves in a 180 degree arc over the chest). If the clinic has a dual or 

triple head camera, the amount of imaging time is reduced by half or more. 

Next, the patient will be set up for a treadmill test (if the patient can 

do one, a pharmaceutical stress test can be done otherwise). The set up 

includes a 12 lead electrocardiogram monitoring, and an intravenous line 

started in one arm. The patient will exercise on a treadmill with 

increasing effort and at the peak of exercise, a dosage of about 25 mCi of 

Tc-99m labeled radiopharmaceutical (e.g., Sestamibi) will be injected into 

the intravenous line. The patient will exercise another minute. Then the 

patient recovers and then after a delay, will be imaged using a SPECT 

camera. Three EKG leads will be attached to the patient for this imaging 

portion so that a gated picture of the heart may be acquired. Thsi allows 

the wall motion of the heart to be studied, and an ejection fraction 

calculated (volume of blood being pumped out of the left ventricle versus 

volume of blood in the ventricle). The Thallium image at rest will display 

the perfusion of the heart at rest. The Tc-99m images will display 

perfusion of the heart at stress and supply the functional information 

described above as well.

The Tl-201 will redistribute over time so a delayed image (4 hours or 24 

hours) may be made to assess the severity of coronary artery disease. For 

example, a narrowed vessel may still supply some perfusion that may not be 

visualized on the immediate rest image. Also viable myocardium may take up 

Tl-201 from a diminished supply and may accumulate enough to be visualized 

on delayed imaging. The Tc-99m pharmaceuticals do not redistribute.



Hope this helps.

Regards,

Mark



Mark How



Senior Health Physicist

Stanford University Health Physics

480 Oak Road

Mail Stop 8006

Stanford, CA 94305

650/725-1407 voice

650/723-0632 fax

mhow@stanford.edu



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