Case Author(s): Christine Fisher, M.D. and Robert Gropler, M.D. , 04/22/97 . Rating: #D3, #Q4

Diagnosis: Apparent inferior wall myocardial perfusion defect due to back-projection artifact.

Brief history:

64 yr old female with chest pain, new onset atrial fibrillation


Rest (Thallium-201) myocardial images on the bottom and Stress (Tc-99m sestamibi) myocardial perfusion images on the top

View main image(mi) in a separate image viewer

View second image(mi). Stress images repeated 3 hours later

Full history/Diagnosis is available below

Diagnosis: Apparent inferior wall myocardial perfusion defect due to back-projection artifact.

Full history:

64 year old female presents with chest pain and new onset atrial fibrillation. Her cardiac risk factors include hypertension and obesity. She underwent an adenosine myocardial perfusion study and did not experience chest pain or ECG changes during the infusion of adenosine.


2.6 mCi Tl-201 chloride i.v.; 21.0 mCi Tc-99m sestamibi i.v.


Initial stress images show significant hepatic and bowel uptake of Tc-99m sestamibi as well as an apparent inferior wall perfusion defect. Repeat (3-hour delayed) Tc-99m sestamibi images show a marked reduction in hepatic and bowel activity and the inferior wall perfusion defect is no longer seen.


Significant uptake in the liver and bowel on the initial stress images caused a back-projection error to adjacent myocardium, in this case the inferior wall. The error imposed is a decrease in activity causing an apparent inferior perfusion abnormality. The inferior wall is the common site for this abnormality. This error is most pronounced when activity in the liver or bowel is at least as high as that in the myocardium and that the dome of the liver or the loop bowel is at the level of the inferior wall. Repeat imaging in three hours allowed liver and bowel clearance of Tc-99 sestamibi and therefore no interference to myocardial imaging. This manuever works well because sestamibi does not significantly redistribute from myocardium.

Major teaching point(s):

1. Inferior wall defects are common with newer Tc-99m agents such as sestamibi or tetrofosmin due to the liver excretion of these tracers.

2. These defects can mimic inferior wall myocardial ischemia.

3. Repeat imaging at 3-4 hrs can help differentiate between this artifact and real ischemia.

ACR Codes and Keywords:

References and General Discussion of Myocardial Imaging (Anatomic field:Heart and Great Vessels, Category:Other(Artifact))

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Case number: mi010

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