Case Author(s): Mukarram A. Baig, MD and Jerold Wallis, MD , 10/21/96 . Rating: #D3, #Q4

Diagnosis: Myocardial artifact

Brief history:

Substernal chest pain.

Images:

Vertical long axis (left)and quality control images(right); the quality control images consist of a sinogram and selective linogram.

Top frames represent stress sestamibi images, and resting thallium imaging in lower frames

View main image(mi) in a separate image viewer

View second image(mi). Selected stress projection images are also available, if desired.

Full history/Diagnosis is available below

Diagnosis: Myocardial artifact

Full history:

Patient is a 46 year old female with chest pain who had difficulty lying still during the examination. There is no history of prior infarction.

Radiopharmaceutical:

2.50 mCi Tl-201 chloride and 20.20 mCi Tc-99m sestamibi i.v.

Findings:

There is an apparent reversible perfusion abnormality in the inferior wall, suggesting inferior ischemia.

However, there is a "break" or discontinuity in the stress sinogram at the midpoint in the image, and there is moderate up/down motion of the cardiac activity (the horizontal white band) on the linogram. On review of the cine of the projection frames, these corresponded to sites of patient movement.

Followup:

Stress Sestamibi images were repeated again within 4 hours of initial injection, as motion artifact was felt to be the reason for the defect initially noted. The slow washout rate of Sestamibi permits reacquisition of the stress images within a few hours with minimal loss in image quality.

The repeat stress images show the perfusion to the inferior wall to be much better than on the initial stress images. The degree of decrease in the inferior wall is now the same on stress and rest images, and is most consistent with diaphragmatic attenuation.

View followup image(mi). Repeat stress images at 4 hours post initial injection, after re-emphasizing to the patient the importance of lying still during image acquisition.

Major teaching point(s):

Patient motion can cause apparent reversible perfusion abnormalities.

Review of the projections for patient motion is critical, and can be done either by inspection of the projection data in cine format or by use of sinogram and linogram images.

The slow washout rate of Sestamibi permits reacquisition of the stress images within a few hours with minimal loss in image quality.

Differential Diagnosis List

Alternate possibilities include inferior wall artifact from intense hepatic uptake of tracer. This reconstruction artifact most commonly occurs with pharmocologic stress (vasodilator) imaging of the Tc-99m perfusion agents, when imaging is performed soon after injection. Delayed imaging allows greater clearance of hepatic activity, reducing the artifact. This artifact is more severe when reconstruction of 180-degree acquisition is performed than when full 360-degree data is utilized.

However, inspection of the projection images shown above demonstrate the liver to have a similar degree of activity as does the heart. If the "hot liver" artifact were present, the liver would typically have significantly more activity than the heart on anterior projection images.

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: mi009

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