Myocardial perfusion SPECT imaging (short axis, vertical long axis, horizontal long axis slices on the left; polor map view on the right) shows a reversible perfusion defect in the mid-distal anterior left ventricle wall.  This defect present only on stress images would typically indicate stress-induced ischemia (i.e. a positive stress test).

However, notice on the SPECT processing images that there is attenuation of photons in the heart due to breast tissue, seen as a “shadow” over the heart in the lateral view of the raw data. Also notice the breast is in differing positions on stress vs. rest images.

This study was interpreted as varying breast attenuation, without evidence for ischemia or infarction.

SPECT data alone tells us there is varying breast attenuation, best appreciated on the raw data views. But correlating with the SPECT/CT fusion images confirms the differing position of the breast. Furthermore when this data is processed using CT attenuation correction, the reversible anterior defect is no longer seen:

Attenuation from breast tissue occurs in a significant proportion of women undergoing myocardial perfusion imaging, usually resulting in a fixed (i.e. present on both rest and stress) perfusion defect in the anterior or anterolateral walls. Attentuation correction methods have been shown to result in a significantly higher normalcy rate without a decrease in sensitivity.

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Hendel RC, et al. Circulation 1999;99:2742-9.