What does this mean: myocardial perfusion imaging adversely affected by soft breast tissue attenuation

Imaging Artifact: Soft tissue attenuation in the breast is a common artifact in myocardial perfusion imaging. It may artifactually affect the depiction of activity in the myocardial wall. If perfusion defect is seen on both stress & rest images and normal wall motion & wall thickness shown on ecg-gated spect then apparent fixed defect is an artifact of attenuation instead of an area of myocardial infarction.