A breast attenuation artifact is an abnormality seen on images taken during a cardiac stress test. This artifact is generally a benign finding and is caused by the shadow cast by breast tissue over the cardiac tissue being tested. Attenuation artifact errors are the most common errors seen during cardiac imaging tests.
During single-photon emission computed tomography, or SPECT, a patient lies in different positions to gain images of the heart from all directions. Photons emitted during the test pass through various tissues that surround the heart, including bone, breast tissue and the lungs. Photon attenuation can be affected by the tracer injected during the test, which aids in visualization on imaging. Attenuation is also affected by a person's body size, camera position during imaging and the depth at which the heart is located within the thorax.
In SPECT imaging, if the breast tissue shadow is superimposed over the heart, it may appear that anterior ischemia is present within the heart, but this is generally a false-positive image. A false-positive image, unfortunately, may lead to unnecessary testing, such as angiography and cardiac catheterization. A woman with repeated false-positive tests may still have true heart abnormalities, but attenuation due to breast tissue needs to be ruled out first in order to make the correct diagnosis.