![]() ![]() Abdominal protuberance (eg, ascites or peritoneal dialysis).ĭiaphragmatic attenuation is more common in the following settings: Diaphragmatic attenuation is estimated to occur in up to 25 percent of myocardial perfusion studies. This artifact results in a perfusion defect in the inferior segments which generally correspond to the posterior descending coronary artery (PDA) territory. Attenuation due to the patient's arm not being raised overhead (on a supine or prone study)ĭiaphragmatic attenuation - Attenuation from the left hemidiaphragm can reduce photon counts in the inferior wall.However, if the body part causing attenuation (eg, breast, diaphragm, arm, etc) changes its position between stress and rest imaging, the resultant soft tissue attenuation may produce a reversible perfusion defect mimicking myocardial ischemia.Īlthough there are multiple sources of attenuation artifact, our discussion will focus on the following common sources in detail : This is generally interpreted as a fixed perfusion abnormality, and may be difficult to differentiate from myocardial scar or infarction. Fixed anatomic structures generally will produce the same attenuation artifact both on stress and rest images. SOURCES OF ATTENUATION ARTIFACT - Soft tissue attenuation may result in an apparent focal fixed or reversible perfusion abnormality or defect. (See "Overview of stress radionuclide myocardial perfusion imaging".) The clinical uses of SPECT rMPI are discussed in detail separately. Sources of attenuation with SPECT rMPI and methods to interpret or eliminate attenuation artifacts will be discussed here. Choice of radioactive tracer (eg, 99m-technetium, thallium-201) and activity of the radioisotope.Photon attenuation and the resultant artifacts are affected by several factors, including: Fixed anatomic structures generally will produce the same attenuation artifact both on stress and rest imaging. Soft tissue attenuation may result in an apparent fixed or reversible perfusion abnormality or defect. Since the heart is surrounded by tissues of varying densities (eg, bone, lungs, and breast), radionuclide imaging of the thorax results in nonuniform myocardial photon activity due to attenuation from these intervening structures. Photon attenuation occurs as photon beams experience loss of energy while traversing tissue. Soft tissue attenuation is one of the more common causes of rMPI artifacts. Interpretation of rMPI requires knowledge of common patterns and causes of artifacts. These artifacts reduce image quality and increase the risk of misinterpretation of the results. However, the full clinical potential of rMPI has not been realized due to numerous factors that result in image artifacts. INTRODUCTION - The value of radionuclide myocardial perfusion imaging (rMPI) with single-photon emission computed tomography (SPECT) for the diagnosis and risk stratification of coronary artery disease (CAD) is well-established. ![]()
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