A fifty-one year old female patient was referred for SPECT Imaging due to intermittent chest pain. The symptoms were considered atypical and not accelerating. The patient was obese (BMI 49.8), and had several risk factors including diabetes, hypertension and hyperlipidemia.
The patient underwent a two-day pharmacologic rest/stress SPECT study (15 mSv) with no symptoms or ECG changes. The SPECT rest and stress study images are shown in Figure A.
The SPECT study demonstrated a medium sized and moderate in intensity anterior and anterolateral perfusion abnormality which was completely reversible. Ventricular function revealed normal wall motion globally as well as in the area of the perfusion abnormality (EF 59%).
These findings were consistent with single vessel ischemia. However, due to the patient’s body habitus, the etiology of attenuation artifact was also possible. The patient was referred for a Cardiac PET perfusion study.
The patient underwent a pharmacologic rest/stress PET study (5 mSv) with no symptoms or ECG changes. The SPECT rest and stress study images are shown in Figure A above.
The PET study demonstrated completely normal perfusion and function with a similar ejection fraction (58%) to the SPECT study Figure B.
This study illustrates the value of Cardiac PET imaging in patients with previous SPECT studies in which attenuation artifact is a consideration. Although less common, reversible perfusion abnormalities can be related to attenuation artifact, as was the situation in this case. Several studies have demonstrated higher diagnostic accuracy for PET over SPECT, both in terms of sensitivity, or in this case specificity (Bateman, Parker, and McArdle). Of note, radiation exposure of the PET study was 1/3 that of the SPECT.