Case Study of the Month -
PET Myocardial Perfusion
This patient is a 57 year-old male, referred by a cardiologist.
Patient History
Fig. 1 — The SPECT study indicated multiple fixed perfusion defects in the anterior wall, apex and inferior wall, consistent with scar.
- This patient has known coronary artery disease (CAD), with a history of myocardial infarction, congestive heart failure, and diabetes.
- Two months prior to his PET perfusion study the patient underwent myocardial SPECT which showed multiple fixed defects consistent with scar (Figure 1, right)
- PET perfusion imaging was requested because of the suboptimal image quality of the SPECT, due to the patient's body habitus (265#), and his diabetes.
Clinical Question
Fig. 2 — The PET perfusion study is arranged as short axis (stress over rest), vertical long axis (stress over rest), and horizontal long axis (stress over rest). Note: the clear reversibility in portions of the anterior wall, apex and inferior wall.
Will the PET perfusion study confirm the fixed defects found on SPECT, or identify areas of reversibility?
PET Perfusion Findings
There was clear evidence of reversibility in the septum, apex, and anterior wall (LAD distribution), as well as the inferior wall (RCA distribution). Small areas of non-reversibility (scar) were noted in the apex and infero/lateral wall (Figure 2, right).
Treatment Change
- Prior to the PET perfusion study the patient was advised to retire and to minimize his daily activities, because of irreversible, extensive heart damage.
- Following his PET perfusion study, his cardiologist elected to proceed to catherization. He was found to have diffuse LAD and RCA disease.
- The LAD was stented and the patient was schedule for RCA stent.
Clinical Question
Under what circumstances can PET perfusion imaging offer advantages over standard myocardial SPECT?
Answer:
PET myocardial perfusion imaging has been shown to be of particular value in diabetics, obese patients, women and patients with equivocal or confusing SPECT studies.
PET Perfusion Protocol
- Rubidium-82 rest study
- Pharmacologic Stress: adenosine
- Rubidium-82 stress study
- CT attenuation
- Total time: 25 minutes
Positron Emission Tomagraphy (PET) myocardial perfusion imaging can be performed with either N-13 ammonia (cyclotron-produced) or rubidium-82 (generator-produced). Advantages of PET versus SPECT include higher spatial resolution, better attenuation correction, quantitation, true stress function analysis, reduced radiation, and higher accuracy. Good candidates for PET include: patients with suboptimal SPECT or SPECT results at odds with the clinical data, obese patients, large breasted women, and diabetics. Presently, PET perfusion studies are best performed with pharmacologic stress (e.g., adenosine, dipyridamole, or dobutamine), and can be completed on modern PET/CT systems in less than 30 minutes.
Superior Clinical Performance
"PET perfusion imaging has two technical advantages which translate into superior clinical performance over conventional SPECT imaging. First, a higher spatial resolution allows more precise localization of jeopardized myocardium. This permits easier identification of the "culprit" coronary vessel, and helps guide coronary interventions. Second, a truly effective attenuation correction eliminates imaging artifacts due to overlying soft tissue. This reduces the frequency of false positive studies, which can lead to unnecessary cardiac catherizations."
Andrew Van Tosh, MD
Beth Israel Medical Center
This case study is courtesy of Dr. Michael Kipper
Pacific Imaging and Treatment Center, San Diego, California
