Clinical Case Study•Cardiac PET/CT

This Is Why We Do Cardiac PET: Comparison of SPECT and PET in the Same Patient

Arun Agarwal, MD  ·  Simran Agarwala  ·  Sunil Selvin, CNMT  ·  Kenneth Merkatz, MD  ·  Ricardo Avila-Gomez, CNMTStarling Physicians — Wethersfield, Connecticut  ·  Molecular Imaging Services, Newark, DE

SPECT vs PETRubidium-82 PET/CTLAD MBFR 1.8680% proximal LAD

The bottom lineA normal exercise SPECT study did not explain this patient’s ongoing angina. Cardiac PET performed in the same patient revealed a large, completely reversible anterior defect with abnormal LAD flow reserve, and catheterization confirmed an 80% proximal LAD stenosis treated with a stent.

Case history

  • 60-year-old male with a history of exertional chest pain, plus hypertension, diabetes, and hyperlipidemia
  • Underwent exercise SPECT: no symptoms, 1–2 mm ST-segment depression, achieved greater than 85% of maximum predicted heart rate
  • SPECT study read as normal with normal left ventricular ejection fraction
  • Because symptoms continued, pharmacologic PET with myocardial blood flow was ordered

PET protocol

  • Stress agent: regadenoson
  • Isotope: Rubidium-82, 39.7 mCi at rest and 39.8 mCi at stress
  • Camera: GE PET/CT Discovery DSTE; flow quantified with Cedars software
  • Stress ECG showed 1.0 mm ST-segment depression in V4, V5, and V6, with shortness of breath and chest pain
  • Heart rate 95 to 123 BPM; blood pressure 153/88 at rest, 147/67 at stress
  • Quality control: good registration at rest and stress, no motion artifact, normal blood-flow QC

Myocardial blood flow reserve

Global reserve was preserved, but the LAD territory was abnormal in isolation — consistent with single-vessel ischemia.

1.86LAD

3.67LCx

3.35RCA

2.39Global

Interpretation and outcome

PET perfusion showed a large anterior, anteroseptal, and apical defect extending from apex to base, moderate to severe in intensity and completely reversible. The TID ratio of 1.41 was abnormal and consistent with ischemia.

Gated imaging demonstrated a reversible anterior wall motion abnormality with ejection fraction falling from 78% at rest to 68% at stress. Global flow reserve was normal at 2.39, but the LAD territory was abnormal at 1.86 — a pattern consistent with single-vessel ischemia rather than diffuse disease.

Catheterization confirmed an 80% proximal LAD stenosis with normal circumflex and right coronary arteries. A stent was placed successfully in the LAD, and the patient had symptom relief.

Teaching points

  • PET diagnostic accuracy is significantly higher than SPECT
  • When symptoms continue after a normal SPECT study, PET imaging may be useful
  • Myocardial blood flow can help localize the diseased vessel, as it did in this patient
  • For higher-risk patients, PET is the preferred modality in part because of better diagnostic accuracy

View the full case presentationComplete slide deck with side-by-side SPECT and PET perfusion images, gated data, Cedars flow results, and catheterization images.

View Case Study (PDF)

References
1. Bateman TM, Al-Mallah MH, Alnabelsi TS, et al. Clinical indications for positron emission tomography myocardial perfusion imaging and myocardial blood flow quantification: an American Society of Nuclear Cardiology position statement. J Nucl Cardiol.
2. Parker MW, Iskandar A, Limone B, et al. Diagnostic accuracy of cardiac positron emission tomography versus single photon emission computed tomography for coronary artery disease: a bivariate meta-analysis. Circ Cardiovasc Imaging. 2012;5:700-707.
3. McArdle BA, Dowsley TF, deKemp RA, Wells GA, Beanlands RS. Does rubidium-82 PET have superior accuracy to SPECT perfusion imaging for the diagnosis of obstructive coronary disease? A systematic review and meta-analysis. J Am Coll Cardiol. 2012;60:1828-1837.

Presented in collaboration with the American Society of Nuclear Cardiology. Case images are not for diagnostic use. This material is intended for healthcare professionals and is educational in nature; it is not clinical advice for any individual patient.

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