CARDIAC PET OVERVIEW

Cardiac Positron Emission Tomography is emerging as the preferred test for the diagnosis of coronary artery disease (CAD). Despite the clear majority of nuclear cardiology procedures being performed on Single Photon Emission Computed Tomography (SPECT) imaging devices, there are several advantages of PET over SPECT: lower radiation dose to the patient radiation, improved tracer kinetics, well established attenuation correction, coincidence detection of emitted events, and the ability to perform routine accurate coronary blood flow measurements.

These advantages correlate with improvements in procedure accuracy and sensitivity compared to SPECT, particularly for heavier patients, where breast, chest wall, and diaphragmatic attenuation interfere with conventional SPECT.

SUPERIOR DIAGNOSTIC ACCURACY

13N-ammonia cardiac PET imaging with coronary flow reserve (CFR) provides high spatial and contrast resolution images. The high-resolution PET detectors optimize the low kinetic energy of 13N-ammonia producing sharp myocardial perfusion images. The statistically high-count 13N-ammonia images of the myocardium are a result of the rapid clearance from blood pool, high first-pass extraction, high retention in the myocardium, and a relatively long physical half-life. 13N-ammonia consistently produces high-quality diagnostic studies regardless of patient size or gender.

Sensitivity Specificity Positive
predictive
value
Negative
Predictive
value
Accuracy
13N-ammonia MPI
PET/CT with 1
96 80 93 89 92
99mTc MPI CZT SPECT with 2 87 67 92 53 83

POWERFUL PROGNOSTIC PREDICTOR

13N-ammonia with CFR is a strong predictor of patient outcomes. CFR offers improved risk stratification and has proven to be an independent predictor of adverse outcomes. The results of one study on the long-term prognostic value of 13N-ammonia with CFR demonstrated that an abnormal CFR, regardless of normal or abnormal perfusion images, was associated with higher adverse cardiac events. Conversely, a normal perfusion along with a normal CFR suggested a 3-year “warranty” period. 3

Annual Event Rate 3

PATIENT SAFETY

13N-ammonia offers the lowest radiation dose to the patient compared to all other SPECT and PET myocardial perfusion radiopharmaceuticals. High sensitivity PET and PET/CT scanners with 3D imaging capabilities allow for half-dose protocols and therefore can routinely provide a complete 13N-ammonia rest/stress CFR study with as little as 1 mSv. or less radiation exposure to the patient. 4

Sensitivity Specificity Positive
predictive
value
Negative
Predictive
value
201TI/ 99mTc-SPECT 29.3 0.5 30.3
Two-day 99mTc-SPECT 12.8-15.7 0.5 13.8-16.7
One-day 99mTc-SPECT 9.9-11.4 0.5 10.9-12.4
Stress-only 99mTc-SPECT 7.1-8.0 0.5 8.1-9.0
82Rb PET (2D) 3.7 0.5 4.2
13N-ammonia (2D) 2.2 0.5 2.7

COST EFFECTIVE

13N-ammonia with CFR provides significant value to the overall management of coronary artery disease (CAD). 13N-ammonia with CFR reduces unnecessary diagnostic procedures and can provide direction for both interventional and medical therapies. A study utilizing 13N-ammonia with CFR demonstrated that the 13N-ammonia CFR results had a direct impact on patient management in 78% of the patients while reducing the overall cost of managing coronary artery disease, even with an increase in the diagnostic imaging cost attributed to the 13N-ammonia PET/CT study. 6

Patient Management 6

References & Articles

References

  1. Gould KL, Lipscomb K, Hamilton GW. Physiologic basis for assessing critical coronary stenosis: instantaneous flow response and regional distribution during coronary hyperemia as measures of coronary flow reserve. The American journal of cardiology. 1974 Jan 31;33(1):87-94
  2. Gould KL, Schelbert HR, Phelps ME, Hoffman EJ. Noninvasive assessment of coronary stenoses with myocardial perfusion imaging during pharmacologic coronary vasodilatation: V. Detection of 47 percent diameter coronary stenosis with intravenous nitrogen-13 ammonia and emission-computed tomography in intact dogs. The American journal of cardiology. 1979 Feb 1;43(2):200-8.
  3. Gould KL. Assessing progression or regression of CAD: the role of perfusion imaging. Journal of Nuclear Cardiology. 2005 Nov 1;12(6):625-38.
  4. Gould KL. Cardiac positron emission tomography. In: Willerson JT, Cohn JN, Wellens HJJ, Holmes DR, editors. Cardiovascular Medicine. 3rd edition. London, United Kingdom: Springer, 2007:855-69.
  5. Johnson NP, Gould KL. Physiological basis for angina and ST-segment change: PET-verified thresholds of quantitative stress myocardial perfusion and coronary flow reserve. JACC: Cardiovascular Imaging. 2011 Sep 30;4(9):990-8.

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Learn how coronary flow reserve is a key clinical application and diagnostic tool.

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