Although currently in limited supply due to the location proximity needed for conventional cyclotrons, 13N-ammonia is well understood and recognized as a gold standard for cardiac perfusion imaging. It is used at prominent cardiac programs at Mayo Clinic, Brigham & Women’s, Massachusetts General, UCLA, and the University of Texas.
N-13 AMMONIA CARDIAC PET RADIOPHARMACEUTICAL
N-13 Ammonia imaging offers many advantages over the dominant 99mTc-SPECT radiopharmaceutical, as well as another cardiac PET tracer, 82Rb-chloride. The table below highlights the differences between N-13 Ammonia and 82Rb-chloride.
N-13 Ammonia, due to the low mean positron length associated before the proton annihilates, has been shown to provide clearer images potentially allowing for an improved diagnostic certainty. The following PET scan images is an example 1N-13 Ammonia compared to 82Rb-chloride.
|Half life (min)||9.97||1.27|
|Positron energy (MeV)||1.19||95.5%|
|Positron range (mm)||0.57||2.60|
|System Resolution (mm)||6.03-6.15||6.54-8.56|
|Effective radiation dose per study (msv)||1.5||3.8|
|Raw material||High Purity O-16 water and methane gas||Sr-82/Sr-85|
|Physiological properties||13N-ammonia||Rest flow 82Rb-chloride|
Tracer Comparison Example Images
Abnormal N-13 Ammonia PET from a patient with a 90% right coronary artery stenosis
Abnormal 82Rb PET from a patient with a 90% Proximal left anterior descending artery stenosis
Natazota et al. “Myocardical perfusion imaging with PET” Imaging Med. 2013 February 1; 5(1): 35-46.
Example Rest/Stress Protocol
Protocols for 13N-ammonia imaging can be as efficient as 82Rb-chloride if a low dose / high dose protocol is used.
Delay of at least 18 min between injection. This is necessary in order to insure rest contamination of less than 12%, which is consistent with a conventional rest/stress 99mTc myocardial perfusion study protocol.
1 min CT
Rest 9 mCi
Stress 20 mCi 13N
1 min CT
N-13 TREADMILL PET
The longer half-life of N-13 A-ammonia can allow for patients to be treadmill exercised as an alternative to pharmacologic stress. This provides additional imaging options for your cardiac PET program.
Recent studies utilizing treadmill N-13 A-ammonia stress testing have demonstrated:
- Reliable diagnostic accuracy and image quality in obese and non-obese patients. 1
- Annual event rate is consistent with previously published SPECT and PET data. 2
- Produces larger, more severe defects compared to dipyridamole stress. 3
References & Articles
- Aggarwal NR, Drozdova A, Askew JW, Kemp BJ, Chareonthaitawee P. Feasibility and diagnostic accuracy of exercise treadmill nitrogen-N-13 Ammonia PET myocardial perfusion imaging of obese patients. Journal of Nuclear Cardiology. 2015 Dec 1;22(6):1273-80.
- Chow BJ, Al Shammeri OM, Beanlands RS, Chen L, DaSilva J, Ruddy TD. Prognostic value of treadmill exercise and dobutamine stress positron emission tomography. Canadian Journal of Cardiology. 2009 Jul 1;25(7):e220-4.
- Chow BJ, Beanlands RS, Lee A, DaSilva JN, Alkahtani A, Ruddy TD. Treadmill exercise produces larger perfusion defects than dipyridamole stress N-13 ammonia positron emission tomography. Journal of the American College of Cardiology. 2006 Jan 17;47(2):411-6.
THE ICONIC ION-12 SC
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We’re confident that our cardiac PET partnership N-13 Ammonia program and/or 18F solution will help grow your practice or service line. We look forward to hearing from you.