A review article by Jonathan Moody, PhD, Principle Scientist for INVIA Medical Imaging Solutions has been published in the September/October issue
of the Journal of Nuclear Cardiology. This article was co-authored by Drs. Lee, Ficaro, and Corbett and Murthy of the University of Michigan. It recommends
the standardization of dynamic PET acquisition, image reconstruction, and quantification protocols for enhanced precision and accuracy of myocardial
blood flow (MBF).
Entitled “Precision and accuracy of clinical quantification of myocardial blood flow by dynamic PET: a technical perspective,” the article concludes that
dynamic PET acquisition and image reconstruction methods need to be standardized so that consistent, accurate results can be routinely realized across
all cardiac PET centers regardless of whether the physicians are reviewing absolute stress MBF only or Coronary Flow Reserve. The article abstract
can be viewed on the Journal of Nuclear Cardiology (JNC) website. Full text can be viewed here
or with a JNC subscription.
*Note that the terms “CFR” [Coronary Flow Reserve] and “MFR” [Myocardial Flow Reserve] are used interchangeably. “Stress MBF” refers to the absolute Myocardial
Blood Flow at stress in Dynamic PET.
Summary of the Article:
Published: Sept/Oct 2015 in the Journal of Nuclear Cardiology
In dynamic PET studies, MBF and CFR (defined as stress MBF divided by rest MBF) both play an important role in the evaluation of Coronary Artery Disease
(CAD) and patient care.
As Dr. Venkatesh Murthy’s points out in his recent article (read the summary here
), some physicians
believe assessing just the stress MBF is sufficient, and want to limit radiation exposure to the patient and save time by eliminating the rest
scan. However, doing so can produce more variable results as MBF values are sensitive to quantification methods. If physicians come to rely on
stress studies alone, there needs to be a higher degree of standardization of quantification methods before stress-only studies can be reliably
Dr. Jonathan Moody expands upon this in his review article by pointing out the importance of all steps involved in a dynamic PET study. He states that
the clinical benefits of MBF may be more fully realized when acquisition, image reconstruction, and quantification protocols are standardized.
He reviewed six general factors that impact the accuracy of clinical MBF quantification, discusses the effects of newer technologies, and provides
specific standardization recommendations. The tracer 82Rb is commonly used for clinical MBF and CFR quantification and is the focus in this review.
6 factors that impact MBF accuracy and recommendations on how to improve them:
1. Tracer infusion and temporal sampling - Recommends standardizing tracer infusion times based on the count rate capabilities of
varying PET scanners.
2. Scatter correction – Recommends more research providing a better understanding of scatter correction with dynamic PET and how
it impacts the accuracy of clinical MBF quantification.
3. Prompt gamma correction – Recommends published clinical validation of existing prompt gamma correction methods and assessment
of its impact on MBF precision and accuracy. Until the clinical validation is published, studies should report whether or not they used correction.
4. Image reconstruction and post-filtering – New image reconstruction methods have become clinically available. A better understanding
of these newer methods and their influence on MBF quantification is necessary. Image reconstruction and post-filtering methods need to be consistent
when comparing studies.
5. Patient motion – Currently there are no clinical solutions for motion during dynamic PET, but there is progress on the development
of a correction method. Further development of a motion correction method for dynamic PET is recommended.
6. Tracer kinetic modeling – Recommends more research and the standardization of image pre-processing across all software, choosing
partial volume correction and model-based methods for consistency across studies.
MBF results may be varied across clinics due to the large number of previous-generation PET scanners being used clinically and a lack of clinical standardization
of dynamic PET acquisition and protocols.
For MBF and CFR to achieve their full clinical potential and meaningfully influence the care of patients, dynamic PET acquisition and image reconstruction
need to be standardized and clinical MBF quantification needs to be optimized so that precise, accurate results can be consistent across all cardiac
For more information on 4DM’s PET/CFR package and the quantification of Reserve and MBF, click here to contact INVIA or request a quote.