A four year study performed by University of Michigan Physician, Assistant Professor of Medicine and Radiology, and 4DM user, Dr. Venkatesh Murthy
has been published in the December 2014 issue of the Journal of Nuclear Medicine comparing methods of quantifying coronary flow reserve when using
Rubidium PET. This extensive study utilized Corridor4DM to perform the PET/CFR quantification, and features co-authors including Drs. Lee, Moody, and
Ficaro of INVIA.
Titled “Comparison and Prognostic Validation of Multiple Methods of Quantification of Myocardial Blood Flow with 82Rb PET,” the abstract can be viewed
on the Journal of Nuclear Medicine (JNM) website
Full Text can be viewed with either a JNM subscription or small fee. The conclusion indicated that, until a standardization of flow models, acquisition
protocols, and reconstruction parameters are developed, the Reserve calculation should be preferred over Stress-only Myocardial Blood Flow when assessing
*Note that the terms “CFR” [Coronary Flow Reserve], “Reserve,” and “MFR” [Myocardial Flow Reserve] are used interchangeably.
A summary of the article follows:
1. Published Dec. 01, 2014 in the Journal of Nuclear Medicine
2. Methods - Looked at Reserve and Myocardial Blood Flow (MBF) comparison between different Flow Models which included 1) varying
the Blood Sampling to be Factor Analysis, Region of Interest, or Factor Analysis-Hybrid, and 2) varying the K1-MBF Relation to be each of the 5 validated extraction models for Rb-82 (eg: Yoshida, Lortie, etc). 2,783 consecutive patients were studied from 2006
to 2010: Rb-82, rest-stress, cardiac PET.
a. Reserve calculations (Stress MBF divided by Rest MBF) are consistent and accurate in assessing risk regardless of Blood Sampling
and K1-MBF Relation used. This means that no matter what hospital assesses your Reserve, and no matter what flow models they use, the patient’s
diagnosis will most likely be consistent.
b. Stress MBF calculations alone (just looking at stress flow quantification without any comparison to rest flow) were highly variable
depending on the Blood Sampling and K1-MBF Relation (although less so when varying the K1-MBF Relation). This means that, depending on the hospital
and the flow models they used, the values of Stress MBF may vary significantly and there is no consistent way to compare to other risk assessments
unless they also used the exact same flow models.
4. Conclusion - Some physicians think looking at the stress images alone when assessing absolute flow is sufficient, and want to limit the radiation
exposure to the patient by eliminating the rest scan. However, doing so can produce inconsistent results as stress MBF values are highly dependent
upon technical aspects such as the flow models the physician selects. If a physician is going to look at stress imaging alone, there needs to be
a high-degree of standardization, including choice of flow models, acquisition protocols, and reconstruction parameters used for assessment. Until
such time, stress-only imaging for cardiac PET [MBF] should not be the only point of reference. Reserve calculations should be
preferred in assessing risk.
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.