82 Rb-PET MPQ: Do normal values exist?
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Rb-PET MPQ: Do normal values exist?
Sergey V. Nesterov, MD, PhD, PMP, PgMP,a,b and Juhani M. Knuuti, MD, PhDa a b
Turku PET Centre, University of Turku, Turku, Finland Institute of Evolutionary Physiology and Biochemistry RAS, St. Petersburg, Russia
Received Aug 21, 2020; accepted Aug 21, 2020 doi:10.1007/s12350-020-02362-3
See related article, https://doi.org/10.10 07/s12350-020-02264-4. Introducing their recent study, Freitag et al.1 state that ‘‘two questions remain unanswered for quantitative 82Rb-PET: (1) which are the normal values of sMBF and rMBF? And (2) which quantitative parameter is the most accurate to allow for a precise diagnosis of CAD (sMBF or myocardial flow reserve [MFR])?’’ To get an answer, they performed a study of 357 patients that underwent 82Rb-PET/CT and integrated coronary CT angiography (CCTA). Based on the finding in CCTA, the patients were classified as (a) normal (no stenosis, N = 153), (b) with non-obstructive coronary artery disease (CAD) (\ 50%, N = 99), and (c) with obstructive CAD (C 50%, N = 105). Not surprisingly, the global stress myocardial blood flow (sMBF) (and myocardial flow reserve, MFR) were higher 3.61 ± 0.71 mLming (3.08 ± 0.84) in normal patients than in patients with obstructive CAD 3.04 ± 0.77 mLming (2.68 ± 0.79). Yet they turned out to be not different compared to patients with nonobstructive CAD (3.43 ± 0.69 mLming and 2.99 ± 0.82). Also, sMBF was more accurate than MFR in identifying both ischemia and severe ischemia. The authors conclude that the provided ‘‘normal quantitative values’’—3.5 mLgmin—which they called the ‘‘optimal threshold,’’ can help rule out myocardial ischemia. Also, they suggest that a resting scan could be omitted in patients with sMBF values. We will not hover over the question of favoring sMBF over MFR: the same has been shown for 15O-
Reprint requests: Sergey V. Nesterov, MD, PhD, PMP, PgMP, Turku PET Centre, University of Turku, Turku, Finland; [email protected] J Nucl Cardiol 1071-3581/$34.00 Copyright Ó 2020 American Society of Nuclear Cardiology.
water,2,3 and taking into account the reduced radioactive burden, it does seem an advantageous option. However, we would like to draw attention to the question of ‘‘normal values.’’ Naturally, practicing physicians do crave the certainty that a number—a cutoff value here— promises to provide. The authors used CT coronary angiography to rule out CAD in patients with suspected ischemic heart disease. Therefore, the selection of the patients can be assumed to represent the population that is typically entering diagnostic testing for suspected obstructive CAD with the caveat that potential microvascular disease remains undetected. The findings of the current study are not very different from the previous small study by Prior et al.,4 where the normal sMBF was 3.82 ± 1.21 mLming (9% higher than the Freitags), in a younger population (age—30 ± 13 years). On the other hand, a more extensive study (N = 241) by Johnson and Gould5 on even the younger population (age—28 ± 5 years
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