Because of its intrinsic quantitative properties, PET permits measurement o
f myocardial perfusion and metabolism in absolute terms (i.e., mL/g/min), H
owever, quantification has been limited by errors produced in image acquisi
tion, selection of regions of interest, and data analysis. The goal of this
study was to evaluate a newly developed, novel, wavelet-based noise-reduct
ion approach that can objectively extract biologic signals hidden within dy
namic PET data. Methods: Quantification of myocardial perfusion using dynam
ic PET imaging with Rb-82, (H2O)-O-15, and (NH3)-N-13 was selected to evalu
ate the effects of the wavelet-based noise-reduction protocol. Dynamic PET
data were fitted to appropriate mathematic models before and after wavelet-
based noise reduction to get flow estimates. Time-activity curves, precisio
n, accuracy, and differentiating capacity derived from the wavelet protocol
were compared with those obtained from unmodified data processing, A total
of 84 human studies was analyzed, including 43 at rest (18 Rb-82 scans, 18
(H2O)-O-15 scans, and 7 (NH3)-N-13 scans) and 41 after coronary hyperemia
with dipyridamole (17 Rb-82 scans, 17 (H2O)-O-15 scans, and 7 (NH3)-N-13 sc
ans). Results: For every tracer tested under all conditions, the wavelet me
thod improved the shape of blood and tissue time-activity curves, increased
estimate-to-error ratios, and maintained fidelity of flow in regions as sm
all as 0.85 cm(3). It also improved the accuracy of flow estimates derived
from Rb-82 to the level of that achieved with H(2)(15)0, which was not affe
cted markedly by the wavelet process. In studies of patients with coronary
disease, regional heterogeneity of myocardial perfusion was preserved and f
low estimates in infarcted regions were differentiated more easily from nor
mal regions. Conclusion: The wavelet-based noise-reduction method effective
ly and objectively extracted tracer time-activity curves from data with low
signal-to-noise ratios and improved the accuracy and precision of measurem
ents with all tracer techniques studied. The approach should be generalizab
le to other image modalities such as functional MRI and CT and, therefore,
improve the ability to quantify dynamic physiologic processes.