Sc. Moore et al., Evaluation of scatter compensation methods by their effects on parameter estimation from SPECT projections, MED PHYS, 28(2), 2001, pp. 278-287
Citations number
39
Categorie Soggetti
Radiology ,Nuclear Medicine & Imaging","Medical Research Diagnosis & Treatment
Three algorithms for scatter compensation in Tc-99m brain single-photon emi
ssion computed tomography (SPECT) were optimized and compared on the basis
of the accuracy and precision with which lesion and background activity cou
ld be simultaneously estimated. These performance metrics are directly rela
ted to the clinically important tasks of activity quantitation and lesion d
etection, in contrast to measures based solely on the fidelity of image pix
el values. The scatter compensation algorithms were (a) the Compton-window
(CW) method with a 20% photopeak window, a 92-126 keV scatter window, and a
n optimized "k-factor," (b) the triple-energy window (TEW) method, with opt
imized widths of the photopeak window and the abutting scatter window, and
(c) a general spectral (GS) method using seventeen 4 keV windows with optim
ized energy weights. Each method was optimized by minimizing the sum of the
mean-squared errors (MSE) of the estimates of lesion and background activi
ty concentrations. The accuracy and precision of activity estimates were th
en determined for lesions of different size, location, and contrast, as wel
l as for a mon complex Bayesian estimation task in which lesion size was al
so estimated. For the TEW and GS methods, parameters optimized for the esti
mation task differed significantly from those optimized for global normaliz
ed pixel MSE. For optimal estimation, the CW bias of activity estimates was
larger and varied more (-2% to 22%) with lesion location and size than tha
t of the other methods. The magnitude of the TEW bias was less than 7% acro
ss most conditions, although its precision was worse than that of CW estima
tes. The GS method performed best, with bias generally less than 4% and the
lowest variance; its root-mean square (rms) estimation error was within a
few percent of that achievable from primary photons alone. For brain SPECT,
estimation performance with an optimized, energy-based, subtractive correc
tion may approach that of an ideal scatter-rejection procedure. (C) 2001 Am
erican Association of Physicists in Medicine.