Respective roles of scatter, attenuation, depth-dependent collimator response and finite spatial resolution in cardiac single-photon emission tomography quantitation: a Monte Carlo study
Gn. El Fakhri et al., Respective roles of scatter, attenuation, depth-dependent collimator response and finite spatial resolution in cardiac single-photon emission tomography quantitation: a Monte Carlo study, EUR J NUCL, 26(5), 1999, pp. 437-446
Citations number
33
Categorie Soggetti
Radiology ,Nuclear Medicine & Imaging","Medical Research Diagnosis & Treatment
The purpose of this study was to investigate the relative influence of scat
ter, attenuation, depth-dependent collimator response and finite spatial re
solution upon the image characteristics in cardiac single-photon emission t
omography (SPET). An acquisition of an anthropomorphic cardiac phantom was
performed together with corresponding SPET Monte Carlo simulations. The car
diac phantom and the Monte Carlo simulations were designed so that the effe
ct of scatter, attenuation, depth-dependent collimator response and finite
spatial resolution could be studied individually and in combination. The im
pact of each physical effect and of combinations of effects was studied in
terms of absolute and relative quantitative accuracy, spatial resolution an
d signal-to-noise ratio (SNR) in the resulting images. No corrections for t
hese effects were assessed. Results obtained from Monte Carlo simulations a
nd real acquisitions were in excellent agreement. Attenuation introduced ab
out 90% activity underestimation in a 10-mm-thick left ventricle wall while
finite spatial resolution alone introduced about 30% activity underestimat
ion. Scatter had a negligible impact on quantitative accuracy in the recont
ructed slices when attenuation was present. Neither bull's eye map homogene
ity nor contrast between a hot and a cold region were affected by depth-dep
endent collimator response or finite spatial resolution. Bull's eye map hom
ogeneity was severely affected by attenuation but not by scatter. Attenuati
on and scatter reduced contrast by about 20% each. Both attenuation and sca
tter increased the full-width at half-maximum (FWHM) characterizing the spa
tial resolution of the imaging system by approximate to 1 mm each but the m
ain effect responsible for the observed 11-mm FWHM spatial resolution was t
he depth-dependent collimator response. SNR was reduced by a factor of appr
oximate to 2.5 because of attenuation, while scattered counts increased SNR
by approximate to 10%. In conclusion, the quantification of the relative i
nfluence of the different physical effects showed that attenuation is defin
itely the major phenomenon affecting cardiac SPET imaging accuracy, but tha
t finite spatial resolution, scatter and depth-dependent collimator respons
e also contribute significantly to the errors in absolute and relative quan
titation and to the poor spatial resolution.