G. El Fakhri et al., Should scatter be corrected in both transmission and emission data for accurate quantitation in cardiac SPET?, EUR J NUCL, 27(9), 2000, pp. 1356-1364
Citations number
19
Categorie Soggetti
Radiology ,Nuclear Medicine & Imaging","Medical Research Diagnosis & Treatment
Ideally, reliable quantitation in single-photon emission tomography (SPET)
requires both emission and transmission data to be scatter free. Although s
catter in emission data has been extensively studied, it is not well known
how scatter in transmission data affects relative and absolute quantitation
in reconstructed images. We studied SPET quantitative accuracy for differe
nt amounts of scatter in emission and transmission data using a Utah phanto
m and a cardiac Data Spectrum phantom including different attenuating media
. Acquisitions over 180 degrees were considered and three projection sets w
ere derived: 20% images and Jaszczak and triple-energy-window scatter-corre
cted projections. Transmission data were acquired using gadolinium-153 line
sources in a 90-110 keV window using a narrow or wide scanning window. The
transmission scans were performed either simultaneously with the emission
acquisition or 24 h later. Transmission maps were reconstructed using filte
red backprojection and mu values were linearly scaled from 100 to 140 keV.
Attenuation-corrected images were reconstructed using a conjugate gradient
minimal residual algorithm. The mu value underestimation varied between 4%
with a narrow transmission window in soft tissue and 22% with a wide window
in a material simulating bone. Scatter in the emission and transmission da
ta had little effect on the uniformity of activity distribution in the left
ventricle wall and in a uniformly hot compartment of the Utah phantom. Cor
recting the transmission data for scatter had no impact on contrast between
a hot and a cold region or on signal-to-noise ratio (SNR) in regions with
uniform activity distribution, while correcting the emission data for scatt
er improved contrast and reduced SNR. For absolute quantitation, the most a
ccurate results (bias <4% in both phantoms) were obtained when reducing sca
tter in both emission and transmission data. In conclusion, trying to obtai
n the same amount of scatter in emission and transmission data, in addition
to being impractical because of the difficulty in knowing the precise scat
ter components, did not yield such accurate absolute activity quantitation
as when emission and transmission scatter were reduced.