Title :
Simultaneous Tc-99m/Tl-201 imaging using energy-based estimation of the spatial distributions of contaminant photons
Author :
Moore, Stephen C. ; English, Robert J. ; Syravanh, C. ; Tow, Donald E. ; Zimmerman, Robert E. ; Chan, Karen H. ; Kijewski, Marie F.
Author_Institution :
Nucl. Med. Service, V.A. Med. Center, W. Roxbury, MA, USA
fDate :
8/1/1995 12:00:00 AM
Abstract :
The advantages of simultaneous acquisition of Tc-99m and Tl-201 myocardial perfusion SPECT images can be fully realized only if the effects of the Tc-99m agent can be accurately removed from the Tl-201 image. We and others have previously reported simultaneous dual-isotope techniques for cardiac studies which make use of a third energy-window to estimate the Tc-99m scatter to be subtracted from the TI-201 window. We have recently demonstrated, however, using a Monte Carlo program which simulates all details of the photon transport, that lead X-rays produced in the collimator may also contribute significantly to contamination in the Tl-201 window. The spatial distribution of the Tc-99m scattered photons differs from that of the lead X-rays. Therefore, we modified our correction technique so that, at each projection angle, the contaminant image to be subtracted from the image in the Tl-201 window was estimated as a linear combination of a scatter-window (90-110 keV) image, blurred by a 2D Gaussian filter, and the Tc-99m photopeak image, blurred by a different Gaussian filter. For simulated data which included `liver´ activity and non-uniform `lung´ attenuation, the improved dual-window subtraction technique provided a more accurate estimate of the true TI-201 image, with less image noise, than did the single-window correction
Keywords :
Monte Carlo methods; cardiology; liver; lung; single photon emission computed tomography; technetium; thallium; 2D Gaussian filter; 90 to 110 keV; Monte Carlo program; Pb; Tc; Tl; X-rays; cardiac studies; collimator; contaminant photons; dual-isotope techniques; energy-based estimation; liver activity; myocardial perfusion SPECT images; nonuniform lung attenuation; photon transport; photopeak image; simultaneous 99mTc/201Tl imaging; simultaneous acquisition; single photon emission computed tomography; single-window correction; spatial distributions; Contamination; Electromagnetic scattering; Liver; Monte Carlo methods; Myocardium; Nonlinear filters; Optical collimators; Particle scattering; Single photon emission computed tomography; X-ray scattering;
Journal_Title :
Nuclear Science, IEEE Transactions on