Feasibility of dual radionuclide brain imaging with I‐123 and Tc‐99m

Abstract

A study was conducted to evaluate the feasibility of simultaneous dual radionuclide brain imaging with 123I and 99mTc using photopeak image subtraction techniques or offset photopeak image acquisition. The contribution of the photons from one radionuclide to a second radionuclide's photopeak energy window (crosstalk) was evaluated for SPECT and planar imaging of a brain phantom containing 123I and 99mTc for a range of activity levels and distribution properties approximating those in rCBF images of the adult human brain. Crosstalk was evaluated for 10% symmetrical energy windows centered on the 123I and 99mTc photopeaks and for 10% energy windows asymmetrically placed to the left and right of the center of the respective photopeaks. Major observations include: (1) in the centered photopeak windows, 99mTc crosstalk in the 123I window is 8.9% of the 99mTc seen in the 99mTc window and ranges from 37.5% to 75.0% of the 123I in the 123I window. 123I crosstalk is 37.8% of the 123I seen in the 123I window and ranges from 4.4% to 8.9% of the 99mTc seen in the 99mTc window; (2) the spatial distribution of a radionuclide's crosstalk photons differs from that observed in the radionuclide's photopeak window; (3) a 99mTc photopeak window offset to the left does not decrease 123I crosstalk, and the percentage of 99mTc scattered photons is significantly increased in the window.(ABSTRACT TRUNCATED AT 250 WORDS)

Analytical calculation of photon distributions in SPECT projections

“…The increase in sensitivity for 1231 was desired because typically the activity of 1231 in a brai, scan is lower than the 99mTc activity. The ratio of 99mTc to 1231 activity is normally between 3:1 and 7:l [177].…”

A novel quantitative dual-isotope method for simultaneous ventilation and perfusion lung SPET

“…The basic condition for its application is a set of transmission maps representing the linear attenuation coefficients for the same set of reconstructed SPET images and their projection data. The original scatter and activity decay-corrected projection emission data are then corrected according to: (8) where n is the iteration number, r is the distance along the projection axis and g i (r,θ) and a i (r,θ) represent the back-projection of transverse images through projection rays L(r,θ), respectively without and with attenuationweighted factors from the set of transmission data. The corrected projection data are used as an entry to the reconstruction algorithm, giving a new set of attenuated-corrected reconstructed sections, .…”

“…Dual-isotope imaging has also been used to assess perfusion and myocardial metabolism with a combination of fluorine-18 fluorodeoxyglucose (FDG) and 99m Tc-MIBI or 201 Tl [3,4,5] and to identify acute myocardial infarcts with 201 Tl and indium-111 antimyosin antibodies [6,7]. In examinations of the functional brain, dual-isotope techniques have been used for both resting and vasodilated rCBF studies with 99m Tc and iodine-123 [8,9]. In gastric emptying studies, a combination of 111 In and 99m Tc has being used for dynamic studies of the liquid and solid emptying phases [10].…”

Model-based correction for scatter and tailing effects in simultaneous99mTc and123I imaging for a CdZnTe cardiac SPECT camera

“…Suggested methods for simultaneous imaging in these cases include using an asymmetrical energy window for the 123 I photopeak (Devous et al 1992). This, however, reduces the counting efficiency for 123 I compared to using a symmetrical energy window (Ivanovic and Weber 1994). Other suggested methods for cross-contamination correction in dual radionuclide imaging using Anger cameras include model-based compensation (Kadrmas et al 1999), a rotation-based Monte Carlo simulation method (de Jong and Beekman 2000), constrained spectral factor analysis (El Fakhri et al 2000), the use of artificial neural networks (El Fakhri et al 2000, 2001, 2002, Zheng et al 2004, iterative generalised spectral factor analysis (Hapdey et al 2006), generalized five-dimensional dynamic and spectral factor analysis (El Fakhri et al 2006b), the Monte Carlo based joint iterative reconstruction algorithm (Ouyang et al 2007(Ouyang et al , 2009) and the analytical photon distribution algorithm (Shcherbinin et al 2009).…”