Enhanced cross‐talk correction technique for simultaneous dual‐isotope imaging: A TL‐201/Tc‐99m myocardial perfusion SPECT dog study

Abstract

A newly developed cross-talk correction method for simultaneous dual-isotope SPECT imaging was tested in a canine model. The method is based on the assumption that the transformations, which modify the primary energy window images into the scatter images as viewed in the other energy windows, are known. These transformations were found by measuring the point spread functions (PSFs) in two different energy windows for both isotopes in water. The dual-isotope correction method is described by two convolution equations which were applied in frequency space. The equations take into account the different spatial distributions of the primary and scatter cross-talk photons. The new enhancement of the method was in applying restoration filters to the resulting corrected images. Three separate studies were acquired in our dog study: two single-isotope and one dual-isotope study. The single isotope images were used as references. The contrast between the left ventricle cavity (LVC) and the myocardium was used in transaxial and short-axis slices as a parameter to evaluate results of dual-isotope correction method with restoration. The change in contrast in the dual-isotope corrected images in both energy windows, i.e., Tc-99m primary window (140 keV) and Tl-201 primary window (70 keV), was significant. The only exception was for the short-axis Tc-99m window images. The corrected 140 keV dual-isotope short-axis slice had the contrast of 0.60 vs 0.58, which was the value in the noncorrected dual-isotope short-axis slice. For dual-isotope 140 keV transaxial slice, the contrast changed from 0.72 to 0.82 after correction. In comparison, for single-isotope Tc-99m 140 keV transaxial slice, contrast changed from 0.62 to 0.84 after restoration correction. There was less change in contrast in the short-axis Tc-99m 140 keV slice, i.e., from 0.56 to 0.61. In the Tl-201 primary window for the transaxial slices the improvement of contrast was from 0.38 to 0.64, and for short-axis slices from 0.22 to 0.32 after correction. In the same 70 keV energy window for single-isotope Tl-201 images, contrast improved from 0.61 to 0.69 and from 0.35 to 0.38 for transaxial and short-axis slice, respectively, after applying restoration correction. In conclusion, the presented dual-isotope correction method with restoration improves the quality of the simultaneous rest Tl-201/stress Tc-99m sestamibi SPECT imaging.

Iterative deconvolution of simultaneous99mTc and201Tl projection data measured on a CdZnTe-based cardiac SPECT scanner

“…A similar approach has been reported in (Hademenos et al 1995). A spectral and spatial deconvolution technique, which can be applied to projection data or reconstructed images has been proposed and evaluated in Knesaurek (1994) and Knesaurek and Machac (1997). Hannequin et al (2000Hannequin et al ( , 2001 describe a method of recovering photopeak counts from projection data collected in multiple subwindows within the usual energy windows.…”

Analytical calculation of photon distributions in SPECT projections

“…Other cross-talk correction techniques have b e n suggested for use with 201T1 -99mT~ heart imaging: multiple energy window based methods such as TEW (2.2.4) [162, 180, 1811 and subtraction of a filtered version of the 99mTc-image [182]. These approaches have not, however, been tested with regards to 99mT~-1231 imaging and may be difficult to apply due to the similarity of the primary energies of these two isotopes.…”

Improvement of the fluorine‐18 fluorodeoxyglucose images in simultaneous F‐18 FDG/Tc‐99m collimated spect imaging

“…17 Recently, cross-talk corrections have been combined with the restoration approach. 11,19,20 Our system was calibrated by the single-isotope Tc-99m and F-18 point source acquisitions in a water-filled cylindrical phantom with a diameter of 23 cm. The point source was placed at distances of 0 cm, 2.5 cm, 5 cm, 7.5 cm and 9 cm from the center of the phantom.…”