Physical Factors Affecting Dual Radioisotopes SPECT Image Quality

Abstract

Dual Single Photon Emission Computed Tomography (DSPECT) is a technique for studying the biodistribution of dual radioactive tracers introduced into the body in the same time, which provides high contrast of three-dimensional images. DSPECT imaging has several potential advantages over conventional SPECT imaging. However, special attention is needed, and a DSPECT system will not produce adequate results unless corrections & very great care is taken in both acquisition and reconstruction of the image.

The aim of This study was to investigate the effects of source concentration, acquisition parameters and reconstruction parameters on DSPECT image quality. DSPECT imaging with a dual-head gamma camera was performed on Jaszczak phantoms filled with a different concentration of 131I & 99mTc solutions, using different acquisition parameters. The acquire images reconstructed using different algorithms such as FBP, OSEM and FLASH 3-D. with evaluate the scattering effects on image quality. The FWHM (characterizing the spatial resolution of the imaging system), differential uniformity, contrast, and SNR in the three transverse slices of the phantom was analyzed.

When the phantom filled with 20 mCi 99mTc-400 µCi 131I, the reconstructed images were showed that improved FWHM, differential uniformity and contrast (P-values were statistically significant) with a suitable SNR. On the other hand, HEGP collimator had better FWHM, differential uniformity and contrast (P-values were statistically significant) with a suitable SNR. In the case of (number of projections) showed improvement of resolution (FWHM) of 128 views rather than in 32 and 64 views. But in the case of Diff. Unif. % and the contrast we found that 64 NOP has the better values, which indicate the higher image quality. For SNR 32 NOP given the best values. In practice, approximately 60 views are adequate for most clinical studies. From our study, we conclude that to optimize the DSPECT imaging quality we must select the 64 NOP with time per views 30 sec.

We found that the compensation for scattering is required to improve the dual SPECT image quality. The best way to perform such compensation is TEW subtraction method. Also, the study showed that, the reconstruction of DSPECT data were by (OSEM) iterative algorithm demonstrated quantitative accuracy comparable to FBP, FLASH-3D algorithm.