Coincidence gamma camera imaging: Can it be more helpful than dedicated SPECT in developing countries? A comparison between the two modes of imaging

Abstract

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Objectives: Scintillation cameras with the coincidence mode may be considered as an intermediate device between SPECT and PET systems that provides relatively inexpensive opportunity to perform some PET studies. In this study we investigate the resolution and accuracy of a system in SPECT and coincidence modes. Methods: The dual detector gamma camera (Vertex MCD, ADAC) equipped with a 5/8-inch crystal was investigated. The SPECT studies were performed with VXHR collimator in 128*128 matrix size using 99mTc. The brain phantom, SPECT resolution phantom and NEMA line-spread phantom were imaged in both modes five times each. Each dataset were reconstructed using filtered backprojection and also ordered subset exception maximization algorithm. Attenuation correction (μ=0.095 cm-1) and random correction techniques were used in this study. Results: The best reconstruction condition was determined based on the spatial resolution, contrast and image quality (visual inspection). The resolution in coincidence mode were significantly (p-value <0.001) higher than the corresponding images in conventional mode. The mean of FWHM with scatter SPECT was 12.74 ± 1.84 but FWHM with scatter Coincidence was 11.8 ± 0.57. The mean of FWHM without scatter SPECT was 11.68± 2.13 but FWHM with scatter Coincidence was 10.49± 0.37. The mean of FWTM with scatter SPECT was 64.00 ± 9.4 but FWTM with scatter coincidence was 59.01± 3.43 and mean of FWTM without scatter SPECT was found 58.93± 11.18 but FWTM without scatter Coincidence was 52.77± 1.38. Conclusions: We concluded that PET-SPECT system can be used as a flexible low cost system with superior data compared to SPECT. The coincidence gamma camera may be useful when a PET system is not available. Since now the emphasis has been on inferior quality of coincidence image compared to PET images. Nevertheless the quality of such system comparing to conventional mode should also be considered.