Diagnosis Defect of Heart SPECT Images with Changing in Imaging Protocol

Introduction: Unfortunately, despite the low cost and non-invasive character of cardiac SPECT imaging, this method has relatively low quality images. As a result, the sensitivity and specificity of this method is considerably lower than angiography. In this study which was performed using Monte Carlo simulation, with constant counting, the effects of increasing the number of shots from 32 to 64 on the image quality parameters were investigated.Materials and methods: In this study, 99m Tc was considered as accurate information of the ENSDF data bank. NCAT humanoid digital phantom of a millimeter resolution and in three different sizes (large, medium and small) was used for simulation. (SimSET) code was used for SPECT images simulation. Two sets of images were taken from each phantom. In the first shooting, 32 images with an average count of 100,000 as the shahed images and in the second image, 64 images with the count of 50,000 as test images were taken. In the end, all images were reconstructed using FBP method and the parameters of resolution, contrast and signal to noise ratio in the image, was calculated to compare.Results: By increasing the number of shots and keeping the time of imaging constant, in the reconstructed images of slices Short Axis and Hor LA and Ver LA, sensible improvement in fence to cavity and fence to background has been observed. But signal to noise ratio has decreased.Conclusion: According to FBP reconstruction theory and the effect of the number of shots on the reconstructed image, improvement of image contrast by increasing the number of shots was expected. Since the resolution reflects contrast, improvement of resolution is also expected. Since recording an image in nuclear medicine follows Poisson statistics, thereby reducing the SNR occurs by reducing the number of photons. Therefore, by keeping the count of photons constant and increasing the number of shots, without increasing the imaging time, one can improve contrast and resolution SPECT images of the heart.