Filter backprojection is an important method of image reconstruction technique in clinical nuclear medicine imaging. Because of noisy images due to less available photon statistics and different factors associated with imaging system in nuclear medicine tomography, using optimal filter to suppress the noise with keeping the proper signal is one of the significant steps in image reconstruction strategy for clinical use. In this paper, we present the effect of implementation of different filters on the hot region of Carlson phantom SPECT image in reconstruction process. By defining some criteria such as image smoothness and contrast, estimation of spatial resolution and location of hot cylindrical sources and their detectability the best filter with specified parameter have been determined and the results have been interpreted. Results show that the perceived image quality of hot region and also their detectability has been improved when Shepp-Logan and Ram-Lak filters with cut-off frequency of 0.4 has been used.