Qualitative evaluation of filter function in brain SPECT

Filtering can greatly affect the quality of clinical images. Determining the best filter and the proper degree of smoothing can help to ensure the most accurate diagnosis. Forty five patient’s data aquired during brain phantom SPECT studies were reconstructed using filtered back-projection technique. The ramp, Shepp-Logan, Cosine, Hamming, Hanning, Butterworth, Metz and Wiener filters were examined to find the optimum condition for each filter. For each slice image, 6200 reconstruction options were considered. The corresponding planar image of each slice was used as the reference image. The quality of reconstructed images was determined using universal image quality index (UIQI). Four nuclear medicine physicians evaluated the images to choose the best of the filters. Images with best resolution, contrast, smoothness and overall quality were selected by nuclear medicine physicians depending on filters used to generate the best image. A significant difference (p<0.05) between the filters regarding these parameters were observed. The results of this study revealed that maximum resolution and contrast could be obtained using both Metz and Wiener filters. However, the best quality images were generated by using Butterworth filter.