Restoration of I-131 whole body image using a Wiener filter

The aim of the study was to restore I-131 whole body image using Wiener filter.

A set of 50 I-131 whole body images acquired using Symbia E dual head gamma camera with high energy general purpose collimator was used. The Gaussian point-spread function (PSF) characterised by the size (3, 5, 7, 9, 11, and 13 pixels) and corresponding standard deviation (0.5, 0.75, 1, 1.5, 1.75, and 2 pixels) and noise-to-signal power ratios (NSR: 0, 0.001, 0.01, 0.1, 0.2, 0.3, 0.4, and 0.5) were used as parameters for Wiener filter. Using the combinations of PSF and NSR, a total of 2450 images (50 × 49 = 2450 images, where 49 images include 1 input and 48 restored images for each input image) were generated and inspected by two nuclear medicine physicians. They selected one best image (the image which had less noise and better contrast between the lesion and background in comparison with the input image). Their results were analyzed.

Compared to input image, the metastatic uptake in restored images was very easily perceived. The restored image obtained with PSF (size = 13, sigma = 2) and NSR = 0.3 had better signal-to-noise ratio in comparison to restored image obtained with PSF (size = 11, sigma = 1.75) and NSR = 0.2.

The restored images with PSF (size = 13, sigma = 2) and NSR = 0.3 were found to have superior image quality in comparison with its input image.