A comparison of the Wiener filter vs. Metz filter for detection of lesions on FDG linear whole body coincidence tomographic images

2130 Objectives : Choosing a proper filter to reduce noise and obtain high resolution is desirable. There is balance between obtaining a high resolution image and obtaining a smooth image, as increasing smoothing through filtering will reduce resolution. At our institution we apply adaptive filters, such as the Wiener filter and the Metz filter, that utilize a multiplier value to create different curve shapes to provide good smoothing and constant count areas, and to control the roll off portion of the curves to provide excellent edge retention of objects. The purpose of this study is to compare the outcome of coincidence studies done with both Wiener and Metz filters with regard to lesion detection. Methods : 19 studies (10 male, 9 female) were randomly selected. Each patient was injected with 10 mCi of 18F-FDG and a whole body linear tomographic sweep study scan was performed with a coincidence method. Each study was processed twice using Wiener and Metz filters. Two nuclear medicine physicians were asked to independently evaluate these images for the number of lesions and quality of images. Patients9 body mass indices (BMI) were calculated for those cases that showed obvious preference for one of the filters. Results : 74% of the cases were comparatively noted as "same" in resolution, including 5 cases showing no lesions. Both physicians agreed that the Wiener filter had better resolution in 4 cases that fell within the normal BMI range (18.5-24.9). There were 2 cases that fell into the overweight range for BMI (25.0-29.9); one physician preferred the Metz filter for better resolution, while the other noted them as the same. In only 1 case that fell into the obese range for BMI (30.0 and above), did both physicians agree that the Metz filter was much better. Conclusions : We conclude that there is no significant difference in the overall resolution of either filter. The filter of choice is based upon personal preference. The findings suggest that when processing 18F-FDG whole body linear scans with coincidence imaging, BMI should be taken into consideration when selecting a filter. Based on our results, the Metz filter may be the preferred choice for overweight patients, and the Wiener filter for average weight patients.