[Study of the normal database that affects 3D-SSP Z-score mapping].

The effects of image reconstruction conditions and devices used on 3D-SSP analysis (Z-score mapping) were investigated. Images of the 3D Hoffman brain phantom were taken with the IRIX device or E.CAM. Using two methods of image reconstruction (FBP and OSEM), several kinds of phantom normal databases (PNDB) and signal data, with or without correction for attenuation, were obtained at varying Butterworth filter cutoff frequencies. The results of 3D-SSP analyses were compared between combinations of PNDB and signal data obtained under the same conditions of image reconstruction and combinations obtained under different conditions. The results of PNDB obtained with different devices were also analyzed. For combinations of PNDB and signal data both obtained with OSEM, the Z-score of signals was high. When FBP was used to obtain both PNDB and signal data, the Z-score and signal size tended to become greater and the false-positive rate tended to decrease as the Butterworth filter cutoff frequency became lower. Whether or not correction for attenuation was incorporated did not affect the results of analysis when the same method was used to collect both PNDB and signal data. If the method for image reconstruction differed between PNDB and signal data, the false-positive rate was relatively high. Using a different device to obtain PNDB resulted in a relatively high false-positive rate. We therefore recommend that the conditions for image reconstruction from signal data should be matched to the conditions for image reconstruction from PNDB. It seems impossible to share the same NDB among different devices.