[Correction of Partial Volume Effect Using CT Images in Brain 18F-FDG PET].

PURPOSE: We performed partial volume effect correction of PET images using 18F-FDG-PET and CT images taken consecutively, compared it with correction using MRI images, and investigated the usefulness of correction using CT images. METHODS: A total of 9 clinically normal subjects were included in the study, and the CT and MRI images of each subject were segmented and normalized. PET images were coregistered to each morphological image and then normalized. The normalized morphological images of each subject were used to mask the brain atlas and to correct for the partial volume effect. For each brain region, comparison of counts, two-group test between CT- and MRI-corrected groups, and correlation analysis were performed. RESULTS: As a result of correction, some error was observed between the two groups. Correlation analysis showed strong positive correlations in many areas, but weak correlations were found in some areas. In the region where significant differences were found, the two groups showed strong positive correlation, and in the region where weak correlation was found, the error tended to be small. CONCLUSION: It is suggested that the correction by CT can be performed with the same accuracy, although some errors are generated compared with MRI.

[Usefulness of the collimator detector response (CDR) recovery and the scatter correction by the effective scatter source estimation (ESSE) method in myocardial SPECT study].

UNLABELLED: The aim of this study was to evaluate the usefulness of the collimator detector response (CDR) recovery and the effective scatter source estimation (ESSE) method which is the scatter correction method built into the ordered subsets expectation maximization (OSEM) method. METHOD: The SPECT quality evaluation phantom and the anthropomorphic torso phantom were used in this study, and image contrast and uniformity were evaluated. The effect of each image correction method on the quantification of absolute radioactivity was also assessed. RESULTS AND CONCLUSION: Image contrast and uniformity were improved with the combination of the CDR recovery and triple energy window (TEW) method or the ESSE method. The combination of the CDR recovery and the ESSE method was the best method for the estimation of absolute radioactivity. Image quality of the SPECT is improved by the combination of CDR recovery and scatter correction in addition to attenuation correction. CDR recovery in addition to attenuation and scatter correction is also useful for the quantification of absolute radioactivity.

[Effect of reconstruction parameters on a calculation of left ventricular volumes by OS-EM reconstruction algorithm including various image corrections].

UNLABELLED: The aim of this study was to evaluate the effect of reconstruction parameters on the measurement of global left ventricular (LV) volume and define the appropriate reconstruction parameters when using the ordered subsets expectation maximization (OS-EM) method and 3D OS-EM (Astonish) method including the collimator distance response (CDR) recovery (RC) for myocardial perfusion SPECT study. METHOD: An anthropomorphic torso phantom with a 56 ml LV part was used. The LV volume was calculated with QPS software by the Update number (iteration number x subsets number) of OS-EM and 3D OS-EM (Astonish). RESULTS AND CONCLUSION: LV volumes calculated with OS-EM and Astonish without attenuation and scatter corrections corresponded to the true obtained by the Update number about 32 times and 24 times when using the OS-EM and Astonish method with attenuation and scatter corrections, respectively. However, LV volumes have changed greatly in the Astonish method according to the change in the Update number. Appropriate numbers of iterations and subsets are the measurement of global LV volumes, especially when using the OS-EM algorithm with RC.