A high performance 3D cluster-based test of unsmoothed fMRI data.

Cluster-size tests (CST) based on random field theory have been widely adopted in fMRI data analysis to detect brain activation. However, most existing approaches can be used appropriately only when the image is highly smoothed in the spatial domain. Unfortunately, spatial smoothing degrades spatial specificity. Recently, a threshold-free cluster enhancement technique was proposed which does not require spatial smoothing, but this method can be used only for group level analysis. Advances in imaging technology now yield high quality high spatial resolution imaging data in single subjects and an inference approach that retains the benefits of greater spatial resolution is called for. In this work, we present a new CST with a correction for voxelation to address this problem. The theoretical formulation of the new approach based on Gaussian random fields is developed to estimate statistical significance using 3D statistical parametric maps without assuming spatial smoothness. Simulated phantom and resting-state fMRI experimental data are then used to compare the voxelation-corrected procedure to the widely used standard random field theory. Unlike standard random field theory approaches, which require heavy spatial smoothing, the new approach has a higher sensitivity for localizing activation regions without the requirement of spatial smoothness.

[Application of real-time fluorescence quantitative polymerase chain reaction techniques for prenatal diagnosis of Down syndrome].

OBJECTIVE: To investigate the value of real-time fluorescence quantitative PCR in diagnosis of Down syndrome with uncultured amniotic cells. METHODS: The uncultured amniocytes of 80 fetuses who were confirmed disomy 21 by chromosome analysis and 5 fetuses detected trisomy 21 and peripheral blood samples of 7 children diagnosed as Down syndrome were collected to extract gDNA and the real-time fluorescence quantitative PCR method was used to detect the original copies of Down syndrome critical region gene(3) (DSCR(3)) and GAPDH gene and then the ratio of DSCR(3)/GAPDH was calculated. RESULTS: The PCR product ratios of DSCR(3) to GAPDH in trisomy 21 from amniocytes and peripheral blood were ranged from 1.64 to 1.98 while in the normal control the ratio was only from 0.46 to 1.30. CONCLUSION: Real-time fluorescence quantitative PCR is a valuable method for rapid and accurate prenatal diagnosis of Down syndrome in uncultured amniotic cells.