Correlation of ADC value with pathologic indexes in colorectal tumor homografts in Balb/c mouse

Objective： Noninvasive diffusion-weighted magnetic resonance imaging （DWI） is a well-studied MR imaging technique for quantifying water diffusion especially in tumor area. The correlation between apparent diffusion coefficient （ADC） value and apoptosis or proliferation is not clear by now. This study aimed to investigate whether DWI-ADC value could be used as an imaging marker related with pathologic indexes of tumors. Methods： A total of 3 0 Balb/c mice with HT2 9 colorectal carcinoma were subjected to DWI and histologic analysis. The percentage of ADC changes and the apoptotic and proliferating indexes were calculated at predefined time points. Kolmogorov-Smirnov distances were considered to determine whether the percentage of ADC changes, and the apoptotic and proliferating indexes were normally distributed. An independent-samples t-test was used to analyze the difference between apoptotic and proliferating indexes in the two groups. Results： There was a statistically significant difference in proliferating index between the radiotherapy and control groups （mean proliferating index： 49.27% vs. 83.09%）, and there was a statistically significant difference in apoptotic index between the two groups （mean apoptotic index： 37.7% vs. 2.71%）. A significant positive correlation was found between the percentage of ADC changes of the viable tissue and apoptotic index. Pearson＇s correlation coefficient was 0.655 （P=0.015）. A significant negative correlation was found between the percentage of ADC changes of the viable tissue and ki-67 proliferation index. Pearson＇s correlation coefficient was 0.734 （P〈0.001）. Conclusions： Our results suggest that ADC proliferating indexes in colorectal carcinoma. value may be used in measurement of cell apoptotic and

Modified Wiener method in diffusion weighted image denoising

To denoise the diffusion weighted images （DWls） featured as multi-boundary, which was very important for the calculation of accurate DTIs （diffusion tensor magnetic resonance imaging）, a modified Wiener filter was proposed. Through analyzing the widely accepted adaptive Wiener filter in image denoising fields, which suffered from annoying noise around the edges of DWIs and in turn greatly affected the denoising effect of DWIs, a local-shift method capable of overcoming the defect of the adaptive Wiener filter was proposed to help better denoising DWIs and the modified Wiener filter was constructed accordingly. To verify the denoising effect of the proposed method, the modified Wiener filter and adaptive Wiener filter were performed on the noisy DWI data, respectively, and the results of different methods were analyzed in detail and put into comparison. The experimental data show that, with the modified Wiener method, more satisfactory results such as lower non-positive tensor percentage and lower mean square errors of the fractional anisotropy map and trace map are obtained than those with the adaptive Wiener method, which in turn helps to produce more accurate DTIs.