Denoising images of dual energy X-ray absorptiometry using non-local means filters.

BACKGROUND: In general, the image quality of high and low energy images of dual energy X-ray absorptiometry (DXA) suffers from noise due to the use of a small amount of X-rays. Denoising of DXA images could be a key process to improve a bone mineral density map, which is derived from a pair of high and low energy images. This could further improve the accuracy of diagnosis of bone fractures and osteoporosis. OBJECTIVE: This study aims to develop and test a new technology to improve the quality, remove the noise, and preserve the edges and fine details of real DXA images. METHODS: In this study, a denoising technique for high and low energy DXA images using a non-local mean filter (NLM) was presented. The source and detector noises of a DXA system were modeled for both high and low DXA images. Then, the optimized parameters of the NLM filter were derived utilizing the experimental data from CIRS-BFP phantoms. After that, the optimized NLM was tested and verified using the DXA images of the phantoms and real human spine and femur. RESULTS: Quantitative evaluation of the results showed average 24.22% and 34.43% improvement of the signal-to-noise ratio for real high and low spine images, respectively, while the improvements were about 15.26% and 13.55% for the high and low images of the femur. The qualitative visual observations of both phantom and real structures also showed significantly improved quality and reduced noise while preserving the edges in both high and low energy images. Our results demonstrate that the proposed NLM outperforms the conventional method using an anisotropic diffusion filter (ADF) and median techniques for all phantom and real human DXA images. CONCLUSIONS: Our work suggests that denoising via NLM could be a key preprocessing method for clinical DXA imaging.

Growth Suppression and Induction of Chemosensitivity in Human Gallbladder Epithelial Carcinoma Cells (GBCE) by Adenovirus-Mediated Transfer of the Wild-type p53 Gene.

PURPOSE: Mutations in the p53 gene are reported in 50~90% of gallbladder and bile duct cancer, and have been implicated in chemoresistance. We undertook this study to determine whether the introduction of the wild type p53 gene into GBCE (human gallbladder cancer cell line with a heterozygous p53 mutation) by an adenoviral vector could increase the sensitivity of the cell to 5-FU, a commonly used drug in the treatment of gallbladder cancer. MATERIALS AND METHODS: GBCE cells were transfected with either Ad/p53 or Ad/E1 in the presence of 5-FU. Gene expression was confirmed by western blotting. Nude mice were injected subcutaneously with GBCE cells. When tumors formed, intratumoral injection of Ad/p53 was performed. Reduction of tumor size was compared in two weeks of Ad/p53 gene transfection. RESULTS: Ad/53 transfection induced a dose-dependent inhibition of tumor growth. Tumor colony formation was more inhibited with p53 gene transfection than with mock transfection in the presence of 5-FU. The reduction in tumor size was more pronounced with p53 transfection than with mock infection. CONCLUSION: These treatment modalities could be utilized in the treatment of p53 mutant human gallbladder cancers.