Objective To test the overall characteristic curve on a computed radiography system. Methods Imaging plate was exposed by scale-time expose using conventional X-ray equipment. It was processed by CR system. Density of different optical density wedge on CR film was measured by using densimeter. Then, characteristic curve was plotted. Results (1) Overall characteristic curve of CR system was affected by gradation processing. (2) Average gradient of overall characteristic curve was 1.98, 3.10, and 3.75 when GA was 0.8,1.4, and 2.4. (3) Overall characteristic curve rotated around rotation center when rotation amount was changed. Conclusion According to the diagnostic purpose and different body position, rotation amount can be selected, and different contrast imaging can be acquired.

Objective:To study the effects of ~(125)I-(α_v)ASODN on the in vitro invasive ability of heptocellular carcino-ma cell line(HepG2) through PEI-RGD-mediated receptor process. Methods: Intergrin α_v-specific antisense oligonucle-otide was labeled with ~(125)I, and PEI-RGD/~(125)I-(α_v)ASODN complex was prepared by combining ~(125)I-(α_v)ASODN with polyethyleneimine derivative PEI-RGD. PEI-RGD/~(125)I-(α_v)ASODN complex was transferred into HepG2 cells through the receptor-mediated process. The effect of PEI-RGD/~(125)I-(α_v)ASODN complex on the invasive ability of HepG2 cells was examined by Boyden chamber invasive assay. Results: (1) The labeling yield and radiochemical purity of ~(125)I-(α_v) ASODN were(73.78±4.09)% and(96.68±1.38)%, respectively, and the labeled compound had a good stability in vitro after 48 h at 37℃; (2) The ability of HepG2 cells to uptake PEI-RGD/~(125)I-(α_v)ASODN reached its peek ([12.77±0.85] % ) when PEI-RGD/~(125)I-(α_v)ASODN was at 4 μl/2 μg ([12.77±0.85] %), and then gredually decreased thereafter. So the dosage of PEI-RGD/~(125)I-(α_v)ASODN for the following experiment was chosen as 2 μl/1 μg; (3) The invasive capacity of HepG2 cells was significantly reduced in PEI-RGD/~(125)I-(α_v)ASODN group compared with those in other experiment and control groups (P <0.01 ). Conclusion: ~(125)I-(α_v)ASODN mediated by PEI-RGD can effectively inhibit the invasive capacity of HepG2 cells.