对一种蓝色染料影象的象质评价

本文对黑白胶片经过特殊的蓝色成象工艺加工后形成的影象的质量进行了客观评价。结果表明,用蓝色成象工艺,感光度、特性曲线直线部分的斜率γ、最大密度及调制传递函数在低空间频率的响应等,均较黑白影象有不同程度的改善和提高;分辨率基本相同;粒度有些增高;调制传递函数的高频响应变坏。这种成象工艺用于对空间频率上限要求不高的一些成象体系,如X射线照象是有利的。这与临床诊断的主观评价的结果一致。

IMAGE ASSESSMENT FOR THE BLUE IMAGING TECHNOLOGY FOR MEDICAL RADIOGRAPHY

A blue imaging technology for medical radiography has been developed in this institute. It was proved superior to ordinary B/W radiographic film in that the X-ray dose can be reduced to 1/5 and all the silver can be recovered. Image assessment has been done in this work with the determination of the speed, gamma, resolving power, MTF and noise level of the blue dye image and in comparison with that of the silver image. B/W radiographic films with on-eside emulsion coating were used in order to eliminate the complication imposed by the crossover effect in the MTF and noise level determinations. The samples were exposed with light and processed to B/W and blue images respectively. The results showed that the speed, gamma, Dmax and the low spatial frequency response of the MTF of the blue image are much improved compared with that of the B/W image, although the fog levels are a little bit higher. The resolving power of the blue image is almost the same of the B/W image. Both the macro- and micronoise are higher for the dye image, but no extra large-scale non-uniformity was introduced in the dye-image formation. The high frequency response of the MTF got poorer in forming the dye image. Summing up all these characteristics, the blue imaging technology is still favourable for medical radiography. In this case the useful imaging frequency range is extended to only about 10 1ps/mm, and the quantum mottle becomes the main source of noise. The-results obtained in this work are in accordance with that of the subjective evaluation in clinical diagnosis.