CR系统自动曝光控制摄影参数与图像后处理

目的:分析CR系统自动曝光控制(电离室)X线摄影特点,探讨图像后处理技术对影像质量的影响。方法:①以A、B、C3组(每组180例)不同组合的kV、mAs、密度补偿、感速、探测野等,对胸部拟人水模及IP板自动曝光控制摄影;②检测3种组合患者影像不同曝光条件、曝光指数、kV与mAs变化及照片密度值。结果:①A组125kV与0.6~1.0mAs组合,图像对比度差;低密度偏高;信噪比低;量子斑点多噪声大。②B组70~85kV与5~30mAs组合,图像对比度好;层次清楚;锐利度高;量子斑点少噪声小。A、B两组差异有显著意义,P<0.001。③C组42~52kV与5~20mAs组合,图像对比度高;层次清楚;锐利度高;量子斑点少噪声小。B、C两组差异没有统计学意义(P>0.05)。④测量胸片、腰、颈椎等的密度值均在0.8~1.30范围内。结论:CR系统自动曝光控制不宜采用高kV或太低kV摄影,检测病灶细微结构应使用尺寸相对较小的成像板。数字化摄影图像信息后处理技术,保证了照片质量,提高了影像学诊断范围及准确率。

Synthetic Evaluation of the Computer Radiography System Imaging Quality

Objective: To analyze Xray automatic exposure control (AEC) radiograp hy in computer radiography (CR) system and to evaluate the system imaging charac teristic parameters synthetically. Methods: ① Different combin ations of voltage, density compensation, speed of sense and field of detection w ere chosen for personification chest water model and IP plate automatic exposing in group A, B and C (each group consisted of 180 cases respectively). ② The ex posure parameters, exposure index, the variety of exposure index and the films d ensity were measured in different combinations in the three groups. Resu lts: ① CR images in group A with the combination of 125 kV and 0.6~1.0 mAs showed low image contrast and more quantum speckles and high noise. ② CR images in group B with the combination of 70~85 kV and 5~30 mAs accquired fin e contrast, that showed with distinct hiberarchy and high sharpness, and less qu antum speckles and low noise. The difference between group A and B was significa nt,P<0.001. ③ CR images in group C with the combination of 42~52 kV and 5 ~20 mAs accquired high contrast and less quantum speckles and low noise. There w as no significant difference between group B and C(P>0.05). ④ The densiti es of thoracic, lumbar and cervical vertebra in CR films was ranging from 0.8 to 1.30. Conclusion: The high voltage or too low voltage for Xra y radiography is not appropriate in the CR AEC. In order to detect the fine stru cture in the focus, the less size imaging plate should be utilized.