フィルム/増感紙システムのクロスオーバー効果の影響 | （―― 特性曲線とModulation Transfer Function ――） | The Influence of Crossover Effect of the Film/Screen System | （―― Characteristic Curve and Modulation Transfer Function ――）

東北大医短部紀要　11(2) : 301～309，2002

フィルム/増感紙システムのクロスオーバー効果の影響
（—— 特性曲線とModulation Transfer Function ——）

佐々木正臣，大石幹雄^*，小倉隆英^*
阿部志津子，洞口正之^*
仙石病院放射線科
^*東北大学医療技術短期大学部診療放射線技術学科

The Influence of Crossover Effect of the Film/Screen System
（—— Characteristic Curve and Modulation Transfer Function ——）

Masaomi SASAKI, Mikio OISHI^*, Takahide OGURA^*,
Shizuko ABE and Masayuki ZUGUCHI^*
Senseki Hospital
^*Department of Radiological Technology, College of Medical Sciences, Tohoku University

Key words : characteristic curve, crossover effect, MTF, One side emulsion film

The present film/screen system consists of both-sided emulsion film with a sheet of screen at its front and back. It is reasonable to think that crossover effect is generated in such a system. So, it could be found out whether there is any crossover effect or not if a system in which no crossover effect is generated at all is made and if its characteristics are compared with those of a general system.
The characteristic curves were measured by using a bootstrap method. Our system was superior to in average gradation G, and ratio sensitivity. The ratio sensitivity of this system to a general system was 113～122% at 80 kV. Sensitivity was measured by using a rectangle wave chart method. The MTF values at 2 LP/mm were 0.35 in a general system and 0.32 in our system. The spatial frequencies at which the MTF value was 0.1 were 5.2 LP/mm in a general system and 5.1 LP/mm in our system. They were almost the same though the MTF value in our system slightly lower. The results of our experiment show that in general X-ray film, though every possible measure should be taken to lower crossover effect, it is generated at higher voltages.