| 摘要 |
PURPOSE:To improve the diagnosis performance of X-ray images by stressing extralow-frequency components thereby increasing the contrast in medical diagnosis. CONSTITUTION:A cumulative phosphor material is scanned, and the radiographic image information recorded in this is read out and is converted to an electric signal, after which this signal is reproduced as a visible image on a recording material. In this case, the unsharp mask signal Sus corresponding to the extralow-spacial- frequencies in the respective scanning points is determined, and the operation of S'=Sorg+beta(Sorg-Sus) is made where the original image signal read out from the phosphor is defined as Sorg and the coefft. of stressing as beta, whereby the frequency components above the extralow spacial frequencies are stressed. With the coefft. kept constant, the maximum value of the modulation transmission function of the system giving the stressed photographic image is made 1.5-6 times the value of the modulation transmission function near zero space frequencies. |
