| 摘要 |
PURPOSE: To perform an image processing suitable for a diagnosis corresponding to the change of photographing section and photographing condition. CONSTITUTION: Based on image signals in an irradiation field region, an image signal region (Smin-ThresH) of an object is specified and a histogram of the image signals in an object region is drawn up (S1-S3). At this point, total sum of frequencies in the histogram is calculated and 0.1% value of the total sum is set as a threshold value. Then, comparisons between the threshold value and a frequency are made from a peak position of frequency nearest to the maximum value (ThresH) toward lower signal side and the first signal value below the threshold value is made minimum value ThresL in the desired image signal region (S8). Then, a cumulative histogram is drawn up between the minimum value ThresL and the maximum value ThresH (S9) and a gradation conversion table is determined so that a signal value attaining 10% cumulative histogram value corresponds to the prescribed output density and gradation processing is applied to the radiation image signals (S10). |
