Comparison of the detection rates in reduced image by difference of interpolation method

Abstract

In the soft copy diagnosis, each pixel of the detector is displayed to the correspondent pixel of liquid crystal display (LCD). But when the image is displayed at the first time, the entire image may be reduced. We examined the influence that the difference of image reduction rate on LCD exerts on detection performance by using observer performance experiment. Moreover, to find the best interpolation method, we investigated the several interpolation methods. We made a simulation image which is similar to Burger phantom. This image consists of 288 signals, each of a different size and contrast. The matrix size is the same as Phase Contrast Mammography (PCM). We gradated the simulation image by using an MTF of a geometric blur, and the image was added to the noise image which is uniformly exposed with PCM. Then the image was reduced by using the nearest-neighbor, the bilinear, and the bicubic methods. The reduction rates were calculated as the ratios of the number of pixels of LCDs to those of PCM. We displayed the reduced images on LCD and examined the detection performance. Results of physical evaluation examined before showed that sharpness and granularity have worsened both in proportion to the reduction rate. The detection performance deteriorated as the reduction rate becomes high. In the comparison of the interpolation methods, the detection performance of the nearestneighbor method was worse than those of other interpolation methods. The bilinear method is the most suitable for the reduction of the image.