Effect of removing image pixel noise bits on the detection of simulated lung nodules

[[abstract]]©1992 SPIE - Our previous studies used statistical methods to assess the noise level in digital images of various radiological modalities. We separated the pixel data into signal bits and noise bits and demonstrated visually that the removal of the noise bits will not affect the image quality. In this paper we report our further study and demonstrate quantitatively that the removal of noise bits has no effect on the image property. The detectability of simulated lung nodules on a wedge phantom is used as a basis for this study. The test phantom consists of a Lucite step wedge of 22 steps (12.5 mm/step) with nylon spheres (1/4 inch, 3/8 inch, and 1/2 inch diameter) simulating nodules kept at each step. Test images of the phantom were taken on a scanning equalization radiographic system which has better nodule detectability than conventional diagnostic x ray systems. The gray-levels at each step of the wedge on the nodule with respect to the background were measured and plotted against the thickness of the wedge. Preliminary results show that the removal of the noise bits do not affect the shape of the curve and thus the detectability of the nodule.[[department]]醫環