Sequential Subtraction Change Detection

Computer programs are under development to enhance the detection of changes from one film to the next as a method to aid radiologists in their detection of disease [31,32]. The processes involved include warping, registration, and subtraction. Because most nonobvious disease occupies only a small portion of the chest, the algorithms which function on the whole chest can warp one image to match the other in spatial dimensions, register them, and subtract them, enhancing only the area that showed local change (Fig. 13). These techniques are still relatively immature and experimental, but it is likely that they will become commonly used in the future.

Figure 13 Sequential subtraction used to aid detection of lung nodule. (a) The lung apex 1 year before b was taken. (c) The subtraction image obtained after the images have been warped and registered. This subtraction image shows (as a white region) a change between the two films, which represented a small non-small-cell lung cancer projected over the first-rib calcified cartilage. (Experimental work of the author, S. C. B. Lo, and H. Zhao.)

Figure 13 Sequential subtraction used to aid detection of lung nodule. (a) The lung apex 1 year before b was taken. (c) The subtraction image obtained after the images have been warped and registered. This subtraction image shows (as a white region) a change between the two films, which represented a small non-small-cell lung cancer projected over the first-rib calcified cartilage. (Experimental work of the author, S. C. B. Lo, and H. Zhao.)

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