Recently, the development of the Computer Aided Diagnoses (CAD) systems has been rapidly remarked. As one of the CAD systems, temporal subtraction technique can emphasize the temporal changes of interested regions by subtracting a previous image from a current image. However, subtraction artifacts are still remained due to misregistration, which caused by the variation of pose and inhalation differences when a patient accepts CT inspection at different times. Therefore, high accurate registration technique between a previous image and a current image is necessary. The purpose of this paper is to propose a nonrigid warping algorithm in local image matching based on the feature-driven Free Formed Deformation (FFD). The proposal was performed on thoracic MDCT images and the satisfactory results were obtained.

The temporal subtraction technique as one of computer aided diagnosis has been introduced in medical fields to enhance the interval changes such as formation of new lesions and changes in existing abnormalities on deference image. With the temporal subtraction technique radiologists can easily detect lung nodules on visual screening. Until now, two-dimensional temporal subtraction imaging technique has been introduced for the clinical test. We have developed new temporal subtraction method to remove the subtraction artifacts which is caused by mis-registration on temporal subtraction images of lungs on MDCT images. In this paper, we propose a new computer aided diagnosis scheme for automatic enhancing the lung nodules from the temporal subtraction of thoracic MDCT images. At first, the candidates regions included nodules are detected by the multiple threshold technique in terms of the pixel value on the temporal subtraction images. Then, a rule-base method and artificial neural networks is utilized to remove the false positives of nodule candidates which is obtained temporal subtraction images. We have applied our detection of lung nodules to 30 thoracic MDCT image sets including lung nodules. With the detection method, satisfactory experimental results are obtained. Some experimental results are shown with discussion.