Original Jpn J Radiol Technol 2000 ;
Automated Image Registration by Matching of Lung Markings on Temporally Sequential Chest Radiographs for Temporal Subtraction Technique

SHIGERU SANADA, HIROSHI SATOU, TAKESHI KOBAYASHI,1) TAKESHI MATSUI,2)
and TSUTOMU TAKASHIMA1)
Department of Radiological Technology, School of Health Sciences, Kanazawa University
1)Department of Radiology, Kanazawa University School of Medicine
2)Department of Radiology, Kanazawa University Hospital
Received Nov. 4, 1999; Revision accepted Jan. 8, 2000; Code Nos. 532, 254
Summary
We examined a method using the image registration of previous and current chest radiographs for the temporal subtraction technique. Lung markings that traversed the lung substance were assigned as landmarks for image registration. The first derivative filter was employed to emphasize lung markings. To remove costal shadows that were emphasized simultaneously, edge gradients and connectivity in the horizontal
direction were analyzed. Previous and current images in which the costal shadows had been deleted and only the lung marking shadows were emphasized were matched by a sequential similarity detection algorithm. The temporal subtraction images, from which a more normal structure was suppressed by this new registration technique, and the morbid temporal changes in 4 of 13 cases(31%)were better enhanced than with the previous method.
Key words: Computer-aided diagnosis, Temporal subtraction, Image processing, Chest radiography