Original Jpn J Radiol Technol 2000 ;
Temporal Subtraction Technique for Detection of Subtle Anomalies
on Temporally Sequential Bone-subtracted Chest Radiographs
by Energy Subtraction

SHIGERU SANADA, TAKESHI KOBAYASHI,1) MEGUMI YOSHIDA, 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. 11, 2000; Code Nos. 532, 254
Summary
We developed a temporal subtraction technique for the detection of subtle anomalies on temporally sequential bone-subtracted chest radiographs(soft tissue images)by energy subtraction. To recognize the temporal changes in a current soft tissue image in comparison with those in a previous soft tissue image, we attempted to enhance the changes by a difference image processing technique. The lung markings were enhanced by the first derivative filter. The image registration for the lung markings on both images by the sequential similarity detection algorithm(SSDA)method was then employed. The soft tissue image provided by the energy subtraction technique was excellent in its detection of subtle abnormalities in the lung, and this method was able to detect subtle abnormalities such as infiltrates and nodules missed in screening. It was suggested that this temporal subtraction technique improves accuracy when radiologists diagnose soft tissue chest images by x-ray energy subtraction.
Key words: Computer-aided diagnosis, Temporal subtraction, Energy subtraction, Image processing, Chest radiography