Computers in Biology and Medicine 33 (2003) 119–142 www.elsevier.com/locate/compbiomed Automated lung outline reconstruction in ventilation–perfusion scans using principal component analysis techniques G. Serpen a ; * , R. Iyer a , H.M. Elsamaloty b , E.I. Parsai c a Department of Electrical Engineering and Computer Science, The University of Toledo, Toledo, OH 43606, USA b Department of Radiology, Medical College of Ohio, Toledo, OH 43614, USA c Department of Radiation Oncology, Medical College of Ohio, Toledo, OH 43614, USA Received 4 March 2002; accepted 24 September 2002 Abstract The present work addresses the development of an automated software-based system utilized in order to create an outline reconstruction of lung images from ventilation–perfusion scans for the purpose of diagnosing pulmonary embolism. The proposed diagnostic software procedure would require a standard set of digitized ventilation–perfusion scans in addition to correlated chest X-rays as key components in the identication of an ideal template match used to approximate and reconstruct the outline of the lungs. These reconstructed lung images would then be used to extract the necessary PIOPED-compliant features which would warrant a pulmonary embolism diagnosis. In order to evaluate this issue, two separate principal component analysis (PCA) algorithms were employed independently, including Eigenlungs, which was adapted from the Eigenfaces method, and an articial neural network. The results obtained through MATLAB TM simulation indicated that lung outline reconstruction through the PCA approach carries signicant viability. ? 2002 Elsevier Science Ltd. All rights reserved. Keywords: Pulmonary embolism; Ventilation–perfusion scans; PIOPED criteria; Principal component analysis; Articial neural network; Template matching 1. Introduction Pulmonary emboli occur as a result of venous thrombi (blood clots within veins) which dislodge from their original source and eventually create an obstruction once in the lung. Such emboli usually originate in the major veins of the lower extremities but can also originate from pelvic veins, veins of the upper extremities, and from the right heart itself. Upon dislodging from the source, * Corresponding author. Tel.: +1-419-530-8158; fax: +1-419-530-8146. E-mail address: gserpen@eng.utoledo.edu (G. Serpen). 0010-4825/03/$ - see front matter ? 2002 Elsevier Science Ltd. All rights reserved. PII: S0010-4825(02)00063-X