Computer-Aided Diagnostic (CAD) Scheme by Use of Contralateral Subtraction Technique. Application to Detection of Acute Cerebral Infarctions in Brain Computed Tomography (CT)

We developed a computer-aided diagnostic (CAD) scheme for detection of subtle image findings of acute cerebral infarction in brain computed tomography (CT) by using a contralateral subtraction technique. In our computerized scheme, the lateral inclination of the image was first corrected automatically by rotating and shifting. The contralateral subtraction image was then derived by subtraction of the reversed image from the original image. Initial candidates for acute cerebral infarctions were identified by multiple thresholding and image filtering. As the first step for removing false-positive candidates, 14 image features were extracted in each of the initial candidates. Halfway candidates were detected by applying a rule-based test with these image features. At the second step, 5 image features were extracted using the overlapping scale with halfway candidates in the slice of interest and the upper/lower slice images. Finally, acute cerebral infarction candidates were detected by applying a rule-based test with 5 image features. The sensitivity of detection in 74 training cases was 97.4% with 3.7 false positives per image. The performance of the CAD scheme for 44 testing cases had an approximately equivalent result to the training cases. Our CAD scheme using the contralateral subtraction technique can reveal suspected image findings of acute cerebral infarctions in CT images. (C) 2011 Wiley Periodicals, Inc. Electron Comm Jpn, 94(2): 32-41, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10299