Logarithmic simulated annealing for X-ray diagnosis

  • Authors:
  • A. Albrecht;K. SteinhöFel;M. Taupitz;C. K. Wong

  • Affiliations:
  • Department of Computer Science and Engineering, CUHK, Shatin, N.T., Hong Kong;GMD-National Research Center for Information Technology, Kekuléstr. 7, 12489 Berlin, Germany;Faculty of Medicine, Institute of Radiology, Humboldt University of Berlin, Schumannstraíe 20/21, 10117 Berlin, Germany;Department of Computer Science and Engineering, CUHK, Shatin, N.T., Hong Kong

  • Venue:
  • Artificial Intelligence in Medicine
  • Year:
  • 2001

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Abstract

We present a new stochastic learning algorithm and first results of computational experiments on fragments of liver CT images. The algorithm is designed to compute a depth-three threshold circuit, where the first layer is calculated by an extension of the Perceptron algorithm by a special type of simulated annealing. The fragments of CT images are of size 119x119 with eight bit grey levels. From 348 positive (focal liver tumours) and 348 negative examples a number of hypotheses of the type w"1x"1+...+w"nx"n=@q were calculated for n=14161. The threshold functions at levels two and three were determined by computational experiments. The circuit was tested on various sets of 50+50 additional positive and negative examples. For depth-three circuits, we obtained a correct classification of about 97%. The input to the algorithm is derived from the DICOM standard representation of CT images. The simulated annealing procedure employs a logarithmic cooling schedule c(k)=@C/ln(k+2), where @C is a parameter that depends on the underlying configuration space. In our experiments, the parameter @C is chosen according to estimations of the maximum escape depth from local minima of the associated energy landscape.