ASSERT

Developer

The School of Electrical and Computer Engineering at Purdue University, West Lafayette.

URL

The homepage is at http://rvl2.ecn.purdue.edu/~cbirdev/WWW/CBIRmain.html, an interactive demo is at http://rvl2.ecn.purdue.edu/~cbirdev/WEB_ASSERT/assert.html.

References

[SBK⁺99]

Features

A physician delineates a pathology bearing region (PBR) in images. A lobular feature set (LFS) is associated to a lobe or a combination of adjacent lobes. A LFS contains 26 features of PBRs adjacent to the lobular boundary, and 26 features of PBRs interior to it. The features of each PBR include 14 perceptual features that are specific for HRCT lung images, grouped into linear and reticular opacities, nodular apacities, high opacities, and low opacities. In addition, from 255 general purpose features, a sequential forward selection algorithm selected 12: five grey level, five texture, and two shape features. The grey level features are the grey level mean and standard deviation, and bins 6 ,9, and 16 from a 16-bin histogram. The texture features are contrast, entropy, homogeneity, and cluster tendency, all derived from the grey coocurrence matrix, and the edginess, the ratio of the number edge pixels to the number of pixels in the PBR. The shape features are area, and distance from the PBR region to the enclosing lobular region boundary. The distribution of the 52-dimensional feature vectors is partitioned into 46 LFS classes.

Querying

A physician delineates a PBR in the query image, from which the features vector is computed.

Matching

The distance between two feature vectors is the Euclidean distance.

Indexing

The 52-dimensional feature space of the LFSs is devided into bins. Each LFS is converted into a hash index by the multi-hash method [GK95]. The index points to the appropriate bin containing pointers to one or more LFS classes.

Result presentation

The four best matching images are shown.

Applications

Assert is a specifically targeted towards retrieval of high resolution computed tomography images of the lung.