Abstract
Fast localization of organs is a key step in computer-aided detection of lesions and in image guided radiation therapy. We developed a context-driven Generalized Hough Transform (GHT) for robust localization of organ-of-interests (OOIs) in a CT volume. Conventional GHT locates the center of an organ by looking-up center locations of pre-learned organs with “matching” edges. It often suffers from mislocalization because “similar” edges in vicinity may attract the prelearned organs towards wrong places. The proposed method not only uses information from organ’s own shape but also takes advantage of nearby “similar” edge structures. First, multiple GHT co-existing look-up tables (cLUT) were constructed from a set of training shapes of different organs. Each cLUT represented the spatial relationship between the center of the OOI and the shape of a co-existing organ. Second, the OOI center in a test image was determined using GHT with each cLUT separately. Third, the final localization of OOI was based on weighted combination of the centers obtained in the second stage. The training set consisted of 10 CT volumes with manually segmented OOIs including liver, spleen and kidneys. The method was tested on a set of 25 abdominal CT scans. Context-driven GHT correctly located all OOIs in the test image and gave localization errors of 19.5±9.0, 12.8±7.3, 9.4±4.6 and 8.6±4.1 mm for liver, spleen, left and right kidney respectively. Conventional GHT mis-located 8 out of 100 organs and its localization errors were 26.0±32.6, 14.1±10.6, 30.1±42.6 and 23.6±39.7mm for liver, spleen, left and right kidney respectively.
