Simultaneous Viewing Of Lung And Heart CT Images Employing Automated Histogram Modification

Computerized Tomography (CT) images reflect the x-ray absorptive properties of the patient. CT images of the chest region, however, are difficult to display. Due to the large density differences between the tissue region of the heart and the air filled region of the lung, the lung appears nearly black if the heart is viewed at normal contrast. Similarly, if the image is adjusted to view the lungs at reasonable contrast, the heart region becomes saturated and featureless. A standard technique for viewing the two regions remaps the darker lung gray-level to values comparable to that of the heart region. The "dark-line artifact" results for those pels of intermediate value between the heart and lung. This apparent line surrounds the lungs and gives the entire image an objectionable piecemeal appearance. A software system, CTIP, written in FORTRAN is discussed which remaps CT image gray-level so that both the lung and heart regions are clearly visible with a more natural anatomical appearance. The system is adaptive to image statistics derived from the gray level histogram and is completely automated. The processed and the standard approach images were compared by twenty-two radiologists with 82% preferring the processed images. All of the respondents agreed that the processed images possessed a more anatomical appearance than the standard approach.