Texture analysis of ultrasound images of livers
Klaus Juel Olsen
It is interesting to compare the results previously obtained and reported
in the literature by other research groups and the results in this project.
However, one must be very careful when making direct comparisons because
many things in the design and analysis may differ.
We have focused on the differentiation between normal liver images and images
from livers with diffuse diseases.
For this two group situation the computerized analysis produces hit rates
ranging from about 50% to more than 80%. Lerski et al. obtained considerably
higher hit rates (83-94%) when differentiating two group situations without
mixed cases. However, the statistical treatment of the data must be criticized.
The discriminations were neither performed jackknifed nor with calibration and
test data set. Furthermore, the reported hit rates seem to be obtained as the
maxima of all possible parameter combinations of the eight parameters with
highest univariate discriminating capability.
The statistical treatment of the results in Raeth et al. is far better, but
one problem is not considered properly. Since they use three images from each
liver, the results will be biased, even when they use a jackknifed
discrimination. However, the results are good. The overall hit rate, for discriminating
between the diffuse diseases fat, hepatitis, cirrhosis/fibrosis and a
situation of mixed fat and cirrhosis/fibrosis, is 80%.
Keeping the differences in statistical methods in mind, the results of the
computer analysis in the liver project are quite acceptable. The performance in
the visual evaluation lies within the range of the reported experiments.
The small superiority of the computer analysis (d-type images) as compared to
the visual evaluation, is found in this project as well as in other projects
(Raeth et al.)
Since the computer analysis of ultrasound images performs at least as well as
the visual evaluation of the images, the combination of the two approaches
is likely to improve the precision of the diagnoses. However, the calibration
problems with the BK1846 scanner influenced the present dataset so it is not
adequate for the design of a final system. In the construction of a final
system the following quidelines are advisable from the experiences in this
- Simultaneously with the recording of the patient images an image of a
phantom should be recorded. The phantom image must in the computer
analysis be used to calibrate for fluctuations in the scanner
- The application of more than one image may improve the precision of the
diagnoses. However, the more correlated the images are, the less
improvement will be obtained in the diagnoses. In this study a combination
of the images from one patient did not yield substantial improvements
in the hit rates. Thus it is recommendable to record only one image from
each patient. The type d image, a scan of the right liver lobe, gives the
best overall hit rate and should be used if only one image is recorded
from each patient.
- The interactive drawing of the contours of the interesting regions is
recommendable. In general, it has not been possible to apply the
informations from the inhomogeneous parts of the liver in this project.
This information is important in visual evaluation of a liver image,
but it is apparently difficult to extract the information automaticly.
If the inhomogeneous parts are used, the drawing of line between
homogeneous and inhomogeneous parts must be done very carefully because
the inhomogeneous parts usually are small.
- There is no significant differences between the two types of contour
settings. Thus the standard, which is contour three, may be applied.
- The histogram parameters and the cartesian GLCM parameters seem to
contain a very large part of the texture information in the images.
A reduction to this set of parameters allows a fast calculation and
IMSOR Ph.D Thesis 51, 1988
Last modified August 18, 1996
Finn Kuno Christensen
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