image recognition andthe reconstruction of cleft palate
TRANSCRIPT
Image Recognition and the
Reconstruction of Cleft Palate
Histological Preparations:
A New Approach
MICHAEL |. SIEGEL, B.A., Ph.D.
JOHN S. TODHUNTER, B.S M.S.Pittsburgh, Pennsylvama 15260
Serial coronal Aistological sections of cleft palate and normal 12 week fetal specimens are
video scanned. The digitized data in a matrix of 10° data points are recorded and through
computer manipulation three dimensional reconstructions are produced. These can be resec-
tioned by computer in various planes to expose any given structure for study. This is the
first application of such a technique to these problems.
An understanding of the role of the mam-
malian nasal septum in midfacial growth has
been of interest to anatomists and craniofacial -
biologists for over a century (Fick, 1857, Scott,
1953, Sarnat, 1970). One of us has extended
this work to non-human primates (Siegel,
1972, 1974) and has also discussed the impli-
cations ofseptum-mediated growth for cleft
palate repair (Siegel, 1976, 1978). Although
- extensive histological examination of cleft and
normal human fetal material has been carried
out (Kraus et al., 1966), the relationship of the
cartilagenous septum to the other structures
of the face has not been investigated in such
specimens. A knowledge of these relationships
is critical to an understanding of abnormal
growth and development in patients who
have undergone cleft palate repair as well as
to an understanding of the pathogenesis of
various types of facial anomalies. While wax
reconstructions from histological preparations
have been used since the late 19th century to
investigate the gross relationships of specific
structures, such studies lose much information
and are of a limited nature. The obvious need
for the information, as well as a better method
Dr. Siegel is affiliated with the University of Pitts-
burgh Cleft Palate Center, Department of Anatomy and
Cell Biology, Department of Anthropology, Pittsburgh,
PA 15260. Mr. Todhunter is a teaching fellow in the
University of Pittsburgh, Department of Electrical En-
gineering, School of Engineering, Pittsburgh, PA 15260.
This paper was supported in part by NIH Research
Grant DE-01697-16, The National Institute of Dental
Research..
381
for obtaining such data, led us to explore the
latest advances which have been instigated by
space age technology. Borrowing the concept
of "CAT scans" or "CT" scans (computerized
tomography) which allow for computer gen-
erated images ofhuman cross-sections and the
advanced techniques of image recognitionand three-dimensional reconstruction, thepresent research has begun to record andutilize that technology in studying histologi-cal preparations.
Computerized techniques for reconstruc-tion of three-dimensional structures from acollection of cross-sections have centered inthe area of computer-aided tomography(Eden, 1978) and in the past have relied onrelatively small data sets. The typical recon-struction program consists of four stages: datarepresentation and preprocessing, imagealignment, interpolation, and presentation.The first of these four steps involves conver-sion of analog image data (e.g. photographsor slides) into a quantized digital form. Quan-tized images are oftentimes subjected to someform of preprocessing in order to clean ran-dom noises introduced by the digitizationprocess, to adjust for adverse lighting condi-tions, or to enhance contrast or other features.Correction for collapsed tissue is also a possi-bility (Rosenfeld and Kak, 1976).
Since digitized sections may not be properlyaligned for direct reconstruction, an algo-rithm to stack consecutive slices must be ap-plied. Two approaches to alignment have ap-peared in the literature: one attempts to min-
382 Cleft Palate Journal, October 1979, Vol. 16 No. 4
imize a measure of dissimilarity between sec-
tions by rotation and translation of the sec-
tions (Chow and Hsi, 1978), another identifies
structural features common to adjacent sec-
tions and aligns sections based upon geo-
graphic location of the chosen features (Bajesy
and Winston, 1978). The mechanics of recon-
struction can be very simple once images are
aligned-any type of interpolation between
sections (piece-wise linear, polynomial regres-
sion, or spline fits) may be used to recover
inter-slice data. Finally, the interpolated data
may be displayed upon a television monitor
or gray-scale plotter. The problems of align-
ment of serially sectioned curved structures
have also been dealt with in a separate report
(Todhunter and Li, in press).
Methods
Twenty u serial sections were prepared from
two 12 week fetal specimens, one with bilat-
eral cleft palate and one normal. These spec-
imens, their preparation and staining are de-
scribed in detail in Kraus et al., 1966. One to
one (1:1) black and white negatives were
made of each slide (approximately 100 per
specimen) (by one of us) utilizing a high
resolution process lens and these were en-
larged on 4 X 5 film and reversed to produce
a large, positive, black and white image of
each section. These films were then subjected
to a video scan with a matrix of 1024 X 1024
data points. This scan assigned a value on a
black (0) and white (255) scale of 0-255 to
each point in the matrix of 10° points. Gray
scale histograms were normalized between
sections by a combination of averaging and
gray scale shift. Interpolation between adja-
cent sections across all 100 sections with such
a scan requires approximately 10° individual
curve fits and access to all the 10° data points.
One of us (Todhunter, in prep.) is developing
an efficient technique implemented on a mini
computer which considerably reduces the
computational complexity of the reconstruc-
tion. Presently, the programs for reconstruc-
tion are being developed and tested on our
PDP11/55 mini computer.
Results
Thus far, our efforts have been in the prep-
aration of scannable photos and the digitiza-
tion and display of the data. Examples of a
computer generated display of one section can
be seen in Figure 1 (each of 64 colors repre-
sents a segment of the gray scale). Since our
primary interest is presently in the septum
and associated structures, this area can be
enlarged (ten times the size of the scanned
image without significant distortion) and en-
hanced (Figure 2). (Each of 64 colors repre-
sents a segment of the gray scale). To view the
structure in a sagittal projection the program
displays an image rotated 90° about the Y
axis (Figure 3). At this stage of the research,
the rotation is utilizing only a fragment of the
available data so that further sectioning in
alternate planes has not yet been carried out.
After stacking and interpolation a three di-
mensional image can be produced (Figure 4).
Reconstructed data represent an approxi-
mation of the continuum comprised of the
slices derived from given sections. As such,
views of internal structures may be easily
generated and viewed from any angle (e.g.
sagittal cuts) by choosing points lying on a
specific cutting plane. Our current software
can produce rotations of these cuts and ex-
ploded views for more detailed study of the
relationships between internal structures.
While our study focuses specifically upon
the palate and associated structures, data
taken from a collection of good quality histo-
logical preparations may be utilized in studies
of many other portions of the craniofacial
complex.
FIGURE 1. Computer generated image of 204 coro-nal section through twelve week fetal head (normal).
Siegel and Todhunter, crert racate imaAGE RECOGNITION 383
FIGURE 2. Computer enlarged and enhanced imageof septal region from Figure 1.
FIGURE 3. Septal region seen in 90° rotated com-puter generated image.
Summary
The need for a better understanding of the
relationships of various structures of the face
in normal and cleft palate fetal specimens has
led to the use of a new and unique computer
technology. Through the computerization of
histological data an infinite number of resec-
tionings may be performed. By altering the
viewing axis new structural relationships may
be viewed and analyzed. The present study
FIGURE 4. Stacked images, coronal three dimen-sional view.
documents for the first time the feasibility ofsuch an approach.
Reprints: Dr. Michael I. Siegel
Department of Anthropology
University of Pittsburgh
Pittsburgh, PA 15260
Acknowledgments: The authors would like tothank Dr. T. W. Sze for the use of the com-puting and image processing facilities of thePattern Recognition Lab, University of Pitts-burgh, and Dr. C. C. Li for advice and tech-nical assistance.
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