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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