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A new method of using in vivo X-ray images of the skull
during photo superposition with the image of the skull.
Alexey Abramov
Russia, Moscow
• INTRODUCTION
• The goal of this presentation is to demonstrate new ways of using in vivo X-ray images for the procedure of craniofacial identification. This newly proposed method uses an adjusted outline-projection technique of a photograph of an unknown skull in order to facilitate comparison to a known radiograph and to account for X-ray distortion of the radiographic images. We suggest a number of potential problems arising during such comparative processes, as well as ways of approaching these hindrances.
X-ray images can be grouped as follows: local images (showing isolated parts
of a skull), panoramic images of teeth and general dentition, and complete shots
of a head (see pictures 1-3).
Picture 1. An example of a local image (three teeth are shown).Picture 2. An
example of a panoramic image (all the teeth of the upper and lower jaws are
shown).Picture 3. An example of a panoramic image of the head (a frontal
projection).
Typically the data obtained from studying radiographs are used to form
dental status of an unknown individual and compare the two
radiographic images. As these methods are widely known and
generally applied, they are not described in this review. Instead, here
we are concerned more with a unique approach to skull-photo
superimposition, using a form of radiographic comparison.
This method has proved to be especially useful in scenarios where the
skulls of unknown individuals were partly destroyed which caused
some difficulties for applying the traditional methods of superposition to
the complete skull for purposes of identification.
There were 20 cases and some experimental studies used to develop
this method.
In the process of developing this method has been used three-
dimensional visualization software system “TADD” (developed by: Abramov S.,
Boldyrev N., Bannikov A.).
• Other cranial features such as the sinuses
are easy to distinguish on high resolution
images and should thus be included as
they are generally considered unique
(Christensen 2005).
• However, one must take into account the differences of the projection distortion of the radiograph, using two steps. (1) The outlines of the skull should be compared – the calvarium contours and the side contours of the lower jaw and then (2) one should compare the contours of the facial bones and the chin. After this general sizing, the unique outlined features can easily be compared in projection and areas of distortion noted from the two-step process can be accounted for and ignored from the identification analysis.
• The process of applying this method is
very effective though not labor-intensive
for facilitating superimposition
identifications. In such cases the
comparison of identified and identifying
objects is based upon taking into account
the combination of separate small features
and with the use of the method of photo
superposition of skull contours.
• Thus the objects which are farther from the radiograph become distorted by appearing much larger in the final image. For instance, when a patient is laid with his face down, the facial skeletal elements are represented more true-to-life and the back sections of the skull are more distorted. Thus we divide such an X-ray image into two zones:
• 1) Representation of the back “layer” of the frontal projection of the skull – the skull outline and
back sections of the lower jaw are increased to a significant degree.
• 2) Representation of the front “layer” of the frontal projection of the skull – the face bones contours are minimally distorted.
• In each of these zones the X-ray contours represent the proportions of the so-called skull “layer” elements rather precisely to enable the procedure of their comparison with the contours of the same skull “layer” of the skull image.
See the results of the skull contours and the radiograph
superposition carried out in two steps
Finally, it should be noted that when CT scanning and NMR methods are used,
there is little if any projection distortion in the images which need be taken into
account during the procedure of photo superposition.
• Now you will see several examples of
using two-step photo superimposition
procedure.
• Picture 17. The X-ray image with the contours of the calvarium and trepanation defect of Mr. M. in the right profile projection.
• Picture 18. The skull image with the contours of the calvarium and trepanation defect in the right profile projection.
• Picture 19. The superimposition of the skull contours of the two images..
• Picture 20. The X-ray image with the contours of the calvarium and trepanation defect of Mr. M. in the frontal projection.
• Picture 21. The skull image with the contours of the calvarium and trepanation defect in the frontal projection.
• Picture 22. The superimposition of the skull contours of the two images.
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