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Fig. 3 Left Calibration vest worn by the patient and the positioning system used at the Sainte-
Justine Hospital. The calibration vest has embedded radio-opaque markers visible on the biplanar
to self-calibration the scene using
fiducial points closer to the patient
s skin. Right Positioning
'
system to minimize patient motion between biplanar acquisitions
In order to facilitate the 3D reconstruction of scoliotic trunks, algorithms based
on the explicit modelling of calibration matrices were used to calibrate the X-ray
scene [
7
,
8
]. However, this particular system required for the patient to be placed in
a
fixed positioning system while wearing a calibration vest during the radiographic
acquisition (Fig.
3
), necessitating calibrated images in order to obtain the 3D
reconstruction of the spine. Because of the inherent limitations of the system used
for research purposes, it became clear such a device could not be deployed in other
clinics and thereby exploiting the bene
ts of 3D reconstruction of the spine. This
ultimately limits the universal access to such a technology in a routine setting to
assess spinal deformations in 3D.
2.2 New Generation of 3D Reconstruction Systems
The ionization dose given to the patient using conventional radiography in not
negligible, and can ultimately induce a risk of cancer or leukaemia with repetitive
acquisitions [
53
], in addition to offer images of average quality. A low-dose
imaging system based on the invention of Georges Charpak (1992 Nobel prize of
physics [
5
]) was developed by EOS imaging (Paris, France) to generate high-
quality radiographic images, while considerably reducing ionization doses. A
rst
evaluation of the prototype was conducted at the St-Vincent de Paul Hospital in
Paris in 1995. Improvements to the system were introduced in order to increase the
resolution and reduce the image acquisition time due in part to the new technologies
in radio-sensitive detectors. The EOS system (Fig.
4
) can acquire simultaneously
biplanar radiographic images and includes a software (sterEOS) to perform the
reconstruction of bony structures. This system is now installed in over 30 countries,
including the US, Canada and Germany.
