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MEDPHOS : 
A NEW PHOTOGRAMMETRIC SYSTEM FOR MEDICAL MEASUREMENT 
A. Malian *, A. Azizi ?, F.A. van den Heuvel ^ 
* Department of Surveying Engineering, University of Tehran, Iran 
R Department of Geodesy, Delft University of Technology, The Netherlands 
malian(@ut.ac.ir ; aazizi@ut.ac.ir ; F.A.vandenHeuvel@lr.tudelft.nl 
Commission V, WG V/3 
KEY WORDS: Close Range, Biometrics, Algorithms, Design, Detection, Optical 
ABSTRACT: 
A multi-camera close range photogrammetric system for robust and precise measurement of human body surface in general and three 
dimensional evaluation of bedsores in particular has been designed and constructed. MEDPHOS (MEDical PHOtogrammetric 
System) consists of four digital synchronized cameras the optical axes of which are convergent in a pre-specified point. A light 
projector is fixed in the center of the cameras-carrying rig. The projector serves as a texture provider that projects a special pattern on 
the surface to be measured to compensate for the lack of texture in human body surface. Determination of shape, size, and density of 
the pattern dots was also investigated. The proposed algorithm consists of the following steps: Both cameras and projector were 
calibrated so that the positional and orientational parameters of the entire system are known. A new method for image segmentation 
and thresholding using morphologic operators was used for the detection of the projected pattern dots from the uneven background of 
the images. A watrershed transformation was also applied to tackle the problem of overlapping pattern dots. Then to reduce the 
effects of specular reflection of light due to the humidity of the object (in the case of wounds), a novel homomorphic transformation 
was developed and applied to the images. After segmentation of the images, connected component labeling procedure was used to set 
up the actual matching points. The centroids of these components were precisely calculated. Intensity-based image matching had 
already been tested that - due to great deviation from the Lambertian assumption necessary for solving the correspondence problem - 
did not give satisfactory results. So, a new algorithm based on four focal constraint has been developed that makes it possible to carry 
out the matching procedure without being dependent on intensities of the pixels and without a need for approximate values of the 
unknowns. This robust and ever valid geometric constraint is found to be very effective with non ambiguous results provided the 
necessary conditions for the system configuration are met. The fourth camera and the calibrated projector- that is treated like an 
active camera- serve as additional sources of information for consistency checking of the results. Almost all kind of information in 
the filed of biometrics can be obtained rapidly, robustly, and easily using MEDPHOS. 
1. INTODUCTION three dimensional information of anatomic structures and their 
deformations and displacements in time. It can record the shape 
and size in studies relating to a wide range of areas of the 
human body, such as torsos, heads, faces, limbs, breasts, feet, 
skin, eyes and teeth. Some of the applications have been for 
purpose of advancing anatomical studies, while others have 
related to the detection or treatment of diseases. 
Opportunities for such measurement relate primarily to: 
e Detection of medical conditions. 
The specific problem treated in this paper is to introduce a new 
system for the measurement of the location of human body 
points. Photogrammetry has a distinct value as a medical 
measurement tool since it uses photography, which offers a 
quick, convenient, non-contact and safe means of recording a 
condition at a particular point in time. It is not invasive, and 
touching the patient, with risk of hurting or infecting, can be 
usually avoided. Further, photography does not distort the e Treatment of a disease or condition. 
surface being measured. Photogrammetry can be contrasted e Study into the anatomical aspects of human body. 
with other external measurement techniques, such as those e Research into diseases and their treatment. 
involving electrogoniometers and accelerometers attached to the 
body for movement analysis, which are not only uncomfortable 
but can interfere with the free movement of the patient 
(Atkinson, 1996). 
2. MEDICAL PHOTOGRAMMETRY 
The term photogrammetry covers the whole range of metrology 
activities that exploit geometric processes based on image 
acquisition and image processing. As stated by (Mitchell and 
Newton, 2002) "The history of attempts to apply 
photogrammetry to the measurement of the human body is 
almost as long as the history of photogrammetry itself. Close 
range photogrammetry can be effectively used for measuring 
biological forms and functions as well as shapes, locations and 
Although photogrammetric measurement is particularly relevant 
to orthopaedics and anatomy, it can also contribute to 
ophthalmology, neurology, dentistry, occupational therapy, 
ergonomic studies and many other areas related to human 
health. The users of the results may be involved in health in 
various ways, as medical researchers, surgeons, clinicians, 
biomechanical engineers, and so on”. In the past, the 
disadvantage of sing photogrammetric methods based on 
analogue photographs and systems was that they required an 
experienced observer to view and measure the photographs in 
an expensive stereoplotter. This was clearly unsatisfactory for a 
clinical situation. The advent of digital photogrammetry has 
overcome this difficulty, but in the meantime it can be argued 
that several of other optical methods have been more quickly to 
an operational stage than the photogrammetric methods (Figure