A Photogrammetric Method for Measuring Breathing Movements ˇ ara1 , Vladim´ır Smutn´y1 , Michaela Veverkov´a2 , Jiˇr´ı Cumpel´ ˇ Radim S´ ık3 1
Center for Machine Perception, Department of Cybernetics Faculty of Electrical Engineering, Czech Technical University, Prague
[email protected] 2
Department of Rehabilitation Medicine Postgraduate Medical School, Prague 3
Department of Physiotherapy Faculty of Physical Education and Sports, Charles University, Prague Abstract. A photogrammetric method for measuring general motions is used to show that it is possible to measure quantitative parameters related to breathing movements of a human body. In a feasibility test we succeeded to relate the observed measurements with a biomechanical breathing model. The proposed setup allows for a non-contact, instantaneous measurement that constrains neither the subject nor any additional measurements. This opens a possibility to improve the diagnosis of breathing disorders.
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Introduction
The goal of this feasibility study was to test the accuracy and repeatability of photogrammetric measurement for reliable measurement of human breathing movements. This is a preparation stage for a clinical study aimed at quantitative evaluation of rehabilitation treatment efficiency.
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Materials and Method
Only one subject was measured in this experiment. The subject underwent a special training course. In an independent clinical examination his breathing was fully consistent with the theoretical description of inspiration [2]. To measure breathing movements we tracked spatial positions of artificial markers located on the subject’s body surface, see Fig. 1. In total, 40 markers were used, 20 per dorsal and 20 per ventral side of the body. Non-breathing movements were neither registered nor compensated for. Data was acquired by four-camera photogrammetric system, see Fig. 2. All cameras were fully calibrated. Simultaneous camera exposure helped eliminate motion artefacts during image acquisition. Marker centers were then semi-automatically detected with the resolution of 1/50 pixel in 760 × 484 images. This information was used to reconstruct the spatial positions of all marker centers by triangulation method. The resulting measurements have the effective resolution of 0.1mm. For breathing description the difference of distances between each horizontal pair of outer markers (e.g. 1–4, 5–8, etc.) was compared in expiration and inspiration phases. This was
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Figure 1: Marker placement.
Figure 2: Camera system used in the experiment. done independently for the ventral and dorsal sides of the body. Distance differences were used to eliminate non-breathing movements at the cost of emphasizing the latero-lateral chest wall movements. Measurements for four types of inspiration were obtained: normal, abdominal, costal, and subclavial.
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Results and Discussion
The results are shown in Tab. 1. From the measurements it was possible to interpret the breathing pattern of the subject in agreement with the theoretical description of four basic types of inspiration [4]. It is clear, however, that the superficial marker location follows skin motions rather than rib motions. Our measurement suffices to derive the rib motions, however. Even though the tested method gives only indirect measurement of breathing movements, it is possible by comparison of measured data with biomechanical breathing model to evaluate the function of the diaphragm, deep intrinsic spine muscles and musculus transversus abdominis. This evaluation would be difficult to achieve in routine clinical examination. Objective methods based on ultrasonography, skiagraphy, and magnetic resonance are not used in the clinical praxis in the Czech Republic. Skiagraphy stresses the patient by X-ray exposure and magnetic resonance imaging is too costly. Our method is relatively cost- and time-efficient and has a sufficient diagnostic value. The proposed method opens new possibilities in breathing diagnosis.
Table 1: Measured movements in mm averaged over the five horizontal pairs.
inspiration type normal
abdominal
costal
subclavial
motion direction latero-lateral cranio-caudal dorso-ventral latero-lateral cranio-caudal dorso-ventral latero-lateral cranio-caudal dorso-ventral latero-lateral cranio-caudal dorso-ventral
ventral side dorsal side inner outer inner outer markers markers markers markers 1.5 11.2 7.5 18.7 −0.2 −0.7 0.0 1.7 1.4 4.6 −1.0 −3.5 1.8 10.1 6.6 17.1 −0.6 −2.6 −0.2 0.4 −1.5 −5.7 −0.3 −0.8 1.9 13.4 8.3 21.7 −0.1 −1.2 0.1 2.2 1.0 0.2 −0.7 −2.0 1.3 11.8 7.9 19.8 0.4 1.0 −0.4 0.2 0.8 1.3 −0.4 0.5
Acknowledgement This work has been supported by the Czech Ministry of Health under project NN6333-3/2000 and by the Czech Ministry of Education under project MSM 210000012.
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