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At least 145 records · Page 8Linked to original sources
PubMed1982

High density facial measurement: a new automated approach.

A brief summary of research undertaken into facial geometric measurement is furnished, emphasizing the potential of photogrammetric methods. The techniques described solves the long-standing problem of stabilization of the human head for repetitive longitudinal investigations. The basic geometric principles of terrestrial photogrammetry and digital imaging techniques are outlined, as the groundwork for a description of a fully automated method of obtaining a high density geometric delineation of sensitive surfaces by digital methods. The technique is appropriate for any medical purpose dealing with measurement and analysis of soft tissue surfaces, obviating, as it does, the need for head stabilization with its concomitant problems, and also in its provision of a databank capability.

Anthropometry↗
PubMed1987

Photogrammetric technique applied to anthropometric study of hands.

Being concerned with physical anthropometric dimensions to explore avenues of research on hands and their working strategies, a research study was made to develop a suitable method by using available photogrammetric resources. The paper discusses the optimums of details found by this study, viz., the use of a Wild C-40 stereometric camera (for obtaining stereoscopic photographs) and the use of a Wild A7 stereorestitution instrument equipped with digital data acquisition accessories (for obtaining all dimensional information). Three-dimensional data at 21 specific points and for nine specific distances were obtained on each hand of ten persons. Test observations indicate, inter alia, a dimensional accuracy of the order of +/- 0.3 mm obtainable through the working system. Cartographic presentations made in support of the digital data are found to be of help. This also permits to obtain additional data as may be necessary at times. Photogrammetry has the advantage of reducing and maintaining to a minimum all sorts of manipulations necessary in such studies.

Anthropometry↗
PubMed1991

Measurement of finger joint angles and maximum finger forces during cylinder grip activity.

Finger joint angles and finger forces during maximal cylindrical grasping were measured using multi-camera photogrammetry and pressure-sensitive sheets, respectively. The experimental data were collected from four healthy subjects gripping cylinders of five different sizes. For joint angles, an image analysis system was used to digitize slides showing markers. During the calibration of the camera system, both the nonlinear least square and the direct linear transform methods were applied and compared, the former providing the fewer errors; it was used to determine joint angles. Data were collected from the pressure-sensitive grip films by using the same image analysis system as used in the collection of the joint angle data. The method of using pressure-sensitive sheets provided an estimation of the weighted centre of the phalangeal forces. Results indicate that finger flexion angles at the metacarpophalangeal and proximal interphalangeal joints gradually increase as cylinder diameter decreases, but that at the distal interphalangeal joint the angle remains constant throughout all cylinder sizes. It was also found that most of the radio-ulnar deviation and the axial rotation angles at the finger joints deviate from zero, but the deviations are small. For the force measurement, it was found that total finger force increases as cylinder size decreases, and the phalangeal force centres are not located at the mid-points of the phalanges. The data obtained in this experiment would be useful for muscle force predictions and for the design of handles.

Biomechanical Phenomena↗
PubMed1994

Photogrammetric accuracy measurements of head holder systems used for fractionated radiotherapy.

PURPOSE: We describe how stereo photogrammetry can be used to determine immobilization and repositioning accuracies of head holder systems used for fractionated radiotherapy of intracranial lesions. METHODS AND MATERIALS: The apparatus consists of two video cameras controlled by a personal computer and a bite block based landmark system. Position and spatial orientation of the landmarks are monitored by the cameras and processed for the real-time calculation of a target point's actual position relative to its initializing position. The target's position is assumed to be invariant with respect to the landmark system. We performed two series of 30 correlated head motion measurements on two test persons. One of the series was done with a thermoplastic device, the other one with a cast device developed for stereotactic treatment at the German Cancer Research Center. Immobilization and repositioning accuracies were determined with respect to a target point situated near the base of the skull. The repositioning accuracies were described in terms of the distributions of the mean displacements of the single motion measurements. RESULTS: Movements of the target in the order of 0.05 mm caused by breathing could be detected with a maximum resolution in time of 12 ms. The data derived from the investigation of the two test persons indicated similar immobilization accuracies for the two devices, but the repositioning errors were larger for the thermoplastic device than for the cast device. Apart from this, we found that for the thermoplastic mask the lateral repositioning error depended on the order in which the mask was closed. CONCLUSION: The photogrammetric apparatus is a versatile tool for accuracy measurements of head holder devices used for fractionated radiotherapy.

Head and Neck Neoplasms↗
PubMed1995

The incorporation of partial shielding of the spinal cord in a tissue deficit compensator in radiotherapy of the thorax.

A method to determine the shape of a patient by placing radiopaque wires and chains on the skin and taking two isocentric X-ray films is described. The wire locations are reconstructed by X-ray stereo photogrammetry, and a beam's eye view of the wire frame structure can be obtained with reference to the original setup of the "stereo-pair" films. An algorithm for paving between the wires with triangular plates is described which allows the calculation of the tissue deficit distance and compensator thickness. The depth and distance to points on the spinal cord are calculated, and the dose rate is calculated using a standard irregular field computation program. The limit for spinal cord tolerance is specified in terms of the maximum daily dose based on an equivalent dose formula. The additional thickness of compensator, required for the posterior field compensator to satisfy the tolerance limit, is calculated. The technique readily accommodates the kyphotic and scoliotic spine and has been in routine clinical use for seven years.

Algorithms↗
PubMed2006

Correction of the nasal tip and columella in Koreans by a complete septal extension graft using an extensive harvesting technique.

The nose of most Koreans is characterised by a low nasal dorsum, retracted columella, and an acute columella-labial angle. For the surgical correction of the tip and columella, a complete septal extension graft, along with augmentation rhinoplasty has been developed. However, the use of this type of graft is frequently problematic because the septal cartilage is not large enough. In a study involving 10 cadavers, a complete septal extension graft was achieved in two of them by using septal cartilage harvested according to standard techniques. Therefore, the septal cartilage was harvested, leaving a 5-mm L-shaped strut, and a complete septal extension graft was implanted. The present report describes the results obtained in 34 patients and offers an analysis of the results as judged by the columella-labial angle and three proportional indices (nose height index, nasal bridge length index, and nasal tip projection index), measured by photogrammetry. The postoperative values obtained in these four categories increased significantly compared to the preoperative ones, thus confirming that the projection of tip was augmented, the nose was lengthened, and the columella was advanced caudally. Moreover, these positive outcomes were maintained during long-term follow-up, and no side effects, such as saddle nose deformity, were reported.

Adolescent↗
PubMed2006

The material properties of the native porcine mitral valve chordae tendineae: an in vitro investigation.

The material properties of the mitral valve chordae tendineae are important for the understanding of leaflet coaptation configuration and chordal pathology. There is limited information about the mechanical properties of the chordae during physiologic loading. Dual camera stereo photogrammetry was used to measure strains of the chordae in vitro under physiologic loading conditions. Two high-speed, high-resolution cameras captured the movement of graphite markers attached to the central section of the chordae. A uniaxial test simulating the same loading conditions was conducted on the same chordae using the same markers. The maximum strain experienced during the cardiac cycle was 4.29% +/- 3.43%. The loading rate was higher at 75.3% +/- 48.6% strain per second than the unloading rate at -54.8% +/- -56.6% strain per second. The anterior lateral strut chordae had a higher maximum strain (5.7% +/- 3.8%) and loading rate (80.5% +/- 51.9% strain per second) than the posterior medial strut chordae (5.5% +/- 2.3% strain and 68.1% +/- 48.3% strain per second). The posterior medial strut chordae had a higher unloading rate (-68.5% +/- -59.1% strain per second) than the anterior lateral strut chordae (-44.9% +/- -57.2% strain per second). Although the anterior lateral and posterior medial strut chordae have a significantly different diameter and length, they experience a similar strain, strain rate, and tension. In conclusion, a non-destructive technique was developed to measure in vitro chordal strain in the mitral valve. This technique allows the investigation of the behavior of biological tissues under physiologic loading conditions.

Animals↗
PubMed2006

Stereo image matching for facial feature measurement to aid in fetal alcohol syndrome screening.

The facial phenotype associated with fetal alcohol syndrome is identified through the measurement of facial distances and their comparison to population norms. As an alternative to time-consuming direct manual measurements, stereo photogrammetry has been used to obtain the required facial measurements from stereo digital photographs. While stereo photogrammetric measurement is faster, it requires manual marking of relevant facial landmarks on digital images. We present an algorithm that automatically finds matched feature points on the second of a pair of stereo images, after manual marking of the first. Standard image processing tools are used for preprocessing. Matching is based on a simple exhaustive search in an image window, with the sum of squared differences of the pixel intensities in the two images as the objective function. Eye measurements, namely palpebral fissure length, interpupillary distance, inner canthal distance and outer canthal distance, as well as distances that can be used to approximate the circularity of the upper lip, were obtained using the manual method of marking both images, and the method of automatic marking of the second image. Comparison revealed mean differences less than 1mm.

Anthropometry↗
PubMed1999

Structural anthropometric measurements for wheelchair mobile adults.

Structural anthropometric measurements for males and females were determined for the wheelchair mobile adults. A photogrammetry methodology was used to obtain the measurements. The various subject demographics including age, level or type of dysfunction as well as the specified anthropometric dimensions of the wheelchair mobile subjects were identified. The data would be useful for the design of industrial workstations for wheelchair mobile adults. Present workstation design principles based on seated able-bodied anthropometric measurements would not be suitable for this population.

Adult↗
PubMed2003

Explicit calibration method and specific device designed for stereoradiography.

The three-dimensional geometry of the human spine is noteworthy information that can be obtained by stereoradiographic methods. These methods are based on the identification of anatomical structures in several views which are obtained by rotation of a patient standing on a turntable. Calibration algorithms for computer vision or photogrammetry are well documented, but they generally yield calibration devices which are cumbersome for the use in clinical stereoradiography. This paper presents a calibration method adapted to a two-view stereoradiography calibration (frontal and lateral incidences) and based on a simplified geometric modeling of the radiological environment. The a priori knowledge yields four calibration equations related to the vertical and horizontal planes of both views, leading to a specific calibration procedure and device. Moreover this device is attached to the stereoradiographic system (directly integrated on the turntable) in order to facilitate clinical applications. A validation was performed on 26 dried lumbar vertebrae in order to evaluate clinical situation. The mean accuracy of the stereoradiographic reconstruction was 1.2mm.

Aged↗
PubMed1998

Skin movement artefact assessment and compensation in the estimation of knee-joint kinematics.

In three dimensional (3-D) human movement analysis using close-range photogrammetry, surface marker clusters deform and rigidly move relative to the underlying bone. This introduces an important artefact (skin movement artefact) which propagates to bone position and orientation and joint kinematics estimates. This occurs to the extent that those joint attitude components that undergo small variations result in totally unreliable values. This paper presents an experimental and analytical procedure, to be included in a subject-specific movement analysis protocol, which allows for the assessment of skin movement artefacts and, based on this knowledge, for their compensation. The effectiveness of this procedure was verified with reference to knee-joint kinematics and to the artefacts caused by the hip movements on markers located on the thigh surface. Quantitative validation was achieved through experimental paradigms whereby prior reliable information on the target joint kinematics was available. When position and orientation of bones were determined during the execution of a motor task, using a least-squares optimal estimator, but the rigid artefactual marker cluster movement was not dealt with, then knee joint translations and rotations were affected by root mean square errors (r.m.s.) up to 14 mm and 6 degrees, respectively. When the rigid artefactual movement was also compensated for, then r.m.s errors were reduced to less than 4 mm and 3 degrees, respectively. In addition, errors originally strongly correlated with hip rotations, after compensation, lost this correlation.

Adult↗
PubMed1999

Methodological and technological implications of quantitative human movement analysis in long term space flights.

In the frame of the 179-days EUROMIR '95 space mission, two in-flight experiments foresaw the analysis of three-dimensional human movements in microgravity. For this aim, a space qualified opto-electronic motion analyser based on passive markers was installed onboard the MIR Space Station. The paper describes the experimental procedures designed in order to face technical and operational limitations imposed by the critical environment of the orbital module. The reliability of the performed analysis is discussed, focusing two related aspects: accuracy in three-dimensional marker localisation and data comparability among different experimental sessions. The effect of the critical experimental set-up and of TV cameras optical distortions is evaluated on in-flight acquired data, by performing an analysis on Euclidean distance conservation on rigid bodies. An optimisation method for the recovering of a unique reference frame throughout the whole mission is described. Results highlight the potentiality that opto-electronics and close-range photogrammetry have for automatic motion analysis onboard orbital modules. The discussion of the obtained results provides general suggestions for the implementation of experimental human movement analysis in critical environments, based on the suitable trade-off between external constraints and achievable analysis reliability.

Algorithms↗
PubMed1991

Increased preferential optic disc asymmetry in ocular hypertensive patients compared with control subjects.

The authors determined asymmetrical differences in optic disc cupping and pallor between the right and left eyes of 57 control subjects and 75 patients with ocular hypertension. Photogrammetry was used to measure the optic disc cup, and computerized image analysis was used to measure the optic disc pallor for the total disc and its quadrants. Generally, for control and ocular hypertensive eyes, the median values of cupping and pallor were significantly larger in the left eye than in the right, except for depth in the inferior quadrant (right eye minus left eye = 9.3%, P = 0.000) and pallor in the nasal quadrant (right eye minus left eye = 21.3%, P = 0.01), which were preferentially larger in the right eye than in the left in ocular hypertensive eyes. Ocular hypertensive eyes also showed a greater difference between the right and left eyes compared with control eyes for inferior depth (P = 0.06) and nasal pallor (P = 0.02). Detection of optic disc differences as a sign of ocular hypertension between the right eye and the left should evaluate the inferior and nasal quadrants of the disc.

Aged↗
PubMed2000

Streifenlichttopometrie (SLT): a new method for the three-dimensional photorealistic forensic documentation in colour.

By means of the new method of Streifenlichttopometrie (SLT) it is possible to record the complete body surface of casualties in a practically photorealistic fashion, i.e. three-dimensionally and in colour. In comparison with the classic method of Photogrammetry Streifenlichttopometrie (SLT) is remarkably faster (10,000 points/s instead of 1 point/s) and in addition the colour of every point measured upon the corpse's surface is instantly recorded. Taking into consideration the resolution required and the qualities of the camera system the body surface is recorded in 'patches', i.e., areas of a defined extension (in the present case 500 mmx500 mmx200 mm) which are marked with a body fixed reference frame to grant the exact matching of the data after the recording process. Length, perimeter, square and volume of the body segments and injuries can be determined. Furthermore the natural colour of the wounds can be used for an immediate classification according to the intensity of the impact forces. In addition the 3-D coordinates of the body surface including the wounds can be transferred into an animated computer simulation for the reconstruction of the traumatic events.

Accidents↗
PubMed1995

A computerized non-invasive method for the assessment of human facial volume.

The three-dimensional coordinates of 22 standardized soft-tissue facial landmarks were used in the definition of a three-dimensional model of the adult human face. The model allows the estimation of the volume of the face in toto and of its parts (upper, middle and lower thirds, nose). Landmark coordinates were collected in 80 healthy young adults (40 men and 40 women selected according to criteria of dentofacial normality) by infrared photogrammetry by an automated instrument, and facial volumes calculated. Sample variability was larger in women than in men; the nose and the upper third of face had the largest variability regardless of gender. On average, all volumes computed in men were significantly larger than the corresponding values computed in women. Also the lower-to-middle third face ratio was significantly higher in men than in women. The sexual dimorphism in human facial volume did not involve the different parts of the face to the same extent: a large part of male facial volume preponderance was explained by the lower third of face. The proposed facial model could adequately represent the human face in all those research and clinical fields where noninvasive surface measurements could be employed alone or in support of conventional radiographic data.

Adult↗
PubMed2002

A stereo-photogrammetric method to measure the facial dysmorphology of children in the diagnosis of fetal alcohol syndrome.

In diagnosing a child with fetal alcohol syndrome (FAS), anthropometric measurements of the face are conventionally performed by highly trained dysmorphologists using a hand-held ruler. This renders the screening of large populations of children for the facial features characteristic of FAS very time-consuming and costly. This study proposes a new, cost-effective, and non-intrusive method to measure in three dimensions the facial dysmorphology of children using stereo-photogrammetry. The face of each child is photographed in a control frame simultaneously by a pair of high-resolution digital cameras mounted 1.04 m from the child and 0.26 m apart. Software has been developed to calibrate the images and to compute the three-dimensional object-space coordinates of any point on the face from a measurement of the point on each of the images. The palpebral fissure lengths, inner canthal-, and interpupillary distances of 44 subjects were measured in this manner independently by two investigators and compared with measurements obtained by clinical specialists in the conventional manner. There was found to be no statistically significant difference between palpebral fissure lengths determined using the two techniques (paired Student's t-test p-values are 0.29 and 0.18, respectively). It has also been demonstrated that facial measurements can be performed with greater consistency from a pair of stereo photographs than direct measurements from live subjects.

Anthropometry↗
PubMed1999

A new photogrammetric method to measure fetal breathing movements.

OBJECTIVE: In most recent studies, fetal respiratory movements have been measured with real-time and Doppler echography. We describe an alternative approach using photogrammetry that provides more objective measurements. METHODS: Respiratory movements were studied in 28 women with uncomplicated pregnancies of 30-38 weeks' gestation. Fetal echographic images were recorded on videotape and digitized to obtain coordinates of the reference point (midpoint on the anterior abdominal wall of the fetus between the xiphoid process and the insertion of the umbilical vessels) and generate graphic representations of fetal movements in the anterior abdomen. RESULTS: The mean duration of a complete respiratory cycle was 1.194 s, the mean distance representing the extent of movement was 2.92 mm, the mean inspiratory velocity was 5.52 mm/s and the mean expiratory velocity was 5.06 mm/s. CONCLUSIONS: Photogrammetric analysis of images obtained with real-time echography provided accurate measurements of fetal breathing movements.

Abdominal Muscles↗