Percutaneous MR-guided interventions using an optical Moiré Phase tracking system: Initial results.

The aim of this study was the development and evaluation of a real-time guidance support using optical Moiré Phase Tracking (MPT) for magnetic resonance (MR) guided percutaneous interventions. A gradient echo sequence, capable of real-time position updates by the MPT system, was modified to enable needle guidance based on four rigidly attached MPT markers at the back of a needle. Two perpendicular imaging planes were automatically aligned along the calibrated needle and centered at its tip. For user guidance, additional information about the needle trajectory and the tip to target distance were added as image overlay. Both, images and guiding information were displayed on the in-room monitor to facilitate MR guided interventions. The guidance support was evaluated by four experienced interventional radiologists and four novices targeting rubber O-rings embedded in a custom-made phantom on a 3T wide-bore MRI system (80 punctures). The skin to target time, user error, system error and total error were analyzed. The mean skin to target time was 146s±68s with no statistically significant difference between experts and novices. A low mean user error (0.91mm±0.43mm), system error (0.53mm±0.27mm) and total error (0.99mm±0.47mm) was reached in all directions. No statistically significant difference in user error, system error and total error could be found between experts and novices. The presented tracking and image guidance system combined with the user interface offers continuous and interactive control of the imaging plane while puncturing in the magnet enabling accurate real-time feedback for both, experienced and non-experienced users.

Non-invasive methods of computer vision in the posture evaluation of adolescent idiopathic scoliosis.

PURPOSE: Reviewing techniques for non-invasive postural evaluation of adolescent idiopathic scoliosis (AIS) based on information extraction from images based on computer methods. METHODS: The Scopus, Web of Science, MEDLINE, ScieLo and PubMed databases were used, for the period 2011-2015. RESULTS: 131 articles were found based on keyword of which 15 articles met the established eligibility criteria. Of these, 4 were based on photogrammetry, and 11 based on laser, structured light, ultrasound, and Moiré projection. In these studies, the methodological quality varied from low to high. CONCLUSIONS: The findings indicated diversity in methodologies; 14/15 articles reviewed were limited to the evaluation of the topography of the posterior back. A study, using two-dimensional photogrammetry, presented a whole body postural evaluation. As the asymmetry in AIS can be extended to the whole body, more attention should be given to develop full body assessment techniques to provide important additional data to aid in treatment decisions.

[The appearance test of a molar tooth with phase shift shadow moiré].

Modern photo-mechanics testing techniques are widely used in industrial circles and academic circles. In order to solve the problem of biomedical engineering, shadow moiré method is used in oral and dental area in our study. A molar tooth was tested by phase shift shadow moiré method. Through testing molar tooth, the results show that shadow moiré method could be used for measuring the appearance of the oral area and concave and convex parts of molar tooth could also be distinguished and shown by interference patterns. The characteristics of shadow moirh are that it does't need exerting load on the specimen and could realize non-contact measurement.

Measurements of 3D relative locations of particles by Fourier Interferometry Imaging (FII).

In a large number of physical systems formed of discrete particles, a key parameter is the relative distance between the objects, as for example in studies of spray evaporation or droplets micro-explosion. This paper is devoted to the presentation of an approach where the relative 3D location of particles in the control volume is accurately extracted from the interference patterns recorded at two different angles. No reference beam is used and only ten (2 + 8) 2D-FFT have to be computed.

New method of Scoliosis Deformity Assessment: ISIS2 System.

Scoliosis deformity has been assessed using radiographic angle measurements. Surface topography systems are an alternative and complementary methodology. Working systems include the original ISIS1 system, Quantec and COMOT techniques. Over the last five years the new ISIS2 (Integrated Shape Imaging System) has been developed from basic principles to improve the speed, accuracy, reliability and ease of use of ISIS1. The aim of this study was to confirm that ISIS2 3D back shape measurements are valid for assessment and follow up of patients with scoliosis. Three-dimensional back measurements were performed in Oxford. ISIS2 includes a camera/projector stand, patient stand with a reference plane, and Mac computer. Pixel size is approximately 0.5 mm with fringe frequency of approximately 0.16 fringes/mm ( approximately 6.5 mm/fringe). Clinical reports in pdf format are of coloured images with numerical values. Reports include a height map, contour plot, transverse section plots, coronal plot, sagittal sections and bilateral asymmetry maps. A total of 520 ISIS2 scans on 242 patients were performed from February 2006 to December 2007. There were 58 male patients (median age 16 years, SD 3.71, min 7, max 25) and 184 female patients (median age 14.5 years, SD 3.23, min 5, max 45). Average number of scans per patient was 2.01 with the range of 1-10 scans. Right sided thoracic curves were the most frequent pattern. The median values and 95% CI are reported of back length; pelvic rotation; flexion/extension; imbalance; lateral asymmetry; skin angle; kyphosis angle; lordosis angle; volumetric asymmetry. ISIS2 scoliosis measurements are non-invasive, low-cost, three-dimensional topographic back measurements which can be confidently used in scoliosis assessment and monitoring of curve progression.

Measurement of microstrains across loaded resin-dentin interfaces using microscopic moiré interferometry.

UNLABELLED: Little is known about the mechanical behavior of resin-dentin interfaces during loading. The presence of relatively compliant hybrid and adhesive layers between stiffer dentin and resin composite should deform more during compressive loading. OBJECTIVE: The objective of this study was to measure changes in microstrain across bonded dentin interfaces in real time using a recently developed microscope moiré interferometer. METHOD: This system used a miniature moiré interferometer, using two CCD cameras for simultaneous recording of longitudinal and transverse deformation fields, a piezotransducer for fringe shifting and use of a microscope objective with magnification up to 600 x. Small beams (1 mm x 2 mm x 6 mm) of moist resin-bonded dentin covered with cross-lined diffraction grating replica were placed in a miniature compression tester to allow controlled loading from 2 to 37 N while imaging the interference fringe patterns. RESULTS: Resin-dentin interfaces created by bonding dentin with Single Bond/Z100, under compressive loading, exhibited comparatively large strains across the adhesive-hybrid interface. When the wrapped phase maps were unwrapped to permit conversion of fringe order to displacements, the 2-D profiles of strain fields revealed non-uniform strains across the adhesive interface. In the adhesive/hybrid layer zone, the negative strain was larger (i.e. -6000 mu epsilon) than that seen in the adjacent resin composite or underlying mineralized dentin. The changes were elastic because they disappeared when the load was removed. SIGNIFICANCE: Microscopic moiré interferometry can be very useful in revealing real-time strain across bonded interfaces under load.

Long-wave cycles in the position of erupting human premolars.

OBJECTIVE: Unusual long-wave cycles in the position of an erupting human premolar were first noted by Trentini et al. [Trentini CJ, Brown WH, Paterson RL, Proffit WR. The application of Moire magnification to high precision studies of human premolar eruption. Arch Oral Biol 1995;40:623-9]. This report characterises them in detail and evaluates their significance relative to human tooth eruption. DESIGN: The magnitude and frequency of Trentini cycles were examined in high-resolution recordings of premolar eruption in patients without and with periapical infiltration of a vasoconstrictor or vasodilator, and the possibility of artifact due to the natural frequency of vibration of a tooth-PDL system or to building vibration was evaluated. RESULTS: The cycles are characterised by a magnitude of 1.3 +/- 0.5 microm and a frequency of 1.8 +/- 0.5 cycles per minute, with greater variation between than among subjects. They cannot be explained as a natural frequency phenomenon, and vibration from microseism is highly unlikely. The cycles disappear when blood flow to the periapical area of the tooth is interrupted and reappear when blood flow resumes. CONCLUSIONS: The cycles appear to reflect a physiologic rhythm, probably related to blood flow in the periodontal ligament. Because they are similar whether or not a tooth is erupting at a particular time, however, it appears that they are not a direct reflection of a blood flow-related eruption mechanism.

Mapping of tooth deformation caused by moisture change using moiré interferometry.

UNLABELLED: Bonding of composite restorative materials to teeth usually involves surface etching and drying of both dentin and enamel. These two hard tissues have very different water contents. OBJECTIVES: The purpose of this study was to evaluate the effects of changes in humidity on the dimensional changes in dentin disks constrained by enamel and in unconstrained dentin. METHODS: Changes in humidity were used to induce changes in the moisture level of the hard tissues, which created a mechanical load across the dentin-enamel junction (DEJ). High-sensitivity moiré interferometry was used to measure the magnitudes of the strains. Diffraction gratings (with a sensitivity of 2400 lines/mm) were transferred to moist polished sections of human teeth, which were subsequently dehydrated and then hydrated again. The fringe patterns from moiré interferometry recorded the change in deformation between the moisture states. RESULTS: The results indicated that there were wide variations in strain between the two specimen geometries. The strains were fairly constant through the bulk of the dentin in both specimen types. However, the strain gradients were very high across the dentin-enamel interface into the dentin in the unconstrained geometry, and nearly zero in the constrained geometry. SIGNIFICANCE: Moiré interferometry is a powerful tool to study the deformation of materials that are not isotropic and are not linearly elastic. It provides full-field, high-resolution deformation fields in tooth specimens. Deformations observed in this study indicate that the DEJ zone is a unique material interface that needs to be better understood in terms of normal tooth function, and that its material properties be taken into account when natural hard tissues are restored.

An investigation of CO2 laser scleral buckling using moiré interferometry.

BACKGROUND AND OBJECTIVE: To demonstrate suitability of moiré interferometry to assess and quantify laser-induced shrinkage of scleral collagen for buckling procedures. MATERIALS AND METHODS: Scleral buckling of human cadaver eyes was investigated using a Coherent Ultrapulse CO2 laser. Projection moiré interferometry was employed to determine the out-of plane displacement produced by laser exposure, and in-situ optical microscopy of reference markers on the eye was used to measure in-plane shrinkage. RESULTS: Measurements based on moiré interferometry allow a three dimensional view of shape changes in the eye surface as laser treatment proceeds. Out-of-plane displacement reaches up to 1.5 mm with a single laser spot exposure. In-plane shrinkage reached a maximum of around 30%, which is similar to that reported by Sasoh et al (Ophthalmic Surg Lasers. 1998;29:410) for a Tm:YAG laser. CONCLUSION: The moiré technique is found to be suitable for quantifying the effects of CO2 laser scleral shrinkage and buckling. This can be further developed to provide a standardized method for experimental investigations of other laser sources for scleral shrinkage.

Use of functional tests to increase the efficiency of scoliosis screening diagnosis by COMOT method.

COMOT technique was developed at Novosibirsk Research Institute of Traumatology and Orthopaedics as a pilot study in 1997 was used for screening for spine deformities in schoolchildren in Novosibirsk, Omsk and Moscow. Topographic screening was performed with patient standing in his natural free and easy posture. The criteria for scoliosis detection was an angle of lateral asymmetry (LA), calculated on the basis of topographic data, which was an analogue of Cobb angle. An additional criterion for structural spine deformation was an angle of scoliotic arch apex rotation (R). The analysis of responsiveness and specificity of topographic test (TT) at detection of structural arches of 10 and more degrees (according to Cobb) showed that they depend on the level of taken thresholds.

3D reconstruction and analysis of the whole trunk surface for non-invasive follow-up of scoliotic deformities.

The purpose of this study was to evaluate the 3D reconstruction accuracy of a new technology that allows the acquisition of the whole trunk and to develop a software to analyse the trunk surface asymmetry. A non-invasive active vision system provides a 3D textured reconstruction of the whole trunk. The analysis system provides the clinician with quantitative indices that characterize the whole external trunk asymmetry.

Construction of a high-resolution moiré interferometer for investigating microstructural displacement fields in materials.

A high-magnification moiré interferometer has been constructed with a spatial resolution of the order of 1 microm to measure the local in-plane displacement field associated with a material's microstructure. Laser illumination passes through phase-stepping optics and is delivered to the microscope head by polarization-preserving single-mode optical fibres. The head itself is a compact unit consisting of collimating optics, an objective lens and a charge coupled device (CCD) camera. Thin-phase gratings are cast onto the sample surface with a compliant epoxy resin and coated with ca. 5 nm of gold to enhance the fringe contrast and reduce speckle noise. By switching between the laser illumination and white-light illumination, the underlying microstructure is viewed in exact registration with the measured displacement fields. The application of the instrument is illustrated here by visualization of displacement fields in polymer-bonded explosives (PBXs) during deformation to failure. PBXs are highly filled polymers consisting of up to 95% by weight crystalline explosive bound in a variety of polymeric binders. The mechanical properties of PBXs are highly dependent on the microstructure, and moiré interferometry is an ideal tool for investigating the relationship between the 1-100 microm sized crystals and the displacement fields. Methods such as this are required if computer models of inhomogeneous materials are to be accurately validated.

Quantitative measurement of volume changes induced by oral plastic surgery: validation of an optical method using different geometrically-formed specimens.

The purpose of this research was to study the validity and variability of a projection Moiré system, measuring volume differences of geometrically different formed specimens mimicking localized alveolar ridge defects. Nine pairs of specimens were fabricated, each of which simulated a preoperative ridge defect and a corresponding surgically-corrected postoperative ridge defect. All specimen pairs had a mathematically defined form which allowed the accurate assessment of their volume differences by a mechanical 3-D coordinate measuring machine or by a software-controlled milling machine. Measurements achieved with these methods were used as the references for comparison. Six specimen pairs, A1 to A6, possessed a simple rectangular geometrical form which facilitated their fabrication. Three specimen pairs, B1 to B3, were milled and consisted of geometrically more complex 3-D sculptured surfaces, which came closest to a true imitation of a localized ridge defect. An optical measurement system in the form of the projection Moiré was utilized, applying a 4-phase shift technique, and results obtained with this device were regarded as test volumes. The absolute variability of the test volume measurements differed between 0.397 mm3 to 15.872 mm3, corresponding to a relative variability of 0.83% to 2.83%. The mean of the relative variability was within 1.68% for the "A" specimens and 2.15% for the "B" specimens. However, the difference was not significant, probably due to the limited number of "B" specimens. The systematic error of the Moiré measurements in relation to the reference methods was surprisingly low, ranging from -0.12 mm3 to 7.67 mm3. The relative systematic error, expressed as a percentage of reference volume, ranged between 0.06% and -2.23%. The mean of the relative error for the more complex "B" specimens was 1.37%, which was less accurate in comparison to the more simply formed "A" specimens with a relative systematic error of 0.35%. Therefore, in this in vitro model it was possible to measure volume differences of geometrically different formed specimens, mimicking localized alveolar ridge defects, with a validity within 2.2% and with a variability of less than 2.8%.

The application of Moire magnification to high-resolution studies of human premolar eruption.

The optical phenomenon of Moire magnification can be used to provide real-time measurements of the position of an erupting human premolar, with a resolution of 0.1 micron or better. A new instrument for this purpose, which allows repeated measurements in the same individual, is described. Cyclic changes in the position of the erupting tooth in concert with the heartbeat, with a magnitude of 0.05-0.35 micron, can be discerned. An unusual cyclic rhythm, with a period of 20-50 s, was observed.

Optic- and computer-aided surgery.

Optic- and computer-aided surgery is a new, original tool for the diagnosis of dismorphies, both in its conception (digitalization of a Moiré pattern on the body) and in its applications (predominantly surgical, for legal medicine and didactic purposes). By means of this three-dimensional (3D) method of measurement by digitalized Moiré, the forms of the body in general and those of the face in particular can be studied and quantified with a high degree of accuracy. This precision in the geometrical analysis of its forms is achieved by combining the latest developments in optics and computer technology. This article presents the current state of the authors' research in the 3D synthesis and manipulation of the human image.

An experimental study on biomechanical properties of hepatic tissue using a new measuring method.

Hepatic tissue is an important internal organ for life. In this paper, we combined the moire method (an optical method) and indentation technique to investigate biomechanical response of hepatic tissue. To examine this measuring technique, we first measured the biomechanical properties of the block of pig's hepatic tissue using this method. The experimental result indicated that the pig's hepatic tissue was obviously a viscoelastic material. We closely analyzed the change of curves for force relaxation, creep, and nonlinear deformation of the block of pig's liver. Meanwhile, we also compared the changes in the biomechanical parameters of normal and cirrhosis hepatic tissue of humans.

Three-dimensional analysis of facial morphology using moiré stripes. Part I. Method.

A system is presented for analysing facial morphology using moiré stripes. Faces are photographed with a moiré camera, the moiré stripes are entered into a computer, and the computer automatically analyses the dimensions of the face. Subtle differences between the right and left sides of the face appear as asymmetries in the moiré pattern and are easily identified. The method is useful for analysing maxillofacial deformities, for treatment planning, and assessment of postoperative results.

Variability of palatal dimensions in South Australian twins.

Estimates of genetic contributions to variability in three palatal dimensions were obtained from a sample of 70 pairs of South Australian twins aged between 11 and 26 years. Palatal width and length were measured directly from dental models, while palatal height was assessed indirectly from moiré contourographs. For each of the three palatal variables there was evidence of significant genetic variance, with heritability estimates for palatal width and height generally exceeding those for palatal length. Furthermore, palatal height measurements displayed greatest relative variability and strongest correlation between monozygous twins (r = 0.95), suggesting that this dimension could be useful as an additional comparative feature in forensic odontological investigations.

[Prediction system of facial change].

UNLABELLED: Three-dimensional simulation of facial change in a patient with severe facial deformity is very effective in not only determining a treatment plan but also in obtaining informed consent. The purpose of this presentation was to introduce the outline of our prediction system of facial change and its preliminary clinical application. (Outline of this system) This system is composed of the following three parts: Input: Three-dimensional digitized data from modified Moire Topography and coloring data of the face taken by the three-dimensional photographing appliance. ANALYSIS: Reconstruction of colored simulation model and transformation by host computer with 32 bit CPU. Output: Display of full-colored simulation model by three-dimensional graphics (Results of clinical application) 1. Three-dimensional reconstructed graphics were well accepted for clinical use, especially for the prediction in orthognathic surgery. 2. Compared with other systems, the following advantages were found: a) Simplified digitizing system using the CCD camera b) Total access time, from initial data input to display of computed picture, was about 20 minutes c) Accurate reproducibility of facial form and color vision.

Reliability of the moiré method in study of tooth and palatal morphology.

The purpose of the present study was to determine reproducibility of the photographic technique, intra- and inter-examiner reliability of the moiré method for investigating tooth and palatal morphology as well as the agreement between the moiré method and the palatometer in measuring palatal height. Intraclass correlation coefficients (ICC) of 0.88 to 0.95 for three separate photographs for each of the same 40 casts taken by three examiners and measured by a single examiner exhibited high reproducibility of the photographic technique. For studying tooth morphology, the moiré lines were counted from the cusp tips to the mesiobuccal and distolingual fossae. ICC of 0.92 to 0.99 with 95% confidence limits for triple measurements and Pearson correlation coefficients of 0.92 to 1.00 for double measurements showed high intra- and inter-examiner consistency, respectively. For palatal height at the level of the first maxillary molars ICC with 95% confidence limits for triple measurements was 0.98 and correlation coefficient between two examiners 0.98, respectively. Correlation coefficients between the moiré method and the palatometer were also high, with a value of 0.98. In summary, with careful calibration before use, the moiré method proved to be useful and reliable in studying tooth and palatal morphology.