An automatic markerless registration method for neurosurgical robotics based on an optical camera.

The purpose of this study was to investigate the feasibility of a surface-based registration method based on a low-cost, hand-held Sense three-dimensional (3D) scanner in image-guided neurosurgery system. The scanner was calibrated prior and fixed on a tripod before registration. During registration, a part of the head surface was scanned at first and the spatial position of the adapter was recorded. Then the scanner was taken off from the tripod and the entire head surface was scanned by moving the scanner around the patient's head. All the scan points were aligned to the recorded spatial position to form a unique point cloud of the head by the automatic mosaic function of the scanner. The coordinates of the scan points were transformed from the device space to the adapter space by a calibration matrix, and then to the patient space. A 2-step patient-to-image registration method was then performed to register the patient space to the image space. The experimental results showed that the mean target registration error of 15 targets on the surface of the phantom was 1.61±0.09 mm. In a clinical experiment, the mean target registration error of 7 targets on the patient's head surface was 2.50±0.31 mm, which was sufficient to meet clinical requirements. It is feasible to use the Sense 3D scanner for patient-to-image registration, and the low-cost Sense 3D scanner can take the place of the current used scanner in the image-guided neurosurgery system.

It is required to use a stereotactic frame on a patient's crainial surface to access an intracerebral hematoma in conventional ICH (Intracerebral Hemorrhage) removal surgery. Since ICH using a stereotactic frame is an invasive procedure and also takes a long time, we attempt to develop a robotic ICH removal procedure with a markerless registration system using an optical 3-D scanner. Preoperative planning is performed using a patient's CT (Computed Tomography) images, which include the patient's 3-D geometrical information on the hematoma and internal structures of brain. To register the preplanned data and the intraoperative patient's data, the patient's facial surface is scanned by an optical 3-D scanner on the bed in the operating room. The intraoperatively scanned facial surface is registered to the pose of the patient's preoperative facial surface. The conventional ICP (Iterative Closest Point) algorithm can be used for the registration. In this paper, we propose a weighted ICP in order to improve the accuracy of the registration results. We investigated facial regions that can be used as anatomical landmarks. The facial regions for the landmarks in the preoperative 3-D model are weighted for more accurate registration. We increase weights at the relatively undeformed facial regions, and decrease weights at the other regions. As a result, more accurate and robust registration can be achieved from the preoperative data even with local facial shape changes.

Low registration errors are an important prerequisite for reliable navigation, independent of its use in cranial or spinal surgery. Regardless of whether navigation is used for trajectory alignment in biopsy or implant procedures, or for sophisticated augmented reality applications, all depend on a correct registration of patient space and image space. In contrast to fiducial, landmark, or surface matching-based registration, the application of intraoperative imaging allows user-independent automatic patient registration, which is less error prone. The authors' aim in this paper was to give an overview of their experience using intraoperative CT (iCT) scanning for automatic registration with a focus on registration accuracy and radiation exposure. A total of 645 patients underwent iCT scanning with a 32-slice movable CT scanner in combination with navigation for trajectory alignment in biopsy and implantation procedures (n = 222) and for augmented reality (n = 437) in cranial and spine procedures (347 craniotomies and 42 transsphenoidal, 56 frameless stereotactic, 59 frame-based stereotactic, and 141 spinal procedures). The target registration error was measured using skin fiducials that were not part of the registration procedure. The effective dose was calculated by multiplying the dose length product with conversion factors. Among all 1281 iCT scans obtained, 1172 were used for automatic patient registration (645 initial registration scans and 527 repeat iCT scans). The overall mean target registration error was 0.86 ± 0.38 mm (± SD) (craniotomy, 0.88 ± 0.39 mm; transsphenoidal, 0.92 ± 0.39 mm; frameless, 0.74 ± 0.39 mm; frame-based, 0.84 ± 0.34 mm; and spinal, 0.80 ± 0.28 mm). Compared with standard diagnostic scans, a distinct reduction of the effective dose could be achieved using low-dose protocols for the initial registration scan with mean effective doses of 0.06 ± 0.04 mSv for cranial, 0.50 ± 0.09 mSv for cervical, 4.12 ± 2.13 mSv for thoracic, and 3.37 ± 0.93 mSv for lumbar scans without impeding registration accuracy. Reliable automatic patient registration can be achieved using iCT scanning. Low-dose protocols ensured a low radiation exposure for the patient. Low-dose scanning had no negative effect on navigation accuracy.

Intraoperative speech mapping has evolved into the "gold standard" for neurosurgical removal of lesions near the language cortex. The integration of neuronavigation into a multimodal protocol can improve the reliability of this type of operation, but most systems require rigid fixation of the patient's head throughout the operation. This article describes and evaluates a new noninvasively attached sensor-based reference tool, which can replace rigid pin fixation of the patient's head during awake craniotomies. The attachment technique and the resulting application accuracy were investigated under clinical conditions in 13 patients undergoing awake craniotomy with intraoperative mapping of cortical language sites. Spatial information was used for updating the image guidance by continuously adjusting the image planes relative to the position of the patient's head. The mean registration error achieved with this technique was 1.53 +/- 0.51 mm (fiducial registration error +/- standard deviation). The system's median application accuracy between dura opening and closure ranged from 0.83 to 1.85 mm (position error). The use of a reference sensor can replace uncomfortable pin fixation of the patient's head during navigation-supported awake craniotomies. Application accuracy is not affected by repositioning of the patient or by unavoidable head movements. Thus, this technique enables full exploitation of the benefits of navigation in a multimodal operative protocol without the need to rigidly fix the patient's head.

The growth and development of a person's body can be affected by various factors such as hereditary factors, the environment and the type of food consumed. One method that can be used to find out the condition of a person's body growth and development is to compare weight and height. This analysis is known as Body Mass Index (BMI). To carry out this analysis, weight and height measurements must first be taken. With the tools developed in this study, the analysis process can be carried out easily. This developed tool is able to measure height and weight at the same time. Height measurement is carried out by placing the weight sensor (Load Cell) under the user's footing like a tire scale in general. As for height measurement, on the top of the patient's head, a laser-based distance sensor VL53L1X placed. In contrast to height measurement which uses a voice-based distance sensor with direct measurements on the surface of the patient's head whose measurement results are less accurate. This is due to the uneven surface of the head, different hair shapes, and diffused sound waves. With the Scale Bar method/plate that can move up/down automatically as the sensor measurement plane. Thus, the measurement results are better because the reflection plane is in the form of a flat plate so that the light reflection results from the laser sensor become more focused. From the results of measurements, weight and height in several patients, the results of measurements were obtained with an average difference of 0.3 cm for height and 0.09 kg for body weight measurement.

The determination of particle collision kinetics is useful to decouple the effects of process parameters on individual events in flocculation. This paper discusses the effects of flocculation conditions on the collision efficiency of ATCC strain CRL 1606 hybridomas flocculated with poly-L-histidine. Experimental determinations of the collision efficiency of cells in Couette flow are presented over a range of experimental conditions. The collision efficiency correlates with the cell zeta potential to the -2.4 power at high surface coverage, consistent with literature results in latex systems. At low coverage, accounting for the distribution of polymer on the cells corrects for deviation from the high-coverage behavior. Collision is dependent on the hydrodynamic environment as well. At high surface coverage, collision efficiency is weakly dependent on hydrodynamic conditions and follows a dependency on the shear rate and viscosity to the -0.32 power. This is consistent with ionic coagulation theory. At low surface coverage, the collision efficiency is strongly dependent on the viscous fluid forces. The results versus both dose and shear rate over the entire range of surface coverages are consistent with weak intercell bonding. Collision kinetics in the presence of high molecular weight dextrans show steric hindrance to cell collision.

Automatic Registration between Real-Time Ultrasonography and Pre-Procedural Magnetic Resonance Images: A Prospective Comparison between Two Registration Methods by Liver Surface and Vessel and by Liver Surface Only

The relationship between alkyl phase structure and chromatographic performance is investigated for a series of docosyl (C22)-modified silica surfaces. The results of solid-state nuclear magnetic resonance (NMR) spectroscopy and fluorescence spectroscopy are evaluated and correlated with liquid chromatographic retention for relevant shape-selective separations. A set of four different stationary phases was prepared by solution and surface polymerization approaches, yielding materials with surface coverages ranging from 3.6 to 7.0 μmol/m2. 13C cross polarization magic angle spinning (CP/MAS) NMR spectra indicate that a predominance of trans conformations exists for high-coverage C22 phases (>4.0 μmol/m2). Two-dimensional solid-state NMR spectroscopy (wide line separation, WISE) was utilized to evaluate the mobility of the trans and gauche alkyl chain conformations. Temperature-dependent 13C CP/MAS NMR measurements of the bonded phases exhibit large differences in the dynamic behavior of the immobilized C22 chains. Unusually high chain rigidity was found for the self-assembled monolayer C22 phase (7.0 μmol/m2). Fluorescence lifetime measurements of 1,6-diphenylhexatriene (DPH) exhibit two different lifetimes of τF ≈ 1 and 7 ns, which are ascribed to probe molecule populations in the mobile and bonded phases, respectively. Quantitative evaluation of the fluorescence decay curves shows that the partitioning of DPH into the alkyl phase is favored at higher surface coverages, reaching a maximum at a ligand density of 4.9 μmol/m2. Time-resolved fluorescence anisotropy measurements also revealed that probe mobility was minimized at this surface coverage. With increasing temperature, the mobility of DPH was found to increase and the fraction of sorbed molecules to decrease. A shape selectivity test mixture containing five polycyclic aromatic hydrocarbons including DPH was employed for temperature-dependent chromatographic studies. In accord with the spectroscopic results, shape selectivity is enhanced at low temperatures and at high surface coverages. The combination of these spectroscopic and chromatographic tools provides a wealth of information on the surface morphology of systematically prepared C22 sorbents and greater insight on the molecular recognition process in liquid chromatography.

Molecular dynamics simulations of monolayers of metal-chelating ligands grafted onto a graphite surface in water are carried out to calculate structural (density profiles, radius of gyration, and asphericity coefficients), dynamical (diffusion coefficients), and energetical properties as a function of the surface coverage. The purpose is to provide a better understanding of the dependence of various properties of these monolayers on the surface coverage. A critical value of the surface coverage from which all structural properties derive a limiting value has been established. It also appears that the chains rather adopt an elongated conformation along the direction normal to the surface from this critical surface coverage. The hydrogen-bonding structure and dynamics of water molecules are reported. An ordered structure of water in the region close to the terminal groups of the grafted molecules is shown at a relatively high surface coverage. This ordering is similar to that observed in the case of water in interaction with a solid surface.

The adsorption of a series of (ethylene oxide−tetrahydrofuran−ethylene oxide), EOn/2THFmEOn/2, triblock copolymers has been studied at the water/hydrophobic silica interface by time-resolved ellipsometry. The copolymers form monolayers with the middle tetrahydrofuran block anchoring at the surface and the ethylene oxide groups either anchoring at the surface or protruding into the aqueous phase. The degree of anchoring of the EO chains depends critically on the surface coverage. The copolymer isotherms are generally rather well described by the conventional Langmuir expression, and the plateau surface area per polymer molecule increases linearly with the molecular weight. However, the plateau thickness exhibits a more complex behavior. At low coverages, the adsorbed layer thickness is small, and both THF and EO chains form trains at the surface. As the surface coverage increases, however, the EO chains are increasingly forced away from the surface, and the mean thickness of the adsorbed layer exhibits a relatively strong linear dependence on the surface excess. At higher coverages, closer to the adsorption plateau, a weaker dependence is observed. The thickness increase is in this latter region due to the increasing steric repulsion between protruding EO chains. Outside the adsorbed layer, we also found support for the existence of a depletion layer. We show further that there are three regimes in the kinetics of adsorption. In the first (low surface coverage), the process is diffusion controlled and the rate is proportional to the concentration difference between the bulk solution and the subsurface located just outside the adsorbed layer. In the second regime (intermediate coverages and adsorption times), the kinetics are governed by the rate of displacement of anchored EO chains by THF chains of adsorbing copolymers. In the third regime (high surface coverages), the adsorption slows down markedly due to the energy barrier caused by presence of the relatively dense brush of adsorbed EO chains. In this regime, the surface excess varies proportionally with log t, which was also observed to be the case during the desorption process.

Quartz particles of various discrete particle size ranges have been methylated to varying known mounts using trimethylchlorosilane and their flotation behaviour has been assessed in a modification of the Hallimond tube. For each particle size there is a definite degree of. surface coverage below which the particles do not float. A 'flotation domain' is identified which shorvs that both coarse (-100pm) and fine (-10pm) particles require a greater degree of surface coverage to initiate flotation than do intermediate (-40pm) particles. Water contact angles have been measured on quartz plates and powders which have been methylated (under the same conditions) with trimethylchlorosilane. Both advancing and receding water contact angles measured on quartz plates as a function of degree of surface methylationare in good agreement with the angles predicted by the Cassie equation. Advancing water contact angles measured on quartz particles as a function of degree of surface methylation are also in good agreement with angles predicted by the Cassie equation up to surface coverages of'about 70%. The angles measured at higher surface coverages are less than those anticipated by the Cassie equation. The flotation behaviour of the particles has been compared with that predicted by existing flotation theories. It has been shown that coarse particle behaviour is predicted by the kinetic theory of flotation proposed by Schulze. Fine particle behaviour, however, only qualitatively agrees with Scheludko's theory of fine particle behaviour. Calculated induction times, in conjunction with observed flotation behaviour, indicate that the bubble-particle attachment process is most efficient for particles of about 38pm in diameter ander the set experimental conditions used in this study. Flotation rate trials were performed for three particle size ranges and rate constants were evaluated for the various degrees of surface coverage. It was found that the dependence of rate constant on particle size is essentially linear.

Navigation-Supported Stereotaxy by Applying Intraoperative Computed Tomography

BackgroundStereotactic navigation could improve the quality of surgery for rectal cancer. Critical challenges related to soft tissue stereotactic pelvic navigation include the potential difference in patient anatomy between intraoperative lithotomy and preoperative supine position for imaging. The objective of this study was to determine the difference in patient anatomy, sacral tilt, and skin fiducial position between these different patient positions and to investigate the feasibility and optimal set-up for stereotactic pelvic navigation.MethodsFour consecutive human anatomical specimens were submitted to repeated CT-scans in a supine and several degrees of lithotomy position. Patient anatomy, sacral tilt, and skin fiducial position were compared by means of an image computing platform. In two specimens, a 10-degree wedge was introduced to reduce the natural tilt of the sacrum during the shift from supine to lithotomy position. A simulation of laparoscopic and transanal surgical procedures was performed to assess the accuracy of the stereotactic navigation.ResultsAn up-to-supracentimetric change in patient anatomy was noted between different patient positions. This observation was minimized through the application of a wedge. When switching from supine to another position, sacral retroversion occurred independent of the use of a wedge. There was considerable skin fiducial motion between different positions. Accurate stereotactic navigation was obtained with the least registration error (1.9 mm) when the position of the anatomical specimen was registered in a supine position with straight legs, without pneumoperitoneum, using a conventional CT-scan with an identical specimen positioning.ConclusionThe change in patient anatomy is small during the sacral tilt induced by positional changes when using a 10-degree wedge, allowing for an accurate stereotactic surgical navigation. This opens up new promising opportunities to increase the quality of surgery for rectal cancer cases where it is difficult or impossible to identify and dissect along the anatomical planes.

Hydrogen permeation through palladium membranes and inhibition by carbon monoxide, carbon dioxide, and steam

Molecular dynamics simulations of adsorption behavior of organic friction modifiers on hydrophilic silica surfaces under the effects of surface coverage and contact pressure