Manual Positioning Research Articles

Movement speed effects on limb position drift.

Previous research has shown that even when limb position drifts considerably during continuous blind performance, the topological and metrical properties of generated hand paths remain remarkably invariant. We tested two possible accounts of this intriguing effect. According to one hypothesis, position drift is due to degradation of limb-position information. This hypothesis predicted that drift of static hand positions at movement reversals should not depend on movement speed. According to the other hypothesis, position drift is due to degradation of movement information. This hypothesis predicted that drift of static hand positions at movement reversals should vary with movement speed. We tested these two hypotheses by varying the required movement speed when normal human adults performed back-and-forth manual positioning movements in the absence of visual feedback. Movement distance and direction were well preserved even though hand positions between movements drifted considerably. In accord with the movement error hypothesis, but not in accord with the position hypothesis, the rate at which hand positions drifted depended on movement speed. The data are consistent with the idea that hand position, which defines the origin of the trajectory control coordinate system, and movement trajectory are controlled by distinct neural mechanisms.

End posture selection in manual positioning: evidence for feedforward modeling based on a movement choice method.

Although it is well known that the postures adopted at the ends of movements depend on where one starts and how one moves, it is not yet clear whether those differing end postures are selected before movements begin. Two experiments were designed to test the hypothesis that end postures for positioning movements are chosen before movements commence. The experiments were further designed to check whether movements are internally simulated before overt movements occur and end-postures are still being selected. To address these questions we used a movement choice method. Participants were presented with two possible end postures and were asked to choose between them by moving to the one that seemed easier to adopt. End-posture choices were affected by starting positions and also by the movements that would have to be made, as affected by having obstacles in the way. The results suggest that participants relied on feedforward modeling of prospective movements as they selected end postures prior to overt movement production. The fact that the movement choice method could confirm this suggests that the method holds considerable promise as a tool for investigating motor planning.

Indications to the use of condylar repositioning devices in the surgical treatment of dental-skeletal class III

Purpose: The aim of this report was to compare the clinical and radiographic findings observed at the 12-month follow-up in 2 groups of 15 patients who underwent Le Fort I and bilateral sagittal split osteotomy for the correction of dental-skeletal Class III. In the first group, the condylar positioning devices were used, whereas in the second group, an alternative method was used for the intraoperative assessment of mandibular repositioning. Materials and Methods: All of the patients of our study in the immediate presurgical period were without temporomandibular joint disorders and with a normal anatomic relationship between condyle and fossae. The condyle position and morphology were examined at the 12-month follow-up through cephalometric measurements and the postsurgical findings in both groups were compared with those observed in the presurgical period. Results: In all of the 30 patients in our study, no relapse or postsurgical temporomandibular joint disturbance was observed at the 12-month follow-up. Variations in condyle position of more than 2 mm or 2° were not observed in the 15 patients treated with condylar positioning devices. Changes in condyle position between 2 and 4 mm and 2° and 4° were observed in 6 of the 15 patients treated without the devices. Conclusions: The use of condylar positioning devices can be avoided in patients with dental-skeletal Class III without presurgical temporomandibular dysfunction. The manual positioning of the mandibular condyle is easier, but it requires the utmost care and an experienced operator. © 2003 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 61:304-309, 2003

MRI-guided gas bubble enhanced ultrasound heating in in vivo rabbit thigh

In this study, we propose a focused ultrasound surgery protocol that induces and then uses gas bubbles at the focus to enhance the ultrasound absorption and ultimately create larger lesions in vivo. MRI and ultrasound visualization and monitoring methods for this heating method are also investigated. Larger lesions created with a carefully monitored single ultrasound exposure could greatly improve the speed of tumour coagulation with focused ultrasound. All experiments were performed under MRI (clinical, 1.5 T) guidance with one of two eight-sector, spherically curved piezoelectric transducers. The transducer, either a 1.1 or 1.7 MHz array, was driven by a multi-channel RF driving system. The transducer was mounted in an MRI-compatible manual positioning system and the rabbit was situated on top of the system. An ultrasound detector ring was fixed with the therapy transducer to monitor gas bubble activity during treatment. Focused ultrasound surgery exposures were delivered to the thighs of seven New Zealand white rabbits. The experimental, gas-bubble-enhanced heating exposures consisted of a high amplitude 300 acoustic watt, half second pulse followed by a 7 W, 14 W or 21 W continuous wave exposure for 19.5 s. The respective control sonications were 20 s exposures of 14 W, 21 W and 28 W. During the exposures, MR thermometry was obtained from the temperature dependency of the proton resonance frequency shift. MR T2-enhanced imaging was used to evaluate the resulting lesions. Specific metrics were used to evaluate the differences between the gas-bubble-enhanced exposures and their respective control sonications: temperatures with respect to time and space, lesion size and shape, and their agreement with thermal dose predictions. The bubble-enhanced exposures showed a faster temperature rise within the first 4 s and higher overall temperatures than the sonications without bubble formation. The spatial temperature maps and the thermal dose maps derived from the MRI thermometry closely correlated with the resulting lesion as examined by T2-weighted imaging. The lesions created with the gas-bubble-enhanced heating exposures were 2–3 times larger by volume, consistently more spherical in shape and closer to the transducer than the control exposures. The study demonstrates that gas bubbles can reliably be used to create significantly larger lesions in vivo. MRI thermometry techniques were successfully used to monitor the thermal effects mediated by the bubble-enhanced exposures.

A reply

Our expression of the neck position should have been more unambiguous. This ambiguity was due to a common practice of not distinguishing explicitly the position of the upper from lower cervical spine. We stated that ‘insertion of the conventional laryngeal mask is best achieved when the patient's neck is flexed and the head extended as described by Magill (‘sniffing’ position)’ [1]. This is the most commonly used expression of the head and neck position that Drs Brimacombe and Keller also adopt. A more accurate expression is extension of the occipitoatlantoaxial complex (i.e. extension of the head on the neck and of the upper cervical spine) and flexion of the lower cervical spine [2]. We also stated that ‘in fact, its insertion becomes more difficult or impossible when the patient's head and neck are in either the neutral or flexed position’ [1] and cited three articles [345]. In the first study [3], insertion of the laryngeal mask was more difficult when the occiput was placed directly on the trolley and the head and neck were stabilised (manual in-line position) than when the head and neck were placed in the Magill position. In retrospect, we should not have used the term ‘neutral position’, since it can be regarded as the position of the head and neck when the occiput is placed either directly on the trolley or on one pillow (or a pad). In the second study [4], it was suggested that flexion of both the occipitoatlantoaxial complex and lower cervical spine by cricoid pressure made insertion more difficult. In the third report [5], insertion of the mask was impossible when the occipitoatlantoaxial complex was flexed and the lower cervical spine extended. Drs Brimacombe and Keller state that we showed that neck flexion facilitated placement, but what we showed was that extension of the occipitoatlantoaxial complex (i.e. extension of the upper cervical spine) and flexion of the lower cervical spine facilitated placement [3]. Therefore, perhaps we should have stated that insertion may become more difficult when the occipitoatlantoaxial complex (or the head and upper cervical spine) is flexed. In our patient, both the occipitoatlantoaxial complex and the lower cervical spine were flexed due to burn contracture [1]. We expressed this as a ‘a fixed flexed neck’.

Tactical audio and acoustic rendering in biomedical applications

Complexity of biomedical data requires novel sophisticated analysis and presentation methods. Sonification is used as a new information display in augmented reality systems to overcome problems of existing human-computer interface (e.g., opaque or heavy head-mounted displays, slow computer graphics, etc.). A novel taxonomy of sonification methods and techniques is introduced. We present our experience with tactical audio and acoustic rendering in biomedical applications. Tactical audio as an audio feedback is used as support for precise manual positioning of a surgical instrument in the operating room. Acoustic rendering is applied as an additional information channel and/or warning signal in biomedical signal analysis and data presentation.

Automatic Target Location Strategy-A Novel Approach in Scanning Electrochemical Microscopy

In this article a recently constructed scanning electrochemical microscope with an original automatic target location facility is described and its operation is demonstrated on different targets. The measuring tip positioning device is based on stepper motor driven linear modules with 75 nm linear travel resolution. The home-built electronic unit and the Windows 95 compatible measuring and image-forming program furnish the microscope to operate in both amperometric and potentiometric modes. A novel, simplex algorithm based automatic target location program was developed to substitute the tedious and lengthy manual tip positioning. In this article different strategies are described and the most important results of this investigation are summarized.

SELF-ALIGNMENT TECHNIQUE OF SURFACE-MICROMACHINED OPTICAL SWITCHES TO BULK-MICROMACHINED V-GROOVES

We report a new self-alignment technique of surface-micromachined polysilicon structures to bulkmicromachined silicon V-grooves which are used to accommodate optical fibers. Most of the conventional surface micromachined optical structures have used thin guiding rails or marks on a silicon substrate to align optical fibers to microstructures, and thus they require careful manual positioning. We have newly developed a technique to hold fibers in V-grooves, which have been defined at the same time as optical microstructures, to eliminate fiber manipulation for alignment. The process is simple with only two additional masks to the existing surface micromachining process and can be generally applied to MEMS fabrication.

Registration of synthetic tomographic projection data sets using cross-correlation

Tomographic registration, a method that makes possible accurate patient registration directly from projection data, consists of three processing steps: (i) manual coarse positioning, (ii) tomographic projection set acquisition, and (iii) computer mediated refined positioning. In the coarse positioning stage, the degree of patient alignment is comparable with that achieved with the standard radiotherapy set-up. However, the accuracy requirements are somewhat more relaxed in that meticulous alignment of the patient using external laser indicators is not necessary. Instead, tomographic projection sets are compared with planning CTs in order to achieve improved patient set-up. The projection sets are cross-correlated to obtain the best-fit translation and rotation offsets. The algorithm has been tested on synthetic data with the incorporation of varying amounts of Gaussian pseudo-random noise. These tests demonstrate the algorithm's stability and also confirm that alignment can be achieved with an accuracy of less than one projection pixel.

Ease of placement of the laryngeal mask during manual in-line neck stabilization

We studied 20 patients, in a randomized, cross-over study, to determine if manual in-line stabilization of the head and neck altered the ease of insertion of the laryngeal mask and its correct positioning. After induction of anaesthesia and neuromuscular block, the laryngeal mask was inserted and adequacy of ventilation assessed while the patient's head and neck were placed in the Magill and manual in-line positions, in turn. Ease of insertion of the mask was assessed using a 10-cm visual analogue scale (VAS) and position using a fibreoptic bronchoscope. Time for insertion of the mask was measured. The laryngeal mask was inserted and adequate ventilation obtained at the first attempt in all 20 patients in the Magill position and in 19 of 20 patients in the manual in-line position. Insertion was always more difficult (P << 0.001; 95% CI for difference in VAS 20-55 mm) and time for insertion longer (P << 0.001; 95% CI for difference 4.9-11.9 s) in the manual in-line position compared with the Magill position. The incidence of a suboptimal position was significantly higher for the manual in-line position (seven patients) than for the Magill position (15 patients) (P < 0.005). We conclude that in paralysed patients, manual in-line stabilization of the head and neck made insertion of the laryngeal mask and its correct positioning more difficult.

177 The accuracy of patient positioning in irradiation of rectum cancer

Purpose Evaluation of correct positioning using an ionisation chamber on-line portal imaging system in routine clinical radiotherapy of rectum cancer. Methods and Materials In 13 patients with pelvic irradiation, portal images were obtained using a fast electronic megavoltage radiotherapy imaging system. A total of 208 portal images and 13 simulator films were used to determine the values of setup deviations in the X-Y-directions and the rotation of fields in a fixed coordinate system, and the accuracy of the manually positioned blocks. Results Mean standard deviations of the difference between simulation and treatment images were in mm: 7.33 and 7. 13 for X and Y, 3.55 for the rotation fault, and 4.55 for the position of blocks. Maximal variations of standard deviations were respectively 2.29–11.91; 2.39–7.83; 1.84–7.07; 1.17–10.09. Conclusion The errors of field positions summed up to a mean of up to 11.91 mm in one patient. Maximal errors counted in single fields up to 30 mm. The mean error of manual block positioning was not acceptable. Thus, mechanically fixed blocks are now used after obtaining the results of this study. A daily control should be considered for difficult patients.

A simple manual method of repositioning small bowel during pelvic irradiation

Small intestine is often unnecessarily irradiated during radiotherapy because it lies near tumor volumes and thus may be dose limiting. Repositioning of normal tissues can sometimes be accomplished by mechanical rather than invasive surgical techniques. At our institution, physical displacement of small bowel tissues was carried out on a population of patients with good result. Patients suffering from prostatic, cervical, and rectal carcinoma were treated using a custom built and padded block composed of rigid Styrofoam. The block, in most cases, successfully displaced significant amounts of healthy tissues from treatment fields. Maximum displacement of bowel was accomplished at the time of simulation using fluoroscopy and manual positioning of the device. The optimum displacement position and location of the Small Bowel Displacement Device (SBDD) were recorded by means of orthogonal radiographs. The device was affixed to a piece of mylar that had been previously scribed with an X and Y coordinate system, which could be used to permanently anchor the SBDD to its position of maximum displacement. Displacements of as much as 4.0 to 5.0 cm were noted on most patients. Patients generally tolerated the device well as long as they were able to lie prone. Patients with recent abdominal surgery were less likely to tolerate the SBDD, and omental slings or meshes generally precluded movement of the small bowel.

Nonsurgically Treated Carpal Tunnel Syndrome in the Manual Worker

This study evaluates the course of carpal tunnel syndrome in a group of manual laborers who declined surgery for personal or social reasons. Thirty-five patients and 67 extremities with carpal tunnel syndrome were evaluated in a group of manual laborers. The carpal tunnel syndrome was classified as mild, moderate, or severe on the basis of initial evaluation data. Sensory batteries, motor and sensory conduction velocities, and electrical studies were performed on a scheduled basis. Follow-up ranged between 14 and 58 months, with an average of 34.3 months. Three patients became worse and one improved during the study period. All others remained unchanged. Six patients returned to work, but only three returned to their original jobs. Although carpal tunnel syndrome does not appear to be a progressive condition once the triggering cause is removed, nonsurgical treatment does not seem to be the treatment of choice for patients who must continue in a manual labor position.

Operator Performance with Alternative Manual Control Modes in Teleoperation

Recent experiments conducted at the Jet Propulsion Laboratory (JPL) comparing alternative manual control modes using the JPL Advanced Teleoperator (ATOP) System are described in this paper. Of particular interest were control modes that provide force reflection to the operator. The task selected for the experiment is a portion of the Solar Maximum Satellite Repair (SMSR) procedure we developed to demonstrate the repair of the Solar Maximum Satellite with teleoperators. SMSR had been successfully performed by NASA astronauts in 1984 and it was selected as a task to demonstrate the ATOP system capability for space applications. The seven manual control modes evaluated in the experiment are combinations of manual position or resolved motion rate control with alternative control schemes for force reflection and remote manipulator compliance. Performance measures used were task completion times, average force and torque exerted during the execution of the task, and cumulative force and torque exerted. The results were statistically analyzed and they show that, in general, force reflection significantly improves operator performance and indicate that a specific force-reflecting scheme may yield the best performance among the control modes we tested. Also, our experiment showed that, for the selected task, the position control modes were preferable to the rate control modes and slave manipulator compliance reduced task interaction forces and torques.

Assessment of Bone Mineral Content in the Internal Bone Volume

A method for assessing values related to bone density and mass is described. Mean attenuation and pixel area are measured in pixels selected on the basis of CT units. The method is to a large extent computerized and not dependent on manual positioning or outlining of a region of interest. Because it is not dependent on a comparatively large volume of homogeneous bone it can be used to make assessments even in very heterogeneous bones including cortical bone. The method is adaptable for measurement in all parts of the skeleton and values related to both bone density (DRV) and bone mass (MRV) are derived. The measurements in the femoral condyles were shown to have a precision of approximately 0.25 to 0.30 Z-score units (standard deviation of the measurements expressed in Z-score units). The agreement between chemically analyzed calcium density (weight of calcium per volume) and DRV was little less than 0.50 Z-scores and 0.30 Z-scores for the chemically determined calcium mass and the MRV. The agreement with mechanical bone strength was 0.78 Z-scores for DRV and 0.64 for the MRV. Altering scan parameters or measuring approaches gave systematic differences in measurements. There were, however, good linear correlations between the measurements which show that these different measuring approaches essentially gave identical measurements.

A five-axis computer-controlled stage for the Transmission Electron Microscope

A new five axis computer controlled stage system for the transmission electron microscope has been developed. The current design uses the existing stage of a Philips 400T without internal modification. The motors are all synchronous and employ feedback control from shaft encoders rather than “steps”.The X and Y translation controls have an increment of 15 nm and are engaged by electronic clutches. The alpha tilt control can be incremented in 0.0625 degree units which allows 16 “steps” per degree. The beta tilt has an increment of 0.0017 degrees (approximately 500 counts per degree). The Z axis control has a 3 nm increment and can be controlled by a set of manual override switches. The position of the stage is monitored by shaft encoders in such a way that manual positioning does not effect motorized repositioning.All five axes are calibrated for speed to determine the log/linear range of movement (Figs. 1-4). From the graphs, three speeds are chosen.

A Foot-Fixator for Exact Imaging Reproducibility in Lower Extremity Radiography

For repeated radiographic examinations for evaluating fracture healing, dislocation of fractures, migration and loosening of prostheses, resorption conditions, etc, it is very important that identical and comparable projections should be available. Traditional manual by-eye positioning can be inadequate in many situations. A device designed with the aim of securing identical and reproducible projection conditions on different occasions was therefore constructed.

Individual characteristics of sitting behaviour

During the performance of a manual positioning task weight displacements on the sets of chairs have been recorded. They show a clear individual pattern with similar characteristics on subsequent ex...

RETRAN Analysis of the San Onofre Unit 2 Turbine Trip from 100% Power

The RETRAN analysis of San Onofre Nuclear Generating Station Unit 2 (SONGS 2) turbine trip from 100% power is a continuing effort of out inhouse RETRAN model development to benchmark the calculations against the plant test data. The previous benchmarked calculations - RETRAN analyses of SONGS 2 flow measurements and low-power natural circulation test - showed very good agreement with the plant test data. The latter RETRAN model was then expanded for the current study to include steam generator secondary side, main steam line pipings, control valves, and plant control systems. The benchmarked turbine trip model has been used to analyze the station-requested plant operational transients. These are assessment of strategies for performing turbine overspeed surveillance, determining a manual position of one steam bypass valve following a reactor trip from 100% power, and plant response to one main steam isolation valve closure at 90 and 50% power levels. In addition, the RETRAN calculations employing benchmarked models can be used to verify the simulator predictions and assess the existing plant operating procedures.

Computer-based determination of size and shape in living cells.

Measurement of cell volume in living epithelial cells has become an important technique in studies of membrane transport processes that function in cell volume regulation. Planimetry of video images of optical sections enables the measurement of the cross sectional area of each section. Cell volume is calculated from the measured area of each section and the known focus displacements. In the past the measurement of cross section area has been done by manual positioning of a cursor superimposed on the video image. Each experiment generates approximately 200 images in which two or more cells may be analysed. We have developed a computer-based method that uses one image as a template, and allows automated area determination of successive images by template matching and digital image processing. This new method is comparable to the older method in speed and accuracy, but requires much less effort from the experimenter.