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A new diagnostic method to measure the trajectory and orientation of a magnetized projectile traveling through opaque media in-situ has been developed. An array of magnetic field sensing coils placed around a projectile flight path produces raw voltage data that, upon analysis, yields the trajectory of the projectile. This paper discusses the theory of operation of the diagnostic, presents the analysis used to convert voltage signals to trajectory information, gives design details of the sensor array, and presents two representative experiments. In these experiments projectiles were launched from a 50-mm gun at a velocity of about 1 km/s. In both cases the projectiles perforated a 35 inch long, right circular cylinder filled with sand. Data from 24 sensing coils were recorded and analyzed to determine the trajectory and orientation of the projectiles from well before they impacted the opaque material until well after target exit. To test the validity of the method high-speed digital video cameras recorded the projectiles’ entry and exit for the same sand targets. Trajectory and orientations from the magnetic tracking technique compared well to camera observations.

A novel haptic position measurement system (HPMS) utilizing a hand-held magnetic sensor is developed to measure the position and shape of soft/compliant objects. The magnetic senor, serving as a touch probe, is guided by hand to contact with the object. The haptic feedback from the contact between the sensor and object provides the guidance to the user for measurement. The HPMS is validated by measuring the diameter of a soft silicone phantom and shown capable to achieve 0.2 mm accuracy level. This result demonstrated the feasibility for HPMS as a new approach to measure the shape of soft and compliant objects.

This paper describes the design concepts, the making of and some applications of the first Estonian Virtual Reality Environment. Using hardware only slightly above the threshold of consumer level, we built a virtual environment (VE) aimed at scientific visualization with the lowest possible space requirements (smaller than a cube with 2 m edge length in total) and budget (approximately below 30.000 €). The system is a fully functional visualization environment that replicates most of the features and properties of a real-sized CAVE-like System, therefore allowing further prototyping and research in the field of Virtual Reality.

While the average frequency of chewing and food intake have been reported before, a detailed description of the pattern of chewing and the cumulative intake of food over the course of a meal have not. In order to achieve this goal, video recording of the maxillary-mandibular region of women eating food from a plate was synchronized with video recording of the plate and computer recording of the weight-loss of the plate. Video recording of chewing correlated strongly with chewing identified by magnetic tracking of jaw displacement in a test with chewing gum at three different frequencies, thus ensuring the validity of video recording of chewing. Weight-loss data were corrected by convolution algorithms, validated against human correction, using sliding window filtering to correct errors with video events as reference points. By use of this method, women ate on average 264 g of food over 114 min, they took an average of 51 mouthfuls during the meal and displayed on average 794 chews with 15 chews per chewing sequence. The number of mouthfuls decreased and the duration of the pauses after each mouthful increased in the middle of the meal and these measures were then restored. The ratio between chewing sequences and subsequent pauses remained stable although the weight of each mouthful decreased by the end of the meal, a measure that is hypothesized to be reflected in a decelerated speed of eating. The method allows this hypothesis to be tested and its implication for clinical intervention to be examined.

We sought to determine the effects of varying the perceptual demands of a suprapostural visual task on the postural activity of children with developmental coordination disorder (DCD), and typically developing children (TDC). Sixty-four (32 per group) children aged between 9 and 10 years participated. In a within-participants design, each child performed a signal detection task at two levels of difficulty, low (LD) and high difficulty (HD). During performance of the signal detection tasks we recorded positional variability of the head and torso using a magnetic tracking system. We found that task difficulty had a greater effect on task performance among the TDC group than among children with DCD. Overall positional variability was greater the DCD group than in the TDC group. In the TDC group, positional variability was reduced during performance of the HD task, relative to sway during performance of the LD task. In the DCD group, positional variability was greater during performance of the HD task than during performance of the LD task. In children, DCD may reduce the strength of functional integration of postural activity with the demands of suprapostural visual tasks.

The LHCb experiment features a particle identification system composed of two RICH detectors, flanked by a magnetic tracking configuration. This system is now being readied for data taking. The first beam is scheduled for 2008. We will discuss the commissioning strategy and point out some key issues and the approach which has been adopted to solve them.

The purpose of this study was to determine whether plane, end-range determination, or scapular motion affects shoulder range-of-motion measurements. In 16 healthy subjects, instrumentation with a magnetic tracking device was used to measure shoulder internal and external range of motion. The arm was supported while it was rotated either actively or passively with a measured torque. There was a significant main effect of plane for internal rotation (P < .001) but not for external rotation (P = .584). Passive humerothoracic motion was significantly greater than active humerothoracic motion for internal rotation (P < .006) and external rotation (P < .01). Active and passive humerothoracic motion was significantly greater than active and passive glenohumeral motion in 6 of the 7 active conditions and all 7 passive conditions (P < .002). Our results suggest that significant amounts of scapulothoracic motion may impact measurements of isolated glenohumeral joint motion.

Bulk patient motion during transthoracic 3-D echocardiography (3DE) produces image plane misregistration and errors in left ventricular (LV) volume and ejection fraction (EF). To correct for patient motion, we used a magnetic locating system to track both the ultrasound transducer and the chest wall of the patient, so images could be registered in a patient-centered coordinate system ("correction"). Fourteen subjects each underwent 3DE, with deliberate patient motion, to measure LV volume and EF. Results were compared to magnetic resonance imaging (MRI). Without correction, 3DE differed significantly from MRI (EF: r = 0.78, SEE = 5.8%). Application of correction increased 3DE accuracy, despite patient motion (EF: r = 0.91, SEE = 3.7%), to a level comparable to that of 3DE in the absence of motion (EF: r = 0.93, SEE = 3.5%). Patient motion during 3DE examination can be corrected using a magnetic spatial location system.

This study was performed to determine whether 3-dimensional echocardiography (3DE) with a magnetic tracking system for image plane localization, which unlike standard 2-dimensional echocardiography (2DE), does not require acquisition of specific image planes or "standard views" for quantitative measurement of left ventricular volume and ejection fraction (EF), could compensate for sonographer inexperience. Eight adults underwent magnetic resonance imaging (MRI) scanning; they also had 2DE and 3DE performed by 2 experienced and 3 novice sonographers. Data were analyzed by a single expert reader blinded to patient and sonographer identity. Linear regression of MRI EF (reference standard) against echocardiographic EF yielded the following results, where RD indicates the residual difference between measured MRI values and those predicted using echocardiographic results: expert 3DE: r = 0.97, RD=2.4%, and r = 0.96, RD=2.8%; novice 3DE: r = 0.83, RD=5.1%, to r = 0.95, RD=4.8%; expert 2DE: r = 0.85, RD=4.8%, and r = 0.86, RD=4.9%; and novice 2DE: r = 0.34, RD=11.7%, to r = 0.69, RD=6.6%. Comparison of error variances indicated that novices who used 3DE equaled the performance of experts who used 2DE, although experts were always more accurate than novices when both used the same echocardiographic method (3DE vs 3DE, 2DE vs 2DE). In a comparison of methods, 3DE was always superior to 2DE, regardless of sonographer experience. Three-dimensional echocardiography allows even novice sonographers to obtain diagnostic-quality data sets, which they were unable to accomplish with 2DE. These results suggest that scanning with 3DE, combined with remote expert interpretation, may be useful in providing echocardiographic services in regions where they are presently unavailable. (J Am Soc Echocardiogr 1999;12:290-9.)

The suitability of a long-range transmitter was evaluated for use with a Polhemus Fastrak® magnetic tracking device in kinesiologic studies. Performance was judged by comparing positional and rotational accuracy to a standard transmitter. Data were obtained at distances of up to 2.7 and 5.0 m for the standard and long-range transmitters, respectively. Use of the long-range transmitter improved system performance allowing reproducible measurements at a greater distance. However, it is necessary to calibrate the system in each new test environment as there can be significant distortion of the magnetic field.

While several different methods have been used to measure carpal kinematics, biplanar radiography is generally considered to be the most accurate and popular one. However, biplanar radiography is tedious and so only pseudo-dynamic kinematics can be measured. Recently, magnetic tracking system has been developed for the measurement of joint kinematics which is versatile and easy to use and so the possibility of measuring motions dynamically. In this study, the capability of a magnetic tracking device to accurately measure carpal kinematics was investigated by comparing it with biplanar radiography. The kinematics of the third metacarpal, scaphoid, and lunate in five fresh cadaveric specimens were measured using both methods as the wrists were placed in eight positions. The finite screw rotation of each bone with respect to the distal radius during selecting the seven wrist motions was calculated for both measuring techniques and compared. In general, the kinematics for all three bones measured by using either magnetic tracking device or biplanar radiography was identical and showed no statistical difference. The averaged differences ranged from 0.0 to 2.0°. These differences were due to the potential effect of the weight of the sensors and the interference of the attaching rod to the surrounding tissue. It is concluded that the application of the magnetic tracking device to carpal kinematics is warranted, if proper technical procedures as suggested are followed.

Undisrupted joint contact areas can be determined based on surface proximity from combined surface geometry and bony kinematics measured with a magnetic tracking device. This technique is useful for evaluating the apparent region of contact in the normal joint. After disruption of the supporting structures or other simulated pathology, the locations and size of the contact region can be compared with the normal condition. However, the contact results may be highly sensitive to measurement errors. In this study, the accuracy of this method was evaluated for three simple geometric objects: (1) a flat plate, (2) a cylinder, and (3) a sphere, all in contact with a flat surface. The results indicated the contact can be determined within an average proximity of 0.16 ± 0.01 mm (mean ± standard error) with the flat plate, 0.07 ± 0.02 mm with the cylinder, and 0.06 ± 0.08 mm with the sphere. The proximity values are nearly the same as the translational accuracy of the equipment, and might be used as thresholds for in vitro studies.

INTRODUCTION AND OBJECTIVES: Minimal invasive urologic surgery may benefit from ergonomic motion analysis, as the surgeonAEs joints are often in non-optimal positions, leading to premature fatigue. We propse to examine and compare the ergonomics of simulated single-site surgery and conventional laparoscopic surgery. METHODS: A laparoscopic box trainer is used to simulate surgical conditions. To simulate conventional laparoscopic surgery, two instruments are inserted bilaterally and the camera in the center position. Single site surgery is simulated by inserting an Endocone (Karl Storz, Germany) in the center position and inserting a double bent grasper, a straight grasper and the camera through it. Standard laparoscopic training tasks (object transfer, knot tying) are performed and ergonomic data is captured. Magnetic tracking technology is used to obtain position and orientation data for the operatorAEs wrists, elbows and shoulders at a rate of thirty times per second. The data is inserted into an algorithm which calculates the ergonomic scores for each posture throughout the execution of the laparoscopic task. At the end, the algorithm can compare the ergonomic performance of different laparoscopic methods using the analyzed scores. The analysis is based on the RULA method (Rapid Upper Limb Assessment). RESULTS: Preliminary analysis of the data show that joints are in non-optimal positions in single site surgery, as compared to conventional laparoscopic surgery. This is demonstrated by the higher arm and wrist RULA scores obtained for tasks conducted through the single port systems (Test 10) in comparison to tasks conducted through a conventional laparoscopic setup (Test 1). CONCLUSIONS: Ergonomic motion analysis may yield results that lead to the improvement of minimal invasive surgical techniques and equipment.

Majorana neutrinos are postulated in both theories of the neutrinoless double beta decay ( 0 ν β β ) and the seesaw mechanism. The observation of 0 ν β β would be an evidence of the seesaw mechanism. The DCBA experiment measures the kinetic energy of individual beta ray in double beta decays with powerful background rejection capability. For the future project, Magnetic Tracking Detector (MTD) is designed on the basis of DCBA-T2 and T3.

Although three-dimensional (3D) echocardiography has been used to measure mitral valve areas (MVA) in mitral stanosis from both transescphageal (TEE) and transthoracic (TTE) approaches, the accuracy of these techniques has not been compared. Accordingly, we compared the accuracy of mitral valve area measurements obtained with a 3D volumetric free-hand (FH) TEE approach to those acquired with a 3D TEE approach using invasive Gorlin mitral valve area as the "gold standard". Methods: 19 patients (49±18 yrs) with mitral stenosis were studied with TEE and free-hand TEE prior to valvuIoplasfy. During TEE, 2D images were acquired every 3 ° over 180 ° (SONOS 5500). Freehand images were obtained in 80 planes gated to respiration and heart rate using magnetic tracking, and processed on Omniview (TomTec). Direct 3D mitral valve area measurements reconstructed from TEE and free-hand TEE were compared to invasive Gorlin mitral valve area. Results: Both 3D techniques, free*hand TEE and TEE, were in good agreement with invasive data (Bland-AItmann and correlation, figure). Conclusions. Mitral valve orifice area measurements obtained with free-hand TEE scanning are as accurate as those obtained with 3D TEE, with the advantages of being noninvasive and suitable for serial measurements.