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PubMed2005

Contact force measurement of instruments for force-feedback on a surgical robot: acceleration force cancellations based on acceleration sensor readings.

For delicate operations conducted using surgical robot systems, surgeons need to receive information regarding the contact forces on the tips of surgical instruments. For the detection of this contact force, one of the authors previously proposed a new method, called the overcoat method, in which the instrument is supported by sensors positioned on the overcoat pipe. This method requires cancellation of the acceleration forces of the instrument/holder attached to the overcoat sensor. In the present report, the authors attempt to use acceleration sensors to obtain the acceleration forces of the instrument/holder. The new cancellation method provides a force-detection accuracy of approximately 0.05-0.1 N for a dynamic response range of up to approximately 20 Hz, compared to approximately 1 Hz, which was achieved by using acceleration forces based on the theoretical robot motion.

Acceleration↗
PubMed1997

Eye movements induced by lateral acceleration steps. Effect of visual context and acceleration levels.

Eye movement responses were obtained from six normal subjects exposed to randomly ordered rightwards/leftwards linear acceleration steps of 0.05 g, 0.1 g or 0.24 g amplitude and 650 ms duration along the interaural axis. With the instruction to gaze passively into the darkness, compensatory nystagmus was evoked with slow-phase velocity sensitivity of 49 degrees s(-1) g(-1). When subjects viewed earth-fixed targets at 30 cm, 60 cm or 280 cm, eye movements at 130 ms from motion onset were proportional to acceleration and inversely proportional to target distance, before the onset of visually guided eye movements. Our results show that a modulation with viewing distances of the earliest human otolith-ocular reflexes occurs in the presence of pure linear acceleration. However, full compensation was not attained for the nearer targets and higher accelerations.

Acceleration↗
PubMed1979

Influence of the ambient acceleration field upon acute acceleration tolerance in chickens.

It has been demonstrated both in the Russian and in the American space programs that there is a progressive deconditioning of the circulatory system with exposure to weightlessness. Astronauts and cosmonauts returned to Earth have a significantly reduced orthostatic tolerance which will persist for a few days. We have measured the acceleration tolerance of domestic fowl, acutely exposed to a 6 g+z field, as the time over which a normal heart rate can be maintained. This period of circulatory accommodation ends abruptly with a marked bradycardia, which with continued treatment is terminal. For animals which have been previously chronically accelerated (e.g., physiologically adapted to a 2.5 g field) the acute acceleration tolerance is greatly increased. It appears that the influence of the ambient acceleration field in conditioning the responsiveness of the circulatory system is a general phenomenon.

Acceleration↗
PubMed1970

Response of semicircular canal dependent units in vestibular nuclei to rotation of a linear acceleration vector without angular acceleration.

1. Recent experiments have shown that rotation of a linear acceleration vector round the head can generate involuntary ocular nystagmus in the absence of angular acceleration. The present experiments examine the suggestion that adequate stimulation of the semicircular canals may contribute to this response.2. Decerebrate cats were located in a stereotaxic device on a platform, slung from four parallel cables, which could be driven smoothly round a circular orbit without inducing significant angular movement of the platform. This Parallel Swing Rotation (PSR) generated a centripetal acceleration of 4.4 m/sec(2) which rotated round the head at 0.52 rev/sec.3. The discharge frequency of specifically lateral canal-dependent neural units in the vestibular nuclei of cats was recorded during PSR to right and left, and in the absence of motion. The dynamic responses to purely angular motion were also examined on a servo-driven turntable.4. Without exception all proven canal-dependent cells examined (twenty-nine cells in nine cats) were more active during PSR in the direction of endolymph circulation assessed to be excitatory to the unit, than during PSR in the opposite direction.5. The observed changes in discharge frequency are assessed to have been of a magnitude appropriate for the generation of the involuntary oculomotor response induced by the same stimulus in the intact animal.6. The findings suggest that a linear acceleration vector which rotates in the plane of the lateral semicircular canals can be an adequate stimulus to ampullary receptors, though an explanation which invokes the modulation of canal cells by a signal dependent upon the sequential activation of macular receptors cannot be positively excluded.

Acceleration↗
PubMed1981

Symposium on low frequency harmonic acceleration, the rotatory chair. Responses to low-frequency harmonic acceleration in patients with acoustic neuromas.

There has been increased interest in harmonic acceleration (HA) for the evaluation of vestibular pathology in recent years. The purpose of this study was to determine the value of harmonic acceleration testing in 24 patients with surgically proven acoustic neuromas. All patients were tested preoperatively and postoperatively, and none were lost to follow-up. Thirteen were tested one year or more after surgery. For rotational evaluation, each patient was seated in an enclosed chair driven by a D.C. torque motor turntable system and rotated utilizing five low frequency sinusoids (.01 - .16 Hz). Slow eye movements in response to acceleration were analyzed by analog and digital computer techniques. Output measures were the phase relationships between the input stimulus velocity and the slow phase eye movement velocity and labyrinthine preponderance (LP) or asymmetry. Preoperative results showed that caloric examination identified 79% of patients with tumors and HA 67% (2 standard deviation criteria). When both tests were evaluated together they identified 91% of all patients with tumors. Of the 4 small tumors (less than 2 cm), HA identified 4 and caloric examination 2. All patients were tested approximately 7 days postoperatively and had statistically significant shifts in their phase and LP measures. The shifts in phase were stable up to 3 years after surgery; however, the LP returned toward normal values. These findings indicate that the vestibular system can compensate but not repair itself after the loss of one labyrinth. In those patients who continued to be symptomatic 1 year or more after surgery, the LP did not return to normal values. Harmonic acceleration testing complemented caloric testing in the identification of patients with tumors and objectively demonstrated patients with continued symptomatology after surgery.

Acceleration↗
PubMed1996

Accelerated loss of telomeric repeats may not explain accelerated replicative decline of Werner syndrome cells.

The Werner syndrome (WS) is characterized by the premature onset and accelerated rate of development of major geriatric disorders, including atherosclerosis, diabetes mellitus, osteoporosis, ocular cataracts, and various neoplasms. Cultures of WS skin-fibroblastlike cells have been previously shown to undergo accelerated rates of decline of the replicative potentials and to exhibit variegated chromosomal translocations and deletions. Since the replicative decline of normal somatic cells is associated with a loss of telomeric repeats, we investigated the kinetics of telomeric repeat loss in WS cells. The mean length of telomere restriction fragments (TRF) from the earliest passages of WS cells studied was not shorter than those of controls, possibly reflecting selective pressure for subsets of cells with relatively high residual replicative capacity. Statistical evidence indicated an accelerated shortening of TRF length in serially passaged WS cultures, but the mean TRF lengths of WS cultures that had ceased replicating were significantly longer than those of senescent controls. Thus, while accelerated loss of telomeric repeats could potentially explain the rapid decline in proliferation of WS cells, it is possible that WS cells exit the cell cycle via mechanisms that differ from those of replicatively senescent cells from control subjects.

Adult↗
PubMedDate not supplied

Acceleration of chromosome aberrations in senescence-accelerated strains of mice.

Age-related changes in the frequency of chromosome aberrations were examined using bone marrow cells of senescence-accelerated strains of mice (SAM). An accelerated senescence-prone strain, SAM-P/1, showed a striking increase in the frequency of chromosome aberrations, from age 3 to 8 months, whereas an accelerated senescence-resistant strain, SAM-R/1, at the same ages showed only a slight increase. Both these strains were derived from the same ancestral strain (AKR/J). The rate of increase of chromosome aberration frequency paralleled the advancement of senescence in both strains. These observations suggest that there are genetic factors which closely relate to chromosomal instability and acceleration of the senescence processes.

Aging↗
PubMed2005

The influence of the type of accelerant, type of burned material, time of burning and availability of air on the possibility of detection of accelerants traces.

The presented research consisted in a series of field experiments and laboratory analyses of obtained samples. Their aim was to investigate how different factors influence the possibility of identification of accelerant traces in conditions that are as similar as possible to those of real fires. The studied factors were: type of burned material, type of accelerant, length of time between lighting and extinguishing of fire and the air availability level. The obtained results show that, among investigated factors, the type of burned material has the greatest influence. The other factors, with regard to their influence, could be ranked in descending order as follows: 'other' (hard to determine and regulate factors), type of accelerant, time of burning and air availability. 'Other' factors include arrangement of the burned material and dispersion of the accelerant.

Journal Article↗
PubMed1999

Smart (simultaneous modulated accelerated radiation therapy) boost: a new accelerated fractionation schedule for the treatment of head and neck cancer with intensity modulated radiotherapy.

PURPOSE: To report the initial experience in the definitive treatment of head and neck carcinomas using SMART (Simultaneous Modulated Accelerated Radiation Therapy) boost technique. Radiation was delivered via IMRT (Intensity Modulated Radiotherapy). The following parameters were evaluated: acute toxicity, initial tumor response, clinical feasibility, dosimetry and cost. METHODS AND MATERIALS: Between January 1996 and December 1997, 20 patients with primary head and neck carcinomas were treated with SMART boost technique. The treatment fields encompassed two simultaneous targets. The primary target included palpable and visible disease sites. The secondary target included regions at risk for microscopic disease. Daily fractions of 2.4 Gy and 2 Gy were prescribed and delivered to the primary and secondary targets to a total dose of 60 Gy and 50 Gy, respectively. Lower neck nodes were treated with a single conventional anterior portal. This fractionation schedule was completed in 5 weeks with 5 daily fractions weekly. Toxicity was evaluated by RTOG acute toxicity grading criteria, evidence of infection at immobilization screw sites, subjective salivary function, weight loss, and the need for treatment split. Mean follow-up was 15.2 months. Initial tumor response was assessed by clinical and radiographical examinations. Clinical feasibility was evaluated by the criteria: time to treat patient, immobilization, and treatment planning and QA time. In dosimetry, we evaluated the mean doses of both targets and normal tissues and percent targets' volume below goal. To evaluate cost, Medicare allowable charge for SMART boost was compared to those of conventional fractionated and accelerated radiotherapy. RESULTS: ACUTE TOXICITY: None of the patients had a screw site infection and all patients healed well after completion of radiotherapy. Sixteen of 20 patients (80%) completed the treatment within 40 days without any split. Sixteen patients (80%) had RTOG Grade 3 mucositis while 10 patients (50%) had Grade 3 pharyngitis. Three of 20 patients (15%) had weight loss greater than 10% of their pretreatment weight. Ten patients (50%) required intravenous fluids, tube feeding or both. Nine patients (45%) reported moderate xerostomia with significant relief reported within 6 months. INITIAL TUMOR RESPONSE: 19 patients (95 %) had complete response (CR) while one had partial response (PR). The patient with PR had stable disease on imaging at 12 months follow-up. Two patients were found to have lung metastases at 2 months and 5 months follow-up. To date, there have been two local recurrences in the complete responders. Both patients had nasopharyngeal primary; one was retreated with radioactive Cesium-137 implant and the other died from the disease. CLINICAL FEASIBILITY: The average treatment time for a three-arc treatment was 17.5 minutes and 2.5 minutes for each additional arc. Eleven patients (55%) had four-arc treatment while six patients (30%) had five-arc treatment and three patients (15%) had three-arc treatment. Immobilization was reproducible within less than 2 mm. The treatment planning, QA and documentation prior to treatment averaged 2 days. DOSIMETRY: The mean doses to the primary and secondary targets were 64.4 Gy and 54.4 Gy, respectively; 8.9% of the primary target volume and 11.6% of the secondary target volume were below prescribed dose goal. The mean dose delivered to the mandible was 30 Gy, spinal cord 17 Gy, ipsilateral parotid 23 Gy, and contralateral parotid 21 Gy. COST: Total Medicare allowable charge for SMART boost was $7000 compared to $8600 (conventional) and $9400 (accelerated fractionation). CONCLUSIONS: SMART boost technique is an accelerated radiotherapy scheme that can be delivered with acceptable toxicity. It allows parotid sparing as evidenced both clinically and by dosimetry. Initial tumor response has been encouraging. It is clinically feasible and cost saving. A larger population of patients and a long-term fol

Aged↗
PubMed1988

Assessment of neuromuscular transmission by the evoked acceleration response. An evaluation of the accuracy of the acceleration transducer in comparison with a force displacement transducer.

This paper presents preliminary observations on an acceleration-responsive transducer designed to monitor neuromuscular transmission. Simultaneously evoked acceleration and tension responses of the adductor pollicis muscles were studied. Registrations were obtained during recovery from atracurium-induced block in 29 individuals in neurolept II anaesthesia (Group I) and in 4 ICU patients (Group II) sedated with pentobarbital or midazolam. Regression analysis of 1567 train-of-four (TOF) registrations, in regard to TOF-ratio (T4/T1) and first twitch ratio (T1/T0), demonstrated regression coefficients (b) and correlation coefficients (r) in the range 0.91-1.06 and 0.89-0.98, respectively. During 1 Hz single twitch stimulation and post-tetanic count stimulation, b and r were in the range 0.85-1.03 and 0.77-0.90, respectively. Following administration of edrophonium (n = 6, Group I) a deviation of T1/T0 regression values was observed in four individuals, i.e. 0.48 (b) and 0.56 (r). This investigation proved a good level of accuracy of the acceleration transducer compared to the force displacement transducer during spontaneous and neostigmine-induced recovery from atracurium block. The acceleration transducer-based system does not require a rigid suspension and seems to have a good monitoring potential in clinical assessment of neuromuscular transmission.

Adult↗
PubMed1995

Influence of target distance and acceleration level on eye movements evoked by lateral acceleration steps.

Lateral eye movements produced by linear acceleration along the inter-aural axis were studied in 6 normal subjects. They were seated upright, whole-body restrained, and were exposed to randomised rightward/leftward steps of 0.05 g. 0.1 g, 0.24 g of 600 ms duration. When viewing earth-fixed targets at 30, 60 or 280 cm from their eyes, mainly pure compensatory slow-phase eye movements were evoked at latencies around 50 ms measured for the closest viewing distances. At onset, slow-phase amplitude was modulated by acceleration and target distance. When the subjects were stationary and pursued moving targets at similar distances and accelerations, latencies around 140 ms were observed, and catch-up saccades were frequently made. From these experiments, we defined the dynamics of the otolith-ocular reflex for various levels of acceleration and viewing distances.

Adult↗
PubMed1996

Torque, total work, power, torque acceleration energy and acceleration time assessed on a dynamometer: reliability of knee and elbow extensor and flexor strength measurements.

Isometric torque and isokinetic peak torque, total work, power, torque acceleration energy and acceleration time at 30, 120 and 240 degrees.s-1 of the knee and elbow extensors and flexors were measured using an isokinetic dynamometer in 24 healthy women. Intrasession variation of the measurements was evaluated and the short-term and long-term reliability was assessed by repeating all procedures after averages of 2 and 30 days, respectively. The effect of learning on peak torque during a session was also evaluated. Moreover, the effect of general warming-up on knee extensor and flexor strength was examined on a separate day. Using correlations, numerous studies have indicated that muscle strength measurements are reliable. Correlations, however, are inappropriate and misleading in studies on reliability. In the present study reliability of each strength variable was expressed as the coefficient of variation (CV). With the protocol used, neither learning nor warming-up had any significant effect on strength. As expected, intra-session variation tended to be less than short-term and long-term inter-session variation. The CVs for strength variables measured 30 days apart exceeded 5% for all variables and rose to 107% for acceleration time. Substantial between-subject variation of individual CVs were found. The study demonstrated that muscle strength measurements may be highly unreliable in the individual subject.

Acceleration↗
PubMed1993

Encoding of head acceleration in vestibular neurons. I. Spatiotemporal response properties to linear acceleration.

1. Extracellular recordings were made in and around the medial vestibular nuclei in decerebrated rats. Neurons were functionally identified according to their semicircular canal input on the basis of their responses to angular head rotations around the yaw, pitch, and roll head axes. Those cells responding to angular acceleration were classified as either horizontal semicircular canal-related (HC) or vertical semicircular canal-related (VC) neurons. The HC neurons were further characterized as either type I or type II, depending on the direction of rotation producing excitation. Cells that lacked a response to angular head acceleration, but exhibited sensitivity to a change in head position, were classified as purely otolith organ-related (OTO) neurons. All vestibular neurons were then tested for their response to sinusoidal linear translation in the horizontal head plane. 2. Convergence of macular and canal inputs onto central vestibular nuclei neurons occurred in 73% of the type I HC, 79% of the type II HC, and 86% of the VC neurons. Out of the 223 neurons identified as receiving macular input, 94 neurons were further studied, and their spatiotemporal response properties to sinusoidal stimulation with pure linear acceleration were quantified. Data were obtained from 33 type I HC, 22 type II HC, 22 VC, and 17 OTO neurons. 3. For each neuron the angle of the translational stimulus vector was varied by 15, 30, or 45 degrees increments in the horizontal head plane. In all tested neurons, a direction of maximum sensitivity was identified. An interesting difference among neurons was their response to translation along the direction perpendicular to that that produced the maximum response ("null" direction). For the majority of neurons tested, it was possible to evoke a nonzero response during stimulation along the null direction always had response phases that varied as a function of stimulus direction. 4. These spatiotemporal response properties were quantified in two independent ways. First, the data were evaluated on the basis of the traditional one-dimensional principle governed by the "cosine gain rule" and constant response phase at different stimulus orientations. Second, the response gain and phase values that were empirically determined for each orientation of the applied linear stimulus vector were fitted on the basis of a newly developed formalism that treats neuronal responses as exhibiting two-dimensional spatial sensitivity. Thus two response vectors were determined for each neuron on the basis of its response gain and phase at different stimulus directions in the horizontal head plane.(ABSTRACT TRUNCATED AT 400 WORDS)

Acceleration↗
PubMed1978

[Linear accelerators in oncoradiology. Comparison of the effciency of four clinically utilized electron linear accelerators with energies up to 20 MeV (author's transl)].

Further development of linear accelerators for medical purposes results in leaving off the principle of circular acceleration. The present investigation, comparing four clinically utilized electron linear accelerators with different constructional systems, reveals a large scale of clinical applicability, advantages and disadvantages partly compensating one another. None of the four machines examined offers a total of decisive advantages as compared to the other ones. Some essential data from the side of radiation exit are tested: depth dose data and photon contamination during operation with electrons, field sizes and homogeneity, penumbral width and penetration power for electron and X radiations. The appreciation of electron therapy by the radiologist may be a factor as well the handling of the machine, but in many cases the space available in an existing locality or the confidence in the ready service of a contracting firm, considerations concerning failure periods, estimate of repair and subsequent costs are influencing the decision for a certain type of equipment.

Electrons↗
PubMed2000

Acceleration of fresh fracture repair using the sonic accelerated fracture healing system (SAFHS): a review.

The Sonic Accelerated Fracture Healing System (SAFHS) is a relatively new fracture management tool which incorporates the application of a specifically modified diagnostic ultrasound unit to healing fractures with the intention of accelerating repair. In an animal fracture model, this device has been shown to accelerate the rate of biomechanical healing by a factor of 1.4-1.6. In two randomized, controlled trials in humans, the same unit has been shown to reduce the time frame of clinical and radiographic healing by 38%. In the two fracture regions investigated, tibial diaphysis and distal radius, this represented a 58 day and 37 day reduction in healing time, respectively. Despite its effect on the entire process of fresh fracture repair, the effect of the SAFHS on the individual stages and processes involved has not been established. This paper reviews these stages and processes, and discusses the clinical and practical implications of the effect of the SAFHS on fracture repair and the need for further research into this modality.

Animals↗
PubMed1995

The rationale to switch from postoperative hyperfractionated accelerated radiotherapy to preoperative hyperfractionated accelerated radiotherapy in rectal cancer.

PURPOSE: To demonstrate the feasibility of preoperative Hyperfractionated Accelerated RadioTherapy (preop-HART) in rectal cancer and to explain the rationales to switch from postoperative HART to preoperative HART. METHODS AND MATERIALS: Fifty-two consecutive patients were introduced in successive Phase I trials since 1989. In trial 89-01, postoperative HART (48 Gy in 3 weeks) was applied in 20 patients. In nine patients with locally advanced rectal cancer, considered unresectable by the surgeon, 32 Gy in 2 weeks was applied prior to surgery (trial 89-02). Since 1991, 41.6 Gy in 2.5 weeks has been applied preoperatively to 23 patients with T3-T4 any N rectal cancer immediately followed by surgery (trial 91-01). All patients were irradiated at the department of radiation-oncology with a four-field box technique (1.6 Gy twice a day and with at least a 6-h interval between fractions). The minimal accelerating potential was 6 MV. Acute toxicity was scored according to the World Health Organization (WHO for skin and small bowel) and the Radiation Therapy Oncology Group criteria (RTOG for bladder). This was done weekly during treatment and every 3 months thereafter. Small bowel volume was estimated by a modified "Gallagher's" method. RESULTS: Acute toxicity was acceptable both in postoperative and preoperative setup. The mean acute toxicity was significantly lower in trial 91-01 compared to 89-01. This difference was due to the smaller amount of small bowel in irradiation field and lower total dose in trial 91-01. Moreover, there was a significantly reduced delay between surgery and radiotherapy favoring trial 91-01 (median delay 4 days compared to 46 days in trial 89-01). Nearly all patients in trial 89-02 and 91-01 underwent surgery (31 out of 32; 97%). Resection margins were negative in 29 out of 32. Hospitalization duration in trial 91-01 was not significantly different from trial 89-01 (19 vs. 21 days, respectively). CONCLUSIONS: Hyperfractionated accelerated radiotherapy immediately followed by surgery is feasible as far as acute toxicity is concerned. Preoperative HART is favored by a significantly lower acute toxicity related, in part, to a smaller amount of irradiated small bowel, and a shorter duration of the delay between radiotherapy and surgery. Moreover, the hospital stay after preoperative HART is not significantly increased.

Adult↗
PubMed2000

Age-associated DNA damage is accelerated in the senescence-accelerated mice.

We investigated how the DNA status correlates with the aging process in organisms, in different organs and in tissues using two inbred strains of mice, which are genetically related but have different senescence patterns. The SAMP1 mice belong to an accelerated senescence-prone and short lived strain, the other, SAMR1 mice are from an accelerated senescence-resistant and long lived strain. Using the alkaline filter elution technique, pieces of tissues from six organs: lung, intestine, liver, brain, muscle, and heart have been examined for DNA damage, mainly DNA single strand breaks. It was shown that in newborns the DNA damage is minimal, and it was increased significantly with calendric age in all organs in both strains. Although the correlation of DNA damage with aging differed in the different six organs, damage was significantly higher in SAMP1 mice than SAMR1 mice at later life in all organs. This is another remarkable example for the strong correlation of DNA damage and aging process, especially with senescence acceleration.

Aging↗
PubMed2000

A combination of EGF and IGF-I accelerates the progression of meiosis in bovine follicular oocytes in vitro and fetal calf serum neutralizes the acceleration effect.

The effects of a combination of EGF and IGF-I (GFs) on the progress of meiosis and on their developmental competence were examined in cumulus-enclosed bovine oocytes. Exposure to GFs in serum-free, 0.3% PVP-containing maturation medium significantly (P<0.05) increased the frequency of oocytes with the first polar body (PB) at 16 h of culture and decreased those with PB at 20 h. The cleavage rates of PB-extruded oocytes after fertilization were not affected by treatment of GFs during maturation culture, and blastocyst yield was not improved by GFs treatment. Although replacement of PVP from GFs-containing medium with fatty acid-free BSA did not affect the timing of PB extrusion, replacement with 10% FCS neutralized the acceleration effects of GFs. Replacement for macromolecule in maturation medium did not improve blastocyst yield of PB-extruded oocytes after fertilization. These results indicate that the progression of meiosis in bovine oocytes with cumulus cells is accelerated by exposure to GFs in serum-free maturation medium but their developmental competence is not improved, and that the acceleration effects on the progress of meiosis is neutralized by the presence of FCS in maturation medium with no improvement of developmental competence after in vitro fertilization.

Animals↗