PURPOSE: The aim of this study was to introduce a method of obtaining the oscillation graphs of the dental x-ray tube heads relative to time using an accelerometer. MATERIALS AND METHODS: An Accelerometer, Piezotron type 8704B25 (Kistler Instrument Co., Amherst, NY, USA) was utilized to measure the horizontal oscillation of the x-ray tube head immediately after positioning the tube head for an intraoral radiograph. The signal from the sensor was transferred to a dynamic signal analyzer, which displayed the magnitude of the acceleration on the Y-axis and time lapse on the X-axis. The horizontal oscillation of the tube head was measured relative to time, and the settling time was also determined on the basis of the acceleration graphs for 6 wall type, 5 floor-fixed type, and 4 mobile type dental x-ray machines. RESULTS: The oscillation graphs showed that tube head movement decreased rapidly over time. The settling time varied with x-ray machine types. Wall-type x-ray machines had a settling time of up to 6 seconds, 5 seconds for fixed floor-types, and 11 seconds for the mobile-types. CONCLUSION: Using an accelerometer, we obtained the oscillation graphs of the dental x-ray tube head relative to time. The oscillation graph with time can guide the operator to decide upon the optimum exposure moment after xray tube head positioning for better radiographic resolution.
Acceleration ; Head Movements ; Head* ; Radiography

PURPOSE: The aim of this study was to introduce a method of obtaining the oscillation graphs of the dental x-ray tube heads relative to time using an accelerometer. MATERIALS AND METHODS: An Accelerometer, Piezotron type 8704B25 (Kistler Instrument Co., Amherst, NY, USA) was utilized to measure the horizontal oscillation of the x-ray tube head immediately after positioning the tube head for an intraoral radiograph. The signal from the sensor was transferred to a dynamic signal analyzer, which displayed the magnitude of the acceleration on the Y-axis and time lapse on the X-axis. The horizontal oscillation of the tube head was measured relative to time, and the settling time was also determined on the basis of the acceleration graphs for 6 wall type, 5 floor-fixed type, and 4 mobile type dental x-ray machines. RESULTS: The oscillation graphs showed that tube head movement decreased rapidly over time. The settling time varied with x-ray machine types. Wall-type x-ray machines had a settling time of up to 6 seconds, 5 seconds for fixed floor-types, and 11 seconds for the mobile-types. CONCLUSION: Using an accelerometer, we obtained the oscillation graphs of the dental x-ray tube head relative to time. The oscillation graph with time can guide the operator to decide upon the optimum exposure moment after xray tube head positioning for better radiographic resolution.
Acceleration ; Head Movements ; Head* ; Radiography

PURPOSE: To describe that Computer image recognition technique is more accurately and less invasive than other methods, which using contact lens with a search probe or electrodes for record of eye movements. METHODS: A reference marker which was infrared was attached to the center of the forehead of the patients and the infrared light was illuminated to both eyes. Video image sequences were recorded using digital CCD camera and the captured image frames (640 X 480) were processed using a image analysis program. From which each image frame captured, pupil area was saperated using difference of brightness in pupil and iris. And then the pupil center was determined by calculating the center-of-mass of black pixels to meet the pupil threshold criteria. RESULTS: In a post-processing process, we could acquire horizontal and vertical eye position and velocity data. Inverse fast fourier transformation(FFT) and digital filtering algorithm were applied to filter out noise due to limited resolution of the CCD camera and sampling rates. Experimental result showed that the system could detect about 0.2mm positional location and 30Hz horizontal and vertical eye movements simultaneously. CONCLUSIONS: We could accurately measure and record two dimensional eye movements of patients (horizontal and vertical simultaneously) in real time with some head movements.
Electrodes ; Eye Movements* ; Forehead ; Head Movements ; Humans ; Iris ; Noise ; Pupil

BACKGROUND: The proper cuff pressure is important to prevent complications related to the endotracheal tube (ETT). We evaluated the change in ETT cuff pressure by changing the position from supine to prone without head movement. METHODS: Fifty-five patients were enrolled and scheduled for lumbar spine surgery. Neutral angle, which was the angle on the mandibular angle between the neck midline and mandibular inferior border, was measured. The initial neutral pressure of the ETT cuff was measured, and the cuff pressure was subsequently adjusted to 26 cmH2O. Flexed or extended angles and cuff pressure were measured in both supine and prone positions, when the patient's head was flexed or extended. Initial neutral pressure in prone was compared with adjusted neutral pressure (26 cmH2O) in supine. Flexed and extended pressure were compared with adjusted neutral pressure in supine or prone, respectively. RESULTS: There were no differences between supine and prone position for neutral, flexed, and extended angles. The initial neutral pressure increased after changing position from supine to prone (26.0 vs. 31.5 +/- 5.9 cmH2O, P < 0.001). Flexed and extended pressure in supine were increased to 38.7 +/- 6.7 (P < 0.001) and 26.7 +/- 4.7 cmH2O (not statistically significant) than the adjusted neutral pressure. Flexed and extended pressure in prone were increased to 40.5 +/- 8.8 (P < 0.001) and 29.9 +/- 8.7 cmH2O (P = 0.002) than the adjusted neutral pressure. CONCLUSIONS: The position change from supine to prone without head movement can cause a change in ETT cuff pressure.
Head Movements ; Head* ; Humans ; Neck ; Prone Position ; Spine

BACKGROUND AND OBJECTIVES: Active head rotation test measures vestibulo-ocular reflex at frequencies of 1 Hz to 8 Hz which correspond to the frequencies of head movements in daily living. However, the normative data of several authors are not in unity, and the usefulness of the test in the evaluation of the peripheral vestibulopathy is yet to be determined. The purpose of this study is to make our own normative data using our own testing condition and facilities and to evaluate the usefulness of the test in the evaluation of the peripheral vestibulopathy. MATERIALS AND METHODS: Active head rotation test was performed in 22 controls and 34 peripheral vestibulopathy patients (24 unilateral, 10 bilateral) using the VORTEQ system in darkness with eyes open (VOR-EO). Gain, phase and symmetry were compared between the control group and the patient groups. RESULTS: The control group showed the gain of 1.0 to 1.1 at frequencies of 1 Hz to 4 Hz. Phase was between 4 to 7 degrees, and symmetry was close to zero. Unilateral vestibulopathy group did not show a significant difference in gain, phase and symmetry from the normal group at the majority of frequencies. Bilateral vestibulopathy group showed a significant gain reduction compared to the normal group and unilateral group (p<0.05). But phase and symmetry were not significantly different. CONCLUSION: The active head rotation test was not useful in evaluating unilateral peripheral vestibulopathy although it was useful in assessing funcitonal deficit of VOR in bilateral vestibulopathy.
Darkness ; Head Movements ; Head* ; Humans ; Reflex, Vestibulo-Ocular

BACKGROUND AND OBJECTIVES: The conventional instrument for video head impulse test (vHIT) records the movement of the right eye only. The aim of this study was to evaluate the changes in the gain of vHIT results qdue to different directions of head rotation directons at different target distances and rotation speeds. SUBJECTS AND METHOD: Horizontal head impulse was recorded by vHIT in 20 normal subjects. vestibulo-ocular reflex (VOR) gains to the right and left directions were compared at different test conditions. Two different impulses with low (50-150 deg/sec) and high (200-300 deg/sec) peak-head-velocities were tested and the subjects were also instructed to fixate a laser dot on a screen at different distances of 60, 100, and 200 cm. Eye movements were recorded on the right eye. RESULTS: Regardless of the target distances and peak-head-velocities, the VOR gains to the rightward head rotation were significantly greater than those to the leftward head rotation. In more than 85% of normal subjects, vHIT gain to the rightward head rotation was greater than that to the leftward head rotation. Mean gain asymmetries were 2.16-3.33% and the mean interaural vHIT gain differences were 0.04-0.07. CONCLUSION: Regardless of the target distances and peak-head-velocities, the VOR gains to the rightward head rotation were significantly greater than those to the leftward head rotation. Directional asymmetry of VOR gain should be considered when interpreting vHIT results in patients with vestibular disorders.
Eye Movements ; Head Impulse Test* ; Head* ; Humans ; Reflex, Vestibulo-Ocular

Loupes-assisted microsurgery often needs an operational head lamp for a better condition of light. This may cause serious neck fatigue due to the weight the operational head lamp, the limitation of the operator's head movement from the hind cable, and some cost for purchasing and management of it. On the contrary, a mountain head lamp is very light, full of freedom in movement, applicable to all types of loupes, and relatively very cheap. In conclusion, a mountain head lame can be a cost-effective light source for Loupes-assisted microsurgery.
Fatigue ; Freedom ; Head ; Head Movements ; Light ; Microsurgery ; Neck

BACKGROUND AND OBJECTIVES: Vestibulo-ocular reflex (VOR) is the mechanism for the production of rapid compensatory eye movement during head movements. VOR gain can adapt to a change in visual stimulation, which is called adaptive plasticity. To investigate the adaptation of VOR to concave spectacle lens, the authors compared the diopters with VOR gain changes. MATERIALS AND METHODS: Calibration and sinusoidal harmonic acceleration (SHA) rotation tests at 0.01, 0.04 and 0.16 Hz were performed on 24 volunteer subjects wearing myopic lenses, with glasses on and off. RESULTS: VOR gains of patients with glasses-on were significantly greater, compared with those without glasses. Correlation between diopters and gain change ratio was significant, especially at low frequencies. CONCLUSION: Long-term wearing of myopic lenses induced VOR gain reduction, which is proportioned to the diopter of the lenses.
Acceleration ; Calibration ; Eye Movements ; Eyeglasses ; Glass ; Head Movements ; Humans ; Photic Stimulation ; Plastics ; Reflex, Vestibulo-Ocular* ; Volunteers

The Viewing Wand is a frameless stereotactic device to provide image-based intraoperative navigation, allowing accurate neurosurgical planning and procedures. The authors applied the frameless stereotactic device called "ISG Viewing Wand" to 30 cases of intracranial lesions and evaluated for its usefulness and limitation. The Viewing Wand was used in 3 cases in conjunction with CT and 27 cases with MRI. The actual error of this system after the registration was judged by the operating surgeon to be less than 2mm in CT or MR image. The useful registrations were possible in 25(83%) out of 30 cases. But it was not useful in 5 cases, because of movement of fiducial markers in 2 cases and head movement after registration in 3 cases. In 25 cases having useful registration, the wand was helpful to localize the lesion for designing the scalp incision and bone flap, as well as the extent of surgical resection of lesions. As a whole, the viewing wand was found to be reliable and accurate. The system is a useful navigational aid that allows a direct approach to intracranial pathology without the drawbacks of application and the limitations of a frame-based stereotactic device.
Fiducial Markers ; Head Movements ; Magnetic Resonance Imaging ; Neuronavigation* ; Pathology ; Scalp

Bilateral vestibular deficit affects far fewer patients than unilateral deficit, and thus has been understudied. When bilateral vestibular organs are injured, loss of input of vestibulo-ocular and vestibulo-spinal reflex that normally stabilize the eyes and body, affected patients suffer blurred vision during head movement, postural instability, and disequilibrium. Vestibular rehabilitation therapy is an exercise-based treatment program designed to promote vestibular adaptation and substitution. The rationale for the exercises, which originated from the observation that patients who were active recovered faster, was based on the supposition that the head movements that provoke the patient's dizziness play an important role in hastening the recovery process. Here the author reviews the clinical manifestation and treatment of bilateral vestibular deficit that include vestibular rehabilitation therapy and vestibular device that studied today.
Dizziness ; Exercise ; Head Movements ; Humans ; Reflex ; Rehabilitation ; Vertigo ; Vestibular Diseases