No abstract available.
Electrodes*

No abstract available.
Electrodes*

PURPOSE: To explore the effects of stimulus duration, stimulus intensity, and background luminance on the amplitude and waveform of the ON- and OFF- responses of photopic ERG and to provide standard parameters of ON- and OFF- responses for normal Korean populations. METHODS: Twenty normal subjects (20 eyes) were enrolled to record photopic ON-and OFF-responses using a contact lens electrode with built-in LEDs and an LED-driver. The influence of stimulus duration on wave amplitudes was studied at flash durations that varied from 5 to 200 ms. The influence of stimulus intensity was studied with 0.4, 0.7, 1.1, 1.4, 1.7, 1.9, 2.0, and 2.1 log cd/m2. In addition, the influence of background luminance was studied with 20, 30, 40, and 50 cd/m2. RESULTS: Among 20 normal subjects, the d-waves in 16 subjects were isolated from b-waves with more than 50 ms of stimulus duration. The d-wave was observed for a 30-ms stimulus duration in 3 subjects and for a 100-ms duration in 1 subject. The amplitudes of the b-and d-waves increased as stimulus intensity was increased. The amplitudes of b-and d-waves decreased as background luminance was increased. CONCLUSIONS: Our results suggest that the clinical use of ON-and OFF-response recording can be obtained with stimulus parameters from 100 to 150 ms in duration and a 1.7-2.1 log cd/m2 intensity under 30-40 cd/m2 background luminance.
Electrodes ; Electroretinography

PURPOSE: To compare electroretinogram (ERG) waveforms acquired using an ERG-jet electrode and a Burian-Allen electrode. METHODS: ERGs were recorded with an ERG-jet electrode and a Burian-Allen electrode from both eyes of 29 volunteers. Three consecutive recordings were obtained with both electrodes from the left eye of another 6 volunteers. Peak-to-trough amplitudes and peak implicit times were compared between both eyes, and between the 2 types of electrodes. Interpersonal and intrapersonal variation were also compared. RESULTS: The differences in amplitude and implicit time between the right and left eyes were not influenced by the type of electrode. The amplitude of the ERG acquired using the Burian-Allen electrode, however, showed significant differences between both eyes, contrary to the amplitude acquired using the ERG-jet electrode. ERG recordings obtained using the ERG-jet electrode generally showed higher amplitude, shorter implicit time, and less interpersonal and intrapersonal variation than ERG recordings obtained using the Burian-Allen electrode. CONCLUSIONS: In this application, the ERG-jet ERG electrode appeared to be superior to the Burian-Allen electrode in terms of both usefulness and consistency.
Electrodes ; Eye

The quality factors (kQ,Q0) were evaluated by appling the results recently studied for the effect of central electrode in TRS-398 protocol. The PTW-31010 and IBA-CC13 chambers were used in this study. The quality factors were calculated as a function of beam quality for high energy electron and photon beams and compared with data currently used in TRS-398 protocol. In the PTW-31010 chamber using aluminium electrode, appling the new central electrode collections, the quality factors were 0.4% and 0.9% higher than current TRS-398 data for high energy photon and electron beams respectively. In the IBA-CC13 chamber using C-552 electrode, there are no variations in quality factors compared to TRS-398 data currently used.
Electrodes ; Electrons

We have designed the multi channel detector for the quality assurance of clinical photon beams. The detector was composed of solid phantom inserted by six plane-parallel ionization chambers at different depth. The chamber as a mini plane parallel chamber was made of carbon coated microfilms. In this study the electrical characteristics of the six chambers in the solid phantom were evaluated using 6 MV photon beam. The leakage currents were less than 0.5 pA, reproducibility was less than 0.5%, linearity was less than 0.5%, and dose rate effect was less than 0.7%. In addition the effect of dose variation from other chambers was estimated to maximum 0.8% approximately. The developed detector can be used for quality determination in output dosimetry or measurement of percentage depth dose approximately for clinical photon beam.
Carbon* ; Electrodes*

No abstract available.
Electrodes* ; Seizures*

PURPOSE: The purpose of this study was to determine the factors influencing on the size of thermal lesions after ablation using an expandable radio-frequency needle electrode in porcine liver. MATERIALS AND METHODS: Ablation procedures involved the use of a monopolar radio-frequency generator and 15-G needle electrodes with four and seven retractable hooks (RITA Medical System, Mountain View, Cal.,U.S.A.). The ablation protocol in fresh porcine liver comprised of combinations of varying hook deployment, highest set temperature, and ablation time. Following ablation, the maximum diameter of all thermal lesions was measured on a longitudinal section of the specimen. Ten representive lesions were examined by an experienced pathologist. RESULTS: At 3-cm hook deployment of the needle electrode with four lateral hooks, the size of spherical thermal lesions increased substantially with increases in the highest set temperature and ablation time until 11 minutes. After 11 minutes lesion size remained similar, with a maximum diameter of 3.3 cm. At 2-cm hook deployment, sizes decreased to about 2/3 of those at 3 cm, and at 1-cm hook deployment lesions were oblong. At 3-cm hook deployment of a needle electrode with seven hooks, the size of thermal lesions increased with increasing ablation time until 14 minutes, and the maximum diameter was 4.1 cm. Microscopic examination showed a wide zone of degeneration and focal coagulation necrosis. CONCLUSION: The size of thermal lesions produced by the use of an expandable radio-frequency needle electrode were predictable, varying according to degree of hook deployment, highest set temperature, and ablation time.
Electrodes* ; Liver ; Necrosis ; Needles*

OBJECTIVES: The aim of this study was to observe the nystagmus of totally unilateral vestibular function loss on galvanic vestibular stimulation and the diagnostic value of galvanic vestibular stimulation. Additionally we wanted to evaluate which portions may be stimulated by galvanic vestibular stimulation. MATERIALS AND METHODS: We evaluated the three parameters of galvanic stimulation in fourteen patients with totally unilateral vestibular function loss, 1)spontaneous nystagmus, 2)galvanic stimulating nystagmus, 3)Post galvanic stimulating nystagmus through 3-dimensional video-oculography technique. RESULTS: When negative electrode was attached to the intact side, The nystagmus on galvanic vestibular stimulation was directed to the negative electrode side in all patients and post galvanic stimulating nystagmus was directed to the opposite side but on functional loss side, we couldn't detect any nystagmus on galvanic vestibular stimulation and in 10 patients, post galvanic stimulating nystagmus was observed and directed to the intact side. CONCLUSIONS: Galvanic vestibular stimulation is very useful for evaluating the vestibular function and for diagnosing the vestibular disease.
Electrodes ; Humans ; Vestibular Diseases

No abstract available.
Chronic Pain* ; Electrodes*