A simple approach to calculate active power of electrosurgical units

Abstract Introduction: Despite of more than a hundred years of electrosurgery, only a few electrosurgical equipment manufacturers have developed methods to regulate the active power delivered to the patient, usually around an arbitrary setpoint. In fact, no manufacturer has a method to measure the active power actually delivered to the load. Measuring the delivered power and computing it fast enough so as to avoid injury to the organic tissue is challenging. If voltage and current signals can be sampled in time and discretized in the frequency domain, a simple and very fast multiplication process can be used to determine the active power. Methods This paper presents an approach for measuring active power at the output power stage of electrosurgical units with mathematical shortcuts based on a simple multiplication procedure of discretized variables – frequency domain vectors – obtained through Discrete Fourier Transform (DFT) applied on time-sampled voltage and current vectors. Results Comparative results between simulations and a practical experiment are presented – all being in accordance with the requirements of the applicable industry standards. Conclusion An analysis is presented comparing the active power analytically obtained through well-known voltage and current signals against a computational methodology based on vector manipulation using DFT only for time-to-frequency domain transformation. The greatest advantage of this method is to determine the active power of noisy and phased out signals with neither complex DFT or ordinary transform methodologies nor sophisticated computing techniques such as convolution. All results presented errors substantially lower than the thresholds defined by the applicable standards.

Repeatability of corneal power measurements by Galilei Ⅱ dual Scheimpflug analyzer in post-LASIK eyes / 中华实验眼科杂志

Background The assessment of total corneal power is essential to both the prediction of intraocular lens power before cataract surgery and the diagnosis of corneal ectasia.Objective This study was to access the repeatability of corneal power measurements in post-laser assisted in-situ keratomileusis (LASIK) eyes with GalileiⅡ dual Scheimpflug analyzer.Methods In this cross-sectional study,68 eyes of 36 subjects who received LASIK surgery more than 3 months in Eye Hospital of Wenzhou Medical University were recruited from July to September in 2011.The mean preoperative spherical equivalent diopter was (-4.95±2.08) D in the subjects with the diopter range from-1.75 D to-10.00 D.The parameters of corneal power were measured by Galilei Ⅱ dual Scheimpflug analyzer,including SimK,Ka,Kp,KG and Kray.Three-time consecutive measurements were completed in every examined eye to obtain the data of SimK,Ka,Kp,KG and Kray,respectively.The coefficient of variation (CV),standard deviation (SD),Cronbach α coefficient and intra-class correlation coefficient (ICC) were calculated to evaluate the repeatability.Concordance between the different measurements was assessed using Bland-Altman agreement analysis.This study followed the Helsinki Declaration,all subjects signed informed consent.Results The CVs of three-time measured SimK,Ka,Kp,KG and Kray were 0.24％,0.28％,-0.37％,0.31％ and 0.32％,respectively,and the Cronbach α values were ＞0.9 and the ICCs were ＞0.982.The Bland-Altman analysis between different measurements showed that the maximum 95％ limits of agreement (LoA) were 0.37 D for SimK,0.46 D for Ka,0.09 D for Kp,0.45 D for KG and 0.49 D for Kray,respectively.Conclusions The Galilei Ⅱ dual Scheimpflug analyzer performed high repeatability and concordance on corneal power measurements in post-LASIK eyes.The differences between measuring results are clinically acceptable.

Evaluation of ocular refraction in silicone oil temponade eyes by the IOL-Master system / 眼科研究

Background The combination procedure of the removal of silicon oil and cataract extraction+intraocular lens (IOL) implantation is the main method of treating cataract in silicone oil tamponade eye.However,the conventional measuring method of the IOL power is limiting in eyes with silicone oil tamponade.The IOL-Master system is confirmed to be an ideal non-contact optical measuring instrument in vivo.Objective The aim of this study is to measure the preoperative IOL power,evaluate the accuracy of biometry with the IOL-Master system and compare the relationship between different factors and refractive error.Methods IOL power was measured in 29 silicone oil tamponade eyes of 29 patients prior to the silicone oil removal combining IOL implantation with the IOL-Master system according to different factors such as placement time,axis oculi,complications and so on.The reasons of visual acuity recovery and measurement error were discussed.Results Postoperative visual acuity was improved in all of the patients.The average predictive refractive error was 0.329±0.846 (-1.5--2D).Classified factors for the cause of disease for axis oculi included rhegmatogenous retinal detachment (RRD)(t=0.478,P=0.637),macular hole(t=0.135,P=0.895),myopia(t=0.435,P=0.667)and oil-placed time (good for less than 1 year).These factors showed an indirect relationship with errors.Conclusion Silicone oil removal combined with IOL implantation can improve visual acuity.The IOL-Master biometry is accurate,safe and convenient in measuring the IOL power in silicon oil temponade eye,but future research should be performed to decrease the measuring error.

Relationship between Clinical History Method and Orbscan II for Measuring Corneal Power after LASIK

PURPOSE: To evaluate the relation between clinical history method and Orbscan II for corneal power measurement after laser in situ keratomileusis (LASIK). METHODS: A total of 77 consecutive eyes of 43 patients who were treated with LASIK for myopia were followed up for at least 6 months. Corneal power by clinical history methods (CK) was compared with 3.0 mm zones of simulated keratometry (Sim-K), with 0.5, 1.0, 1.5, 2.0 and 3.0 mm zones of axial power maps (AP) and with 2.0, 3.0, 3.5, 4.0 and 5.0 mm zones of total optical power maps (TOP). RESULTS: Sim-K and all AP-map zones using Orbscan II were significantly higher (P<.001) than the CK value, while all TOP-map zones were significantly lower (P<.001) than the CK value. Among them, 3.0 and 4.0 mm TOP-map zones showed the highest correlation with the corneal power by CK (r2=0.889, P<.001; r2=0.889, P<.001). The correlation was higher with 3.0 mm TOP-map zone (r2=0.800, P<.001) than with 4.0 mm TOP-map zone (r2=0.793, P<.001) in high myopia patients. CONCLUSIONS: Although 3.0 and 4.0 mm TOP-map zones of Orbscan II were correlated highly with the CK value, these correlations were relatively low in high myopia patients and 3.0 mm TOP-map zone was better correlated than 4.0 mm TOP-map zone in these patients.

Comparison of Global Field Power Measurement and Conventional Method in Multi-channel Auditory Event Related Potential P300 Determination

OBJECTIVE: The present study was designed to compare Global field Power Measurement and conventional method in P300 determination. METHOD: The subjects were composed of patients(N=20) with schizophrenia by DSM-IV and normal controls(N=20). The auditory event related potential P300 was measured by "oddball paradigm". P300 components were determined by Global Field Power Measurement and conventional method at 5 electrodes(Fz, Cz, Pz, T3, T4). RESULTS: P300 amplitudes of patients were smaller than those of controls across all electrodes and in both methods, but there was no differential power in P300 determination between two methods. Asymmetry of auditory event-related potential P300 was not shown between patients with schizophrenia and normal controls. CONCLUSION: It is implicated that it depends on clinical situations and research purposes what method of P300 determination will be more appropriate for patients with schizophernia.

How to Determine P300 Component in Auditory Event Related Potential Brain Topography / 신경정신의학

OBJECTS: This study was designed to make a comparison between methods to determine the components of topographic auditory event related potential P300. METHODS: The subjects were consisted of 44 normal controls and 44 patients with schizophrenia diagnosed by DSM-IV. The topographic auditory event related P300 was recorded in oddball paradigm. The components of P300, including latency, amplitude, and location of maximum amplitude in X-Y coordinates, were analized by computerized EP mapping system. The latency of P300 was determined by both global field power measurement and classic method. RESULTS: There was difference between two groups in latency(DF=1, F=35.28, P= 0.0001) and amplitude(DF=1, F=36.62, P=0.0001), but not in X coordinate(DF=1, F=0.37, P=0.55) and Y coordinate(DF=1, F=2.00, P=0.16). There was no difference between two mothods in latency(DF=1, F=0.04, P=0.85), in amplitude(DF=1, F=0.07, P=0.79), in X coordinate(DF=1, F=0.07, P=0.79), and in Y coordinate(DF=1, F=0.03, P=0.86). CONCLUSION: The results suggested that two methods to determine the components of topographic auditory event related potential P300 should be available for both research and clinical application to date.

Effects of Cigarette Smoking on Auditory Event-Related Potential P300 / 신경정신의학

OBJECTIVES: The authors studied the effects of cigarette smoking on the cognitive function with topographic mapping of auditory event-related potential P300. METHODS: The subjects, 24 smokers and 14 nonsmokers, were assessed in the latencies and amplitudes of topographic auditory event-related potential P300 determined by Global Field Power Measurement. RESULTS: 1) There were significant differences of P300 latencies between smokers and controls artier smoking(ANOVAL F=10.45, P=0.0026). 2) There were no significant differences of P300 amplitude but a trend was present between smokers and nonsmokers after smoking(ANOVAL F=3.77, P=0.06). 3) There were no significant differences of difference between amplitude in maximal point and amplitude in minimal point but a trend was present between smokers and nonsmokers artier smoking(ANOVAL F=3.68, P=0.063). 4) There were no significant differences of maximal point in X-axis and in Y-axis, minimal point in X-axis and in Y-axis of P300 between smokers and nonsmokers artier smoking. CONCLUSIONS: These results support that auditory event-related potential P300 change by cigarrete smoking is indicative of enhanced cognitive function.