Ring electrode for radio-frequency heating of the cornea: modelling and in vitro experiments

[EN] Radio-frequency thermokeratoplasty (RF-TKP) is a technique used to reshape the cornea curvature by means of thermal lesions using radio-frequency currents. This curvature change allows refractive disorders such as hyperopia to be corrected. A new electrode with ring geometry is proposed for RF-TKP. It was designed to create a single thermal lesion with a full-circle shape. Finite element models were developed, and the temperature distributions in the cornea were analysed for different ring electrode characteristics. The computer results indicated that the maximum temperature in the cornea was located in the vicinity of the ring electrode outer perimeter, and that the lesions had a semi-torus shape. The results also indicated that the electrode thickness, electrode radius and electrode thermal conductivity had a significant influence on the temperature distributions. In addition, in vitro experiments were performed on rabbit eyes. At 5 IN power the lesions were fully circular. Some lesions showed non-uniform characteristics along their circular path. Lesion depth depended on heating duration (60% of corneal thickness for 20s, and 30% for 10s). The results suggest that the critical shrinkage temperature (55-63degreesC) was reached at the central stroma and along the entire circular path in all the cases.Berjano, E.; Saiz Rodríguez, FJ.; Alió, J.; Ferrero, JM. (2003). Ring electrode for radio-frequency heating of the cornea: modelling and in vitro experiments. Medical & Biological Engineering & Computing. 41(6):630-639. https://doi.org/10.1007/BF02349970S630639416Alió, J. L., Ismail, M. M., Artola, A., andPérez-Santonja, J. J. (1997a): ‘Correction of hyperopia induced by photorefractive keratectomy using non-contact Ho: YAG laser thermal keratoplasty’,J. Refract. Surg.,13, pp. 13–16Alió, J. L., Ismail, M. M., andSanchez, J. L. (1997b): ‘Correction of hyperopia with non-contact Ho: YAG laser thermal keratoplasty’,J. Refract. Surg.,13, pp. 17–22Alió, J. L., andPérez-Santonja, J. J. (1999): ‘Correction of hyperopia by laser thermokeratoplasty (LTK)’ inPallikaris, I., andAgarwal, S. (Eds): ‘Refractive Surgery’ (Jaypee Brothers Medical Publishers Ltd, New Delhi, 1999), pp. 583–591Alió, J. L., andPérez-Santonja, J. J. (2002): ‘Correction of hyperopia by laser thermokeratoplasty (LTK)’ inAgarwal, S., Agarwal, A., Apple, D. J., Buratto, L., Alió, J. L., Pandey, S. K., andAgarwal, A. (Eds): ‘Textbook of ophthalmology’ (Lippincott Williams & Wilkins, Philadelphia, 2002), pp. 1331–1337Ayala, M. J., Alió, J. L., Ismail, M. M., andSánchez-Castro, J. M. (2000): ‘Experimental corneal histological study after thermokeratoplasty with holmium laser’,Arch. Soc. Esp. Oftalmol.,75, pp. 619–626Asbell, P. A., Maloney, R. K., Davidorf, J., Hersh, P., McDonald, M., Manche, E., andConductive Keratoplasty Study Group (2001): ‘Conductive keratoplasty for the correction of hyperopia’,Tr. Am. Ophtalmol. Soc.,99, pp. 79–87Avitall, B., Mughal, K., Hare, J., Helms, R., andKrum, D. (1997): ‘The effects of electrode-tissue contact on radiofrequency lesion generation’PACE,20, pp. 2899–2910Avitall, B., Helms, R. W., Koblish, J. B., Sieben, W., Kotov, A. V., andGupta, G. N. (1999): ‘The creation of linear contiguous lesions in the atria with an expandable loop catheter’,J. Am. Coll. Cardiol.,33, pp. 972–984Berjano, E. J., Saiz, J., andFerrero, J. M. (2002): ‘Radio-frequency heating of the cornea: Theoretical model andin vitro experiments’,IEEE Trans. Biomed. Eng.,49, pp. 196–205Brickmann, R., Kampmeier, J., Grotehusmann, U., Vogel, A., Koop, N., Asiyo-Vogel, M., Kamm, K., andBirngruber, R. (1996): ‘Corneal collagen denaturation in laserthermokeratoplasty’,SPIE Proc.,2681, pp. 56–63Choi, B., Kim, J., Welch, A. J., andPearce, J. A. (2002): ‘Dynamic impedance measurements during radio-frequency heating of cornea’,IEEE Trans. Biomed. Eng.,49, pp. 1610–1616Curley, M. G., andHamilton, P. S. (1997): ‘Creation of large thermal lesions in liver using saline-enhanced RF ablation’. Proc. 19th Ann. Int. Conf. IEEE Eng. Med. Biol. Soc., Chicago, pp. 2516–2519Doss, J. D., andAlbillar, J. I. (1980): ‘A technique for the selective heating of corneal stroma’,Contact Intraocular Lens Med.,6, pp. 13–17Doss, J. D. (1982): ‘Calculation of electric fields in conductive media’,Med. Phys.,9(4), pp. 566–573Gruenberg, P., Manning, W., Miller, D. andOlson, W. (1981): ‘Increase in rabbit corneal curvature by heated ring application’,Ann. Ophthalmol.,13, pp. 67–70Hata, C., andRaymond Chia, W.-K. (2001): ‘Catheter for circular tissue ablation and methods thereof’. US Patent 2001/0044625 A1Jain, M. K., andWolf, P. D. (1998): ‘Effect of electrode contact on lesion growth during temperature controlled radiofrequency ablation’, Proc. 20th Ann. Int. Conf. IEEE Eng. Med. Biol. Soc. Hong Kong (IEEE, Piscataway NJ) pp. 245–247Jain, M. K., andWolf, P. D. (1999): ‘Temperature controlled and constant power radiofrequency ablation: what affects lesion growth?’,IEEE Trans. Biomed. Eng.,46, pp. 1405–1412Krasteva, V. Tz., andPapazov, S. P. (2002): ‘Estimation of current density distribution under electrodes for external defibrillation’,Biomed. Eng. OnLine,1, 7Labonté, S. (1992): ‘A theoretical study of radio-frequency ablation of the myocardium’,PhD dissertation, Department of Electrical Engineering, University of Ottawa, CanadaLabonté, S. (1994): ‘Numerical model for radio-frequency ablation of the endocardium and its experimental validation’,IEEE Trans. Biomed. Eng.,41, pp. 108–115Mannis, M. J., Segal, W. A., andDarlington, J. K. (2001): ‘Making sense of refractive surgery in 2001: Why, when, for whom, and by whom?’,Mayo Clin. Proc.,76, pp. 823–829McCally, R. L., Bargeron, R. A., andGreen, W. R. (1983): ‘Stromal damage in rabbit corneas exposed to CO2 laser radiation’,Exp. Eye Res.,37, pp. 543–550McDonald, M. B., Hersh, P. S., Manche, E. E., Maloney, R. K., Davidorf, J., andSabry, M. (2002): ‘Conductive keratoplasty for the correction of low to moderate hyperopia: U.S. clinical trial 1-year results on 355 eyes’,Ophthalmol.,109, pp. 1978–1989McRury, I. D., Mitchell, M. A., Panescu, D. andHaines, D. E. (1997): ‘Non-uniform heating during radiofrequency ablation with long electrodes: monitoring the edge effect’,Circ.,96, pp. 4057–4064Méndez-g, A., andMéndez-Noble, A. (1997): ‘Conductive keratoplasty of the correction of hyperopia’ inSher, N. A. (Ed.) ‘Surgery for hyperopia and presbyopia’ (Williams & Wilkins, Baltimore, 1997), pp. 163–171Miller, D., andManning, W.J. (1978): ‘Alterations in curvature of bovine cornea using heated rings’,Invest. Ophthalmol., p. 297Mirotznik, M. S., andSchwartzman, D. (1996): ‘Nonuniform heating patterns of commercial electrodes for radiofrequency catheter ablation’,J. Cardiovasc. Electrophysiol.,7, pp. 1058–1062Nakagawa, H., Yamanashi, W. S., Pitha, J. V., Arruda, M., Wang, X., Ohtomo, K., Beckman, K. J., McClelland, J. H., Lazzara, R., andJackman, W. M. (1995): ‘Comparison ofin vivo tissue temperature profile and lesion geometry for radiofrequency ablation with a saline-irrigated electrode versus temperature control in a canine thigh muscle preparation’,Circ.,91, pp. 2264–2273Panescu, D., Whayne, J. G., Fleischman, S. D., Mirotznik, M. S., Swanson, D. K., andWebster, J. G. (1995): ‘Three-dimensional finite element analysis of current density and temperature distributions during radio-frequency ablation’,IEEE Trans. Biomed. Eng.,42, pp. 879–890Plonsey, R., andHeppner, D. B. (1967): ‘Considerations of quasistationarity in electrophysiological systems’,Bull. Math. Biophys.,29, pp. 657–664Rowsey, J. J. (1987): ‘Electrosurgical keratoplasty: Update and retraction’,Invest. Ophthalmol. Vis. Sci.,28, p. 224Rutzen, A. R., Roberts, C. W., Driller, J., Gomez, D., Lucas, B. C., Lizzi, F. L., andColeman, D. J. (1990): ‘Production of corneal lesions using high-intensity focused ultrasound’,Cornea,9, pp. 324–330Schwan, H. P., andFoster, K. R. (1980): ‘RF-fields interactions with biological systems: electrical properties and biophysical mechanism’,Proc. IEEE,68, pp. 104–113Seiler, T., Matallana, M., andBende, T. (1990): ‘Laser thermokeratoplasty by means of a pulsed Holmium:YAG Laser for the hyperopic correction’,Refrac. Corneal Surg.,6, pp. 335–339Silvestrini, T. A. (1998): ‘Electrosurgical procedure for the treatment of the cornea’. US Patent 5,766,171Simmons, W. N., Mackey, S., He, D. S. andMarcus, F. L. (1996): ‘Comparison of gold versus platinum electrodes on myocardial lesion size using radiofrequency energy’,PACE,19, pp. 398–402Stringer, H., andParr, J. (1964): ‘Shrinkage temperature of eye collagen’,Nature,204, p. 1307Trembly, B. S., andKeates, R. H. (1991): ‘Combined microwave heating and surface cooling of the cornea’,IEEE Trans. Biomed. Eng.,38, pp. 85–91Trembly, B. S., Hashizume, N., Moodie, K. L., Cohen, K. L., Tripoli, N. K., andHoopes, P. J. (2001): ‘Microwave thermal keratoplasty for myopia: keratoscopic evaluation in porcine eyes’,J. Refract. Surg.,17, pp. 682–688Tungjitkusolmun, S., Woo, E. J., Cao, H., Tsai, J. Z., Vorperian, V. R., andWebster, J. G. (2000): ‘Thermal-electrical finite element modelling for radio frequency cardiac ablation: effects of changes in myocardial properties’,Med. Biol. Eng. Comput.,38, pp. 562–568Wiley, J. D., andWebster, J. G. (1982): ‘Analysis and control of the current distribution under circular dispersive electrodes’,IEEE Trans. Biomed. Eng,29, pp. 381–38

Psychological and social effects of orthodontic treatment

Adolescents with commonly occurring forms of malocclusion often are presumed to be at risk for negative self-esteem and social maladjustment. A randomized control group design was used to assess the psychosocial effects of orthodontic treatment for esthetic impairment. Ninety-three participants, 11 to 14 years old, with mild to moderate malocclusions, were randomly assigned to receive orthodontic treatment immediately or after serving as delayed controls. A battery of psychological and social measures was administered before treatment, during treatment, and three times after completion of treatment, the last occurring one year after termination. Repeated measures analyses of variance assessed group differences at the five time points. Parent-, peer-, and self-evaluations of dental-facial attractiveness significantly improved after treatment, but treatment did not affect parent- and self-reported social competency or social goals, nor subjects' self-esteem. In summary, dental-specific evaluations appear to be influenced by treatment, while more general psychosocial responses are not.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44814/1/10865_2005_Article_BF01856884.pd

A Review of Ex-Post Evidence for Mode Substitution and Induced Demand Following the Introduction of High-Speed Rail

To date, relatively little is known about the nature of the demand for high-speed rail (HSR) soon after inauguration of the services, despite close to 50-year experience of HSR operation and 17 166 km of HSR network around the world. This is a real lacuna given the scale of HSR construction around the world, the amount of resources committed to it, the desired accessibility, economic and environmental effects associated with HSR development and the relatively poor track record of forecasting demand for HSR services. Focusing on mode substitution and induced demand effects, this review aims to fill the gap in knowledge about the ex-post demand for HSR services in order to facilitate a learning process for the planning of the future HSR network. Although there is not much evidence on the demand for HSR services and existing evidence is largely influenced by route-specific characteristics, a methodological limitation that must be acknowledged, the evidence presented allows a better characterisation of HSR as a mode of transport. The review shows that the demand for HSR a few years after inauguration is about 10–20% induced demand and the rest is attributed to mode substitution. In terms of mode substitution, in most cases the majority of HSR passengers have used the conventional rail before. Substitution from aircraft, car and coach is generally more modest.info:eu-repo/semantics/publishe