The Experts below are selected from a list of 198 Experts worldwide ranked by ideXlab platform
Jan Hrbacek - One of the best experts on this subject based on the ideXlab platform.
-
Technical Note: Benchmarking automated eye tracking and human detection for motion monitoring in ocular proton therapy.
Medical physics, 2020Co-Authors: Riccardo Via, Fabian Hennings, Giovanni Fattori, Alessia Pica, Antony J. Lomax, Damien C. Weber, Guido Baroni, Jan HrbacekAbstract:Purpose Ocular proton therapy is an effective therapeutic option for patients affected with uveal melanomas. An optical eye-tracking system (ETS) aiming at noninvasive motion monitoring was developed and tested in a clinical scenario. Materials and methods The ETS estimates eye position and orientation at 25 frames per second using the three-dimensional position of pupil and Cornea Curvature centers identified, in the treatment room, through stereoscopic optical imaging and infrared eye illumination. Its capabilities for automatic detection of eye motion were retrospectively evaluated on 60 treatment fractions. Then, the ETS performance was benchmarked against the clinical standard based on visual control and manual beam interruption. Results Eye-tracking system detected eye position successfully in 97% of all available frames. Eye-tracking system-based eye monitoring during therapy guarantees quicker response to involuntary eye motions than manual beam interruptions and avoids unnecessary beam interruptions. Conclusions Eye-tracking system shows promise for on-line monitoring of eye motion. Its introduction in the clinical workflow will guarantee a swifter treatment course for the patient and the clinical personnel.
-
Noninvasive eye localization in ocular proton therapy through optical eye tracking: A proof of concept.
Medical physics, 2018Co-Authors: Riccardo Via, Fabian Hennings, Giovanni Fattori, Alessia Pica, Antony J. Lomax, Damien C. Weber, Guido Baroni, Aurora Fassi, Jan HrbacekAbstract:PURPOSE Over the last four decades, Ocular Proton Therapy has been successfully used to treat patients affected by intraocular lesions. For this, treatment geometry verification is routinely performed using radiographic images to align a configuration of fiducial radiopaque markers implanted on the sclera outer surface. This paper describes the clinical application of an alternative approach based on optical eye tracking for three-dimensional non-invasive and automatic eye localization. An experimental protocol was designed to validate the optical-based eye referencing against both radiographic imaging system and the clinically used EYEPLAN treatment planning system. METHODS The eye tracking system (ETS) was installed in the OPTIS 2 treatment room at PSI to acquire eye motions during the treatment of nine patients. The pupil position and the Cornea Curvature centre were localized by segmenting the pupil contour and Corneal light reflections on the images acquired by a pair of calibrated optical cameras. After calibration of the ETS, a direct comparison of radiopaque markers position, and consequentially eye position and orientation, provided by the ETS, radiographs and EYEPLAN was performed. RESULTS Nineteen out of thirty total monitored fractions were excluded from the study due to poor visibility of Corneal reflection, resulting in a success rate of acquisition of 37%. For this data, overall median agreement between ETS-based and X-ray based markers position assessment were 0.29 mm and 0.94 degrees for translations and rotations respectively. Small discrepancies were also measured in the eye centre estimates of the ETS and EYEPLAN. Conversely, variations in measured eye orientation were higher, with inter-quartile range (IQR) between 4.39° and 7.58°. Nonetheless, dosimetric evaluation of the consequence of ETS uncertainties showed that the target volume would still be covered by more than 95% of the dose in all cases. CONCLUSION An ETS was successfully installed in a clinical ocular proton therapy treatment room and used to monitor eye position and orientation in a clinical scenario. First results show the potential of such a system as an eye localization device. However, the low success rate prevents straightforward clinical application and needs further improvements aimed at increasing Corneal reflection visibility. This article is protected by copyright. All rights reserved.
J. M. Ferrero - One of the best experts on this subject based on the ideXlab platform.
-
Ring electrode for radio-frequency heating of the Cornea: Modelling andin vitro experiments
Medical and Biological Engineering and Computing, 2003Co-Authors: E. J. Berjano, J. Saiz, J. L. Alió, J. M. FerreroAbstract: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 W 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 (55–63°C) was reached at the central stroma and along the entire circular path in all the cases.
-
Ring electrode for radio-frequency heating of the Cornea: modelling and in vitro experiments.
Medical & biological engineering & computing, 2003Co-Authors: Enrique Berjano, J. Saiz, J. L. Alió, J. M. FerreroAbstract: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 W 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 (55–63°C) was reached at the central stroma and along the entire circular path in all the cases.
-
Radio-frequency heating of the Cornea: theoretical model and in vitro experiments
IEEE transactions on bio-medical engineering, 2002Co-Authors: Enrique Berjano, J. Saiz, J. M. FerreroAbstract:We present a theoretical model for the study of Cornea heating with radio-frequency currents. This technique is used to reshape the Cornea to correct refractive disorders. Our numerical model has allowed the study of the temperature distributions in the Cornea and to estimate the dimensions of the lesion. The model incorporates a fragment of Cornea, aqueous humor, and the active electrode placed on the Cornea surface. The finite element method has been used to calculate the temperature distribution in the Cornea by solving a coupled electric-thermal problem. We analyzed by means of computer simulations the effect of: a) temperature influence on the tissue electrical conductivity; b) the dispersion of the biological characteristics; c) the anisotropy of the Cornea thermal conductivity; d) the presence of the tear film; and e) the insertion depth of the active electrode in the Cornea, and the results suggest that these effects have a significant influence on the temperature distributions and thereby on the lesion dimensions. However, the cooling of the aqueous humor in the endothelium or the realistic value of the Cornea Curvature did not have a significant effect on the temperature distributions. An experimental model based on the lesions created in rabbit eyes has been used in order to compare the theoretical and experimental results. There is a tendency toward the agreement between experimental and theoretical results, although we have observed that the theoretical model overestimates the lesion dimension.
Fu Meng-ju - One of the best experts on this subject based on the ideXlab platform.
-
Actorial analysis research of the changes of posterior Cornea Curvature after laser in situ keratomileusis of patients with High myopia
Clinical Ophthalmology, 2012Co-Authors: Chen Yuan-bin, Fu Meng-juAbstract:Objective Observe the changes of posterior Cornea Curvature after laser in situ keratomileusis(LASIK).Study the relationship of posterior Cornea Curvature change with preoperative intraocular pressure and load factor(Preoperative Corneal thickness/Residual bed thickness).Methods Forty patients(80 eyes) were treated by LASIK.Curve of Corneal posterior surface was measured with Orbscan II topography system before and 1 month,2 month,3 month,6 month after surgery.The results of measurement in different time points were compared.Patients were divided into four groups according to the preoperative intraocular pressure and load factor.Study the relationship of posterior Cornea Curvature change with preoperative intraocular pressure and load factor.Results The posterior Corneal surface showed a mean forward shift after LASIK of patients with high myopia.1 month after LASIK surgery,radius of posterior Cornea Curvature were changed 0.135 μm ±0.098 μm,2 month after LASIK surgery,radius of posterior Cornea Curvature were changed 0.022 μm±0.034μ m.Cconclusion The posterior Corneal surface showed a mean forward shift after LASIK with high myopia,2 months after LASIK surgery Corneal surface Curvature basically stable.The higher the preoperative intraocular pressure,the bigger the load factor,the more obvious the forward shift of the Cornea.
Riccardo Via - One of the best experts on this subject based on the ideXlab platform.
-
Technical Note: Benchmarking automated eye tracking and human detection for motion monitoring in ocular proton therapy.
Medical physics, 2020Co-Authors: Riccardo Via, Fabian Hennings, Giovanni Fattori, Alessia Pica, Antony J. Lomax, Damien C. Weber, Guido Baroni, Jan HrbacekAbstract:Purpose Ocular proton therapy is an effective therapeutic option for patients affected with uveal melanomas. An optical eye-tracking system (ETS) aiming at noninvasive motion monitoring was developed and tested in a clinical scenario. Materials and methods The ETS estimates eye position and orientation at 25 frames per second using the three-dimensional position of pupil and Cornea Curvature centers identified, in the treatment room, through stereoscopic optical imaging and infrared eye illumination. Its capabilities for automatic detection of eye motion were retrospectively evaluated on 60 treatment fractions. Then, the ETS performance was benchmarked against the clinical standard based on visual control and manual beam interruption. Results Eye-tracking system detected eye position successfully in 97% of all available frames. Eye-tracking system-based eye monitoring during therapy guarantees quicker response to involuntary eye motions than manual beam interruptions and avoids unnecessary beam interruptions. Conclusions Eye-tracking system shows promise for on-line monitoring of eye motion. Its introduction in the clinical workflow will guarantee a swifter treatment course for the patient and the clinical personnel.
-
Noninvasive eye localization in ocular proton therapy through optical eye tracking: A proof of concept.
Medical physics, 2018Co-Authors: Riccardo Via, Fabian Hennings, Giovanni Fattori, Alessia Pica, Antony J. Lomax, Damien C. Weber, Guido Baroni, Aurora Fassi, Jan HrbacekAbstract:PURPOSE Over the last four decades, Ocular Proton Therapy has been successfully used to treat patients affected by intraocular lesions. For this, treatment geometry verification is routinely performed using radiographic images to align a configuration of fiducial radiopaque markers implanted on the sclera outer surface. This paper describes the clinical application of an alternative approach based on optical eye tracking for three-dimensional non-invasive and automatic eye localization. An experimental protocol was designed to validate the optical-based eye referencing against both radiographic imaging system and the clinically used EYEPLAN treatment planning system. METHODS The eye tracking system (ETS) was installed in the OPTIS 2 treatment room at PSI to acquire eye motions during the treatment of nine patients. The pupil position and the Cornea Curvature centre were localized by segmenting the pupil contour and Corneal light reflections on the images acquired by a pair of calibrated optical cameras. After calibration of the ETS, a direct comparison of radiopaque markers position, and consequentially eye position and orientation, provided by the ETS, radiographs and EYEPLAN was performed. RESULTS Nineteen out of thirty total monitored fractions were excluded from the study due to poor visibility of Corneal reflection, resulting in a success rate of acquisition of 37%. For this data, overall median agreement between ETS-based and X-ray based markers position assessment were 0.29 mm and 0.94 degrees for translations and rotations respectively. Small discrepancies were also measured in the eye centre estimates of the ETS and EYEPLAN. Conversely, variations in measured eye orientation were higher, with inter-quartile range (IQR) between 4.39° and 7.58°. Nonetheless, dosimetric evaluation of the consequence of ETS uncertainties showed that the target volume would still be covered by more than 95% of the dose in all cases. CONCLUSION An ETS was successfully installed in a clinical ocular proton therapy treatment room and used to monitor eye position and orientation in a clinical scenario. First results show the potential of such a system as an eye localization device. However, the low success rate prevents straightforward clinical application and needs further improvements aimed at increasing Corneal reflection visibility. This article is protected by copyright. All rights reserved.
Vinay A. Shah - One of the best experts on this subject based on the ideXlab platform.
-
Newly designed self-retaining contact lens for vitreous surgery.
American journal of ophthalmology, 2003Co-Authors: Kakarla V. Chalam, Chirag Patel, Vinay A. ShahAbstract:Abstract Purpose Development of a new self-retaining acrylic contact lens for vitreous surgery. Design A standard −60 diopters plano concave lens with the radius of Curvature 6.7 mm (less than the Cornea Curvature) was modified with addition of four foot plates to facilitate stability and centration. Method A drop of viscoelastic material placed between lens and Cornea induces negative suction and helps retain the lens in position. Conclusion This specially designed lens eliminates the need for suturing on the sclera or dependence on the assistant to provide placement. It provides a stable well-centered view of the fundus during vitreous surgery.