Lesion strength control by automatic temperature guided retinal photocoagulation

Schlott, Kerstin; Koinzer, Stefan; Baade, Alexander; Birngruber, Reginald; Roider, Johann; Brinkmann, Ralf

doi:10.1117/1.jbo.21.9.098001

Cited by 4 publications

(4 citation statements)

References 26 publications

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“…Our research group has previously reported on temperature-guided retinal photocoagulation with optoacoustic feedback. Koinzer et al 15 , 20 established a fixed-power variable-time approach, where a constant irradiation power was held until the desired aim temperature was reached. This was a first step toward more reproducible and uniform lesion strengths based on the Arrhenius damage integral accounting for the temperature and time of elevated temperature.…”

Section: Discussionmentioning

confidence: 99%

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Real-Time Temperature-Controlled Retinal Laser Irradiation in Rabbits

von der Burchard,

Kren,

Fleger

et al. 2024

Trans. Vis. Sci. Tech.

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Purpose Subdamaging thermal retinal laser therapy has the potential to induce regenerative stimuli in retinal diseases, but validated dosimetry is missing. Real-time optoacoustic temperature determination and control could close this gap. This study investigates a first in vivo application. Methods Two iterations of a control module that were optically coupled in between a continuous-wave commercial laser source and a commercial slit lamp were evaluated on chinchilla rabbits. The module allows extraction of the temperature rise in real time and can control the power of the therapy laser such that a predefined temperature rise at the retina is quickly achieved and held constant. Irradiations with aim temperatures from 45°C to 69°C were performed on a diameter of 200 µm and a heating time of 100 ms. Results We analyzed 424 temperature-guided irradiations in nine eyes of five rabbits. The mean difference between the measured and aim temperature was −0.04°C ± 0.98°C. The following ED 50 values for visibility thresholds could be determined: 58.6°C for funduscopic visibility, 57.7°C for fluorescein angiography, and 57.0°C for OCT. In all measurements, the correlation of tissue effect was higher to the temperature than to the average heating laser power used. Conclusions The system was able to reliably perform temperature-guided irradiations, which allowed for better tissue effect control than simple power control. This approach could enhance the accuracy, safety, and reproducibility of thermal stimulating laser therapy. Translational Relevance This study is a bridge between preclinical ex vivo experiments and a pilot clinical study.

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Section: Discussionmentioning

confidence: 99%

“…The pressure transients are recorded by an ultrasonic transducer (Medical Laser Center Lübeck, Lübeck, Germany) embedded in the contact lens and digitized by a data acquisition board. 17 , 20 A control-unit processes the data in real time to acquire the temperature rise.…”

Section: Methodsmentioning

confidence: 99%

Real-Time Temperature-Controlled Retinal Laser Irradiation in Rabbits

von der Burchard,

Kren,

Fleger

et al. 2024

Trans. Vis. Sci. Tech.

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“…In order to meet the need for proper energy dosing, Brinkmann et al [13] have developed an approach for online temperature measurement during retinal laser treatment using the photo-acoustic effect. It has already proven its feasibility during animal experiments on rabbits [9,14] and even in clinical studies [13]. Briefly, if a sufficiently short light pulse from the probe laser is absorbed by the RPE, the impulsive expansion gives rise to a pressure transient, which can be detected at the exterior corneal surface of the eye by means of an ultrasonic transducer.…”

Section: Introductionmentioning

confidence: 99%

Towards temperature controlled retinal laser treatment with a single laser at 10 kHz repetition rate

Mordmüller

Kleyman

Schaller

et al. 2021

Advanced Optical Technologies

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Laser photocoagulation is one of the most frequently used treatment approaches in ophthalmology for a variety of retinal diseases. Depending on indication, treatment intensity varies from application of specific micro injuries down to gentle temperature increases without inducing cell damage. Especially for the latter, proper energy dosing is still a challenging issue, which mostly relies on the physician’s experience. Pulsed laser photoacoustic temperature measurement has already proven its ability for automated irradiation control during laser treatment but suffers from a comparatively high instrumental effort due to combination with a conventional continuous wave treatment laser. In this paper, a simplified setup with a single pulsed laser at 10 kHz repetition rate is presented. The setup combines the instrumentation for treatment as well as temperature measurement and control in a single device. In order to compare the solely pulsed heating with continuous wave (cw) tissue heating, pulse energies of 4 µJ were applied with a repetition rate of 1 kHz to probe the temperature rise, respectively. With the same average laser power of 60 mW an almost identical temporal temperature course was retrieved in both irradiation modes as expected. The ability to reach and maintain a chosen aim temperature of 41 °C is demonstrated by means of model predictive control (MPC) and extended Kalman filtering at a the measurement rate of 250 Hz with an accuracy of less than ±0.1 °C. A major advantage of optimization-based control techniques like MPC is their capability of rigorously ensuring constraints, e.g., temperature limits, and thus, realizing a more reliable and secure temperature control during retinal laser irradiation.

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“…30 The creation of lesions of different strengths was also demonstrated on rabbits in vivo. 31,32 In this work, we present an alternative approach for a temperature-based feedback control, which adjusts the therapy laser power during the irradiation, in order to achieve a preset temperature rise within a fixed time frame.…”

Section: Introductionmentioning

confidence: 99%

Power-controlled temperature guided retinal laser therapy

et al. 2017

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Laser photocoagulation has been a treatment method for retinal diseases for decades. Recently, studies have demonstrated therapeutic benefits for subvisible effects. A treatment mode based on an automatic feedback algorithm to reliably generate subvisible and visible irradiations within a constant irradiation time is introduced. The method uses a site-individual adaptation of the laser power by monitoring the retinal temperature rise during the treatment using optoacoustics. This provides feedback to adjust the therapy laser power during the irradiation. The technique was demonstrated on rabbits in vivo using a 532-nm continuous wave Nd:YAG laser. The temperature measurement was performed with 523-nm Q-switched Nd:YLF laser pulses with 75-ns pulse duration at 1-kHz repetition rate. The beam diameter on the fundus was 200 μm for both lasers, respectively. The aim temperatures ranged from 50°C to 75°C in 11 eyes of 7 rabbits. The results showed ophthalmoscopically invisible effects below 55°C with therapy laser powers over a wide range. The standard deviation for the measured temperatures ranged from 2.1°C for an aim temperature of 50°C to 4.7°C for 75°C. The ED50 temperature value for ophthalmoscopically visible lesions in rabbits was determined as 65.3°C. The introduced method can be used for retinal irradiations with adjustable temperature elevations.

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Lesion strength control by automatic temperature guided retinal photocoagulation

Cited by 4 publications

References 26 publications

Real-Time Temperature-Controlled Retinal Laser Irradiation in Rabbits

Real-Time Temperature-Controlled Retinal Laser Irradiation in Rabbits

Towards temperature controlled retinal laser treatment with a single laser at 10 kHz repetition rate

Power-controlled temperature guided retinal laser therapy

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