TY - JOUR

T1 - Towards temperature controlled retinal laser treatment with a single laser at 10 kHz repetition rate

AU - Mordmüller, Mario

AU - Kleyman, Viktoria

AU - Schaller, Manuel

AU - Wilson, Mitsuru

AU - Theisen-Kunde, Dirk

AU - Worthmann, Karl

AU - Müller, Matthias A.

AU - Brinkmann, Ralf

N1 - Funding Information: We also gratefully acknowledge C. Kren and V. Danicke from the Medical laser Center Lübeck for supporting this work.

PY - 2021/12/20

Y1 - 2021/12/20

N2 - 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.

AB - 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.

KW - extended Kalman filter

KW - laser-coagulation

KW - model predictive control

KW - ophthalmology

KW - photo-acoustics

UR - http://www.scopus.com/inward/record.url?scp=85120051524&partnerID=8YFLogxK

U2 - 10.1515/aot-2021-0041

DO - 10.1515/aot-2021-0041

M3 - Article

AN - SCOPUS:85120051524

VL - 10

SP - 423

EP - 431

JO - Advanced Optical Technologies

JF - Advanced Optical Technologies

SN - 2192-8576

IS - 6

ER -