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

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Mario Mordmüller ◽  
Viktoria Kleyman ◽  
Manuel Schaller ◽  
Mitsuru Wilson ◽  
Dirk Theisen-Kunde ◽  
...  
Keyword(s):  
Temperature Measurement ◽  
Laser Treatment ◽  
Repetition Rate ◽  
Continuous Wave ◽  
Cell Damage ◽  
Pulsed Laser ◽  
Extended Kalman Filtering ◽  
Tissue Heating ◽  
Pulsed Heating ◽  
Measurement And Control

Abstract 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.

scholarly journals Effects of pulse width and repetition rate of pulsed laser on kinetics and production of singlet oxygen luminescence

2016 ◽  
Vol 09 (06) ◽  
pp. 1650019 ◽  
Author(s):  
Defu Chen ◽  
Ying Wang ◽  
Buhong Li ◽  
Huiyun Lin ◽  
Xuechun Lin ◽  
...  
Keyword(s):  
Singlet Oxygen ◽  
Repetition Rate ◽  
Pulse Width ◽  
Near Infrared ◽  
Continuous Wave ◽  
Laser Excitation ◽  
Pulsed Laser ◽  
Cw Laser ◽  
Difference Formula ◽  
Significant Difference

Pulsed and continuous-wave (CW) lasers have been widely used as the light sources for photodynamic therapy (PDT) treatment. Singlet oxygen (1O2) is known to be a major cytotoxic agent in type-II PDT and can be directly detected by its near-infrared luminescence at 1270[Formula: see text]nm. As compared to CW laser excitation, the effects of pulse width and repetition rate of pulsed laser on the kinetics and production of 1O2 luminescence were quantitatively studied during photosensitization of Rose Bengal. Significant difference in kinetics of 1O2 luminescence was found under the excitation with various pulse widths of nanosecond, microsecond and CW irradiation with power of 20[Formula: see text]mW. The peak intensity and duration of 1O2 production varied with the pulse widths for pulsed laser excitation, while the 1O2 was generated continuously and its production reached a steady state with CW excitation. However, no significant difference ([Formula: see text]) in integral 1O2 production was observed. The results suggest that the PDT efficacy using pulsed laser may be identical to the CW laser with the same wavelength and the same average fluence rate below a threshold in solution.

Clinical effects of dynamic cooling during pulsed laser treatment of port-wine stains

1997 ◽  
Vol 12 (4) ◽  
pp. 320-327 ◽  
Author(s):  
E. J. Fiskerstran ◽  
K. Ryggen ◽  
L. T. Norvang ◽  
L. O. Svaasand
Keyword(s):  
Laser Treatment ◽  
Pulsed Laser ◽  
Clinical Effects ◽  
Port Wine ◽  
Port Wine Stains ◽  
Dynamic Cooling

scholarly journals Time-Resolved Quadrupole Mass Spectrometric Studies on Pulsed Laser Ablation of TiO2

1999 ◽  
Vol 18 (3) ◽  
pp. 99-109 ◽  
Author(s):  
Yongxin Tang ◽  
Zhenhui Han ◽  
Qizong Qin
Keyword(s):  
Laser Ablation ◽  
Continuous Wave ◽  
Center Of Mass ◽  
Pulsed Laser ◽  
Pulsed Laser Ablation ◽  
Ionic Species ◽  
Mass Spectrometric ◽  
Quadrupole Mass ◽  
Time Resolved ◽  
Ambient Oxygen

Pulsed laser ablation of TiO2 at 355 nm and 532 nm has been investigated using an angleand time-resolved quadrupole mass spectrometric technique. The major ablated species include O (m/e = 16), O2 (m/e = 32), Ti (m/e = 48), TiO (m/e = 64) and TiO2 (m/e = 80). The time-of-flight (TOF) spectra of ablated species are measured for the ionic and neutral ablated species, and they can be fitted by a Maxwell – Boltzmann (M – B) distribution with a center-of-mass velocity. The measured angular distributions of the ionic species (O+ and Ti+) and the neutral species (O and Ti) can be fitted with cos⁡nθ and a cos⁡θ + (1−a)cos⁡nθ, respectively. In addition, a continuous wave oxygen molecular beam is introduced into the ablated plume, and the enhancement of the signal intensities of TiO is observed. It implies that the ablated Ti atoms/ions species can react with ambient oxygen molecules in the gas phase. In the meanwhile, the physicochemical mechanism of pulsed laser ablation of TiO2 is discussed.

Continuous-wave and Pulsed Laser Performance of Yb∶LuAG Single Crystal Fiber

2022 ◽  
Vol 43 (01) ◽  
pp. 42-50
Author(s):  
Xiao-fei MA ◽  
◽  
Tao WANG ◽  
Jian ZHANG ◽  
Yan-ru YIN ◽  
...  
Keyword(s):  
Single Crystal ◽  
Continuous Wave ◽  
Pulsed Laser ◽  
Laser Performance ◽  
Crystal Fiber

Introducing Temperature Measurement and Control Techniques to Engineering Undergraduate Students in the Gulf Region

2008 ◽  
Author(s):  
Peter Rodgers ◽  
Arman Molki
Keyword(s):  
Engineering Education ◽  
Temperature Measurement ◽  
Temperature Control ◽  
Instrumentation Amplifier ◽  
Gulf Region ◽  
Linear Temperature ◽  
Control Techniques ◽  
The Third ◽  
And Control ◽  
Measurement And Control

Hands-on laboratory skills play a vital role in providing students with a sound understanding of the scientific fundamentals and their application in solving real-life engineering problems. One of the essential laboratory based courses taught at our Institute is Introduction to Measurements and Instrumentation. The design and implementation of such a course has been well documented in Western engineering education, but presents specific challenges in the Gulf region due to economical, social and cultural factors. This paper discusses the adaptation of corresponding Western courses to undergraduate mechanical engineering studies in the Gulf region. Laboratory exercises for temperature measurement and control are described, which consist of four modules, each building upon the other. In each module, students learn how to design an accurate measuring system, and process and interpret collected data. In the first module, the students are required to build a thermocouple reader using an AD620 instrumentation amplifier and to compare measurements with NIST reference tables. The second module is an introduction to LabVIEW, a graphical data acquisition programming language. The students are required to write a LabVIEW program to record multiple thermocouple signals from a heated plate under varying convective cooling conditions, using a high resolution temperature logger with on-board signal conditioning. The third and fourth modules focus on temperature control techniques. In the third laboratory exercise, the students are required to construct an electrical circuit using a low-power PCB relay and NPN bipolar transistor to develop a bang-bang linear temperature controller. The program created in module two is modified to have the heater operation automatically controlled for a fixed temperature set point. In module four, the students replace the bang-bang controller built in the previous lab with a commercially available PID controller and explore the differences between PID and linear temperature control systems. For each module, students are required to submit a formal report covering the theoretical background, the experimental procedure employed, uncertainty analysis, and conclusions and recommendations. An effective teaching strategy is outlined that covers the fundamental concepts of temperature measurement and control through carefully designed experiments, with sample results presented. Emphasis is placed on the tailoring of the course topics to engineering education in the Gulf region.

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