Modulated Laser Pulse for Tissue Ablation
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Solution Overview
Problem
Pulsed laser systems for tissue ablation face challenges in minimizing heat deposition in tissues while reducing undesirable effects from debris clouds, such as high-intensity light emission and thermal necrosis, particularly at short pulse durations.
Innovation Solution
A modulated laser system with pulses of longer duration (≥ 350 microseconds) that oscillates between intensity maxima and minima, synchronizing intensity modulation with debris cloud oscillations to keep laser intensity low during debris cloud maxima, thereby reducing heat deposition and debris-laser interaction effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If short laser pulses are used to achieve cold regime ablation, then heat deposition in tissue is reduced, but interaction with debris cloud increases causing undesirable effects
Solution Approach 1:
The laser pulse intensity is modulated periodically during the pulse duration, creating multiple intensity maxima and minima. This periodic modulation allows the laser to interact with the debris cloud in a controlled manner, reducing continuous interaction effects while maintaining effective ablation through the intensity maxima phases.
Solution Approach 2:
The laser pulse intensity is dynamically adjusted during the pulse duration rather than maintaining a constant intensity. The intensity profile changes over time with multiple maxima and minima, allowing optimization of both heat deposition control and debris cloud interaction at different time points within the same pulse.
2Object-generated harmful factors
If long laser pulses are used to reduce debris cloud interaction, then undesirable effects are reduced, but heat deposition in tissue increases
Solution Approach 1:
By implementing periodic intensity modulation with multiple maxima and minima within the pulse, the system achieves reduced debris cloud interaction during intensity minima phases while maintaining effective ablation during intensity maxima phases, avoiding the continuous heat deposition problem of long constant-intensity pulses.
Solution Approach 2:
The continuous laser pulse is segmented into multiple intensity phases (maxima and minima) rather than maintaining a single constant intensity level. This segmentation allows different portions of the pulse to serve different functions: maxima for ablation and minima for reduced debris interaction.
3Productivity
If high laser intensity is used to improve ablation speed, then productivity increases, but thermal necrosis risk increases
Solution Approach 1:
The periodic intensity modulation creates alternating phases of high intensity (for fast ablation) and lower intensity (for heat dissipation), allowing the tissue to cool between intensity maxima and reducing the risk of thermal necrosis while maintaining high overall ablation speed.
Solution Approach 2:
The dynamic intensity profile adjusts the laser intensity in real-time during the pulse, applying high intensity only when needed for ablation while allowing heat dissipation during lower intensity phases, thereby optimizing the balance between ablation speed and thermal damage prevention.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The modulated laser system achieves low heat deposition in tissues and reduced interaction with debris clouds, minimizing thermal damage and undesirable effects like light emission and burning smells, while maintaining efficient ablation.
Implementation Method 1
pulsed lasers are used for the removal of hard and soft body tissues such as dental enamel, dentine, bone material, skin and mucosa. The material removal in tissue ablation is based on a pronounced absorption of the temporally limited laser pulse in the ablated tissue. The laser absorption leads to local heating with sudden evaporation that causes material removal.
Implementation Method 2
The material removal in tissue ablation is based on a pronounced absorption of the temporally limited laser pulse in the ablated tissue. The laser absorption leads to local heating with sudden evaporation that causes material removal.
Implementation Method 3
When the individual pulse impinges on the aforementioned debris cloud, the cloud particles get rapidly heated up to very high temperatures, sometimes leading to plasma formation within the surrounding gases and air.
Data Source
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AI summary
A Laser system is disclosed which comprises a pump, wherein the laser system is adapted to be operated in pulsed operation so that at least one individual pulse of a temporally limited pulse duration (To) is generated, wherein the pulse ablates a material such that a debris cloud forms above the ablated material. Further, the pump power of the pump is modulated in such a way that the following three conditions are fulfilled: (1) the intensity of the pulse oscillates between maximum values and minimum values during the pulse duration, wherein the laser pulse comprises a plurality of intensity maxima Imax which occur at times {Ti, i=1, ... N}; and a plurality of intensity minima Imin which occur at times {tk, k=1, ... (N-1)}, wherein the intensity does not vanish at the intensity minima; (2) the intensity oscillations of the laser pulse induce oscillations of the size of the debris cloud so that, during the pulse duration (To), there are at least two maxima of the size of the debris cloud which occur at times {τj, j=1, ... M} and which are located in between two intensity maxima of the laser pulse; and (3) at least 70 percent of the maxima of the size of the debris cloud occur near an intensity minimum of the pulse such that, for at least 70 percent of the maxima of the size of the debris cloud, the intensity of the pulse I(τj) at the time of the maximum of the size of the debris cloud is smaller than Imin(tk) + 0.5 x [Imax (Ti) - Imin(tk) ], wherein Imin(tk) is the intensity minimum of the pulse which is closest to the maximum of the size of the debris cloud at time τj and Imax(Ti) is the intensity maximum of the pulse which is closest to the maximum of the size of the debris cloud at time τj.