Device for the treatment of biological tissue using laser radiation
An apparatus for the treatment of biological, in particular living tissue comprising a treatment laser device 1 for generating a pulsed treatment radiation directed on to a target tissue, in an embodiment additionally including a measurement laser device 2, 3 for generating a pulsed measurement radiation directed on to the target tissue of lower energy and shorter pulse duration than the treatment radiation, a detector device 4 for measuring pressure transients induced by the measurement radiation and a control device 6 for controlling the treatment radiation in dependence on the pressure transients evaluated in respect of a tissue change, wherein a regulating or control algorithm for controlling the treatment radiation is formed from the pressure transients.
1. An apparatus for the treatment of living tissue, comprising
a treatment device for generating a pulsed laser radiation to be directed on to a target tissue;
a detector device for detecting pressure amplitudes coming from the target tissue;
an evaluation device for evaluating the pressure amplitudes detected by the detector device; and
a control device for controlling the treatment radiation in dependence on the evaluated pressure amplitudes,
wherein
the evaluation device is adapted for evaluating a change of tissue condition in a second time interval Δt 2 which follows a first time interval Δt 1 in which no tissue change occurs at the target tissue, to determine a deviation of an averaged variation f(t) of the pressure amplitudes measured within the second time interval Δt 2 from a function a*m(t),
wherein m(t) represents a previously known curvature characteristic of the averaged temporal variation f(t) of the pressure amplitudes measured during the first time interval Δt 1 and a is determined from the fit condition f(t) =a*m(t) of a fit procedure at the end of Δt 1 ,
to determine a moment in time t i at which the deviation reaches a given value, and
in dependence on the determined moment in time t i , to predetermine treatment radiation parameters for a third time interval Δt 3 following the second time interval Δt 2 .
2. The apparatus as set forth in claim 1 wherein the control device is adapted to control the duration or the power of the respective pulse of the treatment radiation.
3. The apparatus as set forth in claim 1 , wherein the evaluation device has a memory or is connected to a memory in which the curvature variation m(t) of the function f(t) is stored.
4. The apparatus as set forth in claim 1 , wherein the evaluation device has a memory or is connected to a memory in which experimentally ascertained data are stored for predetermining the treatment parameters in the third time interval Δt 3 .
5. The apparatus as set forth in claim 1 , wherein the treatment duration in the third time interval Δt 3 is proportional to the duration of the second time interval Δt 2 , and the power of the treatment radiation remains the same during the second and third time intervals.
6. The apparatus as set forth in claim 1 , wherein in addition to the treatment device there is provided a measurement laser device for generating an additional pulsed measurement radiation directed on to the target tissue of lower energy and shorter pulse duration than in the case of the treatment radiation and the detector device is adapted to detect the pressure amplitudes induced by the measurement radiation and coming from the target tissue.
7. The apparatus as set forth in claim 1 , wherein the detector device is adapted to detect the pressure amplitudes induced by the treatment radiation and coming from the target tissue.
8. The apparatus as set forth in claim 7 wherein the frequency of the treatment radiation is at least 100 Hz.
9. The apparatus as set forth in claim 1 , wherein it is of a configuration for implementing photocoagulation at the fundus of an eye, in particular at the RPE.