Method and apparatus for irradiating a surface with pulsed light
A method and apparatus irradiates a surface with at least one pulsed light beam emitted from an emission surface of an optical element. The at least one pulsed light beam comprises a plurality of pulses having a temporal pulsewidth in a range between about 0.1 millisecond and about 150 seconds. The at least one pulsed light beam has a beam cross-sectional area at the emission surface greater than about 2 cm 2 and a time-averaged irradiance in a range between about 1 mW/cm 2 and about 100W/cm 2 .
1. A method of irradiating a portion of a patient's scalp or skull with light, the method comprising:
delivering a pulsed light beam to the patient's scalp or skull from an emission surface of an output optical element in communication with a source of light;
providing a thermal conduit in thermal communication with the output optical element and with a cooling mechanism; and
cooling the output optical element using the cooling mechanism via the thermal conduit,
wherein the pulsed light beam comprises a plurality of pulses having a temporal pulsewidth in a range between 0.1 millisecond and 150 seconds, the pulsed light beam having a cross-sectional area greater than 2 cm 2 at the emission surface of the output optical element, and having a temporal profile comprising a time-averaged irradiance in a range of 10 mW/cm 2 to 10 W/cm 2 across the cross-sectional area, and
wherein the temporal profile does not optimize a thermal relaxation of an irradiated brain tissue.
2. The method of claim 1 , further comprising selecting the patient, wherein the patient is selected at least partly because the patient has experienced one or more conditions selected from the group consisting of a primary destructive event, Parkinson's disease, and depression.
3. The method of claim 1 , wherein the pulsed light beam has a fluence at a cortical surface of a brain of the patient between 12.5 μJ/cm 2 to 1 J/cm 2 .
4. The method of claim 1 , wherein the pulsed light beam at the emission surface has a beam diameter in a range between 10 millimeters and 40 millimeters, an average irradiance per pulse in a range between 10 mW/cm 2 and 10 W/cm 2 , one or more wavelengths in a range between 600 nanometers and 1064 nanometers.
5. The method of claim 1 , wherein the source of light comprises a laser light source.
6. The method of claim 1 , wherein the output optical element comprises sapphire.
7. The method of claim 1 , wherein the output optical element comprises diamond, calcium fluoride, or zinc selenide.
8. The method of claim 1 , wherein the output optical element comprises a rigid, optically transmissive, and thermally conductive material.
9. The method of claim 1 , wherein the output optical element comprises a flexible optically transmissive, and thermally conductive material.
10. The method of claim 1 , wherein the output optical element has a thermal conductivity of at least 10 watts/meter-K.
11. The method of claim 1 , wherein the emission surface is concave to conform to a curvature of the patient's scalp or skull, thereby reducing or preventing air gaps from forming between the emission surface and the patient's scalp or skull.
12. The method of claim 1 , wherein the emission surface comprises one or more optical coatings, films, layers, or membranes configured to reduce back reflections.
13. The method of claim 1 , wherein the emission surface comprises one or more diffusers.
14. The method of claim 1 , wherein the temporal pulsewidth is in a range between 0.1 millisecond and 300 milliseconds.
15. The method of claim 1 , wherein the cross-sectional area is in a range of 2 cm 2 to 20 cm 2 at the emission surface of the output optical element.
16. The method of claim 1 , wherein the output optical element has an aperture diameter of less than 33 millimeters.
17. The method of claim 1 , wherein the pulsed light beam comprises one or more wavelengths in a range between 600 nanometers and 1064 nanometers.
18. The method of claim 1 , wherein the time-averaged irradiance at the scalp or skull provides a time-averaged irradiance greater than 0.01 mW/cm 2 to a target subsurface tissue of a brain of the patient below a dura of the patient.
19. The method of claim 1 , wherein the time-averaged irradiance at the emission surface averaged over one second is in a range between 100 mW/cm 2 and 10 W/cm 2 and a peak irradiance at the scalp is in a range between 10 mW/cm 2 and 10 W/cm 2 .
20. The method of claim 19 , wherein the pulsed light beam has one or more wavelengths in a range between 600 nanometers and 1064 nanometers.
21. The method of claim 19 , wherein the temporal profile further comprises a temporal pulsewidth in a range between 0.1 millisecond and 300 milliseconds.
22. The method of claim 1 , wherein the pulsed light beam has a duty cycle in a range between 10% and 30%.
23. The method of claim 1 , wherein a timing of the temporal profile corresponds to a timing of a biomolecular process involved in an absorption of one or more photons in the irradiated brain tissue.