Systems and methods for thermometry and theranostic applications

1. A method of measuring temperature in an environment, the method comprising:

(a) disposing a population of ultrasound-switchable fluorophores in the environment, the population comprising a first ultrasound-switchable fluorophore having a first switching threshold temperature;

(b) exposing the environment to an ultrasound beam to create an activation region within the environment, the activation region having a temperature greater than or equal to the first switching threshold temperature;

(c) disposing the population of fluorophores within the activation region to switch at least one fluorophore of the population from an off state to an on state;

(d) exposing the environment to a beam of electromagnetic radiation, thereby exciting at least one fluorophore of the population in the on state;

(e) detecting a first photoluminescence signal emitted by the population of fluorophores; and

(f) correlating the first photoluminescence signal with a first temperature or temperature range including the first switching threshold temperature.

2. The method of claim 1 , wherein the first photoluminescence signal emitted by the population of fluorophores is detected using a detector comprising a plurality of optical fiber collectors coupled to a camera or photon counter, wherein the optical fiber collectors are spatially distributed around an exterior surface of the environment.

3. The method of claim 1 , wherein correlating the first photoluminescence signal with a first temperature or temperature range comprises determining a final temperature (T(tp)) of the activation region following exposure of the activation region to the ultrasound beam according to Equation (1).

4. The method of claim 1 , wherein the ultrasound beam is modulated and correlating the first photoluminescence signal with a first temperature or temperature range comprises determining a first peak-to-peak modulated photoluminescence signal based on the modulated ultrasound beam.

5. The method of claim 1 , wherein exposing the environment to an ultrasound beam also heats the environment.

6. The method of claim 1 , wherein correlating the first photoluminescence signal with a first temperature or temperature range comprises determining a temporal profile of the temperature of the activation region.

7. The method of claim 6 , wherein determining the temporal profile of the temperature of the activation region comprises equating the first switching threshold temperature to the temperature of the environment at one or more time points, the time points corresponding to the initial detection or initial loss of the first photoluminescence signal.

8. The method of claim 1 , wherein the population of ultrasound-switchable fluorophores further comprises a second ultrasound-switchable fluorophore having a second switching threshold temperature, the second switching threshold temperature being higher than the first switching threshold temperature.

9. The method of claim 8 , wherein the activation region has a temperature greater than or equal to the second switching threshold temperature.

10. The method of claim 9 , further comprising:

(g) detecting a second photoluminescence signal emitted by the population of fluorophores; and

(h) correlating the second photoluminescence signal with a second temperature or temperature range including the second switching threshold temperature.

11. The method of claim 10 , wherein:

exposing the environment to a beam of electromagnetic radiation comprises exposing the environment to a first excitation beam and a second excitation beam;

wherein the first excitation beam and the second excitation beam have differing wavelength maxima; and

wherein the first excitation beam primarily excites the first ultrasound-switchable fluorophore;

wherein the second excitation beam primarily excites the second ultrasound-switchable fluorophore; and

wherein the first and second excitation beams are provided to the environment sequentially.

12. The method of claim 11 , wherein:

the first photoluminescence signal is detected with a first detector or detection channel;

the second photoluminescence signal is detected with a second detector or detection channel;

the first detector or detection channel is off when the second photoluminescence signal is detected; and

the second detector or detection channel is off when the first photoluminescence signal is detected.

13. The method of claim 10 , wherein the population of ultrasound-switchable fluorophores further comprises a third ultrasound-switchable fluorophore having a third switching threshold temperature and a fourth ultrasound-switchable fluorophore having a fourth switching threshold temperature, the third switching threshold temperature being higher than the second switching threshold temperature and the fourth switching threshold temperature being higher than the third switching threshold temperature.

14. The method of claim 13 , wherein the activation region has a temperature greater than or equal to the third switching threshold temperature or greater than or equal to the fourth switching threshold temperature.

15. The method of claim 14 , further comprising:

(i) detecting a third photoluminescence signal emitted by the population of fluorophores;

(j) correlating the third photoluminescence signal with a third temperature or temperature range including the third switching threshold temperature;

(k) detecting a fourth photoluminescence signal emitted by the population of fluorophores; and

(l) correlating the fourth photoluminescence signal with a fourth temperature or temperature range including the fourth switching threshold temperature.

16. The method of claim 15 , wherein the first, second, third, and fourth temperatures or temperature ranges span a total temperature range in a continuous manner.