Ultrasound autofocusing using reflections
Various approaches of focusing an ultrasound transducer having multiple transducer elements to a target region include generating at least one acoustic reflector in the target region; transmitting ultrasound waves to the acoustic reflector; measuring reflections off the acoustic reflector; and based at least in part on the measured reflections, adjusting the parameter value associated with the transducer element(s).
1. A system for focusing an ultrasound transducer comprising:
an ultrasound transducer comprising a plurality of transducer elements; and
a controller configured to:
(a) cause generation of one or more microbubbles in a target region using the ultrasound transducer;
(b) transmit ultrasound waves, based on initial parameter values associated with the transducer elements, to the target region;
(c) cause a detector device or a sub-region of the ultrasound transducer to measure reflections of the ultrasound waves transmitted in step (b) off at least one of the one or more microbubbles in the target region;
(d) based at least in part on the measured reflections, adjust a parameter value associated with at least one of the transducer elements;
(e) transmit ultrasound waves, based on the adjusted parameter value, to the target region;
(f) cause the detector device or the sub-region of the ultrasound transducer to measure reflections of the ultrasound waves transmitted in step (e) off at least one of the one or more microbubbles in the target region; and
(g) repeat steps (d), (e), and (f) until a stopping condition is satisfied,
wherein the stopping condition corresponds to a deviation between (i) a phase difference between ultrasound waves transmitted in step (e) and measured reflections thereof and (ii) a phase difference between ultrasound waves transmitted in a previous iteration of step (e) and measured reflections thereof, being below a threshold.
2. The system of claim 1 , wherein the controller is configured to cause the detector device to measure the reflections.
3. The system of claim 1 , wherein the controller is further configured to cause an imager and/or the detector device to detect generation of the one or more microbubbles in the target region.
4. The system of claim 1 , wherein the controller is configured to cause the sub-region of the ultrasound transducer to measure the reflections.
5. The system of claim 1 , wherein the controller is further configured to cause the ultrasound waves transmitted in step (b) to generate the one or more microbubbles in the target region in step (a).
6. The system of claim 1 , wherein the controller is further configured to, in step (a), cause the transducer elements to transmit ultrasound waves to the target region so as to generate the one or more microbubbles before transmission of the ultrasound waves in step (b).
7. The system of claim 6 , wherein the controller is further configured to transmit the ultrasound waves transmitted in at least one of step (a) or step (b) based at least in part on a physical model.
8. The system of claim 6 , wherein the controller is further configured to transmit the ultrasound waves in step (a) having a value of a constitutive parameter different from that of the ultrasound waves in step (b).
9. The system of claim 8 , wherein the constitutive parameter comprises at least one of an intensity level or a frequency.
10. The system of claim 6 , wherein the ultrasound transducer comprises a plurality of sub-regions, each sub-region comprising a plurality of transducer elements, wherein the plurality of sub-regions includes the sub-region in step (c).
11. The system of claim 10 , wherein the controller is further configured to cause different sub-regions of the transducer to transmit ultrasound waves in different iterations of step (e).
12. The system of claim 10 , wherein the controller is further configured to cause a first sub-region to transmit the ultrasound waves in step (e) and the sub-region to measure the reflections in step (f), the first sub-region being different from the sub-region.
13. The system of claim 10 , wherein the controller is further configured to cause the sub-region of the transducer to transmit the ultrasound waves in step (e) and subsequently measure the reflections in step (f).
14. The system of claim 1 , wherein the controller is further configured to initially estimate the parameter value based on a measurement of transmitted or reflected ultrasound waves.
15. The system of claim 1 , wherein the parameter value comprises at least one of a frequency, a phase, or an amplitude of a signal driving at least one of the transducer elements.