Ultrasound systems

1. A sensing system to sense a parameter of an object, the sensing system comprising a transducer arranged to generate pressure waves directed at the object, at least one pressure wave detector arranged to detect cavitation in the object and output detection signals, and a controller arranged to receive the detection signals from the at least one detector, to process the detection signals to measure a signal parameter of the detection signals that varies with the parameter of the object,

wherein the controller has stored therein a record of either a relationship between the parameter of the object and the signal parameter, or at least one reference variation in the signal parameter that corresponds to a respective variation in the parameter of the object, and the controller is arranged to use the record to generate a sensor output that varies in response to changes in the signal parameter, wherein either:

(a) the parameter of the object is temperature, and the signal parameter is arranged to vary with a level of cavitation activity in the object;

(b) the parameter of the object is a viscoelastic parameter, and the controller is arranged to determine a cavitation threshold pressure from the signal parameter;

(c) the parameter of the object is a viscoelastic parameter, and the signal parameter is a parameter of the frequency content of the detection signals; or

(d) the parameter of the object is a presence of lesions, and the signal parameter is a parameter of the spectral content of the detection signals.

2. A system according to claim 1 wherein the sensor output is arranged to control the transducer to vary an output of the transducer in response to changes in the sensor output.

3. A system according to claim 1 further comprising a feedback device arranged to provide feedback to a user, wherein the sensor output is arranged to control the feedback device and to vary the feedback in response to changes in the sensor output.

4. A system according to claim 1 wherein the controller is arranged to define a target range of the signal parameter, and to change the sensor output in response to the signal parameter being outside the target range.

5. A system according to claim 1 wherein the signal parameter is a variance of the detection signals.

6. A system according to claim 1 wherein the controller is arranged to monitor how the signal parameter changes in response to changes in the sensor output.

7. A system according to claim 1 wherein the signal parameter is a timing parameter.

8. A system according to claim 7 wherein the signal parameter is indicative of a cavitation threshold of the object.

9. A method of sensing a parameter of an object comprising:

generating pressure waves directed at the object;

sensing cavitation in the object using at least one pressure wave detector arranged to output detection signals;

measuring a signal parameter of the detection signals that varies with a parameter of the object;

accessing a record of either a relationship between the parameter of the object and the signal parameter, or at least one reference variation in the signal parameter that corresponds to a respective variation in the parameter of the object, and

using the record to generate a sensor output; wherein either:

(a) the parameter of the object is temperature, and the signal parameter is arranged to vary with a level of cavitation activity in the object;

(b) the parameter of the object is a viscoelastic parameter, and a cavitation threshold pressure is determined from the signal parameter;

(c) the parameter of the object is a viscoelastic parameter, and the signal parameter is a parameter of the frequency content of the detection signals; or

(d) the parameter of the object is a presence of lesions, and the signal parameter is a parameter of the spectral content of the detection signals.

10. A method according to claim 9 wherein the sensing output varies in response to changes in the signal parameter.