Ultrasound system and method
An ultrasound system ( 1 ) is disclosed that comprises a probe ( 10 ) including an array ( 110 ) of CMUT (capacitive micromachined ultrasound transducer) cells ( 100 ), each cell comprising a substrate ( 112 ) carrying a first electrode ( 122 ), the substrate being spatially separated from a flexible membrane ( 114 ) including a second electrode ( 120 ) by a gap ( 118 ); and a bias voltage source ( 45 ) coupled to said probe and adapted to provide the respective first electrodes and second electrodes of at least some of the CMUT cells with a monotonically varying bias voltage including a monotonically varying frequency modulation in a transmission mode of said probe such that the CMUT cells are operated in a collapsed state and transmit at least one chirped pulse during said transmission mode. Such a system for instance may be an ultrasound imaging system or an ultrasound therapeutic system. An ultrasonic pulse generation method using such as system is also disclosed.
1. An ultrasound system comprising:
a probe including an array of CMUT (capacitive micromachined ultrasound transducer) cells, each cell comprising a substrate carrying a first electrode the substrate being spatially separated from a flexible membrane including a second electrode by a gap; and
a voltage source coupled to said probe and adapted to provide the respective first electrodes and second electrodes of at least some of the CMUT cells with a monotonically varying voltage including a monotonically varying frequency modulation in a transmission mode of said probe such that the CMUT cells are operated in a collapsed state and transmit at least one chirped pulse during said transmission mode.
2. The ultrasound system of claim 1 , wherein the voltage source comprises:
a first stage adapted to generate a static component of said monotonically varying voltage during said transmission mode, wherein the static component is sufficient to force the CMUT cells in the collapsed state; and
a second stage adapted to generate a monotonically varying component of said voltage, said monotonically varying component including the monotonically varying frequency modulation, and wherein the voltage source is adapted to combine the static component and the monotonically varying component to form the monotonically varying voltage including the monotonically varying frequency modulation.
3. The ultrasound system of claim 1 , wherein the monotonically varying voltage and the monotonically varying frequency modulation are monotonically increasing.
4. The ultrasound system of claim 1 , wherein the monotonically varying frequency modulation is matched to monotonic variations in a resonance frequency of respective membranes of the CMUT cells induced by the monotonically varying bias voltage.
5. The ultrasound system of claim 1 , wherein the monotonically varying frequency modulation is a linearly increasing frequency modulation.
6. The ultrasound system of claim 1 , further comprising a plate of a dispersive material in front of the array of CMUT cells for compressing said chirped pulse.
7. The ultrasound system of claim 6 , wherein the plate is removably mounted in front of said array.
8. The ultrasound system of claim 6 , wherein the plate has a thickness of half an optimum thickness for said compression.
9. The ultrasound system of claim 1 , wherein the at least one chirped pulse has a duration ranging from 0.1-1.0 microseconds.
10. The ultrasound system of claim 1 , wherein the voltage source is further adapted to provide the respective first electrodes and second electrodes of at least some of the CMUT cells with a further voltage that forces the CMUT cells in the collapsed state during a reception mode of said probe.
11. The ultrasound system of claim 10 , further comprising a user interface, wherein the voltage source is adapted to provide the further voltage as defined by a user using said user interface during the reception mode.
12. The ultrasound system of claim 1 , wherein the ultrasound system is an ultrasound diagnostic imaging system or an ultrasound therapeutic system.
13. A method of ultrasonic pulse transmission, comprising:
providing an array of CMUT (capacitive micromachined ultrasound transducer) cells, each cell comprising a substrate carrying a first electrode, the substrate being spatially separated from a flexible membrane, including a second electrode by a gap; and
providing, in a transmission mode, the respective first and second electrodes of at least some of the CMUT cells with a monotonically varying voltage including a monotonically varying frequency modulation such that the CMUT cells are operated in a collapsed state and transmit at least one chirped pulse, preferably wherein the CMUT cells are operated in a deep collapse mode.
14. The method of claim 13 , further comprising transmitting the at least one chirped pulse through a dispersive material to compress the at least one chirped pulse.
15. The method of claim 13 , further comprising providing, in a reception mode, the respective first and second electrodes of at least some of the CMUT cells with a further voltage forcing the CMUT cells in the collapsed state.