A medical device comprising a hollow probe and ultrasound generation means disposed to direct a generated ultrasound wave to the tip of the hollow probe, wherein: the device further comprises suction monitoring means that comprises a flow sensor, wherein, in use, suction is applied through the hollow probe: the ultrasound generation means is adjusted in response to a suction flow rate through the probe detected by the suction monitoring means such that a decrease in the monitored suction flow rate through the hollow probe causes an increase in the magnitude and/or frequency of the ultrasound wave generated by the ultrasound generation means and directed to the tip of the probe: the device additionally comprises a temperature monitoring means, and wherein the ultrasound generation means is adjusted in response to a temperature detected by temperature monitoring means, and wherein the temperature monitoring means comprises at least one temperature sensor; and the at least one temperature sensor is coupled to the hollow probe, or the at least one temperature sensor is located within the device, or at least two temperature sensors are used one being coupled to the hollow probe and one being located within the device, the temperature sensor(s) being adapted to measure the temperature of the fluid flowing through the device. the device further comprises suction monitoring means that comprises a flow sensor, wherein, in use, suction is applied through the hollow probe: the ultrasound generation means is adjusted in response to a suction flow rate through the probe detected by the suction monitoring means such that a decrease in the monitored suction flow rate through the hollow probe causes an increase in the magnitude and/or frequency of the ultrasound wave generated by the ultrasound generation means and directed to the tip of the probe: the device additionally comprises a temperature monitoring means, and wherein the ultrasound generation means is adjusted in response to a temperature detected by temperature monitoring means, and wherein the temperature monitoring means comprises at least one temperature sensor; and the at least one temperature sensor is coupled to the hollow probe, or the at least one temperature sensor is located within the device, or at least two temperature sensors are used one being coupled to the hollow probe and one being located within the device, the temperature sensor(s) being adapted to measure the temperature of the fluid flowing through the device. the ultrasound generation means is adjusted in response to a suction flow rate through the probe detected by the suction monitoring means such that a decrease in the monitored suction flow rate through the hollow probe causes an increase in the magnitude and/or frequency of the ultrasound wave generated by the ultrasound generation means and directed to the tip of the probe: the device additionally comprises a temperature monitoring means, and wherein the ultrasound generation means is adjusted in response to a temperature detected by temperature monitoring means, and wherein the temperature monitoring means comprises at least one temperature sensor; and the at least one temperature sensor is coupled to the hollow probe, or the at least one temperature sensor is located within the device, or at least two temperature sensors are used one being coupled to the hollow probe and one being located within the device, the temperature sensor(s) being adapted to measure the temperature of the fluid flowing through the device. the device additionally comprises a temperature monitoring means, and wherein the ultrasound generation means is adjusted in response to a temperature detected by temperature monitoring means, and wherein the temperature monitoring means comprises at least one temperature sensor; and the at least one temperature sensor is coupled to the hollow probe, or the at least one temperature sensor is located within the device, or at least two temperature sensors are used one being coupled to the hollow probe and one being located within the device, the temperature sensor(s) being adapted to measure the temperature of the fluid flowing through the device.