Patent Number: 
Section: claims

1. A radiotherapy apparatus, comprising:a radiation source configured to radiate a radiation ray;a multi leaf collimator, including a plurality of leaves, configured to limit a radiation range of the radiation ray; anda drive unit configured to move at least one of the leaves with an ultrasonic wave. 2. The radiotherapy apparatus according to claim 1, wherein the drive unit comprises:a metal material contacting a contact edge of the leaf in a contact pressure;a piezoelectric transducer which is placed on an opposite side to the contact edge of the metal material; anda signal generation unit configured to supply an electric signal to the piezoelectric transducer. 3. The radiotherapy apparatus according to claim 2, wherein the signal generation unit comprises:a first drive circuit which is provided to each leaf of a first band of leaves among the plurality of leaves; anda second drive circuit which is provided to each leaf of a second band of leaves among the plurality of leaves. 4. The radiotherapy apparatus according to claim 3, further comprising:a switch circuit, connected to the second drive unit, configured to select at least one leaf to be moved by the second drive unit among the second band of leaves. 5. The radiotherapy apparatus according to claim 4, wherein:the first band of leaves are positioned on an inner side to an isocentre; andthe second band of leaves are positioned on an outer side to the isocentre than the first band of leaves. 6. The radiotherapy apparatus according to claim 2, wherein the piezoelectric transducer is placed on a side edge of the leaf. 7. The radiotherapy apparatus according to claim 2,wherein the piezoelectric transducer and the metal material are placed on farther positions from an isocentre than a maximum radiation range. 8. A radiotherapy apparatus, comprising:a radiation source configured to radiate a radiation ray;a multi leaf collimator, including a plurality of leaves, configured to limit a radiation range of the radiation ray; andmeans for moving at least one of the leaves with an ultrasonic wave. 9. The radiotherapy apparatus according to claim 8, wherein the means for moving comprises:a metal material contacting a contact edge of the leaf in a contact pressure;a piezoelectric transducer which is placed on an opposite side to the contact edge of the metal material; anda signal generation unit configured to supply an electric signal to the piezoelectric transducer. 10. The radiotherapy apparatus according to claim 9, wherein the signal generation unit comprises:a first drive circuit which is provided to each leaf of a first band of leaves among the plurality of leaves; anda second drive circuit which is provided to each leaf of a second band of leaves among the plurality of leaves. 11. The radiotherapy apparatus according to claim 10, further comprising:a switch circuit, connected to the second drive unit, configured to select at least one leaf to be moved by the second drive unit among the second band of leaves. 12. The radiotherapy apparatus according to claim 11, wherein:the first band of leaves are positioned on an inner side to an isocentre; andthe second band of leaves are positioned on an outer side to the isocentre than the first band of leaves. 13. The radiotherapy apparatus according to claim 9, wherein the piezoelectric transducer is placed on a side edge of the leaf. 14. The radiotherapy apparatus according to claim 9,wherein the piezoelectric transducer and the metal material are placed on farther positions from an isocentre than a maximum radiation range. 15. A method for controlling a radiotherapy apparatus, comprising:radiating a radiation ray;limiting a radiation range of the radiation ray with a plurality of leaves; andmoving at least one of the leaves with an ultrasonic wave.