The invention is related to a method for monitoring a range of a particle beam in a target. The method is using gamma detectors for detecting prompt gammas produced in the target. The time differences between the time of detecting a gamma quantum and a time of emission of a particle or a bunch of pa
The invention is related to a method for monitoring a range of a particle beam in a target. The method is using gamma detectors for detecting prompt gammas produced in the target. The time differences between the time of detecting a gamma quantum and a time of emission of a particle or a bunch of particles from the radiation device are determined. A statistical distribution of those time difference is used to deduce information related to the range of the beam. The invention is also related to an apparatus for monitoring a range based on measured time profiles of detected prompt gammas.
대표청구항▼
1. A method for monitoring the range of a particle beam in a target, said particle beam being delivered by a radiation device, the method comprising the steps of a) providing a gamma detector configured to detect gamma quanta produced by said particle beam in said target, said gamma detector is conf
1. A method for monitoring the range of a particle beam in a target, said particle beam being delivered by a radiation device, the method comprising the steps of a) providing a gamma detector configured to detect gamma quanta produced by said particle beam in said target, said gamma detector is configured to generate a detection timing signal which is correlated with a time of detection of a gamma quantum at said detector,b) providing a reference timing signal which is correlated with a time of emission of a single particle or a particle bunch from said radiation device,c) detecting gamma quanta with said gamma detector,d) determining for a number of detected gamma quanta, a time difference between the time of detection of a gamma quantum and a time of emission of the single particle or the particle bunch which has produced the gamma quantum detected,e) making a statistical distribution MDIS of the time differences obtained in the previous step,f) analyzing said statistical distribution MDIS so as to obtain information about said range of the particle beam. 2. A method according to claim 1 wherein said step f of analyzing comprises the additional steps of: f1 acquiring a reference distribution REFDIS, said reference distribution REFDIS is corresponding to an expected distribution of time differences,f2 comparing said statistical distribution MDIS obtained in step e with said reference distribution REFDES obtained in step f1. 3. A method according to claim 2 wherein step f2 further comprises the sub-steps of i. determining a statistical parameter from said statistical distribution MDIS,ii. determining from said reference distribution REFDIS a reference statistical parameter corresponding to the statistical parameter determined in step i,iii. comparing the statistical parameter obtained in step i with the reference statistical parameter obtained in step ii. 4. A method according to claim 3 wherein said reference distribution REFDIS is obtained through a model calculation or the reference distribution REFDIS is obtained from a previously performed measurement. 5. A method according to claim 2 wherein said detection timing signal and said reference timing signal are provided with an uncertainty in time equal or less than 10 ns. 6. An apparatus for monitoring a range of a particle beam in a target, said particle beam comprises particles or bunches of particles delivered by a radiation device for radiation therapy, said apparatus comprising a gamma detector for detecting gamma quanta produced by a particle beam in a target, said gamma detector is configured to generate a detection timing signal which is correlated with a time of detection of a gamma quantum at said gamma detector,an analyzer comprising i. a first interface for receiving as an input said detection timing signal,ii. a second interface for receiving as an input a reference timing signal, said reference timing signal being correlated with a time of emission of a single particle or a particle bunch from said radiation device,iii. a controller configured for: a. determining a time difference between a time of detection of a gamma quantum in the gamma detector and a time of emission of the single particle or the particle bunch which has produced the gamma quantum detected,b. making a statistical distribution of time differences MDIS resulting from multiple gamma quanta detections in said detector,c. analyzing said statistical distribution MDIS so as to obtain information about said range of the particle beam. 7. An apparatus according to claim 6 wherein said controller is further configured for c1. acquiring a reference distribution REFDIS said reference distribution REFDIS corresponding to an expected distribution of time differences,c2. comparing said statistical distribution MDIS with said reference distribution REFDIS. 8. An apparatus according to claim 7 wherein comparing the statistical distribution MDIS with the reference distribution REFDIS is performed by a) determining a statistical parameter from said statistical distribution MDIS,b) determining a reference statistical parameter from said reference distribution REFDIS,c) comparing the statistical parameter obtained in step a) with the reference statistical parameter obtained in step b). 9. An apparatus according to claim 7 wherein said detection timing signal and said reference timing signal are provided with an uncertainty in time equal or less than 10 ns. 10. An apparatus according to claim 6 wherein said gamma detector comprises a scintillator detector or a Cherenkov detector or a resistive plate chamber detector. 11. A particle beam system for delivering energetic particles or bunches of energetic particles to a target comprising a particle beam source for delivering energetic particles or bunches of energetic particles;beam directing means for directing the energetic particles or bunches of energetic particles in a beam direction pointing to said target;a timing controller configured for providing a timing reference signal representing a time structure for delivering said energetic particles or bunches of energetic particles;a first gamma detector configured for detecting prompt gammas emitted from said target; characterized in that said particle beam system further comprises a second gamma detector configured for detecting prompt gammas emitted from said target and located with respect to said first detector such that the first and the second detector are detecting prompt gammas emitted from different angles with respect to said beam direction;a data acquisition system for measuring prompt gammas in synchrony with the said timing reference signal so as to obtain a timing profile indicating a number of prompt gammas measured as a function of a time elapsed since the delivery of a particle or a bunch of particles, said first and second detector are coupled to said data acquisition system so as to acquire a first timing profile from the first detector and to acquire a second timing profile from the second detector;a data analyser comprising an algorithm configured for a. determining from said first timing profile a first time width DT1;b. determining from said second timing profile a second time width DT2;c. determining a photon travel shift DDP defined as a distance traveled by a photon in the time interval equal to the difference between the first and the second time width: DDP=(DT2−DT1)*c whereby c is equal to the speed of light;d. determining a particle beam penetration depth by correlating said photon travel shift DDP with the difference in detector location between the first and second detector. 12. A particle beam system according to claim 11 wherein said data analyser comprises computing means configured for calculating a distance R in the target by solving the equation DDP=(R*R+d1*d1-2*R*d1*cos(α)-(R*R+d2*d2-2*R*d2*cos(β)-(d1-d2)wherebyDDP is the said photon travel shift;d1 is the distance from the first detector to the entrance point, the entrance point being defined as the point where the energetic particles or bunches of energetic particles enter the target;d2 is the distance from the second detector to the entrance point;α is the angle between the beam direction and the direction going from the entrance point towards the first detector;β is the angle between the beam direction and the direction going from the entrance point towards the second detector. 13. A particle beam system according to claim 11 wherein said second gamma detector is located with respect to said first gamma detector such that the first and the second gamma detector are detecting prompt gammas emitted at angles with respect to the beam direction that differ by at least 20°. 14. A particle beam system according to claim 11 wherein said first gamma detector is located for measuring prompt gammas emitted at an angle equal or larger than 100° with respect to the beam direction and said second gamma detector is located for measuring prompt gammas emitted at an angle equal or smaller than 80° with respect to the beam direction. 15. A particle beam system according to claim 11 wherein said data acquisition system is configured to measure said timing profiles with a resolution equal or smaller than ten nanoseconds. 16. A particle beam system according to claim 11 wherein said particle beam source is comprising a particle accelerator for delivering protons or ions having an energy larger than 40 MeV per mass unit. 17. A method for verifying a penetration depth of an energetic particle beam in a target by detecting prompt gammas produced when said energetic particle beam penetrates said target, the method comprising the steps of providing a first gamma detector configured for detecting prompt gammas;providing a second gamma detector configured for detecting prompt gammas;locating said first and second detector in a different location with respect to the target such that the first and the second detector are configured for detecting prompt gammas emitted at different angles with respect a direction of the energetic particle beam;providing a timing reference signal representing a time structure of the energetic particle beam;measuring prompt gammas emitted from the target with said first detector in synchrony with said timing reference signal so as to obtain a first timing profile;measuring prompt gammas emitted from the target with said second detector in synchrony with said timing reference signal so as to obtain a second timing profile;determining from said first timing profile a first time width DT1;determining from said second timing profile a second time width DT2;determining a photon travel shift DDP defined as a distance traveled by a photon in the time interval equal to the difference between the first and the second time width: DDP=(DT2−DT1)*c whereby c is equal to the speed of light;determining said penetration depth by correlating said photon travel shift DDP with the difference in detector location between the first and second detector. 18. A method according to claim 17 whereby the step of determining said penetration depth comprises a step of calculating a distance R in the target by solving the equation DDP=(R*R+d1*d1-2*R*d1*cos(α)-(R*R+d2*d2-2*R*d2*cos(β)-(d1-d2)wherebyDDP is the said photon travel shiftd1 is the distance from the first detector to the entrance point, the entrance point being defined as the point where the energetic particle beam enters the target;d2 is the distance from the second detector to the entrance point;α is the angle between the beam direction and the direction going from the entrance point towards the first detector;β is the angle between the beam direction and the direction going from the entrance point towards the second detector. 19. A method according to claim 17 wherein said second gamma detector is located with respect to said first detector such that the first and the second detector are detecting prompt gammas emitted at angles with respect to the beam direction that differ by at least 20°. 20. A method according to claim 17 wherein said first gamma detector is located for measuring prompt gammas emitted at an angle equal or larger than 100° with respect to the beam direction and said second gamma detector is located for measuring prompt gammas emitted at an angle equal or smaller than 80° with respect to the beam direction.
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Zwart, Gerrit Townsend; Jones, Mark R.; Cooley, James, Collimator and energy degrader.
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