Method and apparatus for monitoring the range of a particle beam

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.

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 travelled 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.

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 travelled 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.