Apparatus for particle therapy verification comprising a collimator with multiple openings

A method for charged hadron therapy verification by detecting prompt gammas produced when irradiating a target with a charged hadron beam, the beam being directed along a beam line, wherein the prompt gammas are detected with an apparatus comprising:

• a collimator comprising a plurality of collimator slabs of thickness (t), the collimator slabs being spaced apart to form an array of slit-shaped openings and placed at an essentially right angle to the beam line to allow the passage of prompt gamma emission from the target, the collimator being defined at least by three geometrical parameters being:
• the width (s) of the slit-shaped openings;
• the depth (D) of the slit-shaped openings;
• and
• the fill factor (f), with f equal to t/(t+s);
• and
• a detection device configured for detecting the prompt gammas emission, the detection device comprising at least a portion of scintillator material aligned with each of the slit-shaped openings;
• wherein the width s of the openings, the depth D of the openings and the fill factor f are chosen such that:
• s is 2 mm or higher;
• D is between 50 mm and 200 mm;
• f is lower than or equal to 0.7;
• and
• a Time of Flight (TOF) discrimination is applied to the detection of the prompt gammas, and wherein J>1%, with J defined as
• S
• ·
• A
• A
• TOF
• and wherein:
• S=spatial acceptance=1−f=s/(s+t);
• A=angular acceptance=slit width/collimator depth (s/D);
• and
• ATOF=TOF acceptance=the ratio of neutron background emission that is conserved after application of the TOF discrimination, to the total neutron background emission, with ATOF=1 when no TOF discrimination is applied.