Safety dose interlock for charged particle beams

An assembly for preventing an overdose of a charged particle beam during therapy to a patient, comprising:

• a detector comprising detector elements that form a plurality of pixels, the detector apparatus configured to output, for each said pixel, a local measured current corresponding to a local measured intensity of said particle beam at said pixel;
• a controller in communication with said particle beam generator and said detector apparatus, said controller comprising, for each said pixel:
• a current integrator circuit that converts said local measured current into a total local detected charge integrated from a start time, the integrator circuit outputting an integrator voltage that corresponds to said total local detected charge;
• and
• a first discriminator circuit that compares the integrator voltage with a first reference voltage corresponding to a first maximum acceptable dose for said patient;
• a programmable reference voltage source that outputs a programmable reference voltage corresponding to a second maximum acceptable dose for said patient;
• and
• a second discriminator circuit that compares the integrator voltage with the programmable reference voltage;
• a logic circuit that generates an overdose fault signal if, at any of said pixels, said integrator voltage is higher than the first reference voltage or the programmable reference voltage.

A method of preventing an overdose of a charged particle beam during therapy to a patient, the method comprising:

• passing the charged particle pencil beam through a pixelated ion detector chamber comprising detector elements that form a plurality of pixels;
• for each said pixel,
• receiving a local measured current collected at said pixel;
• passing said local measured current through a current integrator circuit that converts said local measured current into an integrator voltage that corresponds to a total local detected charge integrated from a start time;
• comparing the integrator voltage with a reference voltage that corresponds to a maximum acceptable dose for said patient;
• and
• stopping the therapy if the integrator voltage is greater than the reference voltage.