A parallel, transputer-based data acquisition system for on-line PET imaging of proton and gamma-ray radiotherapy beams

We have designed and built a modified positron emission tomography (PET) imaging system for monitoring the dose delivered by proton and γ ray radiotherapy beams. By measuring the amount and ratio of the beam induced positron emitting activity, the dose distribution and tissue composition may be determined. The system utilizes fast LeCroy ECLine electronics and a VME multinode transputer based frontend. Utilizing a transputer based filter, positron annihilation events containing timing, energy, and position information will be filtered in real time at event rates of up to 40 kHz. This will result in only valid events being transmitted back to the host for further analysis and display, reducing both storage media requirements and image reconstruction time. At these rates, proton radiotherapy beams may be monitored between beam pulses for online range verification. It will also be possible to perform bloodflow studies on tumors using the activity induced by a γ-ray radiotherapy beam. Future electronic developments will allow event rates up to roughly 80 kHz. For both treatment modalities, determination of the composition of tumors will directly affect treatment planning through compensation for oxygen enhancement effects to the dose