Wide-Range Neutron Counting for Yield Prediction of PET Agents in Cyclotron Irradiations

As PET is moving into the clinical setting, the instrumentation from yesterday's research laboratory is being pressed into routine use in a setting which is intolerant of any unreliability. At the University of Wisconsin, a system of three neutron detectors has been developed to asses the progress of target irradiations in real time. The triad of detectors consists of an NE213 liquid scintillator, a 238U fission detector, and a proton recoil telescope to be able to detect neutron fluence rates over a span of six decades. The signals from these detectors are the inputs to a leaky integrator which calculates the build up of activity in the target. In this way, the cyclotron operator can easily monitor the irradiation and take immediate action, if required, as opposed to finding an empty target at the end of bombardment and falling hopelessly behind schedule. The ability to accurately predict target yields by wide-range neutron counting adds a measure of reliability to radiopharmaceutical production and will facilitate PET becoming a routine clinical tool.