RAD2012, Nis, Serbia Positron Detector for radiochemistry on chip applications R. Duane, N. Vasović, P. LeCoz, N. Pavlov 1, C. Jackson 1, A. Jakšić 1) Sensl technologies (

OUTLINE Radiochemistry On Chip (ROC) European Project –Production of radiotracers for Positron Emission Tomography (PET) analysis Silicon Photomultiplier Technology Miniature Radiation Probes Summary

Positron Emission Tomography Injection of positron emitting radiotracer (e.g. F-18 combination with glucose biomarker = FDG)

Commercial production of Radiotracers Cyclotron to produce the radioactive isotope (e.g. F-18, C-11) Hot-cells to combine radioisotopes with biomarker such as glucose analog + = Fludeoxyglucouse (FDG)

Radiochemistry on Chip (ROC) Motivation Technical Goal: Microfluidic synthesis platform Motivation: On-site production of PET radiotracers

Microfluidic Synthesis Platform RadioTracer Waste Lines

Radiation Detection Objectives Flow Probe Waste Probe Track movement of FDG radioactivity in 1m 3 Lead Box –High concentrations of positron and annihilation gammas (1Tbq total F18 activity) Shielded probes to quantify activity in waste and flow shielded chambers Unshielded positron probe to track small changes in positron activity in microfluidic chips as “process monitor” microreactor Positron Probe

Shielded probe requirements/design 1.Activity: 3.7kBq/100uL (waste) to 740Mbq/uL (flow) 2.Size: approx 1-2cm 3 (due to microfluidic chip sizes) Scintillator based detector 3.Magnetic Field Immunity due to proximity to mini-cyclotron Semiconductor (Silicon) based photodetector 4.Count linearity and stability (<5%) Gamma scintillation detector 5.Long cabling (5m) High gain photodetector

Scintillator and Photodetector Operation Scintillation Crystal Photodetector With amplification High Energy Gamma 1) Conversion to lower energy visible photons 2) Detection and amplification of visible photons

Silicon Photodetector types Silicon PN photodiode (Gain=1) Silicon Avalanche photodiode ( Gain=100 ) Geiger Mode photodetector (Gain>10 6 )

Sensl Silicon Photomultiplier Sensl Silicon Photomultiplier (SPM) Silicon Photomultiplier (SPM) = Array of Geiger Mode photodiodes -3,640 35um geiger mode diodes per 3mm die -Replaces PhotoMultiplier Tube (PMT) Low voltage 30V operation Direct gamma hits are not an issue due to device design Expect good count linearity for gamma detector Large signal to noise ratio results in simpler electronics and longer cabling

Sensl Silicon Photomultiplier Probes Inorganic Scintillator SPM

CSI (TI) Probe Results CSI (TI) chosen as best spectral match (550nm) to SPM peak light absorption (520nm) Peak Resolution 8.7% Cs137, 10.5% Ge68 511kev 667kev

CSI(TI) Probe Results Distinguish minimum waste activity (1.5kBq) in lab environment at room temperature Stability of 4.7% (139kBq) over 12 hour measurement (1s integration time) — Meets 5% specification for flow probe —Expect better stability for 740MBq flow activities Background Minimum Waste

CSI(TI) Probe Linearity Good linearity for low waste activities(1.5kBq-139kBq) using peak counting Peak Sensitivity = 30counts/second/kBq (at 6mm distance from disc source)

CSI (TI) Flow Probe Saturation of measured counts (Peak counting) –CSI(TI) scintillator 1  s pulse and associated 3  s shaping time

LSO Flow Probe LSO scintillator (3mm) investigated for flow probe Faster gamma response (40ns) Poorer spectral matching (440nm peak photon emission) 10s integration time

LSO Flow Probe Good fit to 1Gbq F-18 decay over 20 hours (Total counting) 5 second integration time min F-18 half-life

SUMMARY Silicon Photomultiplier based probes for radiochemistry –CSI(TI) +SPM waste probe –LSO + SPM flow probe Preliminary results show good count linearity and stability Temperature compensation circuitry for SPM gain in development Welcome collaborators with access to high activity positron sources –Stability, Linearity as a function of temperature –Radiation Hardness

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