Characterization of scintillating fibers for use as positron detector in positron emission tomography

Manual and automatic blood sampling at different time intervals is considered the gold standard to determine the arterial input function (AIF) in dynamic positron emission tomography (PET). However, blood sampling is characterized by poor time resolution and is an invasive procedure. The aim of this study was to characterize the scintillating fibers used to develop a non-invasive positron detector.

The detector consists of a scintillating fiber coupled at each end to transmission fiber-optic cables that are connected to photo multiplier tubes in a dual readout setup. The detector is designed to be wrapped around the wrist of the patient undergoing dynamic PET. The attenuation length and bending losses were measured with excitation from gamma radiation (¹³⁷Cs) and ultraviolet (UV) light. The response to positron-emitting radio-tracers was evaluated with ¹⁸F and ¹¹C.

The attenuation length for a 3.0 m and 1.5 m long scintillating fiber both coincides with the attenuation length given by the manufacturer when excited with the ¹³⁷Cs source, but not with the UV source due to the differences in scintillation mechanisms. The bending losses are smaller than the measurement uncertainty for the ¹³⁷Cs source irradiation, and increase when the bending radius decrease for the UV source irradiation. The signal-to-noise ratio for ¹⁸F and ¹¹C solutions are 1.98 and 22.54 respectively. The measured decay constant of ¹¹C agrees with its characteristic value.

The performed measurements in the dual readout configuration suggest that scintillating fibers may be suitable to determine the AIF non-invasively.