Bismuth Organic Liquid Detector with Cherenkov Light and Charge Readout for Positron Emission Tomography

Basic data for this project

Description

The aim of the BOLD-PET project is to develop a fast-response, high-efficiency gamma detector with fine grained spatialresolution for positron emission tomography (PET) based on recent developments using the liquid TriMethyl Bismuth (TMBi).This liquid with a bismuth mass fraction of more than 80% allows for a very efficient and accurate detection of 511 keV photonsoriginated from positron annihilation. Bismuth has the highest nuclear charge (Z = 83) and thus the largest photoelectriccross section of all stable isotopes. The gamma energy of 511 keV is transferred to electrons in this material in nearly50 % of the cases through the photoelectric effect. Both the Cherenkov light emitted by the resulting relativistic photoelectronand the secondary charge carriers produced during multiple scattering interactions are detected in a liquid ionisationchamber, supplemented by photodetectors. Based on previous studies of liquid TMBi, we intend to develop and evaluatea novel PET detector with simultaneous detection of Cherenkov light and ionisation in a common effort of four researchpartners. Excellent imaging resolution is anticipated with the proposed detector by cancelling out Depth Of Interaction effectswhile allowing for placement of the detector close to the body which is increasing the detector’s solid angle. The TMBi’scoincidence photoelectric efficiency is the highest available, with twice the value of LSO/LYSO crystals. The new detectorshould be able to use accurate time-of-flight (TOF) information through Cherenkov light detection in order to improve thecontrast of the reconstructed image. To achieve a breakthrough in this challenging project, the expertise of the existing FrenchCaLIPSO group (CEA-IRFU, CNRS-LAL) will be supplemented by the expertise on high-resolution PET imaging and detectordevelopment (WWU-EIMI group), and ultra-purification as well as light and charge detector readout (WWU-PHYSICS group),both from University of M¨unster. The main objective of this collaborative project is to develop a novel detector system for PETimaging (e.g. human brain PET, small animal PET) with a projected efficiency of 30%, high spatial precision of 1 mm3, andhigh time of flight resolution of 100 ps (FWHM). In order to achieve these objectives the project will focus on the followingwork areas: (1) ultra-purification of TMBi and further characterisation of TMBi for gamma radiation detection, (2) developmentof an ionisation detector prototype, (3) study of the Cherenkov photon detection in liquid TMBi, (4) Monte Carlo simulationand image reconstruction of a full PET scanner employing the new technology, and (5) evaluation of a final PET detectiondemonstrator, merging charge and optical readout.