Development of a high-resolution, MRI-compatible PET detector using digital silicon photomultipliers

Abstract

The simultaneous integration of positron emission tomography (PET) and magnetic resonance imaging (MRI) promises to combine superior functional and anatomical information into a single examination, but poses a number of engineering challenges. In particular, the development of MRI-compatible photodetectors is a key issue to realize PET/MRI at its best.

In 2009, a novel photodetector, the so-called digital SiPM, was presented. The digital SiPM combines an array of Geiger-mode photodiodes with a direct digital readout and timestamper on a single silicon die. Its high integration and expected immunity to magnetic fields makes the digital SiPM very promising for simultaneous PET/MRI. Related to the development of the world’s first digital SiPM based simultaneous PET/MRI system, this thesis focuses on three specific engineering aspects of simultaneous PET/MRI.

First, an MRI-compatible photodetector stack based on digital SiPMs has been developed, investigated and optimized. The final design is virtually immune to the MRI environment and enables the full potential of the digital SiPM to be used for simultaneous PET/MRI, including its time-of-flight capabilities. No evidence was found that the digital SiPM itself is affected by the MRI environment.

Second, based on carbon fibre composites, a novel modular radio frequency (RF) shielding concept for MRI-compatible PET detectors has been developed. In contrast to common copper based shields, carbon fibre composites are less susceptible to eddy currents because of their lower sheet conductance. It is shown, experimentally and analytically, that carbon fibre composites can provide higher RF shielding efficiency to sheet conductance ratios than conventional copper shields can do, which makes them beneficial for simultaneous PET/MRI.

Third, experimental and simulation approaches for the optical design of pixelated scintillation detectors have been assessed, in particular to improve the depth-of-interaction encoding of pixelated scintillation detectors. A novel pixelated scintillator configuration is proposed, which avoids the use of inter-crystal reflectors.

Date of Award	2016
Original language	English
Awarding Institution	King's College London
Supervisor	Paul Marsden (Supervisor) & Volkmar Schulz (Supervisor)