Novel carbon nanotube-composite for electromagnetic shielding of radiation detectors: A step toward fully integrated positron emission tomography and magnetic resonance imaging systems

Abstract

Carbon nanotubes (CNT) have shown promising properties, as a filler, for increasing the electrical conductivity of composites entering in the fabrication of high-frequency shielding materials. However, up to now, their features at low-frequency range have received little attention. In this study, composite layers based on pristine CNT and polydimethylsiloxane (PDMS) have been synthesized. Both multi-wall and single-wall CNTs were investigated to determine the specific electrical properties of the composite for eliminating the impact of low-frequency electromagnetic interferences in positron emission tomography/magnetic resonance imaging (PET/MRI) scanners. The CNT dispersibility was studied in various solvents. To fabricate a homogeneous composite, a hybrid method based on ultra-sonication and shear mixing of CNT mixtures was developed. The impedance measurements on thin layers confirmed that a well-processed composite provides the required conductivity (>103 S/cm) for electromagnetic interference shielding in the desired frequency range. Such composite layers achieved a shielding effectiveness of >68 dB in the MRI gradient range (10–100 kHz), and exceeded 80 dB in the MRI RF range (50–500 MHz). The results demonstrated that using these CNT-composite shielding layers, the artifacts due to the electromagnetic interferences of gradient and RF coils in the MRI environment can be avoided for PET imaging.