MR Performance in the Presence of a Radio Frequency-Penetrable Positron Emission Tomography (PET) Insert for Simultaneous PET/MRI

Abstract

Despite the great promise of integrated positron emission tomography (PET)/magnetic resonance (MR) imaging to add molecular information to anatomical and functional MR, its potential impact in medicine is diminished by a very high cost, limiting its dissemination. An RF-penetrable PET ring that can be inserted into any existing MR system has been developed to address this issue. Employing optical signal transmission along with battery power enables the PET ring insert to electrically float with respect to the MR system. Then, inter-modular gaps of the PET ring allow the RF transmit field from the standard built-in body coil to penetrate into the PET fields-of-view (FOV) with some attenuation that can be compensated for. MR performance, including RF noise, magnetic susceptibility, RF penetrability through and $B_{1}$ uniformity within the PET insert, and MR image quality, were analyzed with and without the PET ring present. The simulated and experimentally measured RF field attenuation factors with the PET ring present were -2.7 and -3.2 dB, respectively. The magnetic susceptibility effect (0.063 ppm) and noise emitted from the PET ring in the MR receive channel were insignificant. $B_{1}$ homogeneity of a spherical agar phantom within the PET ring FOV dropped by 8.4% and MR image SNR was reduced by 3.5 and 4.3 dB with the PET present for gradient-recalled echo and fast-spin echo, respectively. This paper demonstrates, for the first time, an RF-penetrable PET insert comprising a full ring of operating detectors that achieves simultaneous PET/MR using the standard built-in body coil as the RF transmitter.

3D Auto-Context-Based Locality Adaptive Multi-Modality GANs for PET Synthesis

“…Modern PET scans are usually accompanied with other modalities, such as computed tomography (CT) and magnetic resonance image (MRI). By combining functional and morphological information, PET/CT and PET/MRI systems could increase diagnostic accuracy in a variety of malignancies [3–5]. Previous research also indicates the benefit brought by multi-modality data for medical image quality enhancement [6, 7].…”

Performance evaluation of RF coils integrated with an RF‐penetrable PET insert for simultaneous PET/MRI

“…Although EPI sequence is a common sequence for brain imaging, it was not performed in the study. As presented from earlier publications, 10,28,29 the intense gradient field slew rate of EPI sequence induced eddy current on the solid copper shielding cage of the RF-penetrable PET insert and suffered from the Nyquist ghosting artifact. To allow the PET ring operable with EPI, various designs and materials for the shielding cage with sufficiently high shielding effectiveness and low induced eddy current have been investigated.…”

“…In our previous work describing an RF‐penetrable PET insert, we used the body coil as both TX/RX for purposes of studying “RF penetrability”, and have demonstrated that the RF field could be both transmitted and received through the PET ring with ~ 3.5 dB attenuation for both directions. We also showed that this configuration allows a uniform B 1 field inside the useful PET FOV.…”

Evaluation of the radiofrequency performance of a wide-bore 1.5 T positron emission tomography/magnetic resonance imaging body coil for radiotherapy planning

“…Previous simultaneous PET/MRI designs were typically based on the concept of adding PET scintillation crystals and readout electronics to an existing MRI system [6] , either in the form of a removable PET insert (e.g. for small-animal [7] , [8] , [9] or brain [10] , [11] , [12] ), or integrated between the gradient coil and the RF body coil (e.g. [13] , [14] ).…”