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

Lee, Brian J.; Watkins, Ronald D.; Lee, Keum Sil; Chang, Chen‐Ming; Levin, Craig S.

doi:10.1002/mrm.27444

Cited by 21 publications

(21 citation statements)

References 37 publications

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“…This RX coil inside the PET insert will slightly attenuate the detected PET annihilation photon flux; however, with careful PET-compatible design using low-density materials in the PET FOV, the impact on PET performance should be negligible [16], [34], [35]. This custom multi-channel RX coil is the subject of another study [36, 16].…”

Section: Discussionmentioning

confidence: 99%

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

Lee

Grant

Chang

et al. 2018

IEEE Trans. Med. Imaging

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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.

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Section: Discussionmentioning

confidence: 99%

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

Lee

Grant

Chang

et al. 2018

IEEE Trans. Med. Imaging

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“…MR image quality will also be improved using a dedicated RF coil within the PET insert . Other PET insert designs to date are not RF‐transmissive so they require a dedicated RF transmit/receive coil residing inside the PET ring.…”

Section: Discussionmentioning

confidence: 99%

“…MR image quality will also be improved using a dedicated RF coil within the PET insert. 41 Other PET insert designs to date 8,40 are not RF-transmissive so they require a dedicated RF transmit/receive coil residing inside the PET ring. However, a dedicated RF receive-only coil placed within the RF-penetrable PET ring allows the MR body coil to be used for RF transmit only.…”

Section: B Simultaneous Pet/mr Imagingmentioning

confidence: 99%

Simultaneous PET/MR imaging with a radio frequency‐penetrable PET insert

et al. 2017

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Purpose A brain sized radio-frequency (RF)-penetrable PET insert has been designed for simultaneous operation with MRI systems. This system takes advantage of electro-optical coupling and battery power to electrically float the PET insert relative to the MRI ground, permitting RF signals to be transmitted through small gaps between the modules that form the PET ring. This design facilitates the use of the built-in body coil for RF transmission, and thus could be inserted into any existing MR site wishing to achieve simultaneous PET/MR imaging. The PET detectors employ non-magnetic silicon photomultipliers in conjunction with a compressed sensing signal multiplexing scheme, and optical fibers to transmit analog PET detector signals out of the MRI room for decoding, processing, and image reconstruction. Methods The PET insert was first constructed and tested in a laboratory benchtop setting, where tomographic images of a custom resolution phantom were successfully acquired. The PET insert was then placed within a 3T body MRI system, and tomographic resolution/contrast phantom images were acquired both with only the B0 field present, and under continuous pulsing from different MR imaging sequences. Results The resulting PET images have comparable contrast-to-noise ratios (CNR) under all MR pulsing conditions: the maximum percent CNR relative difference for each rod type among all four PET images acquired in the MRI system has a mean of 14.0±7.7%. MR images were successfully acquired through the RF-penetrable PET shielding using only the built-in MR body coil, suggesting that simultaneous imaging is possible without significant mutual interference. Conclusions These results show promise for this technology as an alternative to costly integrated PET/MR scanners; a PET insert that is compatible with any existing clinical MRI system could greatly increase the availability, accessibility, and dissemination of PET/MR.

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“…3). More details about the construction of the coil and the comparison of its performance to a custom bird-cage transceiver coil, which is used in most other PET inserts, can be found in our previous work [52].…”

Section: Methodsmentioning

confidence: 99%

Performance Study of a Radio-Frequency Field-Penetrable PET Insert for Simultaneous PET/MRI

Chang

Lee

Grant

et al. 2018

IEEE Trans. Radiat. Plasma Med. Sci.

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Hybrid positron emission tomography (PET)/magnetic resonance imaging (MRI) has risen to the cutting edge of medical imaging technology as it allows simultaneous acquisition of structural, functional and molecular information of the patient. A PET insert that can be installed into existing MR systems can in principle reduce the cost barriers for an existing MR site to achieve simultaneous PET/MRI compared to procuring an integrated PET+MRI system. The PET insert systems developed so far for PET/MRI require the RF transmitter coil to reside inside the PET ring as those PET inserts block the RF fields from the MRI system. Here we report for the first time on the performance of a full-ring brain-sized “RF-penetrable” PET insert we have recently completed. This insert allows the RF fields generated by the built-in body coil to penetrate the PET ring. The PET insert comprises a ring of 16 detector modules employing electro-optical coupled signal transmission and a multiplexing framework based on compressed sensing. Energy resolution, coincidence timing resolution (CTR), photopeak position, and coincidence count rate were acquired outside and inside a 3-Tesla MRI system under simultaneous acquisition to evaluate the impact of MRI on the PET performance. Coincidence count rate performance was evaluated by acquiring a cylinder source with high initial activity decaying over time. Tomographic imaging of two phantoms, a custom 6.5-cm diameter resolution phantom with hot rods of four different sizes (2.8 mm, 3.2 mm, 4.2 mm, and 5.2 mm diameter) and a 3D Hoffman brain phantom, were performed to evaluate the imaging capability of the PET insert. The energy resolution at 511 keV and CTR acquired by the PET insert were 16.2±0.1% and 5.3±0.1 ns FWHM, respectively, and remained stable during MRI operation except when the EPI sequence was applied. The PET system starts to show saturation in coincidence count rate at 2.76 million photon counts per second. Most of the 2.8-mm diameter hot rods and main features of the 3D Hoffman brain phantom were resolved by the PET insert, demonstrating its high spatial resolution and capability to image a complex tracer distribution mimicking that seen in the human brain.

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

Abstract: RF coil configurations for an RF-penetrable PET insert for simultaneous PET/MRI were studied. The RX-only phased-array coil (TX from body coil) outperformed the TX/RX birdcage coil with improved MR performance as well as negligible PET photon attenuation.

Cited by 21 publications

References 37 publications

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

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

Simultaneous PET/MR imaging with a radio frequency‐penetrable PET insert

Performance Study of a Radio-Frequency Field-Penetrable PET Insert for Simultaneous PET/MRI

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