Development and evaluation of a multichannel endorectal RF coil for prostate MRI at 7T in combination with an external surface array

• Published in: Journal of magnetic resonance imaging Vol. 43; no. 6; pp. 1279 - 1287
• Main Authors: Ertürk, M. Arcan, Tian, Jinfeng, Van de Moortele, Pierre-François, Adriany, Gregor, Metzger, Gregory J.
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01-06-2016; Wiley Subscription Services, Inc
• Subjects: 7 Tesla body imaging; Computer-Aided Design; endorectal coil; Equipment Design; Equipment Failure Analysis; Humans; Image Enhancement - instrumentation; Magnetic resonance imaging; Magnetic Resonance Imaging - instrumentation; Magnetics - instrumentation; Male; MRI; Phantoms, Imaging; prostate; prostate cancer; Prostatic Neoplasms - diagnostic imaging; Prostatic Neoplasms - pathology; Reproducibility of Results; Sensitivity and Specificity; Transducers; ultrahigh field; endorectal coil; 7 Tesla body imaging; prostate cancer; prostate; MRI; ultrahigh field
• ISSN: 1053-1807; 1522-2586
• DOI: 10.1002/jmri.25099

Purpose
To develop and evaluate a sterilizable multichannel endorectal coil (ERC) for use in combination with an external surface array (ESA) for high‐resolution anatomical and functional studies of the prostate at 7T.
Materials and Methods
A two‐loop ERC (ERC‐2L) and a microstrip‐loop ERC (ERC‐ML) were compared at 7T in terms of transmit and receive performance. The best‐performing ERC was evaluated alone and in combination with the ESA through 1) simulations on both phantom and an anatomically correct numerical human model to assess
B1+ transmit and specific absorption rate (SAR) efficiencies, and 2) phantom experiments to calculate
B1+ transmit efficiency and signal‐to‐noise ratio (SNR). Phantom studies were also performed to look at heating when using the ERC as a transmitter and for comparing the new coil against a single‐channel balloon‐type ERC (ERC‐b). High‐resolution magnetic resonance imaging (MRI) acquisitions were performed on a single healthy subject using the two‐channel ERC combined with the ESA.
Results
Compared to the ERC‐ML, the ERC‐2L demonstrated 20% higher SAR efficiency and higher SNR 3 cm from the coil. The presence of a tuned and detuned ERC‐2L did not alter the peak local SAR of the ESA alone; however, the detuned ERC‐2L had 45% less peak local SAR around the rectum compared to the tuned ERC‐2L. The receive‐only version of the ERC‐2L improved the SNR 4.7‐fold and 1.3‐fold compared to the ESA and ERC‐b, respectively. In combination with the ESA, the ERC‐2L supported in‐plane voxel‐size of 0.36 × 0.36 mm2 in T2‐weighted anatomic imaging.
Conclusion
The reusable ERC‐2L combined with an ESA offers a high SNR imaging platform for translational studies of the prostate at 7T. J. Magn. Reson. Imaging 2016;43:1279–1287.