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Part 1: Dual-Tuned Proton/Sodium Magnetic Resonance Imaging of the Lumbar Spine in a Rabbit Model

Moon, Chan Hong, PhD*; Kim, Jung-Hwan, BS*; Jacobs, Lloydine, MD; Zhao, Tiejun, PhD; Sowa, Gwendolyn, MD, PhD†,§; Vo, Nam, PhD; Kang, James, MD; Bae, Kyongtae Ty, MD, PhD*

doi: 10.1097/BRS.0b013e318259ee98
Basic Science
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Study Design. Development of a dual-tuned proton/sodium radiofrequency (RF) coil for magnetic resonance imaging (MRI) of the rabbit spine and quantification of sodium concentration in intervertebral discs.

Objective. To develop the dual-tuned proton/sodium MRI of rabbit lumbar spine to investigate proteoglycan matrix content and intervertebral disc degeneration (IDD).

Summary of Background Data. IDD is a common chronic condition that may lead to back pain, limited activity, and disability. Early-stage IDD involves the loss of proteoglycan matrix and water content in the disc. Sodium MRI is a promising noninvasive technique for quantitative measurement of proteoglycan changes associated with IDD. The combined structural (proton) and biochemical (sodium) MRI facilitates the investigation of morphological and molecular changes associated with degeneration of discs.

Methods. Multichannel dual-tuned proton/sodium transceiver RF coil of the rabbit spine was developed and optimized at 3T human scanner—8 channels allocated for the sodium coil and 4 channels for the proton coil. High-resolution anatomy proton images of the discs were acquired using turbo spin echo and dual echo steady state sequence. Sodium concentration of the discs was quantified from sodium magnetic resonance (MR) images that were calibrated for signal attenuation because of RF field inhomogeneity, sodium MR relaxation times, and disc thickness. Twelve rabbits (∼1-yr old, female, 5.2 ± 0.4 kg) were used for measuring disc sodium concentration.

Results. High-resolution in vivo proton and sodium MR images of rabbit discs (≤2-mm thickness) were successfully obtained using an in-house dual-tuned proton/sodium RF coil at 3T. The total acquisition time for each set of images was approximately 40 minutes. Sodium concentration of normal rabbit lumbar discs was measured at 269.7 ± 6.3 mM, and this measurement was highly reproducible, with 5.3% of coefficient of variation.

Conclusion. Sodium concentrations of rabbit lumbar discs were reliably measured using our newly developed dual-tuned multichannel proton/sodium RF coil at 3T.

Combined dual-tuned proton/sodium magnetic resonance imaging of the rabbit lumbar discs and the quantification of sodium concentration in the discs were achieved using a multichannel dual-tuned radiofrequency coil in the 3T human scanner.

*Departments of Radiology, University of Pittsburgh, Pittsburgh, PA

Ferguson Laboratory for Orthopaedic and Spine Research, Department of Orthopaedic Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA

MR Research Support, Siemens Healthcare, Pittsburgh, PA

§Department of Physical Medicine and Rehabilitation, University of Pittsburgh, Pittsburgh, PA.

Address correspondence and reprint requests to Kyongtae Ty Bae, MD, PhD, Department of Radiology, University of Pittsburgh School of Medicine, 200 Lothrop St., Pittsburgh, PA 15213; E-mail: baek@upmc.edu

Acknowledgment date: November 4, 2011. First revision date: February 20, 2012. Acceptance date: April 7, 2012.

The device(s)/drug(s) that is/are the subject of this manuscript is/are not intended for human use.

Radiological Society of North America (RSNA) Research Scholar and NIH/NCCAM grant funds were received to support this work.

One or more of the author(s) has/have received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this manuscript: e.g., honoraria, gifts, consultancies, royalties, stocks, stock options, decision-making position.

© 2012 Lippincott Williams & Wilkins, Inc.