A 28-Channel Coil Array for Improved Imaging of the Optic Nerve ROBB P. MERRILL, 1 J. ROCK HADLEY, 1 EMILEE MINALGA, 1 EUGENE G. KHOLMOVSKI, 1 SATHYA VIJAYAKUMAR, 1 SEONG-EUN KIM, 1 EDWARD P. QUIGLEY, 1 DENNIS L. PARKER, 1 JOHN W. ROSE 2 1 Department of Radiology, University of Utah, Salt Lake City, Utah 84108 2 Chief of Neurology, VA Hospital, Salt Lake City, Utah 84108 ABSTRACT: This work describes the design and construction of a radio-frequency (RF) coil optimized for imaging the optic nerve on a Siemens 3T TIM Trio MRI scanner. The specific goals were to optimize signal sensitivity from the orbit to the optic chiasm and improve SNR over previous designs. The optic nerve (ON) coil was constructed using two fiberglass formers that fit together in a clamshell arrangement to maintain a high filling factor for any head size. This design maintains close coil-to-sample coupling near the eyes and around the entire head to eliminate the air void regions that occur between coil and sample when heads are imaged in one-piece rigid head coils. The anterior mask former holds 26 overlapping coil elements in a soccer ball layout. The posterior former supports the neck and head and houses two additional overlapped coil elements, totaling to 28 elements. Signal-to-noise-ratio (SNR) measurements on a custom-made homogeneous head phantom using the optic nerve coil showed a 310% increase in SNR near the orbits and 60% increase at the optic chiasm compared to the 12-channel Siemens head coil. Inverse g-factor maps show that the ON coil performs well for parallel imaging over the region of the optic nerve, providing a possible reduction of eyeball motion artifacts. Images from volunteer studies demonstrate that high-resolution imaging of the optic nerve can be achieved using 3T MRI with advanced imaging coils, leading to improved patient care for optic neuritis patients. Ó 2012 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 41B: 73–84, 2012 INTRODUCTION Optic neuritis is characterized by inflammation of the optic nerve (ON), leading to eye movement pain, reduced color perception, poor pupillary response, and mild to severe visual impairment. Optic neuritis occurs in 50% of multiple sclerosis (MS) patients and may be a presenting symptom of the disease (1, 2). Data from clinical trials demonstrate a significant reduction in the risk of developing MS if demyelinat- ing lesions are detected early enough, and therapy is initiated (3). Consequently, there is great motivation among researchers and radiologists to produce images of the ON with higher resolution, and with greater coverage of the optic pathway, from which to form more accurate diagnoses (1). Nearly every magnetic resonance imaging (MRI) study of the ON has reported difficulties (1, 4, 5–7). The nerve structure is very small (4–6 mm diameter), highly mobile, and embedded deeply within the cra- nium. Motion artifacts often make the nerve difficult Received 27 January 2012; revised 5 April 2012; accepted 25 April 2012 Subject matter presented in e-poster format at the 17th Scientific Meeting & Exhibition of ISMRM (2009). Correspondence to: Robb P. Merrill; E-mail: rmerrill@ucair.med. utah.edu Concepts in Magnetic Resonance Part B (Magnetic Resonance Engineering), Vol. 41B(3) 73–84 (2012) Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/cmr.b.21216 Ó 2012 Wiley Periodicals, Inc. 73