High-resolution MR imaging of the human eye 2005.
OBJECTIVE
We studied preparatory strategies for high-resolution human eye in vivo imaging with commercially available magnets and coils.


METHODS
We imaged normal volunteers on 1.5T systems by Philips, GE, and Siemens, using commercial approximately 9 cm temporomandibular joint receive coils. Subjects fixated the nonimaged eye on a target. We compared signal (S) to tissue noise (Nt) and system noise (Ns) between images acquired with the imaged eye: 1) open, 2) held closed, 3) taped closed, and 4) taped closed with overlying water-soaked gauze. We standardized technique 4 to compare studies between manufacturers using T1-weighted parameters (repetition time/echo time/flip angle/number of signal averages = 400 ms/10-17 ms/90 degrees /4-6, in-plane resolution approximately 250 x 250 microm2; 2-3 mm slices, image time = 4.3-5.2 min). We obtained similar images of an enucleated human eye to estimate in vivo effects of microsaccades and ocular pulsations.


RESULTS
Measurements of S/Nt and S/Ns gave surprising results of Nt < Ns in some instances. Ns/Nt was congruent with 1, varying approximately 20%, when the eye was taped shut and covered with water-soaked gauze. T1-weighted spin echo sequences, using technique 4, produced high-quality images with good S/Nt on all systems. Images from the three manufacturers were comparable when parameters were normalized for pulse repetition time, echo time, number of signal averages, bandwidth in Hz/pixel, and reconstruction matrix. Images of the enucleated eye produced S/Nt ratios that were comparable to in vivo images in some structures.


CONCLUSIONS
Our best preparatory technique produced images with in-plane resolution of approximately 250 mum in 4-5 minutes with three commercial 1.5 T systems. The in vivo S/Nt was comparable to in vitro values in most solid tissues but decreased in most fluid compartments.
University of Colorado, Health Sciences Center, Radiology, 4200 E. Ninth Avenue, A034, Denver, CO 80262, USA. robert.bert@uchsc.edu
Robert J
RJ
Bert
Samuel
S
Patz
Mohamed
M
Ossiani
Shelton D
SD
Caruthers
Hernan
H
Jara
Jaroslaw
J
Krejza
Thomas
T
Freddo
D005123:Eye / Q000033:anatomy & histology*; D006801:Humans; D066298:In Vitro Techniques; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*