0.6 T magnetic resonance imaging of the orbit

Edwards, J R; Hyman, RA; Vacirca, S.J.; Boxer, MA; Packer, Stuart; Kaufman, IH; Stein, HL

doi:10.2214/ajr.144.5.1015

Cited by 22 publications

(6 citation statements)

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“…Using Eq. [4], variations of the RF receiver coil sensitivity over each ROI were obtained. For the posterior chamber, anterior chamber, ciliary body, iris, lens cortex, lens nucleus, extraocular muscle, vitreous humor, chorioretina, and optic nerve, our estimates of ͱNEX are 1%, 5%, 1%, 1%, 1%, 4%, 6%, 16%, 6%, and 7%, respectively.…”

Section: Resultsmentioning

confidence: 99%

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T₁ and T₂ measurements of the fine structures of the in vivo and enucleated human eye

Patz¹,

Bert²,

Frederick³

et al. 2007

Magnetic Resonance Imaging

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Purpose: To measure T 1 and T 2 of the fine structures of the in vivo eye. Materials and Methods:Involuntary saccades make it difficult to obtain artifact-free images. Using a method recently reported (Bert et al, Acad Radiol 2006;12:368 -378), near artifact-free spin-echo images were obtained. Both an isolated enucleated eye and eight human subjects were studied at 1.5T. Spin-echo variable TR/TE data was acquired for T 1 /T 2 determination. Average relaxation times were calculated two ways. First, an arithmetic average over different subjects was computed. Second, all data was normalized using the fitted amplitudes of each data set and pooled to obtain a single least squares fit. BECAUSE OF THE very small size of many structures in the human eye, as well as the difficulty with involuntary patient motion of the eye, high resolution and high signal-to-noise ratio (SNR) MRI of the human eye is technically difficult. There are, however, many reports of ocular MRI in the early literature (1-13). For example, in 1987, Atlas et al (13) retrospectively reviewed their initial experience in 59 patients with MRI of the orbit concluding that there were five specific areas in which MRI ocular imaging provided important information. Imaging at a high field, which was 1.5T in 1987, together with a surface coil and short TR values (600 -800 msec) were very important in increasing SNR so that the acquisition time (using 128 phase encodes) could be kept less than two minutes. For longer values of TR, considerable motion artifacts were observed from both head and eye motion. A number of limitations were noted, including poor specificity. In 1991, Wilms et al (14) reported the results of ocular MRI in 41 patients. Their conclusions were that MRI was superior to computed tomography (CT) in depicting ocular lesions because of multi-planar imaging and higher contrast resolution. Critical determinations of T 1 and T 2 values for ocular structures were not reported.From a technical standpoint, other than implementing surface coils and going to high field, it is useful to employ fast spin-echo (FSE) techniques that reduce total acquisition time by measuring multiple lines of k-space for each acquisition (15). In 2003, Simon et al (16) reported on the use of a three-dimensional T2-weighted FSE method to obtain a spatial resolution of 0.703 mm (readout), 0.938 mm (phase encode), and 1.2-1.6 mm (slice), over an 18 cm field of view (FOV) that included the eye. Total imaging time, however, was fairly long at nine minutes 52 seconds. Clinical results with this method were reported by McCaffery et al (17) and showed that with the thinner slice sections ob-

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Section: Resultsmentioning

confidence: 99%

“…There are, however, many reports of ocular MRI in the early literature (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13). For example, in 1987, Atlas et al (13) retrospectively reviewed their initial experience in 59 patients with MRI of the orbit concluding that there were five specific areas in which MRI ocular imaging provided important information.…”

mentioning

confidence: 99%

T₁ and T₂ measurements of the fine structures of the in vivo and enucleated human eye

Patz¹,

Bert²,

Frederick³

et al. 2007

Magnetic Resonance Imaging

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“…In humans, MR imaging appears to be especially useful for the evaluation of the intracanalicular and intracranial part of the optic nerve and the chiasm in the sagittal plane 3–5 and allows differentiation between enlargement of the optic nerve sheath and the optic nerve itself 6,3 . IV administration of contrast medium (gadolinium‐DTPA) provides information about the soft‐tissue perfusion of the normal ocular and orbital structures, especially of the normal retina, the meningeal sheath of the optic nerve, and of pathologic structures 7 …”

Section: Introductionmentioning

confidence: 99%

Magnetic Resonance Imaging of the Canine Optic Nerve

Boroffka

Görig

Auriemma

et al. 2008

Vet Radiology Ultrasound

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We describe the magnetic resonance (MR) imaging aspects of normal canine optic nerve, the diameter of the optic nerve as measured on MR images, and optimal MR sequences for the evaluation of the optic nerve using a 0.2T MR unit. Three millimeter contiguous slides of the normal canine orbital region were acquired in transverse and dorsal oblique planes using a variety of tissue weighting sequences. It was apparent that detailed anatomic assessment of the optic nerve can be performed with low-field MR imaging, but none of the sequences provided unequivocal superior image quality of the optic nerve. The mean diameter of the optic nerve sheath complex was 3.7mm and of the optic nerve 1.7 mm. The intraorbital and intracanalicular parts of the optic nerve are consistently visible and differentiation between the optic nerve and optic nerve sheath complex is possible using low-field MR systems.

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“…The TI at the "null point" (i.e., the value of TI for which SI equals zero for the tissue with a specific T1) is given by the equation [15], Tl nu " = -T1 x In['h (1 + e-TR{T' )]. (2) For TR » T1 , Tl nu" is given by the approximation [13] , Tlnu" = T1 x In 2.…”

Section: Methodsmentioning

confidence: 99%

“…Orbital lesions have been evaluated by many investigators with spin-echo (SE) MR imaging (1)(2)(3)(4)(5)(6)(7)(8)(9); and with the more recent implementation of high-resolution surface-coil techniques [10,11], significant advances have been made in MR imaging of the orbit. The orbit is somewhat unique in neuroradiology, in that the background stroma in this area is composed mainly of fat, which has a characteristic appearance on SE images.…”

Section: Stir Mr Imaging Of the Orbitmentioning

confidence: 99%

STIR MR imaging of the orbit

Atlas

Grossman

Hackney

et al. 1988

American Journal of Roentgenology

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0.6 T magnetic resonance imaging of the orbit

Cited by 22 publications

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T₁ and T₂ measurements of the fine structures of the in vivo and enucleated human eye

T₁ and T₂ measurements of the fine structures of the in vivo and enucleated human eye

Magnetic Resonance Imaging of the Canine Optic Nerve

STIR MR imaging of the orbit

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0.6 T magnetic resonance imaging of the orbit

Cited by 22 publications

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T1 and T2 measurements of the fine structures of the in vivo and enucleated human eye

T1 and T2 measurements of the fine structures of the in vivo and enucleated human eye

Magnetic Resonance Imaging of the Canine Optic Nerve

STIR MR imaging of the orbit

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Product

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T₁ and T₂ measurements of the fine structures of the in vivo and enucleated human eye

T₁ and T₂ measurements of the fine structures of the in vivo and enucleated human eye