Artefacts of Magnetic Resonance Imaging in Patients Implanted With a Stainless Steel Glaucoma Drainage Micro-Device

Abstract

Purpose:: To evaluate the presence of artefacts in Magnetic Resonance Imaging (MRI) exam of optic nerve and brain in glaucomatous patients implanted with a stainless steel miniature glaucoma drainage device (Ex-PRESS^TM). This drainage implant is already cleared by FDA for MRI.

Methods:: Seven eyes of 5 glaucomatous patients with an Ex-PRESS^TM device positioned at the limbus under conjunctiva (n=2) or under a scleral flap (n=6) undergoing a complete MRI of the brain were recruited. MRI was performed on a 1.5 Tesla MR system (Signa Excite General Electric Milwaukee, WI, USA) with an eight channel phased-array head coil. An axial T1- weighted, axial and coronal T2-weighted with fat saturation and whole brain DP/T2- weighted MR imaging were obtained. Parameters evaluated: axial T1- weighted, TR 400 ms TE 17.6 ms, axial T2- weighted, TR 3700 ms TE 55 ms TI 150 ms, coronal T2- weighted with fat-saturation, TR 4040 ms TE 95.7 ms, axial DP/T2- weighted, TR 3000 ms TE 16.5/82.6 ms, all with slice thickness 3 mm matrix 256 × 256 FOV 160 mm. A 1 to 5 rating scale was applied for an overall rating of the effects on DP/T2 pulse sequence on imaging of optic nerve and brain. A score of 1 indicated masking of structures, 2 indicated that structures were visible but indistinct and that imaging was not suitable for clinical purposes, 3 indicated that visualization was sufficient for clinical evaluation, 4 indicated a good visualization, 5 indicated excellent visualization.

Results:: When optic nerve visualization was rated, one optic nerve was scored 2, three optic nerves were scored 3 and three optic nerves were scored 4 (mean score 3.20 ± 0.84 S.D.) When whole brain imaging was evaluated four eyes had a score of 4 and three eyes had a score of 5 (mean score 4.20 ± 0.45 S.D.).Mean signal intensity (SI) values within ROIs were not significantly different (mean SI in Right Optic nerve = 81.33 ± 2.34 S.D. mean SI in Left Optic nerve SI = 81.71 ± 2.73 S.D).

Conclusions:: Our data support the effectiveness of MRI exam with minimal artefacts in imaging interpretation, even in neighbouring structures. No effect was observed in brain imaging. This is the first report on MRI in patients implanted with an Ex-PRESS^TM device.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • optic nerve