硅油填充眼核磁共振成像与A型超声测量结果比较

Comparison of magnetic resonance imaging and A-mode ultrasound for the measurement of silicone oil-filled eyes

目的观察并探讨核磁共振成像（MRI）用于硅油填充眼眼球视轴测量的可行性及其优缺点。方法32例32只硅油填充眼纳入本研究。采用MRI横断面T1加权像（T1WI）、T2加权像（T2WI）检测硅油前后间隙，以脂肪抑制后T2WI成像测量眼球视轴；以角膜顶点至黄斑中心凹距离作为视轴长度，此连线上测量硅油后间隙的厚度。A型超声采取坐位及仰卧位检查，坐位测量眼球视轴长度，改变超声传播速度以修正眼球视轴长度；仰卧位检测硅油后间隙。结果MRI检测结果显示，硅油在T1WI像中信号较对侧玻璃体高，T2WI像中信号较玻璃体低，加脂肪抑制后硅油信号降低，化学位移伪影减少；受检眼玻璃体腔内均存在不同程度的硅油前后间隙，玻璃体后间隙厚度为（2．47±1．31）mm。A型超声检测结果显示，18只眼可检测到硅油后间隙，占56．25％。MRI、A型超声测量本组患者硅油填充眼视轴长度分别为（23．52±4．67）、（20．57±5．32）mm，两者比较，其差异有统计学意义（t=30．17，P〈0．05）。结论MRI能够用于硅油填充眼视轴测量，并对硅油前后间隙进行观察和测量。

Objective To investigate the feasibility of using magnetic resonance imaging （MRI） to measure the visual axis length in silicone oil filled eyeballs. Methods Thirty-two silicone oil-filled eyes of 32 patients were studied. The ante-silicone oil spaces （ASS） and retro-silicone oil spaces （RSS） on the visual axis was measured on the cross-sectional T1 weighted images （TIWI） and T2WI, the length of the visual axis was measured on the fat-suppressed TeWI. The length of the visual axis was the distance from the corneal vertex to the macular fovea, and it was also measured by A-mode ultrasound in sitting position with different ultrasonic velocity. The post-oil gap was also measured by A-mode ultrasound in supine position. Results Compared with the signal of the contralateral vitreous body, the silicone oil signal was higher on T^WI images, lower on TzWI images. After fat suppression, the silicone oil signal and chemical shift artifact were reduced. There were different levels of ASS and RSS in the vitreous cavity of all 32 cases, the RSS depth was （2.47± 1.31） mm on average by MRI. However, RSS was detected in only 56.25% （18 cases） eyeballs by A-mode ultrasound. The visual axis length of silicone oil filled eyes was （23.52± 4.67） mm by MRI, and （20.57±5.32） mm by A-mode ultrasound in sitting position. The differences between two measurements was statistically significant （t=30.17, P〈0.05）. Conclusions In addition to A-mode ultrasound, MRI might be another effective method to detect RSS and ASS, and to measure the axial length of silicone oil-filled eyes.