多层螺旋CT容积再现技术显示正常内耳及内耳病变的价值

Visualization of normal and abnormal inner ear with volume rendering technique using multislice spiral CT

目的评价容积再现技术(VRT)对正常内耳及内耳病变的显示能力。方法对20例(40耳)正常内耳及42例(61耳)内耳病变患者行多层螺旋CT横断面扫描,扫描参数为120kV,100mAs,0.75mm准直器宽度,螺距为1,高分辨骨算法重建。对感兴趣耳进行VRT重建。结果VRT图像清晰显示了正常内耳的空间立体结构。40耳先天性内耳发育畸形VRT图像均立体、直观、清晰地显示了畸形的形态和部位。VRT表现为:(1)Michel畸形1耳:内耳完全缺如;(2)共同腔畸形3耳:耳蜗与前庭不能相互区分,呈一囊状结构;(3)不完全分隔Ⅰ型3耳:耳蜗呈囊状,前庭扩大呈囊状,二者可相互区分;(4)不完全分隔Ⅱ型(即Mondini型)5耳:耳蜗仅1.5圈,中圈和顶圈融合,前庭扩大;(5)前庭与半规管畸形14耳:耳蜗正常,前庭扩大,半规管短小、缺如或扩大;(6)前庭导水管扩大14耳:前庭导水管开口扩大呈喇叭口状,与总脚相通。骨化性迷路炎患者7例(7耳),4耳重组时不能完整地显示内耳的立体结构,3耳表现为耳蜗变细或半规管显示不完整。14例(14耳)迷路瘘管患者中,耳蜗破坏1耳,耳蜗、前庭、水平半规管、上半规管均破坏3耳,仅水平半规管破坏10耳。VRT图像表现为半规管或耳蜗与团状高密度结构相连,重组时不能相互分开。结论VRT可清晰显示正常内耳及部分内耳病变,对内耳病变的诊断有重要帮助。

Objective To evaluate the ability of the volume rendering technique to display the normal and abnormal inner ear structures. Methods Forty normal earand 61 abnormal inner ears （40 congenital inner ear malformations, 7 labyrinthitis ossificans, and 14 inner ear erosion caused by cholesteatomas） were examined with a MSCT scanner. Axial imaging were performed using the following parameters ：120 kV, 100 mAs,0.75 mm slice thickness, a pitch factor of 1. The axial images of interested ears were reconstructed with 0.1 mm reconstruction increment and a FOV of 50mm. The 3D reconstructions were done with volume rendering technique on the workstation. Results In the subjects without ear disorders a high quality 3D visualization of the inner ear could be achieved. In the patients with inner ear disorders all inner ear malformations could be clearly displayed on 3D images as follows： （1）Michel deformity （ one ear） ： There was complete absence of all cochlear and vestibular structures. （ 2 ） common cavity deformity（3 ears）： The cochlea and vestibule were represented by a cystic cavity and couldn＇t be differentiated from each other. （3） incomplete partition type Ⅰ （3 ears）：The cochlea lacked the entire modiolus and cribriform area, resulting in a cystic appearance. （4） incomplete partition type Ⅱ （Mondini deformity） （5 ears） ：The cochlea consisted of 1.5 turns, in which the middle and apical turns coalesced to form a cystic apex. （ 5 ） vestibular and semicircular canal malformations （ 14 ears ）： Cochlea was normal, vestibule dilated, semicircular canals were absent, hypoplastic or enlarged. （6）dilated vestibular aqueduct （ 14 ears） ： The vestibular aqueduct was bell-mouthed. In 7 patients with labyrinthitis ossificans, 3D images failed to clearly show the completeinner ears in 4 ears because of too high ossifications in the membranous labyrinth. In the other 3 ears volume rendering could display the thin cochlea basal turn and the intermittent semicircular canals. In the patients with cholesteatomas 3D volume rendering images could identify the site of the bony labyrinth erosion and its surrounding structures. Conclusions Volume rendering technique can provide higher quality three-dimensional images of the bony labyrinth and serves as a useful tool for analysis of normal and anomalies of the inner ear.