颌骨造釉细胞瘤的影像学研究

Imaging study of ameloblastomas of the jaw

目的研究颌骨造釉细胞瘤的影像学特征,探讨CT、MRI对颌骨造釉细胞瘤的诊断及鉴别诊断价值。方法回顾分析20例经手术病理证实的颌骨造釉细胞瘤的CT(20例)、MRI(10例)表现。观察病变的部位、形态、内部结构、邻近结构侵犯及囊内容物密度和(或)信号特征等。结果20例中,14例位于下颌磨牙与升支区,其他部位少见。CT表现:20例中,病变呈多房型13例,单房型7例;肿瘤造成邻近骨质缺损18例,其中9例缺损范围超过囊壁周长的1/2,5例肿瘤穿破邻近骨皮质,形成局部软组织肿块;9例牙根吸收,呈截断状;18例造成邻近重要结构(下颌管、上颌窦、鼻腔等)的侵犯;囊变区CT值范围为9.5～31.4HU,平均21.2HU。MRI表现:10例中,5例呈囊实性,实性部分均呈等T1、等T2信号;另5例呈纯囊性,其中4例呈不规则厚壁,1例囊壁见乳头状突起;囊内容物呈均一长T1、长T2信号7例,呈不均匀混杂信号3例。增强检查6例中,4例实体部分呈明显均一强化,2例囊壁呈明显不规则强化。结论造釉细胞瘤在发生部位、形态、内部结构及邻近结构侵犯等方面均具有一定的特征性。高分辨螺旋CT配合二维曲面牙科软件技术可显示病变的形态、周围骨质破坏、牙根吸收及邻近重要结构改变;MRI对于软组织成分的显示优于CT,二者联合应用对于提高造釉细胞瘤的术前诊断正确率有重要价值。

Objective To study the imaging features of ameloblastomas of the jaw, and to determine the value of CT and MRI in the diagnosis and differential diagnosis of ameloblastomas. Methods Twenty patients with ameloblastoms of the jaw confirmed pathologically were studied retrospectively. The location and shape of lesions, inner and adjacent structures, the density and/or signal intensity of cystic contents on CT （n =20） and/or MRI （n = 10） were analyzed. Results Among 20 the cases, 14 lesions located in molarramus region of mandible, the other sites were rare. On CT images, the lesions were mostly muhilocular. The lesions could destroy adjacent cortex, even extended more than half of cystic wall circle in 9 cases and formed soft tissue mass in 5 cases. Root apex resorption generally demonstrated truncation or serration type in 9 cases. The adjacent vital structures （ such as mandibular canal, maxillary sinus and nasal cavity） were always invaded by the lesions. CT value of the lesions ranged from 9. 5 HU to 31.4 HU （ mean 21.2 HU）. On MR images, 5 cases showed a mixed pattern of cystic and solid components, the solid part of the lesion appeared iso-T1 and iso-T2 signal intensity compared to adjacent muscles. 5 cases showed a purely cystic pattern, 4 of them had irregular thick wall and the other one had papillary projections. On enhanced MRI scans, 4 of 6 cases demonstrated homogenous and obvious enhancement in solid component, and the other 2 cases showed obvious irregular enhancement of the wall. Conclusion There were some characteristic imaging findings of ameloblastomas in location, shape, inner structures and growth behavior. HRCT with Denta scan software was prone to demonstrate the three-dimensional outline, destruction of adjacent cortical bone and adjacent vital structures. MRI was superior to CT in demonstrating the soft tissue of ameloblastomas. The application of both could improve the diagnostic accuracy of ameloblastomas of the jaw.