出血坏死性鼻息肉的CT和MRI诊断

CT and MRI diagnosis of hemorrhagic and necrotic nasal polyps

目的探讨出血坏死性鼻息肉的CT和MRI表现。方法回顾性分析17例经病理证实的出血坏死性鼻息肉的影像资料。其中14例行CT检查，16例行MR检查，15例同时行MR增强检查。结果17例病变均以上颌窦口为中心向鼻腔及上颌窦内生长，边缘清晰，16例形态不规整，呈浅分叶状，仅1例呈卵圆形。CT表现：14例病变表现为密度不均匀的软组织肿块影，2例分别在病变周边及内部见到条形及结节状高密度影，邻近骨质均呈压迫、吸收改变，局部骨质不连续，以上颌窦内壁最常见。MRI表现：16例病变内部在T1WI上为低信号（与脑灰质相比），T2WI上为高信号，14例同时伴有线样的低信号分隔；15例病变周边可见到T1WI为等信号、T2WI为低信号的不规则环形影围绕；15例行增强检查的病变呈不均匀性明显强化，强化部分形态各异，10例内部为多发结节状强化，4例为斑片状强化，1例强化外观似叶片状，而T2WI上的低信号环不强化。4例病变的鼻腔侧周边可见边缘清楚的囊状液体信号影，向前至鼻前庭，向后达后鼻孔区，增强后不强化。11例行动态增强扫描，其中7例时间-信号强度曲线（TIC）呈持续上升型；4例呈速升缓降型。结论MRT2WI上内部的不均匀高信号为低信号围绕以及增强后结节状、斑片状的强化特征均是出血坏死性鼻息肉特异的MRI表现，而CT有助于判断病变性质，明确诊断有一定困难，MRI应是出血坏死性鼻息肉的首选检查方法。

Objective To study the CT and MRI findings of hemorrhagic and necrotic nasal polyps. Methods The imaging data of 17 cases with hemorrhagic and necrotic nasal polyps confirmed by surgery and pathology were analyzed retrospectively. CT was performed in 14 cases, MRI in 16 cases, of which 15 also underwent contrast-enhanced MRI. Results All 17 lesions with well-circumscribed margin originated in the areas of maxillary sinus ostia and extended into adjacent nasal cavity and maxillary sinus. The lesions appeared as lobular shape in 16 cases and oval shape in 1 case. On non-enhanced CT, 14 lesions showed heterogenous soft tissue density masses, the hyperdense strip and nodule were detected on the periphery and in the center of 2 lesions respectively. All the involved bony walls were compressed and remodeled with focal defect,especially in the medial wall of maxillary sinus. On MRI, all 16 lesions revealed inhomogenous signal. The central region of the lesions appeared hypointense signal on T1WI compared to gray matter and hyperintense signal on T2WI with line-like hypointense signal septa in 14 cases, the irregular hypointense signal rims were also found on the periphery of 15 lesions on T2WI, postcontrast MR imaging showed strongly inhomogenous enhancing masses with non-enhancing hypointense rim, the appearances of enhancement showed multiple nodules in 10 cases, patches in 4 cases and leaf-like in 1 case. The typical simple polyps were present in the ipsilateral nasal cavity of the lesions in 4 cases, extending into nasal vestibule anteriorly and choana posteriorly. On dynamic contrast-enhanced MRI in 11 cases, the time- intensity curves （TIC） showed increasing enhancement type in 7 cases and rapid enhancement and slow wash-out type in 4 eases. Conclusion The inhomogenous hyperintensity surrounded by the peripheral hypointense rim on MR T2WI and marked nodular and patchy enhancement appearance are typical features of hemorrhagic and necrotic nasal polyps. CT is helpful to judge the nature of lesions, but difficultly confirms the diagnosis, while MRI should be the imaging modality of first choice for hemorrhagic and necrotic nasal polyps.