苯丙酮尿症脑部病变扩散加权成像

Diffusion Weighted Imaging of White Matter Abnormalities in Patients with Phenylketonuria

目的使用磁共振扩散加权成像(DWI)技术研究苯丙酮尿症(phenylketonuria,PKU)患者脑白质内病灶的扩散特点,并观察表观扩散系数(apparent diffusion coefficient,ADC)的变化。资料与方法对8例临床确诊的PKU患儿及性别、年龄相匹配的8名健康儿童(对照组)行T1WI、T2WI及DWI,测量侧脑室后角T2WI异常信号区及放射冠正常白质的ADC值和对照组相应部位的ADC值。结果在T2WI上,所有未经治疗的PKU患儿均表现为非占位性、斑片状、条带状高信号,在X、Y、Z3个方向同时施加扩散梯度的跟踪ADC图(trace APC map)上显示更清晰。患儿大脑白质病灶X、Y、Z3个方向的ADC值明显低于对照组相应部位脑白质的ADC值,两者差异存在统计学意义(P<0.05)。平均ADC值比对照组相应部位减少23%,侧脑室后角扩散各向异性消失(F=0.195,P=0.825)。结论未经治疗的PKU白质异常在DWIav上显示更清晰,DWI可提供PKU患儿脑白质病灶的病理信息。

Objective To evaluate the features of brain white matter lesions in phenylketonuria（PKU）with diffusion weighted MR imaging（DWI）,and to explore the apparent diffusion coefficient（ADC）value.Materials and Meth-ods Magnetic resonance（MR）imaging,which included T1-weighted,T2-weighted,fluid-attenuated inversion-recovery（FLAIR）,and diffusion-weighted image,was performed in 8 patients with PKU and 8 age-and sex-matched health volunteers.Abnormal signal around the posterior horn of lateral ventricle on T2WI and the WM in coronal radiation were selected as region of interest.Apparent diffusion coefficient of water（ADC,10^-3 mm^2/s）in the X,Y and Z directions（ADCX,Y,Z）was calculated in patients and matched health volunteer.Results Patchy areas of increased signal intensity located sy mmetrically in the parieto-occipital WM were demonstrated on T2WI images in all untreated PKU.Those abnormalities demonstrated on conventional MRI were observed with even better contrast in the DWI images.The ADCX,Y,Z value of the lesion area in PKU patients is lower than that of the same area in normal controls with great significance.The mean ADC of water measured in PKU lesions decreased by approximately 23% compared to the ADC calculated for the same volume of interest in controls.The anisotropy observed in the group of controls was not clearly observed in periventricular areas in the group of PKU patient.Conclusion The WM lesions are more conspicuous on diffusion-weighted images with lower ADC values and loss of their anisotropy,which suggested that the intramyelinic vacuole formation 0.lead to an increase in the distance between the currently unorganized myelin layers.