Prenatal diffusion-weighted MRI of fetal brain lesions: Preliminary clinical experience

Prenatal Diffusion-Weighted Imaging (DWI) was recently demonstrated to be feasible in the normal fetal brain. We report our preliminary experience of abnormal prenatal DWI findings in the brains of eight fetuses with suspected lesions on the basis of clinical and ultrasound findings. The diffusion-weighted echo-planar sequence, which had an acquisition time of 14-18 seconds, was performed with the mother holding her breath. Slice thickness varied from 5 to 6 mm, the TR was 4000-5000 ms, the TE was 81 ms, the in plane resolution was 2.5x2.5 mm. Apparent Diffusion Coefficient (ADC) trace maps were calculated on the basis of three axes diffusion-sensitized images. In two cases, hypoxic-ischemic focal lesions showed a DWI signal compatible with the acute or subacute stage. In two cases of recent fetal death, the brain ADC was markedly decreased. In a case of fetus papyraceus, the intracranial ADC value suggested the brain having a solid structure. In a case of intraventricular hemorrhage, the lesion was more conspicuous on DWI than on conventional images. In a case of brain developmental malformations, the ADC showed values compatible with decreased cellular proliferation disorders. In a case of intracranial cystic mass, DWI readily differentiated between an arachnoid and an epidermoid cyst. DWI appears to enhance the prenatal MRI capability of characterizing hypoxic-ischemic lesions. Moreover, prenatal DWI seems to provide valuable information on the timing of fetal death. ADC determination can provide additional data on the nature of brain malformations in cases of abnormal development.