Annet L, Duprez T, Grandin C, Dooms G, Collard A, Cosnard G
Department of Medical Imaging, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, Avenue Hippocrate 10, 1200 Brussels, Belgium.
Neuroradiology. 2002 Apr;44(4):326-8. doi: 10.1007/s00234-001-0726-2. Epub 2002 Feb 7.
The purpose was to determine whether a strong decrease in apparent diffusion coefficient (ADC) within epidermoid cysts (ECs) is actually responsible for their bright signal intensity on diffusion-weighted (DW) trace images. We studied six patients with surgically proven ECs in whom ADC calculation from T2-weighted DW-EPI-SE data were performed within the ECs and within the deep white matter and cerebrospinal fluid (CSF) as references. All ECs displayed highest signal intensity on the DW trace images. ADC values ranged from 1,280 to 807 x 10(-6) mm(2)/s within cysts (with a mean value of 1,070), from 849 to 698 x 10(-6) mm(2)/s within white matter (with a mean value of 764) and from 3,370 to 2,980 x 10(-6) mm(2)/s within CSF (with a mean value of 3,185). ECs exhibited slightly higher ADC values than white matter, and not the strongly decreased ones which would have been expected if diffusion-weighting were the prominent mechanism for bright signal intensity of the ECs on DW images. However, the EC ADC values are much lower than those of the CSF. Other mechanisms must therefore be involved, i.e. the T2 shine-through effect. Reduced ADC is not the only explanation of the EC bright signal intensity on the DW trace images.
目的是确定表皮样囊肿（ECs）内表观扩散系数（ADC）的显著降低是否实际上是其在扩散加权（DW）追踪图像上信号强度增高的原因。我们研究了6例经手术证实为ECs的患者，在这些患者中，根据T2加权DW-EPI-SE数据在ECs内以及作为对照的深部白质和脑脊液（CSF）内进行ADC计算。所有ECs在DW追踪图像上均显示出最高信号强度。囊肿内的ADC值范围为1280至807×10⁻⁶mm²/s（平均值为1070），白质内为849至698×10⁻⁶mm²/s（平均值为764），CSF内为3370至2980×10⁻⁶mm²/s（平均值为3185）。ECs的ADC值略高于白质，而非如果扩散加权是ECs在DW图像上信号强度增高的主要机制所预期的显著降低的值。然而，ECs的ADC值远低于CSF的ADC值。因此，必定涉及其他机制，即T2透过效应。ADC降低并非ECs在DW追踪图像上信号强度增高的唯一解释。
