60.一位無症狀之成年人接受 MRI 檢查,下圖 T2 加權影像中箭頭所指為何種狀況? (A)脊髓脫髓鞘(cord demyelination)(B)脊髓空洞症(syrinx)(C)截斷假影(truncation artifact)(D)反摺假影(flow aliasing artifact)