Song H K, Wehrli F W, Ma J
Department of Radiology, University of Pennsylvania Medical Center, Philadelphia 19104, USA.
Magn Reson Med. 1997 Feb;37(2):185-91. doi: 10.1002/mrm.1910370207.
The requirements for imaging the skin are dictated by the organ's layered structure, which extends only a few millimeters from the surface and thus demands extremely high resolution in this direction. While less critical, resolution in the remaining two dimensions determines whether the skin's accessory structures can be resolved. The problem is compounded by short transverse relaxation times, in particular of the dermis, the structure of most clinical interest. In this work images of the normal human skin were obtained in vivo at voxel sizes as small as 19 x 78 x 800 microm3, by means of customized 3D gradient and partial flip-angle spin-echo pulse sequences and very small transmit/receive coils on a 1.5T clinical imager equipped with high-power whole-body gradients. Structures resolved include hair follicles and the sublayers of the dermis. The very short time constant for the major component (91%) for transverse relaxation in the dermis (T2* approximately 10 ms) suggests the potential of substantial gains in achievable signal-to-noise ratio by shortening the echo time.
对皮肤成像的要求取决于该器官的分层结构，该结构从表面仅延伸几毫米，因此在这个方向上需要极高的分辨率。虽然其余两个维度的分辨率不太关键，但它决定了皮肤附属结构是否能够被分辨出来。横向弛豫时间短，尤其是真皮层（大多数临床关注的结构）的横向弛豫时间短，使问题更加复杂。在这项研究中，通过定制的三维梯度和部分翻转角自旋回波脉冲序列以及在配备高功率全身梯度的1.5T临床成像仪上使用非常小的发射/接收线圈，在体素大小低至19×78×800立方微米的情况下获得了正常人体皮肤的图像。分辨出的结构包括毛囊和真皮的亚层。真皮中横向弛豫主要成分（91%）的非常短的时间常数（T2*约为10毫秒）表明，通过缩短回波时间，有可能大幅提高信噪比。
