from those multiple two dimensional projections.

将这些二维投影进行组合
That mathematical process is called

所采用的数学方法叫做
reconstruction from back projections

反投影法
and it results in a three dimensional image,

用这种方法就能得到三维图像
in a CT a slice of the -- object of the patient is obtained

通过沿轴向旋转探测器中的放射源
by rotating the source in the detector around that axial location.

就能得到病人一个身体层面的情况
What we're going to start

我们要从
with is talking about an alternate to CT--

一种CT机的替代机器开始讲起
we're going to talk about an alternate to CT

我们由一种CT机的替代机器开始讲
which forms the same kind of images.

它能生成某种图像
That is, images of an axial location, maybe a transverse image;

可以轴向的图可以是横断面图
a slice from the body

就像人体的一个切片