CT and MRI differ in two basic ways.
CT uses x-rays to detect and
record the radiation absorbed by different tissues, and sends the data
to a computer to transform into images. MRI does not use x-rays.
Instead,
MRI employs a powerful magnetic field to monitor the nuclei of
hydrogen atoms in water, the most abundant element in the body. When
subjected to the magnetic field of an MRI, the hydrogen protons are
knocked out of alignment and emit a radiofrequency signal that is
detected by the MRI machine, which then processes the signals into
images.
CT scans usually show little differentiation in soft
tissues, but highlight solid structures, like calcium deposits or
kidney stones.
MRI scans emphasize detailed tissue structures due to differences in water content.
Source: ehealthmd.com
Because
Tom has the type of cancer that can move into either soft tissue or
bony structures, both MRIs and CT scans have been used at different
times. The main benefit for Tom is that a CT scan is usually much
quicker and easier - both to get one scheduled, and to actually go
through it.
