NCCN Guidelines for Patients
Rectal Cancer, Version 1.2017
Some imaging tests use contrast. Contrast is a dye
that will be injected into your bloodstream. It makes
the pictures clearer. Some people have an allergic
reaction to the dye. Tell your doctor if you’ve had
problems with contrast in the past.
CT with contrast
omography) takes many pictures of
a body part using x-rays. A computer combines the
x-rays to make one detailed picture. The picture is
saved for later viewing by the radiologist.
CT is advised to see if the cancer has spread. Get
scans of your chest, abdomen, and pelvis. Contrast
should be used. The radiologist will look for cancer in
nearby and distant sites.
During the scan, you will need to lie face up on a
table. The table will move through the machine. As
the machine takes pictures, you may hear buzzing,
clicking, or whirring sounds.
You will be alone in the room during the test. In
a nearby room, the technician will operate the
machine. He or she will be able to see, hear, and
speak with you at all times. One scan is completed in
about 30 seconds. You will likely be able to resume
your activities right away unless you took a sedative.
maging) uses a magnetic
field and radio waves to make pictures. There are
three reasons why you may receive an MRI. Your
doctor may order an MRI if the CT scan was unclear.
Contrast should be used. Second, MRI and chest
CT without contrast may be done if you can’t receive
CT contrast. Third, you may receive a pelvic MRI to
assess the extent of the cancer in your pelvis. The
scan can show the tumor depth and if cancer is in
Getting MRI is much like getting CT. Except, you will
lie on top of and wear a coil device. The latter coil will
cover your body from below your chest to the top of
your legs. Coils will send and receive radio waves.
Straps may be used to help you stay in place. MRI
may cause your body to feel a bit warm.
Instead of pelvic MRI, you may receive an endorectal
ultrasound. This test can also show the extent of
cancer in your pelvis. A small probe will be inserted
into your rectum. The probe will emit sound waves
that will bounce off of tissue and make echoes. The
echoes will make a picture that will be seen by your
doctor on a screen.
Sometimes CT is combined with PET (
omography). When used together, they
are called a PET/CT scan. PET/CT scan is not often
used to plan treatment for rectal cancer.
There are three reasons why you may have a PET/
CT scan. PET/CT can show how big a tumor is if you
have metastases. PET/CT can also find metastases
other than in the liver that would exclude surgery.
Last, PET/CT may be received if the CT scan is
unclear or you can’t receive contrast.
PET/CT may be done with one or two machines
depending on the cancer center. For PET, a sugar
radiotracer will first be injected into your body. The
radiotracer will be detected with a special camera
during the scan. Cancer cells will appear brighter
than normal cells because they use sugar more
quickly. PET can show even small amounts of