APPENDIX VIII
DIAGNOSTIC IMAGING PROCEDURES
Diagnostic imaging procedures offer noninvasive
approaches for visualizing the structure and func-
tion of internal organs. Though each procedure
has specific applications and diagnostic value, doc-
tors often use procedures in combination with
one another to give detailed information to help
diagnose health conditions as well as monitor the
effectiveness of treatment. Some procedures
involve the injection or consumption of radio-
opaque contrast media (special dyes) or radioiso-
topes to create dimensional images.
The entries in this appendix discuss procedures
that have broad application across body systems
and health conditions. Entries for diagnostic imag-
ing procedures specific to a particular body system
are in the section of The Facts On File Encyclopedia of
Health and Medicinethat covers that body system.
For example, MAMMOGRAM—X-RAYof the breast—
appears in the section “The Reproductive System”
and INTRAVENOUS PYELOGRAM(IVP)—imaging of the
KIDNEYS—appears in the section “The Urinary Sys-
tem.”
computed tomography (CT) scanA radio-
logic procedure that uses multiple X-RAYimages to
create multi-dimensional pictures of the structure
of internal organs. The CT scanner takes numer-
ous X-ray “slices” that a computer then assembles
into an image of the organ or structure. The X-ray
tube rotates within the scanner, moving around
area of the body being scanned. A CT scan may be
done with or without contrast media, depending
on the reason for the procedure. CT scan of the
abdomen may require a bowel prep (laxative or
enema). Most other CT scans do not require any
advance preparation.
The scan itself is painless, though some people
may feel claustrophobic when inside the scanner.
Some CT scanners are open, which reduces the
sense of being closed in. Most often it is necessary
to change out of regular clothing into a hospital
gown for the scan, to prevent interference from
objects such as zippers and buttons. A CT scan
generally takes between 15 minutes and an hour,
depending on the type of images the doctor
desires. No recovery is necessary; when the radi-
ologist is satisfied with the quality of images, the
person may get dressed and leave.
There is a slight risk of an adverse or allergic
reaction to contrast dye, which is iodine-based. CT
scan does expose a person to ionizing radiation,
though for most procedures the level of exposure
is within the established safety boundaries. Fre-
quent CT scans or complex CT scans, such as car-
diac multislice CT (CMCT), result in significantly
higher exposure, however. It is important to dis-
cuss the potential risks of such exposure before
undergoing the procedure.
Doctors may order CT scans to evaluate STROKE
and TRAUMATIC BRAIN INJURY(TBI), complex or ques-
tionable BONEfractures, internal masses that could
be tumors, and damage to the HEARTafter HEART
ATTACK. Certain surgeries that require extraordi-
nary precision, such as operations on the BRAIN
(for example, THALAMOTOMY and PALLIDOTOMY),
may use CT scan to guide the placement of surgi-
cal instruments.
magnetic resonance imaging (MRI) An
imaging procedure that uses powerful magnetic
energy to visualize internal organs and structures.
MRI does not involve exposure to radiation. The
nuclei of hydrogen atoms (a component molecule
of water) align themselves in a known pattern
within the body’s natural magnetic field. The MRI
machine emits a strong pulse of electromagnetic
energy, also called radiofrequency (RF) energy,
causing the hydrogen nuclei to temporarily417