If your veterinarian
recommends a CT scan, an MRI or radiation therapy for your pet, you may
have some questions. Below are answers to some commonly asked questions.
A new $1 million
renovation to the radiology section at the Veterinary Medical Teaching
Hospital in Kansas State University's College of Veterinary Medicine showcases
advanced in-house technology that is rarely seen in veterinary teaching
hospitals.
The three-room
suite features premier computed tomography -- CT -- for small animals and
horses as well as magnetic resonance imaging -- MRI -- capabilities for
small animals. The equipment, which is rarely available for large animals,
offers the same specialized medical care used for human patients.
The CT scanner
is used to assimilate multiple X-ray images into a two-dimensional, cross-sectional
image. MRI scans, which are superior to traditional X-ray images, are used
to examine internal structures of the body, particularly the soft tissues
of the brain, spinal cord, joints and abdomen. MRI is typically used for
detecting and monitoring cancers.
ANSWERS TO COMMONLY
ASKED QUESTIONS ABOUT CT AND MRI
Why does my
pet need CT or MRI?
Some areas of
the body are difficult to image with conventional radiographs (X-rays)
or ultrasound. Because of complex anatomy or overlying structures, tomographic
(or slice) images must be used to evaluate the area.
CT and MRI
also both have the advantage of displaying images digitally, which can
emphasize differences between normal and abnormal tissues making problems
easier to detect, and the margins easier to recognize.
Is it safe?
Magnetic resonance
imaging uses radio-frequency energy to excite molecules in your pet --
similar to that which a radio or TV station emits.
No ionizing
radiation is used. Low magnetic fields have not been demonstrated to be
harmful to animals or people.
Caution must
be taken in animals or people that have been implanted with pacemakers
or metal clips in certain areas.
Because pets
cannot move during the MRI scan, they must be anesthetized during the procedure.
While there are some risks inherent to anesthesia, at the KSU VMTH, anesthesia
is supervised by board certified (American College of Veterinary Anesthesiology)
specialists who carefully assess each patient prior to the procedure. While
CT scanning uses ionizing radiation, the dose received by the patient is
similar to that of conventional radiographs (X-rays) and less than that
for a human receiving a similar procedure. CT should be avoided in breeding
animals during the first trimester of pregnancy. Pets are usually anesthetized
for CT scans.
These procedures
are relatively quick (15 - 30 minutes), further minimizing the risks.
Why does my
pet need to be anesthetized or sedated for the procedure?
Both CT and
MRI require the patient to hold still during the scanning procedure. Even
small movements result in artifacts which degrade the scan quality.
Why does the
procedure cost more than conventional (radiographs) X-rays?
Equipment costs
and maintenance costs are much higher for CT and MRI equipment. A CT scanner
will cost 10 – 20 times as much as a conventional X-ray unit. An MRI unit
costs 20 – 50 times as much.
How does CT
work?
CT units produce
a very thin fan of x-rays which are directed through the patient and strike
a row of radiation detectors. The amount of radiation going through a specific
part of the patient, and therefore reaching the detector is related to
the density of the body part. A CT scanner takes numerous views of each
part, and reconstructs an image based on the density of different areas.
How does MRI
work?
When a patient
is put in a strong magnet, some of the atoms become aligned with the magnetic
field. If a carefully tuned radio-frequency (RF) pulse is sent into the
patient, those atoms can be tipped over. As the atoms realign themselves
with the magnetic field, they give off an RF pulse that can be detected
by the MRI scanner. The amount of RF signal given off, and the time at
which it is released are characteristic for certain tissues. RF signal
changes can differentiate normal from abnormal tissues such as those affected
by cancer, infection or trauma.
What are the
indications for CT?
CT is particularly
useful for looking at complex bony structures such as the skull, spine
or joints. It is also useful for detecting and characterizing lung disease.
Both CT and MRI are excellent for assessing blood flow to an organ or region.
What are the
indications for MRI?
MRI is useful
for looking at soft tissue structures which have low contrast on conventional
radiographs (x-rays) and complex soft tissue structures.
The largest
indications are in imaging the brain, spinal cord, and soft tissues of
the musculoskeletal system.
COMMONLY ASKED
QUESTIONS ABOUT RADIATION THERAPY
How does radiation
therapy work?
The linear accelerator
can be programmed to produce photons or electrons to treat deep or superficial
tumors, respectively. These energy beams can be directed to specific sites
on the body to treat the patient. Radiation therapy works by sterilizing
cells, which keeps them from being able to undergo successful division.
This means a large tumor may not shrink immediately with RT.
The cells will
be sterilized, and will live out their natural life span.
When they attempt
to divide, they will be unable to do so and will die resulting in tumor
shrinkage.
Why does my
pet need radiation therapy?
Radiation therapy
is used to treat inoperable tumors that have not spread to other sites
in the body. Like, surgery, this offers a potential cure for localized
tumors. It may be combined with surgery or it may be combined with chemotherapy
to address both local and systemic disease.
Certain chemotherapy
drugs act as radiation sensitizers and are used for their ability to enhance
the effects of radiotherapy.
How often is
radiation therapy administered?
RT can be used
with curative or palliative intent (relieving clinical signs).
When administered
with curative intent RT is given in small fractions over three to four
weeks. For palliative effects, RT is given in large fractions once weekly
for three weeks.
What types of
side effects can happen with radiation therapy?
Radiation therapy
in dogs and cat does NOT cause systemic side effects (tiredness, loss of
appetite, nausea). Side effects of RT occur more often with curative
attempts, and can be categorized in to acute and chronic problems.
Acute injuries
begin during or shortly after the completion of therapy. They arise in
tissues within the RT field that are growing and dividing rapidly; the
most common acute effects are skin problems that mimic a severe sunburn.
Acute side effects
will resolve with minimal nursing care and they are not considered to be
does limiting. Chronic side effects arise from damage to tissues within
the RT field that are slowly renewing populations (i.e. bone, retina, brain).
Clinical syndromes
include the formation of bony sequestra, retinal lesions, brain cataracts
and neurologic signs. Chronic side effects are dose limiting, veterinary
protocols are designed to minimize long term problems.
Why does my
pet need to be anesthetized or sedated for the procedure?
Because pets
cannot move during the radiation therapy, they must be anesthetized during
the procedure. While there are some risks inherent to anesthesia, at the
KSU VMTH, anesthesia is supervised by board certified (American College
of Veterinary Anesthesiology) specialists who carefully assess each patient
before the procedure.
Each treatment
is very short, animals are anesthetized for 10-15 minutes daily.
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Information Provided By
K-State Media Relations
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