Pemeriksaan CT-Scan Kepala A. Indikasi Pemeriksaan (Bontrager,
2001)1. Tumor,massa dan lesi2. Metastase otak3. Perdarahan intra
cranial4. Aneurisma5. Abses6. Atrophy otak7. Kelainan post trauma
(epidural dan subdural hematom)8. Kelainan congenitalB. Persiapan
pemeriksaan
a. Persiapan pasien Tidak ada persiapan khusus bagi penderita,
hanya saja instruksui-instruksi yang menyangkut posisi penderita
dan prosedur pemeriksaan harus diketahui dengan jelas terutama jika
pemeriksaan dengan menggunakan media kontras. Benda aksesoris
seperti gigi palsu, rambut palsu, anting-anting, penjempit rambut,
dan alat bantu pendengaran harus dilepas terlebih dahulu sebelum
dilakukan pemeriksaan karena akan menyebabkan artefak.Untuk
kenyamanan pasien mengingat pemeriksaan dilakukan pada ruangan
ber-AC sebaiknya tubuh pasien diberiselimut (Brooker, 1986)
b. Persiapan alat dan bahanAlat dan bahan yang digunakan untuk
pemeriksaan kepala dibedakan menjadi dua, yaitu :1. Peralatan
steril : Alat-alat suntik Spuit. Kassa dan kapas Alkohol2.
Peralatan non-steril Pesawat CT-Scan Media kontras Tabung oksigenc.
Persiapan Media kontras dan obat-obatanDalam pemeriksaan CT-scan
kepala pediatrik di butuhkan media kontras nonionik karena untuk
menekan reaksi terhadap media kontras seperti pusing, mual dan
muntah serta obat anastesi jika diperlukan. Media kontras digunakan
agar struktur-struktur anatomi tubuh seperti pembuluh darah dan
orga-organ tubuh lainnya dapat dibedakan dengan jelas. Selain itu
dengan penggunaan media kontras maka dapat menampakan adanya
kelainan-kelainan dalam tubuh seperti adanya tumor.Teknik injeksi
secara Intra Vena ( Seeram, 2001 )1. Jenis media kontras :
omnipaque, visipaque2. Volume pemakaian : 2 3 mm/kg, maksimal 150
m3. Injeksi rate : 1 3 mm/secC. Teknik Pemeriksaan Posisi pasien :
Pasien supine diatas meja pemeriksaan dengan posisi kepala dekat
dengan gantry. Posisi Objek : Kepala hiperfleksi dan diletkkan pada
head holder. Kepala diposisikan sehingga mid sagital plane tubuh
sejajar dengan lampu indikator longitudinal dan interpupilary line
sejajar dengan lampu indikator horizontal. Lengan pasien diletakkan
diatas perut atau disamping tubuh. Untuk mengurangi pergerakan dahi
dan tubuh pasien sebaiknya difikasasi dengan sabuk khusus pada head
holder dan meja pemeriksaan. Lutut diberi pengganjal untuk
kenyamanan pasien ( Nesseth, 2000 ).
Scan Parameter1. Scanogram : kepala lateral2. Range : range I
dari basis cranii sampai pars petrosum dan range II dari pars
petrosum sampai verteks.3. Slice Thickness : 2-5 mm ( range I ) dan
5-10 mm ( range II )4. FOV : 24 cm5. Gantry tilt : sudut gantry
tergantung besar kecilnya sudut yang terbentuk oleh orbito meatal
line dengan garis vertical.6. kV : 1207. mA : 2508. Reconstruksion
Algorithma : soft tissue9. Window width : 0-90 HU ( otak
supratentorial ); 110-160 HU ( otak pada fossa posterior );
2000-3000 HU ( tulang )10. Window Level : 40-45 HU ( otak
supratentorial ); 30-40 HU ( otak pada fossa posterior ); 200-400
HU ( tulang ) Foto sebelum dan sesudah pemasukkan media kontras
Secara umum pemeriksaan CT-scan kepala membutuhkan 6-10 irisan
axial. Namun ukuran tersebut dapat bervariasi tergantung keperluan
diagnosa. Untuk kasus seperti tumor maka jumlah irisan akan
mencapai dua kalinya karena harus dibuat foto sebelum dan sesudah
pemasukan media kontras. Tujuan dibuat foto sebelum dan sesudah
pemasukan media kontras adalah agar dapat membedakan dengan jelas
apakah organ tersebut mengalami kelainan atau tidak. Gambar yang
dihasilkan dalam pemeriksaan CT-scan kepala pada umumnya: Potongan
Axial I Merupakan bagian paling superior dari otak yang disebut
hemisphere. Kriteria gambarnya adalah tampak :
a. Bagian anterior sinus superior sagitalb. Centrum semi ovale
(yang berisi materi cerebrum)c. Fissura longitudinal (bagian dari
falks cerebri)d. Sulcuse. Gyrusf. Bagian posterior sinus superior
sagital Potongan Axial IV Merupakan irisan axial yang ke empat yang
disebut tingkat medial ventrikel. Criteria gambarnya tampak :
a. Anterior corpus collosumb. Anterior horn dari ventrikel
lateral kiric. Nucleus caudated. Thalamuse. Ventrikel tigaf.
Kelenjar pineal (agak sedikit mengalami kalsifikasi)g. Posterior
horn dari ventrikel lateral kiri Potongan Axial V Menggambarkan
jaringan otak dalam ventrikel medial tiga. Kriteria gambar yang
tampak :
a. Anterior corpus collosumb. Anterior horn ventrikel lateral
kiric. Ventrikel tigad. Kelenjar pineale. Protuberantia occipital
interna Potongan Axial VII Irisan ke tujuh merupakan penggambaran
jaringan dari bidang orbita. Struktur dalam irisan ini sulit untuk
ditampakkan dengan baik dalam CT-scan. Modifikasi-modifikasi sudut
posisi kepala dilakukan untuk mendapatkan gambarannya adalah tampak
:a. Bola mata / occular bulbb. Nervus optic kananc. Optic chiasmad.
Lobus temporale. Otak tengahf. Cerebellumg. Lobus oksipitalish. Air
cell mastoidi. Sinus ethmoid dan atau sinus sphenoid
CT Scan Apa yang dimaksud dengan CT Scanning Tubuh? Apakah
kegunaan umumnya? Bagaimana persiapannya? Apa saja peralatannya?
Bagaimana prosedur kerjanya? Bagaimana scan CAT dilakukan? Apa yang
akan saya alami selama dan setelah pemeriksaan ini? Siapa yang
menafsirkan hasil dan bagaimana cara mendapatkannya? Apa manfaat
dan risikonya? Apa keterbatasan CT Scanning Tubuh?
Apa yang dimaksud dengan CT Scanning Tubuh?
CT scan-kadang disebut juga CAT scan-adalah tes medis non-
invasif yang membantu dokter untuk mendiagnosa dan mengobati
kondisi medis.
CT scan menggabungkan peralatan khusus x-ray dengan komputer
canggih untuk menghasilkan gambar atau beberapa gambar bagian dalam
tubuh. Gambar-gambar penampang dari daerah yang sedang dipelajari
dapat diperiksa pada monitor komputer, dicetak atau ditransfer ke
CD.
CT scan organ, tulang, jaringan lunak dan pembuluh darah
memberikan kejelasan yang lebih besar dan memberikan rincian lebih
dari pemeriksaan x-ray biasa.
Dengan menggunakan peralatan khusus dan keahlian untuk membuat
dan menafsirkan CT scan tubuh, ahli radiologi dapat lebih mudah
mendiagnosa masalah seperti kanker, penyakit jantung, penyakit
menular, apendisitis, trauma dan gangguan muskuloskeletal.
Apakah kegunaan umumnya?Pencitraan CT adalah: Salah satu alat
terbaik dan tercepat untuk mempelajari dada, perut dan panggul
karena menyediakan gambarnya secara rinci, memperlihatkan potongan
melintang dari semua jenis jaringan. Merupakan metode yang
digunakan untuk mendiagnosis bermacam-macam kanker, termasuk
paru-paru, hati, ginjal dan kanker pankreas, karena gambar
memungkinkan dokter untuk mengkonfirmasi adanya tumor dan mengukur
ukuran, lokasi yang tepat dan sejauh mana keterlibatan tumor dengan
organ terdekat lainnya. Pemeriksaan yang memainkan peran penting
dalam diagnosis, deteksi dan pengobatan penyakit pembuluh darah
yang dapat menyebabkan stroke, gagal ginjal bahkan kematian. CT
scan umumnya digunakan untuk menilai emboli paru (bekuan darah
dalam pembuluh paru-paru) serta untuk aneurisma aorta perut (AAA).
Berguna dalam mendiagnosa dan mengobati masalah tulang belakang dan
luka pada tangan, kaki dan struktur tulang lainnya karena dengan
jelas dapat menunjukkan tulang bahkan yang sangat kecil serta
jaringan sekitarnya seperti otot dan pembuluh darah.In pediatric
patients, CT is rarely used to diagnose tumors of the lung or
pancreas as well as abdominal aortic aneurysms. For children, CT
imaging is more often used to evaluate: lymphoma neuroblastoma
kidney tumors congenital malformations of the heart, kidneys and
blood vesselsPhysicians often use the CT examination to: quickly
identify injuries to the lungs, heart and vessels, liver, spleen,
kidneys, bowel or other internal organs in cases of trauma. guide
biopsies and other procedures such as abscess drainages and
minimally invasive tumor treatments. plan for and assess the
results of surgery, such as organ transplants or gastric bypass.
stage, plan and properly administer radiation treatments for tumors
as well as monitor response to chemotherapy. measure bone mineral
density for the detection of osteoporosis.
How should I prepare?You should wear comfortable, loose-fitting
clothing to your exam. You may be given a gown to wear during the
procedure.Metal objects including jewelry, eyeglasses, dentures and
hairpins may affect the CT images and should be left at home or
removed prior to your exam. You may also be asked to remove hearing
aids and removable dental work.You may be asked not to eat or drink
anything for several hours beforehand, especially if a contrast
material will be used in your exam. You should inform your
physician of all medications you are taking and if you have any
allergies. If you have a known allergy to contrast material, or
"dye," your doctor may prescribe medications to reduce the risk of
an allergic reaction. Also inform your doctor of any recent
illnesses or other medical conditions and whether you have a
history of heart disease, asthma, diabetes, kidney disease or
thyroid problems. Any of these conditions may increase the risk of
an unusual adverse effect.Women should always inform their
physician and the CT technologist if there is any possibility that
they are pregnant. See the Safety page for more information about
pregnancy and x-rays.What does the equipment look like?
The CT scanner is typically a large, box-like machine with a
hole, or short tunnel, in the center. You will lie on a narrow
examination table that slides into and out of this tunnel. Rotating
around you, the x-ray tube and electronic x-ray detectors are
located opposite each other in a ring, called a gantry. The
computer workstation that processes the imaging information is
located in a separate control room, where the technologist operates
the scanner and monitors your examination.How does the procedure
work?
CT scan showing the liver
CT slice through mid abdomenIn many ways CT scanning works very
much like other x-ray examinations. X-rays are a form of
radiationlike light or radio wavesthat can be directed at the body.
Different body parts absorb the x-rays in varying degrees. In a
conventional x-ray exam, a small amount of radiation is aimed at
and passes through the body, recording an image on photographic
film or a special image recording plate. Bones appear white on the
x-ray; soft tissue, such as organs like the heart or liver, shows
up in shades of gray and air appears black.With CT scanning,
numerous x-ray beams and a set of electronic x-ray detectors rotate
around you, measuring the amount of radiation being absorbed
throughout your body. At the same time, the examination table is
moving through the scanner, so that the x-ray beam follows a spiral
path. A special computer program processes this large volume of
data to create two-dimensional cross-sectional images of your body,
which are then displayed on a monitor. This technique is called
helical or spiral CT.CT imaging is sometimes compared to looking
into a loaf of bread by cutting the loaf into thin slices. When the
image slices are reassembled by computer software, the result is a
very detailed multidimensional view of the body's
interior.Refinements in detector technology allow new CT scanners
to obtain multiple slices in a single rotation. These scanners,
called multislice CT or multidetector CT, allow thinner slices to
be obtained in a shorter period of time, resulting in more detail
and additional view capabilities.Modern CT scanners are so fast
that they can scan through large sections of the body in just a few
seconds, and even faster in small children. Such speed is
beneficial for all patients but especially children, the elderly
and critically ill.For children, the CT scanner technique will be
adjusted to their size and the area of interest to reduce the
radiation dose.For some CT exams, a contrast material is used to
enhance visibility in the area of the body being studied.How is the
CAT scan performed? The technologist begins by positioning you on
the CT examination table, usually lying flat on your back or less
commonly, on your side or on your stomach. Straps and pillows may
be used to help you maintain the correct position and to hold still
during the exam. Depending on the part of the body being scanned,
you may be asked to keep your hands over your head.Many scanners
are fast enough that children can be scanned without sedation. In
special cases, sedation may be needed for children who cannot hold
still. Motion will degrade the quality of the examination the same
way that it affects photographs.If contrast material is used, it
will be swallowed, injected through an intravenous line (IV) or
administered by enema, depending on the type of examination.
Next, the table will move quickly through the scanner to
determine the correct starting position for the scans. Then, the
table will move slowly through the machine as the actual CT
scanning is performed. Depending on the type of CT scan, the
machine may make several passes.You may be asked to hold your
breath during the scanning. Any motion, whether breathing or body
movements, can lead to artifacts on the images. This is similar to
the blurring seen on a photograph taken of a moving object. When
the examination is completed, you will be asked to wait until the
technologist verifies that the images are of high enough quality
for accurate interpretation.The CT examination is usually completed
within 30 minutes. The portion requiring intravenous contrast
injection usually lasts only 10 to 30 seconds.What will I
experience during and after the procedure?
CT scan: appendicitis
CT scan: normal appendixCT exams are generally painless, fast
and easy. With helical CT, the amount of time that the patient
needs to lie still is reduced.Though the scanning itself causes no
pain, there may be some discomfort from having to remain still for
several minutes. If you have a hard time staying still, are
claustrophobic or have chronic pain, you may find a CT exam to be
stressful. The technologist or nurse, under the direction of a
physician, may offer you some medication to help you tolerate the
CT scanning procedure.If an intravenous contrast material is used,
you will feel a pin prick when the needle is inserted into your
vein. You may have a warm, flushed sensation during the injection
of the contrast materials and a metallic taste in your mouth that
lasts for a few minutes. Some patients may experience a sensation
like they have to urinate but this subsides quickly.If the contrast
material is swallowed, you may find the taste mildly unpleasant;
however, most patients can easily tolerate it. You can expect to
experience a sense of abdominal fullness and an increasing need to
expel the liquid if your contrast material is given by enema. In
this case, be patient, as the mild discomfort will not last
long.When you enter the CT scanner, special light lines may be seen
on your body and are used to ensure that you are properly
positioned. With modern CT scanners, you will hear only slight
buzzing, clicking and whirring sounds as the CT scanner revolves
around you during the imaging process.You will be alone in the exam
room during the CT scan, unless there are special circumstances.
However, the technologist will always be able to see, hear and
speak with you at all times.With pediatric patients, a parent may
be allowed in the room but will be required to wear a lead apron to
minimize radiation exposure.After a CT exam, you can return to your
normal activities. If you received contrast material, you may be
given special instructions.Who interprets the results and how do I
get them?A physician, usually a radiologist with expertise in
supervising and interpreting radiology examinations, will analyze
the images and send a signed report to your primary care physician
or the physician who referred you for the exam, who will discuss
the results with you.Follow-up examinations are often necessary,
and your doctor will explain the exact reason why another exam is
requested. Sometimes a follow-up exam is done because a suspicious
or questionable finding needs clarification with additional views
or a special imaging technique. A follow-up examination may be
necessary so that any change in a known abnormality can be detected
over time. Follow-up examinations are sometimes the best way to see
if treatment is working or if an abnormality is stable over
time.What are the benefits vs. risks?Benefits CT scanning is
painless, noninvasive and accurate. A major advantage of CT is its
ability to image bone, soft tissue and blood vessels all at the
same time. Unlike conventional x-rays, CT scanning provides very
detailed images of many types of tissue as well as the lungs,
bones, and blood vessels. CT examinations are fast and simple; in
emergency cases, they can reveal internal injuries and bleeding
quickly enough to help save lives. CT has been shown to be a
cost-effective imaging tool for a wide range of clinical problems.
CT is less sensitive to patient movement than MRI. CT can be
performed if you have an implanted medical device of any kind,
unlike MRI. CT imaging provides real-time imaging, making it a good
tool for guiding minimally invasive procedures such as needle
biopsies and needle aspirations of many areas of the body,
particularly the lungs, abdomen, pelvis and bones. A diagnosis
determined by CT scanning may eliminate the need for exploratory
surgery and surgical biopsy. No radiation remains in a patient's
body after a CT examination. X-rays used in CT scans usually have
no immediate side effects.Risks There is always a slight chance of
cancer from excessive exposure to radiation. However, the benefit
of an accurate diagnosis far outweighs the risk. The effective
radiation dose for this procedure varies. See the Safety page for
more information about radiation dose. Women should always inform
their physician and x-ray or CT technologist if there is any
possibility that they are pregnant. See the Safety page for more
information about pregnancy and x-rays. CT scanning is, in general,
not recommended for pregnant women unless medically necessary
because of potential risk to the baby. Nursing mothers should wait
for 24 hours after contrast material injection before resuming
breast-feeding. The risk of serious allergic reaction to contrast
materials that contain iodine is extremely rare, and radiology
departments are well-equipped to deal with them.
Because children are more sensitive to radiation, they should
have a CT exam only if it is essential for making a diagnosis and
should not have repeated CT exams unless absolutely necessary. CT
scans in children should always be done with low-dose
technique.What are the limitations of CT Scanning of the
Body?Soft-tissue details in areas such as the brain, internal
pelvic organs, and joints (such as knees and shoulders) can often
be better evaluated with magnetic resonance imaging (MRI). A CT
exam is not generally indicated for pregnant women.A person who is
very large may not fit into the opening of a conventional CT
scanner or may be over the weight limitusually 450 poundsfor the
moving table.
MRI (Magnetic Resonance Imaging)
What is MRI of the Body?
MRI of the kneeMagnetic resonance imaging (MRI) is a noninvasive
medical test that helps physicians diagnose and treat medical
conditions.MRI uses a powerful magnetic field, radio frequency
pulses and a computer to produce detailed pictures of organs, soft
tissues, bone and virtually all other internal body structures. The
images can then be examined on a computer monitor, transmitted
electronically, printed or copied to a CD. MRI does not use
ionizing radiation (x-rays).Detailed MR images allow physicians to
better evaluate various parts of the body and determine the
presence of certain diseases that may not be assessed adequately
with other imaging methods such as x-ray, ultrasound or computed
tomography (also called CT, MDCT or CAT scanning).What are some
common uses of the procedure?
MR imaging of the body is performed to evaluate: organs of the
chest and abdomenincluding the heart, liver, biliary tract,
kidneys, spleen, bowel, pancreas and adrenal glands. pelvic organs
including the reproductive organs in the male (prostate and
testicles) and the female (uterus, cervix and ovaries). blood
vessels (MR Angiography). breasts.Physicians use the MR examination
to help diagnose or monitor treatment for conditions such as:
tumors of the chest, abdomen or pelvis. certain types of heart
problems. blockages, enlargements or anatomical variants of blood
vessels, including the aorta, renal arteries, and arteries in the
legs. diseases of the liver, such as cirrhosis and tumors, and that
of other abdominal organs, including the bile ducts, gallbladder,
and pancreatic ducts. diseases of the small intestine, colon,
rectum and anus. cysts and solid tumors in the kidneys and other
parts of the urinary tract. tumors and other abnormalities of the
reproductive organs (e.g., uterus, ovaries, testicles, prostate).
causes of pelvic pain in women, such as fibroids, endometriosis and
adenomyosis. suspected uterine congenital abnormalities in women
undergoing evaluation for infertility. breast cancer and implants.
fetal assessment in pregnant women.How should I prepare for the
procedure?You may be asked to wear a gown during the exam or you
may be allowed to wear your own clothing if it is loose-fitting and
has no metal fasteners.Guidelines about eating and drinking before
an MRI exam vary with the specific exam and also with the facility.
Unless you are told otherwise, you may follow your regular daily
routine and take food and medications as usual.Some MRI
examinations may require the patient to receive an injection of
contrast material into the bloodstream. The radiologist or
technologist may ask if you have allergies of any kind, such as
allergy to iodine or x-ray contrast material, drugs, food, the
environment, or asthma. However, the contrast material most
commonly used for an MRI exam, called gadolinium, does not contain
iodine and is less likely to cause side effects or an allergic
reaction.The radiologist should also know if you have any serious
health problems or if you have recently had surgery. Some
conditions, such as severe kidney disease may prevent you from
being given contrast material for an MRI. If there is a history of
kidney disease, it may be necessary to perform a blood test to
determine whether the kidneys are functioning adequately.Women
should always inform their physician or technologist if there is
any possibility that they are pregnant. MRI has been used for
scanning patients since the 1980s with no reports of any ill
effects on pregnant women or their babies. However, because the
baby will be in a strong magnetic field, pregnant women should not
have this exam unless the potential benefit from the MRI exam is
assumed to outweigh the potential risks. Pregnant women should not
receive injections of contrast material. See the Safety page for
more information about pregnancy and MRI.If you have claustrophobia
(fear of enclosed spaces) or anxiety, you may want to ask your
physician for a prescription for a mild sedative prior to the
scheduled examination.Jewelry and other accessories should be left
at home if possible, or removed prior to the MRI scan. Because they
can interfere with the magnetic field of the MRI unit, metal and
electronic objects are not allowed in the exam room. These items
include: jewelry, watches, credit cards and hearing aids, all of
which can be damaged. pins, hairpins, metal zippers and similar
metallic items, which can distort MRI images. removable dental
work. pens, pocketknives and eyeglasses. body piercings.In most
cases, an MRI exam is safe for patients with metal implants, except
for a few types. People with the following implants cannot be
scanned and should not enter the MRI scanning area unless
explicitly instructed to do so by a radiologist or technologist who
is aware of the presence of any of the following: internal
(implanted) defibrillator or pacemaker cochlear (ear) implant some
types of clips used on brain aneurysms some types of metal coils
placed within blood vesselsYou should tell the technologist if you
have medical or electronic devices in your body, because they may
interfere with the exam or potentially pose a risk, depending on
their nature and the strength of the MRI magnet. Examples include
but are not limited to: artificial heart valves implanted drug
infusion ports implanted electronic device, including a cardiac
pacemaker artificial limbs or metallic joint prostheses implanted
nerve stimulators metal pins, screws, plates, stents or surgical
staplesIn general, metal objects used in orthopedic surgery pose no
risk during MRI. However, a recently placed artificial joint may
require the use of another imaging procedure. If there is any
question of their presence, an x-ray may be taken to detect the
presence of and identify any metal objects.Patients who might have
metal objects in certain parts of their bodies may also require an
x-ray prior to an MRI. You should notify the technologist or
radiologist of any shrapnel, bullets, or other pieces of metal
which may be present in your body due to accidents. Dyes used in
tattoos may contain iron and could heat up during MRI, but this is
rarely a problem. Tooth fillings and braces usually are not
affected by the magnetic field but they may distort images of the
facial area or brain, so the radiologist should be aware of
them.Infants and young children usually require sedation or
anesthesia to complete an MRI exam without moving. Whether a child
requires sedation will depend on the childs age and the type of
exam being performed. Moderate and conscious sedation can be
provided at most facilities. A physician or nurse specializing in
the administration of sedation or anesthesia to children will be
available during the exam to ensure your child's safety. You will
be given special instructions how to prepare your child for the
sedation or anesthesia.What does the equipment look like?
The traditional MRI unit is a large cylinder-shaped tube
surrounded by a circular magnet. You will lie on a moveable
examination table that slides into the center of the magnet.Some
MRI units, called short-bore systems, are designed so that the
magnet does not completely surround you; others are open on the
sides (open MRI). These units are especially helpful for examining
patients who are fearful of being in a closed space and for those
who are very obese. Newer open MRI units provide very high quality
images for many types of exams; however, open MRI units with older
magnets may not provide this same image quality. Certain types of
exams cannot be performed using open MRI. For more information,
consult your radiologist.The computer workstation that processes
the imaging information is located in a separate room from the
scanner.How does the procedure work?Unlike conventional x-ray
examinations and computed tomography (CT) scans, MRI does not
depend on ionizing radiation. Instead, while in the magnet, radio
waves redirect the axes of spinning protons, which are the nuclei
of hydrogen atoms, in a strong magnetic field.The magnetic field is
produced by passing an electric current through wire coils in most
MRI units. Other coils, located in the machine and in some cases,
placed around the part of the body being imaged, send and receive
radio waves, producing signals that are detected by the coils.A
computer then processes the signals and generates a series of
images each of which shows a thin slice of the body. The images can
then be studied from different angles by the interpreting
radiologist.Frequently, the differentiation of abnormal (diseased)
tissue from normal tissues is better with MRI than with other
imaging modalities such as x-ray, CT and ultrasound.How is the
procedure performed?MRI examinations may be performed on
outpatients or inpatients.You will be positioned on the moveable
examination table. Straps and bolsters may be used to help you stay
still and maintain the correct position during imaging.
Devices that contain coils capable of sending and receiving
radio waves may be placed around or adjacent to the area of the
body being studied.If a contrast material will be used in the MRI
exam, a nurse or technologist will insert an intravenous (IV) line
into a vein in your hand or arm. A saline solution may be used. The
solution will drip through the IV to prevent blockage of the IV
line until the contrast material is injected.You will be moved into
the magnet of the MRI unit and the radiologist and technologist
will leave the room while the MRI examination is performed.If a
contrast material is used during the examination, it will be
injected into the intravenous line (IV) after an initial series of
scans. Additional series of images will be taken during or
following the injection.When the examination is completed, you may
be asked to wait until the technologist or radiologist checks the
images in case additional images are needed.Your intravenous line
will be removed.MRI exams generally include multiple runs
(sequences), some of which may last several minutes.Depending on
the type of exam and the equipment used, the entire exam is usually
completed in 15 to 45 minutes.
What will I experience during and after the procedure?Most MRI
exams are painless. However, some patients find it uncomfortable to
remain still during MR imaging. Others experience a sense of being
closed-in (claustrophobia). Therefore, sedation can be arranged for
those patients who anticipate anxiety, but fewer than one in 20
require it.It is normal for the area of your body being imaged to
feel slightly warm, but if it bothers you, notify the radiologist
or technologist. It is important that you remain perfectly still
while the images are being recorded, which is typically only a few
seconds to a few minutes at a time. For some types of exams, you
may be asked to hold your breath. You will know when images are
being recorded because you will hear tapping or thumping sounds
when the coils that generate the radiofrequency pulses are
activated. You will be able to relax between imaging sequences, but
will be asked to maintain your position without movement as much as
possible.You will usually be alone in the exam room during the MRI
procedure. However, the technologist will be able to see, hear and
speak with you at all times using a two-way intercom. Many MRI
centers allow a friend or parent to stay in the room as long as
they are also screened for safety in the magnetic environment.You
may be offered or you may request earplugs to reduce the noise of
the MRI scanner, which produces loud thumping and humming noises
during imaging. Children will be given appropriately sized earplugs
or headphones during the exam. MRI scanners are air-conditioned and
well-lit. Some scanners have music to help you pass the time.When
the contrast material is injected, it is normal to feel coolness
and a flushing sensation for a minute or two. The intravenous
needle may cause you some discomfort when it is inserted and once
it is removed, you may experience some bruising. There is also a
very small chance of irritation of your skin at the site of the IV
tube insertion. Some patients may sense a metallic taste in their
mouth after the contrast injection.If you have not been sedated, no
recovery period is necessary. You may resume your usual activities
and normal diet immediately after the exam. A few patients
experience side effects from the contrast material, including
nausea and local pain. Very rarely, patients are allergic to the
contrast material and experience hives, itchy eyes or other
reactions. If you experience allergic symptoms, notify the
technologist. A radiologist or other physician will be available
for immediate assistance.Manufacturers of intravenous contrast
indicate mothers should not breastfeed their babies for 24-48 hours
after contrast medium is given. However, both the American College
of Radiology (ACR) and the European Society of Urogenital Radiology
note that the available data suggest that it is safe to continue
breastfeeding after receiving intravenous contrast. The ACR Manual
on Contrast Media states:"Review of the literature shows no
evidence to suggest that oral ingestion by an infant of the tiny
amount of gadolinium contrast medium excreted into breast milk
would cause toxic effects. We believe, therefore, that the
available data suggest that it is safe for the mother and infant to
continue breastfeeding after receiving such an agent.If the mother
remains concerned about any potential ill effects, she should be
given the opportunity to make an informed decision as to whether to
continue or temporarily abstain from breastfeeding after receiving
a gadolinium contrast medium. If the mother so desires, she may
abstain from breastfeeding for 24 hours with active expression and
discarding of breast milk from both breasts during that period. In
anticipation of this, she may wish to use a breast pump to obtain
milk before the contrast study to feed the infant during the
24-hour period following the examination."For further information
please consult the ACR Manual on Contrast Media and its
references.Who interprets the results and how do I get them?A
radiologist, a physician specifically trained to supervise and
interpret radiology examinations, will analyze the images and send
a signed report to your primary care or referring physician, who
will share the results with you.Follow-up examinations are often
necessary, and your doctor will explain the exact reason why
another exam is requested. Sometimes a follow-up exam is done
because a suspicious or questionable finding needs clarification
with additional views or a special imaging technique. A follow-up
examination may be necessary so that any change in a known
abnormality can be detected over time. Follow-up examinations are
sometimes the best way to see if treatment is working or if an
abnormality is stable over time.What are the benefits vs.
risks?Benefits MRI is a noninvasive imaging technique that does not
involve exposure to ionizing radiation. MR images of the
soft-tissue structures of the bodysuch as the heart, liver and many
other organs is more likely in some instances to identify and
accurately characterize diseases than other imaging methods. This
detail makes MRI an invaluable tool in early diagnosis and
evaluation of many focal lesions and tumors. MRI has proven
valuable in diagnosing a broad range of conditions, including
cancer, heart and vascular disease, and muscular and bone
abnormalities. MRI enables the discovery of abnormalities that
might be obscured by bone with other imaging methods. MRI allows
physicians to assess the biliary system noninvasively and without
contrast injection. The contrast material used in MRI exams is less
likely to produce an allergic reaction than the iodine-based
contrast materials used for conventional x-rays and CT scanning.
MRI provides a noninvasive alternative to x-ray, angiography and CT
for diagnosing problems of the heart and blood vessels.Risks The
MRI examination poses almost no risk to the average patient when
appropriate safety guidelines are followed. If sedation is used
there are risks of excessive sedation. The technologist or nurse
monitors your vital signs to minimize this risk. Although the
strong magnetic field is not harmful in itself, implanted medical
devices that contain metal may malfunction or cause problems during
an MRI exam. There is a very slight risk of an allergic reaction if
contrast material is injected. Such reactions usually are mild and
easily controlled by medication. If you experience allergic
symptoms, a radiologist or other physician will be available for
immediate assistance. Nephrogenic systemic fibrosis is currently a
recognized, but rare, complication of MRI believed to be caused by
the injection of high doses of gadolinium contrast material in
patients with very poor kidney function.What are the limitations of
MRI of the Body?High-quality images are assured only if you are
able to remain perfectly still or hold your breath, if requested to
do so, while the images are being recorded. If you are anxious,
confused or in severe pain, you may find it difficult to lie still
during imaging.A person who is very large may not fit into the
opening of a conventional MRI machine.The presence of an implant or
other metallic object sometimes makes it difficult to obtain clear
images. Patient movement can have the same effect.Breathing may
cause artifacts, or image distortions, during MRIs of the chest,
abdomen and pelvis. Bowel motion is another source of motion
artifacts in abdomen and pelvic MRI studies. This is less of a
problem with state-of-the art scanners and techniques.Although
there is no reason to believe that magnetic resonance imaging harms
the fetus, pregnant women usually are advised not to have an MRI
exam unless medically necessary.MRI may not always distinguish
between cancer tissue and edema fluid.MRI typically costs more and
may take more time to perform than other imaging modalities.
21