2.comprehensive written report (mri)
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Polytechnic University of the Philippines
Sta. Mesa, Manila
College of Engineering
Department of Electronics and Communication Engineering
MRI- Magnetic Resonance Imaging
Barrion, John Ervin M.
Gopez, Jayson B.
Sto. Domingo, Joziel R.
(Researchers)
BSECE IV-2
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Engr. Marianito P. Gallego Jr.
(Professor)
MRI- Magnetic Resonance Imaging
I. Magnetic Resonance Imaging
Magnetic 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. MRI does not use ionizing radiation (x-rays).
Detailed MR images allow physicians to evaluate various parts of the body
and determine the presence of certain diseases. The images can then be
examined on a computer monitor, transmitted electronically, printed or
copied to a CD. It is based on the principles of nuclear magnetic resonance
(NMR), a spectroscopic technique to obtain microscopic chemical and
physical information about molecules. MRI has advanced beyond a
tomographic imaging technique to a volume imaging technique.
Magnetic resonance imaging (MRI) is a test that uses a magnetic field and
pulses of radio wave energy to make pictures of organs and structures
inside the body. In many cases, MRI gives different information about
structures in the body than can be seen with anX-ray,ultrasound,
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orcomputed tomography (CT) scan. MRI also may show problems that
cannot be seen with other imaging methods.
For an MRI test, the area of the body being studied is placed inside a
special machine that contains a strong magnet. Pictures from an MRI scan
are digital images that can be saved and stored on a computer for more
study. The images also can be reviewed remotely, such as in a clinic or an
operating room. In some cases,contrast materialmay be used during the
MRI scan to show certain structures more clearly.
You may be able to have an MRI with anopen machinethat doesn't
enclose your entire body. But open MRI machines aren't available
everywhere. The pictures from an open MRI may not be as good as those
from astandard MRI machine.
MRI can give different information about structures in the body than can
be obtained using a standard x-ray, ultrasound, or computed tomography
(CT) exam. For example, an MRI exam of a joint can provide detailed images
of ligaments and cartilage, which are not visible using other study types. In
some cases, a magnetically active material (called a contrast agent) is used
to show internal structures or abnormalities more clearly.
In most MRI devices, an electric current is passed through coiled wires to
create a temporary magnetic field around a patients body. (In open-MRI
devices, permanent magnets are used.) Radio waves are sent from and
received by a transmitter/receiver in the machine, and these signals are
used to produce digital images of the area of interest.
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An MRI (or magnetic resonance imaging) scan is a radiology technique that
uses magnetism, radio waves, and a computer to produce images of body
structures. The MRI scanner is a tube surrounded by a giant circular
magnet. The patient is placed on a moveable bed that is inserted into the
magnet. The magnet creates a strong magnetic field that aligns the protons
of hydrogen atoms, which are then exposed to a beam of radio waves. This
spins the various protons of the body, and they produce a faint signal that
is detected by the receiver portion of the MRI scanner. The receiver
information is processed by a computer, and an image is produced.
The image and resolution produced by MRI is quite detailed and can detect
tiny changes of structures within the body. For some procedures, contrast
agents, such as gadolinium, are used to increase the accuracy of the
images.
II. History
Magnetic resonance imaging (MRI) is a sophisticated imaging technique
that has evolved as a clinical modality over the past 30 years. The origins of
MRI, or NMR (nuclear magnetic resonance), as it was termed in the past,
however, can be traced back for over a century. Along the way, many
scientists from diverse disciplines have made remarkable contributions that
have brought the field to its present statea clinical tool capable of real
time in-utero cardiac imaging and a research tool capable of imaging a
single cell. As this powerful imaging modality and scientific tool continues
to evolve, it is worthwhile to pause and look back at the evolution of MRI
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and note the scientists who made the extraordinary contributions that have
led to five Nobel Prizes awarded to discoveries related to NMR/MRI.
By 1975, Peter Mansfield and Andrew Maudsley proposed a line scan
technique, which, in 1977, led to the first image of in vivo human anatomy,
a cross section through a finger. In 1977, Hinshaw, Bottomley, and Holland
succeeded with an image of the wrist and Damadian et al. created a cross
section of a human chest. More human thoracic and abdominal images
followed, and, by 1978, Hugh Clow and Ian R. Young, working at the British
company EMI, reported the first transverse NMR image through a human
head. Two years later, William Moore and colleagues presented the first
coronal and sagittal images through a human head. In 1980, Edelstein et
al. from Aberdeen University in Scotland demonstrated imaging of the body
using Ernsts technique. A single image could be acquired in approximately
five minutes by this technique. By 1986, the imaging time was reduced to
about five seconds without sacrificing too much image quality.
A.Quick History of the MRI
1882 Nikola Tesla discovered the Rotating Magnetic Field in Budapest,
Hungary. This was a fundamental discovery in physics.
1937 Columbia University Professor Isidor I. Rabi working in the Pupin
Physic Laboratory in New York City, observed the quantum phenomenon
dubbed nuclear magnetic resonance (NMR). He recognized that the atomic
nuclei show their presence by absorbing or emitting radio waves when
exposed to a sufficiently strong magnetic field.
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1946 Felix Bloch and Edward Purcell discover magnetic resonance
phenomenon.
1950s Herman Carr creates a one-dimensional MR image.
1956 The "Tesla Unit" was proclaimed in the Rathaus of Munich, Germany
by the International Electro-technical Commission-Committee of Action. All
MRI machines are calibrated in "Tesla Units". The strength of a magnetic
field is measured in Tesla or Gauss Units. The stronger the magnetic field,
the stronger the amount of radio signals which can be elicited from the
body's atoms and therefore the higher the quality of MRI images.
1969 Original Concept; Damadian Conceives of and proposes whole body
MR scanner for the first time.
1970 - Key Discovery Makes MR Scanner Possible; Damadian identifies
T1/T2 differences between cancer and normal. He was seeking an MR
signal difference in an important disease (cancer) that would prove his idea
of an MR body scanner was a goal worth pursuing.
March 1971 First Published Article; Damadian T1/T2 findings and
scanner proposal published inScience, March 19, 1971. High pixel contrast
provided by dramatic T1/T2 differences overcomes x-ray's century-old
inability to see detail in vital organs.
Spring 1971 Scanning Method Proposed; Damadian outlines voxel-by-voxel
scanning method
September 1971 Gradient Method Proposed; Lauterbur notebook proposal
of gradient methods of Gabillard, Purcell & Carr for 1-dimension
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1971 Raymond Damadian, a physician and experimenter working at
Brooklyn's Downstate Medical Center discovered that hydrogen signal in
cancerous tissue is different from that of healthy tissue because tumors
contain more water. More water means more hydrogen atoms. When the
NMR machine was switched off, the bath of radio waves from cancerous
tissue will linger longer then those from the healthy tissue.
1972 MRI adapted for medical purposes; Using highspeed computers,
magnetic resonance imaging (MRI) is adapted for medical purposes, offering
better discrimination of soft tissue than xray CAT and is now widely used
for noninvasive imaging throughout the body. Among the pioneers in the
development of MRI are Felix Bloch and Edward Purcell (Nobel Prize
winners in 1952), Paul Lauterbur, and Raymond Damadian.
March 1972 First Patent Filed; Damadian files '832 patent for 3-dimension
voxel-by-voxel scan method and T1/T2 method.
October 1972 2D Scan (Image) Achieved; Lauterbur submits 2-dimension
MR scan (image) method with scan of 1mm tubes for publication
1972 Raymond Damadian applies for a patent, which describes the concept
of NMR being used for above purpose. He illustrates major parts of MRImachine in his patent application.
March 1973 2D Paper Published; Lauterbur paper published in Nature,
March 16, 1973
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1973 Paul Lauterbur, a chemist and an NMR pioneer at the State University
of New York, Stony Brook, produced the first NMR image. It was of a test
tube.
1974 3D Scan Method Proposed; Garroway, Grannell & Mansfield publish
3-dimension scan method
1974 Raymond Damadian receives his patent.
1975 Phase Coding Introduced; Kumar, Welti & Ernst introduce phase
encoding to scan method
1975 Richard Ernst proposes using phase and frequency encoding and
Fourier transform for acquisition of MR images.
1977 First Human Scan Achieved; Damadian and coworkers, Minkoff and
Goldsmith, achieve first scan (image) of the human body utilizing voxel
method of patent.
1977 Raymond Damadian produces MR image of the whole body. Peter
Mansfield improves mathematics behind MRI and develops echo-planar
technique, which allows images to be produces in seconds and later
becomes the basis for fast MR imaging.
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Figure 1. On July 3, 1977, nearly
five hours after the start of
the first MRI test, the first human
scan was made as the first MRI prototype.
The image above is of Dr. Damadian with the
history- making prototype of
his MRI scanner. This prototype is now on
permanent display at the Smithsonian Institutions Hall of Medical Sciences.
1980Phase Coding Applied; Aberdeen group introduces spin warp method
1980 Phase Coding Applied; Aberdeen group introduces spin warp method
1983 Ljunggren and Tweig introduce k-space.
1986 Le Bihan publishes an article in Radiology, which describes diffusion
weighted imaging (DWI).
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1987 Real time MR imaging of the heart is developed.
1991 Filler and colleagues describe imaging of axonal transport of
supermagnetic metal oxide particles, a technique, which later becomes
important in imaging of neural tracts.
1993 Functional MR imaging of the brain is introduced.
1994 The first intraoperative MR unit developed by GE and Harvard is
installed in the Brigham and Women's Hospital in Boston.
1997 Patent Upheld; High Court on U.S. Patents and U.S. Supreme Court
enforce Damadian '832 patent.
1990s In addition to research centers and large hospitals, small remote
hospitals and imaging centers begin to utilize MRI predominantly for
neuroimaging and musculoskeletal imaging.
2000s Cardiac MRI, Body MRI, fetal imaging, functional MR imaging are
further developed and become routine in many imaging centers. Research
centers make significant strides forward in imaging cartilage on high field
scanners. The number of free standing MRI centers, most of which utilize
low or moderate field MR scanners significantly increases.
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Figure 2. The future of MRI from 2050 2059
2057 The ability to scan, analyse and
diagnose the body has taken a huge
leap forward by now. Hires, 3D
imaging of internal structures and brain activity is now possible using
realtime video, rather than static photos. This can be accomplished with
devices no bigger than a camera or tablet. By the late 2050s, MRI scans
have become as quick and easy as taking a photograph, with a
hundredfold decrease in cost.
Nikola Tesla discovered the Rotating Magnetic Field in 1882 in Budapest,
Hungary.
This was a fundamental discovery in physics.
In 1956, the "Tesla Unit" was proclaimed in the Rathaus of Munich,
Germany by the
International Electrotechnical CommissionCommittee of Action. All MRI
machines
are calibrated in "Tesla Units". The strength of a magnetic field is measured
in Tesla or Gauss Units. The stronger the magnetic field, the stronger the
amount of radio signals
which can be elicited from the body's atoms and therefore the higher the
quality of MRI
images.
1 Tesla = 10,000 Gauss
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LowField
MRI= Under .2 Tesla (2,000 Gauss)
MidField
MRI= .2 to 0.6 Tesla (2,000 Gauss to 6,000 Gauss)
HighField
MRI= 1.0 to 1.5 Tesla (10,000 Gauss to 15,000 Gauss)
In 1937, Columbia University Professor Isidor I. Rabi working in the Pupin
Physic Laboratory in Columbia University, New York City, observed the
quantum phenomenon dubbed nuclear magnetic resonance (NMR). He
recognized that the atomic nuclei show their presence by absorbing or
emitting radio waves when exposed to a sufficiently strong magnetic field.
NUMBER OF MRI MACHINES WOLRDWIDE
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III. Uses and Application of the Procedure
MR imaging of the body is performed to evaluate, diagnose or monitor
treatments for a variety of medical conditions, including: organs of the
chest and abdomenincluding the heart, liver, biliary tract, kidneys,
spleen, bowel, pancreas, and adrenal glands; pelvic organs including the
bladder and the reproductive organs such as the uterus and ovaries in
females and the prostate gland in males; blood vessels (including MR
Angiography); lymph nodes; Abnormalities of the brain and spinal cord;
Tumors, cysts, and other abnormalities in various parts of the body;
Injuries or abnormalities of the joints; Suspected uterine abnormalities in
women undergoing evaluation for infertility
Physicians use an MR examination to help diagnose or monitor treatment
for conditions such as: tumors of the chest, abdomen or pelvis; diseases of
the liver, such as cirrhosis, and abnormalities of the bile ducts and
pancreas; inflammatory bowel disease such as Crohns disease and
ulcerative colitis; heart problems, such as congenital heart disease;
malformations of the blood vessels and inflammation of the vessels
(vasculitis); a fetus in the womb of a pregnant woman.
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An MRI scan can be used as an extremely accurate method of disease
detection throughout the body and is most often used after the other
testing fails to provide sufficient information to confirm a patient's
diagnosis. In the head, trauma to the brain can be seen as bleeding or
swelling. Other abnormalities often found include brain aneurysms,stroke,
tumors of the brain, as well as tumors or inflammation of the spine.
Neurosurgeons use an MRI scan not only in defining brain anatomy but in
evaluating the integrity of the spinal cord after trauma. It is also used when
considering problems associated with the vertebrae or intervertebral discs
of the spine. An MRI scan can evaluate the structure of the heart and
aorta, where it can detect aneurysms or tears. MRI scans are not the first
line of imaging test for these issues or in cases of trauma.
It provides valuable information on glands and organs within the abdomen,
and accurate information about the structure of the joints, soft tissues,
and bones of the body. Often, surgery can be deferred or more accurately
directed after knowing the results of an MRI scan.
IV.Procedure
A.Preparation
The presence of a strong magnetic field means the metal objects of any kind
are not permitted within the scanning room during an MRI Scan. All
jewellery and clothing containing metal, particularly objects containing iron
need to be removed. Internal metal objects such as metal clips, medication
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pumps, or any internal metal items such as shrapnel or metal particles
also present a considerable risk and must be made known to the doctor.
Other equipment that may cause a risk include cardiac pacemakers or
defibrillators; a catheter with metal components; aneurysm clips and
cochlear implants. Some metal implants do not rule out using an MRI
scanner, but some do and it is important to tell a doctor about any
implants or metallic objects. If the patient suspects they may bepregnant,
the doctor must be informed as little is known about the effect of MRI
scans on an unborn baby. To improve the experience of the MRI, it is
advised that the patient not drink for several hours before the scan. This is
especially true of coffee and tea, as going to the toilet is not possible
without interrupting the scan and beginning again.
B.How does it Work?
An MRI scanner is a cylindrical machine, used to get images of the human
body. An MRI machine consists of a round tunnel within where the patientlies on a narrow table. An image of this is seen to the right. Surrounding
the tube is a large cylindrical magnet. During an MRI Scan, the patient is
within a stable magnetic field which is 10,000 30,000 times stronger than
the earths magnetic field. Protons are tiny particles that are present in
water molecules throughout the body. These are aligned by the incredibly
strong magnetic field, noting that there are no water molecules in the
human skeleton, only in bodily tissue. Radio waves are transmitted in
pulses, and these protons produce echoes that are emitted out of the body.
These echoes are received by theMRIscanner, and are then reconstructed
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into images of the body by a computer. These images are very precise and
give a clear anatomical view of the body from any angle.
C.How does MRI performed?
Once you are dressed in a medical gown, you will then be asked to lie down
on a narrow table which then moves into the tunnel. An MRI can last from
30 minutes to an hour, depending on the scans being performed. The scan
consists of sequences, lasting from 2-15 minutes, during which the
machine makes knocking noises, which can be loud. Patients are often
provided with earphones to listen to music to distract them from these
noises during the procedure. It is essential that the patient must remain
motionless in order to produce a clear picture. For some patients
claustrophobia may be an issue as the space within the MRI can be
confining. Subsequently those with claustrophobicanxietyand childrenmay need light sedation. Throughout the procedure imaging technicians are
able to communicate with the patient via intercom to ensure that the
patient is informed and comfortable.
After the MRI scan a radiologist, who is a physician experienced in MRI and
other radiology examinations, will analyze the images and send a report
with his or her interpretation to the patients personal physician. Thepatient receives MRI results from the referring physician who ordered the
test. The image is available almost immediately, but the time from when the
image is made available to when a report is issued will vary depending on
the complexity of the case.
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D.What will you experience after the procedure?
Most MRI exams are painless. However, some patients find it uncomfortableto 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
medication.
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 obtained, which is
typically only a few seconds to a few minutes at a time. You will know when
images are being recorded because you will hear and feel loud tapping or
thumping sounds when the coils that generate the radiofrequency pulses
are activated. Some centers provide earplugs, while others use headphones
to reduce the intensity of the sounds made by the MRI machine. You will be
able to relax between imaging sequences, but will be asked to maintainyour position without movement as much as possible.
In some cases, intravenous injection of contrast material may be
performed. The intravenous needle may cause you some discomfort when it
is inserted and 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 temporary metallic taste in their mouth after
the contrast injection.
V. Benefits and Risk
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A.Benefits
MRI is a noninvasive imaging technique that does not involve exposure to
ionizing radiation. MR images of the soft-tissue structures of the body
such 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.
B.Risk and Disadvantages
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
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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-based contrast material in patients
with very poor kidney function. Careful assessment of kidney function
before considering a contrast injection minimizes the risk of this very rare
complication.
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.
Figure 1 Accidents Happen becauseof strong magnetic Field
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The magnet may cause pacemakers, artificial limbs, and other implanted
medical devices that contain metal to malfunction or heat up during the
exam. Any loose metal object may cause damage or injury if it gets pulled
toward the magnet. If a contrast agent is used, there is a slight risk of an
allergic reaction. MRI contrast agents can cause problems in patients with
significant kidney disease. Dyes from tattoos or tattooed eyeliner can cause
skin or eye irritation. Medication patches can cause a skin burn. The wire
leads used to monitor an electrocardiogram (ECG) trace or respiration
during a scan must be placed carefully to avoid causing a skin burn.
Prolonged exposure to radio waves during the scan could lead to slight
warming of the body.
Here is a news about an accident happens in MRI session.
Aug. 1, 2001 -- Despite the horrific MRI accident that caused the death of
6-year-old Michael Colombini earlier this week in Valhalla, N.Y., many
medical experts reiterate that the use of the imaging test is safe when used
appropriately. Colombini was undergoing an MRI, or magnetic resonance
imaging, at Westchester County Medical Center last Friday when an oxygen
canister was turned into a guided missile by the powerful MRI magnet. The
canister was drawn into the magnet core while the boy was in the machine.
The result was a fatal blow to the child's head. He died on Sunday. Frank
Shellock, MD, an MRI safety expert who has been tracking MRI-related
accidents for 16 years tells WebMD that this is the first death caused by an
MRI projectile, and that any kind of MRI accident is "relatively rare." MRIs
have been used regularly by doctors since "1982, and it is estimated that
about 10 million MRI imaging studies are done in the United States each
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year," says Shellock, who is a clinical professor of radiology at the
University of Southern California. 2001 WebMD, Inc. All rights reserved.
VI.Limitation
High-quality images are assured only if you are able to remain perfectly still
and follow breath-holding instructions 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.
The presence of an implant or other metallic object sometimes makes it
difficult to obtain clear images. Patient movement can have the same effect.A very irregular heartbeat may affect the quality of images obtained using
techniques that time the imaging based on the electrical activity of the
heart, such as electrocardiography (EKG).
An MRI is a very expensive and time consuming investigation compared to
other methods such asx-rayandCT. Some parts of the body, like bone, are
better examined using simpler techniques such as an X-Ray. An MRI may
not always be able to tell the difference between some disease processes. It
is also not a very good investigation for emergencies or accidents because of
the long time it takes and the fact that all equipment has to be removed
from the room while the machine is running.
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VII. The equipment
A.Appearance and Process
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, calledshort-bore systems, are designed so that the
magnet does not completely surround you. Some newer MRI machines have
a larger diameter bore which can be more comfortable for larger size
patients or patients with claustrophobia. Other MRI machines are open on
the sides (open MRI). Open units are especially helpful for examining larger
patients or those with claustrophobia. Newer open MRI units provide very
high quality images for many types of exams; however, older open MRI
units 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.
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Figure 1: Picture of MRI Equipment Figure 2: Siemens Allegra 3T
Figure 3: A schematic representation
of the major systems on a
magnetic resonance imager.
B.Comparison to other Imaging Equipment
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 alignment of hydrogen atoms that naturally
exist within the body without causing any chemical changes in the tissues.
As the hydrogen atoms return to their usual alignment, they emit energy
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that varies according to the type of body tissue in which they lie. The MR
scanner listens for this energy and creates a picture of the tissues scanned.
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. 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.
VIII.Types of MRI
A.Magnetic Resonance Angiogram(MRA)
An MRA, or magnetic resonance angiogram, is a type ofMRI scanthat uses
MRI's magnetic fields and radio waves to produce pictures of blood vessels
inside the body, allowing doctors to locate problems that may cause
reduced blood flow. An MRI, or magnetic resonance imaging, is the
technology behind an MRA, and it is used to examine soft ligament tissues
and tendon injuries. Both scans are generally safe for most patients and do
not expose them toionizing radiation.
B. Functional MRI
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This type of MRI is done on the brain, and not only shows the structure of
the brain, but also how much activity is taking place in each part. This has
been used to find out what parts of the brain are most active during certain
situations or tasks.Cardiac MRI: This can be used for several different
conditions and is dealt with separately.
Types of MRI Exams
Brain MRI
An MRI of the brain produces very detailed pictures of the brain. It is
commonly used
to study patients with headaches, seizures, weakness, blurry vision, etc. It
also can
further evaluate an abnormality seen on a CT scan. During the brain MRI,
a special
device called a head coil is placed around the patient's head. It does not
touch the
patient, and the patient can see through large gaps in the coil. This device
is what
helps to produce the very detailed pictures of the brain.
Cardiac MRI
Cardiac MRI can evaluate the size and thickness of the chambers of the
heart, the extent of damage caused by a heart attack or progressive heart
disease, and buildup of plaque and blockages in the blood vessels. It is an
invaluable tool for detecting and evaluating coronary artery disease and the
function of the heart muscles, valves and vessels.
http://www.myvmc.com/investigations/cardiac-mri-magnetic-resonance-imaging/http://www.myvmc.com/investigations/cardiac-mri-magnetic-resonance-imaging/ -
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Spine MRI
This test is most commonly used to look for a herniated disc or narrowing
of the spinal canal (spinal stenosis) in patients with neck, arm, back
and/or leg pain. It is also the best test to look for a recurrent disc
herniation in a patient who has had prior back surgery.
Bone and Joint MRI
MRI can evaluate virtually all of the bones and joints, as well as the soft
tissues. Tendon, ligament, muscle, cartilage and bone injuries can be
diagnosed using MRI scans. It can also be used to look for infections and
masses.
Abdomen MRI
MRI of the abdomen is most frequently used to further evaluate an
abnormality seen on another test, such as an ultrasound or CT scan. Thus,
the exam is usually tailored to look at specific organs or tissues, such as
the liver, adrenal glands or pancreas.
Pelvic MRI
For women, pelvic MRI is used to evaluate the ovaries and uterus as
followup to an ultrasound exam which showed an abnormality. It is also
used to evaluate endometrial cancer. For men, pelvic MRI is sometimes
used to evaluate prostate cancer.
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Magnetic Resonance Imaging (MRI) Magnetic Resonance Andiography(MRA)
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IX. Microscopic Property Responsible for MRI
A.Basic Concepts and Basic Anatomy of an MRI System
The Static Magnetic Field
Magnetic resonance imaging requires a very strong magnetic field that has
precisely the same magnitude and direction everywhere in the region we
want to image. Uniformity or homogeneity is one of key properties to
describe MRI system quality. The strength of the magnetic field can be
difficult to understand because we rarely encounter strong magnetic field in
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everyday life. We use unit of gauss (G) or tesla (T), where 10000 gauss is
equal to 1 tesla, to describe the strength of the field.
The basic concept used both for creating the magnetic fields we need for
MRI and detecting the MR signal is that if we run an electrical current
through a wire, then a magnetic field is created around the wire. For the
design of MRI systems, this idea is extended further by wrapping wires in
repeated loops along the surface of a cylinder, which makes the magnetic
field stronger and more uniform over a larger volume at the center of the
cylindrical coil of wire.
Magnetic Field Gradient
A gradient in the magnetic field is what will allow us to accomplish this. A
magnetic field gradient is a variation in the magnetic field with respect to
position. A one-dimensional magnetic field gradient is a variation with
respect to one direction, while a two-dimensional gradient is a variation
with respect to two. The most useful type of gradient in magnetic resonance
imaging is a one- dimensional linear magnetic field gradient. A one-
dimensional magnetic field gradient along the x axis in a magnetic field, Bo,
indicates that the magnetic field is increasing in the x direction. Here the
length of the vectors represents the magnitude of the magnetic field. The
symbols for a magnetic field gradient in the x, y, and z directions are Gx, Gy,
and Gz.
Representing Images with Numbers and Vice-Versa
Digital Imaging and Communications in Medicine
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Digital Imaging and Communications in Medicine (DICOM) is a standard for
handling, storing, printing, andtransmittinginformation inmedical
imaging. It includes afile formatdefinition and a networkcommunications
protocol. The communication protocol is an application protocol that
usesTCP/IPto communicate between systems. DICOM files can be
exchanged between two entities that are capable of receiving image and
patient data in DICOM format.
A DICOM data object consists of a number of attributes, including items
such as name, ID, etc., and also one special attribute containing the image
pixel data (i.e. logically, the main object has no "header" as such: merely a
list of attributes, including the pixel data). A single DICOM object can have
only one attribute containing pixel data. For many modalities, this
corresponds to a single image. But note that the attribute may contain
multiple "frames", allowing storage of cine loops or other multi-frame data.
X. Bibliography and References
https://en.wikipedia.org/wiki/Data_transmissionhttps://en.wikipedia.org/wiki/Medical_imaginghttps://en.wikipedia.org/wiki/Medical_imaginghttps://en.wikipedia.org/wiki/File_formathttps://en.wikipedia.org/wiki/Communications_protocolhttps://en.wikipedia.org/wiki/Communications_protocolhttps://en.wikipedia.org/wiki/TCP/IPhttps://en.wikipedia.org/wiki/Data_transmissionhttps://en.wikipedia.org/wiki/Medical_imaginghttps://en.wikipedia.org/wiki/Medical_imaginghttps://en.wikipedia.org/wiki/File_formathttps://en.wikipedia.org/wiki/Communications_protocolhttps://en.wikipedia.org/wiki/Communications_protocolhttps://en.wikipedia.org/wiki/TCP/IP -
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Magnetic Resonance Imaging (MRI) pages 1-8, Radiological Society of North
America, Inc.
Basic Principles of MRI, Simply Physics, simplyphysics.com
Magnetic Resonance Imaging: Historical Perspective,Journal of
Cardiovascular Magnetic Resonance(2006) 8, 573580 Copyright c_ 2006
Taylor & Francis Group, LLC
Basic Principles of MRI, James Voyvodic, Ph.D., Brain Imaging and
Analysis Center
Radiologyinfo.org, a resource produced by American College of Radiology
and Radiological Society of North America. Magnetic Resonance Imaging
-Body (MRI) Accessed 2/14/2014.
Food and Drug Administration, Radiation-Emitting Products: MRI
(Magnetic Resonance Imaging) Accessed 2/14/2014.
Copyright 1995-2014, The Cleveland Clinic Foundation.
Reimer P, Parizel PM, Stichnoth FA. Clinical MR Imaging: a Practical
Approach (2ndEdition). Heidelberg. Springer-Verlag. 2003.
Hornak, JP. The Basics of MRI. The Centre of Imaging Science. 2006.
July 1, 2015.http://www.cis.rit.edu/htbooks/mri/
Chernoff D, Stark P. Principles of Magnetic Resonance Imaging, UpToDate.
July 1, 2015.http://www.uptodate.com/contents/principles-of-magnetic-
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resonance-imaging?
source=search_result&search=principles+of+magnetic+resonance+imaging
&selectedTitle=1~150
Magnetic Resonance Imaging: Body, Radiology Info. Radiological Society of
North America, 2006. July 1, 2015.http://www.radiologyinfo.org/
http://www.qmagnets.com/magnetic-field-gradients.php
http://www.uptodate.com/contents/principles-of-magnetic-resonance-imaging?source=search_result&search=principles+of+magnetic+resonance+imaging&selectedTitle=1~150http://www.uptodate.com/contents/principles-of-magnetic-resonance-imaging?source=search_result&search=principles+of+magnetic+resonance+imaging&selectedTitle=1~150http://www.uptodate.com/contents/principles-of-magnetic-resonance-imaging?source=search_result&search=principles+of+magnetic+resonance+imaging&selectedTitle=1~150http://www.radiologyinfo.org/http://www.qmagnets.com/magnetic-field-gradients.phphttp://www.uptodate.com/contents/principles-of-magnetic-resonance-imaging?source=search_result&search=principles+of+magnetic+resonance+imaging&selectedTitle=1~150http://www.uptodate.com/contents/principles-of-magnetic-resonance-imaging?source=search_result&search=principles+of+magnetic+resonance+imaging&selectedTitle=1~150http://www.radiologyinfo.org/http://www.qmagnets.com/magnetic-field-gradients.php
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