TEXT PART
In clinical practice medical imaging is a crucial component of a large number of
applications. Usually not only one image modality (imaging device) is used but several
(like Computed Tomography, Magnetic Resonance Imaging, Angiography, Ultrasound,
or the real patient), providing different kinds of information to physicians. Moreover,
medical image data acquired during diagnosis is often used to aid in operations and
intraoperative images are revised for follow-up.
CT Introduction
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CT or CAT scans are special x-ray tests that produce cross-sectional images of the body using xrays and a computer. These images allow the radiologist, a medical doctor who specializes in
images of the body, to look at the inside of the body just as you would look at the inside of a loaf
of bread by slicing it. This type of special x-ray, in a sense, takes "pictures" of slices of the body
so doctors can look right at the area of interest. CT scans are frequently used to evaluate the brain,
neck, spine, chest, abdomen, pelvis, and sinuses.
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CT has become a commonly performed procedure. Scanners are found not only in hospital x-ray
departments, but also in outpatient offices.
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CT has revolutionized medicine because it allows doctors to see diseases that, in the past, could
often only be found at surgery or at autopsy. CT is noninvasive, safe, and well-tolerated. It
provides a highly detailed look at many different parts of the body.
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If you are looking at a standard x-ray image or radiograph (such as a chest x-ray), it appears as if
you are looking through the body. CT and MRI are similar to each other, but provide a different
view of the body than an x-ray does. CT and MRI produce cross-sectional images that appear to
open the body up, allowing the doctor to look at it from the inside. MRI uses a magnetic field and
radio waves to produce images, while CT uses x-rays to produce images. Plain x-rays are an
inexpensive, quick exam and are accurate at diagnosing things such as pneumonia, arthritis, and
fractures. CT and MRI better evaluate soft tissues such as the brain, liver, and abdominal organs,
as well as look for subtle abnormalities that may not be apparent on regular x-rays.
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People often have CT scans to further look at an abnormality seen on another test such as an x-ray
or an ultrasound. They may also have a CT to check for specific symptoms such as pain or
dizziness. People with cancer may have a CT to look for the spread of disease.
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A head or brain CT examines the various structures of the brain to look for a mass, stroke, area of
bleeding, or blood vessel abnormality. It is also sometimes used to look at the skull.
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A neck CT checks the soft tissues of the neck and is frequently used to study a lump or mass in the
neck or to look for enlarged lymph nodes or glands.
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CT of the chest is frequently used to further study an abnormality on a plain chest x-ray. It is also
often used to look for enlarged lymph nodes.
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Abdominal and pelvic CT looks at the abdominal and pelvic organs (such as the liver, spleen,
kidneys, pancreas, and adrenal glands) and the gastrointestinal tract. These studies are often
ordered to check for a cause of pain and sometimes to follow up on an abnormality seen on
another test such as an ultrasound.
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A sinus CT exam is used to both diagnose sinus disease and to look for a narrowing or obstruction
in the sinus drainage pathway.
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A spine CT test is most commonly used to look for a herniated disc or narrowing of the spinal
canal (spinal stenosis) in people with neck, arm, back, and/or leg pain. It is also used to look for a
fracture or break in the spine.
MRI Introduction

A magnetic resonance imaging scan, or an MRI, is similar to a CT scanner in that it produces
cross-sectional images of the body. Looking at the body in cross section is like looking at the
inside of a loaf of bread by slicing it. Unlike a CT scan, MRI does not use x-rays. It uses a strong
magnetic field and radio waves to produce very clear and detailed images of the inside of the body
on a computer. MRI is commonly used to examine the brain, spine, joints, abdomen, and pelvis. A
special kind of MRI exam, called magnetic resonance angiography (MRA), examines the blood
vessels.
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An MRI of the brain produces very detailed pictures of the brain. It is commonly used to study
patients with such problems as headaches, seizures, weakness, hearing loss, and blurry vision.
It can also be used to further evaluate an abnormality seen on a CT scan. During a 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.
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Spine MRI 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.
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Bone and joint MRI can check virtually all of the bones and joints, as well as the soft tissues.
Injured tendons, ligaments, muscles, cartilage, and bone can be diagnosed by MRI. It also can be
used to look for infections and masses.
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MRI of the abdomen is most frequently used to further look at an abnormality seen on another
test, such as an ultrasound or CT scan. The exam is usually tailored to look just at the liver,
adrenal glands, or pancreas.
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For women, pelvic MRI provides a detailed look at the ovaries and uterus and is often used to
follow up an abnormality seen on ultrasound. It is also used to evaluate the spread of cancer of the
uterus. For men, pelvic MRI is sometimes used to check patients with prostate cancer. MRI is also
used to look at the bones and muscles of the pelvis.
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Magnetic resonance angiography (MRA) looks at blood vessels. The blood vessels in the neck
(carotid and vertebral arteries) and brain are frequently studied by MRA to look for areas of
narrowing or dilatation (widening). In the abdomen, the arteries supplying blood to the kidneys are
also frequently looked at with this technique.
introduction to ultrasound
Medical ultrasound, also called sonography, is a mode of medical imaging that has a wide array of clinical
applications, both as a primary modality and as an adjunct to other diagnostic procedures. The basis of its
operation is the transmission of high frequency sound into the body followed by the reception, processing,
and parametric display of echoes returning from structures and tissues within the body. Ultrasound is
primarily a tomographic modality, meaning that it presents an image that is typically a cross-section of the
tissue volume under investigation. It is also a soft-tissue modality, given that current ultrasound
methodology does not provide useful images of or through bone or bodies of gas, such as found in the lung
and bowel. Its utility in the clinic is in large part due to three characteristics. These are that ultrasound a) is
a real-time modality, b) does not utilize ionizing radiation, and c) provides quantitative measurement and
imaging of blood flow.
NUCLEAR MEDICINE INTRODUCTION
In nuclear medicine, imaging is performed by a gamma camera. A radioactive agent is infused into the
patient's blood. The concentrations of the agent in the various organs emit gamma rays which are mapped
by the camera heads and converted to electrical signals. These acquired signals are presented as images on
the display console. Modern high-performance gamma cameras are equipped with two detector heads, and,
moreover, are able to perform in two imaging modes: Whole-body scanning, where the data is acquired
along the entire length of the patient's body; and SPECT, where the detectors rotate around the patient
acquiring data that is reconstructed into tomographic images.