Common Medical Imaging Procedures
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What is radiography?
x-rays are sent through the body and casts shadows, which is what a picture is taken of.
A single barrage of x-rays passes through the body producing an image of interior structures on x-ray sensitive film. The resulting 2D image is called a radiogragh, or x-ray.
What are the benefits and drawbacks of radiography?
- Relatively inexpensive, quick, and simple to perform; usually provides sufficient information for diagnosis.
- X-rays do not easily pass through dense structures, so bones appear white. Hollow structures, such as the lungs, appear black. Structures of intermediate density, such as skin, fat, and muscle, appear as varying shades of gray.
- At low doses, x-rays are useful for examining soft tissues such as the breast (mammography) and for determining bone density (bone densitometry).
What is a contrast medium (radiography).
Substance that makes hollow or fluid filled structures visible on an x-ray; it can be introduced by an injection, suppository, or oral means.
What are the common uses of contrast x-rays?
Image blood vessels (angiography),
the urinary system (intravenous urography),
- and the gastrointestinal tract
- (barium contrast x-ray).
What is magnetic resonance imaging (MRI)?
Uses magnetism to create a 3d image. Usually a contrast medium is required. Lasts 30-60mins.
- The body is exposed to a high-energy magnetic field, which causes protons in body fluids and tissues to arrange themselves in relation to the field. Then a pulse of radio waves “reads” these ion patterns, and a color-coded image is
- assembled on a video monitor. The result is a two- or three-dimensional blueprint of cellular chemistry.
What are the advantages/disadvantages as well as uses of an MRI?
- Relatively safe, but cannot be used on patients with metal in their bodies.
- Shows fine details for soft tissues but not for bones.
- Most useful for differentiating between normal and abnormal tissues.
- Used to detect tumors and artery-clogging fatty plaques; reveal brain abnormalities; measure blood flow; and detect a variety of musculoskeletal, liver, and kidney disorders.
What is diffusion tensor imaging (DTI)?
A variation of an MIR that provides an image of the brains white matter.
Diffusion tensor imaging (DTI) is a variation of MRI that tracks the movement of water molecules along the length of axons, long processes of nerve cells that form the white matter in the brain. The white matter is organized into bundles of axons called tracts that connect one part of the brain with another. DTI provides images of the brain’s white matter.
What are the uses of a DTI?
- Used in the diagnosis of addictions,
- brain tumors,
- traumatic brain injury,
- multiple sclerosis,
- and neurodegenerative diseases.
What is computed tomography (CT)?
A CT scanner takes many x-rays of a person and uses a computer to generate a 3d image. Usually a contrast medium is required.
In this form of computer-assisted radiography, an x-ray beam traces an arc at multiple angles around a section of the body. The resulting transverse section of the body, called a CT scan, is shown on a video monitor.
What are the uses to a CT scan?
Main use: examine tissue density.
- Visualizes soft tissues and organs with much more detail than conventional radiographs.
- Multiple scans can be assembled to build three-dimensional views of structures (described next).
- Whole-body CT scanning typically targets the torso and appears to provide the most benefit in screening for lung cancers, coronary artery disease, and kidney cancers.
What is a coronary computed tomography angiography (CCTA)?
A form of CT scan that creates a 3d image of the coronary (heart) blood vessels.
- In this form of computer-assisted radiography, an iodine-containing contrast medium is injected into a vein and a beta-blocker is given
- to decrease heart rate. Then, numerous x-ray beams trace an arc around the heart and a scanner detects the x-ray beams and transmits them to a computer, which transforms the information into a three-dimensional image
- of the coronary blood vessels on a monitor.
What is ultrasound scanning?
- High-frequency sound waves produced by a handheld wand reflect off body tissues and are detected by the same instrument.
- The image, which may be still or moving, is called a sonogram (SON-o ̄ -gram) and is shown on a video monitor.
What are the benefits and common uses of ultrasound?
- Safe, noninvasive, painless, and uses no dyes.
- Most commonly used to visualize the fetus during pregnancy.
- Also used to observe the size, location, and actions of organs and blood flow through blood vessels (Doppler ultrasound).
What is endoscopy?
- Endoscopy involves the visual examination of the inside of body organs or cavities using a lighted instrument with lenses called an endoscope.
- The image is viewed through an eyepiece on the endoscope or projected onto a monitor.
What are the uses of a CCTA scan?
- Used primarily to determine if there are any coronary artery blockages (for example, atherosclerotic plaque or calcium) that may require an intervention such as angioplasty or stent.
- The CCTA scan can be rotated, enlarged, and moved at any angle.
- The procedure can take thousands of images of the heart within the time of a single heartbeat, so it provides a great amount of detail about the heart’s structure and function.
What is a positron emission tomography scan used for? (PET scan)
To provide a visual colorized image of an organs activity such as the brain.
Used to study the physiology of body
structures, such as metabolism in the brain or heart.
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