Diagnostic Methods: Ultrasound, CT, and MRI

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Diagnostic Methods Ultrasound, CT, and MRI
Prepared by- Md. Bashir Uddin Assistant
Professor Dept. of BME KUET, Khulna-9203
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Diagnostic Methods

• In medicine, a diagnostic test or method is any
  kind of medical test performed to aid in the
  diagnosis or detection of disease.
• For example, such a test may be used to confirm
  that a person is free from disease, or to fully
  diagnose a disease, including to sub-classify it
  regarding severity and susceptibility to
  treatment.
• Some of diagnostic methods are
• Ultrasound Imaging
• CT Scan
• MRI
• etc

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Ultrasound

• Ultrasound is an oscillating sound pressure wave
  with a frequency greater than the upper limit of
  the human hearing range
• Ultrasound devices operate with frequencies from
  20 kHz up to several gigahertz.
• Ultrasound is used in many different fields, such
  as-
• To detect objects and measure distances
• In Ultrasonic imaging (sonography)
• In Nondestructive testing of products and
  structures
• To detect invisible flaws
• In Cleaning and mixing
• Locating prey and obstacles
• To change the chemical properties of substances

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Ultrasound
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Ultrasound Imaging

• Ultrasound is safe and painless, and produces
  pictures of the inside of the body using sound
  waves.
• Ultrasound imaging, also called ultrasound
  scanning or sonography, involves the use of a
  small transducer (probe) and ultrasound gel
  placed directly on the skin.
• High-frequency sound waves are transmitted from
  the probe through the gel into the body.

• The transducer collects the sounds that bounce
  back and a computer then uses those sound waves
  to create an image.

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Ultrasound Imaging

• Ultrasound examinations do not use ionizing
  radiation (as used in x-rays), thus there is no
  radiation exposure to the patient. Because
  ultrasound images are captured in real-time, they
  can show the structure and movement of the body's
  internal organs, as well as blood flowing through
  blood vessels.
• Ultrasound imaging is a noninvasive medical test
  that helps physicians diagnose and treat medical
  conditions

• Ultrasound is used to help physicians evaluate
  symptoms such as
• pain
• swelling
• infection

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Ultrasound Imaging
Ultrasound is a useful way of examining many of
the body's internal organs, including but not
limited to the

• Liver
• Gallbladder
• Spleen
• Pancreas
• Kidneys
• Bladder
• heart and blood vessels
• thyroid and parathyroid glands
• uterus, ovaries, and unborn child (fetus) in
  pregnant

• Patients
• Eyes
• scrotum (testicles)
• brain in infants
• hips in infants

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Ultrasound Imaging

• Benefits
• Most ultrasound scanning is noninvasive (no
  needles or injections).
• Occasionally, an ultrasound exam may be
  temporarily uncomfortable, but it is almost never
  painful.
• Ultrasound is widely available, easy-to-use and
  less expensive than other imaging methods.
• Ultrasound imaging is extremely safe and does not
  use any ionizing radiation.
• Ultrasound scanning gives a clear picture of soft
  tissues that do not show up well on x-ray images.
• Ultrasound is the preferred imaging modality for
  the diagnosis and monitoring of pregnant women
  and their unborn babies.
• Ultrasound provides real-time imaging, making it
  a good tool for guiding minimally invasive
  procedures such as needle biopsies and fluid
  aspiration

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Ultrasound Imaging

• Limitations
• Ultrasound waves are disrupted by air or gas
  therefore ultrasound is not an ideal imaging
  technique for air-filled bowel or organs obscured
  by the bowel. In most cases, barium exams, CT
  scanning, and MRI are the methods of choice in
  such a setting.
• Large patients are more difficult to image by
  ultrasound because greater amounts of tissue
  attenuates (weakens) the sound waves as they pass
  deeper into the body.
• Ultrasound has difficulty penetrating bone and,
  therefore, can only see the outer surface of bony
  structures and not what lies within (except in
  infants who have more cartilage in their
  skeletons than older children or adults). For
  visualizing internal structure of bones or
  certain joints, other imaging modalities such as
  MRI are typically used.

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Computerized Tomography (CT)

• Computerized/Computed tomography (CT scan) also
  called CT or x-ray CT combines a series of
  X-ray views taken from many different angles and
  computer processing to create cross-sectional
  images of the bones and soft tissues inside your
  body.
• In some cases, CT images can be combined to
  create 3-D images.
• CT scan images can provide much more information
  than do plain X-rays.
• A CT scan has many uses, but is particularly well
  suited to quickly examine people who may have
  internal injuries from car accidents or other
  types of trauma.
• A CT scan can be used to visualize nearly all
  parts of the body.

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Computerized Tomography (CT)

• X-ray computed tomography (x-ray CT) is a
  technology to produce tomographic images (virtual
  'slices') of specific areas of the scanned
  object, allowing the user to see inside without
  cutting.
• Medical imaging is the most common application of
  x-ray CT. Its cross-sectional images are used for
  diagnostic and therapeutic purposes in various
  medical disciplines.
• As x-ray CT is the most common form of CT in
  medicine and various other contexts, the term
  computed tomography alone (or CT) is often used
  to refer to x-ray CT, although other types exist
  (such as positron emission tomography PET and
  single-photon emission computed tomography
  SPECT).
• Older and less preferred terms that also refer to
  x-ray CT are computed axial tomography (CAT scan)
  and computer-aided/assisted tomography.

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Computerized Tomography (CT)
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Computerized Tomography (CT)

• Advantages
• There are several advantages that CT has over
  traditional 2D medical radiography.
• First, CT completely eliminates the
  superimposition of images of structures outside
  the area of interest.
• Second, because of the inherent high-contrast
  resolution of CT, differences between tissues
  that differ in physical density by less than 1
  can be distinguished.
• Finally, data from a single CT imaging procedure
  consisting of either multiple contiguous or one
  helical scan can be viewed as images in the
  axial, coronal, or sagittal planes, depending on
  the diagnostic task. This is referred to as
  multiplanar reformatted imaging.
• Adverse Effect
• The radiation used in CT scans can damage body
  cells, including DNA molecules, which can lead to
  cancer.

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Magnetic Resonance Imaging (MRI)

• Magnetic resonance imaging (MRI) is a technique
  that uses a magnetic field and radio waves to
  create detailed images of the organs and tissues
  within your body.
• Most MRI machines are large, tube-shaped magnets.
  When you lie inside an MRI machine, the magnetic
  field temporarily realigns hydrogen atoms in your
  body. Radio waves cause these aligned atoms to
  produce very faint signals, which are used to
  create cross-sectional MRI images like slices
  in a loaf of bread.
• The MRI machine can also be used to produce 3-D
  images that may be viewed from many different
  angles.
• In many cases, MRI gives different information
  about structures in the body than can be seen
  with an X-ray, ultrasound, or computed tomography
  (CT) scan. MRI also may show problems that cannot
  be seen with other imaging methods.

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Magnetic Resonance Imaging (MRI)

• Magnetic resonance imaging (MRI) is done for many
  reasons. It is used to find problems such as
  tumors, bleeding, injury, blood vessel diseases,
  or infection.
• MRI also may be done to provide more information
  about a problem seen on an X-ray, ultrasound
  scan, or CT scan.
• Contrast material may be used during MRI to show
  abnormal tissue more clearly.
• An MRI scan can be done for the

• Head
• Chest
• Blood vessels

• Abdomen and pelvis
• Bones and joints
• Spine

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Magnetic Resonance Imaging (MRI)

• It is a noninvasive diagnostic scanning technique
• MRI provides a better contrast between normal and
  abnormal tissue than the CT scan.
• The procedure lasts between 60 and 90 minutes.

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Magnetic Resonance Imaging (MRI)

• Benefits
• Provide very detailed diagnostic pictures of most
  of the important organs and tissues in body
• Sometimes able to show unique information that
  other tests are unable to show
• Generally painless
• Do not use radiation and are therefore suitable
  for use in children and pregnant women.
• Risks
• Safety studies have found no long-term negative
  effects from MRI scans.
• MRI scan is done in an enclosed space, so the
  people who are claustrophobic, i.e. fearful of
  being in a closely enclosed surface, are facing
  problems with MRI to be done.
• MRI scans involve really loud noises while
  processing because they involve a really high
  amount of electric current supply.
• MRI scans can cause heart pacemakers,
  defibrillation devices and cochlear implants to
  malfunction.

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