Fluoroscopy Intro to EQUIPMENT and PHYSICS

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Fluoroscopy Intro to EQUIPMENT and PHYSICS

• Rad T 290
• SPRING 2013
• Week 9

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Topics

• Types of fluoroscopy systems
• Viewing the image
• Anatomy physiology of the eye
• Review of radiation physics

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FLUOROSCOPY

• Primary function real-time, dynamic, motion
  studies of anatomic structures.
• Motion of circulation or internal structures.
• Evolution of Fluoroscopy
• Conventional
• Image Intensified
• Digital

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Fluoroscope

• 1898 by Thomas Edison

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DIRECT FLUOROSCOPY

• Early fluoroscopy the image was viewed directly
  the xray photons struck the fluoroscopic screen
  emitting light.
• The higher kVp brighter the light
• Advantage excellent resolution
• Disadvantages
• Only one person can view image
• Room need complete darkness
• Patient dose ( radiologist) was very high

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Direct Fluoroscopy
In older fluoroscopic examinations radiologist
stands behind or looks into a screen and view
the picture Radiologist receives high exposure
despite protective glass, lead shielding in
stand, apron and perhaps goggles
Main source staff exposure is NOT the patient but
direct beam
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Conventional old Fluoroscopy systems
15 - 30 min for dark adaptation RODS or CONES
Vision?
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Red goggles for dark adaptation

• Fluoroscopy was performed in total darkness
• The eyes had to be adjusted for 15 - 30 minutes
• by wearing red goggles

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Human Vision

• Light passes through the lens, where light is
  focused onto the retina.
• Between the cornea and the lens is the iris,
  which acts like a camera diaphragm controls the
  amount of light admitted into the eye

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CORNEA

• The cornea is a thin transparent protective
  covering that protects the eye.
• It has no blood vessels and it helps focus light
  onto the retina
• Light rays bounce off all objects. If a person is
  looking at a particular object, such as a tree,
  light is reflected off the tree to the person's
  eye and enters the eye through the cornea

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IRIS

• located between the cornea and the lens
• colored part of the eye
• It controls the amount of light that is admitted
  to the eye by dilating or constricting the pupil.
  
• Bright light causes contraction of the iris
  allowing only a small amount of light to hit the
  pupil
• In dim light, the pupil enlarges to allow more
  light to enter the eye.

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Lens Pupil

• focuses the light that passes through the pupil
  onto the retina where the light receptors are
  located
• The pupil is the opening to the eye. As the iris
  opens and closes, it causes the pupil to dilate
  or contract.
• Light has to pass through the pupil to reach the
  retina

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The Retina

• The retina is important because it contains the
  rods and cones.
• rods and cones are specialized photoreceptor
  cells called
• That convert light rays into electrical signals
  that transmitted to the brain through the optic
  nerve.

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The Retina

• The sharpest point of vision is located in the
  center in an area called the fovea centralis.
• Rods see in dim light and
• Cones provide the ability to see in color

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• Fovea centralis the
• central part of retina
• Cones tightly packed
• Remainder cones dimish more rods

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The rods

• These are located at the periphery of the retina
• There are fewer of them and they are sensitive to
  low levels of light.
• Night vision (scotopic vision) uses the rods of
  the eye to see
• The rods are colorblind

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The cones

• Cones are located at the center of the retina in
  the fovea centralis
• They respond to intense light levels. As such,
  these are used for our daylight (phototropic
  vision).
• Cones have better visual acuity and better
  contrast perception.
• Cones perceive color

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Visual Physiology 2 types of light receptors

• CONES
• Daylight
• Photopic
• Percieve color
• Center of retina
• Better visual acuity
• II much brighter

• RODS
• Night vision
• Scotopic
• Perceive grays
• Periphery of retina dim objects seen better
  1000 x more sensitive
• 30 min dark adaptation

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VISUAL ACUITY

• ABILITY TO PERCEIVE FINE DETAILS
• INTEGRATION TIME 0.2 SEC (how long it takes to
  identify something)
• Photopic acuity is 10 x greater than scotopic
• Contrast perception is our ability to detect
  differences in brightness
• Normal viewing distance 12 15 inches

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Fluoroscopy

• X-ray transmitted trough patient
• The photographic plate replaced by fluorescent
  screen
• Screen fluoresces under irradiation and gives a
  life picture
• Older systems direct viewing of screen
• Nowadays screen part of an Image Intensifier
  system
• Coupled to a television camera
• Radiologist can watch the images live on
  TV-monitor images can be recorded
• Fluoroscopy often used to observe digestive tract
• Upper GI series, Barium Swallow
• Lower GI series Barium Enema

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Early Image Intensified FLUORO

• Types of Equipment
• C-arm
• Stationary, mobile, mini
• Under table/over table units

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IMAGE INTENSIFICAITON

• IMAGES ARE VIEWED ON A TV SCREEN/MONITOR

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Remote over the table tube
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Different fluoroscopy systems

• Remote control systems
• Not requiring the presence of medical specialists
  inside the X Ray room
• Mobile C-arms
• Mostly used in surgery

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C-ARM UNIT -STATIONARY
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MOBILE C-ARM UNIT
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Mini c-arm
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Conventional II system
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NEWER SYSTEMS DIGITAL FLUORO
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Basic Componets of old Fluoroscopy Imaging
Chain
Primary Radiation
EXIT Radiation
Fluoro TUBE
PATIENT
105 Photospot
Fiber Optics OR
Image Intensifier
ABC
LENS SPLIT
Cassette
Image Recording Devices
CINE
CONTROL UNIT
VIDICON Camera Tube
TV
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Review of Radiation Physics