Transcript Introduction to Angiographic Procedures and Equipment

Introduction to
Angiographic
Procedures and
Equipment
RAD TECH 255
SP 2007
Carltons – CH 42
ANGIOGRAPHY
• RADIOGRAPHIC EXAM
OF THE ARTERIES
USING CONTRAST
MEDIA
Special Procudures –
Sterile Environment (like OR)
Some history….
• The first angiogram was performed
only months after Roentgen's
discovery,
• when two physicians injected chalk
into an amputated hand
• and created an image of the
arteries
Technical innovations
• image intensification
• three-phase generators
• rapid film changers
• automatic pressure injectors
• advanced catheter technology
• all helped to establish angiography
as an essential diagnostic tool by
the 1960s
Other Technologies
which demonstrate the vasculature to a
greater or less degree
• CT
• MRI
• ultrasound (particularly Doppler)
• nuclear medicine
• are all used to image vessels and
each has its advantages and
disadvantages
Vessel imaging is a
constantly evolving area.
• Current developments
• such as CT
• magnetic resonance angiography
(MRA)
• may change this in the future.
Angiography
Digital subtraction
angiography (DSA)
•is still considered the
gold standard of vessel
imaging when other
modalities are
inconclusive
development of
interventional techniques
An important offshoot of
angiographic imaging
•
•
•
•
•
have created a therapeutic technology
Embolization
intra-arterial drug therapy
transluminal angioplasty
are among the procedures that have
radically changed and broadened the
scope of the diagnostic imaging
department
Angiographic Equipment
• Vascular studies usually require a
room or suite of rooms specifically
designed to accommodate the
sophisticated and accessory
equipment needed to perform
angiography and interventional
procedures
EQUIPMENT
• Biplane C-arm digital imaging
• Autoinjector
• --syringes, a heating device,
• a high-pressure mechanism
• a control panel
Rapid film changer (NOW DIGITAL)
•
Cut film 6 & Cassette changer /magazine
• Image Intensifying screen
• Sliding table
COST
• Angiography equipment and MRI
scanners
• are major investments
• usually costing between
• $750,000 and $1 million DOLLARS
• The procedure room should be large
enough to accommodate all of the
equipment as well as radiologic and
ancillary staff
• Special procedures sometimes require a
general anesthetic that necessitates
extra equipment and staff.
• These procedures are also more
hazardous to the patient and each room
must be equipped to deal with
emergencies that may occur
• Remote computerized equipment
should also be housed adjacent to
the special room.
• Although there must be adequate
protection for all operators and
staff, there must at all times be
clear access and view of the
patient being examined
Biplane angiography
Angiographic Equipment
Generator:
• This must be a three-phase or highfrequency 12-pulse machine and at least
1000 mA to accommodate the rapid, short,
and high exposure values required in
angiography
Angiographic Equipment
Tube Ratings
X-ray tube:
• High-speed rotating anode tubes. The object of an
angiogram is to produce the highest quality
radiographs in the shortest time possible
• a 0.3 mm small focal spot will produce the best
detail
• tube rating can be exceeded because of the rapid
succession of exposures needed
• usual to have a 0.6-mm focal spot tube
Angiographic Equipment
Single or biplane image intensification
• A C-arm or U-arm device is preferable
• the equipment can be rotated rather than the
patient when visualization of the catheter is
critical
• simultaneous biplane
visualization exposures
are needed to reduce the
number of injections
of contrast required
Film changers –
NOW OBSOLETE
• the ability to move film in rapid succession,
• allowing for a number of exposures to be
registered each on its own film
• There are a number of makes, the most
common at present being the Puck system
(Siemens) which uses cut film. PUCK-U
• Programmable - allowing the operator to vary
the speed and the number of films passing
through the changer
• Speeds vary from 3 to 12 films per second,
• These changers can also be single or
biplane, allowing for simultaneous exposures.
MedCon: G. Puck film changer
Film Changer Features (5)
Supply magazine. This is a light-tight box
that can be filled with film in the darkroom
and then attached to the film changer.
Transport mechanism. This consists of a
series of compression roller devices that
moves the film from the supply magazine to
a pair of intensifying screens and then to the
receiving cassette.
Film Changer Features (5)
Compression table. This contains a pair of screens.
As soon as the film is positioned between them,
they compress the film and the exposure is
automatically triggered. As soon as the exposure
is complete, the compression is released and the
film advanced to the receiving cassette.
Receiving cassette. This is the magazine that holds
the exposed film. When the examination is
complete, the cassette is removed from the
changer and taken to the darkroom to be
unloaded. It is returned empty to the changer.
Film Changer Features (5)
Program selector: This allows the operator to
set speeds and film quantity to suit the
examination being undertaken.
Programs can be designed to fit standard
requirements of various procedures.
Film Changer Features (5)
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•
•
•
•
Supply magazine
Transport mechanism
Compression table
Receiving cassette
Program selector
Equipment
•
•
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Cine radiography.
Fluoroscopy unit with TV monitor:
Single or biplane fluoroscopy units are available.
Video equipment – DIGITAL RECORDING
Other image recording devices: Images can be
acquired and stored in a digital format
(postprocessing). This is the fundamental principle
of DSA.
CINE – 35 MM roll film
Angiographic table
• are horizontal only
• but with moving or floating capabilities
• It is important that during a procedure, a
patient can be moved without actually being
repositioned, particularly with the catheter
in situ.
Pressure Injectors
• In most angiographic studies
• contrast must be administered
consistent speed
• either faster
• as in abdominal angiography
• or slower as in lymphangiography
SAFETY MEASURES: P 638
LIGHT / ALARM /
at
a
Pressure Injectors
• Warms contrast – improve viscosity
• Piston – motor driven plunger
• SAFETY MEASURES (p.638)
• Flashing light – audible tone – message
• OPERATIONAL ERROR – OMISSION
• PREVENTS EXESSIVE PRESSURE
FLOW RATE CONTROLLED
Pressure injectors
are motor driven and have the following major components
• Control panel where parameters for
injections are set.
• Motor
drive
mechanism
is
the
electromechanical device that drives the
plunger into the syringe at a specific
pressure.
Pressure injectors
• Syringes are always removable for
sterilization purposes or are disposable.
• Heating system maintains the contrast at
near body temperature to reduce shock and
lower the viscosity of certain contrast
media.
Digital Fluoroscopy
• Fluoroscopy is a common
technique used by clinical
physicians to obtain real
time images of moving
body parts and internal
structures of a patient
compared to static
radiographic examinations.
Digital Fluoroscopy
• A digital fluoroscopy system is commonly
designed as a conventional one in which the
analog video signal is converted to and stored
as digital data by an analog to digital converter
(ADC)
Digital Subtraction Angiography
(DSA)
• Performed for diagnostic and therapeutic
purposes of vessel visualization in the body.
Digital Subtraction Angiography
• DSA uses an II/TV
system combined
high speed
processor in
angiographic
with a
image
a digital
system.
DSA Equipment
• Digital subtraction angiography requires
more complex equipment than digital
radiography,
• specifically because it has to manipulate
a number of pulsed images and at the
same time create a subtracted image
using the first pre contrast image as a
mask
Digital Fluoroscopy and
Digital Subtraction Angiography (DSA)
• DIGITAL
FLUOROSCOPY
• Introduction
• Design and Equipments
• DIGITAL IMAGING
CONCEPTS
• Binary Numbers
• Pixels
• Gray levels
• DIGITAL IMAGE DATA
PROCESSNG IN
DIGITAL
FLUOROSCOPY
• Last Image Hold
• Gray-scale processing
• Temporal Frame Averaging
• Edge Enhancement
Digital Fluoroscopy
• ALTERNATE DIGITIZATION
• Digital video camera (Charge-couple
device)
• Direct capture of x-ray (flat–panel detector)
Image digitizer
• This turns the analog TV image into a
digital image consisting of pixels
• the number of which depends on the
lines per inch of the TV image
• The usual pixel numbers in an image
are 512 x 512 or 1024 x 1024 (high
resolution)
Digital Subtraction Angiography (DSA)
• DSA refers to a technique which compares two
images of a region of the body before and after a
contrast medium has been injected into the body for
the purpose of studying blood vessels.
DSA
• In traditional angiography, we acquire
images of blood vessels on films by
exposing the area of interest with timecontrolled x-ray energy while injecting
contrast medium into the blood vessels.
• The images thus obtained would also record
other structure besides blood vessels as the
x-ray beam passes through the body. In
order to remove these distracting structures
to see the vessels better, we need to acquire
a mask images for subtraction.
DSA continued
• The mask image is simply an image of the same
area without contrast administration. So, using
manual darkroom technique, clear pictures of
blood vessels are obtained by taking away the
overlying background.
• In DSA, the images are acquired in digital format
through the computer. With the help of the
computer, all images would be recorded into the
computer and subtracted automatically. As a
result, we can have a near-instantaneous film show
of the blood vessels alone after x-ray.
Digital Imaging Concepts
• FUNDAMENTALS
• Binary numbers
• Pixels
• Gray levels
Pixels and Matrix
• Pixel: The smallest element of a digital image
• Matrix: A two dimensional series of square
boxes composed of pixels
• Digital fluoroscopy uses 512x512–1024x1024 pixels
Comparison of a clinical image at different
matrix sizes
16x16
32x32
64x64
128x128
256x256
512x512
Gray Levels
in
Digital Fluoroscopy
• ADC samples the analog video signal exiting
the video camera tube and converts the value
of the video signal to a binary number for
processing and storage
Comparison of a clinical image at different bit
depths - gray levels
• 256 gray levels (8bits)
16 gray levels (4bits)
• 8 gray levels (3bits)
4 gray levels (2bits)
Last Image Hold
The last frame acquired before stopping x-ray
acquisition is continuously displayed
LIH - stays on screen
Use of Road Mapping with Clinical
Images
• .
Digital Subtraction Angiography (DSA)
Pre-contrast image
Pos-contrast image
Subtracted image
Venous system
DIGITAL ADVANTAGE -Edge Enhancement
Original Image
Subtracted Image
Blurred Image
Edge-Enhanced image
(Edge-enhanced image = [original image - blurred version] + original image.)
Mask Pixel Shift
Subtracted image with the subtraction
image is shifted several pixels
mask
Image Summation
• Image summation is used to combine two or more
frames of a DSA imaging sequence to form a
complete image of vessel anatomy.