Xray Mammography DSA

1. Mammography
• Mammographic X ray Tube
•Device for compressing breast
•Focal spot size
•High Voltage Generator
•Anti scatter grid
•Mammographic Image receptor
•Automated Exposure Control System
•Specialized soft tissue radiography technique , dedicated to breast imaging
•Basically 2 types of structures dealt with – Poor contrast
•Water density-muscle,gland,fibre,blood vessel
•Fat
• Lesion (tumor) can be seperated radiographically from surrounding fat-often
present in sufficient amount – acts as Natural contrast
•EXPOSE FACTORS :-
•LOW KV:- Lower KV- greater radiographic contrast
•MINIMUM FILTERATION OF BEAM
•SMALL FOCAL SPOT Smallest available focus is used, never more than 1mm; to
prevent distortion of image & permit good magnification
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Uses Soft radiation- by operating tube at low kV- High mA
Increases contrast
Increases dose also !
Filament of mammo-much close to anode
Mo anode- Mo filter
Small focal spot size

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8. Focal spot
area of anode surface which receives the beam of electrons
from cathode
Basic concept
Size and shape of the focal spot is determined by the size and shape of
the electron beam when it strikes the anode.
Size and shape of the electron beam is determined by:
dimensions of the filament tungsten coil
construction of the focusing cup
position of the filament in the focusing cup
The focal spot sizes commonly employed are:
0.3mm and 0.6mm, usually for mammography
1.0mm and 1.2mm, usually for general radiography
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10. Using same metal (Mo)-for both target & filter : SPECTRAL WINDOW PRINCIPLE
Filter readily transmits Characteristic radiation produced initially by same element –
while absorbing much of general radiation
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14. Good & uniform Compression of breast to be imaged :-
•Immobilezes breast
•Decrease geometric unsharpness
•Increases contrast ( seperates breast structures )
•Decrease scatter radiation ( brings tissue closer to Image Receptor)
•Holds breast tissue away from chest wall ( removes overlap)
•For homogenicity of image density
VIEWS TAKEN:-
Craniocaudal (CC)
IR raised for 90º chest wall angle.
Compression applied
Correct placement of the photocell in film screen mammography is under the
most glandular tissue
Typically the anterior third of the breast
Pectoral muscle should be seen
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16. CR angled 45º-50º and enters medially.
IR raised to the height of the axilla
Compression applied
Film Screen mammography-position of photocell is under the most
glandular tissue typically the anterior third of the breast
Pectoral muscle and inframammary fold should be seen.
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18. X-ray tube
• Cathode accelerates electrons
and leads them to
anode(electron beam).
• Only a small portion of the
electron beam is converted to
x rays.
• Photons are discharged in all
directions.
• By adjusting current and
voltage, we can direct the
beam on a visible substance.

19. Rotating Anode
• The anode of rotating anode
tube consist of a large disc of
tungsten, or an alloy of
tungsten, which theoretically
rotates at a speed of about
3600 rpm.
• The purpose of rotating anode
is to spread the heat produced
during an exposure over a
large area of anode.

21. PARTS OF X-RAY MACHINE
• X-Ray Generator: High voltage generator: modifies incoming
voltage and current to provide an x-ray tube with the power
needed to produce an x-ray beam of the desired peak-kilo-
voltage (k V p) and current (mA) and duration (Time).
• Control panel: Permits the selection of technique factors and
initiation of radiographic exposures mA, kV, Time
• Transformer: Transformers modify the voltage of incoming
alternating-current (AC) electrical signals to increase or
decrease the voltage in a circuit.

22. …CONT
• Step-up transformer: Supplies the high voltage
to the x-ray tube (voltage increases and current
decreases)
• Step-down transformer: Supplies power to
heat the filament of the x-ray tube (voltage
decreases and current increases)
• Autotransformer: Supplies the voltage for the
two circuits and provide a location for the K v p
meter (indicates the voltage applied across the
x-ray tube)
• Rectifiers: Convert AC into the direct current
(DC) required by the x-ray tube. A rectifier
restricts current flow in an x-ray tube to one
direction (from cathode to anode), thereby
preventing damage to the x-ray tube filament.
Two types: Half wave and Full wave.

23. …CONT
• X-RAY TUBE: It is an expensive wearing element in
medical radiological equipment. It consists of
 Anode,
 Expansion bellows (provide space for oil to expand),
 Cathode (and heating-coil),
 Tube envelope (evacuated) ,
 Tube housing,
 Cooling dielectric oil,
 Rotor,

24. …CONT
• High Tension Cable: Special highly insulated
cables Considered are the cable capacitance (130-230
pF/m) because it affects the average value of the
voltage and current across the x-ray tube (increases
the power delivered to the tube.
• Collimators and Grids: They are used to increase
the image contrast and to reduce the dose to the
patient by mean limiting the x-ray beam to the area of
interest.
• Collimator: It is placed between the x-ray tube and
the patient and Usually provided with an optical
device, by which the x-ray filed can be exactly
simulated by a light filed.
• Grid: It is inserted between the patient and the film
cassette in order to reduce the loss of contrast due to
scattered radiation.

25. …CONT
• X-ray film: X-ray film is a sensitive material (sheet)
for the x-ray. A film that has been exposed to x-rays
shows an image of the x-ray intensity.

26. High Voltage Transformer
• The high voltage transformer is a step-up transformer.
• There will be more winding on the secondary side
compared to the primary side.
• The ratio of windings is referred to as the turns ratio.
• The only difference between the primary and
secondary waveforms is the amplitude.
• The turn ratio for most x-ray high voltage transformers
is between 500 and 1000.
• The primary voltage is measured in volts, and
secondary in kilovolts.

27. Autotransformer:
• The power supplied to x-ray
machine is delivered to a
special transformer called
an Autotransformer.
• It works on the principle of
electromagnetic Self
induction
• Iron core wrapped by
simple coil winding.
• Attached to input power

28. • It has only one winding and one core.
• The single winding has number of
connections, or electric taps.
• The purpose to use the Autotransformer is to
overcome induction losses.
• Its value ranges from 0 to 400V.

29. Protecting Housing

30. • X-ray tube is always mounted inside a lead-
lined protective housing that is designed to:
– Prevent excessive radiation exposure.
– Prevent electric shock to the patient and operator
(technologist)
• Incorporates specially designed high-voltage
receptacles.
• Provides mechanical support for the x-ray
tube and protects it from damage.
• Some tube housings contain oil in which the
tube is bathed.
• Some tube housings contain a cooling fan to
air-cool the tube.

31. • When properly designed, they reduce the
level of leakage radiation to less than 100
mR/hr at 1 meter when operated at
maximum conditions.

32. Grid
• By virtue of function and
material, collimator and
grid are same but they
have different location.
• It is made up of lead.
• It is located just after
patient.
• It is used to destroy
scattered radiation from
the body.

33. Bucky
• A Bucky is a component of x-ray units that
holds the x-ray film cassette and moves
the grid during x-ray exposure. The motion
keeps the lead strips from being seen on the x-
ray picture.
The name refers to Dr. Gustave Bucky who
invented the use of filter grids in 1913.

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35. kVp Adjustment (circuit Diagram)

36. • X-ray console have adjustments labeled major
Major kVp and minor kVp.
• By the combinations of these two, we can get
the required kVp.
• The low voltage becomes input to the high
voltage step up transformer.
• The kVp meter is placed across the output
terminal of autotransformer.

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38. mA control

39. • The tube current, the number of electrons
crossing from the cathode to anode per
second is measured in milli Amperes (mA).
• The quantity of electrons is determined by
filament temperature.
• The filament normally operates at currents
between 3 and 5 A.
• The Tube Current is controlled through a
separate circuit called the filament circuit.
• The transformer used for filament is step
down .

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46. collimator

47. • The Collimator is attached to the x-ray tube
below the glass window where the useful
beam is emitted.
• Lead shutters are used to restrict the beam.
• Its purpose is to minimize field of view, to
avoid un necessary exposure by using lead
plates.

48. DIGITAL SUBSTRACTION ANGIOGRAPHY
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Blood vessels are not
normally seen in an x-
ray image because of
low contrast.
Dense fluid with high
atomic numbers
increase the contrast.
e.g. Iodine.
Iodine absorbs photons
more than blood and
tissue.
The first contrast media
used for intravascular
injection were called
high-osmolar contrast
media (HOCM).
Digital subtraction angiography (DSA) is a type of fluoroscopy technique used
in interventional radiology to clearly visualize blood vessels in a bony or dense
soft tissue environment.

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 During angiography, patients may be sedated to reduce
anxiety.
 Their heart rate and rhythm, breathing, and oxygen
saturation are monitored throughout the procedure.
 Patient clean draped .
 A local anesthetic is usually used in the area where the
catheter is to be inserted, most commonly the femoral
artery.
 First, a small incision given, medicut is inserted into the
artery. fluoroscopy is used to guide the needle to the proper
position .
 The needle is then removed after placing guide wire in the
artery and vascular sheath is inserted over the guide wire .
The catheter is then inserted along the guide wire through
the sheath.
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When the catheter is in the correct position, the
wire is pulled out and dye is injected through the
catheter.
Images are acquired during contrast injection.
Injections can be made directly into the artery of
interest (selective arteriography)
Complications from an arteriogram are very rare,
but there is some risk. Most problems that occur
can be detected at the time of the procedure or
immediately after the procedure. The artery may be
injured at the puncture site or along the artery
where the catheter is passed.
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Modern DSA systems are based on digital fluoroscopy
systems, which are equipped with special software and
display facilities.
(DSA) was developed to improve vessel contrast. This is
a technique that uses a computer to subtract two images,
obtained before and after contrast media is injected into
the vessels of interest. The anatomical structures that are
the same in the two images can be removed and the
resulting image shows the vessels only.
The principles of subtraction are based on the following:
The scout film shows the structural details
Angiogram film shows exactly the same anatomic details, if the patient does
not move, plus the opacified blood vessels.
If all the information in the scout film could be subtracted from the angiogram
film, only the opacified vessel pattern would remain visible.

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The image before the contrast agent is administered is
called the mask image.
Once the contrast is administered, a sequence of images
are taken by a television camera in analog form, which
is then digitised by computer.
The DSA processor has two separate image memories,
one for the mask and the other for the images with
contrast medium.
These two image memories are subtracted from one another
arithmetically, and the result goes to an image processing
and display unit.

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Digital subtraction techniques
DSA has many techniques
 Mask subtraction
 Time interval differencing
 Dual energy subtraction
 Hybrid
 Temporal filtering
 K edge substraction

56. Types of Substraction :-
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•MASK-MODE SUBTRACTION most widely used process of DSA in which temporal
subtraction is done . It involves initial acquisition of a frame of region of interest which is
used to stabilize the exposure factors.
•Then a second image is taken and stored as mask image. This mask image is subtracted from
subsequently acquired images on pixel–by–pixel basis and show only contrast filled
structures.
•If any movement occurs after acquisition of mask image, misregistration occurs in the
subtracted images. This can be overcome to some extent by pixel shifting.
•TIME INTERVAL DIFFERENCE SUBTRACTION is another mode of temporal subtraction
where a consecutive previous frame is subtracted from current frame (e.g, frame 1 from
frame 2, frame 2 from frame 3 and so on). very useful in cardiac imaging (rapid motion).
•images obtained can then be stacked to provide a composite
image without motion.
•DUAL ENERGY SUBSTRACTION
•region of interest is exposed to higher kV (120 to 130 kV) and lower kV (70 kV) at
very short interval (about 50 ms).

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Types of Substraction :-
•DUAL ENERGY SUBSTRACTION higher kV image is subtracted from the lower
Kv image to produce an iodine and bone image (the soft tissue and gas
shadows are eliminated). This technique has the advantage of elimination of
motion artifacts. The limitations of this mode of subtraction include increased
radiation dose, reduced opacity of contrast opacified structures, reduced
SNR and increased complexity of the equipment.
• HYBRID SUBSTRACTION
combination of dual energy and temporal subtraction.
 High KVp & low KVp image pair is collected.
 No pt. movement – soft tissues cancel properly. but bone edges cause severe
artifact.
 Consider the subtracted images to consist of only 2 atomic no. materials (iodine &
bone).
 The hybrid subtraction produces 2 sets of subtracted images.
 The same bone & iodine structures are present on both sets.
 D.E.S can now be used to eliminate bone leaving only iodine.
 The final image – more noise.

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•K edge subtraction
 Iodine attenuates diagnostic x-rays almost entirely
by P.E.E.
 One method for achieving high iodine contrast is
removal of all x-rays from the beam except those
that lie below the k-shell B.E of ‘I’.
 An x-ray filter made of rare earth named cerium can
do this well, since B.E = 40 KeV.
 Thick filter will remove most of the x-rays above 40
KeV.
 The image to be subtracted should contain few
x-rays.

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•Temporal filtering
 Temporal filters are used.
 This filter generates one final image by adding &
subtracting some of the original images together, &
then shifting & repeating to form the next image.

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Adjust contrast & brightness.
Remasking – correcting misregistered images.
Pixel shifting.
Edge enhancement – edges of the vessels can be enhanced so
that small details can be made more obvious.
Image zoom.
land marking – a small amount of original image is added
into the subtracted image.
Noise smoothing – operates by reducing the statistical
fluctuations in each pixel by averaging the pixel with it's
closest neighbors. The visual prominence of noise has
been suppressed by averaging, but resolution is
decreased.
IMAGE PROCESSING

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Post-processing in DSA
Mask pixel shift is a software modification feature used when smaller patient
motion occurs after the mask image is acquired. By shifting the pixels of the mask image,
reregistering of the mask with post contrast image is possible thus obviating motion
artifacts This technique may be manual or automatic.
Remask is a similar feature where another mask image is selected, which is temporally
closer to the contrast image. This is useful when patient motion occurs prior to contrast
image, but after initiation of the acquisition.

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Image summation is a property in which two or more frames of a DSA acquisition
are summed into a single image This is beneficial when rapid acquisition opacifies
part of a vessel in each frame and summation adds up the frames to produce a
single image showing the entire vessel.
Stacking is a similar technique used in carbon dioxide angiography where the
fragmented boluses of the gas are added to produce a complete picture of the
opacified structure.

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Land marking is a feature in which lesser intensity (10- 20%, but is manually
adjustable) of original image is added to the subtracted image. This provides
anatomical landmarks in subtracted images, useful in subsequent intervention.
(A) Subtracted aortogram with bronchial and intercostal arteries without bony
landmarks.
(B) Conventional image (B) although shows bones well, the arteries are not well
seen.
Land marking (C) shows both the arteries and bones

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When a digital subtraction
technique is used, patient motion
that occurs between acquisition of
the precontrast images and
acquisition of the postcontrast
images will result in artifacts due to
misregistration of the two images.
If these arti-facts are observed, it is
possible to reregister the pre- and
postcontrast images by shifting the
subtraction mask (precontrast
image) with respect to the
postcontrast image and
resubtracting the two images

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Road mapping is useful for the
placement of catheters and wires in
complex and small vasculature.
DSA sequence is performed, and
the frame with maximum vessel
opacification is identified;
this frame becomes the road map
mask. The road map mask is
subtracted from subsequent live
fluoroscopic images to produce
real-time subtracted fluoroscopic
images overlaid on a static image
of the vasculature
Road Mapping

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• In the scanning section of tube, externally mounted coil
(emitting focusing coil and electrostatic deflecting coil) produce
an axial electromagnetic field by means of which-
• The electrons are focused on the target of tube and
• The beam is moved over the target area in an orderly
scanning scan
• Two types scanning system
• Sequential scanning pattern and
• Interlaced scanning pattern
SCANNING SECTION/ SYSTEMS

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SEQUENTIAL SCANNING
PATTERN
• Also called progressive scanning
Disadvantages
• Technical
• Requires a wide frequency band during transmission

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Interlaced scanning
• Instead of scanning all 625 line
consequently, only the even no. of lines
are scanned the first half of the frame
and only the odd no. lines are scanned
during second half.
• In this pattern the transmission is easier
and cheaper because the actual picture
frequency is lower

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TELEVISION IMAGE QUALITY
•One of the most critical components in the imaging chain
for our example digital radiographic system is
the video camera.
•The basic function of the video camera is to produce an
analog electronic signal that is proportional to the
amount of light received by the target of the camera.
•Characteristics relating specifically to TV system
•Resolution
•Contrast
•Brightness
•Image lag
•Distortion

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Working principle of T.V monitor
Control Grid
No. of e-ns & the brightness of
individual dots
Produce bright area in the TV
Picture
Dark Area
Strikes the fluorescent Screen
Emits large no. of light
photons
VISIBLE TV IMAGE
Receive Video signal from ccu & regulate
Grid cuts off the e-ns flow almost completely
E-ns is Accelerated

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VIDICON CAMERA TUBE
•Diameter 1 inch
•Length 6 inch
•Main parts -
•Target section
•Electron gun
•Electromagnetic focusing coil
•Two pair of electrostatic deflecting
coil
•A scanning section

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Image Intensifier
The main purpose of image intensifier is to
amplify the brightness of the fluoroscopic
image, thus obviating the need of dark
adaptation by the radiologist.
Two important functions of II are fluorescence
(conversion of X-ray photons
into visible light) and light signal amplification.
The basic elements that make an image
intensifier are contained in a
vacuum case and include input phosphor,
photocathode, focussing lenses, anode and
output phosphor
main function of input phosphor is to
convert X-ray photons into light photons.

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Artifacts
• Lag
• Vignetting,
• Veiling glare
• Pincushion distortion
• S distortion.
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Lag
Lag is the persistence of luminescence after x-ray
stimulation has been terminated.
Lag degrades the temporal resolution of the dynamic image.
Older image intensifier tubes had phosphors with lag times
on the order of 30–40 msec. Current image intensifier tubes
have lag times of approximately 1 msec.
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Vignetting
A fall-off in brightness at the periphery of an image is called
vignetting. Vignetting is caused by the unequal collection of
light at the center of the image intensifier compared with the
light at its periphery. As a result, the center of an image
intensifier has better resolution, increased brightness, and less
distortion.

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Veiling Glare
Scattering of light and the defocusing of photoelectrons
within the image intensifier are called veiling glare. Veiling
glare degrades object contrast at the output phosphor of the
image intensifier. As mentioned, the contrast ratio is a good
measure of determining the veiling glare of an image
intensifier. X-ray, electron, and light scatter all contribute to
veiling glare.
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Pincushion Distortion
•Pincushion distortion is a geometric, nonlinear magnification
across the image.
•The magnification difference at the peripheryof the image results from
the projection of the x-ray beam onto a curved input surface.
•Due to curvature of Input Phospher of II
•The distortion is easily visualized by imaging a rectangular grid with
the fluoroscope.

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S DISTORTION
• Electrons within the image intensifier move in paths along
designated lines of flux.
• Due to Geo-magnetic field on moving e- within Image
Intensifier
• External electromagnetic sources affect electron paths at the
perimeter of the image intensifier more so than those nearer
the center.
• This characteristic causes the image in a fluoroscopic system
to distort with an S shape .
• Manufacturers include a highly conductive mu-metal shield
that lines the canister in which the vacuum bottle is
positioned to reduce the effect of S distortion.
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Generator characteristics
X-ray generators High powered x-ray generators to provide almost constant
potential power supply to the tube.
Two Velara CVFD microprocessor-controlled 100 kW high-frequency converter
generators.
Minimum exposure time of 1 ms.
Voltage range: 40 kV to 125 kV.
Max current:
- MRC-GS 04-07: 802 mA at 80 kV.
- MRC-GS 05-08: 1062.5 mA at 80 kV.
Automatic kV and mA control for optimal image quality prior to run to reduce
dose.
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Generator characteristics cont.
Max continuous power for fluoroscopy: 2.4 kW for 0.5 hour
and 2 kW for 8 hours.
Nominal power (highest electrical power): 100 kW (1000 mA
at 100 kV)
Reference loading conditions: 110 kV, 18 mA continuous.
Pulsed X-ray of 3.75, 7.5, 15 and 30 frames/sec. in
monoplane and biplane mode for pulsed fluoroscopy.
Pulsed X-ray of 0.5 to 6 frames/sec. for digital subtracted
acquisition in monoplane and biplane mode.
Pulsed X-ray up to 6 frames/sec. for digital acquisition in
monoplane and biplane mode. 15 and 30 frames/sec.
Noise < 55 dB(A).
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X-Ray Tubes
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The high performance metal ceramic tubes .
Most relevant feature is support of the rotor anode in
a spiral groove bearing
The spiral groove bearing glides on a thin film of
liquid metal to maximize heat dissipation allowing
virtually unlimited X-ray sessions without forced cool
down delays.
• The MRC tube runs silently offering a more
comfortable patient environment.
• Another secret of the MRC tube is the enormous
heat storage capacity of its 200 mm diameter anode,
eliminating waiting times.
• And, the MRC X-ray tube can image the heaviest
patients even at steep angles, while maintaining image
quality.

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Tube Specifications

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Tube Specifications …

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Detectors
 More recently, however, the
image intensifier/CCD
combination has been replaced
by an advanced flat detector
imaging device.
 The flat detector converts the
light generated by the absorbed
X-ray energy in the scintillation
layer directly into a digital
electrical signal.
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Flat detector frontal
 Size of housing 42x52 cm
 Maximum field view 30x38cm
 Image matrix 2480x1920
pixel at 14 bit height
 Detector zoom fields
30x30cm,22x22cm,
16x16cm,13.5x13.5cm,
11x11cm formats
Pixel size 154x154 μm
Detective Quantum Efficiency (DQE):
>73% at low spatial frequencies
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Flat detector lateral
• Size of housing 28x28
cm
• Maximum field view
18x18cm
• Image matrix
1024x1024 pixel at 14 bit height
• Detector zoom fields
14.5x14.5cm, 11x11cm formats
Pixel size 184x184 μm
Detective Quantum Efficiency
(DQE): 75%
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Patient support
AngioDIAGNOST 5
Length: 303 cm (119.3 inch).
Metal-free overhang: 125 cm (49.2 inch).
Width: 50 cm (19.7 inch).
Longitudinal float: 100 cm (39.4 inch).
Transverse float: 36 cm (14.2 inch).
Height adjustment (without pivot option): 76
to 104 cm (29.9 to 40.9
inch).
Maximum levelling speed (height
adjustment):
- 2 cm/s (0.8 inch/s).
Table tilt:
L-arc position Angulation (degrees) Rotation
(degrees)
Head-end of table 45 Caudal to 45 cranial 27
RAO to 115 RAO
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Examination light
Light intensity: 30,000 Lux.
Colour temperature: 4300° K.
Focusable light field size: 14 - 25 cm (5.5 - 9.8 inch).
Working distance: 70 -140 cm (27.6 - 55.1 inch).
Light intensity at 30,000 Lux: 114 W/m2.
Lamp type: halogen 22.8 / 24 V 50 W.
Mains power: 220/240 V.
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