2. For nearly 100 years now, the photographic film has been
used to record images
For over 60 years, intensifying screens have been used with
x-ray films to obtain high quality images with lower radiation
doses
Very recently it has become possible to record x-ray images
without the use of conventional film-screen systems (CR and
DR systems)
But even now, radiography using film-screen technology
accounts for about 65 % of all diagnostic examinations
3. Define the key terms used in digital imaging
List the equipment needed to perform digital imaging
Explain the computed radiography (CR) digital system
Explain the digital radiography (DR) system
Explain PACS and recent advances in digital
radiography
4. Any Imaging Technique has following steps –
1. Image Acquisition
2. Image Processing
3. Image Display
4. Image Storage
5. Radiography
Analog
Digital
(Conventional)
Scanner Computed Direct Digital
(X-ray Radiography Radiography
digitizer) (CR) (DR or DDR)
6. A conventional system uses an intensifying screen
to create a latent image on x-ray film.
The film is then processed, creating a manifest
image that can be interpreted by a physician.
It is later stored in the file room (physical storage
for archival)
7. Method is film-based.
Method uses intensifying screens.
Film is placed between two screens.
Screens emit light when x-rays strike them.
Film is processed chemically.
Processed film is viewed on view-box (lightbox).
9. 10% of films are not available when we want them!
15% of films are “hard” to locate or find!
25% of films are “misplaced” or not retrievable
(misfiled).
10% of films are lost (referrals, residents, etc.)
Recent study – physicians spend two weeks/year (100
hours/year) trying to locate or find the films they
need.
Cost in physician time is estimated from $60 to
$80 per study.
10. Radiography
Analog Digital
Scanner Computed Direct Digital
(X-ray Radiography Radiography
digitizer) (CR) (DR or DDR)
11. Definition –
Digital Imaging is any modality / method of imaging
that creates an image that can be viewed or stored on a
computer.
12. Concept began in the 1950s.
Early PACS systems were developed by the military to send
images between Veterans Administration hospitals in the
1980s.
Early process involved scanning radiographs into the
computer and sending them from computer to computer.
Images were then stored in PACS.
Computed and digital radiography followed.
14. Only recently, it has become technically possible and
economically feasible to challenge film technique for
projection radiography
Made possible by certain pre-requisite technological
advances such as -
high luminance and high resolution display monitors
high performance computers / workstations
15. Radiography
Analog Digital
Scanner Computed Direct Digital
(X-ray Radiography Radiography
digitizer) (CR) (DR or DDR)
16. A scanner is used to convert
existing analog images into a
digital format
Not cost-efficient
Hence, seldom used (old
available films need to be
converted into digital format)
17.
18.
19. Definition -
Computed Radiography (CR) is a process of capturing
radiographic data from a Conventional X-ray machine
and processing the data digitally to produce crisp and
high quality radiographic images
1. Image Acquisition
2. Image Processing
3. Image Display
4. Image Storage
22. Light weigth aluminium
Plastic
Steel frame
The front panel made up of low attenuation carbon
fiber
23. Approximately 1 mm thick
Protective layer
Phosphor layer
Anti-halo and reflecting layer
Base
Backing layer
24. Fluorinated Polymer Material – Protects the Phosphor
layer
Protective layer
Phosphor layer
Anti-halo and reflecting layer
Base
Backing layer
25. Europium-activated Barium-fluorohalide (BaFX:
Eu+2)
Protective layer
Phosphor layer
Anti-halo and reflecting layer
Base
Backing layer
The phosphor crystals are usually cast into resin
material to give them the form of plates
26. To reduce scatter
Protective layer
Phosphor layer
Anti-halo and reflecting layer
Base
Backing layer
27. PET – Polyethylene Teraphtalate
Protective layer
Phosphor layer
Anti-halo and reflecting layer
Base
Backing layer
28. Protects the base from damage
Protective layer
Phosphor layer
Anti-halo and reflecting layer
Base
Backing layer
29. The Imaging Plate looks like the intensifying screens
found in Conventional film-screen cassettes
They are made of photostimulable phosphors
Instead of emitting light immediately when exposed to
X-rays, the photostimulable phosphor has the special
property of storing the X-ray energy in a latent form
and releasing the same when stimulated by a laser
energy in the CR Reader / Digitizer – photo
Phosphorescence (c/w - fluorescence)
30. When phosphors are stimulated with X-ray photon
energy, electron hole pairs are produced
In effect, Europium is excited to a higher energy level
(excited state) leaving behind a hole / vacancy
32. Energy absorbed by the imaging plate must be
transformed into electrical charges, which are then
recorded and digitized.
Read out Process
33. The readout process should start immediately after
exposure because the amount of stored energy
decreases over time (latent image completely
disappears by 24 hrs – spontaneous phosphorescence)
Stimulation with a scanning laser beam releases
electrons
Fallingback electrons emit luminescent light
(phosphorescence)
34. 633 nm
390 nm
Typical wavelength of the stimulating laser is 633 nm
(usually helium-neon laser)
Typical wavelength of the emitted light is 390 nm(BLUE)
35. The emitted light intensity is proportional to the
original incident X-ray intensity
The emitted light is captured with an optical array and
a photomultiplier tube, the signals amplified and
digitized (Analog to Digital converters - ADC)
The residual image is erased from the plate by an
intense light source, which returns all electrons to their
original state. This makes the plate ready to be reused
for new exposures
36. How many times can we use a Storage
Phosphor Plate?
• The life of a phosphor plate depends on how
carefully it is handled. Physical damage to the
plate will limit its useful life
• If properly cared for, a plate will produce
thousands of images
• Imaging Plates are known to last more than
50000 Exposure Cycles !!!!!
39. Cassette with Imaging Plate
MA
TRIXLR 3300
Rx Exposure
Printing
Network
Processing server
Identification Digitizer
40. Radiography
Analog Digital
Scanner Computed Direct Digital
(X-ray Radiography Radiography
digitizer) (CR) (DR or DDR)
41.
42. INTRODUCTION
In CR, image acquisition is a two-stage process wherein
image capture and image read out are done separately.
Direct digital radiography (DR) systems, on the other
hand, use detectors that have a combined image capture
and image read out capability.
Cassette-less system
46. There are different types of DR Systems available
depending on the type of detectors used in them
(a) Flat panel detector (FPD) based systems
(b) Charge coupled device (CCD) array based system
47.
48. Requires a photoconductor
Converts x-ray photons into electrical X-ray
charges by setting electrons free.
Directly
Typical photoconductor materials
include amorphous selenium, lead
iodide, lead oxide, thallium Electrical
bromide, and gadolinium compounds. signals
The most commonly used element is
selenium.
49. Selenium-based direct conversion DR systems are
equipped with either a selenium drum or a flat-panel
detector (FPD).
50. A rotating selenium-dotted drum, which has a positive
electrical surface charge, is exposed to x-rays.
During exposure, a charge pattern proportional to that
of the incident x-rays is generated on the drum surface
and is recorded during rotation by an analog to- digital
converter.
51. Amorphous selenium–based direct conversion DR systems.
1. A rotating selenium-dotted drum with a positive electrical surface charge is
exposed to x-rays.
2. Alteration of the charge pattern of the drum surface is proportional to the
incident x-rays.
3. The charge pattern is then converted into a digital image by an analog-to-
digital (A/D) converter.
52. Selenium Drum…..
Several clinical studies have confirmed that selenium
drum detectors provide good image quality that is
superior to that provided by screen-film or CR systems.
(ADVANTAGE)
However, because of their mechanical design, selenium
drum detectors are dedicated thorax stand systems with
no mobility at all. (DISADVANTAGE)
53.
54. A newer generation of direct conversion DR systems make
use of selenium-based flat-panel detectors.
These detectors make use of a layer of selenium with a
corresponding underlying array of thin-film transistors
(TFTs).
The principle of converting x-rays into electrical charges is
similar to that with the selenium drum, except that the
charge pattern is recorded by the TFT array, which
accumulates and stores the energy of the electrons.
55. A selenium-based flat-panel detector system
1. Incident x-ray energy is directly converted into electrical charges
within the fixed photoconductor layer
2. read out by a linked TFT array beneath the detective layer
56. Greater clinical usefulness, since the detectors can
be mounted on thorax stands and Bucky tables
(ADVANTAGE)
Another promising clinical application of
selenium-based flat-panel detectors is in the field
of Mammography (ADVANTAGE)
Studies indicate that the image quality provided
by selenium-based flat-panel detectors is
equivalent to that provided by other flat-panel
detectors and selenium drum detectors
(ADVANTAGE)
60. Charged Coupled Device (CCD) is used
A CCD is a light-sensitive sensor for recording images that
consists of an integrated circuit containing an array of
linked or coupled capacitors.
X-ray energy is converted into light by a scintillator such as
Thallium doped cesium iodide. The amount of light emitted
is then recorded by the CCD, and the light is converted into
electrical charges.
CCD
Lens
Slot scan
coupled
61. An array consisting of
several CCD chips forms a
detector area similar to
that of a flat-panel
detector.
Optical lenses are needed
to reduce the area of the
projected light to fit the
CCD array, which
subsequently converts the
light energy into electrical
charges
62. One drawback of the lens system is a decrease in the
number of photons reaching the CCD, resulting in a
lower signal-to-noise ratio (SNR) and relatively low
quantum efficiency.
63. • Slot-scan CCD systems make use of a special x-ray tube ( tungsten anode)
with a collimated fan-shaped beam, which is linked to a simultaneously
moving CCD detector array having a matching detector width.
• The combination of a small collimated beam and a concordant detector
reduces the impact of scattered radiation in the image, since much of this
radiation will escape without detection.
• Relatively low quantum efficiency of slot-scan CCD systems can be offset by
the resulting lower image noise.
64. The exposure time to the patient is about 20 msec, and
the readout process takes about 1.3 seconds.
Because of the need for fixed installation, slot scan CCD
systems are dedicated to chest
radiography, mammography, or dental radiography.
65. Advantages –
• Relatively cheaper
• Individual defective components can
be replaces rather than changing the
entire detector
• Upgradeable to future innovations
Limitations –
• Bulky design
• Relatively small CCD arrays (2-5 cm) than the
typical projected X-ray areas – hence require
demagnification and optical coupling
• Optical system – more signal noise
• Thermal noise in CCD can degrade mage
quality
• Repeated exposure to X-rays may damage
optical system
66.
67. Small overall design, which allows integration into
existing Bucky tables or thorax stands
Image generation with flat-panel detectors is almost a
real-time process, with a time lapse between exposure
and image display of less than 10 seconds.
Consequently, these systems are highly
productive, and more patients can be examined in the
same amount of time than with other radiographic
devices.
68. Indirect conversion DR systems are “sandwich”
constructions consisting of a scintillator layer, an
amorphous silicon photodiode circuitry layer, and a
TFT array.
When x-ray photons reach the scintillator, visible light
proportional to the incident energy is emitted and then
recorded by an array of photodiodes and converted to
electrical charges.
These charges are then read out by a TFT array similar
to that of direct conversion DR systems.
70. The scintillators (in FPD) usually consist of CsI or Gd2O2S
CsI based FPD - are highly vulnerable to mechanical load
because of their fine structure, these systems cannot be used
outside of fixed installations and therefore lack mobility.
The advantage of CsI-based scintillators is that the crystals
can be shaped into 5–10 micrometer wide needles, which can
be arranged perpendicular to the surface of the detector.
This structured array of scintillator needles reduces the
diffusion of light within the scintillator layer
As a result, thicker scintillator layers can be used, thereby
increasing the strength of the emitted light and leading to
better optical properties and higher quantum efficiency
Gd2O2S based FPD - resistant to mechanical stress as are
storage phosphors and hence are portable.
71. Key features of Direct Digital Conversion
X-rays > Electrical signals
No intermediate light production
Detector material – Amorphous Selenium
Maintains high resolution of images as photoconductor
thickness is increased
Moderate DQE (effficiency) for conventional radiography
but high DQE for mammography KV range
Very sensitive to ambient temperature variations
72. X-rays > Light > Electrical signals
Used Phosphors –
Thallium doped Cesium Iodide (CsI) or
Gadolinium Oxy-Sulphide (GdO2S)
More light scatter, so less spatial resolution
Generates poorer resolution images as phosphor thickness is
increased
High DQE (Efficiency) for Conventional range KV range
Less sensitive to ambient temperature changes
74. Viewing
For an image on a screen
to have the quality
approaching that of a film
image, a special monitor
must be used with a
resolution of 1024 x 1024
pixels
75. After exposure and readout, the raw imaging data must
be processed for display on the computer.
Greatly influences the way the image appears to the
radiologist .
AIM - to improve image quality by reducing noise,
removing technical artifacts, and optimizing contrast
for viewing.
Spatial resolution (the capacity to define the extent or
shape of features within an image sharply and clearly)
cannot be influenced by the processing software
because it is dependent on the technical variables of
the detector (eg, pixel size).
76. Contrast enhancement - makes anatomic structures more visible
and distinguishable
Contrast reduction - results in smoothing of the structures
79. 1. Initially acquired raw data without any processing
2. Contrast enhancement makes anatomic structures more
visible and distinguishable
3. Contrast reduction results in smoothing of the structures
4. Edge enhancement provides sharper delineation of the fine
structures of bones
80. Positioning Markers
Add predetermined text or free text
Zoom and roam image
Invert image
Show/hide histogram (exposure details)
Advanced measurement options (Orthopedic
Application)
Stitching for full leg/full spine
81.
82. Caution - If one feature is being improved, others
may be suppressed, so that unintended and unwanted
masking of diagnostically relevant features may occur.
Consequently, image processing must be optimized
carefully for each digital radiography system.
Image processing software is usually bundled with the
detector and cannot be replaced by other software (in
DDR).
83.
84. Pixel Size, Matrix, and Detector Size
Spatial Resolution
Modulation Transfer Function
Dynamic Range
Radiation Exposure
85. Pixel Size, Matrix, and Detector Size:
Digital images consist of picture elements, or pixels. The
two-dimensional collection of pixels in the image is called
the matrix, which is usually expressed as length (in pixels)
by width (in pixels)
Maximum achievable spatial resolution is defined by pixel
size and spacing. The smaller the pixel size (or the larger the
matrix), the higher the maximum achievable spatial
resolution.
The overall detector size determines if the detector is
suitable for all clinical applications. Larger detector areas are
needed for chest imaging than for imaging of the
extremities
86.
87. Spatial Resolution:
Definition - Spatial resolution refers to the minimum
resolvable separation between high-contrast objects.
In digital detectors, spatial resolution is defined and limited
by the minimum pixel size.
Increasing the radiation applied to the detector will not
improve the maximum spatial resolution.
On the other hand, scatter of x-ray quanta and light
photons within the detector influences spatial resolution.
Therefore, the intrinsic spatial resolution for selenium-
based direct conversion detectors is higher than that for
indirect conversion detectors.
88. The older generations of storage phosphors did not have
diagnostically sufficient intrinsic spatial resolution
For digital mammography, the demanded diagnostic
spatial resolution is substantially higher indicating the
need for specially designed dedicated detectors with
smaller pixel sizes and higher resolutions
89. Modulation Transfer Function:
Definition - capacity of the detector to transfer the
modulation of the input signal at a given spatial frequency to
its output .
At radiography, objects having different sizes and opacity are
displayed with different gray-scale values in an image.
MTF has to do with the display of contrast and object size.
More specifically, MTF is responsible for converting contrast
values of different-sized objects (object contrast) into contrast
intensity levels in the image (image contrast).
MTF is a useful measure of true or effective resolution, since it
accounts for the amount of blur and contrast over a range of
spatial frequencies.
90. Dynamic Range
Dynamic range is a measure of the signal response of a detector
that is exposed to x-rays .
In conventional screen-film combinations, the dynamic range
gradation curve is S shaped within a narrow exposure range for
optimal film blackening .
Thus, the film has a low tolerance for an exposure that is higher or
lower than required, resulting in failed exposures or insufficient
image quality.
For digital detectors, dynamic range is the range of x-ray
exposure over which a meaningful image can be obtained. Digital
detectors have a wider and linear dynamic range, which, in
clinical practice, virtually eliminates the risk of a failed
exposure.
91.
92. Detective Quantum Efficiency (DQE):
Deficiency - Efficiency of a detector in converting incident x-
ray energy into an image signal.
Calculated by comparing the signal-to-noise ratio (SNR) at
the detector output with that at the detector input as a
function of spatial frequency .
Dependent on radiation exposure, spatial frequency, MTF,
and detector material.
High DQE values indicate that less radiation is needed to
achieve identical image quality; increasing the DQE and
leaving radiation exposure constant will improve image
quality.
93. The ideal detector - DQE of 1, meaning that all the
radiation energy is absorbed and converted into image
information.
In practice, the DQE of digital detectors is limited to
about 0.45 at 0.5 cycles/mm.
94.
95. Radiation Exposure:
The higher DQE values of most digital detectors compared
with screen-film combinations suggest that, besides
providing better image quality, digital detectors have the
potential for substantially lowering patient exposure without
a loss of image quality.
The most obvious way to minimize patient exposure is to
greatly reduce the number of failed exposures and requisite
additional images.
This reduction is made possible by the wider dynamic range
of digital detectors compared with conventional screen-film
combinations.
96. Unlike storage-phosphor systems, in which the
possibility of exposure reduction is limited, DR systems
offer a significantly higher potential for general
exposure reduction because of their far superior
quantum efficiency.
Several studies have shown that a considerably lower
exposure is required for equivalent depiction of
anatomic details with flat-panel detectors than with
storage phosphor systems and screen-film
combinations.
In summary, reduction of exposure in flat-panel
detector digital radiography is possible, to some extent
regardless of the clinical situation.
100. A Picture Archiving and Communication System is an
inter and intra-institutional computation system that
manages -
data acquisition ,
transfer,
storage,
distribution
display and
interpretation of medical images,
all integrated with various digital networks .
101. Radiologists need to view, archive, and retrieve
patients' images.
they also need to retrieve and recall complex and rare
pathologic, anatomic, and radiologic knowledge and
compile, retrieve, and consult medical records and
reports.
Finally, they have to be able to communicate results to
referring physicians and colleagues.
102. Components of PACS
• Scheduling,
Digital acquisition devices • Demographics,
Network Short term-rapid access
• Patient information, and
Long term-slowcomponents
• Billing database access
Database server Duplicate-off site for disaster
• Reports
recovery
Archival system
Radiology information system / Hospital Information
System (RIS / HIS)
Soft copy display
Early remote access (for the referring clinician)
104. Once correctly installed, no information is lost and
available when needed
Comparison with previous examinations available at all
times
Simultaneous viewing in different places
Retrieval easy
Post processing manipulations
Film budget reduced
Tele-radiology
105. Technically complex ,
Dedicated maintenance program required
Training required
No fall back after installation
Failure of individual workstations or acquisition
components will affect functions and data flow in the
local PACS branch, failure of the PACS controller or
main PACS archive server can cripple the entire PACS
operation.
108. The rapid acquisition of images
can result in latent signal from
one exposure lingering into the
readout of subsequent
exposures, producing what
appears to be an incomplete
erasure of the previous image,
known as Image lag / Ghosting.
Mainly a DR artifact because of
rapid image acquisition ability
109. Flawed Gain Calibration
Detector Lag
Backscatter (in portable DR due to thin backside
shielding – to make it lighter)
110.
111. (a) Tomosynthesis:
Multiple low dose exposures are given from various angles
while the X-ray tube moves in an arc and the detector remains
stationary.
Multiple images with different focal zones are possible to be
created by addition of these low dose images after pixel shift.
It emphasizes contrast in a particular layer of a region of body.
Generated images can be viewed singly or as a cine loop.
It is considered useful in Chest, IVU studies and
mammography
112. (b) Dual-energy imaging:
By using a high and low kilo-voltage technique, two
datasets are created. Soft tissues and bones can be
separately depicted by this method.
Dual-energy techniques are most effective when both
images are acquired simultaneously. Similar results are
obtained with two exposures within a very short period
of time.
This is useful in chest radiography, particularly for the
evaluation of partially calcified nodules and pleural
plaques.
113. (C) Computer aided diagnosis (CAD)
software programs:
These are important in early detection of cancer of the
lung and breast. The suspicious areas are marked by the
software for review by the radiologist.
The efficiency of CAD software program is related to its
sensitivity and specificity profile.
The main advantage of CAD is that it permits a
radiologist to avoid overlooking diagnostically significant
findings.
114. (d) Automatic image stitching:
Useful in determining precise measurements in lengthy
anatomical regions like the spine or lower limbs.
The largest flat-panel DR plates available today are 43 × 43
cm. Using these detectors, only a limited portion of the body
part can be imaged at one given time, thus making these
detectors inadequate for studying the whole spine or the
entire lower limb.
To overcome this problem, multiple sequential exposures at
different patient positions are acquired in a still patient.
Automatic stitching is then performed to reconstruct a larger
composite image. This special software enables pixel shift
and overlap.
115. (e) Mobile DR:
This is in general a 17 × 14-inches flat panel detector
(FPD) connected by a cable to a mobile x-ray system
having a monitor.
The use of mobile DR systems is hampered by the
fragility of the FPDs and the high costs. A mobile DR
system, when compared with an FSR system, avoids
problems related to the availability, storage,
transportation and disposal of films and chemicals.
116. (f) Wireless FPDs:
Wirelessly transfers image data to the DR system
(Pixium 3543, Thales)
It has no cables and does not interfere with surrounding
machines.
Typically a 17 x 14-inch image is made available within 3
sec. This allows radiography of difficult regions of the
body like the axilla or the TM joint and enables
radiography in unusual positions as in a flexed knee, or
in a limb with limited mobility due to contractures.
117.
118. Some of the drawbacks of CR systems, namely
cassette handling,
long read out time of PSP plates,
low DQE and
poor resolution
Have been addressed by newer innovations and
technological advances.
119. (A) Automated CR systems with fast
readout:
Automated CR systems reduce the readout time less
than 10sec
In these systems there is no cassette handling, leading to
totally automatic image data acquisition
120. (B) Newer phosphors for PSP plates:
Commercially available PSP plates have unstructured
phosphor like rubidium chloride or barium fluorohalides
doped with Europium.
A needle-shaped phosphor cesium bromide, has been
newly introduced, for example, in Konica Minolta's Regius
370 Upright DR, and is considered more efficient due its
structured configuration of crystals.
It reduces light diffusion because of the needle shaped
configuration that acts as light guide. In addition the newer
phosphors are more efficient with an increased DQE.
121. (C) Mobile CR systems:
Mobile X-ray unit with an integrated CR reader.
They are easy to use and offer quick image availability
in less than 25 sec.
122.
123. Relatively cheaper (c/w DR)
Can be incorporated into existing radiography system
Cassettes and imaging plate relatively more sturdy
(c/w DR)
Relatively more time for image processing (c/w DR)
Less DQE (c/w DR)
124. Increased workflow
Integrated high power X-ray system of 30-100 KW –
very short exposure times – eliminating motion blur
Reduction in radiation dose possible as per ALARA
principle
Presets available for various anatomical studies
Automatic Exposure Control (AEC) facility
Automatic filter, focal spot size and tracking for easy
positioning
125. High initial cost
Some radiographic views are difficult to obtain as
detectors are generally not free to be placed in any
position
Fragile detectors – careful handling
126. ENTRANCE SURFACE DOSE
STANDARD RADIOGRAPHIC EXAM USING SFR,CR,DDR
G compagnona, Balani et al: BJR NOV 2006
SFR – Screen Film Radiography
CR – Computed Radiography
DDR – Direct Digital Radiography
127. NIMS FIGURES AT A GLANCE
SEPT 2009-AUG 201O - CONVENTIONAL
SEPT 2010-AUG 2011 - DIGITAL
128. Analog CR DR
(conventional)
Installation Cost + ++ ++++
Radiation reduction not possible possible Definite reduction
possible
Fragility - + +++
Spatial resolution + + ++ (high quality
monitors)
DQE + +++ ++++
Dynamic range + (‘S’ shaped +++ (Linear & +++ (Linear &
curve) wide) wide)
Post processing Not possible possible possible
PACS and teleradiology Not possible possible possible
Image display time +++++ ++ (upto 25 sec) + (< 10 sec)
129. Conventional Radiography is evidently the last of the radiology modalities to
embrace and incorporate digital technology.
The future of radiography will be digital.
CR is a simple and cost effective technology that permits use of existing
radiographic equipment. It has been suggested that for moderate workload
(upto 70-90 films per day), a CR system is adequate.
High cost of a DR system is justified only when the workload is much beyond
this level.
Lastly, a change over to digital technology is essential to create a fully digital
'filmless' radiology department and fully reap the benefits of implementing
RIS and PACS programs.
130. Advances in Digital Radiography: Physical Principles
and System Overview - May 2007
RadioGraphics, 27, 675-686.
Artifacts in Digital Radiography - AJR January 2012 vol.
198 no. 1 156-161.
Christensen’s : physics of diagnostic radiology.
Internet.
