U.S. patent number RE32,164 [Application Number 06/725,433] was granted by the patent office on 1986-05-27 for radiographic systems employing multi-linear arrays of electronic radiation detectors.
This patent grant is currently assigned to The University of Utah. Invention is credited to Robert A. Kruger.
United States Patent |
RE32,164 |
Kruger |
May 27, 1986 |
**Please see images for:
( Certificate of Correction ) ** |
Radiographic systems employing multi-linear arrays of electronic
radiation detectors
Abstract
A scanning radiographic system employing a multi-linear array.
The system includes a source of electronic radiation, which is
focused upon the multi-linear array. The multi-linear array
includes radiation sensors each of which is adapted to generate an
intensity signal as a function of the amount of radiation sensed
thereby. Each sensor has associated therewith a means for holding
or storing its respective intensity signals. The intensity signals
thus held may be continually up-dated to reflect subsequent
intensity signals resulting from additional radiation sensed by the
respective sensors. An opaque object to be scanned by the
radiographic system passes through the beam of radiation in a
controlled fashion. This controlled motion is synchronized and
coordinated with the shifting of the up-dated intensity signals so
that the speed and course of travel of a particular up-dated
intensity signal through the holding means of a given group of said
sensors is optically aligned with the speed and course of travel of
the radiation passing through a given area of the opaque specimen.
In this fashion, there is generated one up-dated intensity signal
corresponding to a given area of the opaque specimen. These
up-dated intensity signals are then collected and processed by a
suitable visual system.
Inventors: |
Kruger; Robert A. (Salt Lake
City, UT) |
Assignee: |
The University of Utah (Salt
Lake City, UT)
|
Family
ID: |
26906466 |
Appl.
No.: |
06/725,433 |
Filed: |
April 22, 1985 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
211792 |
Dec 1, 1980 |
04383327 |
May 10, 1983 |
|
|
Current U.S.
Class: |
378/19; 378/22;
378/98.8 |
Current CPC
Class: |
H05G
1/60 (20130101); A61B 6/06 (20130101); A61B
6/4233 (20130101); G01N 23/04 (20130101) |
Current International
Class: |
A61B
6/06 (20060101); H05G 1/00 (20060101); G01N
23/02 (20060101); G01N 23/04 (20060101); H05G
1/60 (20060101); G01N 023/00 () |
Field of
Search: |
;378/19,22,99 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
"Charge Transfer Devices for Infrared Imaging" Milton, Optical and
Infrared Detectors, 1977..
|
Primary Examiner: Anderson; Bruce C.
Attorney, Agent or Firm: Watts, Hoffmann, Fisher &
Heinke Co.
Claims
What is claimed is:
1. A radiographic system for generating a radiograph-type image of
an opaque specimen comprising:
means for generating a beam of radiation;
an array of sensors aligned with said beam comprising:
a plurality of sensors, each adapted to sense and signal the
intensity of any radiation falling thereon,
signal connection means for connecting said sensors of said array
in columns, said signal connection means being adapted to allow
signals from each of said sensors of a given column to be shifted
to an adjacent sensor of said given column in response to a shift
control signal, and
data output means for outputting signals from said columns in
response to an output control signal;
image display means responsive to said outputted signals from said
data output means for producing an image representative of said
outputted signals;
motion means for transversing said beam of radiation with said
opaque specimen in a direction that is substantially parallel with
said columns of said sensors; and
synchronization means for generating said shift control and output
control signals and synchronizing them with the relative motion
between said opaque specimen and said beam of radiation, whereby
said opaque specimen passes through said beam of radiation at
substantially the same rate as said signals of said sensors are
shifted along said columns of sensors of said planar array.
2. A radiographic system as defined in claim 1 wherein said data
output means comprises a shift register having a plurality of
elements adapted to shift a signal from one element of said
register to an adjacent element of said register in response to
said output control signal, an end element of said register having
an output port through which said signals may be serially outputted
to said image display means, and each element of said register
having an input port coupled to an end sensor of a respective
column of said sensors, whereby said signals being shifted through
said columns in response to said shift control signal may be loaded
in parallel into said shift register.
3. A radiographic system as defined in claim 2 wherein said output
control signal operates at a substantially faster rate than said
shift control signal, whereby said shift register, in response to
said output control signal, may be completely emptied in serial
fashion before being reloaded in parallel in response to said shift
control signal.
4. A radiographic system as defined in claim 3 wherein the
frequency of said output control signal is at least n.times.f,
where f is the frequency of said shift control signal and n is the
number of elements in said shift register.
5. A radiographic system as defined in claim 3 wherein said motion
means comprises:
a holding surface onto which said opaque specimen may be placed,
said holding surface being adapted to allow said radiation to pass
therethrough;
drive means for moving said holding surface through said beam.
6. A radiographic system as defined in claim 5 further including
lens means for focusing said beam of radiation onto said array
after said beam has passed through said holding surface and opaque
specimen.
7. A radiographic system as defined in claim 6 further including
image intensifier means for collecting and intensifying said beam
of radiation after said beam has passed through said holding
surface.
8. A radiographic system as defined in claim 5 wherein said image
display means comprises:
an image data processor for buffering and processing the outputted
signals received from said data output means;
image storage means coupled to said image data processor for
storing said buffered and processed signals; and
an image display coupled to said image data processor for receiving
said buffered and processed signals and converting them to an image
representative of said buffered and processed signals.
9. A radiographic system as defined in claim 8 wherein said image
display comprises a cathode-ray tube.
10. A radiographic system as defined in claim 5 wherein said array
comprises a two dimensional charge coupled device, wherein each of
said sensors comprises a photodetector, each of said photodetectors
being adapted to generate an electrical charge proportional to the
intensity of the radiation falling thereon, said two dimensional
charge coupled device including:
a first group of charge transfer gates connecting different groups
of said photodetectors in series in a first dimension so as to form
a plurality of photodetector columns, said first group of charge
transfer gates comprising said signal connection means and being
adapted to allow the electrical charges generated by said
photodetectors to be serially shifted through said photodetector
columns in response to said shift control signal; and
a second group of charge transfer gates connecting an upper end of
said photodetector columns in a second dimension so as to form a
charge transport row, said charge transfer row comprising said data
output means and being adapted to allow electrical charges from
said photodetector columns to enter thereinto in parallel and be
serially shifted thereacross in response to said output control
signal.
11. A radiographic system as defined in claim 10 wherein said data
output means further includes an output gate connected in series
with said charge transport row, said output gate being responsive
to said output control signal and being adapted to interface said
charge transport row with said image display means, whereby the
electrical charges being shifted across said charge transport row
may be serially passed through to said image display means.
12. A method for producing a radiograph-type image of an opaque
specimen having increased resolution and imaging speed, comprising
the steps of:
(a) constructing a multi-linear array having a plurality of
radiation sensors arranged in columns and rows thereon, each of
said sensors being adapted to generate an intensity signal
proportional to the intensity of the radiation sensed thereby, and
each of said sensors having a storage element connected
thereto;
(b) aligning a beam of radiation with said multi-linear array;
(c) storing said intensity signals of each sensor in its respective
storage element;
(d) shifting the intensity signals stored in each of said storage
elements to a different storage element at controlled time
intervals, said adjacent storage element being connected to a
radiation sensor that is adjacent to the radiation sensor having
the storage element from where the intensity signals are
shifted;
(e) augmenting the intensity signals of said storage elements after
the shifting of step (d) in order to account for newly generated
intensity signals received from the respective radiation sensors
connected to each of said storage elements;
(f) creating relative motion between said opaque object and said
array, said opaque object moving with respect to said array at a
controlled speed;
(g) synchronizing the shifting of step (d) with the relative motion
of step (f) so that the augmenting of step (e) is always based on
intensity signals derived from sensed radiation passing through
substantially the same small cross-sectional areas of said opaque
object.
(h) repeating step (d), (e), (f), and (g) until the opaque object
has passed completely through said beam of radiation,
(i) processing the augmented signals to create a radiograph-type
image, each of said augmented signals representing the accumulated
radiation that has passed through a specific small cross-sectional
area of said opaque object during the time said opaque object was
moving through said beam of radiation.
13. A method for producing a radiograph-type image as defined in
claim 12 wherein step (a) of contructing a multi-linear array
comprises constructing said array from a two dimensional charge
coupled device.
14. A method as defined in claim 12 wherein step (f) of creating
relative motion between said opaque object and said array comprises
fixing said array and said beam of radiation and passing said
opaque object therebetween.
15. A method as defined in claim 12 wherein step (f) of creating
relative motion between said opaque object and said array comprises
fixing said opaque object and moving said array therebelow and said
beam of radiation thereabove.
16. A scanning radiographic system comprising:
a multi-linear array having a plurality of radiation sensors lying
in a single plane and arranged in an ordered fashion, each of said
sensors being adapted to generate an intensity signal proportional
to the intensity of the radiation sensed thereby, said multi-linear
array including:
holding means for holding the intensity signals generated by each
of said radiation sensors, each of said holding means being adapted
to up-date the intensity signal held therein with other newly
generated intensity signals resulting from additional radiation
sensed by its respective sensor,
first shifting means for serially shifting said up-dated signals
through the holding means associated with defined groups of said
sensors in response to a first clock signal, said defined groups of
sensors comprising specified patterns of said radiation sensors,
and
second shifting means for serially shifting said up-dated signals
out of the holding means associated with at least one of the
sensors of each of said defined groups of sensors in response to a
second clock signal;
a clock source for generating said first and second clock
signals;
placement means for placing an opaque specimen to be scanned by
said radiographic system above said multi-linear array;
motion means for creating relative motion between said placement
means and multi-linear array, said motion means being adapted to
cause the relative motion thus created to follow a source
substantially the same as said specified patterns;
a source of radiation placed above said placement means for
directing a beam of radiation through said opaque specimen and onto
said array; and
synchronization means for synchronizing said motion means with said
first clock signal, whereby the speed and course of travel of a
particular updated signal through the holding means of a given
group of said sensors is optically aligned with the speed and
course of travel of the radiation passing through the given area of
said opaque specimen.
17. A scanning radiographic system as defined in claim 16 further
including data processing means adapted to receive said up-dated
signals from said second shifting means in response to said second
clock signal.
18. A scanning radiographic system as defined in claim 17 wherein
said data processing means includes
an image data processor to receive, process, and manipulate said
up-dated signals; and
an image display responsive to said processed and manipulated
up-dated signals for displaying an image that is derived from said
signals.
19. A scanning radiographic system as defined in claim 18 wherein
said multi-linear array comprises a charge coupled device.
20. A scanning radiographic system as defined in claim 19 wherein
said radiation sensors are arranged in tightly compacted columns
and rows lying on the plane of said array.
21. A scanning radiographic system as defined in claim 20 wherein
said first shifting means includes a plurality of vertical shift
registers, each of said vertical shift registers being coupled to a
respective column of said radiation sensors.
22. A scanning radiographic system as defined in claim 21 wherein
said second shifting means comprises a horizontal shift register
coupled to one end of said plurality of vertical shift registers.
.Iadd.
23. A medical diagnostic imaging system for producing an image of a
subject by use of penetrative radiation, said system
comprising:
(a) a source for propagating penetrative radiation along a
path;
(b) an array of sensors, each including means to produce a signal
representing radiation when incident thereon, at least partially
interposed in the path and spaced from the source to accommodate a
subject therebetween;
(c) signal connection means for coupling said sensors in at least
one series and including means for facilitating shifting of said
radiation representing signals produced by said sensors of said
series along said series in response to shift control signals;
(d) data output means for outputting signals from said series;
(e) image display means responsive to said outputted signals for
producing a representation of an image of radiation corresponding
to said outputted signals;
(f) motion means for generating relative motion between said array
of sensors and said subject, and
(g) synchronization means for generating said shift control signals
and causing synchronism between the occurrence of said shift
control signals and said relative motion between said subject and
said array. .Iaddend. .Iadd.24. A medical diagnostic imaging system
utilizing penetrative radiation for producing an image of internal
structure of a subject, said system comprising:
(a) a source of propagating penetrative radiation along a path;
(b) an array of sensors, each including means for producing a
signal representing penetrative radiation when incident thereon,
said array being at least partially interposable in the path and
spaced from said source to accommodate a subject therebetween;
(c) signal connection means for coupling a plurality of said
sensors in a series defining a second path, said signal connection
means including means for cumulatively shifting said radiation
representing signals produced by said sensors of said series in a
first sense extending along said second path in response to a
sequence of shift control signals;
(d) means for producing said shift control signals;
(e) data output means for outputting shifted signals from said
series;
(f) image display means responsive to said outputted signals for
producing a representation of radiation emergent from the subject
and to which said outputted signals correspond;
(g) motion means for generating relative motion between said array
of sensors and said subject, said motion defining a path
corresponding to said second path, in a second sense generally
opposite said first sense, and
(h) synchronization means for causing synchronism between said
shift control signals and said relative motion between said subject
and said array. .Iaddend. .Iadd.25. A medical diagnostic system for
producing an image of a subject by use of penetrative radiation,
said system comprising:
(a) a source for propagating penetrative radiation along a first
path;
(b) an array of sensors, each sensor including means to produce an
electrical signal representing radiation when incident on a portion
of said sensor, said array being at least partially interposable in
said first path and further being spaced from said source to
accommodate a subject therebetween in said first path;
(c) signal connection circuitry for connecting a plurality of said
sensors in a series and including means for facilitating cumulative
stepwise shifting of said radiation representing signals produced
by said sensors of said series in a first direction along said
series in response to a plurality of shift control signals, the
average velocity of said shifting being a function of the frequency
of occurrence of said shift control signals;
(d) means for producing said shift control signals;
(e) data output means for outputting said cumulatively shifted
signals from said series of sensors at a rate which is a function
of the rate of occurrence of said shift control signals;
(f) motion means for generating relative synchronizing motion
between said series of sensors and said subject in a second
direction generally opposite to, and at an average velocity which
is a function of, said velocity of said cumulative shifting of said
radiation representing signals, and
(g) image display means responsive to said outputted signals for
producing a representation of an image of radiation corresponding
to said outputted signals. .Iaddend. .Iadd.26. A medical diagnostic
imaging method for producing an image of a subject by use of
penetrative radiation, utilizing a source for propagating
penetrative radiation along a path and an array of penetrative
radiation sensors arranged in a series to define a second path and
spaced from the source to accommodate placement of at least a
portion of a subject in the path between the source and the array
of sensors, said method comprising the steps of:
(a) interposing the array of sensors in the path;
(b) producing by the use of the sensors electrical signals
representing penetrative radiation incident on the sensors;
(c) generating relative motion between said array of sensors and
said subject along a path corresponding generally to said second
path;
(d) producing shift control signals with synchronism between said
shift control signals and said relative motion between said subject
and said array;
(e) shifting said radiation representing signals produced by said
sensors of said series along said second path defined by said
series in response to said shift control signals;
(f) outputting said radiation representing signals from said
series, and
(g) producing a representation of an image of said radiation in
response to
said outputted signals. .Iaddend. .Iadd.27. A method for producing
an image of a subject by use of penetrative radiation, utilizing a
source for propagating penetrative radiation along a first path,
and an array of sensors, spaced from said source and interposable
in said first path, each sensor including means to produce an
electrical signal representing radiation when incident on a portion
of said sensor, said array including a series of sensors whose
geometrical arrangement defines a second path extending
substantially along said series of sensors, said method comprising
the steps of:
(a) generating relative motion between said series of sensors and
said subject in a first direction generally along said second
path;
(b) producing a series of shift control signals;
(c) cumulatively shifting in stepwise fashion said radiation
representing signals produced by said sensors of said series in a
second direction along said second path in response to said
sequence of shift control signals, the average velocity of said
shifting being a function of the rate of occurrence of said shift
control signals and of said motion;
(d) outputting said cumulatively shifted signals from a member of
said series of said sensors, and
(e) producing, in response to said outputted signals, an image of
penetrative radiation incident on said series of sensors. .Iaddend.
.Iadd.28. A radiographic system for generating a radiograph-type
image of an opaque specimen comprising:
means for generating a beam of radiation;
an array of sensors aligned with said beam comprising:
a plurality of sensors, each adapted to sense and signal the
intensity of any radiation falling thereon,
signal connection means for connecting said sensors of said array
in columns, said signal connection means being adapted to allow
signals from each of said sensors of a given column to be shifted
to an adjacent sensor of said given column in response to a shift
control signal, and
data output means for outputting signals from said columns in
response to an output control signal;
image display means responsive to said outputted signals from said
data output means for producing an image representative of said
outputted signals;
motion means for transversing said beam of radiation relative to
said opaque specimen in a direction that is substantially parallel
with said columns of said sensors, and
synchronization means for generating said shift control and output
control signals and synchronizing them with the relative motion
between said opaque specimen and said beam of radiation, whereby
said opaque specimen passes through said beam of radiation at
substantially the same rate as said signals of said sensors are
shifted along said columns of sensors of said planar array.
.Iaddend. .Iadd.29. A radiographic system for producing an image of
a subject, said system comprising:
(a) a source of propagating penetrative radiation along a path;
(b) an array of sensors, each including means to produce a signal
representing radiation when incident thereon, at least partially
interposed in the path and spaced from the source to accommodate a
subject therebetween;
(c) signal connection means for electrically coupling said sensors
in at least one series of sensors having a plurality of members and
including means for facilitating shifting of said radiation
representing signals produced by said sensors of said series along
the members of said series in response to a shift control
signal;
(d) data output means for outputting shifted signals from said
series in response to output control signals;
(e) image display means responsive to said outputted signals for
producing a representation of an image of radiation corresponding
to said outputted signals;
(f) motion means for generating relative motion between said array
of sensors and said subject in a direction extending along said
series, and
(g) synchronization means for generating said shift control signals
in synchronism with said output control signals and with said
relative motion
between said subject and said array. .Iaddend. .Iadd.30. A medical
diagnostic imaging system utilizing penetrative radiation for
producing an image of internal structure of a subject,
comprising:
(a) a source for propagating penetrative radiation along a first
path;
(b) an array of sensors, each sensor including means for producing
a signal representing penetrative radiation when incident on at
least a portion of said sensor, said array being partially
interposable in said first path and spaced from said source to
accommodate placement of a subject therebetween;
(c) motion means for generating relative motion between said array
of sensors and said subject;
(d) time delay and integrate circuitry coupled to said array of
sensors and said motion means for cumulatively shifting radiation
representing signals along a series of said sensors synchronized as
a function of said motion and for outputting said shifted signals,
and
(e) imaging means responsive to said outputted signals for
producing an image of radiation. .Iaddend.
Description
BACKGROUND OF THE INVENTION
This invention relates to radiographic and other similar systems
used to create an image of an opaque specimen by sensing the
intensity of a beam of electronic radiation passed therethrough. In
particular, the invention relates to scanning slit electronic
radiographic system employing multi-linear arrays of electronic
radiation detectors.
Broadly speaking, radiography is defined as the technique of
producing a photographic image of an opaque specimen by
transmitting a beam of electronic radiation through the specimen
onto an adjacent photographic film. An image results because the
variations in thickness, density, and chemical composition of the
specimen block or absorb some of the radiation energy, thereby
causing the intensity of the radiation that does strike the
photographic film (or other sensor) to be a function of the
specimen through which it has passed. Radiography is primarily used
in the fields of medicine and industry.
Electronic radiographic systems employ electronic detectors rather
than photographic film to sense the amount of electronic radiation
that passes through the opaque specimen. Signals generated by the
electronic detectors are then processed to form an image which may
be displayed on an appropriate electronic device, such as a cathode
ray tube. This process of using electronic detectors is broadly
referred to as electronic image detection.
Electronic image detection has had a revolutionary impact on
radiography in recent years. This is because, in a large part, of
the many and varied mathematical and analytical tools available for
the processing of the data generated by the electronic radiation
detectors. These analytical tools are easily and economically used
by means of modern day computers, which makes the handling and
processing of large amounts of data a relatively easy task.
In the prior art of radiographic systems, three specific areas have
emerged which have had a significant impact on electronic image
detection. These areas are: (1) fluoroscopy, (2) computed
radiography, and (3) computed tomography. Each of these systems
uses different approaches in gathering radiographic image
information and combining it to form a desired image.
Fluoroscopy is a term that historically relates to the use of a
fluoroscope for X-ray examination. A fluoroscope was a florescent
screen, or a screen covered with phosphors, designed for use with
an X-ray tube or other suitable source of radiation. Radiation
striking the fluoroscope would cause the phosphors to emit light,
thereby permitting a direct visual observation of X-ray shadow
images of objects interposed between the X-ray tube and the screen.
Because fluoroscopy allowed an entire image to be displayed at one
time, the term has more recently come to mean a radiographic system
displaying an image representing a relatively large area of the
opaque specimen. Typically, fluoroscopy involves the use of some
sort of image intensifier and video system to allow an entire image
to be viewed at one time.
Computed fluoroscopy (hereinafter CF) refers to a combination of an
image intensifier and video system plus a high speed digital image
processor. The purpose of the processor is to convert the
fluoroscopic image to a matrix of appropriate digital signals that
can be stored and linearly processed, and eventually displayed.
The most successful use of CF to date has been in the area of time
dependent image subtraction. That is, if a low image contrast is
present in the fluoroscopic image (such as might exist when iodine
is selectively inserted into the opaque specimen so as to provide
known attenuation properties of the electronic radiation), CF can
be used to enhance the contrast and allow visualization of many
internal features of the opaque specimen that were previously not
clearly visualized.
Because CF requires the use of a large area image intensifier as
well as a video system, the limitations of CF are primarily those
of its constituent elements. In particular, the image intensifier
limits CF in three ways. First, the field size is presently limited
to about 7" diameter (in the opaque specimen) by the currently
available 9" image intensifier. As larger image intensifiers are
developed (such as a 14" image intensifier being marketed by
Phillips Corporation at a cost of over $100,000), larger field
sizes will be possible at a significant increase in cost. Besides
being very expensive, such systems are bulky, heavy, and therefore
require elaborate suspension systems in order reduce their
cumbersome maneuverability. Moreover, even these larger image
intensifiers are not capable of imaging the typical 14" by 17"
field size typically used in chest radiography in the field of
medicine.
A second limitation of the image intensifier is the problem of
scattered radiation. This is a common problem shared by all prior
art large area detectors, and it is particularly noticable for
large field sizes and thick specimens. Scattered radiation not only
reduces image contrast, but it reduces dose efficiency. That is,
the patient (or other opaque specimen) requires an increased
exposure of radiation in order to prevent degradation of the image
quality. While there are techniques to increase dose efficiency,
such as conventional scatter grids, they are not without their
cost. For example, conventional scatter grids absorb significant
fractions of primary radiation (typically about 40%), thereby
reducing the power efficiency of the system. And while other
scatter reduction devices have been found which provide little or
no attenuation, such as scanning slits or multiple slots, the use
of such devices increase the required imaging time.
A third limitation associated with large image intensifiers is the
presence of "veiling glare" in the image formation process. Veiling
glare results from both electron scatter within the image
intensifier as well as light scatter from the input and output
phosphors that have been used therein. The presence of veiling
glare degrades image quality in much the same way as does the
detection of scattered radiation. The amount of glare also
increases with field size. For example, in modern day image
intensifiers the veiling glare may be anywhere from 10% to 40%
depending upon the field size and type of image intensifier
employed. It would therefore be an improvement in the art if a
large field size, or equivalent, could be obtained without the
attendant problems of scattered radiation and veiling glare.
A second prior art technique or method that has evolved in recent
years is that of computerized radiography (hereinafter CR).
Computerized radiography eliminates the need to use large area
detectors by incorporating a fan beam of radiation used in
connection with a linear array of detectors. The fan beam of
radiation, as its name implies, is a long, but narrow, beam of
radiation that falls upon a small linear region of the opqaue
object at any one time. The width of the fan beam is typically 1 to
3 mm. A large image is formed by passing the opaque object through
the fan beam of radiation at a constant velocity with the X-rays
(or other radiation) being pulsed once for each fan beam width of
travel of the opaque object. Thus, a two-dimensional image is
gradually built up one line at a time. This image has the
resolution of the width of the fan beam which as mentioned is
typically 1 to 3 mm.
The advantages of CR are many. First, it offers excellent radiation
scatter rejection in that the radiation is limited to a very narrow
area. Secondly, there is little or no primary attenuation
associated with CR because the use of conventional scatter grids is
not required. Thirdly, as large an image as is required can be
obtained simply by scanning the area over which the image is to be
formed until the desired image is built up line by line. Fourthly,
veiling glare, or lateral communication of the image information,
is minimized because of the limited detector area.
Computerized radiography, or CR, is not without its disadvantages,
however. One main disadvantage is the poor image resolution that is
achieved, typically being 1 to 3 mm. Secondly, the imaging time is
quite long. Typically, the opaque specimen can only travel at a
speed of from 2 to 6 centimeters per second because each image
element must be exposed for a minimum time. Typically, a large
number of photons must be detected for each image element in order
to have a useful image. However, the number of photons, or photon
flux, that is available from the radiation source (such as X-ray
tubes) is limited by heat loading constraints. Thus, the number of
photons striking the imaging element must be controlled by the
speed of the opaque specimen. The total imaging time then becomes
the product of the number of image lines (which is usually around
250 for a typical radiography image) and the exposure time per
line. In contrast, the imaging time for computerized fluoroscopy is
much shorter because all 250 lines (or whatever number of lines are
employed) are formed simultaneously.
Some prior art techniques have been used in order to decrease the
imaging time associated with CR. For example, it is possible to
design the source of radiation so that it may operate at a higher
voltage thereby increasing the flux density as well as the tissue
penetration. However, the disadvantge of such higher voltages is a
loss of contrast for certain types of popular imaging substances
that are selectively inserted into the patient or other opaque
specimen. This is particularly true with iodine which is a commonly
used substance injected into patients so as to highlight certain
systems within their bodies.
It would therefore be desirable to develop a system that provided
the advantages of computerized radiography while at the same time
improving the image resolution and the imaging time. A radiographic
system achieving this desired goal is described herein.
SUMMARY OF THE INVENTION
A general object of the present invention is to provide a
radiographic system that allows a large area image to be generated
with good resolution in a relatively quick imaging time.
A particular object of the present invention is to improve the
present single linear array detection capability in two ways: (1)
to improve the resolution, and (2) to increase the imaging
speed.
A further object of the present invention is to provide a
radiographic system that employs scatter reduction devices having
desirable scatter rejection properties without undesirable
attenuation and loss of resolution.
Another object of the present invention is to provide a
radiographic system capable of generating a large area image in a
short time without using needlessly high voltages, nor requiring
the use of heavy, cumbersome, bulky equipment.
An additional object of the present invention is to provide a
radiographic system that eliminates veiling glare.
Still a further object of the present invention is to provide such
a radiographic system that employs a multilinear electronic
radiation array that is lightweight, relatively inexpensive, easy
to operate, and reliable in its performance.
Still an additional object of the present invention is to provide
such a radiographic system that offers improved dose efficiency and
power efficiency.
The above and other objects of the present invention are realized
in an illustrative embodiment that includes a beam of electronic
radiation generated by a suitable source of electronic radiation.
The beam of electronic radiation is directed towards, and aligned
with, an array of electronic radiation detectors. Each of the
detectors on the array is adapted to generate a signal having a
magnitude proportional to the amount of radiation it senses. The
array also includes, as an integral part thereof, signal processing
capabilities whereby the signals generated by each of the detectors
may be stored in respective storage elements. These stored signals,
at controlled time intervals, are all shifted to the storage
elements of other, adjacent, detectors. Once the signals have been
shifted, the signals are augmented by new signals, if any,
generated by the respective detectors of the storage elements in
which the signals are stored. After having been shifted through
several storage elements, these augmented signals may exit from the
array to be further processed and conditioned so as to enable an
image to be created through a suitable visual system.
In connection with the above shifting and processing of radiation
signals, the opaque specimen is passed between the source of
electronic radiation and the array at a controlled speed and in a
known pattern. This controlled speed is synchronized with the
controlled time intervals at which the signals are shifted from
storage element to storage element. Furthermore, the shifting
pattern--that is the sequence that the signals follow as they are
shifted from storage element to storage element within the
array--is designed to be the same as the movement pattern of the
opaque specimen through the beam of electronic radiation. When the
shifting pattern of the detector signals is the same as the
movement pattern of the opaque specimen, a non-blurred image may be
generated. That is, each pixel, or small area, of the image is
generated from radiation that passes through a corresponding small
area of the specimen. At any instant of time, this radiation falls
upon a given detector and generates a signal for that pixel. As the
specimen moves, causing the radiation passing through the same
small area thereof to likewise move and fall upon an adjacent
detector, the pixel signal generated prior to the movement is
shifted to the storage element associated with the detector
receiving the radiation after the movement. At each storage
element, the resolution of the pixel signal is augmented by having
it updated to reflect the amount of radiation passing through the
corresponding area of the specimen at that particular time. In this
fashion, each pixel in the accumulated image results from an
integration process. This process is commonly referred to as a time
delay and integration (TDI) mode.
In one embodiment of the invention, the two dimensional array is a
charge coupled device (CCD) which is operated in the TDI mode. The
charge coupled device includes columns of image sensing elements
that are tied to a vertical analog transport register. At the top
of each vertical analog transport register is a horizontal analog
transport register. The image sensing elements generate packets of
electrical charge as a function of the radiation sensed thereby.
These charge packets are passed along the column shift registers.
After the charge packet which resulted from the charge accumulated
at a first image sensor in a column of the CCD array has passed to
a second element in the same column, the charge which accumulates
at the second sensor is added to that already in the register. In
this way, charge is accumulated at each successive point along the
register until it passes into the horizontal shift register. When
the opaque specimen is scanned along the CCD matrix in the same
direction as the columns and at the same rate as the charge is
passed from line to line (each line representing a row of image
sensing elements), a non-blurred image results with each pixel in
the accumulated image being the result of N T seconds of
integration, where N is the number of lines in the detector, and T
equals 1/F, F being the clocking frequency of the vertical shift
registers. The horizontal analog transport register is loaded in
parallel with charge packets from each vertical analog transport
register, in response to the vertical clock signal. These charge
packets may be serially clocked out of the horizontal analog
transport register at a sufficiently fast rate so as to completely
empty it prior to having it reloaded in parallel fashion at the
next clocking frequency of the vertical shift register. The charge
packets exiting the horizontal register may then be sent to an
appropriate data processor where they can be digitized and
processed so as to create and display a visual image.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features, and advantages of the
invention will be more apparent from the following more particular
description presented in connection with the accompanying drawings,
in which:
FIG. 1 is a perspective representation of a scanning radiography
system employing a multi-linear array;
FIG. 2 is a block diagram of an m.times.n multi-linear array;
FIG. 3 is a timed schematic representation of a two-phase charge
coupled device shift register, including clock signals, showing how
finite bundles of charge are shifted from one storage element to
another; and
FIG. 4 is a block diagram of a scanning radiography system
employing a multi-linear array, including a suitable visual system
and a controlled-motion specimen table.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention herein disclosed is best understood by reference to
the figures wherein like parts are designated with like numerals
throughout.
Referring first to FIG. 1, there is shown a perspective
representation of a scanning radiography system of the type herein
disclosed as it could be employed for a medical application. A
source of electronic radiation 10, such as an X-ray tube, generates
a beam of electronic radiation 12. This electronic radiation, or
ER, passes through a slit 14 of a collimator 16. The purpose of the
collimator 16 is to form the ER beam 12 into a fan beam,
represented symbolically in FIG. 1 by the dotted lines 18. The fan
beam 18 is directed towards an image intensifier 20. At the point
where the fan beam 18 strikes the upper surface of the image
intensifier 20, shown generally at 22 in FIG. 1, it covers an area
of from 1 to 2 cm. wide by about 20 to 25 cm. long. The upper
surface of the image intensifier 20, designated as 24, is suitably
adapted to interface with a specimen table 26 upon which a patient
or other opaque object 28 may be placed. The specimen table 26 is
then caused to move over the upper surface of the image intensifier
24, thereby allowing the fan beam 18 to selectively penetrate those
portions of the patient 28 that are to be examined.
As the ER fan beam 18 passes through a patient 28, or other opaque
object, various amounts of the radiation will be absorbed depending
upon the thickness, density, and chemical composition of the
specimen. In particular, for medical applications, it is quite
common to inject a substance having known absorption properties,
such as iodine, into the patient 28 so that those portions of the
patient (e.g., the circulatory system) having the iodine therein
will be visual on the ultimate radiography image that is produced.
For purposes of this application, it is sufficient to note that the
ER fan beam 18 exiting from the patient 28 will have a non-uniform
intensity due to the physical and chemical makeup of the patient
through which it has passed. This non-uniform radiation is
intensified by the image intensifier 20 and directed to a lens 30,
or other suitable optically focusing device, which directs and
focuses the radiation upon the surface of a multi-linear array
32.
In order to fully appreciate and understand the invention herein
disclosed, it will be helpful to understand the operation of the
multi-linear array 32. Accordingly, a block diagram of the
preferred embodiment of a multi-linear array 32 is shown in FIG. 2.
The array 32 comprises a plurality of image sensing elements 40
arranged in a particular pattern. In FIG. 2, for example, these
image sensing elements 40 are arranged in a plurality of columns
42a, 42b, . . . 42m where m is a finite integer. The first image
sensing elements 40 of the columns 42a, 42b . . . 42m are mutually
aligned so as to form a row of image sensing elements 44a.
Subsequent rows of image sensing elements 44b, 44c, . . . 44n are
similarly formed by the second, third, . . . and nth image sensing
elements 40 of each column, where n is also a finite integer. Thus
configured, it is seen that the image sensing elements 40 comprise
an m by n array of image sensing elements.
In the preferred embodiment, as shown in FIG. 2, each of the image
sensing elements 40 arranged in the first column of sensors 42a are
tied to a first vertical shift register 46a. Similarly, the image
sensing elements of the column 42b are coupled to a second vertical
shift register 46b. The shift registers of each succeeding column,
up through 42m, are likewise connected to respective vertical shift
registers. A horizontal shift register 48 is coupled to each of the
vertical shift registers 46a, 46b, . . . 46m, so as to allow the
contents of the vertical shift registers to be loaded in parallel
into the horizontal shift register 48.
The vertical shift registers 46a, 46b, . . . 46m are controlled via
a vertical shift clocking signal 50 directed to each register over
signal bus 52. Similarly, a horizontal shift clocking signal 54 is
directed to the horizontal shift register 48 over a separate signal
bus 56. As depicted in FIG. 2, the vertical shift registers 46a,
46b, . . . 46m, as well as the horizontal shift register 48, are
parallel-in, serial-out registers. Each of the vertical shift
registers receives parallel input data from the image sensing
elements 40 connected thereto. The horizontal shift register 48, on
the other hand, receives parallel input date from each of the
vertical shift registers.
Each of the image sensing elements 40 is adapted to generage a
signal as a function of the intensity of the radiation falling
thereupon. Thus, for example, the first image sensing element of
column 42a generates a signal that is directed to the vertical
shift register 46a over the signal line 58. This signal is stored
in a respective storage element of the vertical shift register 46a.
Similar storage elements are present in the vertical shift register
46a for each of the image sensing elements 40 connected thereto.
For convenience, these storage elements will be referred to as the
first, second, third, . . . nth storage elements of their
respective shift registers. When the appropriate vertical shift
clocking signal is present, the signal stored in the first storage
element of a given vertical shift register is shifted to the second
storage element of the same register. Simultaneously, the signal
stored in the second storge element is shifted to that of the third
storage element, and so on, with the signal stored in the nth
storage element being shifted out of the vertical shift register
into the horizontal shift register 48. As a given signal is thus
shifted up through one of the vertical shift registers 46a, 46b, .
. . , or 46m, it passes through the storage elements corresponding
to each of the image sensing elements 40 of the respective column
42a, 42b, . . . or 42m attached to that particular shift register.
While the signal is present in each of these storage elements, it
may be augmented by additional signals received from the respective
image sensing element 40. This augmentation is explained more fully
below.
To illustrate the above process, consider a signal X.sub.1 that is
generated by the first image sensing eleent 40 of the first column
42a. This signal is stored in the first storage element of the
vertical shift register 46a. In response to the vertical shift
clocking signals 50, this signal X.sub.1 will be shifted to the
second storage element of the shift register 46a. While there, it
will be augmented with an additional signal. X.sub.2, generated by
the second image sensing element 40 of the column 42a. Thus, the
signal present in the second storage element of the shift register
46a is now X.sub.1 +X.sub.2. In response to the next vertical shift
clocking signal 50, this signal, X.sub.1 +X.sub.2, will be shifted
to the third storage element of the shift register 46a. While
there, it will be augmented with a signal X.sub.3 generated by the
third image sensing element 40 of the column 42a. In a like manner,
the signal is augmented at each of the storage elements of the
shift register 46a as it is shifted therealong. Thus, the signal
that ultimately is shifted out of the shift register 46a into the
horizontal shift register 48 is a signal, X.sub.T that may be
expressed as: ##EQU1## where X.sub.i represents the signal
generated by the ith image sensing element 40 at the ith time
interval as defined by the vertical shift clocking signal 50.
In order to empty the horizontal shift register 48 of all the
signals that have been loaded in parallel therein with response to
the vertical shift clocking signal 50, it is necessary that the
horizontal shift clock signal 54 operate at a frequency that is at
least m times as fast as the frequency of the vertical clocking
signal 50. This is because the horizontal shift register 48 will
typically be comprised of a series of storage elements similar to
the vertical shift registers 46a, 46b, . . . 46m; and in order for
a signal to be shifted from the extreme left of the horizontal
shift register 48 (as depicted in FIG. 2) through all of these
storage elements and out of the serial data output bus 60 at the
opposite end thereof, it is necessary that at least m horizontal
clocking signals occur in order to completely empty the horizontal
shift register 48 of all the signals stored therein.
A preferred method of constructing the multi-linear array 32 shown
in FIG. 2, although not the only method that could be used, is
through the use of a two dimensional charge coupled device (CCD). A
CCD device offers the advantage of allowing the vertical shift
registers 46a, 46b, . . . 46m, at well as a horizontal shift
register 48, to be easily fabricated on the same substrate as the
image sensing elements 40. The operation of a two-phase CCD shift
register, while not novel to this invention, is depicted in FIG. 3
and is presented herein as being exemplary of how the multi-linear
array 32 may be constructed and operated.
In FIG. 3, two complimentary clock voltage waveforms .phi..sub.1
and .phi..sub.2 are respectively connected to alternate
closely-spaced gate electrodes on the surface of a thin insulating
layer 68 on a piece of silicone 66. An upper layer 64 of the
silicone is n-doped. The substrate 62 of the silicone is p-doped.
The .phi..sub.1 clock signal is connected to alternately spaced
gate electrodes 70a, 70b, 70c, . . . Similarly, the clock voltage
.phi..sub.2 is connected to the alternately spaced gate electrode
72a, 72b, 72c, . . . The dotted line 74 is symbolic of the
potential wells created by the clock voltage waveforms .phi..sub.1
and .phi..sub.2. That is, a deep potential well which attracts
electrons is created under an electrode where the clock voltage is
high and disappears under an electrode where the clock voltage is
low. Thus, in FIG. 3(a), which represents in reference to the
waveforms depicted at the top of the figure the condition at time
t=0, the potential well under gate electrodes 70a, 70b, and 70c is
low (or shallow) because the clock voltage wave form .phi..sub.2
connected to each of these gate electrodes is low at that
particular time. In a similar fashion, the potential well under
electrode 72a, 72b, and 72c is deep (or large) at this time because
the clock voltage waveform .phi..sub.1 connected thereto is high.
For illustrative purposes, it is assumed that at time t=0 that a
finite charge packet of 7 electrons (represented symbolically in
FIG. 3 as seven dots shown generally at 76) is in the potential
well under gate electrode 72a in the storage element "A".
Similarly, a finite charge packet of four electrons, shown
generally at 74 is in the potential well under gate electrode 72b
is in storage element "B". At t=1/2 cycle later, FIG. 3(b), the
potential well under gate 72a has collapsed due to .phi..sub.1
having gone low and, since at the same time the adjacent electrode
70b connected to .phi..sub.2 has gone high, the seven electron
charge packet has been attracted to the new potential well under
electrode 70b, as shown generally at 80. Similarly, the charge
packet of four electrons has been attracted to the new potential
well under electrode 70c, as shown at 82. Another half cycle later,
at t=1 cycle, the potential well under electrode 70b has collapsed
with .phi..sub.2 going low as shown in FIG. 3(c). Thus, the
electron packet of seven electrons moves to the new well under
electrode 72b as shown at 84. In a like fashion, the charge packet
of four electrons has moved to the new potential well now existing
under gate electrode 72c, as depicted at 86.
In the fashion above described, a finite charge of electrons (or
other charged bundles, such as "holes") may be shifted along the
two-phase CCD shift register as controlled by the clock signals
.phi..sub.1 and .phi..sub.2. This type of shift register is
especially well suited for the application herein disclosed in that
the image sensing elements 40 typically generate a finite bundle of
charge (either holes or electrons) as a function of the radiation
intensity falling thereon. Moreover, as this finite charge is
shifted through the register, at the various storage element sites
(labeled "A", "B", & "C" in FIG. 3), it may be readily
augmented by merely adding electrons (or holes) to those already
present. Thus, by connecting a conductive path between the image
sensing element 40 and each respective storage element site, the
signals (finite charge packets of electrons or holes) generated by
each image sensing element 40 are easily added to the prior
existing signal.
CCD two-dimensional image arrays of the type that could be employed
by this invention are commercially available. For example,
Fairchild Semiconductor, Inc. manufactures a 380.times.488 image
array that is ideally suited for this invention. The model number
for such an image array is #CD221CDC. The operation of such an
array is fully detailed and understood by those skilled in
electronic art through the specification sheets that accompany such
devices.
Referring now to FIG. 4, there is shown a block diagram of a
scanning radiography system of the type disclosed herein. Portions
of the block diagram of FIG. 4 are depicted in perspective so as to
facilitate the explanation and description of the system which
follows.
As discussed in connection with FIG. 1, a source of electronic
radiation (ER) 10 generates a beam of ER radiation 12. This beam of
radiation 12 passes through a collimator 16. The purpose of the
collimator 16 is to limit the beam to a known area. This beam of
radiation 12 is symbolically represented in FIG. 4 as the wavy
arrows.
The beam of ER radiation 12 is directed towards and falls upon an
intensifier/lens unit 90. The function of the intensifier/lens unit
90 is to intensify the ER beam 12 and focus it upon the
multi-linear array 32. The multi-linear array 32 typically includes
columns 42a, 42b . . . 42m and rows 44a, 44b, 44c . . . of image
sensing elements 40 as discussed in connection with FIG. 2. The
multi-linear array 32 includes a horizontal shift register 48 at
one end thereof into which signals from the respective columns 42a,
42b, . . . 42n may be loaded. These signals, in turn, may be
serially outputted over the signal bus 60 to a video system 92.
Typically, the video system 92 will include an image data processor
94. This processor 94 interfaces with the multilinear array 32 and
converts the signals received over the signal bus 60 into a
suitable form for processing so that an appropriate image may be
created from the signals and displayed. An image storage unit 96
may be coupled to the image data processor 94 in order to allow the
image data processed by the image data processor 94 to be sampled,
held and retrieved at appropriate time intervals. Also coupled to
the image data processor 94 is an image display unit 98. This image
display unit 98 could be realized using a conventional CRT tube (in
which case the image data processor 94 would also include the
appropriate circuitry to control and energize the CRT tube) or it
could be a matrix display having a large number of small pixels
that could be individually energized in accordance with respective
control signals. Also included in the video system 92 would be a
clock source 100. The clock source 100 would generate the
appropriate vertical shift clocking signal 50 that is directed to
the columns within the array 32 over signal bus 52, as well as the
horizontal shift clocking signals 54 that is directed to the
horizontal shift register 48 of the array 32 over the signal bus
56. As shown in FIG. 4, the vertical shift clocking signal 50 could
also be used as an internal timing signal for the image data
processor 94 and the image storage unit 96. Alternatively, or
conjunctively, other appropriate internal and external timing
signals could be generated by the clock source 50.
A significant feature of the invention herein disclosed is the
control of the specimen table 26 by a table control unit 102. The
relative motion of the table 26 with respect to the ER beam 12 must
be synchronized with the clocking signals used in connection with
the vertical and horizontal shaft registers of the multi-linear
array 32. For example, the control unit 102 may move the specimen
table 26 in the direction indicated by the arrow 104 through the ER
beam 12 at a speed that is synchronized with the vertical shift
clocking signal 50 used in connection with the columns of sensors
42a, 42b, . . . 42m. This synchronization feature is of vital
importance to the invention as discussed below in connection with
the operation of the system.
The operation of the scanning radiographic system depicted in the
block diagram of FIG. 4 will now be explained. A patient, or other
opaque specimen, is placed on the specimen table 26. The specimen
table 26 is then manually (or otherwise) moved to a desirable
starting position. Once the specimen table has been moved to the
initial starting position, the ER source 10 is energized. This
energization may be continuous or pulsed. If pulsed, a clock signal
synchronized with the vertical shift clocking signal 50 as received
over the signal line 106 (shown in dotted lines) would be used to
energize the ER source 10 at the appropriate pulsed intervals.
The ER beam 12 passes through the opaque specimen, the specimen
table 26, and the intensifier/lens unit 90. The beam is
appropriately focused on the multi-linear array 32 so that except
for the effects of the opaque specimen, approximately the same
intensity would be sensed at each small area on the surface of the
array where the image sensing elements 40 (FIG. 2) are located. For
convenience of explanation, each of these small areas
(corresponding to each image sensing element 40) will be be
referred to as a photosite. Thus, in FIG. 4, the small square area
at the intersection of column 42a with the row 44a would be a
single photosite. In like fashion, the intersection of each column
with each row, as depicted in FIG. 4, also comprises a single
photosite.
In connection with the term "photosite" above described, the term
"pixel" will also prove useful in the description that follows. At
any instant of time, the radiation falling upon any single
photosite of the array 32 is passing through a corresponding pixel
of the opaque specimen 28. Thus, a "pixel" may be thought of as a
small area of the opaque specimen through which the radiation
falling upon a single photosite passes. Alternatively, a "pixel"
may be thought of as a small cross-sectional area of the
ultimately-produced radiograph image.
In operation, the radiation 12 passing through a horizontal line of
pixels of the opaque specimen 28 is directed through the
intensifier/lens unit 90 to fall upon a line of photosites located
on the multi-linear array 32. In the context of this discussion, a
"horizontal" line referrs to a line that is perpendicular to the
direction of the relative motion of the specimen table, which
direction of motion is indicated by the arrow 104. The signal
sensed at each photosite (or at each image sensing element 40 (FIG.
2)) is vertically shifted from a first line (row) of the array to
an adjacent line in response to the vertical shift clocking signal
50. At this same time, the specimen table is also shifted forward
(in the direction of the arrow 104) so that the radiation now
falling upon the second line of photosites is passing through the
same line of pixels of the opaque specimen that previously fell
upon the first line of photosites on the array 32. As this process
continues, the signals being shifted vertically along the columns
42a, 42b, . . . 42m of the array 32 each represent the accumulated
signals corresponding to a single pixel of the opaque specimen 28.
Thus, the individual pixels in the image that is ultimately
produced result from an integration process, the integration
occurring over the full length of the columns of the array 32.
After this integration has occurred, the accumulated signals are
passed into the horizontal shift register 48 and shifted serially
therefrom in response to the horizontal shift clocking signal 54.
Note that each pixel in the accumulated image is the result of
n.DELTA.t seconds of integration. where n is the number of lines or
rows in the array 32, and .DELTA.t=1/f, where f is the clocking
frequency of the vertical shift clocking signal 50.
Where a charge coupled device (CCD) multi-linear array 32, such as
is depicted in FIG. 3, is used with the invention, it is seen that
the signals associated with the sensed radiation are charged
packets of electrons (or holes) which are passed along the column
shift registers. After the charge packet which resulted from charge
accumulated at a first line of the CCD array 32 has passed to an
adjacent line, the charge which accumulates at this adjacent line
is added to that already in the shift register. In this way charges
accumulate at each successive line until they passes into the
horizontal shift register. Thus, as explained above, when an image
is scanned along the CCD array 32 at the same rate that charge is
passed from line to line, a non-blurred image results.
The above process results improved scan speed because the exposure
of each individual photosite does not need to be near as long as
prior art systems in that the total exposure may result from the
accumulated exposure after the signal has been shifted through
several photosites. Moreover, the resolution will also be improved.
For example, if the ER beam 12 were to fall upon an area that were
15 cm by 2 cm at the surface of the opaque specimen 28, and if the
resulting radiation passing therethrough were to be imaged onto a
380.times.244 array of a typical CCD device, a resolution of 0.4
mm.times.0.4 mm could be achieved. Moreover, by using an effective
exposure time of 100 milliseconds per pixel, a scan speed of 20
cm/second could be realized. It should be noted that the image
intensifier 20 (FIG. 1), which is included in the intensifier/lens
unit 90 of FIG. 4, could be either a proximity type image
intensifier or a flat florescent screen with efficient optical
coupling.
While the above description has described a system wherein the
signals or charges are shifted vertically along columns of the
multi-linear array 32 so as to be synchronized with corresponding
motion of the specimen table 26, it should be apparent that the
motion of the specimen table and the opaque object could follow any
known pattern so long as the shifting of the signals or charges
from photosite to photosite of the multi-linear array 32 also
followed the same pattern. Thus, a system could be envisioned
wherein the accumulated signals received by the image data
processor 94 could be analyzed to see if sufficient data were
present to produce a desirable image. If not, suitable controls
could be included within the video system 92 to cause the specimen
table to back up (in order to get another run of data) or to move
sideways, or diagonally, in order to get a more complete data
package to represent the image of a particular portion of the
opaque specimen. All that is required, is that such movement of the
specimen table be synchronized with the shifting of the signals so
that the augmentation of the signals at each photosite corresponds
to radiation that has passed to the same pixel area of the opaque
specimen.
The source of electronic radiation 10 will typically be an X-ray
source, although any other suitable radiation could be used, such
as gamarays. The type of radiation used will depend in large extent
to the type of opaque specimens that are to be analyzed.
The table control unit 102 could be realized with a stepper motor
(as when the ER beams 12 are pulsed rather than continuous), or it
could simply be a motor of any suitable type controlled through
known serve control techniques to synchronize the specimen table's
motion with the shifting of the signals within the array 32. It
would also be possible, of course, to keep the specimen table
stationary and move in unison the source of ER 10, the
intensifier/lens unit 90, and the array 32, thereby creating the
requisite relative motion between the ER beam 12 and opaque
specimen 28.
While the invention herein disclosed has been described by means of
specific embodiments and applications thereof, numerous
modifications and variations could be made thereto by those skilled
in radiography and electronic art without departing from the spirit
and scope of the present invention. It is therefore to be
understood that within the scope of the appended claims, the
invention may be practiced otherwise than as specifically described
herein.
* * * * *