U.S. patent application number 11/389271 was filed with the patent office on 2007-09-27 for processes and apparatus for variable binning of data in non-destructive imaging.
This patent application is currently assigned to General Electric Company. Invention is credited to Richard Aufrichtig, Paul Richard Granfors, John Robert Lamberty.
Application Number | 20070223654 11/389271 |
Document ID | / |
Family ID | 38481832 |
Filed Date | 2007-09-27 |
United States Patent
Application |
20070223654 |
Kind Code |
A1 |
Aufrichtig; Richard ; et
al. |
September 27, 2007 |
PROCESSES AND APPARATUS FOR VARIABLE BINNING OF DATA IN
NON-DESTRUCTIVE IMAGING
Abstract
Systems, processes and apparatus are described through which
non-destructive imaging is achieved, including a process for
variable binning of detector elements. The process includes
accepting input data indicative of image quality goals and
descriptors of an imaging task, as well as parameters
characterizing a test subject, relative to non-destructive imaging
of an internal portion of the test subject and determining when the
non-destructive imaging system is capable of achieving the image
quality goals using binning of more than four pixels.
Inventors: |
Aufrichtig; Richard; (Palo
Alto, CA) ; Lamberty; John Robert; (Oconomowoc,
WI) ; Granfors; Paul Richard; (Sunnyvale,
CA) |
Correspondence
Address: |
RAMIREZ & SMITH
PO BOX 341179
AUSTIN
TX
78734
US
|
Assignee: |
General Electric Company
Schenectady
NY
|
Family ID: |
38481832 |
Appl. No.: |
11/389271 |
Filed: |
March 24, 2006 |
Current U.S.
Class: |
378/116 |
Current CPC
Class: |
A61B 6/037 20130101;
A61B 6/032 20130101; A61B 6/508 20130101; A61B 6/467 20130101; A61B
6/548 20130101 |
Class at
Publication: |
378/116 |
International
Class: |
H05G 1/58 20060101
H05G001/58; H05G 1/54 20060101 H05G001/54 |
Claims
1. A process for variable binning of detector data in a
non-destructive imaging system, comprising: receiving input data
indicative of a desired image quality; receiving input data
indicative of an imaging task; receiving input data describing a
test subject or a portion of the test subject; combining the
received input data about desired imaged quality, imaging task, and
test subject with non-destructive imaging system capabilities;
determining if the non-destructive imaging system is capable of
achieving the image quality goals using binning, wherein the
capability is a reduction of one or more dose, spatial frequency
response, detective quantum efficiency and other user defined
variables; and performing binning analyses when the non-destructive
imaging system is capable of achieving the image quality goals
using binning.
2. The process of claim 1, wherein the act of determining comprises
an act of determining a dose of X-radiation consistent with binning
and dose reduction.
3. The process of claim 1, wherein the act of determining includes
an act of estimating detective quantum efficiency, and further
comprising an act of selecting among full resolution mode, two by
two binning, three by three binning, four by four binning and five
by five binning for at least a portion of a detector array.
4. The process of claim 1, wherein the act of determining includes
estimating detective quantum efficiency and dose, and further
comprising, after determining, an act of configuring a detector
array to employ fewer than all detector elements in the detector
array.
5. The process of claim 1, further comprising an act of estimating
detective quantum efficiency, image quality, dose and contrast for
a plurality of detector array operation modes including one or more
of: full resolution imaging, full field of view, two by two
binning, three by three binning, four by four binning and five by
five binning, and further comprising distinguishing those among the
estimated modes that are capable of meeting predetermined image
quality goals.
6. The process of claim 1, wherein the act of determining further
includes an act of estimating detective quantum efficiency.
7. The process of claim 1, further including acts of: configuring
an X-ray detector array in response to the act of determining;
analyzing data from the configured X-ray detector array; and
modifying configuration of the X-ray detector responsive to the act
of analyzing.
8. A non-destructive imaging system, comprising: an illumination
source configured to internally illuminate a test subject; a
detector array including a tesselation of detector elements aligned
with the illumination source opposite the test subject, each
detector element corresponding to a pixel in a full resolution
imaging mode of the detector array; a controllable driver coupled
to the detector array and cooperatively facilitating capability for
multiple functionality settings for a detector array, including
binning of more than four pixels; an interface capable of accepting
input data indicative of image quality goals and facilitating
selection of at least one of the multiple functionality settings; a
processor coupled to the interface; a storage device coupled to the
processor; and software means operative on the processor for:
determining if the detector array is capable of achieving the image
quality goals using binning, wherein the capability is a reduction
of one or more dose, spatial frequency response, detective quantum
efficiency and other user defined variables; and performing binning
analyses when the detector array is capable of achieving the image
quality goals using binning.
9. The system of claim 8, further comprising: estimate detective
quantum efficiency for several of the multiple detector array
functionality settings; distinguish among the several based on dose
and image quality goals to provide one or more candidate
functionality settings; and select one of the candidate
functionality settings.
10. The system of claim 8, wherein the illumination source
comprises an X-ray illumination source and the detector elements
include semiconductive material, each detector element being
associated with a switch coupled to the controllable driver.
11. The system of claim 8, wherein the controllable driver is
configured to selectively group the detector elements into one of a
menu of extended groups, and further comprising a control and
signal processing module configured to: combine signals from
detector elements within each extended group defined by the
controllable driver; and provide digital signals representative of
data from each of the extended groups.
12. The system of claim 8, wherein the illumination source includes
an X-ray illumination source, and further comprising a control
module configured to facilitate operation of the system in
conformance with one or more of: full resolution imaging, full
field of view imaging, two by two binning, three by three binning,
four by four binning or five by five binning, and further
comprising capability for distinguishing those among the estimated
modes that are capable of meeting predetermined image quality
goals.
13. The system of claim 8, wherein the illumination source includes
an X-ray illumination source, and wherein the system further
includes stored data descriptive of empirical characterization of
the system as well as calculated data useful in rank-ordering of
detector array functionality settings in conformance with
identified characteristics of the test subject and goals associated
with an imaging task relative to the test subject.
14. The system of claim 8, wherein the system further includes
stored data descriptive of calculated estimates of detective
quantum efficiency that are useful in rank-ordering of detector
array functionality settings in conformance with identified
characteristics of the test subject and goals associated with an
imaging task relative to the test subject.
15. The system of claim 9, wherein the illumination source
comprises an X-ray illumination source, and wherein the control
module is further configured to generate a message to an operator
of the system prior to initiation of exposure of the test subject
to X-rays.
16. The system of claim 8, further comprising: estimate detective
quantum efficiency for several of the multiple functionality
settings for the detector array; distinguish among the several
based on dose and image quality goals to provide one or more
candidate functionality settings; and select of one of the
candidate functionality settings, wherein the controllable driver
is configured to assist in determining a dose of X-radiation
consistent with binning that reduces X-ray dose exposure of the
test subject relative to the several.
17. A system for variable binning of detector data in an X-ray
system, comprising: a processor coupled to an X-ray detector; a
storage device coupled to the processor; software means operative
on the processor for: accepting input data indicative of image
quality goals and information descriptive of a test subject to be
characterized using the X-ray system; and determining when the
X-ray system is capable of achieving the image quality goals via
combining the signals from an extended group of detector elements,
wherein the capability is a reduction of one or more dose, spatial
frequency response, detective quantum efficiency and other user
defined variables; performing binning analyses when the X-ray
system is capable of achieving the image quality goals via
combining the signals; and setting the X-ray detector control
circuitry and exposure parameters in accordance to the
determination and binning analyses.
18. The system of claim 17, wherein the software means accepts
revised computer-readable information descriptive of revised
capabilities.
19. The system of claim 17, wherein the software means is further
configured to cause the processor to perform acts of: accessing
stored data descriptive of calculated estimates of detective
quantum efficiency useful in rank-ordering of detector array
functionality settings in conformance with identified
characteristics of the test subject and goals associated with an
imaging task relative to the test subject; and selecting one or
more of multiple X-ray exposure strategies.
20. The system of claim 17, wherein the software means is further
configured to cause the processor to perform acts of: estimate
detective quantum efficiency for multiple detector array
functionality settings; distinguish among several detector array
functionality settings based on dose and image quality goals to
provide one or more candidate functionality settings; and select
one of the candidate functionality settings.
Description
FIELD OF THE DISCLOSURE
[0001] This disclosure relates generally to nondestructive
evaluation, including medical diagnosis, and more particularly to
techniques for facilitating diagnosis of presenting conditions
based on internal images of a test subject, such as a living
patient.
BACKGROUND
[0002] Many medical diagnoses rely on non-invasive diagnostic tools
to provide information, often in the form of images, descriptive of
status of internal portions or organs of a patient. These tools
include thermal imaging, ultrasonic probes, magnetic resonance
imaging techniques, positron emission tomography, computed
tomography (CT), single photon emission-computed tomography
(SPECT), optical imaging and/or X-ray based techniques. In some
minimally invasive instances, imaging aids, such as
contrast-enhancing agents, are introduced into the subject or
patient to aid in increasing available data content from the
non-destructive imaging technique or techniques being employed.
[0003] Each of these tools presents advantages in particularized
situations, has technological limitations, may require set-up and
analysis time, can include risks and also has associated costs. As
a result, a cost-benefit analysis that also reflects the degree of
urgency with respect to a particular diagnostic trajectory often
favors usage of X-ray based measurement techniques.
[0004] However, exposure to X-rays can result in some risk to the
test subject or patient. For at least this reason, the dosage of
X-rays incident on the patient, organ or object being
evaluated/imaged, is often carefully chosen and controlled, for
example, variables such as current to the X-ray tube, peak voltage
applied to the X-ray tube (kVp) and exposure time, and by selecting
and defining an area to be exposed to provide successful imaging,
based on the task and the test subject or patient's parameters,
with least health risk to the patient or radiation exposure to the
object being imaged. The Food and Drug Administration has recently
identified X-rays as potentially having carcinogenic effects,
adding impetus to the desire to reduce overall exposure while still
providing imaging characteristics capable of enabling rapid,
effective and accurate diagnostic aids.
[0005] Several factors influence image quality resulting from an
X-ray procedure. Statistical photon noise resulting from
characteristics of the X-ray source and the X-ray generation
conditions tends to dominate other noise sources in formation of an
X-ray image. Contrast between various image portions, and contrast
enhancement techniques, are also important considerations in
providing diagnostic images, and these issues require increasingly
sophisticated treatment as dose is decreased.
[0006] One of the key tenets of medical X-ray imaging is that image
quality should be carefully considered in determining exposure
conditions, such as predetermined dose considerations delivered to
the test subject or patient. The design and operation of a detector
used for medical X-ray imaging should therefore be tailored,
responsive to the particularized task and measurement conditions,
including variables in test subject mass, opacity and the like, to
provide high image quality for each X-ray exposure that is incident
at its input. One very useful objective metric of quality for
electronically-represented images, per input exposure, is detective
quantum efficiency (DQE), which represents efficiency of transfer
of signal-to-noise ratio from the input signal (i.e., the exposure
employed) to detector output.
[0007] Pixelated X-ray detectors (detectors comprising a geometric
array of multiple detector elements, where each detector element
may be individually representative of at least a portion of a
picture element in the resultant image) are increasingly being
used, particularly for medical imaging. The resulting electrical
signals from pixelated detectors may be "read out" individually.
Examples of such usage include full resolution (one by one
binning), full field of view imaging, in which each detector
element in an array individually represents a pixel, and region of
interest imaging, in which a subset of the total ensemble of
detector elements may each correspond to a pixel, but not all
detector elements are employed.
[0008] Detector arrays may also be employed in modes in which the
signals from more than one individual detector element are
combined, prior to electrical conditioning of the resulting
electrical signals. Such combination is commonly called "binning"
of individual detector signals. In turn, digital or electronic
detectors of X-rays and subsequent signal processing of the signals
from such detectors increase flexibility in application and thus
help to promote reduction of dose of the illumination being
employed for non-destructive imaging, which is a desirable goal.
The problems addressed by this disclosure involve successfully
employing these capabilities to improve performance of a detector
array for a particular imaging task.
[0009] For the reasons stated above, and for other reasons
discussed below, which will become apparent to those skilled in the
art upon reading and understanding the present disclosure, there
are needs in the art to provide test data in support of reliable
diagnoses of medical conditions and diseases from medical
anatomical images, providing contrast equal to or exceeding that of
conventional approaches, yet using reduced exposure parameters when
feasible, consistent with the imaging task.
SUMMARY
[0010] The above-mentioned shortcomings, disadvantages and problems
are addressed herein, which will be understood by reading and
studying the following disclosure.
[0011] In one aspect, a process for variable binning of detector
pixels in a non-destructive imaging system is disclosed. The
process includes accepting input data indicative of image quality
goals and descriptors of an imaging task, as well as parameters
characterizing a test subject, relative to non-destructive imaging
of an internal portion of the test subject and determining when the
non-destructive imaging system is capable of achieving the image
quality goals using binning of more than four pixels.
[0012] In another aspect, a non-destructive imaging system includes
an illumination source configured to internally illuminate a test
subject and a detector array including a mosaic of detector
elements aligned with the illumination source opposite the test
subject. Each detector element corresponds to a pixel in a full
resolution, full field of view, imaging mode of the detector array.
The system also includes a controllable driver coupled to the
detector array. The controllable driver provides capability for
multiple detector array functionality settings including binning of
more than four pixels. The system also includes an interface
capable of accepting input data indicative of image quality goals
and facilitating selection of at least one of the multiple
functionality settings.
[0013] In a yet another aspect, an article of manufacture embodies
computer code thereon that includes computer-readable instructions,
which, when executed by one or more processors, causes the one or
more processors to perform acts of (i) accepting input data
indicative of image quality goals and information descriptive of a
test subject to be characterized using an X-ray system and (ii)
determining when the X-ray system is capable of achieving the image
quality goals via pooling of analog data derived from an extended
group of pixels.
[0014] Systems, clients, servers, processes, and computer-readable
media of varying scope are described herein. In addition to the
aspects and advantages described in this summary, further aspects
and advantages will become apparent by reference to the drawings
and by reading the detailed description that follows.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a simplified block diagram of an overview of a
system configured to improve X-ray imaging operations.
[0016] FIG. 2 is a simplified block diagram illustrating a
pixelated detector system that is useful in the context of the
system of FIG. 1.
[0017] FIG. 3 is a simplified block diagram illustrating a detector
element that is useful in the context of the pixelated detector
system of FIG. 2.
[0018] FIGS. 4 through 7 are graphs illustrating computed estimates
of detective quantum efficiency variation as a function of exposure
for different binning configurations and exposure conditions, which
graphs find utility in the context of the system of FIG. 1.
[0019] FIG. 8 shows a flowchart describing an imaging process that
finds utility in the system of FIG. 1.
[0020] FIG. 9 shows a flowchart describing a variable pixel binning
process that finds utility in the system of FIG. 1.
[0021] FIG. 10 is a block diagram of a hardware and operating
environment in which different embodiments can be practiced.
DETAILED DESCRIPTION
[0022] In the following detailed description, reference is made to
the accompanying drawings that form a part hereof, and in which are
shown, by way of illustration, specific embodiments which may be
practiced. These embodiments are described in sufficient detail to
enable those skilled in the art to practice the embodiments, and it
is to be understood that other embodiments may be utilized, and
that logical, mechanical, electrical and other changes may be made
without departing from the scope of the embodiments.
[0023] As used herein, the term "illumination" refers to exposure
to photons, electromagnetic radiation, phonons (e.g.,
insonification via ultrasound) or other wave phenomena, which do
not necessarily correspond to light that is visible to a human eye.
As employed herein, "an extended group of pixels" is defined to
describe five or more pixels whose output signals are pooled or
combined, for example, are added, to form a single picture element
or pixel, prior to or after conversion to binary data, but prior to
post-exposure processing and/or storage or display of resultant
diagnostic data including images derived from a source of such
pixels. Ranges of parameter values described herein are understood
to include all subranges falling therewithin. The following
detailed description is, therefore, not to be taken in a limiting
sense.
[0024] The detailed description is divided into five sections. In
the first section, a system level overview is described. In the
second section, modeling schemes for selecting among pixel binning
options in at least portions of one or more images are described.
In the third section, embodiments of processes are described. In
the fourth section, hardware and an operating environment in
conjunction with which embodiments may be practiced are described.
In the fifth section, a conclusion of the detailed description is
provided. A technical effect of the systems and processes disclosed
herein includes at least one of facilitating capability for
selective, real-time, adaptive variable binning of data from a
plurality of detector elements coupled together in a sensing array
to provide image quality adapted to the imaging task together with
reduced dose delivered to the test subject in non-destructive
imaging.
I. SYSTEM OVERVIEW
[0025] FIG. 1 is a simplified diagram of an overview of a system
100 configured to improve X-ray imaging operations. In particular,
the system 100 is configured to provide digitized images from
non-destructive imaging systems based on X-radiation, while
reducing the radiation dose delivered to the object or patient
being imaged, compared to conventional X-ray imaging systems and
processes. The system 100 includes a gantry 102 or other support
for an illumination source 104, such as an X-ray illumination
source, capable of providing illumination 106, such as X-rays or
other non-destructive internal imaging illumination, a test subject
support 108 that is transmissive with respect to the illumination
106 and that is positioned above a detector assembly 109, which may
include a scintillator 109', and which includes an image capture
device 110, opposed to the illumination source 104.
[0026] Components of the system 100 and a test subject 112 are
maintained in a defined geometric relationship to one another by
the gantry 102. A distance between the illumination source 104 and
the detector 110 may be varied, depending on the type of
examination sought, and the angle of the illumination 106
respective to the test subject 112 can be adjusted with respect to
the body to be imaged responsive to the nature of imaging
desired.
[0027] The test subject support 108 is configured to support and/or
cause controlled motion of the test subject 112, such as a living
human or animal patient, or other test subject 112 suitable for
non-destructive imaging, above the detector 110 so that
illumination 106' is incident thereon after passing through the
test subject 112. In turn, information from the detector 110
describes internal aspects of the test subject 112.
[0028] The detector assembly 109 may include a scintillator 109',
such as a conventional CsI scintillator 109', optically coupled to
an array of photodiodes (FIGS. 2 and 3, infra), such as a
two-dimensional array of photodiodes and suitable control
transistors formed using semiconductor material such as amorphous
silicon, or any other form of detector assembly 109 suitable for
use with the type or types of illumination 106 being employed, such
as X-rays. The detector elements are typically tesselated in a
mosaic. The scintillator 109' converts incident photons comprising
electromagnetic radiation, such as X-rays, from high-energy,
high-frequency photons 106', into lower-energy, lower-frequency
photons corresponding to spectral sensitivity of the detector
elements, in a fashion somewhat analogous to fluorescence, as is
commonly known in the context of many visible-light sources in use
today. Alternatively, the detector 110 may be formed as a
flat-panel array including a direct converter material such as
Cadmium Zinc Telluride (CdZnTe), Mercuric Iodide (Hgl.sub.2), Lead
Iodide (Pbl.sub.2), or amorphous Selenium (.alpha.-Se).
[0029] In some modes of operation, the gantry 102 rotates the X-ray
source 104 and detector 110 about an axis 116. The system 100 also
includes a control module 120, which may include a motor control
module 122 to control motors in the gantry 102 or to position the
X-ray illumination source 104 relative to the test subject 112
and/or the detector 110.
[0030] The controller 120 includes a detector controller 124
configured to control elements within the detector 110 and to
facilitate data transfer therefrom. The controller 120 also
includes a drive parameter controller 128 configured to control
electrical drive parameters delivered to the X-ray source 104. One
or more computers 130 provide connections to the controller 120 via
a bus 132 configured for receiving data descriptive of operating
conditions and configurations and for supplying appropriate control
signals, as will be described below in more detail with reference
to Section II et seq. The computer 130 also includes a bus 134, a
bus 136 and a bus 138. The bus 134 couples the computer 130 to an
operator console 140.
[0031] The operator console 140 includes one or more displays 142
and an input interface 144. The input interface 144 may include
user-selection tools, such as a keyboard, a mouse or other tactile
input device, capability for voice commands, connections to
automated computing equipment and/or other input devices. The one
or more displays 142 provide video, symbolic and/or audio
information relative to operation of system 100, user-selectable
options and images descriptive of the test subject 112, and may
include a graphical user interface for facilitating user selection
among various modes of operation and other system settings.
[0032] The system 100 also includes memory devices 150, coupled via
the bus 136 to the computer 130 through suitable interfaces. The
memory devices 150 include mass data storage capabilities 154 and
one or more removable data storage device ports 156. The one or
more removable data storage device ports 156 are adapted to
removably couple to portable data memories 158, which may include
optical, magnetic and/or semiconductor memories and may have read
and/or write capabilities, and which may be volatile or
non-volatile devices or may include a combination of the preceding
capabilities.
[0033] The system 100 further includes a data acquisition and
conditioning module 160 that has data inputs coupled to the
detector 110 and that is coupled by the bus 138 to the one or more
computers 130. The data acquisition and conditioning module 160
includes analog to digital conversion circuitry for capturing
analog data from the detector 110 and then converting those data
from the detector 110 into digital form, to be supplied to the one
or more computers 130 for ultimate display via at least one of the
displays 142 and for potential storage in the mass storage device
154 and/or data exchange with remote facilities (not illustrated in
FIG. 1). The acquired image data may be conditioned, as described
below with reference to Section II et seq., in either the data
acquisition and conditioning module 160 or the one or more
computers 130 or both.
[0034] FIG. 2 is a simplified block diagram illustrating a
pixelated detector system 200 that is useful in the context of the
system 100 of FIG. 1. The pixelated detector system 200 includes a
detector array 210 (e.g., part of the detector 110 of FIG. 1),
which in this example is assumed to be an N.times.M array, where N
and M represent integers describing a number of rows and columns in
the detector array 210. Typical detector arrays 210 include roughly
1,000 to 4,000 rows and columns. FIGS. 2 and 3 also employ "i",
"j", "n" and "m" to represent integers, where i varies over a range
{1, N}, and j varies over a range {1, M}.
[0035] The detector array 210 comprises a matrix or mosaic of
detector elements or pixel elements, i.e., detector element PDE
215(1, 1) through detector element PDE (n, m), each having a first
dimension 217 and a second dimension 219. The detector elements PDE
215 thus each have an area that is equal to a product a.times.b,
where the first dimension 217 is represented as "a" and the second
dimension 219 is represented as "b".
[0036] The detector elements PDE 215 are arranged along respective
rows and columns as illustrated. For example, a series of row
select lines 220(1) through 220(n) are each coupled to respective
ones of detector elements PDE 215(i, j), arranged along a
respective one of the row select lines 220, and a series of column
signal lines ranging from a first signal column line 230(1) through
a last signal column line 230(m) are each coupled to respective
ones of detector elements PDE 215. In the example of FIG. 2, a
suitable bias voltage V.sub.BIAS on bias line 240 is also coupled
to each of the detector elements PDE 215. Portions of the pixelated
detector system 200 of FIG. 2 and the processes discussed below in
section III may be implemented as software or hardware and may
comprise elements of the system 100 of FIG. 1 (supra) or the
computer system 1000 of FIG. 10 (infra).
[0037] FIG. 3 is a simplified block diagram 300 illustrating a
detector element PDE 215(i, j) that is useful in the context of the
pixelated detector system 200 of FIG. 2. Each detector element PDE
215 includes a computer-controllable switch 360, that may be formed
as a thin film amorphous silicon field effect transistor, and a
detector 365 such as a diode functioning as a photo diode. The
diodes 365 are fabricated to each include a relatively large
photosensitive surface area (a.times.b, FIG. 2), ensuring that the
diodes 365 are capable of intercepting a representative portion of
excitation 370, responsive to illumination 106' that has passed
through the test subject 112. Each diode 365 also includes
relatively large capacitance, facilitating storage of electrical
charge resulting from, and that is a function of, photonic
excitation 370.
[0038] A cathode of each of the diodes 365 in each column 230 of
the detector array 210 is connected by the source-drain conduction
path of the associated transistor 360 to a common column signal
line (230(1) through 230(m)) for the column. For example, the
diodes 365 in column 1 are coupled to the first column signal line
230(1). An anode of each of the diodes 365 in each row 220 is
connected to a common source of a negative bias voltage,
V.sub.BIAS, via the bias line 240. Respective gate electrodes of
the transistors 360 in each row 220 are connected to a common row
select line (220(1) through 220(n)), such as line 220(1) for row 1.
The row select lines 220 and the column signal lines 230 are
coupled to the detector controller 124 (FIG. 1) and the column
signal lines 230 also are connected to the data acquisition and
conditioning module 160.
[0039] In order to acquire an X ray image using the detector array
210, the system 100 may perform a variety of sequences. One
exemplary sequence is as follows. Initially, the detector
controller 124 pre-charges the detector elements 215, for example,
connects all the column signal lines 230(1) through 230(m) to
ground, and applies a positive voltage to all the row select lines
220(1) through 220(n). The positive voltage applied to the row
select lines 220 turns ON the transistor 360 in each detector
element PDE 215, placing a positive charge on the reverse biased
diodes 365. Once the diodes 365 have been fully charged, the
detector controller 124 applies a negative voltage, which is more
negative than the negative bias voltage V.sub.BIAS, to the row
select lines 220. This negative biasing of the row select lines 220
turns OFF the transistor 360 in each detector element PDE 215 and
stores a predetermined amount of charge in each of the diodes
365.
[0040] Then the detector 110 is exposed to a pulse of X-ray photons
106 produced in a conventional manner by the system illumination
source 104 to generate a beam of X-ray photons 106. After
traversing through the test subject 112, X-ray photons 106' are
detected, either directly or by conversion to lower energy photons
370 by the scintillator 109'. When photons 370 strike the diodes
365 in the detector elements PDE 215, the diodes 365 conduct
electricity and discharge a portion of their charge. The amount of
discharge in a given diode 365 depends upon the relative
illumination, which in turn depends upon the intensity of the X-ray
energy 106' transmitted through the test subject 112. Therefore,
the amount of discharge in the diode 365 in each detector element
PDE 215 is a function of intensity of the incident X-rays 106'
striking portions that are each optically coupled to a
corresponding region, e.g., pixel or detector element PDE 215 of
the X-ray detector array 210.
[0041] After termination of X-ray 106' exposure, residual charge in
each diode 365 is sensed. This is done through the column signal
lines which are attached to the data acquisition and conditioning
module 160. The module 160 contains sensing and conversion
circuitry to convert analog signals to digital or binary format to
facilitate additional signal processing and conditioning, data
display, data storage and/or data transmission.
[0042] Any of several types of sensing circuits can be incorporated
into the data acquisition and conditioning module 160. For example,
the sensing circuit can measure the voltage across the diode 365,
and therefore the amount of charge remaining on the diode 365.
Alternatively, the sensing circuit can connect the associated
column signal lines 230(1) through 230(m) to ground potential and
measure the amount of charge that is required to replace the charge
removed by exposure of the respective diode 365 to photons 370.
[0043] To provide maximum image resolution, the diode 365 charges
are individually sensed one row 220 at a time, via the detector
controller 124 sequentially applying positive voltage to each of
the row select lines 220. When a row select line 220 is positively
biased, the detector array transistors 360 connected to that row
select line 220 are turned ON, thereby coupling the associated
diodes 365 in the selected row to their column signal lines 230(1)
through 230(m) and thus to suitable signal combining and
analog-to-digital conversion circuitry. The acquisition of such
data is quantifiable in terms of objective characteristics that
also facilitate comparison of various detectors 110, exposure
parameters, metrics descriptive of resultant utility of information
for analysis/diagnostic/interpretive purposes and the like, as is
described below in more detail.
II. DETECTIVE QUANTUM EFFICIENCY MODEL OVERVIEW
[0044] In this section, a framework for a model descriptive of
Detective Quantum Efficiency, or DQE, is developed, in a series of
subsections (A) through (E). It will be appreciated that, while the
model development below is phrased in terms of conventions such as
Cartesian coordinates, other forms of description and other
coordinate systems may be employed, without significantly altering
the teachings of the present disclosure.
[0045] Aspects of modeling and characterizing performance of
detectors 110 are described in U.S. Pat. No. 6,663,281 B2, entitled
"X-ray detector monitoring", issued to R. Aufrichtig, P. Granfors,
G. Brunst and K. Kump, which is assigned to GE Medical Systems
Global Technology Company, LLC of Waukesha, Wis., and in an article
entitled "Performance Of A 41.times.41 cm.sup.2 Amorphous Silicon
Flat Panel X-ray Detector Designed For Angiographic And R&F
Imaging Applications", by P. Granfors, R. Aufrichtig, G. Possin, B.
Giambattista, Z. Huang, J. Liu and B. Ma (Med. Phys. 30(10),
October 2003, pp. 2715-2726). The model developed in this
disclosure is similar to the model given in the latter publication,
but is adapted for more generalized cases, viz., N'.times.N' or
N'.times.M' pixel binning, and variable pixel binning. The
information represented in the graphs shown in FIGS. 4 through 7
include estimates that are organized for ready application in
radiographic diagnosis, rather than from the perspective of
detector characterization.
II(A). Introduction to Detector Performance Criteria
[0046] DQE is a measure or metric descriptive of efficiency with
which a detector 110 or detector array 210 converts signals from
electromagnetic radiation 106' to electrical signals. As described
herein, DQE includes information that reflects comparison of a
signal-to-noise ratio from that of the electromagnetic signal,
e.g., 106' of FIG. 1, incident on respective photosensitive
detector elements PDE 215(i, j), to a signal-to-noise ratio
corresponding to electrical signals provided via the detector
outputs 230. DQE is an objective measurement often employed in
characterizing imaging performance of a detector 110 and in
comparing relative performance aspects of different detectors 110.
A general equation useful in the context of calculating DQE as a
function of frequency "f" is shown below with reference to Eq. (1):
DQE(f)=(.PHI.*(G(.PHI.)*MTF(f)).sup.2)/(NPS(f)), Eq. (1) where
.PHI. is a parameter describing fluence of electromagnetic or other
incident imaging waves 106' on detector 110, G(.PHI.) describes
detected signal per unit of fluence, that is, a slope describing
detector element PDE 215 response, MTF(f) represents a modulation
transfer function applicable to the system being modeled, and
NPS(f) illustrates frequency variation of an applicable noise power
spectrum. If the response of the detector 110 is linear and the
detector 110 produces a signal of zero when the X-ray fluence F is
zero, G(.PHI.) may be represented by S/.PHI., with S representing
output signal values from the detector 110. Representation of .PHI.
as C*X, with X representing air kerma (kinetic energy released per
unit mass in air), and with C representing fluence per air kerma,
allows Eq. (1) to be modified as shown below in Eq. (2):
DQE(f)=((S*MTF(f)).sup.2)/(NPS(f)*X*C). Eq. (2)
II(B). Binned Imaging Modes
[0047] A common pixelated medical imaging detector array 210
realization employs amorphous silicon as a semiconductive and
photoconductive material, as is described in more detail with
reference to FIG. 3. Detector arrays 210 so formed include an array
of detector elements PDE 215, connected to respective gate lines
220 and respective data lines 230, typically arranged according to
a Cartesian coordinate system, often with the gate lines 220
orthogonal to the data lines 230. When a gate line 220 is switched
to a suitable voltage to read out data from the detector elements
PDE 215 via respective data lines 230, signals from all of the
detector elements PDE 215 on that gate line 220 are sensed by
suitable circuitry coupled to each of the data lines 230. Binned
modes of operation are facilitated by control circuitry, for
example in the detector controller 124 of FIG. 1, which may be
physically contained with the detector 110, that permit combining
signals from multiple neighboring detector elements PDE 215 to
provide a larger pixel. This is achieved by reading out multiple
gate lines 220 simultaneously and summing data signals from
multiple data lines 230. When a number N' of the gate lines 220,
and a number M' of the data lines 230 are coordinated in this
fashion, this is called binning of N' by M' pixels. When N'=M'=1,
the detector array 210 is read out at full resolution.
[0048] In some applications, less than all of the detector elements
PDE 215 in the detector array 210 are involved in providing data
employed to derive an image. For example, in some applications, a
central portion of the detector array 210 is selectively employed
to provide high-resolution imaging of particularized conditions.
Angiography and fluoroscopy exemplify applications where a subset
of the detector elements PDE 215 in the detector array 210 may be
used to form an image while other detector elements are not used to
make the image In one embodiment, a detector array 210 may include
2048.times.2048 detector elements PDE 215, but, in some situations,
only employ 1024.times.1024 detector elements PDE 215 within a
larger array, such as a central group of those detector elements
PDE 215, responsive to machine-executable instructions and as
appropriate to the imaging procedure being initiated. As a result,
increased flexibility of operation coupled with reduced mechanical
complexity may be realized.
II(C). Computing DQE in Binned Modes
[0049] The MTF(f) function may be usefully treated as a product of
at least two components, with one of these components representing
a scintillator portion (descriptive of the MTF of the light
incident to the detector array 210) and another of these components
representing an aperture component, A(x, y), providing information
demonstrative of the sensitivity of the detector array 210. The
aperture component A(x, y) may be approximated as shown below in
Eq. (3), with reference to a Cartesian coordinate system employing
axes X and Y: A(x,y)=X(x)*Y(y). Eq. (3)
[0050] The scintillator component and the aperture component A(x,
y) collectively describe aspects of the responsivity of the
detector 110. Of these two representative components, only the
aperture component of the MTF changes significantly when the
detector array 210 readout is modified from full-resolution mode
(i.e., measuring output signals from each detector element
individually) to binned modes, where an integer number, represented
as N'.times.M', of such detector element output signals, such as
two or more, are combined in formation of a non-destructively
derived imaging representation.
[0051] As an example, an aperture for N'.times.M' binned mode of
operation of the detector array 210 may be usefully modeled as an
aperture of a full-resolution imaging mode, replicated N'.times.M'
times. Employing the approximation of Eq. (3) permits description
of detector performance vs. binning as described below.
[0052] In at least this context, and utilizing applicable Fourier
techniques (as described, for example, in (Med. Phys. 30(10),
October 2003, pp. 2715-2726 at p. 2719), a modulation transfer
function applicable to binned modes of operation of a detector
array 210, wherein the binning has N' detector elements PDE 215
along one axis and M' detector elements PDE 215 along another axis,
may be computed from the MTF in full resolution mode as shown below
with reference to Eq. (4):
MTF(u,v).sub.N'.times.M'=((sin(.pi.puN')*(sin((.pi.pvM))*(MTF.sub.1.times-
.1(u,v))/(N'*sin(.pi.pu)*M'*sin(.pi.pv)), Eq. (4) where "p"
describes pixel pitch within the detector array 210 and "u" and "v"
represent Cartesian coordinates in frequency space.
[0053] The dependence of NPS(f) on imaging mode is somewhat more
complex to model mathematically, owing to effects due to aliasing,
which, in turn, are responsive to spatial sampling, among other
things, and particularly with respect to the Nyquist theorem, as is
well-known to those of skill in the relevant arts. Absent
electronic noise, NPS(f) also includes scintillator and aperture
effects, each including noise aliased from frequencies above the
Nyquist frequency. As a result, even though the scintillator
component does not change, the scintillator component of NPS(f)
differs significantly between modes of detector sampling, at least
in part because of differences in aliasing effects.
[0054] In a fashion analogous to that described above with respect
to transformation of the MTF(f) function (Eq. (4)), a
"pre-sampling" NPS(f) representation is usefully modeled as a
product of aperture and scintillator components. As a practical
matter, measured NPS(f) values are well approximated by summing
such "pre-sampling" NPS(f) over applicable aliases. Simplifying the
aperture component A(x, y) of the MTF(f) via employment of
separable products of sinc functions (i.e., sin(x)/x), the NPS(f)
function, in full-resolution and binned modes, may be written as:
NPS 1 .times. 1 = m , n = - .infin. .infin. .times. { [ sin
.function. ( .pi. .times. .times. a .function. ( u + m / p ) ) .pi.
.times. .times. a .function. ( u + m / p ) ] 2 .function. [ sin
.function. ( .pi. .times. .times. b .function. ( v + n / p ) ) .pi.
.times. .times. b .function. ( v + n / p ) ] 2 F .function. ( u + m
/ p , v + n / p ) } , .times. .times. and Eq . .times. ( 5 ) NPS N
' .times. M ' = m , n = - .infin. .infin. .times. [ sin ( .pi.
.times. .times. p .times. .times. N ' .function. ( u + n / ( N '
.times. p ) ) N ' .times. sin .function. ( .pi. .times. .times. p
.function. ( u + n .times. .times. l / ( N ' .times. p ) ) ) * sin
.times. ( .pi. .times. .times. p .times. .times. M ' .function. ( v
+ m / ( .times. M ' .times. .times. p ) ) ) .times. M ' .times.
.times. sin .times. ( .pi. .times. .times. p .function. ( v + m
.times. .times. l / ( .times. M ' .times. .times. p ) ) ) ] 2 * [
sin .function. ( .pi. .times. .times. a .function. ( u + n / ( N '
.times. p ) ) ) .pi. .times. .times. a .function. ( u + n / ( N '
.times. p ) ) ] 2 * [ sin .function. ( .pi. .times. .times. b
.function. ( v + m / ( M ' .times. p ) ) ) .pi. .times. .times. b
.function. ( v + m / ( M ' .times. p ) ) ] 2 * F .function. ( u + n
/ ( N ' .times. p ) , v + m / ( M ' .times. p ) ) . Eq . .times. (
6 ) ##EQU1##
[0055] Here "a" and "b" represent dimensions of the photosensitive
elements PDE 215, as illustrated in FIG. 2, "m" and "n" represent
integer variables, and F represents a function descriptive of the
scintillator portion of the "pre-sampling" NPS. F, in turn, may be
parameterized as a generalized two-dimensional Lorentzian function,
an example of which is shown in Eq. (7) below:
F(u,v)=.gamma./[(1+.alpha.(u.sup.2+v.sup.2)].sup..beta., Eq. (7)
where the parameter .gamma. represents NPS(f), evaluated at zero
frequency. Substituting Eq. (7) into Eq. (5) and varying values of
".alpha." and ".beta." in order to fit measured values obtained for
NPS(f), where the measured values are obtained in the
full-resolution mode, allows detector 110 performance to be
modeled. When the .alpha. and .beta. values that are found to fit
the measured NPS properties are substituted into Eq. (7), the
result may be employed to predict NPS functions corresponding to
operation of the detector 110 in various binned modes. Combining
Eqs. (4) through (7) allows prediction of DQE(f) applicable to
various binned modes of operation, from data measured in
full-resolution mode.
II(D). Computing DQE(f) Versus Exposure (Dose) for Binned Modes
[0056] Expected DQE(f) at lower exposures can be predicted from the
measured high exposure DQE(f) by decomposing the NPS into a
frequency-dependent quantum noise component, NPS(f,
X)=X*NPS.sub.qX(f), that is proportional to exposure, and a system
component, NPS.sub.0, that is independent of frequency and
exposure. A representation resulting from such treatment is given
below in Eq. (8): NPS(f,X)=X*NPS.sub.qX(f)+NPS.sub.0. Eq. (8)
[0057] The expression shown in Eq. (8) may be substituted into that
shown in Eq. (2). A result of such substitution is shown below in
Eq. (9):
DQE(f,X)=S.sup.2*MTF.sup.2/[C*X.sup.2(NPS.sub.qX+NPS.sub.0/X)]. Eq.
(9)
[0058] At high exposures, NPS.sub.0/X is negligible in comparison
to NPS.sub.qX. As a result, Eq. (9) may be simplified to provide
the expression shown below in Eq. (10): DQE .function. ( f , X ) =
.times. DQE high .times. .times. X .function. ( f ) / [ 1 + NPS 0 /
( X * NPS qX .function. ( f ) ) ] = .times. DQE high .times.
.times. X .function. ( f ) * .times. [ X * NPS qX .times. ( f ) / (
NPS 0 + ( X * NPS qX .times. ( f ) ) ) ] , Eq . .times. ( 10 )
##EQU2## where DQE.sub.highX(f) represents the DQE in the high
exposure limit. Eq. (10) shows that the DQE at exposures below the
high exposure extreme DQE.sub.highX(f) decreases from that high
exposure limit by a factor equal to a ratio of quantum noise to
total noise.
[0059] System noise is described by NPS.sub.0 and may be further
decomposed into a noise contribution, NPS.sub.pixel, arising from
each pixel or detector element PDE 215 in the detector array 210,
and noise arising from data-line and digitization sources,
represented as NPS.sub.line. Substitution of these expressions into
Eq. (10) allows that to be expressed as shown below in Eq. (11):
NPS.sub.0,N'.times.M'=N'*M'*NPS.sub.pixel+M*NPS.sub.line. Eq.
(11)
[0060] The data acquisition and conditioning module 160 of FIG. 1
determines appropriate binning of signals from the detector
elements PDE 215 and the system 100 is capable of configuring the
detector array 210 to operate in that binning mode via suitable
control signals. For a DQE.sub.highX(f) corresponding to given
detector 110, desirable binning parameters at relatively low
exposure can be determined by treating DQE(f, X) appropriately,
where the detector entrance exposure, X, is directly proportional
to the average image signal that has been acquired, for example via
the data acquisition circuitry 160 of FIG. 1. The average may be
computed in a statically robust way, e.g., by computing median or
threshold values, and/or by excluding anomalous results, or
"outliers" (such as anomalously high or low values), prior to
computing the average. The calculated average is then converted
into an entrance exposure by accounting for a selected detector
gain setting.
II(E). DQE Estimates for Different Binning Modes
[0061] FIGS. 4 through 7 are graphs illustrating detective quantum
efficiency variation as a function of exposure for different
binning configurations and exposure conditions that are useful in
the context of the system of FIG. 1. Other estimates may be derived
by employing the theoretical outlines developed in the preceding
subsections. FIGS. 4 through 7 show computed DQE as a function of
exposure at the detector 110, spatial frequency, and amount of
binning, for selected examples. The concepts described in this
disclosure use this type of information to choose an appropriate
amount of binning for the imaging task. This choice may be made by
the operator or by the system 100, and may be either static or
dynamic, i.e., adapted during the imaging as, for example, during a
fluoroscopic imaging sequence.
[0062] FIGS. 4 through 7 depict graphs 400 through 700,
respectively, each having an abscissa calibrated to represent dose
(in microRoentgens or .mu.R) as an independent variable and an
ordinate calibrated to represent DQE as a dependent variable. Each
of FIGS. 4 through 7 provides five examples, correspond
respectively to 1.times.1, 2.times.2, 3.times.3, 4.times.4 and
5.times.5 binning of signal data from the detector array 210, with
each trace having a parenthetical suffix corresponding to the
binning mode being modeled, as noted in the tabular entries
presented with each graph.
[0063] FIG. 4 represents five examples 480(1), 480(2), 480(3),
480(4) and 480(5), for exposure conditions corresponding to a
spatial frequency of zero cycles per millimeter. FIG. 5 represents
five examples 580(1), 580(2), 580(3), 580(4) and 580(5), for
exposure conditions corresponding to a spatial frequency of
one-tenth cycle per millimeter. FIG. 6 represents five examples
680(1), 680(2), 680(3), 680(4) and 680(5), for exposure conditions
corresponding to a spatial frequency of two-tenths cycle per
millimeter. FIG. 7 represents five examples 780(1), 780(2), 780(3),
780(4) and 780(5), for exposure conditions corresponding to a
spatial frequency of three-tenths cycle per millimeter. The models
described above may be usefully employed, together with empirical
data and the examples of FIGS. 4 though 7, to provide estimates
useful in balancing dose, spatial frequency response, DQE and other
variables in selecting one or more candidate binning modes and
corresponding exposure parameters useful for a particular imaging
task and test subject 112. Interpolation may be employed for
estimation of other scenarios, and the models described herein, as
well as historical data, may also be used in arriving at a set of
candidate modes for imaging consideration.
[0064] One or more desirable levels of binning can be determined,
for example via a look-up table that represents the information of
the graphs shown in FIGS. 4 through 7, where the look-up table is
contained in the memory systems 150 of the computer 130 of FIG. 1,
for example. Comparison of the several cases for which estimates
are provided in FIGS. 4 through 7 illustrates this process. For
example, using 0 cy/mm together with a calculated entrance exposure
of 0.5 .mu.R, a 4.times.4 binning may be preferred, with negligible
added benefit resulting from 5.times.5 binning. The system 100 of
FIG. 1 can also be set for a slightly higher spatial frequency,
e.g. at 0.3 cy/mm, where binning in a 3.times.3 binning mode
provides useful imaging properties.
[0065] Benefits obtained via DQE considerations coupled with
binning, together with careful binning selection, are particularly
important at low exposures. In dose-starved situations, there is
very little high spatial frequency content in resulting image data,
and low spatial frequency content is correspondingly significant in
forming an image having useful diagnostic properties. The benefits
of combining signals from multiple detector elements PDE 215 or
pixels often provides larger increases in resultant image quality,
compared to non-binning approaches or in some very simple binning
cases (such as 2.times.2 binning). The benefits of variable
multi-element signal binning accrue in exactly this imaging
situation, viz., one of low exposure and where low spatial
frequency imaging data are significant in diagnosis, for
example.
[0066] Process embodiments of these strategies for providing
diagnostically-useful images together with benefits associated with
variable binning of detector data are described below in more
detail with reference to FIGS. 8 and 9.
III. PROCESS EMBODIMENTS
[0067] In the previous section, an overview of models and
techniques for variable binning of detector data in medical imaging
was described. In this section, the models of that section are used
in describing the operation of a series of embodiments, with the
particular processes of such embodiments being described by
reference to relevant flowcharts. Describing the processes by
reference to one or more flowcharts enables one skilled in the art
to develop programs, firmware, or hardware, including such
instructions to effectuate the processes through one or more
processors responsive to computer-readable instructions embodied on
computer-readable media.
[0068] These capacities are often accomplished using suitable
computers, including one or more processors, by executing the
instructions embodied in articles of manufacture such as
computer-readable media, or as modulated signals embodied in a
carrier wave. As a result, the computer-readable instructions may
include capacity for accepting revised computer-readable
information descriptive of revised capabilities, which may relate
to revisions of aspects of the system 100 via substitution of
components, revisions of data-processing structures and the like.
Similarly, processes performed by server computer programs,
firmware, or hardware also are represented by computer-executable
instructions. The processes of the present disclosure are performed
by one or more program modules executing on, or performed by,
firmware or hardware that is a part of a computer (e.g., computer
130, FIG. 1).
[0069] In some embodiments, processes disclosed herein are
implemented as a computer data signal embodied in a carrier wave,
that represents a sequence of instructions which, when executed by
one or more processors, such as a processor contained in or
associated with the computer 130 in FIG. 1, causes the respective
process to occur. In other embodiments, the processes disclosed
herein are implemented as a computer-accessible medium having
executable instructions capable of directing a processor, such as a
processor contained in or associated with the computer 130 in FIG.
1, to perform the respective process. In varying embodiments, the
medium is a magnetic medium, an electronic medium, or an
electromagnetic/optical medium.
[0070] More specifically, in a computer-readable program
embodiment, programs can be structured in an object-orientation
using an object-oriented language such as Java, Smalltalk or C++,
and the programs can be structured in a procedural-orientation
using a procedural language such as COBOL or C. Software components
may communicate in any of a number of ways that are well-known to
those skilled in the art, such as application program interfaces
(API) or interprocess communication techniques such as remote
procedure call (RPC), common object request broker architecture
(CORBA), Component Object Model (COM), Distributed Component Object
Model (DCOM), Distributed System Object Model (DSOM) and Remote
Method Invocation (RMI). The components execute on as few as one
computer as in computer 130 in FIG. 1, or on multiple
computers.
[0071] FIG. 8 shows a flowchart describing an imaging process 800
for determining estimated image quality versus binning at a
specified dose that finds utility in the system 100 of FIG. 1. The
process 800 begins in a block 805.
[0072] In a block 810, the process 800 accepts input data
descriptive of a type of imaging task to be performed, for example,
angiographic study, examination of hard tissue (such as bone),
pulmonary organ study, fluoroscopy or other non-destructive imaging
or diagnostic characterization, and also incorporating data
descriptive of the test subject 112 under study, such as thickness,
weight, and other variables relevant to the imaging process. Input
data such as dose and voltage may also be provided. Control then
passes to a query task 815.
[0073] In query task 815, the input data and information
descriptive of capabilities of the system 100 are incorporated to
provide one or more suggested exposure regimes likely to be
consistent with noise and signal parameters desired, the type of
imaging sought, the kinds of diagnostic criteria to be extracted
from resultant data and the like. Among other things, the query
task 815 includes determination of when binning of larger numbers
of pixels, that is, binning of pixels in groups larger than
2.times.2, or an extended group of pixels, may result in benefits,
such as reduction of dose, coupled with appropriate resolution and
contrast.
[0074] When the query task 815 determines that binning of larger
numbers of pixels may provide desirable characteristics consistent
with capabilities of the system 100 and conditions relevant to the
test subject 112 as well as the type of characterization being
contemplated, control passes to a block 820. In the block 820, a
process 900 is invoked, as described below with reference to FIG.
9.
[0075] When the query task 815 determines that conventional
exposure and data collection procedures are appropriate for the
imaging and diagnostic desires being undertaken, control passes to
a block 825. In the block 825, the process 800 terminates and
imaging proceeds in a conventional manner.
[0076] FIG. 9 shows a flowchart describing a variable pixel binning
process 900 that finds utility in the system 100 of FIG. 1. The
process 900 begins in a block 905.
[0077] In a block 910, the process 900 employs settings specified
for the type of imaging procedure presently relevant, as well as
information descriptive of the test subject 112 (e.g., as noted
with respect to the block 810 supra), together with a range of
capabilities of the system 100 being employed, in contemplation of
a set of appropriate exposure and data collection regimes. Control
then passes to a block 915.
[0078] In the block 915, signal conditions relative to the detector
110, data collection and processing regimes, and exposure
conditions are collected. In one embodiment, signal conditions may
be derived from historical data, look-up tables and the like, for
substantially similar tasks and conditions. In one embodiment,
signal conditions may include one or more frames of imaging signal
information responsive to an exposure of X-rays 106' that have
passed through the test subject 112. Control then passes to a block
920.
[0079] In the block 920, the process 900 analyzes the ensemble of
factors specific to the present imaging task against the backdrop
of information descriptive of signal conditions. In part, the block
920 sorts the information to select and rank order data relevant to
the type of imaging and test subject 112 of present interest.
Control then passes to a query task 925.
[0080] In the query task 925, the process 900 determines when
signal quality (such as DQE), coupled with dose considerations
relative to the test subject 112, may offer benefits via binning of
larger numbers of pixels, in contrast to conventional imaging
methodologies. When the query task 925 determines that benefits may
be obtained via the techniques described in this disclosure,
control passes to a block 930. When the query task 925 determines
that benefits are unlikely to be obtained via the techniques
described in this disclosure, control passes to a block 935.
[0081] In the block 930, the process 900 determines revised
parameters for configuration of the system 100. The determination
of the block 930 may include one or more binning regimes likely to
prove useful, one or more exposure settings associated with each of
the binning regimes, and the like.
[0082] For example, a feedback loop may be incorporated that
changes the voltage and current to the illumination source or x-ray
tube 104, and the feedback loop may switch filters in and out of
the beam 106, 106', to present a high quality image to the
clinician, together with reduced dose to the test subject 112. The
feedback loop is automatically implemented by the system 100, based
on analysis of the image and other factors. When the image can be
improved by changing the binning mode, or when the image quality
may be maintained but require a reduced dose via modification of
the binning mode, the system 100 alters the exposure and data
collection parameters automatically. The clinician is always
presented with the best image that the system 100 is capable of, at
the lowest dose to the test subject 112. Control then passes to the
block 935.
[0083] In the block 935, data relative to the exposure and data
collection methodologies described above are made available to a
system operator. For example, the display 142 may provide
information descriptive of one or more exposure and data collection
regimes to the operator. As another example, the operator may
over-ride that regime or regimes offered by the processes 800 and
900 via entry of suitable commands, such as commands selected using
the input media 144. The data associated with the block 935
facilitate rank-ordering of exposure and data-collection options
that are consistent with the system 100, the test subject 112, and
other relevant factors. Affirmative selection of an exposure regime
may be sought from the operator prior to exposure of a test subject
112 that is a living being, in the block 935, however, selection of
an exposure regime may also be effectuated automatically. Control
then passes to a block 940.
[0084] In the block 940, the system 100 is configured to operate in
conformance with selected criteria. Control then passes to a block
945, ending the process 900 and initiating operation of the imaging
system 100 as determined via processes 800 and 900, among other
things. The processes 800 and 900 may be implemented as hardware or
software or a combination thereof, and may be updated via addition
or substitution of machine-readable and executable instructions, as
is described below in more detail with reference to FIG. 10.
IV. HARDWARE AND OPERATING ENVIRONMENT
[0085] FIG. 10 is a block diagram of a hardware and operating
environment 1000, including one or more computers 1002, in which
different embodiments can be practiced. The description of FIG. 10
provides an overview of computer hardware and a suitable computing
environment in conjunction with which some embodiments can be
implemented. Embodiments are described in terms of a computer
executing computer-executable instructions. However, some
embodiments can be implemented entirely in computer hardware in
which the computer-executable instructions are implemented in
read-only memory. Some embodiments can also be implemented in
client/server computing environments where remote devices that
perform tasks are linked through a communications network. Program
modules can be located in both local and remote memory storage
devices in a distributed computing environment.
[0086] The computer 1002 includes one or more processors 1004,
commercially available from Intel, Motorola, Cyrix and others. The
computer 1002 also includes random-access memory (RAM) 1006,
read-only memory (ROM) 1008, and one or more mass storage devices
1010, and a system bus 1012, that operatively couples various
system components to the processing unit 1004 and/or to each other
and/or external apparatus. The memories 1006 and 1008, and the mass
storage devices 1010, are types of computer-accessible media. Mass
storage devices 1010 are more specifically types of nonvolatile
computer-accessible media and can include one or more hard disk
drives, floppy disk drives, optical disk drives, and tape cartridge
drives. The processor 1004 executes computer programs stored on
these various computer-accessible media.
[0087] The computer 1002 can be communicatively connected to the
Internet 1014 via a communication device 1016. Internet 1014
connectivity is well known within the art. In one embodiment, a
communication device 1016 is a modem that responds to communication
drivers to connect to the Internet via what is known in the art as
a "dial-up connection." In another embodiment, the communication
device 1016 includes an Ethernet.RTM. or similar hardware network
card connected to a local-area network (LAN) that itself is
connected to the Internet 1014 via what is known in the art as a
"direct connection" (e.g., T1 line, etc.).
[0088] A user may enter commands and information into the computer
1002 through input devices such as a keyboard 1018 or a pointing
device 1020. The keyboard 1018 permits entry of textual information
into computer 1002, as known within the art, and embodiments are
not limited to any particular type of keyboard 1018. The pointing
device 1020 permits the control of the screen pointer provided by a
graphical user interface (GUI) of operating systems such as
versions of the Microsoft Windows.RTM. operating system.
Embodiments are not limited to any particular pointing or tactile
input device 1020. Such pointing devices 1020 include mice, touch
pads, trackballs, remote controls and point sticks. Other input
devices (not shown) can include a microphone, joystick, game pad,
satellite dish, scanner, or the like.
[0089] In some embodiments, the computer 1002 is operatively
coupled to a display device 1022 via the system bus 1012. The
display device 1022 permits the display of information, including
computer, video and other information, for viewing by a user of the
computer 1002. Embodiments are not limited to any particular
display device 1022, which may include cathode ray tube (CRT)
displays (monitors), as well as flat panel displays such as liquid
crystal displays (LCD's). In addition to a monitor 1022, computers
1002 typically include other peripheral input/output devices such
as printers (not shown). Speakers 1024 and 1026 may provide audio
output signals, responsive to commands delivered through the system
bus 1012.
[0090] The computer 1002 also includes an operating system (not
shown) that is stored on the computer-accessible media RAM 1006,
ROM 1008, and mass storage device 1010, that is accessed and
executed by the processor 1004. Examples of operating systems
include the Microsoft Windows.RTM., Apple MacOS.RTM., Linux.RTM.
and UNIX.RTM. operating systems. Examples are not limited to any
particular operating system, however, and the construction and use
of such operating systems are well known within the art.
[0091] Embodiments of the computer 1002 are not limited to any type
of computer 1002. In varying embodiments, the computer 1002
comprises a PC-compatible computer, a MacOS.RTM. operating system
compatible computer, a Linux.RTM. operating system compatible
computer, or a UNIX.RTM. operating system compatible computer. The
construction and operation of such computers are well known within
the art.
[0092] The computer 1002 can be operated using at least one
operating system to provide a graphical user interface (GUI)
including a user-controllable pointer. The computer 1002 can have
at least one web browser application program executing within at
least one operating system, to permit the computer 1002 to access
an intranet, extranet or Internet 1014 world-wide-web pages as
addressed by Universal Resource Locator (URL) addresses. Examples
include the Netscape Navigator.RTM. and the Microsoft Internet
Explorer.RTM. browser programs.
[0093] The computer 1002 can operate in a networked environment
using logical connections to one or more remote computers, such as
a remote computer 1028. These logical connections are achieved by a
communication device coupled to, or forming a part of, the computer
1002. Embodiments are not limited to a particular type of
communications device. The remote computer 1028 can be another
computer, a server, a router, a network PC, a client, a peer device
or other common network node. The logical connections depicted in
FIG. 10 include a local-area network (LAN) 1030 and a wide-area
network (WAN) 1032. Such networking environments are commonplace in
offices, enterprise-wide computer networks, intranets, extranets
and the Internet 1014.
[0094] When used in a LAN-networking environment, the computer 1002
and remote computer 1028 are connected to the local network 1030
through network interfaces or adapters 1034, which is one type of
communications device 1016. The remote computer 1028 also includes
a network device 1036. When used in a conventional WAN-networking
environment, the computer 1002 and remote computer 1028 communicate
with a WAN 1032 through one or more modems (not shown). The modem,
which can be internal or external, is connected to the system bus
1012. In a networked environment, program modules depicted relative
to the computer 1002, or portions thereof, can be stored in the
remote computer 1028.
[0095] The computer 1002 also includes a power supply 1038. Each
power supply 1038 can be a battery. The computer 1002 also may
include a removable memory storage port 1056 capable of accepting a
removable data storage device 1058 (analogous to the port 156 and
removable data storage device 158 of FIG. 1), which provides
capability for revision of machine-readable instructions, among
other things. Computer-readable instructions and/or data may also
be supplied to the computer 1020 via coupling to a
suitably-programmed removable data storage device 1058 and/or via a
carrier wave including modulation of computer-readable information
coupled from external sources, such as the Internet 1014 or other
external interconnections.
[0096] The computer 1002 may function as one or more of the control
segments of module 120 (FIG. 1), the computer 130, the operator
console 140 and/or the data acquisition and conditioning module
160, for example, via implementation of the processes 300, 400, 500
and 600 of FIGS. 3 through 6 as computer program modules.
V. CONCLUSION
[0097] A computer-based medical imaging system is described.
Although specific embodiments have been illustrated and described
herein, it will be appreciated by those of ordinary skill in the
art that any arrangement which is calculated to achieve the same
purpose may be substituted for the specific embodiments shown. This
disclosure is intended to cover any adaptations or variations. For
example, although described in procedural terms, one of ordinary
skill in the art will appreciate that implementations can be made
in a procedural design environment or any other design environment
that provides the required relationships.
[0098] In particular, one of skill in the art will readily
appreciate that the names or labels of the processes and apparatus
are not intended to limit embodiments. Furthermore, additional
processes and apparatus can be added to the components, functions
can be rearranged among the components, and new components to
correspond to future enhancements and physical devices used in
embodiments can be introduced without departing from the scope of
embodiments. One of skill in the art will readily recognize that
embodiments are applicable to future communication devices,
different file systems, and new data types. The terminology used in
this disclosure is meant to include all object-oriented, database
and communication environments and alternate technologies which
provide the same functionality as described herein.
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