U.S. patent application number 09/199953 was filed with the patent office on 2001-10-18 for x-ray tube life prediction method and apparatus.
Invention is credited to BEREZOWITZ, WILLIAM A., BREUNISSEN, JOHN R., MIESBAUER, DIANE M..
Application Number | 20010031036 09/199953 |
Document ID | / |
Family ID | 22739698 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010031036 |
Kind Code |
A1 |
BEREZOWITZ, WILLIAM A. ; et
al. |
October 18, 2001 |
X-RAY TUBE LIFE PREDICTION METHOD AND APPARATUS
Abstract
Possible failure of x-ray tubes is predicted by monitoring and
analysis of operating parameters considered leading indicators of
failure. Historical data for a tube population is analyzed by
discriminant analysis to develop a failure prediction algorithm.
The algorithm is used to correlate operating parameters, or values
derived from the operating parameters with a potential for tube
failure. The operating parameters may include anode overcurrent
events and spits, or spit rate exceeded errors for a diagnostic
system in which the x-ray tube is installed.
Inventors: |
BEREZOWITZ, WILLIAM A.;
(GREENFIELD, WI) ; BREUNISSEN, JOHN R.;
(WAUWATOSA, WI) ; MIESBAUER, DIANE M.;
(BROOKFIELD, WI) |
Correspondence
Address: |
PATRICK S YODER
7915 FM 1960 WEST SUITE 330
HOUSTON
TX
77070
|
Family ID: |
22739698 |
Appl. No.: |
09/199953 |
Filed: |
November 25, 1998 |
Current U.S.
Class: |
378/118 ;
378/117 |
Current CPC
Class: |
H05G 1/26 20130101; H05G
1/54 20130101 |
Class at
Publication: |
378/118 ;
378/117 |
International
Class: |
H05G 001/54 |
Claims
1. A method for predicting failure of an x-ray tube, the method
comprising the steps of: monitoring a plurality of operating
parameters of the x-ray tube; deriving a failure prediction value
from the plurality of monitored parameters; comparing the failure
prediction value to a desired reference value; and generating a
signal indicative of predicted tube failure based upon the
comparison.
2. The method of claim 1, wherein the desired reference value is
derived from monitored operating parameters of the x-ray tube.
3. The method of claim 1, wherein x-ray tube is included in a
medical diagnostic system, and the plurality of parameters are
monitored from a monitoring system remote from the system.
4. The method of claim 3, wherein the plurality of parameters are
monitored by transmitting signals representative of the parameters
over a computer network.
5. The method of claim 3, wherein the plurality of parameters are
monitored by periodic data sweeps between a remote monitoring
system and the system.
6. The method of claim 5, wherein the data sweeps are initiated by
the remote monitoring system.
7. The method of claim 1, wherein the plurality of parameters
includes a parameter indicative of anode overcurrent events for the
x-ray tube.
8. The method of claim 7, wherein the plurality of parameters
includes a parameter derived from spit events for the x-ray
tube.
9. The method of claim 8, wherein the parameter derived from spit
events is based upon a z-score for the x-ray tube.
10. The method of claim 1, wherein the failure prediction parameter
is derived from the plurality of parameters based upon discriminant
analysis of potential failure-related parameters for a population
of x-ray tubes.
11. A method for predicting potential failure of an x-ray tube in a
medical diagnostic system, the method comprising the steps of:
monitoring parameters indicative of presence in the x-ray tube of
particulate matter; deriving a predictive value from the
parameters; generating a signal indicative of potential failure of
the x-ray tube based on the predictive value.
12. The method of claim 11, wherein the parameters include a first
parameter based upon occurrence of anode overcurrent events and a
second parameter based upon occurrence of spit events.
13. The method of claim 12, wherein the second parameter is based
upon occurrence of spit rate exceeded errors in the system.
14. The method of claim 11, wherein the parameters are monitored
from a location remote from the diagnostic system.
15. A method for predicting potential failure of x-ray tubes, the
method comprising the steps of: monitoring operating parameters for
a population of x-ray tubes; performing statistical analysis of the
monitored parameters; and generating a failure prediction algorithm
based upon the statistical analysis.
16. The method of claim 15, wherein the failure prediction
algorithm is generated by discriminant analysis of the monitored
parameters.
17. The method of claim 15, comprising the further steps of:
monitoring operating parameters of at least one x-ray tube; and
predicting failure of the at least one x-ray tube based upon the
monitored parameters and the failure prediction algorithm.
18. The method of claim 15, wherein the monitored parameters
include a first value based upon occurrence of anode overcurrent
events and a second value based upon occurrence of spits.
19. The method of claim 18, wherein the second value is based upon
occurrence of spit rate exceeded errors for the at least one x-ray
tube.
20. A system for predicting possible failure of an x-ray tube, the
system comprising: a monitoring circuit coupled to the x-ray tube,
the monitoring circuit monitoring operating parameters of the x-ray
tube indicative of possible failure; and a failure prediction
circuit coupled to the monitoring circuit, the failure prediction
circuit executing a failure prediction routine based upon the
monitored operating parameters and generating a failure prediction
signal based upon the routine.
21. The system of claim 20, wherein the x-ray tube is included in a
medical diagnostic system and the monitoring circuit is local to
the diagnostic system.
22. The system of claim 20, wherein the x-ray tube is included in a
medical diagnostic system and the failure prediction circuit is
remote from the medical diagnostic system.
23. The system of claim 22, wherein the failure prediction circuit
is included in a remote service facility.
24. The system of claim 23, wherein the remote service facility is
configured for monitoring the operating parameters via a network
connection to the diagnostic system.
25. The system of claim 24, wherein the remote service facility is
configured to collect signals representative of the monitored
operating parameters via periodic data sweeps of the medical
diagnostic system.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to the field of
medical diagnostic systems employing x-ray tubes as sources of
radiation. More particularly, the invention relates to a technique
for predicting future life and possible failure of an x-ray tube
through analysis of predictive parameters sensed during use of the
tube.
BACKGROUND OF THE INVENTION
[0002] A variety of medical diagnostic and other systems are known
in which x-ray tubes are employed as a source of radiation. In
medical imaging systems, for example, x-ray tubes are used in both
x-ray systems and computer tomography (CT) systems as a source of
x-ray radiation. The radiation is emitted in response to control
signals during examination or imaging sequences. The radiation
traverses a subject of interest, such as a human patient, and a
portion of the radiation impacts a detector or a photographic plate
where the image data is collected. In conventional x-ray systems
the photographic plate is then developed to produce an image which
may be used by a radiologist or attending physician for diagnostic
purposes. In digital x-ray systems a photo detector produces
signals representative of the amount or intensity of radiation
impacting discrete pixel regions of a detector surface. In CT
systems a detector array, including a series of detector elements,
produces similar signals through various positions as a gantry is
displaced around a patient.
[0003] Depending upon the particular modality of the imaging system
and the system configuration, the x-ray tube source may be mounted
in various manners. For example, in conventional x-ray systems,
anode and cathode assemblies support the x-ray tube within a
casing. The anode assembly is coupled to a target within a glass or
metal envelope, while the cathode assembly is coupled to a cathode
plate. A metal shield or casing surrounds the glass envelope. The
volume between the casing and the envelope is filled with a cooling
medium, such as oil. A window is provided in the casing for
emitting x-rays created by controlled discharges between the
cathode plate and the target.
[0004] The x-ray tube is typically operated in cycles including
periods in which x-rays are generated interleaved with periods in
which the x-ray source is allowed to cool. A typical imaging
sequence may include a number of such sequences. Moreover, the
x-ray tube may have a useful life over a large number of
examination sequences, and must generally be available for
examination sequences upon demand in a medical care facility.
[0005] Given the demanding schedules to which x-ray tubes are often
subjected, failure of the tubes is of particular concern. Various
failure modes have been observed in x-ray tubes, and these may have
a variety of sources. For example, within the glass encasement a
vacuum or near vacuum is preferably maintained. However, due to
leaks, degradation in the cathode or anode materials, decomposition
of anode filaments, and so forth, particulates may be created or
freed within the tube. These particulates may result in eventual
failure of the tubes over time. Failure of the tubes can also be a
function of the modes of operation and user-selected parameters,
such as voltage or current.
[0006] Due to the stringent requirements and reliability demands
placed on x-ray tubes in medical diagnostic systems, special
programs may be implemented for insuring rapid replacement of the
tubes upon failure. Present procedures for replacement of x-ray
tubes in medical diagnostic systems are primarily reactionary.
Service personnel generally monitor the performance of the tubes
over time and through the various examination sequences. However,
the service personnel are often made aware of tube failures only as
they occur. When a tube does fail, to insure rapid replacement of
failed tubes a conventional response is to expedite shipment of a
replacement tube which is then installed by trained service
personnel at considerable shipping and handling expense. While the
x-ray tubes could be shipped in advance and stored on location or
in a centralized service facility, these strategies also require
inventory of relatively expensive items, again resulting in
additional costs of the service program. Such inventories may also
inconveniently occupy valuable storage space at the location.
[0007] There is a need, therefore, for an improved technique for
predicting possible failure of x-ray tubes in medical diagnostic
equipment. There is a particular need for a technique which will
accurately predict potential failure, permitting replacement tubes
to be shipped or replacement to be scheduled in an orderly fashion
prior to the actual tube failure. . Such a system could also
provide feedback for planning the tube manufacturing and assembly
process, as well as feedback to system users for planning the
replacement process.
SUMMARY OF THE INVENTION
[0008] The present invention provides a technique for predicting
possible failure of x-ray tubes designed to respond to these needs.
The technique may be employed in conjunction with various types of
systems employing x-ray tubes as radiation sources. The technique
is particularly well suited to predicting failure of x-ray tubes in
medical diagnostic equipment, such as conventional and digital
x-ray systems, CT systems, and so forth. The technique allows data
available from x-ray tube control and monitoring circuits to be
analyzed as a leading indicator of future tube failure. In a
presently preferred embodiment the parameters are monitored in data
sweeps by a centralized service facility. Alternatively, the data
may be monitored directly at the diagnostic equipment scanners and
the analyses performed locally at the medical facility.
Discriminant analysis is performed on certain candidate parameters
considered to be leading indicators of tube failure. Based upon the
results of the analysis an algorithm is developed for future
analysis of operating parameters of the tubes. When a failure is
predicted, a replacement tube may be ordered and shipped prior to
the predicted failures. The facility in which the tube is installed
may also be informed of the scheduled tube replacement, as may
field service technicians who will install the replacement tube.
The technique also facilitates reporting of the operability of the
systems incorporating the tubes to the facility.
[0009] Thus, in accordance with one aspect of the invention, a
method is provided for predicting failure of an x-ray tube. For
such failure prediction, a plurality of operating parameters of the
x-ray tube are monitored, and a failure prediction value is derived
from the monitored parameters. The failure prediction value is
compared to a desired reference value. Based upon the comparison a
signal indicative of predicted tube failure is generated. The
desired reference value may also be derived from the monitored
parameters. Moreover, the parameters may be monitored, the
comparison made, and the failure prediction signal generated either
at a tube location, or at a remote location, such as at a service
center. In a presently preferred embodiment, the parameters
monitored in the process include parameters related to anode
overcurrent events and to spits occurring within the x-ray tube.
The failure prediction value may be derived from the monitored
parameters in accordance with an algorithm established by
statistical methods, such as discriminant analysis.
[0010] The invention also relates to a method for predicting
potential failure of x-ray tubes which includes steps of monitoring
operating parameters of a population of x-ray tubes, and performing
statistical analysis of the monitored parameters. A failure
prediction algorithm is then generated from the statistical
analysis. The statistical analysis may include discriminant
analysis of a range of monitored parameters. The method may include
further steps of monitoring operating parameters of at least one
x-ray tube and predicting failure of the x-ray tube based upon the
monitored parameters and the failure prediction algorithm.
[0011] The invention also provides a system for predicting failure
of an x-ray tube. The system includes a monitoring circuit coupled
to the x-ray tube for monitoring operating parameters indicative of
possible failure. The system also includes a failure prediction
circuit coupled to the monitoring circuit. The failure prediction
circuit executes a failure prediction routine based upon the
monitored parameters and generates a failure prediction signal
based upon the routine. The failure prediction circuit and the
monitoring circuit may be provided at the same or at different
locations. In a preferred configuration, the failure prediction
circuit is positioned remote from the monitoring circuit, and
receives data representative of the monitored parameters via a
network connection.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a diagrammatical representation of a digital x-ray
imaging system incorporating an x-ray tube as a source of
radiation;
[0013] FIG. 2 is a diagram of an exemplary x-ray tube of the type
incorporated in the system of FIG. 1;
[0014] FIG. 3 is a detail view of a portion of the operative
components of the x-ray tube of FIG. 2 illustrating events which
give rise to parameters presently considered as leading indicators
of possible tube failure;
[0015] FIG. 4 is a graphical representation of an exemplary time
histogram of events presently considered indicative of future tube
failure;
[0016] FIG. 5 is a diagrammatical representation of a service
network linked to a series of scanners of the type illustrated in
FIG. 1 for monitoring tube performance, predicting possible tube
failure, and scheduling replacement of x-ray tubes; and,
[0017] FIG. 6 is a flow diagram illustrating steps in exemplary
logic for monitoring and predicting failure of x-ray tubes and for
scheduling their replacement.
DETAILED DESCRIPTION OF THE INVENTION
[0018] Turning now to the drawings, and referring first to FIG. 1,
a diagnostic imaging system 10 is illustrated diagrammatically.
System 10 includes a source of x-ray radiation 12 which employs an
x-ray tube 14. In the embodiment illustrated in FIG. 1, system 10
is a digital x-ray imaging system. However, it should be noted that
the digital x-ray system is illustrated and described herein as an
exemplary system only. The present technique for predicting tube
failure and scheduling tube replacement may be applied to any type
of imaging, diagnostic, or other system employing such x-ray tubes,
such as conventional x-ray systems, CT systems, and so forth.
[0019] In the system shown in FIG. 1, radiation source 12 receives
power and control signals from a generator or controller 16.
Generator 16 converts alternating current power to direct current
power and applies controlled pulses of DC power to tube 14 to
induce emissions of x-ray radiation for examination purposes.
Moreover, generator 16 monitors a range of operating conditions or
parameters of the tube in a manner described in greater detail
below. Power and control signals from generator 16 are conveyed to
tube 14 via a set of conductors 18.
[0020] Under the command of generator 16, tube 14 within the
radiation source produces a stream of radiation 20. The radiation
is directed through a collimator 22 and passes through a subject
24, such as a human patient, during examinations. A portion of the
radiation impacts a detector 26. In the case of a digital x-ray
system, detector 26 converts high energy photons to lower energy
photons which are detected by a series of photo diodes (not shown).
The detector electronics convert the sensed signals to image data
which is output as indicated at reference numeral 28. Detector 26
conveys the image data signals to a control/data acquisition
circuit 30. Circuit 30 also provides control signals for regulating
scanning of the detector. Moreover, circuit 30 may perform
additional signal processing or signal filtering functions.
Following such processing, circuit 30 conveys the processed image
data, indicated at reference numeral 32, to a system controller
34.
[0021] System controller 34 receives the image data and performs
further processing and filtration functions. In particular,
controller 34 derives discrete data from the acquired signals and
reconstructs useful images from the data. Controller 34 then stores
the image data in a memory or storage device 36. Device 36 may also
be used to store configuration parameters, data log files, and so
forth. In a presently preferred configuration, system controller 34
also provides signals to generator 16 for controlling emissions of
x-ray radiation from source 12. System controller 34 may also
include circuitry for providing interactive data exchange with
remote computer stations, such as a centralized service center as
described more fully below. Finally, system controller 34 includes
interface circuitry for exchanging configuration data, examination
requests, and so forth, with an operator interface 38. The system
may also include sensors for detecting specific operating
parameters, such as temperature and vibration, values of which may
also be stored and analyzed as described below. Operator interface
38 preferably includes an operator work station which permits
clinicians or radiologists to request and control specific
examinations, review data log files, view reconstructed images, and
output reconstructed images on a tangible medium, such as
photographic film.
[0022] As will be appreciated by those skilled in the art, the
foregoing system description is specific to digital x-ray imaging.
Other control and interface circuitry will, of course, be included
on other scanner types, such as conventional x-ray systems, CT
imaging systems, and so forth. In general, however, such systems
will include a generator or controller for commanding emission of
x-ray radiation for examination or calibration purposes. Moreover,
for implementation of the present technique, such systems will
include inherent capabilities for monitoring performance of the
x-ray tube during such examination or calibration sequences such
that parameters considered as leading indicators of tube failure
may be acquired, stored and analyzed.
[0023] FIG. 2 illustrates an exemplary radiation source 12,
including an x-ray tube 14. In the embodiment shown in FIG. 2, the
radiation source includes an anode assembly 40 and a cathode
assembly 42. The anode and cathode assemblies, along with x-ray
tube 14 are positioned within a casing 44 which may be made of
aluminum and lined with lead. Tube 14 is supported by the anode and
cathode assemblies within the casing. Tube 14 includes a glass
envelope 46. Within the glass envelope, adjacent to anode assembly
40, a rotor 48 is positioned. A stator 50 at least partially
surrounds the rotor for causing rotation of an anode disc during
operation, as described below. Casing 44 is filled with a cooling
medium such as oil around glass envelope 46. The cooling medium
also preferably provides high voltage insulation.
[0024] Within envelope 46, tube 14 includes an anode 52, a front
portion of which is formed as a target disc 54. A target or focal
surface 56 is formed on disc 54 and is struck by an electron beam
during operation as described below. Tube 14 further includes a
cathode 58 which is coupled to the cathode assembly 42 via a series
of electrical leads 60. The cathode includes a central shell 62
from which a mask 64 extends. The mask encloses leads 60 and
conducts the leads to a cathode cup 66 mounted at the end of a
support arm 68. Cathode cup 66 serves as an electrostatic lens that
focuses electrons emitted from a heated filament (not shown)
supported by the cup.
[0025] As will be appreciated by those skilled in the art, as
control signals are conveyed to cathode 58 via leads 60, the
cathode filaments within cup 66 are heated and produce an electron
beam 70. The beam strikes the focal surface 56 and generates x-ray
radiation which is diverted from the x-ray tube as indicated at
reference numeral 72. The direction and orientation of beam 72 may
be controlled by a magnetic field produced by a deflection coil 74.
The field produced by deflection coil 74 is also preferably
controlled by the generator and controller circuitry 16 described
above. Radiation beam 72 then exits the source through an aperture
76 in casing 44 provided for this purpose.
[0026] X-rays are produced in the x-ray tube 14 when, in a vacuum,
electrons are released and accelerated by the application of high
voltages and currents to the cathode assembly and are abruptly
intercepted by the anode target disc. The voltage difference
between the cathode and anode components may range from tens of
thousands of volts to in excess of hundreds of thousands of volts.
Moreover, the anode target disc may be rotated such that electron
beams are constantly striking a different point on the anode
perimeter. Depending upon the construction of tube 14, the desired
radiation may be emitted by substances such as radium and
artificial radiotropics, as well as electrons, neutrons and other
high speed particles. Within the envelope of tube 14, a vacuum on
the order of 10.sup.-5 to about 10.sup.-9 torr at room temperature
is preferably maintained to permit unperturbed transmission of the
electron beam between the anode and cathode elements.
[0027] As noted above, in addition to providing power and control
signals for operation of tube 14, generator 16 (see FIG. 1)
monitors operating parameters of the tube. Certain of these
parameters are considered as predictive of future tube failure in
accordance with the present technique. Such parameters may be
measured via sensors, but are preferably available from the
characteristics of the control and power signals applied to the
tube. FIG. 3 is a detailed representation of a portion of the tube
components, and illustrates certain operational anomalies which can
occur in the tube leading to detectable parameters considered to be
predictive of future tube failure.
[0028] As shown in FIG. 3, cathode cup 66 is positioned adjacent to
anode disc 54 within the interior of the x-ray tube. As power is
applied to filaments within the cathode cup, an electron beam 70 is
emitted which strikes the anode disc. While the beam is preferably
created in a vacuum, during operation of the x-ray tube
particulates 70 may be present in the tube. Such particulates may
be introduced in the tube by leaks, degradation of the system
components within the tube, decomposition of the tube filaments,
and so forth. When electron beam 70 impacts such particulate
matter, the electron beam may continue toward the anode disc as
indicated by reference numeral 80. In certain cases, however, the
electron beam may be deflected from the target disc as indicated at
reference numeral 82. Both incidents create anomalies in the
signals exchanged between the tube and generator 16 which can be
detected by the generator. In general, such events create high
current discharges. When particulate is encountered by the electron
beam and the beam continues along its path to impact the anode
disc, an anode overcurrent event may be recorded. Moreover, where
the electron beam is diverted from the anode disc by the
particulate, the high current discharge event is generally termed a
"spit" in the art. In addition to detecting current anomalies of
these types, generator 16 is capable of distinguishing between
anode overcurrent events and spits. Such events are recorded by
system controller 34 and saved within memory circuitry 36. As will
be appreciated by those skilled in the art, various other anomalies
may be detected and recorded in a similar manner.
[0029] In addition to recording the actual number of anode
overcurrent events and spits, system controller 34 preferably
derives additional parameters from at least one of these. In the
present embodiment, for example, the system controller records the
number of spits per day of operation. Moreover, the current to the
x-ray tube may be interrupted upon the occurrence of a spit, and
subsequently reapplied during an examination sequence. Such events
are recorded by the system controller and logged for each day of
operation. However, a maximum "spit rate" may be imposed in terms
of spits per unit time. If the spit rate is greater than a preset
limit, a scan or examination is typically aborted. For example, in
a present embodiment of the system, a spit rate of over 32
spits/second causes the current examination scan to be aborted.
Such events are termed "spit rate exceeded" errors or "SREs." The
number of SREs per day is also monitored by system controller 34
and stored in memory circuitry 36.
[0030] Through extensive analysis of operating parameters for a
population of x-ray tubes, it has been found that certain of the
parameters monitored by generator 16 and system controller 34
provide accurate predictive indicators of tube failure. From this
analysis a model algorithm has been developed which permits the
monitored parameters to be correlated with a potential for tube
failure. While algorithms including a large number of monitor
parameters may be included in such failure prediction analyses, in
a present embodiment the rate of occurrence of anode overcurrent
events and SREs are used to generate failure prediction values
which may be compared to evaluate the potential for short term tube
failure. As described more fully below, discriminant analysis is
used in the present technique to identify and to properly weight
such predictive parameters in the algorithm, and to relate them in
a value considered predictive of tube failure.
[0031] By way of example, FIG. 4 is a graphical representation of a
"Z-score" derived from data files of SREs for an exemplary x-ray
tube. The Z-score is calculated based upon the occurrences of SREs
by the following relationship: 1 Z - score = SRE 3 d - SRE L SRE ;
( eq . 1 )
[0032] Where SRE.sub.3d is the average number of SREs per day over
a previous three day period, SRE.sub.L is the average number of
SREs per day over the life of the tube, and .sigma..sub.SRE is the
standard deviation of the number of daily SREs over the life of the
tube.
[0033] FIG. 4 represents a histogram or curve 84 of the Z-score
over time. The Z-score may be graphed over a base line of time 86
and a magnitude on a vertical axis 88. As indicated by the
histogram, the Z-score is generally expected to remain at an
extremely low or null level throughout most of the useful life of
the x-ray tube. At some time during the life of the tube, however,
a sharp rise will be detected in the Z-score, such as due to an
increase in particular matter within the tube resulting in an
increase in SREs, as indicated by the sharp rise 90 in the
histogram. In many systems the rise will be followed by a peak 92
and a subsequent drop off. It is believed that such a drop off may
occur due to a tendency for a particular matter to drop to the
bottom of the tube.
[0034] As indicated above, in accordance with the present
technique, discriminant analysis is used to determine weighting
coefficients for the parameters considered to be predictive of
failure. In the presently preferred technique, two weighted
functions are obtained through the discriminant analysis as
follows:
Idf1=C.sub.1+K.sub.1 (adjrate)+K.sub.2(aoc) (eq. 2); and,
Idf2=C.sub.2+K.sub.3 (adjrate)+K.sub.4(aoc) (eq. 3);
[0035] where the value Idf1 is a first linear discriminant function
value, Idf2 is a second linear discriminant function value, C.sub.1
and C.sub.2 are constants resulting from the discriminant analysis,
K.sub.1, K.sub.2, K.sub.3 and K.sub.4 are coefficients resulting
from the discriminant analysis, adjrate is the Z-score for the
tube, and the value aoc is the count of daily anode overcurrent
events. In the present embodiment, the values for the constants and
coefficients applied in equations 2 and 3 are as follows:
1 C.sub.1 -0.12588 C.sub.2 -0.00937 K.sub.1 0.83695 K.sub.2 0.19511
K.sub.3 0.1833 K.sub.4 0.19962.
[0036] In the present embodiment, if the value of Idf2 is found to
be greater than or equal to the value of Idf1 no imminent failure
is predicted for the tube. On the contrary, when the value of Idf1
exceeds the value of Idf2, the tube is considered to be near
failure, and its replacement is scheduled as summarized below.
[0037] It should be noted that the foregoing values and
correlations have been determined through extensive analysis of a
variety of parameters and their fluctuations over the life of a
population of x-ray tubes. In accordance with the present
technique, the statistical analyses may be employed to identify the
particular parameters discussed above, or additional or different
parameters which may be considered indicative of impending tube
failure. Similarly, the particular constant and weighting values
indicated above may be altered or replaced by other values to
accurately predict potential tube failure.
[0038] As noted above, in the present embodiment the parameters
considered indicative of future tube failure are monitored at the
individual diagnostic or imaging system in which the tube is
installed. The analysis of these parameters may also be performed
at the diagnostic system, or may be performed remotely, such as at
a central service facility. FIG. 5 represents a diagrammatical
representation of a number of diagnostic systems or scanners 94
coupled to such a central service facility via a remote data
exchange network. In the embodiment illustrated in FIG. 5 scanners
94, which may be similar to or different from one another, include
interactive communications hardware and software for communicating
over a network represented generally at reference numeral 96.
Network 96 may include an intranet, internet or other network, such
as the Internet. In such cases, the scanners are preferably
provided with network software, such as a graphical user interface
and browser permitting operations personnel at a facility to send
and receive messages with the central service facility. The network
96 permits the scanners to be coupled to a web server 98 which
manages communications and data traffic between the central service
facility and the scanners on the network. Alternatively, the
scanners may be designed to be linked directly to the service
facility by a modem-to-modem connection, as indicated by the letter
M in FIG. 5.
[0039] The server 98 may transmit and receive data with the
scanners, and with a central service facility 102 through a
firewall 100, particularly with a Point-to-Point Protocol (PPP).
Firewall 100 may include any of various known security devices for
preventing access to central service facility 102 except by
recognized subscribers and other users. Central service facility
102 includes one or more central computers 104 which coordinates
data exchange between the network scanners and work stations 106 at
the central service facility. Work stations 106 may, in turn, be
staffed by service personnel. Computer 104 may also be coupled for
data exchange with one or more servers 108 at the central service
facility. Moreover, computer 104 or other devices at the central
service facility may be coupled or configured to be coupled to
other internal or external networks, such as for exchanging data
with databanks 110 through an additional firewall 112. In the
presently preferred configuration, databanks 110 may be local to or
remote from the central service facility, and may contain data
relating to history on particular scanners, families of scanners,
populations of tubes, and the like. Such data is compiled over time
by transmission from computer 104, and is subsequently accessible
by computer 104 to establish or revise the particular algorithms
employed for predicting future failure of the tubes. Finally, the
central service facility may be coupled to a warehouse 114 or
similar facility for ordering shipment of replacement tubes
depending upon the outcome of the analysis summarized above.
[0040] It should be noted that in the presently preferred
embodiment, the technique for predicting possible failure of x-ray
tubes, and scheduling their replacement, may incorporate planning
for production, transportation, warehousing, and similar processes.
Accordingly, as illustrated in FIG. 5, the block 114 should be
understood to include manufacturing and assembly operations,
storage facilities, transportation infrastructure, and the like.
Thus, based upon predicted failure of a particular type or types of
tubes, the system may schedule manufacturing or assembly
operations, cause parts or sub-components to be ordered or
assembled, and the like. Similarly, tubes for which failure is
predicted or possible may be transported or assigned to specific
storage locations or forward staging areas at or near the locations
where the tubes will be needed. In a presently preferred
configuration, the system may sweep tube parameters from a variety
of scanners, associate possible tube failures with a list of
subscriptions stored in a database 110, and command manufacturing,
transportation, storage and other upstream replacement processes,
as well as the actual tube replacement itself.
[0041] In operation, the central service facility 102 can access
scanners 94 at will via the various network connections. Periodic
sweeps of the scanners may be implemented in which the data
necessary for evaluation of possible future tube failure is
acquired with or without intervention from service or operations
personnel at the institutions in which the scanners are installed.
Moreover, similar network transfer of the data may originate at the
individual scanners. Once the information has been obtained by the
service facility, the computations and comparisons required for
prediction of possible tube failure are made as described above. If
the prediction is found to be positive, replacement of the tube is
scheduled.
[0042] The foregoing structure also permits various alternative
management procedures to be implemented. For example, the data
acquisition and comparisons may be made directly at the individual
scanners. In such cases, the algorithm may be stored a priori at
the scanners, or may be downloaded from the service facility to the
scanners. When the scanner determines that a tube failure is
possible or imminent, a message can be sent from the individual
scanner to the central service facility, which then schedules for
tube replacement. Similarly, when multiple scanners or diagnostic
systems are provided in an institution, a central management
station may be linked to the scanners in an internal network. The
central management station may then collect the monitored parameter
data and perform the failure prediction, or may transmit the
information to a service facility for analysis.
[0043] It is also contemplated that the central service facility
may conduct the evaluations described herein and schedule tube
replacement only for scanners for which a conforming service
contract or agreement has been completed. Accordingly, in
appropriate situations, the central service facility may only sweep
data from service subscribing scanners, or may transmit updated
failure analysis algorithms to such subscribing scanners.
[0044] It should also be noted that the present technique permits a
remote field engineer station to be integrated into the tube
replacement process, as shown at reference numeral 116 in FIG. 5.
As will be appreciated by those skilled in the art, field service
engineers may access information on replacement of tubes through
the same network used to link the scanners to the service facility.
When replacement of a tube is scheduled, therefore, the field
engineer may be notified of the need to attend to such
replacement.
[0045] The foregoing procedure is summarized in FIG. 6. As shown at
step 122 in FIG. 6, subscribing scanners or facilities are
periodically swept to obtain data on parameters considered
indicative of possible x-ray tube failure, such as anode
overcurrent events, and SREs rates or Z-scores derived from the SRE
data. Alternatively, the data collection may be performed locally
at the diagnostic system. All or a portion of the analysis may also
be performed at the diagnostic system, which may then flag possible
failure to the service facility. At step 124, the data is compiled,
either at the central service facility or at the scanners (or
internal management station), to obtain the failure prediction
values needed for the prediction analysis. At step 126 the
predictive analysis is performed, such as through the calculations
summarized above in equations 2 and 3. The predictive failure
analysis concludes at step 128 wherein a comparison is made between
the failure prediction values, as summarized above. Where the
result of the comparison indicates that failure is not imminent,
this fact may be reported to the scanner or institution in which
the scanner is installed, as indicated at step 130. The periodic
sweeping and analysis summarized above then is repeated over the
course of the tube life.
[0046] If the result of the comparison made at step 128 is
affirmative, this fact is reported to the scanner or institution at
step 132. In addition, a service order is generated at step 134 and
a replacement tube is ordered from a warehouse or factory as
indicated at reference numeral 114 in FIG. 5. Moreover, the service
order includes an electronic message notification sent to a field
service engineer, such as via a remote station 116, to inform the
field service engineer that replacement of the tube is required.
Alternatively, the field service engineer may place a service order
in response to receipt of a failure prediction or replacement
scheduling message.
[0047] As noted above, the method may include coordination of other
upstream operations in addition to the actual scheduling of the
tube replacement. Thus, parts or subcomponents may be ordered,
manufactured, or assembled based upon the predicted failure.
Moreover, where local warehousing or staging areas are provided,
tubes may be shipped in advance to such locations in anticipation
for the predicted failure. Also, messages provided via the present
technique, both to field service engineers, as well as to scanner
operations personnel, may include an indication of remedial or
other measures which can be implemented to avoid or forestall the
predicted tube failure pending its replacement.
[0048] The foregoing technique thus permits effective prediction of
possible tube failure by algorithms derived from actual occurrences
of historic tube failures. The algorithms may be refined and
altered over time as desired. Moreover, alternative algorithms may
be developed for particular families or types of tubes, or for
particular types of diagnostic equipment. Upon implementation, the
technique facilitates planned replacement of the tubes with little
or no intervention from operations personnel. At the same time, the
technique allows the institutions to be kept abreast of the
operational state of the x-ray tubes, and of scheduled or needed
replacement as these are identified by the central service
facility. Additional costs of stocking and transporting replacement
of tubes after failure may thereby be reduced or eliminated, as may
costs and inconvenience associated with downtime of diagnostic
equipment.
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