U.S. patent application number 10/801416 was filed with the patent office on 2005-01-20 for hyperthermia treatment systems and methods.
Invention is credited to Cover, Roger W., Mioduski, Paul C., Rosato, Jerry F..
Application Number | 20050015125 10/801416 |
Document ID | / |
Family ID | 33029944 |
Filed Date | 2005-01-20 |
United States Patent
Application |
20050015125 |
Kind Code |
A1 |
Mioduski, Paul C. ; et
al. |
January 20, 2005 |
Hyperthermia treatment systems and methods
Abstract
Systems and methods are disclosed to control the temperature of
an RF hyperthermia system with minimum overshoot and to improve
safety by, among other things, detecting a defective temperature
sensor. Temperature overshoot may be minimized by compensating for
the short-term temperature difference between the area being
treated and the applicator delivering the RF energy. The RF energy
may heat the tissue and then the tissue may transfer heat to the
applicator sensor. The system may also adapt to various applicator
sizes and shapes by modifying control loop coefficients based on
initial probe response.
Inventors: |
Mioduski, Paul C.; (Tucson,
AZ) ; Cover, Roger W.; (Oro Valley, AZ) ;
Rosato, Jerry F.; (Tucson, AZ) |
Correspondence
Address: |
SQUIRE, SANDERS & DEMPSEY L.L.P.
Two Renaissance Square
Suite 2700
40 North Central Avenue
Phoenix
AZ
85004-4498
US
|
Family ID: |
33029944 |
Appl. No.: |
10/801416 |
Filed: |
March 15, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60455022 |
Mar 14, 2003 |
|
|
|
Current U.S.
Class: |
607/102 ;
607/101 |
Current CPC
Class: |
A61B 2018/00666
20130101; A61B 2018/00988 20130101; A61B 2018/00791 20130101; A61B
2018/00821 20130101; A61B 2017/00734 20130101; A61B 2018/00779
20130101; A61B 18/1233 20130101; A61B 2017/00123 20130101; A61B
2017/00092 20130101; A61B 2018/00892 20130101 |
Class at
Publication: |
607/102 ;
607/101 |
International
Class: |
A61F 007/00; A61F
007/12; A61F 002/00 |
Claims
What is claimed is:
1. A method of operating a hyperthermia treatment system,
comprising: measuring a temperature that is within an allowable
range of operation for the system; and determining whether to
continue operation of the system based on a parameter related to
the measured temperature.
2. The method of claim 1 wherein the parameter comprises the
measured temperature.
3. The method of claim 1 wherein the parameter comprises a
temperature difference between the measured temperature and another
measured temperature.
4. The method claim 1 wherein the parameter comprises a rate of
change of temperature.
5. A medical device for performing hyperthermia treatment,
comprising: a heat source for providing heat for the hyperthermia
treatment; a temperature sensor for measuring temperature from the
providing of heat; and a processor that determines whether to
continue the hyperthermia treatment based on a parameter related to
a measured temperature that is within an allowable range of
operation for the device.
6. The device of claim 5 wherein the parameter comprises the
measured temperature.
7. The device of claim 5 wherein the parameter comprises a
temperature difference between the measured temperature and another
measured temperature.
8. The device claim 5 wherein the parameter comprises a rate of
change of temperature.
9. A method of operating a hyperthermia treatment system,
comprising: performing a plurality of tests to determine whether
the hyperthermia treatment system is operating properly; and
terminating operation of the hyperthermia treatment system in
response to failure of any test of a predefined set of the tests
and preventing further operation of the hyperthermia treatment
system until the hyperthermia treatment system is reset for further
operation at a specified facility.
10. The method of claim 9 wherein the specified facility comprises
a manufacturer of the hyperthermia treatment system.
11. The method of claim 9 wherein the tests are for verifying
proper operation inside and outside of a housing for the
hyperthermia treatment system.
12. The method of claim 11 wherein the tests for verifying proper
operation inside the housing comprise the predefined set of the
tests.
13. The method of claim 11 further including terminating operation
of the hyperthermia treatment system in response to failure of any
test of a predefined second set of the tests and permitting further
operation of the hyperthermia treatment system after a local reset
is performed.
14. The method of claim 13 wherein the tests for verifying proper
operation outside of the housing comprise the predefined second set
of the tests.
15. The method of claim 9 wherein the reset may be performed only
after required repairs are completed.
16. The method of claim 9 wherein the reset includes providing a
special code to the hyperthermia treatment system.
17. A method of operating a hyperthermia treatment system,
comprising: determining when the hyperthermia treatment system has
provided a desired temperature for treatment; evaluating one or
more criteria pertaining to a thermal dose being delivered; and
terminating a treatment when evaluation of one or more of the
criteria indicates undertreatment of a patient.
18. A medical device for performing hyperthermia treatment,
comprising: a heat source for providing heat for the hyperthermia
treatment; a temperature sensor for measuring temperature from the
providing of heat; and a processor that determines when the
hyperthermia treatment system has provided a desired temperature
for treatment, evaluates one or more criteria pertaining to a
thermal dose being delivered, and terminates a treatment when
evaluation of one or more of the criteria indicates undertreatment
of a patient.
19. A method of operating a hyperthermia treatment system,
comprising: monitoring parameters relating to operation of the
hyperthermia treatment system; and playing over the system a
predefined announcement when a predefined operational
characteristic of the system has been detected.
20. A medical device for performing hyperthermia treatment,
comprising: a heat source for providing heat for the hyperthermia
treatment; a temperature sensor for measuring temperature from the
providing of heat; and a processor that monitors parameters
relating to operation of the hyperthermia treatment system and
plays over the system a predefined announcement when a predefined
operational characteristic of the system has been detected.
21. The device of claim 5 wherein the system is used to treat at
least one of an abnormality, ailment, condition, disease, disorder
and wound found on at least one of a patient's skin and tissue.
22. The device of claim 21 wherein the at least one of an
abnormality, ailment, condition, disease, disorder and wound
include at least one of Actinic Keratosis, Angioma, Acrochordon,
Atypical Mycobacteria, Chromoblastomycosis, Cystic Acne, Clavus,
Cutaneous Leishmaniasis, Dermatophytosis, Epidermoid Cysts,
Fibroma, Hydrocystoma, Keloids, Molluscum Contagiosum, Mycetoma,
Seborrheic Keratosis, Sporotrichosis, Syringoma and Warts.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is related to, claims priority from and
incorporates herein by reference co-pending U.S. provisional
application Ser. No. 60/455,022, filed Mar. 14, 2003, entitled
"HYPERTHERMIA TREATMENT SYSTEM WITH TEMPERATURE CONTROL ALGORITHM
AND METHOD" by Paul C. Mioduski, Roger W. Cover and Jerry F.
Rosato.
DESCRIPTION OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to medical systems and
methods, and, more particularly, to hypertherrhia treatment systems
and methods.
[0004] 2. Background of the Invention
[0005] Hyperthermia treatment systems and methods are well known
for treating abnormal tissue. For example, it is well known to use
such systems to apply high frequency current from a probe through
the tissue under treatment to another probe, which causes the
temperature of the tissue to rise to a selected level high enough
to kill abnormal tissue, without permanently damaging adjacent
healthy tissue.
[0006] Use of hyperthermia treatment systems and methods to
noninvasively or minimally-invasively treat abnormal or malignant
tissue has increased significantly in recent years. Regarding
hyperthermia treatment systems and methods, studies have shown that
for a specific biological effect, there is an inverse relationship
between the exposure time of the treatment and the treatment
temperature. For example, an increase of 1 degree Celsius to the
treatment temperature may reduce the treatment exposure time to
achieve a desired effect by a factor of 2. Treatment duration
multiplied by the treatment temperature is known as the thermal
dose. At certain thermal dose levels, abnormal tissue is affected
differently than normal tissue. When heat is applied to normal
tissue, blood vessels dilate, thus dissipating the heat from the
tissue and preserving cellular integrity. Abnormal tissue, such as
tumor tissue, has a different blood supply structure that is unable
to defuse the heat as well. Thus, application of heat results in
the destruction of the abnormal tissue.
[0007] U.S. Pat. No. 4,531,524 ("'524 patent"), entitled "Circuit
Apparatus and Method for Electrothermal Treatment of Cancer Eye",
issued on Jul. 30, 1985, to present inventor Paul Mioduski. The
'524 patent discloses a hand-held electronic probe including
circuitry for passing high frequency current through malignant eye
tissue of livestock, or other tissue such as warts. The circuitry
includes a thermistor in a probe tip that contacts the malignant
eye tissue and produces a voltage that controls a voltage
controlled oscillator (VCO) that drives an audio transducer. If the
probe tip is held against the malignant tissue with sufficient
force, the pitch of the sound emitted by the audio transducer
steadily increases, indicating to the user that the proper pressure
is being maintained to ensure heating of the tissue to the desired
treatment temperature. The circuitry then causes the transducer to
emit periodic beeping sounds which the user can count to ensure
that the tissue is maintained within a desired temperature range
for a desired amount of time during which the circuitry responsive
to the thermistor varies the duty cycle of the high frequency
current applied to the tissue so as to maintain the desired
temperature within a predetermined range. Initially, high frequency
current is applied at a substantially reduced duty cycle in order
to prevent excessive temperature lag between the tissue and the
probe tip, so as to prevent initial temperature overshoot of the
tissue before the thermistor and circuitry can respond to reduce
the duty cycle.
[0008] A problem with the hyperthermia treatment systems and
methods disclosed in the '524 patent results from the RF energy
being applied between two probes of the applicator. Specifically,
there is a time lag or delay between the time at which the skin of
the abnormal tissue reaches a given temperature and the time at
which the thermistor in the probe detects the temperature of the
abnormal tissue. This lag causes undesirable temperature overshoot
of the abnormal tissue during temperature ramp-up, which can harm
the patient. To compensate for such overshoot, system gain may be
reduced, which eliminates or reduces temperature overshoot, but
also increases the time to reach temperature, which, undesirably,
increases the total treatment time. Additionally, reducing system
gain limits the accuracy that can be achieved for maintaining
tissue temperature at a desired level after initial ramp-up. Thus,
there are difficult trade-off considerations.
[0009] It is desirable to know whether the temperature sensor in a
hyperthermia system is functioning correctly. If the temperature
sensor is not operating correctly, it could result in burning the
patient, if the measured temperature is below the actual treatment
temperature, or it could result in under-treating the patient, if
the measured temperature is above the actual treatment
temperature.
[0010] Some lesions are too large to fit between the RF probes, and
therefore cannot be treated in a single operation cycle. Thus, a
first area of the lesion is treated, and then the RF probes are
moved to an adjacent, slightly overlapping region and the operation
cycle is repeated. However, because the overlap treatment site is
at an elevated temperature, the control loop may be unstable during
the initial portion of the treatment. Depending on the amount of
overlap, the hyperthermia treatment system disclosed in the '524
patent may have experienced temperature overshoot, failed to reach
the preselected treatment temperature, or took too long to reach
the preselected treatment temperature because its control loop was
adjusted to start at a temperature of approximately 30 degrees
Celsius.
[0011] Another consideration in hyperthermia treatment systems is
the amount of pressure required by the applicator being used. The
problem of maintaining the correct pressure on various applicators
without distracting the doctor's attention from the tumor is fairly
difficult. Anything that causes the doctor to inadvertently move
the probes along the tumor can be very detrimental to achieving the
desired treatment. But the skin may be dry, and contact pressure
may be low or high, and how much power is being accepted by the
tumor may not be very well known.
[0012] There is an unmet need for improved hyperthermia treatment
systems and methods which address these and other considerations of
the related art.
SUMMARY OF THE INVENTION
[0013] In accordance with an embodiment of the invention, a method
of operating a hyperthermia treatment system is disclosed,
comprising measuring a temperature that is within an allowable
range of operation for the system, and determining whether to
continue operation of the system based on a parameter related to
the measured temperature.
[0014] In accordance with another embodiment of the invention, a
medical device for performing hyperthermia treatment is disclosed,
comprising a heat source for providing heat for the hyperthermia
treatment, a temperature sensor for measuring temperature from the
providing of heat, and a processor that determines whether to
continue the hyperthermia treatment based on a parameter related to
a measured temperature that is within an allowable range of
operation for the device.
[0015] In accordance with a further embodiment of the invention, a
method of operating a hyperthermia treatment system is disclosed,
comprising performing a plurality of tests to determine whether the
hyperthermia treatment system is operating properly, and
terminating operation of the hyperthermia treatment system in
response to failure of any test of a predefined set of the tests
and preventing further operation of the hyperthermia treatment
system until the hyperthermia treatment system is reset for further
operation at a specified facility.
[0016] In accordance with another embodiment of the invention, a
method of operating a hyperthermia treatment system is disclosed,
comprising determining when the hyperthermia treatment system has
provided a desired temperature for treatment, evaluating one or
more criteria pertaining to a thermal dose being delivered, and
terminating a treatment when evaluation of one or more of the
criteria indicates undertreatment of a patient.
[0017] In accordance with another embodiment of the invention, a
medical device is disclosed for performing hyperthermia treatment,
comprising a heat source for providing heat for the hyperthermia
treatment, a temperature sensor for measuring temperature from the
providing of heat, and a processor that determines when the
hyperthermia treatment system has provided a desired temperature
for treatment, evaluates one or more criteria pertaining to a
thermal dose being delivered, and terminates a treatment when
evaluation of one or more of the criteria indicates undertreatment
of a patient.
[0018] In accordance with still another embodiment of the
invention, a method of operating a hyperthermia treatment system is
disclosed, comprising monitoring parameters relating to operation
of the hyperthermia treatment system, and playing over the system a
predefined announcement when a predefined operational
characteristic of the system has been detected.
[0019] In accordance with still another embodiment of the
invention, a medical is disclosed device for performing
hyperthermia treatment, comprising a heat source for providing heat
for the hyperthermia treatment, a temperature sensor for measuring
temperature from the providing of heat, and a processor that
monitors parameters relating to operation of the hyperthermia
treatment system and plays over the system a predefined
announcement when a predefined operational characteristic of the
system has been detected.
[0020] Additional objects and advantages of the invention will be
set forth in part in the description which follows, and in part
will be obvious from the description, or may be learned by practice
of the invention. The objects and advantages of the invention will
be realized and attained by means of the elements and combinations
particularly pointed out in the appended claims.
[0021] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory only and are not restrictive of the invention, as
claimed.
[0022] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate several
embodiments of the invention and together with the description,
serve to explain the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1A is a perspective view of a hyperthermia treatment
system, in accordance with systems and methods consistent with the
present invention.
[0024] FIG. 1B is a block diagram of a hyperthermia treatment
system, in accordance with systems and methods consistent with the
present invention.
[0025] FIG. 2A is a block diagram of an RF module and associated
components from FIG. 1B, in accordance with systems and methods
consistent with the present invention.
[0026] FIG. 2B is a block diagram of a microcontroller module and
associated components from FIG. 1B, in accordance with systems and
methods consistent with the present invention.
[0027] FIG. 3 is a schematic diagram of an applicator, a handset,
and a cable of a hyperthermia treatment system from FIG. 1B, in
accordance with systems and methods consistent with the present
invention.
[0028] FIG. 4 is a schematic diagram of an RF oscillator,
modulator, and filter circuit from FIG. 2A, in accordance with
systems and methods consistent with the present invention.
[0029] FIGS. 5A and 5B are flow charts depicting methods for
operating a hyperthermia treatment system, in accordance with
systems and methods consistent with the present invention.
[0030] FIGS. 6A-6F are flow charts depicting in greater detail
methods for operating a hyperthermia treatment system as depicted
in FIGS. 5A and 5B, in accordance with systems and methods
consistent with the present invention.
DESCRIPTION OF THE EMBODIMENTS
[0031] Reference will now be made in detail to the present
exemplary embodiments of the invention, examples of which are
illustrated in the accompanying drawings. Wherever possible, the
same reference numbers will be used throughout the drawings to
refer to the same or like parts.
[0032] FIG. 1A shows a hyperthermia treatment system 1 for treating
skin and/or tissue (hereafter collectively referred to as
"tissue"). Tissue treatment may include treatment for any
abnormality, ailment, condition, disease, disorder, wound or the
like, which may include: Actinic Keratosis, Angioma, Acrochordon,
Atypical Mycobacteria, Chromoblastomycosis, Cystic Acne, Clavus,
Cutaneous Leishmaniasis, Dermatophytosis, Epidermoid Cysts,
Fibroma, Hydrocystoma, Keloids, Molluscum Contagiosum, Mycetoma,
Seborrheic Keratosis, Sporotrichosis, Syringoma and Warts.
[0033] Hyperthermia treatment system 1 may comprise a localized
current field RF instrument and may include a main unit 2 having a
front panel 2A. A treatment temperature selection knob 2B may
provide the function of setting a desired treatment temperature. An
LCD display 2C may display a measured temperature. A sound control
knob 2D may set a volume of any sound emitted by a speaker 7, as
shown in FIG. 1B. A handle 2F may be provided on top of main unit
2. A conventional RF connector 8 may be connected to a cable 9,
which may be connected to a handset 10. An applicator 11 may be
plugged into handset 10. As described below, probes 36A and 36B
(FIG. 3) of applicator 11 may be pressed against abnormal tissue
(i.e., tissue of a tumor or other lesion) which may cause RF energy
to be conducted from one probe through the abnormal tissue to the
other probe in order to elevate the temperature of the tissue to a
selected value and then maintain it at the selected value for a
predetermined time. Plug-in handset 10 may accept various sized and
shaped applicators 11 for various kinds of tissue.
[0034] One or more indicators, e.g., LED indicator lights 2E may
perform various functions, depending on the operating mode which
may include, indicating the elapsed treatment time, the level of
battery charge or system self-test diagnostic results. The battery
indicator mode of LEDs 2E may also indicate the approximate number
of treatments that can be made on the remaining battery charge.
Hyperthermia treatment system 1 may be battery-operated, to avoid
any possibility of electrical shock to the patient.
[0035] Referring to FIG. 1B, hyperthermia treatment system 1 may
include a main unit 2 which may include an RF module which may be 3
mounted in a rear portion of a housing 28 of main unit 2 and a
microcontroller module 5 which may be mounted in a front portion of
housing 28. One or more batteries 6 and a speaker 7 may be included
in housing 28, as shown.
[0036] Hyperthermia treatment system 1 may use one or more
temperature sensor e.g., a thermocouple 29 (FIG. 3) to measure
temperature in one or more of the applicator probes to assist in
controlling the amount of applied RF energy so as to control the
temperature of the treatment site during temperature amp-up to a
selected value and then to assist in maintaining temperature to
within a range, e.g., .+-.1 degree Celsius of the desired
temperature for a predetermined treatment time. The treatment time
may be of any desired duration, however, it is desirable to have
treatment times of no more than approximately 90 seconds. Any
desired treatment site temperature may be used, however, a
preferred range is from 38 degrees Celsius to 65 degrees
Celsius.
[0037] Hyperthermia treatment system 1 may control ramping up of
the temperature of the treatment site to a selected treatment
value. The pitch of an audible sound that may be produced by
speaker 7 may indicate the progress of the ramp-up to the desired
temperature. After the treatment site (as may be measured by
thermocouple 29) reaches the preselected value, a distinct sound
may be produced, such as a beep played at the same regular
interval, e.g., 2 seconds for same time period, e.g., 30 seconds.
After a predetermined period of time, e.g., 30 seconds with the
tissue at the desired treatment temperature, a different sound,
e.g., longer beeping sound may be produced. During treatment,
indicator lights 2E may indicate how long the treatment site has
been at the desired temperature, e.g., (30, 60, and 90
seconds).
[0038] Referring to FIG. 2A, RF module 3 may include power supply
circuitry 15 that may be powered by batteries 6, which may comprise
two six volt batteries connected in series and which may have been
previously been charged by charger circuit 14. Charger circuit 14
may be connected by a switch 13 which may be on the rear panel of
main unit 2, to an AC adapter circuit 12. A shutter which may be
associated with switch 13 may prevent a battery charger (not shown)
from being plugged into hyperthermia treatment system 1 while it is
being used to prevent possible electrical shock to a patient due to
high-voltage transients that may be present on external power lines
or to a malfunction of the AC adapter. Power supply circuitry 15
may provide a +12 volt supply voltage on a conductor 17 and a -12
volt supply voltage on a conductor 16 to power the various circuits
in hyperthermia treatment system 1. RF module 3 may also include RF
circuitry 18 that may include a crystal oscillator circuit 19 which
may produce a 6.78 MHz signal 20 which may be applied as an input
to an RF modulator circuit 21, and may also include various signal
conditioning circuits (not shown).
[0039] RF modulator circuit 21 may be controlled by an RF control
signal 25 and an RF enable signal 26 and may produce a modulated RF
signal 22 that may be applied to an input of a filter 23. Filter 23
may produce an RF output signal 27 that may be applied to a
terminal of connector 8, through cable 9 and handset 10 and applied
across conductive probes 36A and 36B of applicator 11. Filter 23
may produce RF feedback signal 35 which may represent the amplitude
of the RF voltage on conductor 27, and may be applied as an input
to a microcontroller module 5 of FIG. 2B. Filter 23 may also
produce a scaled RF feedback signal 24 which may be applied to
another control input of RF modulator 21. Scaled RF feedback signal
24 may be scaled-down version of RF feedback signal 35, and may be
scaled down to a range that may be compatible with the range of RF
control signal 25 that may represent the RF output voltage 27 being
called for by microcontroller 40. As subsequently explained, the
scaled RF feedback signal 24 may represent either the RF voltage
(in one embodiment) or the RF power (in another embodiment) that
may be applied to the treatment site being contacted by the probes
of applicator 11 The oscillator output may be modulated to control
the amplitude of the output 22 of RF modulator 21, which may then
be filtered and transmitted to handset 10 and probes 36A and
36B.
[0040] In contrast to the related art which produces an unknown RF
output voltage and only begins to reduce the power output as the
selected temperature is closely approached, the disclosed
embodiment of the present invention may use scaled RF feedback
signal 24 with RF circuitry 18 so as to cause the voltage of the RF
modulator output signal 22 to be a known quantity, regardless of
the load impedance constituted by the treatment site contacted by
the applicator probes and/or the impedance between the probe
surfaces and the tissue. The feedback loop may regulate the amount
of energy going into the RF output transformer which may produce
the 6.78 MHz signal by varying the duty cycle of the signal going
into the base of the output transistor, and that may allow the
temperature overshoot of the treatment site to be minimized and at
the same time also may allow the fastest practical ramp-up of the
treatment site temperature to the preselected value. If the RF
feedback circuit is not used to linearize the oscillator circuit,
the ramp time may have to be extended in order to prevent
temperature overshoot.
[0041] RF oscillator 19, which may be a crystal oscillator, may
generate an output 20 having a frequency of 6.78 MHz, which may be
an input to RF modulator 21, which may produce an RF signal 22 that
may be input to filter 23. The RF control signal 25 from
microcontroller 40 may establish the desired RF output signal level
which may be selected by means of temperature selection knob 2B. RF
enable signal 26 may be generated by microcontroller 40, which may
enable or disable the RF output signal 27. The filter 23 may
produce an RF feedback error signal, namely, RF feedback signal 35,
that, in effect may indicate to microcontroller 40 whether the
system is producing the desired output voltage. Such information
may help determine whether or not good electrical and thermal
contact of probes 36A and 36B is being made to the treatment site
or whether there are other problems with applicator 11, such as a
non-operational RF oscillator or a short circuit across the RF
probe. Treatment may be automatically terminated by microcontroller
40 if the RF feedback signal 35 is not within a reasonable
range.
[0042] Another approach to control of the amount of RF energy
delivered to the treatment site is to sense the amount of RF power
(rather than the amount of voltage) that may be delivered to and
absorbed by the treatment site. This may provide better control of
the amount of RF power delivered and absorbed, because it may
measure the impedance of the "load" to which the RF energy may be
supplied and may indicate whether more or less power should be
applied by the RF circuitry 18. A multiplier circuit (not shown)
may be used to compute the power delivered to the treatment site by
multiplying the voltage on conductor 27 by the current through it,
and the resulting value may determine the value of the signal on
feedback conductor 24. Providing power feedback instead of voltage
feedback may allow faster ramp-up times and lower overshoot. It may
predict the rate of change of temperature by measuring the power
absorption rate.
[0043] In FIG. 2A, the scaled RF feedback signal 24 may linearize
the relationship of the voltage on conductor 22 to the RF control
signal 25, and may substantially improve the accuracy of control of
the amount of RF power delivered to the treatment site. As a
result, microcontroller 40 may use the complete range of its
internal D/A converters, which may improve loop stability, maximum
ramp rate, and temperature accuracy when at the desired
temperature.
[0044] As subsequently explained, a cold junction compensation
circuit 30 may be built into connector 8. A pair of conductors 34
may be connected through corresponding terminals of connector 8 and
through cable 9 and handset 10 to the terminals of thermocouple 29
which may be in RF probe 36A. A conductor 33 may be connected to
the output of a conventional cold junction compensation circuit 30
and may conduct a compensation signal that may be used to adjust
the thermocouple output signal 34 for the amount of offset caused
by a copper-to-constantan junction of a typical type T
thermocouple.
[0045] Referring to FIG. 2B, microcontroller module 5 may include a
microcontroller 40, which can be an 8051 type microcontroller that
may include 2 kilobytes of internal RAM, 32 kilobytes of internal
nonvolatile flash memory, at least three analog-to-digital (A/D)
converter channels, and at least two internal digital-to-analog
converter (D/A) channels. A crystal 40A may be connected to provide
a reference clock to an oscillator in microcontroller 40.
Microcontroller 40 may be powered by a +3.3 volt supply voltage
that may be produced by a power supply circuit (not shown) that in
turn may be powered by supply voltage conductor 17 of FIG. 1B. The
-12 volt supply voltage on conductor 16 may provide power for
various analog circuitry. One of the D/A outputs of microcontroller
40 may be connected to RF control conductor 25. Another D/A output
may be connected by conductor 41 to an input of a multiplexer 49
and to an input of the V/F converter 48. An A/D input of
microcontroller 40 may be connected by conductor 47 to an output of
an instrumentation amplifier (IA) 46. Another A/D input of
microcontroller 40 may be connected to receive the RF feedback
signal 35 from filter 23 in FIG. 2A. An I/O output of
microcontroller 40 may be connected by conductor 44 to an input of
a level shift circuit 45, the output of which may be connected to
RF enable conductor 26. The RF enable conductor 26 also may be
connected to an input of microcontroller 40.
[0046] Microcontroller 40 can run at approximately 24 MHz. It may
have an internal watchdog timer (not shown) that may reset
microcontroller 40 and may turn everything off if it is not
accessed within a certain time. A redundant external watchdog timer
43 may also reset microcontroller 40 if watchdog timer 43 is not
written to for a defined time, e.g., few tenths of a second. The
internal and external watchdog timers may be powered by different
power supply circuits (not shown) so that no single failure can
interfere with their safety function. Microcontroller 40 may have
eight A/D and two D/A terminals. One of the D/A outputs may be
connected to the RF control conductor 25. That allow
microcontroller 40 to set the level of the output 27 of the RF
oscillator circuitry 18.
[0047] The scaled RF feedback signal 24 may be provided to
linearize the RF output and thereby improve controller accuracy and
reduce ramp-up time without temperature overshoot. RF feedback
signal 35 may be applied to an A/D input of microcontroller 40,
which may allow the microcontroller to determine whether a
requested RF output voltage is achieved. The RF feedback signal 35
may be used by the microcontroller to reduce temperature overshoot
and to provide safety features. If an abnormal condition, such as a
short circuit across the probe electrodes or a failure in the RF
oscillator occurs, microcontroller 40 can detect it and may
permanently disable the unit to prevent further use. A level
shifter 45 may be provided in series with RF enable conductor 26.
In order to determine if the RF enable signal 26 is functioning
properly, signal 26 may be fed back to an input of microcontroller
40. The purpose of level shifter 45 is to match the signal levels
between microcontroller 40 which may operate at 3.3 V and the RF
oscillator control circuitry which may utilize +5 volt and +8 volt
power supply voltages.
[0048] Referring to FIG. 3, a cold junction offset input of
instrumentation amplifier 46 may be connected to conductor 33 to
receive the cold junction offset signal that may be produced by
cold junction compensation circuit 30 in connector 8. The
differential inputs of instrumentation amplifier 46 may be
connected, respectively, to the conductors 34 which may be coupled
across thermocouple 29 in FIG. 3. Cold junction compensator circuit
30 may be mounted in connector 8, and may be connected by
conductors 32A and 32B to corresponding pins of the connector 8 and
the output of cold junction compensator circuit 30 may be connected
through conductor 33 and a terminal of connector 8 to the special
compensation input terminal of instrumentation amplifier 46. The
instrumentation amplifier in combination with its input filter
circuitry may be a differential amplifier that may provide common
mode rejection for a low voltage thermocouple signal. Most of the
"common mode noise" may come from the RF generator. The output of
instrumentation amplifier 46 may be coupled to two of the A/D
inputs of microcontroller 40. Since the gains of the A/D converter
channels may be different, this may provide a larger dynamic range,
meaning that the low gain A/D channel may cover a larger
temperature range, but may not have very good resolution because
each bit may represent almost 0.1 degrees Celsius. The higher gain
channel may have better resolution (approximately 0.05 degrees
Celsius), but, may have limited temperature range. Together they
may allow a wide temperature range and good resolution in a region
of interest, e.g., near 50 degrees Celsius.
[0049] Either V/F converter 48 or microcontroller 40 can generate
an audible tone signal that may pass through multiplexer 49, audio
amplifier 51, and volume control circuit 52 to speaker 7.
Multiplexer 49 may receive two of its inputs from V/F converter 48,
which may have an input connected to microprocessor output 41. V/F
converter 48 may produce three outputs, which may include a sine
waveform, a square waveform, and a triangle waveform, the first two
of which may be connected to two separate inputs, of multiplexer
49. The third input of multiplexer 49 may be connected to ground so
the sound generator can be turned off when desired. The fourth
input of multiplexer 49 may be connected to D/A output 41 of
microcontroller 40, which may allow preselected or arbitrary sound
waveforms generated by microcontroller 40 to be applied to speaker
7. Since the input of microcontroller 40 may be connected to output
of the compensated instrumentation amplifier output 47 which may
represent the temperature measured by thermocouple 29,
microcontroller 40 may have information to produce an output
voltage at D/A converter 41 so that the pitch of the sound produced
by speaker 7 may be proportional to the temperature of thermocouple
29 and therefore to the temperature of the treatment site being
heated by RF energy from probes 36A and 36B.
[0050] The V/F converter may have internal parameters that set the
output frequency to between about 600 Hz and 3000 Hz. The
availability of sine and square wave shapes may allow
microcontroller 40 to create different sounds to alert the user of
various conditions.
[0051] Referring to FIG. 3, cable 9 may connect some of the
terminals of connector 8 to handset 10. Specifically, the RF output
of filter 23 may be coupled through connector 8 and may become the
center conductor of a coaxial cable that may have a grounded shield
conductor 27A. The center conductor or "hot" conductor 27 of the
coaxial cable may be connected through handset 10 and the body 11A
of applicator 11 to conductive probe 36A of applicator 11. The
shielded conductor 27A of the coaxial cable may be connected to the
other conductive probe 36B. Thermocouple 29 may be located in probe
36A, and may have its two conductors coupled to the above-mentioned
pair of conductors 34, which may extend through cable 9 to
connector 8 and to the differential input terminals of
instrumentation amplifier 46 of FIG. 2B.
[0052] A momentary switch 58 in handset 10, which may be utilized
to start a hyperthermia treatment, and also may be used by the
operator to halt the hyperthermia treatment after the desired
treatment time interval has elapsed, may be connected to conductors
58A and 58B which may extend through connector 8 to microcontroller
40. A light emitting diode 59 on handset 10 may be similarly
connected by conductors 59A and 59B which may extend through
connector 8 to microcontroller 40 and its output buffer. LED 59 may
be used to indicate the start of the treatment and to provide a
visual indication of the elapsed time by blinking at same
predefined frequency, e.g., every two seconds.
[0053] Note that thermocouple 29 may be mounted in the same probe
36A that may be connected to the hot conductor 27, in order to
ensure that the temperature may be properly sensed even if the
ground electrode may not be firmly in contact with the skin. It has
been observed that heating of the treatment site can occur, under
certain conditions, even if probe 36B is not in direct contact with
the tissue being treated. This means that thermocouple 29 should be
mounted in probe 36A. It should be understood that there may always
be some capacitive coupling to the skin even if the ground
electrode is not firmly in contact with the tissue. This may allow
heating to take place without accurately sensing the temperature if
the thermocouple was located in the ground electrode. Such heating
does not occur if the high-voltage electrode is in poor contact
with the skin because the capacitive coupling may be much
lower.
[0054] Referring to FIG. 2A, the RF circuitry within dashed line 18
may be electrically shielded to prevent EMI (electromagnetic
interference). This RF circuitry is shown in detail in FIG. 4 and
may include a conventional 6.78 MHz crystal oscillator 19 that may
produce a square wave output applied to the input of an integrating
circuit 69. Integrating circuit 69 may produce a sawtooth waveform
which may be applied to the positive input of a comparator 67 that
may compare the sawtooth waveform to a reference voltage applied to
the negative input of comparator 67 by means of a conductor 66. The
output of comparator 67 may be a pulse signal and, the width of
each pulse thereof may be determined by a comparison of the
sawtooth waveform with the above-mentioned reference voltage on
conductor 66. The portion of FIG. 4 other than power oscillator and
RF output transformer circuit 71 and filter 23 is the RF modulator
21 of FIG. 2B. The resulting duty-cycle-modulated RF signal on
conductor 70 may be applied as an input to a conventional RF power
oscillator circuit 71 which may produce an output 72 that may be
filtered by filter circuit 23 to produce a sinusoidal waveform. RF
enable conductor 26 may be connected to an input of power
oscillator circuit 71. Power oscillator circuit 71 may include an
RF output transformer, the secondary winding of which may be
connected to conductor 72. Filter circuit 23 may produce a 6.78 MHZ
RF signal RFOUT proportional to the value of the RF Control signal
25.
[0055] An RF feedback signal 35 may be produced by filter 23 and
may be divided by a divider circuit 73 to produce the
above-mentioned scaled RF feedback signal 24. Filter 23 may be a
standard R/C filter/divider following a rectifier that may convert
the RF signal to a DC signal. After the filter, the signal may be a
scaled RF feedback signal 24 that may be applied through a resistor
65 to the negative input of an operational amplifier 62 and to one
terminal of a feedback capacitor 63, the other terminal of which
may be connected to the output of operational amplifier 62. The
output of operational amplifier 62 also may be connected to one
terminal of resistor 64, the other terminal of which may be
connected by conductor 66 to the negative input of comparator 67 to
provide the above mentioned reference voltage. The reference
voltage on conductor 66 also may be limited by a clamp circuit 68.
The positive input of operational amplifier 62 may be coupled by
resistor 61 to RF control signal 25 in order to set the desired
temperature at which the abnormal tissue may be maintained during
the treatment operation. The RF enable signal 26 may be driven by
microcontroller 40 through a level shifting circuit 45 shown in
FIG. 2B.
[0056] The operator can perform an independent temperature
verification by putting the hyperthermia treatment device 1 into an
"operate" mode, in which case the readout 2C may indicate the
present room temperature. The readout may always read the
temperature of the applicator electrode. This may be true before
and after treatment. This continuous display is intended as an
additional safety feature that may allow the operator to determine
if the system is behaving properly.
[0057] During a treatment the self-test algorithm that may be
executed by microcontroller 40 may require that during a first
period, e.g., a first four second interval, there must be an
increase of a predetermined amount, e.g., 0.4 degrees Celsius of
thermocouple 29 from a previously measured temperature. To
accomplish this, the self-test program may continue to acquire a
sequence of "local minimum temperatures" and require that there be
at least a 0.4 degree Celsius rise in the temperature of
thermocouple 29 from at least one of the local minimum temperatures
acquired during the first four second interval. The self-test
algorithm may require that there be an increase of at least 0.4
degrees Celsius from the lowest accumulated local minimum
temperature during the first four seconds to verify that
thermocouple 29 is operating correctly. The hyperthermia treatment
may be terminated if either 1) the thermocouple temperature does
not undergo a temperature increase of at least 0.4 degrees Celsius
during the first four seconds of the self-test procedure, or 2) the
thermocouple temperature does not rise above the initial
thermocouple temperature by the end of the first eight seconds of
the self-test procedure. Also, the above algorithm may detect a
malfunction of thermocouple 29 even if it occurs during a
hyperthermia treatment cycle. The program may conclude that
thermocouple 29 is malfunctioning if either or both requirements
are not met.
[0058] If the present cycle of the hyperthermia treatment process
has just been completed on the first portion of a large lesion, and
a second cycle of the hyperthermia treatment process is about to
begin on a second portion of the lesion that slightly overlaps the
first portion, the tissue may already be quite warm from the first
treatment cycle. It is desirable to know whether a temperature drop
of thermocouple 29 after the beginning of the second cycle is a
normal temperature decrease due to a high initial temperature
caused by RF heating from the first cycle or whether the
thermocouple is malfunctioning after the RF probes have been moved
to a new tissue area. By looking at the change in the rate of
change of the temperature before and after the RF oscillator is
enabled, microcontroller 40 can determine if the high temperature
start is a result of an overlap procedure or a malfunctioning
thermocouple. The algorithm may require an absolute temperature
change of at least 0.4 degrees Celsius during the first 4 seconds
of the treatment or a relative change of 1 degree Celsius during
the first 8 seconds.
[0059] The self-test algorithm and the temperature control
algorithm may be executed by microcontroller 40 to prevent
hyperthermia treatment system 1 from applying RF energy to a
treatment site below 20 degrees Celsius mainly as a test to detect
any flaw in thermocouple 29 or a malfunction of temperature
compensation circuit 30.
[0060] Having the start temperature above a predefined minimum
temperature, e.g., 20 degrees Celsius may allow detection of a
malfunctioning thermocouple and/or a malfunctioning cold junction
compensation circuit. A thermocouple is a metal-metal junction
which may generate a small magnitude open circuit voltage signal
(e.g., tens to hundreds of millivolts) that may be generally
proportional to temperature and can be measured by a bridge circuit
or an instrumentation amplifier. The cold junction in the
above-described system may be located in the connector 8, which is
why the cold junction compensation circuit may also be located
therein, and it may require a cold junction compensation circuit,
because the cold junction produces another voltage that may tend to
offset the voltage produced by thermocouple 29 and therefore may
produce a temperature measurement error. Cold junction compensation
circuit 30 may produce an offset voltage that may be proportional
to the cold junction voltage and may compensate it by providing an
offset signal to the instrumentation amplifier that may be used to
measure the voltage produced by thermocouple 29, and thereby may
avoid an error, e.g., 25 degrees Celsius, in the room temperature
reading. A start temperature above 20 degrees Celsius may allow
easy determination as to whether there is a shorted thermocouple or
a defective cold junction compensation circuit. If either occurs,
the temperature may read near a minimum value, e.g., approximately
10 degrees Celsius. If the thermocouple is defective (open), the
temperature signal from the thermocouple may approximate a maximum
temperature value, e.g., approximately 65 degrees Celsius.
[0061] The self-test algorithm may also determine whether the
temperature of thermocouple 29 attained a selected desired
treatment temperature within a pre-determined time, e.g., 45
seconds, and if this determination is affirmative, the algorithm
may conclude that hyperthermia treatment system 1 is functioning
properly. Hyperthermia treatment system 1 may allow the physician a
predetermined time, e.g., 15 seconds, to begin a next treatment
without retesting the thermocouple 29. This may allow a reasonable
overlap of the present treatment cycle with a previous treatment
cycle, which may be desirable for some procedures.
[0062] To ensure that the system is operating safely, the self-test
algorithm may perform a plurality of independent temperature tests.
Comparator circuitry internal to the microcontroller may be
programmed to permanently shut down the system if the temperature
exceeds a predetermined maximum value, which may be approximately
58 degrees Celsius. The algorithm may also require that after
reaching a desired treatment temperature the unit must remain
within a predetermined temperature window, which may be determined
from a table of values. The table may allow the system to react
faster if the temperature error is large. As an additional safety
measure, a set of comparators external to the microcontroller may
also have the ability to disable the system if the temperature
exceeds a predetermined value, e.g., 58 degrees Celsius. These
external comparators may provide a backup in case the
microcontroller malfunctions. Also, the self-test algorithm may
operate to detect whether: (1) a power supply is out of
specification by reading the value of each power supply using its
internal A/D converter, (2) the timer is working properly as
determined by the internal and external watchdog timers, and/or (3)
the redundant ADC converter inputs match. If any of these or other
suitable determinations are affirmative, microcontroller 40 may
permanently disable hyperthermia treatment system 1 to ensure that
it cannot be used again unless and until it is sent back to the
factory for repair and/or replacement.
[0063] Initially, after waiting for oscillator 19 to start up, the
system may perform a self test operation (which actually may be
repeated at some predetermined interval, e.g., approximately every
50 milliseconds), during which everything may be held inactive
until it may be determined that the microcontroller oscillator
started properly. If the RF circuitry 18 does not start up properly
within a predetermined time, e.g., 1.5 seconds, the unit may be set
into a permanently disabled mode and returned to the factory for
repair or replacement.
[0064] The hyperthermia treatment system I may have a plurality of
states. A first state may be "normal operation", a second state may
be for "treatment operation" or "standby operation" and a third
state may be "abnormal operation," which may include a first
condition that may require stopping a current hyperthermia
treatment, and a second condition that may require that
hyperthermia treatment system I be set to a disabled state and
returned to the factory before it can be used again for
hyperthermia treatment. Hyperthermia treatment system 1 may be
disabled and returned to the factory whenever a condition is
detected which could result in a risk to a patient, irrespective of
whether hyperthermia treatment system 1 might be operational if it
is turned off and then powered up again.
[0065] The self-test operations may include testing power supply
voltages, doing A/D converter input comparisons and D/A converter
output comparisons, one against the other, to determine if they are
working properly, determining if the oscillators 19 and 40A are
operating properly, determining if their frequency ratio is
approximately correct to establish whether either is substantially
off frequency, and testing some I/O bits, which may include the RF
enable. Some or all of the self-test operations may be performed on
a continuous basis over some predetermined interval (in this case
every 50 milliseconds), and if any critical self-test fails more
than a predefined limit, e.g., three times in a row, then
hyperthermia treatment system 1 may be set in the "disable and
return to factory" mode. The present treatment may be terminated if
any self-test operation fails only once. The setting of treatment
temperature selection knob 2B may be read, any "off" transition of
the power on-off switch may be detected, and the battery test may
be determined, all by microcontroller 40.
[0066] Microcontroller 40 may also set the state of the 30/60/90
second LEDs 2E, which may be used primarily to indicate battery
charge level and elapsed treatment time, but may also be used for
diagnostic purposes. During a battery test, the 30/60/90 second
LEDs not only may indicate the percentage of battery charge
remaining, they may also indicate the approximate number of
remaining treatments that can be performed with the remaining
battery charge, because the fully charged battery may be capable of
powering hyperthermia treatment system 1 for approximately 100
hyperthermia treatments. In the "treatment timing mode" the LEDs 2E
may indicate to the physician the elapsed treatment time, e.g., 30
seconds, 60 seconds, or 90 seconds, so that the physician can
terminate the present treatment by depressing momentary switch 58
of handset 10 at the time they determine to be appropriate.
[0067] Hyperthermia treatment system 1 may begin operation at
reduced power. The reason for this is that there may be a long lag
between the time at which the treatment site is heated up to the
desired treatment temperature by the applied RF energy and the time
at which thermocouple 29 actually detects the heating. The
treatment site could be burned before the correct temperature could
be determined from the thermocouple if hyperthermia treatment
system 1 were to be started at full power. By starting the
temperature ramp-up procedure at a predetermined reduced power
level, e.g., about 30 percent, of the maximum RF output voltage on
conductor 27 and ramping to 100 percent (if required) may allow the
treatment temperature to be achieved within a predetermined period,
e.g., approximately 20 seconds. This may be achieved by using a PID
loop algorithm that may generate the RF control signal by summing
the integral gain, a derivative gain, and proportional gain. Other
parameters may be used which are not typically used in PID loops.
One may be that the selected treatment temperature, plus or minus a
predetermined temperature, e.g., one degree Celsius, must be
attained within a predetermined time, e.g., 45 seconds, and if more
time is required to ramp up to the selected temperature, the
treatment may be automatically terminated. Typical ramp up times
may be approximately 20 seconds.
[0068] PID loop software, as represented in the
subsequently-described flowchart, may determine the error between
the desired treatment temperature and the actual temperature of the
treatment site, and may multiply that difference by the
proportional gain term in order to obtain a proportional gain
value. Specifically, the PID loop integrate the difference over
time, and then multiply that by the integral gain term to obtain an
integral value. The PID loop may determine the derivative of that
difference and multiply it by the differential gain term to obtain
the differential gain value, and then may sum all three together
and output that value to the RF control signal 25 through a D/A
converter of microcontroller 40. With integral gain, if the
preselected temperature is not being achieved, i.e., the overall
system does not have enough gain, the integral gain may be
increased in accordance with the amount of time required to achieve
the preselected temperature. The integral gain may force the RF
output signal to the value needed regardless of the value of the
proportional gain. The opposite condition can occur when the load,
i.e., the treatment site, absorbs too much RF power too quickly and
the treatment site heats too rapidly. In this case, the derivative
term may determine how quickly the actual treatment site
temperature approaches the preselected treatment temperature, and
if that is occurring too rapidly, the derivative term may cause the
amount of RF energy applied to the treatment site to be reduced, or
cause the amount of RF energy applied to the treatment site to be
increased if the actual temperature of the treatment site
approaches the preselected desired treatment temperature too
slowly.
[0069] Testing of the described embodiment of the invention
indicates that thermocouple 29 measures treatment site temperature
overshoot of less than one degree Celsius under all conditions with
all available applicators and that the temperature ramp-up time of
the treatment site occurs within about 20-22 seconds.
[0070] If the thermocouple temperature begins to drift outside of
the plus/minus 1 degree Celsius range, a sliding scale may be used
to determine how soon to terminate a treatment. If the temperature
varies by more than a predetermined amount from a predetermined set
point for more than a predetermined amount of time, the proper
thermal dose will not be provided, and the system may alert the
doctor by terminating the treatment early and making an "abnormal
termination" audible sound. The sliding scale may be determined by
a time/temperature matrix, which may be programmed into the
microcontroller. In this embodiment, if the actual treatment site
temperature is more than a predefined amount, e.g., one degree
Celsius, below the preselected treatment temperature, it has to
remain more than one degree Celsius below the preselected treatment
temperature more than a predefined period of time, e.g., 16
seconds, before the present treatment may be terminated. If the
actual treatment site temperature is more than two degrees Celsius
below the preselected treatment temperature, it has to remain more
than a predetermined amount, e.g., two degrees Celsius, below the
preselected treatment temperature for at least eight seconds before
the present treatment may be terminated.
[0071] Hyperthermia treatment system 1 may be set in the
return-to-factory mode if a hardware malfunction is detected.
Usually the problem that causes a treatment to be terminated is
that the temperature doesn't ramp up properly, for example, because
of dry skin or improper probe contact. Since the effectiveness of
hyperthermia treatment may drop by a factor of two for every one
degree Celsius reduction in temperature, failure of the abnormal
tissue to reach the preselected treatment temperature may result in
ineffective treatment.
[0072] The present device may be fully digitally controlled, which
may improve system accuracy and control.
[0073] System 1 may employ methods to control the applied
temperature with minimum overshoot and to improve safety by
detecting any defective temperature sensor in the applicator. Such
method may minimize overshoot by compensating for the short-term
temperature difference between the area of the body being treated
and the applicator delivering the RF energy. The RF energy may heat
the treatment site and then the treatment site may transfer heat to
the applicator sensor. Time lag between heating and sensing may
contribute to temperature overshoot.
[0074] Another cause of overshoot may be that different applicator
sizes and shapes heat treatment sites at different rates and to
different depths. Methods employed by system 1 may adapt to the
various applicator sizes and shapes by modifying the control loop
coefficients based on the initial probe response. This may improve
temperature control accuracy and further reduce temperature
overshoot.
[0075] The algorithm may also use the initial probe response to
detect a defective temperature sensor by comparing the rate of
change in temperature before and after power is applied. A shorted
thermocouple sensor, for example, can report the temperature of the
cold junction compensation circuit that may be approximately at
room temperature. Undetected, this could lead to over treatment or
burning of the tissue being treated. The problem may be complicated
by the fact that at various times in a treatment the temperature
sensor can legitimately report any value between room temperature
and the selected temperature because it could be cooling down from
a previous treatment. By looking for changes in the rate of change
of temperature before and after power is applied a defective sensor
can be detected under a very wide range of conditions without false
positives.
[0076] Referring to FIGS. 5A and 5B, the program in microcontroller
40 may initialize the hardware and firmware in block 74 and perform
a self testing operation in block 75. Block 76 may represent a
routine that can be utilized to perform debugging and interactive
set-up operations. In decision block 77, the program may determine
whether momentary switch 58 has been pressed, and if that
determination is affirmative, the program may determine if there
has been a previous hyperthermia treatment within a predetermined
time period, e.g., the past 15 seconds. If this determination is
negative, the program may operate to maintain the treatment site at
the selected treatment temperature, as indicated in block 81. The
operation implemented by decision block 78 may allow convenient
treatment of overlapping regions of the abnormal tissue without
starting over and performing a new ramp-up operation.
[0077] If the present treatment is considered to be an initial
treatment, then the program may go to block 79 and execute a
routine to ramp the power from an initial value up to the selected
treatment value, as previously described. In decision block 80, the
program may determine if the thermocouple is at the selected
treatment temperature, and if this determination is affirmative the
ramp-up operation may be completed, and in the routine of block 81,
the program may operate to maintain the thermocouple at the
selected treatment temperature. If the decision of block 80 is
negative, the ramp-up operation of block 79 may continue. In
decision block 82, the program may determine if the present
hyperthermia treatment is complete, and if it is not, the program
may continue to maintain the thermocouple and the treatment site at
the selected treatment temperature, but otherwise the program may
return to decision block 77 and await a new signal from momentary
switch 58.
[0078] During the operation indicated in FIG. 5A, microprocessor
may repeatedly execute the routine shown in FIG. 5B to perform
concurrent error checking and data recording operations. In FIG.
5B, if any of the conditions indicated in blocks 83-92 is met, the
present treatment may fail. Some of the aforementioned blocks,
namely, blocks 83-85, 88and 89, may indicate failures from which
the hyperthermia treatment system 1 cannot recover without repair
from the manufacturer. If the conditions indicated in any of these
particular blocks occur, the operation of hyperthermia treatment
system 1 may be "permanently" disabled until it has been reset by
qualified repair personnel.
[0079] Referring to FIG. 6A, the system initially may be in a reset
state, and the first step, in block 100 may be to execute a
hardware initialization routine which may (include initializing
registers, setting input/output buffer data directions, setting A/D
converter gains, etc.), and then set up operating variables as
indicated in block 101. The next step may be to read various
variables and status information from the EEPROM, as indicated in
block 102. Decision block 4 may allow a determination to be made as
to whether to execute a debug routine (not described) indicated in
block 105. If no debug routine is to be executed, decision block
106 may determine whether the power to hyperthermia treatment
system 1 should continue to be on, and if it is, the program may
execute a normal shutdown as indicated in block 107 in response to
actuation of the power switch.
[0080] Decision block 108 may determine if a timer has timed out,
and if that decision is negative, the program may reenter decision
block 104. This may allow hyperthermia treatment system 1 to
automatically turn itself off if no activity occurs for a
predetermined period, e.g., 15 minute interval. If the timer of
decision block 108 has timed out, the program may update the
watchdog timer, as indicated in block 109. This may occur at some
predefined interval, e.g., approximately every second.
[0081] The program may then operate to check the power supplies in
hyperthermia treatment system 1 and make a decision in block 110 to
execute a failure shutdown as indicated in block 111 if the power
supplies are not functioning properly, and otherwise may go to
decision block 112. A failure shutdown may result in disabling
hyperthermia treatment system 1 until it has been repaired by the
factory or by authorized personnel. Next, the program may determine
in decision block 112 if the RF circuitry is functioning properly,
and hyperthermia treatment system 1 may undergo a failure shutdown
if the determination is negative. Otherwise, the program may go to
decision block 113 and determine if the thermocouple indicates a
thermocouple temperature greater than a predetermined number of
degrees Celsius above the selected treatment temperature. If there
is such an over-temperature condition, the program may set an
"error stop" condition as indicated in block 114 and cause a
specific pattern of the status LEDs 2E (FIG. 1A) to indicate the
over-temperature state. If the determination of decision block 113
is negative, the program may go to decision block 116 and check for
the existence of a number of predetermined abnormal conditions. If
any of them are found, the program may set status LEDs 2E to a
corresponding warning pattern, as indicated in block 117. The
program may then go to decision block 118 and check to determine if
the battery output voltage is low, and if it is, may execute a
subroutine that sets the LED status lights 2E to a corresponding
warning pattern and then may go to program entry point or label
121. If the battery voltage is not low, the program may set the
status lights pattern to indicate acceptable battery voltage as
indicated in block 120, and then may go to entry point 121.
[0082] The program may then go to decision block 122 of FIG. 6B.
Decision block 122 may determine which state of a plurality of
possible states (e.g., switch open, switch closed, or "bad state")
momentary switch 58 is presently in, and may determine an "on" code
in a register if momentary switch 58 is open, an "off" code if
momentary switch 58 is closed, and any other code in the register
may be considered to be a "bad state" code.
[0083] As mentioned above, decision block 122 may be a multistate
conditional test that may determine which one of several conditions
momentary switch 58 is in. "Button open" and "button closed" may be
variables stored in a register, and a "bad state" may represent a
possibly corrupted value in the register and may be any possible
value in the register other than the two permitted states
representing "button open" and "button closed". This may represent
a fatal condition, which may necessitate disabling the system.
[0084] If the "button open" state is detected by decision block
122, the program may go to decision block 123 and, if momentary
switch 58 is closed, detects a "button closed" condition as the
result of a transition from the button open condition to the button
closed condition, and then goes to block 125 and sets the button
state as closed, and then goes to decision block 126. If a button
closed condition is not detected in decision block 123, the program
goes to FIG. 6C via entry point 124.
[0085] Decision block 126 of FIG. 6B may determines if
microcontroller 40 is in an idle state, and if it is not, the
program may determine in decision block 135 if the program is in a
ramp-up state, and if that determination is negative, the program
may go to decision block 137 and determine if hyperthermia
treatment system 1 is in a treatment mode. If the program is
determined in decision block 126 to be in an idle mode, the program
may go to decision block 127 and check the battery voltage. If the
battery voltage is low, the program may go to block 128 and set the
system state to an "error stop" state and then go via entry point
124 to FIG. 6C. If the battery voltage is not low, the program may
go to decision block 129 and determine if the thermocouple
temperature is at an excessively high temperature, and if this
determination is positive, the program may go to block 128 and set
the system state to an error stop condition to terminate the
present treatment (but may not permanently disable hyperthermia
treatment system). If the determination of block 129 is negative,
the program may go to decision block 130 and determine if the
selected treatment temperature is within a proper predetermined
range, and may generate a "record error" as indicated by block 131
if the selected treatment temperature is out of the proper range,
and otherwise may go to block 132 and set various control
information to default values, and may also initialize various
control variables to suitable pre-ramp state values and set the
system state to "SS=PRE-RAMP" in block 133, and then, in block 134,
may record information for subsequent debugging processes, in order
to provide a record of the error or abnormal condition. The
conditions associated with blocks 127 through 134 may be associated
with conditions which may need to be recorded to aid subsequent
debugging.
[0086] If hyperthermia treatment system 1 is not in an idle state,
then the program may determine if it is in the ramp-up state, as
indicated in decision block 135. If the determination of decision
block 135 is affirmative, the program may go to block 136 and may
set the system state to a stop condition in order to stop an
abandoned ramp-up and may record information of the abandoned
ramp-up, and then may go to entry point 124. If the determination
of decision block 135 is negative, the program may go to decision
block 137 and may determine if hyperthermia treatment system 1 is
in the treatment mode, in which case the program may go to block
138, may record the treatment information and may set the system
state to a stop condition to stop a treatment mode, and may then go
to FIG. 6C via entry point 124. If the determination of decision
block 137 is negative, the program may go directly to entry point
124.
[0087] If the "button closed" state is detected in decision block
122, the program may go to decision block 139 and, if momentary
switch 58 is open, may detect a "button open" condition as the
result of a transition from the button closed condition to the
button open condition, and may go to block 140 and may set the
button state as open, and may then go to entry point 124.
[0088] If the state produced by decision block 122 is that the
button state register is invalid, then the program may generate a
failure shutdown condition, as indicated in block 111A.
[0089] Referring to FIG. 6C, in block 150 the program may look at
how long a temperature change difference between the present
thermocouple temperature and a previous thermocouple temperature
has existed, because it is a parameter that may be used in the PID
loop. The program may look for a rate of change of thermocouple
temperature, and to this end, the program may store a particular
number of samples of thermocouple temperature and discard the
oldest sample and add the newest one and then take a new average of
the stored samples. A time-weighted average may be performed on the
temperature difference values, and in block 151, the program may
compute a new temperature difference which may be the difference
between the last time-weighted average and the present
time-weighted average, by excluding the oldest of, for example, 10
measurements being averaged and including the newest measure of
temperature difference. From that point, a series of tests may be
performed. In decision block 152, the program may determine if the
battery voltage is too low for a proper hyperthermia treatment, and
if it is, the program may execute a normal shutdown operation, as
indicated in block 107. Otherwise, the program may go to decision
block 153 and determine if the battery voltage is low but is
nevertheless high enough to allow a proper hyperthermia treatment
to be performed, and if this decision is affirmative, the program
may go to block 154 and count the number of times this condition
has been detected (to, for example, ensure that the battery has not
failed in the sense of having a single defective cell therein and
to ensure that information may be retained for subsequent
diagnostic purposes). In decision block 155, the program may
compute the thermocouple temperature as measured by two of the A/D
converters in microcontroller 40, which may include one with high
gain in another with low gain, one having a large temperature range
and low resolution and another having a small temperature range
with high resolution. If the two temperature measurements are not
essentially the same, then the program may go to block 156 and
record that information for future diagnostic purposes, to indicate
that one of the A/D converter channels may be defective, and also
may shut hyperthermia treating unit 1 down. In any case, the
program may then go to block 157 and test the power supplies and
suitably records the values for use elsewhere in the program (block
110 of FIG. 6A). If the power supplies are properly functional, the
program may go to decision block 158 and test the output of the RF
circuitry for improper RF output levels, and if an improper RF
output level exists, the program may execute a failure shutdown, as
indicated in block 111. Otherwise, program may go to decision block
159 and determine if there is an RF short condition. If there is,
the program may go to block 160 and set the system state to an
error stop condition, and may then go to entry point 161. The
program cannot detect an RF runaway condition or an RF shorted
condition, if the program is in a stop condition or an idle
condition. The determinations of decision blocks 158 and 159 only
apply if the program is not in a stop condition or an idle
condition. The term "RF runaway condition" means a condition in
which the value of the output of the RF circuitry is significantly
different than the value "requested" by the previously described
feedback circuitry.
[0090] The program then may go to FIG. 6D and enter decision block
162, which may generate one or more codes representing a pre-ramp
mode, a ramp mode, a treatment mode, a stop mode, an error stop
mode, or a default mode. Decision block 162 represents a
multi-state conditional test feature that may determine which of a
plurality of conditions hyperthermia treatment unit 1 is in and may
generate corresponding codes, one of the plurality of conditions
being a default condition which may be represented by a code other
than any of the codes representing other conditions. The system may
be set to an idle condition if there is a default code which is any
code other than the codes representing a first group of conditions
shown in FIG. 6D. If the system is in the pre-ramp mode, it may
determine if the thermocouple is at a suitable starting
temperature, wherein decision block 163 may determine whether the
temperature is greater than a predefined value, e.g., 20 degrees
Celsius, and if this determination is negative, the program may go
to decision block 164 and determine if the thermocouple temperature
is less than 20 degrees Celsius for more than a predetermined time,
e.g., 4 seconds, and if so, then an error stop condition may be
created as indicated in block 165, and the program then may go back
to entry point 103 of FIG. 6A. A negative determination of decision
block 164 may result in the program returning via entry point 103
to FIG. 6A. If the determination of decision block 163 is
affirmative, the program may enter the ramp-up subroutine of FIG.
6E via entry point 166.
[0091] If conditional test decision block 162 determines that
hyperthermia treatment system 1 is in the ramp mode, the program
may go via entry point 166 to execute the temperature ramp-up
procedure shown in detail in FIG. 6E, and represented by bock 166A
in FIG. 6D. If conditional test decision block 162 determines that
hyperthermia treatment system 1 is in the treatment mode, the
program may execute the subroutine for executing the treatment
temperature maintaining procedure shown in detail in the subroutine
of FIG. 6F and also represented in FIG. 6D by block 167A.
[0092] If conditional test decision block 162 detects a stop
condition, then the program may enter block 168 and set the system
to an idle condition, and may also cause speaker 7 to emit a
"nominal termination tone" or beeping sound, and then return to
FIG. 6A via entry point 103. If conditional test decision block 162
determines that the system is in an error stop condition, the
program may reset the system to an off condition as indicated in
block 170, and may cause speaker 7 to emit and "abnormal
termination tone" as indicated in block 171, and then return to
FIG. 6A by way of entry point 103.
[0093] Referring to FIG. 6E, a plurality of tests may be performed
before beginning the actual temperature ramp-up routine. In block
173 the program may determine if the battery voltage is too low to
allow the temperature ramp-up procedure to begin, and if this
determination is affirmative, the program may go to block 174 and
change the system state to an error stop condition, turn off the
various controls, update the status information for subsequent
debugging, and then return to FIG. 6A via entry point 103. If the
battery voltage is not too low to allow the temperature ramp-up
procedure to begin, the program may go to decision block 175 and
determine whether the start up thermocouple temperature was greater
than or equal to a predetermined value, e.g., 20 degrees Celsius,
and also now is less than a predetermined value, e.g., 10 degrees
Celsius. If the determination of block 175 is affirmative, the
program may go to block 176, set the system state to an error stop
condition, turn off appropriate controls, update the debugging
status information, and then may go to entry point 103 of FIG. 6A.
This test may provide an indication of a possible failure of the
thermocouple or an oscillator. If the determination of decision
block 175 is negative, the program may begin the temperature
ramp-up procedure by determining if the thermocouple temperature is
at the selected treatment temperature value, in decision block 177.
If this determination is affirmative, the program may go to FIG. 6F
via entry point 167 in order to run the PID loop. If the
thermocouple temperature is not at the selected treatment
temperature, then the program may go to decision block 178 and
determine if a predefined maximum ramp time, e.g., of 45 seconds,
has been exceeded. If this determination is affirmative, the
program may go to block 179 and set the system state to an error
stop condition, turn off appropriate controls, update the status
information, and go to FIG. 6A via entry point 103. If the maximum
ramp time has not been exceeded, then the program may go to
decision block 180 and determine if the thermocouple temperature
has been ramping upward for a predetermined time, e.g., at least 1
second. If this determination is affirmative, the program may go to
block 184 and record the present 1-second temperature difference
and then go to FIG. 6F to run the PID loop. If the thermocouple
temperature has not been ramping up for a predefined time, e.g., 1
second, the program may go to decision block 181 and determine
whether both a previous treatment has been performed and the
present ramp time is greater than a predefined time, e.g., 4
seconds. If that is the case, the program may go to block 182 and
calculate the various proportional, integral, and differential PID
loop variables to thereby update them and then go to decision block
183 and determine if the changes in PID loop variables are less
than expected for a predefined time, e.g., 4 second interval. If
this determination is affirmative, the program may go to block 186,
set the system state to an error stop condition, turn off
appropriate controls, and update the debug status information, and
then return to FIG. 6A via entry point 103. This portion of the
program may determine whether the thermocouple or the RF generator
circuitry is defective, by determining if the thermocouple
temperature fails to increase during the ramping operation by at
least a certain amount of temperature change within a certain
amount of time. If the determination of decision block 181 is
negative, the program may then go to FIG. 6F via entry point 167 to
run the PID loop.
[0094] Referring to FIG. 6F, the program may first go to block 188
and calculate PID loop values to determine what the present loop
gain should be, and then may go to block 189, set the value of the
RF control voltage on conductor 25 (FIG. 4), and record the maximum
peak RF voltage produced, for diagnostic purposes. The program may
then go to decision block 190 to determine if the system is in the
treatment mode. If this determination is negative, the program may
still be in the temperature ramp-up mode, and the program may
return to FIG. 6A via entry point 103. If the treatment mode has
begun, the program may begin a series of tests by going to decision
block 191 and determining if the present treatment time exceeds a
maximum treatment time e.g., 90 seconds . If this determination is
affirmative, the program may go to block 192, set the system state
to an error stop condition, turn off appropriate controls, and
update the status information, and then go to decision block 195.
If the determination of decision block 191 is negative, the program
may go to decision block 193 and determine if a predefined time,
e.g., 2 second interval, has elapsed. If such time has elapsed,
then the program may go to block 184 and produce a beeping tone by
means of speaker 7 and cause the handpiece LED 59 (FIG. 3) to
flash, to indicate elapsing of consecutive 2 second intervals of
treatment time as they occur. In any case, the program may go to
decision block 195 and determine if the thermocouple temperature
has been below the proper temperature for too long. This may be
determined by reference to a stored table of values that determine
how execution of the PID loop should progress, in accordance with
the earlier discussion herein. If the determination of decision
block 195 is affirmative, the program may go to block 196, set the
system state to an error stop condition, turn off appropriate
controls, update the debugging status information, and then return
to FIG. 6A via entry point 103. Otherwise, the program may go to
decision block 197 and determine if the thermocouple temperature
may be above a maximum permissible temperature, e.g., 58 degree
Celsius, and if this determination is affirmative, program may go
to block 198 and set the system state to an error stop condition,
turn off appropriate controls, update debugging status information,
and return to FIG. 6A. Otherwise, the program may go to block 199
and calculate the integral PID terms, meaning that the integral
term may be incremented every time the PID loop is executed,
wherein the integral term may force the loop gain to appropriately
increase as long as the thermocouple temperature is below the
selected treatment temperature.
[0095] While the invention has been described with reference to
several particular embodiments thereof, those skilled in the art
will be able to make the various modifications to the described
embodiments of the invention without departing from its true spirit
and scope. It is intended that all elements or steps which are
insubstantially different from those recited in the claims but
perform substantially the same functions, respectively, in
substantially the same way to achieve the same result as what is
claimed are within the scope of the invention. For example, the
thermal sensor 29 may not have to be located in either of probes
36A and 36B, and instead could be attached to the applicator 11 in
some other fashion so as to thermally contact the treatment site.
Also, the oscillator circuitry 19,69 could be included within the
RF modulator 21.
[0096] Other embodiments of the invention will be apparent to those
skilled in the art from consideration of the specification and
practice of the invention disclosed herein. It is intended that the
specification and examples be considered as exemplary only, with a
true scope and spirit of the invention being indicated by the
following claims.
* * * * *