U.S. patent application number 11/840732 was filed with the patent office on 2007-12-06 for computerized electrical signal generator.
This patent application is currently assigned to BAYLIS MEDICAL COMPANY INC.. Invention is credited to Frank Headley BAYLIS, Krishan SHAH.
Application Number | 20070282321 11/840732 |
Document ID | / |
Family ID | 38373951 |
Filed Date | 2007-12-06 |
United States Patent
Application |
20070282321 |
Kind Code |
A1 |
SHAH; Krishan ; et
al. |
December 6, 2007 |
COMPUTERIZED ELECTRICAL SIGNAL GENERATOR
Abstract
The invention relates to a medical probe signal generator. More
particularly, it relates to a medical probe signal generator
architecture. The present invention further relates to a system
including a medical probe signal generator having an automatic
probe type detector for detecting an identifier and at least one
instrument cable comprising the identifier.
Inventors: |
SHAH; Krishan; (Mississauga,
CA) ; BAYLIS; Frank Headley; (Beaconsfield,
CA) |
Correspondence
Address: |
DIMOCK STRATTON LLP
20 QUEEN STREET WEST SUITE 3202, BOX 102
TORONTO
ON
M5H 3R3
CA
|
Assignee: |
BAYLIS MEDICAL COMPANY INC.
5253 Decarie Boulevard, Suite 540
Montreal
CA
H3W 3C3
|
Family ID: |
38373951 |
Appl. No.: |
11/840732 |
Filed: |
August 17, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10122413 |
Apr 16, 2002 |
7258688 |
|
|
11840732 |
Aug 17, 2007 |
|
|
|
Current U.S.
Class: |
606/34 |
Current CPC
Class: |
A61B 18/1206 20130101;
A61B 90/98 20160201; A61B 2018/00702 20130101; A61B 2018/00988
20130101; A61B 2018/00791 20130101; A61B 2018/00875 20130101 |
Class at
Publication: |
606/034 |
International
Class: |
A61B 18/18 20060101
A61B018/18 |
Claims
1. An energy delivery system for delivering energy to a patient's
body via at least one medical instrument of a plurality of
different medical instruments, the system comprising: an energy
generator comprising a detector associated with an electrical
connector port of the generator for detecting an identifier from a
plurality of identifiers, the generator adapted to enable functions
relevant to the identifier upon detecting the identifier; and at
least one instrument cable comprising one of the plurality of
identifiers, the cable comprising a first electrical connector for
connection to the connector port of the generator and a second
electrical connector for connection to a connector of the at least
one medical instrument.
2. The energy delivery system as claimed in claim 1, wherein one or
more of the plurality of identifiers is associated with and
connectable to at least two different medical instruments.
3. The energy delivery system as claimed in claim 2, comprising at
least two instrument cables each comprising an identical identifier
of said one or more of the plurality of identifiers, one of said at
least two instrument cables comprising an electrical connector
having a first configuration for connection to one of said at least
two different medical instruments, and another of said at least two
instrument cables comprising an electrical connector having a
second configuration for connection to another medical instrument
of said at least two different medical instruments.
4. The energy delivery system as claimed in claim 1, wherein the
functions relevant to at least one of the plurality of identifiers
are relevant to at least two different medical instruments
connectable to the energy generator.
5. The energy delivery system as claimed in claim 1, comprising at
least two instrument cables each comprising an identical
identifier, one of said at least two instrument cables comprising
an electrical connector having a first configuration for connection
to a first medical instrument, and another of said at least two
instrument cables comprising an electrical connector having a
second configuration for connection to a second medical instrument
different from the first medical instrument.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 10/122,413, filed on Apr. 16, 2002, which is
incorporated herein by reference in its entirety.
FIELD OF THE INVENTION
[0002] The invention relates generally to an energy generator. More
particularly, the invention relates to an apparatus for providing a
controlled source of energy to an application tool, combining
features that customize the utilization to a particular
specialization.
BACKGROUND OF THE INVENTION
[0003] Electrical signal generators are used in a variety of
medical applications. Examples include electrosurgery, tissue
ablation, tissue perforation, neural stimulation, and neural
lesioning. Neural lesion procedures using electrical current with a
high frequency wave, typically in the radiofrequency (RF) spectrum,
have been in use since the early 1950s. Among a variety of
therapeutic purposes, the application of RF in the nervous system
is commonly used in the interventional treatment of pain. The
principle of this application is to intervene in the transmission
of pain signals by altering a function of a nerve structure. This
is accomplished by controlled generation of heat, or, non-thermal
delivery of RF current using an electrode connected to the
generator. Modern RF electrodes not only deliver current but also
include temperature sensors that feedback information to the
controller. And thus, in this situation the energy application tool
is interchangeably referred to as a RF electrode and RF probe. One
of the major advantages of using electrical current for
interventional pain management is that by applying appropriate
frequencies, the current can be used to stimulate nerves adjacent
the electrode to differentiate pain fibers from other neural fibers
and ensure the correct placement of the electrode prior to
intervention.
[0004] Currently, in the field of interventional treatment of
chronic pain the specialist commonly uses three modes of RF
treatment including standard RF, pulsed RF and intradiscal
lesioning. Each of these treatment modes is based on the
application of continuous or pulsed radiofrequency electrical
current to tissue or to an application tool. For some procedures,
prior to applying radiofrequency energy, the target site is
stimulated using stimulation modes to ensure correct placement of
the RF delivery probe.
RF Lesioning Devices--Probes and Cannula
[0005] Probes are medical devices that are designed to act as
patient/energy interfaces for radiofrequency generator systems. The
RF energy applied is usually a 400 to 900 kHz waveform that can be
used for a variety of purposes. In most radiofrequency generators,
the 460-500 kHz waveform is delivered to the body using a probe and
cannula system. A cannula is a hypodermic needle with an insulated
shaft and a bare metal tip called an active tip. It is called an
active tip because once the probe is inserted into the cannula and
the RF is activated, the tip becomes the energy delivery mechanism.
The electrical circuit required to deliver current and voltage is
provided by a return electrode pad that is placed on a flat body
part of the patient, such as his thigh. When the RF energy is
activated at the machine, RF is delivered to the cells surrounding
the active tip surface area. With energy application, the cells
move faster and generate heat. As this heat increases, it is
detected by the temperature measurement device that is located in
the probe.
[0006] Therefore, the mono-polar probe serves two major functions,
it is used for RF energy delivery to the cannula and temperature
monitoring through a thermocouple effect. In some cases, the probes
are not truly heating devices (i.e. resistive elements), but rather
passive energy delivery systems.
Intradiscal Lesioning Devices Probes
[0007] Historically, intradiscal devices work on the principle
described above or on a different principle. Still using RF energy
(for example, at 460 kHz) these bi-polar probes are designed to be
heating elements. There is a resistive element in the probe that
generates heat. When this probe is placed in the body it radiates
heat to the tissue that surrounds it. There is no need for a return
electrode, but there is a need to measure the temperature and
provide that information to the generator for a temperature control
function.
[0008] Therefore, the bi-polar probe serves two major functions. It
is used for delivery of heat energy to the tissue in the disc and
for temperature monitoring through a temperature sensor.
[0009] A limitation of conventional signal generators is that they
are built with switches and controls hardwired in a dedicated
manner for the specific generator. The components are therefore
securely connected to each other for a specific function with
limited reliance on the operation of a central processing unit.
This limits the ease of use and adaptability of the signal
generator.
[0010] For example, at the time of purchasing new medical probes
for a new technique, it is common to acquire, at the same time, a
dedicated electrical signal generator. Consequently, there is a
significant cost associated with purchasing, storing and
maintaining dedicated electrical signal generators for a large
variety of medical probes. Upgrading a hardwired electrical signal
generator to accommodate a new medical probe is costly, if possible
at all. It is very difficult to change the functions of the machine
without changing the actual physical parts and without adding user
input controls such as buttons, switches and dials. In the Pain
Management field, for example, this is costly and inefficient
because there are a growing number of procedures being developed
for the treatment of pain. Furthermore, the addition of the new
technique decreases the ease of use as additional user input
controls or components are added to the existing system.
[0011] Another example of this limitation is that there is also a
significant cost related to training personnel, both doctors and
nurses, in the use of such signal generators. Especially since this
training must be done for each new signal generator. Each signal
generator has its own proprietary configuration and requirements
for use. The nurse or doctor must set switches and controls to
desired settings prior to use.
[0012] Currently, the generic signal generators are very complex to
use and require extensive training of personnel who operate them.
The flow of operations is not intuitive and there is no support for
the user for troubleshooting. Furthermore, excessive control
buttons and switches that are not always needed for every procedure
complicate the user interface. The complexity and lack of
operational information makes the use of the current generators
time consuming, frustrating and costly for the physicians because
of increased training required.
SUMMARY OF THE INVENTION
[0013] There is therefore a need for an apparatus for delivering a
controlled source of energy to an application tool, combining
features that customize the utilization to a particular
specialization, thus allowing ease of use and safety. There is also
a need for an apparatus for delivering a controlled source of
energy to an application tool that has flexibility for quick and
inexpensive upgrading.
[0014] Accordingly, an object of the invention is to provide an
energy generator built on a software platform that flexibly allows
for modifications of programmed energy delivery profiles and use
with different application tools.
[0015] According to one broad aspect of the present invention,
there is provided an energy delivery system for delivering energy
to a patient's body via at least one medical instrument of a
plurality of different medical instruments, the system comprising
an energy generator comprising a detector associated with an
electrical connector port of the generator for detecting an
identifier from a plurality of identifiers, the generator adapted
to enable functions relevant to the identifier upon detecting the
identifier; and at least one instrument cable comprising one of the
plurality of identifiers, the cable comprising a first electrical
connector for connection to the connector port of the generator and
a second electrical connector for connection to a connector of the
at least one medical instrument.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] These and other features, aspects and advantages of the
present invention will become better understood with regard to the
following exemplary and nonlimiting embodiments illustrated in the
accompanying drawings wherein:
[0017] FIG. 1 is a schematic representation of a basic RF lesioning
circuit
[0018] FIG. 2 is a block diagram of the architecture of an
electrical signal generator;
[0019] FIG. 3 is a block diagram of the main components of an
electrical signal generator;
[0020] FIG. 4 is a schematic view of the components of a Front
Panel User Interface for the signal generator;
[0021] FIG. 5 is a flow chart of the probe recognition process;
[0022] FIG. 6 is a flow chart of the error/fault detection and
control process;
[0023] FIG. 7 is a flow chart of the main steps carried out while
using a medical probe signal generator.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0024] While illustrated in the block diagrams (FIGS. 2 and 3) as
ensembles of discrete components communicating with each other via
distinct data signal connections, it will be understood by those
skilled in the art that the embodiments described herein are
provided by a combination of hardware and software components, with
some components being implemented by a given function or operation
of a hardware or software system, and many of the data paths
illustrated being implemented by data communication within a
computer application or operating system. The structure illustrated
is thus provided for efficiency of teaching the present
embodiment.
[0025] The signal generator has the ability to control the output
and therefore the treatment in real time using a classical control
system. In this case, the control system incorporates temperature
feedback to adjust the level of current and voltage supplied to the
tissue. Input to the control system is provided from the tissue
temperature measurements made by the probe.
[0026] FIG. 1 illustrates a schematic of a basic RF lesioning
circuit of common pain management signal generators. The basic
components of the circuit include the electrical RF generator 1
which converts readily available electricity mains outlet to
radiofrequency electricity and supplies the power to the output
terminals 2 according to settings or a control algorithm; typically
one output terminal is connected to a dispersive electrode 3 that
is placed on the surface of patients body 5 and the other output
terminal is connected to an active electrode 4 that is used to
concentrate the current density in a target lesion location 6.
[0027] FIG. 2 shows a schematic diagram of the interaction between
the application, driver and board levels of one embodiment. The
application level 10 contains all the software-coded modules that
drive the functions of the generator. What follows are examples of
functions that are performed and stored at the application level
10.
[0028] Temperature profile calculations are performed to convert
the signal received from the temperature sensor in the RF probe
into temperature values that can be used in the control algorithm.
This is done through temperature lookup tables 36 that are
preprogrammed into the application level. A signal transmitted from
the temperature sensor is converted using temperature lookup tables
36 into a meaningful temperature value that can be displayed on the
screen 34 to the user. This conversion is done at the application
level 10 and the result is displayed on the screen 34 for the user
to see.
[0029] Energy delivery to an application tool is governed by a
classical control system (PID control) that is programmed at the
application level 10. The inputs are temperature and power feedback
loops that are connected to the temperature measuring probe 30. The
output of the control system is the appropriate amount of voltage
and current required to perform the programmed function.
[0030] The application level 10 is programmed to assign different
functions to different user input controls such as switches and
dials 37. This assignment of functions of the user input controls
is done as soon as the application level 10 is turned on and is
constantly modified depending on the current mode selected and the
probe 30 that is attached to the generator. Algorithms are coded
into the application level 10 to perform the selection of modes.
These algorithms 33 take information from the Probe Type Detection
function 32 of the generator to determine which probe 30 is
attached and combine that information with user inputs introduced
using user input controls 37 to determine the information to be
displayed on the screen 34. When there is no user input as to the
selection of the mode, the generator defaults to the most
appropriate screen/mode for the probe 30 selected. The generator
gets these screens from a graphical user interface library. This
default to the appropriate mode and, thus, the display of the
appropriate screen, makes the generator straight-forward to use.
The modes are selected and the algorithm assigns the screens to be
shown on the display 34.
[0031] With the display of the appropriate screen on the display 34
comes the assignment of the input settings 58 available to the user
(see FIG. 4). These values are programmed into the application
level 10 with the increments of settings that will be provided to
the user through the display 34. These settings can be adjusted to
meet the user requirements according to conditions predetermined by
the algorithms in the application level 10. These predetermined
conditions are based on safe and effective timings for the
modification of the settings. When the user makes a change to the
settings that are displayed by the settings indicators 58 he has
the option of saving those settings as the default values. This
save setting function is performed by the user's manipulation of an
assigned switch 61 and the relay of that input to the software at
the application level 10. The software (application level 10)
stores the saved settings appropriately until the values are
changed and saved.
[0032] Certain settings that are not used on a regular basis by the
user are separated from the most commonly used settings and placed
on a separate screen stored in the graphical user interface library
in the application level 10. This simplifies the display and
minimizes the settings that can be controlled on a more regular
basis, thus increasing the ease of use. These less common settings
can be changed within the limits of a predetermined range and can
be saved by the press of an assigned switch. These less common
settings are stored at the application level 10.
[0033] Messages displayed on the screen 34 are one of the ways that
the generator interacts with the user in order to inform the user
of the actions required or the status of the generator. These
messages are called by a routine that is accessible by the
application level 10 and they come in different categories
including informational messages, error messages, and fault
messages. This messaging system is preprogrammed at the application
level 10 and the display of these messages is controlled by the
constant monitoring of the status of the machine and the user
inputs. This monitoring is synthesized by the application level 10
and information is taken from all input drivers 14, 15, 16, 17 and
internal circuitry checks that are cycling at all times. When the
application level 10 is notified of a user input command or a
compromise in generator operation, the appropriate message is
selected from the routine and displayed. These compromises in
generator function can include exceeding software shut down limits
that are defined in the application level 10, hardware problems
such as faulty measuring systems, problems with the energy delivery
system, conflicting settings by the user and any other internal
problems that are contradictory to the application level 10 or any
other level's operational requirements.
[0034] Parameters that are changing during energy delivery could
also be stored at the application level 10. This way, a history of
the lesion procedure could be extracted from the generator at a
later date. This mechanism would involve transferring the variables
that are being adjusted by the control loop into a storage device
until it could be accessed and downloaded or transferred to an
external device.
[0035] The application level 10 is directly linked to the operating
system 11 (in some embodiments, a stRT Linux V1.00) and the Real
Time Kernel (RTX) 12. Access to the central processing unit (CPU)
13 is provided through the operating system 11. No commands from
the application level 10 can run without access to the CPU 13. The
RTX 12 manages the access to the CPU 13 and controls the resources
of the CPU 13.
[0036] Connected to the O/S 11 is a system of drivers 14, 15, 16,
17 that are responsible for communication and direction of the four
circuit boards 18, 19, 20, 21 of the generator. The four drivers
are: the stimulation and measurement (SAM) driver 14, the screen
driver 15, the RF board driver 16 and the I/O driver 17. The four
boards of the generator are: the stimulation and measurement (SAM)
board 18, the screen 19, the RF board 20, and the switches or I/O
interface 21.
[0037] The SAM Board 18 is used for a variety of stimulation and
measurement functions. The functions performed at the SAM Board 18
are stored in the driver and reported to the application level
10.
[0038] In one embodiment, the shape and the size of the stimulation
pulses is determined by the application level 10 based on the
settings of the generator and the energy delivery circuitry on the
SAM board 18. This circuitry includes a switching mechanism that
allows the pulses to be enabled or disabled based on commands from
the application level 10. The presence of the stimulation output is
detected at the circuitry and fed-back to the application level 10
for feedback to the user on the display 57. When a probe 30 is
connected to the generator, the Probe Type Detector 32 function
uses standard circuitry methods to assign the probe a DAC count
that can be used to identify the probe to the application level
10.
[0039] As previously mentioned, the temperature lookup tables and
conversions are done at the application level 10, but the analog
circuitry that connects to the probe 30 is on the SAM board 18.
This board sends information, through the driver 14, to the
application level 10 on the voltages that are being read on the
probe 30. That information is processed as previously discussed. It
communicates with the operating system 11 through the SAM driver
14, shown in FIG. 2.
[0040] The screen 19 allows for display of real time measurements
using a LCD display 34 and using graphics of measurements made by
the SAM board 18 and RF Board 20. It displays, in real time, the
measurements in digital and/or graphical form based on the
information processed by the application level 10 and sent to the
driver 15. The graphical user interface is accessed for the
preprogrammed instructions on what to place on the screen in any
particular situation dictated by the application level. It
communicates with the operating system 11 through the screen driver
15.
[0041] The RF Board 20 generates the RF waveforms. It contains the
power, transformers and electrical circuitry needed to supply
electrical current at 460 kHz. The RF energy is applied to the
probe 30 when the output is turned on 54. This RF board 20 is used
to take voltage and current measurements and thus impedance and
power indications are obtained from the registers on this board 20.
It communicates with the operating system 11 through the RF board
driver 16.
[0042] The switches or I/O interface board 21 is responsible for
detecting short circuits for the settings user input controls 53,
mode selection user input controls 55, output ON/OFF switch 54 and
footswitch 40 for quick (20 ms) recognition of the user inputs. The
user input controls 53, 54, 55 on the front panel (FIG. 4) are
connected to the board 21 and the circuitry allows for the
detection of a user input control press or hold. These user input
controls 53, 54, 55 function through standard switching techniques,
preferably soft touch switching techniques. The detection of user
input at the board level is translated by the driver and provided
to the application level 10 for processing and synthesis. It
communicates with the operating system 11 through the I/O driver
17.
[0043] Referring to FIGS. 2 and 3, the screen 19 and user input
controls 37 are the input and output devices that communicate with
the user. The probe 30 and connector cable 31 are switched between
the RF board 20 and the SAM board 18 depending on the desired
function of the probe 30. The physician will be using the probe 30,
the connector cable 31, the display 34 and the user input controls
37 to interact with the RF generator.
[0044] This system is very flexible in the division of labor
between the application level 10, the driver level 14, 15, 16, 17
and the board level 18, 19, 20, 21. Although it has been found to
be most efficient to apply most controls at the application level
10, it is possible to put any or all of the functions at different
levels. Any combination of task division including these three
levels would be an improvement in flexibility and functionality on
the prior art technology. For example, the Pain Management
generators on the market today tend to have the control of the
temperature profile at either the board level or the driver level.
These would be considered low level controls and would make it
difficult to incorporate changes to the device without changing a
lot of the hardware in the generator.
Preferred Radiofrequency Waveform Specifications
[0045] A continuous radiofrequency waveform can have a set
frequency (for example, 460 kHz) and shape (for example,
quasi-sinusoidal). The amplitude of this waveform can be modified
through user inputs using the user input controls 37, in
combination with or independently of the PID control of the output,
upon energy delivery, depending on the mode selected. In the
preferred embodiment, an Automatic Temperature mode performs PID
control on the temperature inputs/monitoring and power
outputs/monitoring. In the case of Manual Power mode, the generator
allows the user to control the power based on the temperature
measurements. During standard RF procedures, the RF wave is
continuous. In pulsed procedures, the switch settings and the
application level 10 determine the delivery profile.
[0046] The RF waveform is generated on the RF board 20, interfaced
to the O/S 11 by the RF driver 16, and controlled by the
application level 10 in the form of PID control systems and
sampling of switch values. The RF waveform is delivered to the
probe after the application level 10 dictates a series of relays
that must take place to switch the probe 30 to the patient.
[0047] FIG. 3 is a block diagram of the preferred main functional
components of the generator. Functional components may be
implemented at any level (application 10, driver or board levels)
of the generator architecture and they can be divided between
levels of the architecture. It will be understood that some of
these components are optional to the operation of the generator and
are simply shown since they form part of the preferred
embodiment.
[0048] A medical device 30 is connected to a connector cable 31,
which is in turn connected to the generator cable connections 56
which has a functional component that acts as a Probe Type detector
32. The Probe Type detector 32 detects which probe 30, of a host of
compatible devices, has been connected to the generator and sends a
probe identification to a mode determiner 33. The mode determiner
33 uses the probe identification to determine in which mode the
generator is to operate. The mode information is sent to the
display 34 for display of the main mode interface. The mode
information is also sent to the RF energy profile determiner 35
which uses temperature look up tables 36 to update the display 34
and the screen user input controls 37 labels and values. In turn,
the screen user input controls 37 can also update the display 34 of
the labels and values for the user input controls 53, 55 on the
screen 19. When the values of the user input controls 53, 55
(displayed on the graphical user interface 58, 60) are changed by
the user, the updated values are sent by the screen switches and
controls 37 to the RF energy profile determiner 35 for the
adjustment of the profile. The profile can also be stored using a
profile keeper 38 which stores the profile parameters transmitted
by the RF energy profile determiner 35.
[0049] The RF energy profile determiner 35 then sends the RF energy
parameters to the RF waveform generator 39 which makes the
appropriate calculations and generates the RF waveform with the
proper amplitude, frequency and time. The footswitch 40 is used to
turn on or off the RF generation. The RF waveform generator 39 can
send data to the display 34 to display a graphical representation
of the RF waveform to be generated. The profile keeper 38 can also
keep in memory the RF waveform parameters. The RF waveform
generator can also update the screen switches and controls 37.
[0050] As the RF energy is being delivered, the current and voltage
applied at the medical device 30 is measured by a current and
voltage measurement circuit 41 or using the current and voltage
that is being delivered. The current and voltage measurement
receives the RF waveform parameters from the RF waveform generator
39 and compares the measured current and voltage to the required
current and voltage as determined by the control algorithm. The
difference between the measured and expected values is sent to the
software/hardware protection circuitry 44 which compares the
differences received with cut off values and triggers an error
generation if necessary. Similarly, the time and amplitude is
measured by a time and amplitude measurement circuit 42 and the
temperature is measured by a temperature measurement circuit 43.
All measurement circuits 41, 42 and 43 can feedback their readings
to the RF waveform generator 39 for adjustment of the zero values
and correction of the parameters.
[0051] The software/hardware protection circuitry 44 receives all
differences between the expected and measured values and is
responsible for triggering an error generation, if necessary. If an
error generation is necessary, the software/hardware protection
circuitry 44 sends a trigger message error/fault message generator
46 and shuts down the generation of RF energy. The error/fault
message generator 46 then sends an error message to the display 34
for display to the user. The software/hardware protection circuitry
determines whether the hardware components should be protected
against potentially harmful conditions. If so, it also triggers the
error/fault message generator 46 to send an error message to the
display 34 and manages the protection of the hardware
components.
[0052] In some embodiments, the system provides for the management
of the values specified by the user for the treatment profiles. See
FIG. 4 for a schematic look at the front panel user interface for
the generator.
[0053] The input/output interface board 21 is given information on
the allocation of variables to user input controls based on the
screen 19 that is selected. The application level 10 determines the
range of the variables and the increments by which they can be
changed by the user. The switch board 21 and driver 17 monitor the
values that the user sets by detecting short circuits at the soft
touch key interface 53, 55. The information on the variable values
is processed and the application level 10 instructs the CPU 13 to
perform mathematical calculations for the treatment profile. These
treatment profiles are based on the physicians requirement that a
lesion of a particular temperature (SET TEMP) is maintained for a
given time (TIME). Additional specifications can include pulse
duration, pulse rate, power limit on the procedures or a special
ramp rate for attaining the wanted temperature. Constant monitoring
of the switch board 21 and switch driver 17, as directed by the
real time kernel 12, allows for real time changes of the system
variables.
[0054] In order to maintain the user specified treatment profile,
the application level 10 uses system feedback information from the
SAM Board 18 temperature measurement for control of RF output. The
PID control algorithm in the application level 10 indicates, for
example, a 20 ms temperature measurement frequency. The operating
system 11 communicates with the SAM driver 14 to obtain the ADC
count from the SAM Board 18 circuitry resulting from the analog
voltage supplied by the probe 30 at the treatment site. This value
is sent to the application level 10 where the probe identification
and ADC count for temperature are combined together to get a
temperature value in degrees from the temperature lookup table 36
for the appropriate probe 30. This temperature can be displayed on
the screen 57 through the screen Driver 15 and/or can be sent to
the PID controllers to adjust the power application for RF
delivery.
[0055] The maintenance of the desired temperature at the treatment
site is performed using PID control techniques. The desired
temperature of the system is compared to the actual temperature and
the changes in current or voltage are determined and applied to the
system.
[0056] For example, in automatic temperature mode, the generator
does automatic temperature control using a PID control system
combined with a power control system to ensure that an appropriate
amount of power is supplied and to ensure that the user specified
treatment profile is delivered.
[0057] The front panel user interface (FIG. 4) of the preferred
embodiment can be described as follows. A power indicator LED 51
indicates if the power if is turned on. A fault indicator LED 52
indicates if a fault has been detected. The liquid crystal display
50 comprises five general areas. The measurement area 57 is where
values measured are displayed. A graphed data and pop up display
area 59, a setting indicators area 58, a mode selection indicators
area 60 and a save settings area 61 are provided. Hardware setting
controls P1 to P5 53 are provided. An output on/off indicator 54, a
series of soft key controls M1 to M7 55 and cable connection
outlets 56 are also provided on the front panel user interface. The
setting controls P1 to P5 53 are inputs to the setting indicators
58. The soft key controls M1 M7 55 are inputs to the Mode Selection
Indicators 60.
Error/Fault Detection (Cut Off Mechanism)
[0058] FIG. 6 is a flow chart of the steps of the error/fault
detection mechanisms. Software shutdown limits are designed to
detect any problems before they affect the components at the
hardware level. The application level 10 gets information of the
Error/Fault event 65 and determines what error/fault code will be
displayed to the user. This information is passed from the
application level 10, to the screen driver 15 and is then displayed
on the screen 59. The error events are all pre emptive events in
the RTX 12 and will take highest priority at the processing level
if they occur.
[0059] If the software fails at any time, the machine is designed
to shut down RF energy immediately. This mechanism is commonly
referred to as a watchdog hardware protection application 66 and it
detects software shutdown. If the watchdog hardware is not toggled
by the software every 20 ms then the watchdog application is
triggered and has no choice but to shut the down the RF Output 71,
72 and 73 right at the level of the RF board through a circuit
cut-off. A fault led is lit 74. In addition, an informational
message is retrieved from the application level and displayed on
the screen 59 to notify the user of the problem and the potential
solution. In cases where software shutdowns are implemented it is
the intention that extra information for the user would allow for
them to troubleshoot the event and determine how to proceed.
[0060] The driver status is verified every 20 ms by a CHECKSUM that
is performed on the data sent by the driver. If there is an
inconsistency in the checksum, the application level 10 triggers an
error. The RF generation is shut down 68. The error/fault condition
is identified 69 and the error/fault message is displayed 70 on the
screen.
[0061] It is also possible to deal with error/faults at any level
throughout the system. For example, certain errors could be
generated from the RF board 20 while others could be generated at
the SAM board driver. The division of labor has infinite
combinations and is best based on the functionality and efficiency
proposed by the system. No matter where the error is generated, the
system has the intelligence to relay that information to the
application level and access the informational message that will
allow the user to troubleshoot.
[0062] Examples of software shutdown limits are as follows:
[0063] measured impedance smaller than 25 or greater than 1000
Ohms,
[0064] measured temperature greater than the set temperature by
5.degree. C. for 5 seconds or by 10.degree. C. for 1 second,
[0065] measured RF power greater than the set RF power multiplied
by 1.5 plus 5 W for 100 ms,
[0066] measured RF power greater than the set RF power multiplied
by 1.5 plus 5 W for 1 s, or
[0067] measured RF voltage greater than 170 Vrms and a measured RF
current greater than 0.9 Arms.
[0068] Examples of hardware shutdown limits are as follows:
[0069] measured RF Power greater than 60 W+5%,
[0070] measured RF voltage greater than 200 Vrms.+-.5%,
[0071] measured RF current greater than 1 Arms.+-.5%,
[0072] stimulation current greater than 40 to 44 mA, and
[0073] stimulation voltage greater than 11 V.
Probe Identification
[0074] A probe 30 is preferably attached to the generator via a
connector cable 31. The connector cable 31 is used in order to
extend the distance that the physician can work away from the
generator, and to provide flexibility in which probes 30 can be
connected. For example, different probes 30 may have different
connectors 31, but any probe 30 can be attached to the generator
using the properly designed connector cable 31. The connector cable
31 comprises a cable attached to two electrical connectors. These
connectors are designed to match the appropriate probe plug-in at
one end and the appropriate generator plug-in at the other.
Connector cables create flexibility in probe compatibility and
create a workable extension of the probe for physicians' use.
[0075] In the preferred embodiment, the port 56 on the generator
where the connector cable 31 is attached is a standard medical
connector. It is possible to make connector cables 31 with the
matching medical connector for any probe 30 that could be attached
to the generator. Because this interchangeability is desirable, a
Probe Type Detector system is incorporated. The Probe Type Detector
32 allows a variety of different probes 30 to be connected to the
generator, initializing appropriate programmed functions relevant
to the probe detected. For example, relevant treatment modes are
provided to the user when a particular probe 30 is connected.
[0076] The connector cable 31 contains the technology that allows
the Probe Type Detector 32 to identify the probe. Specifically, on
the end of each connector cable that connects to cable connection
56, there is a medical 14 pin connector. In all compatible cables,
pins 1, 2, 3 of the 14 pin connector are the identity pins. These
identity pins can be shorted together or have a resistance attached
across them in order to allow the generator to identify what probe
is going to be attached.
[0077] The Probe Type Detector 32 circuitry consists of resistors
connected in series. This connection creates a voltage divider that
is modified by reading the voltage coming from the three
identification pins. This voltage is changed by creating electrical
shorts between pins or by connecting resistors across them. The
resulting voltage is converted to an ADC count through an analog to
digital converter and each probe type is assigned its own ADC
count.
[0078] In the preferred embodiment, the ADC count that corresponds
to the cable 31 attached is written to the Stimulation and
Measurement Board 18 ADC register. This register value is sent
through the driver level to the application level 10 and to the
operating system 11. It is maintained by the application level 10
in order to detect cable connection and disconnection and to use
the information for temperature look up tables.
[0079] FIG. 5 is a flow chart of the steps carried out to identify
probes. Shorts and/or resistors are used between pins of the cable
connector to create a unique identification corresponding to a type
of surgical device 80. The probe recognition voltage divider
circuitry 81 calculates the voltage across the pins. The ADC
converter converts this data 82 to an ADC count. The ADC count is
sent through the driver level 83 to the operating system 84 which
then sends the appropriate data to the application level processing
85 which can map the appropriate profile and/or mode to the probe
30 that is connected.
[0080] FIG. 7 shows a flow chart of the main steps carried out when
using the generator of the preferred embodiment. A compatible probe
is connected to an appropriate connector cable 130. The connector
cable is connected to the generator 131. Then, the Probe Type
Detector determines if the probe is recognized 132. If the probe is
not recognized, an error/fault message is displayed on the screen
133. If the probe is recognized, the treatment mode parameters
corresponding to the probe are retrieved 134. The mode settings are
displayed on the screen 135. The RF generation settings are then
obtained from the user inputs 136. The user accepts the settings
and proceeds by turning on the Output 129. When this is done the RF
energy profile is determined 137 and can be stored 138. The RF
waveform is generated 139 and the parameters (such as voltage,
current, temperature, time and amplitude) are monitored 140. If a
software or hardware malfunction is detected 141, the error/fault
is identified 142 and an error/fault message is generated on the
screen 143. If there is no malfunction, then the monitoring of the
parameters continues 140. Furthermore, the RF output can be
manually turned off 144 anytime during RF output. RF output
terminates automatically when the predetermined parameter, time, is
complete 145. When RF output is stopped, either manually or
automatically, the display on the screen returns to show the mode
settings 135 after a brief pause.
Treatment Profile Implementation and Control Mechanism
[0081] The treatment profile, or the manipulation of temperature
according to treatment time, is commonly specified by the user in
terms of SET TEMP (temperature reached by the tissue) and TIME
(duration of power application). With the software control of the
generator screen 19, only the treatment variables required for a
specific mode of treatment are presented on the screen 19 and the
values are easily adjustable before a procedure. The application
level 10 selects an appropriate treatment mode relevant to the
connected probe and user input control allocation allowing settings
to remain adjustable throughout the procedures or to be made
non-communicating to eliminate the possibility of changes.
[0082] The application level 10 has the capability to manage data
for the user. For example, the modes and settings used can be
saved. The user can input and save comments about the procedure and
the patient's response to stimulation. The user can input and save
treatment data such as time, temperature, impedance, power,
voltage, current, set temperature, and set power. User information
such as names and preferred settings can also be stored. Patient
information can be saved including: name, patient identification
number, address, phone number, fax number, regular physician,
diagnosis, medical history. The data saved could be organized by
the application level 10. The storage of these parameters is done
using a hard drive or flash disk in the generator or real-time
transfer of parameters through a data transfer port. Those skilled
in the art will realize that there are a variety of computer tools
available to perform this data transfer, but the ability to store
the information that will be pertinent for a pain physician in
order to facilitate ease of documentation, due to the flexibility
in the software architecture of the system is unique to this
system. All data entry would be done using a standard computer or a
combination of keys on the generator.
Preferred System Configuration Specifications
[0083] Preferably, the product software is to run on a 486 66
PC/104 by Advantek with 16 MB of RAM and its ROM is to be 32 MB of
Flash EPROM. The display is a 640.times.480 flat panel LCD in VGA
mode.
[0084] The operating system should be a stRTLinux V1.00 and the
compiler should be a gcc version egcs 2.90.29--GNU project C
compiler.
Details of the Components of the Generator and its Tools
[0085] The mode is basically a function that the operator (i.e.
physician) wants to perform on the patient. The following is a list
of examples of interventional pain management modes that can be
made available in the generator.
[0086] Voltage stimulation of nervous tissue: Voltage stimulation
is the most common way to stimulate nervous tissue. Stimulation is
used to check the placement of the electrode by trying to elicit
specific responses from the nerves/patient. This is accomplished by
sending a signal that is similar to the electrical signal used by
either a sensory nerve or motor nerve. If the electrode is close to
a nerve, a noticeable response is elicited. Sensory stimulation is
done at low frequency, typically 50 Hz, in order to reproduce the
pain that the patient feels. Motor stimulation is done at a low
frequency, typically 2 Hz, to ensure the absence of a motor
response (a motor response would indicate that you are too close to
a motor nerve, which is the incorrect position). Therefore, by
reproducing pain using sensory stimulation and applying motor
stimulation without eliciting a motor response the physician can
determine that the electrode is close to the pain transmitting
nerve and not near a motor nerve. And thus, when the intervention
is preformed the correct nerve will be affected. The frequency
range used for both sensory and motor stimulation is within the
range of frequency used by the nervous system and is often termed
physiological frequency range. In this mode the physician can
increase the voltage to stimulate the patient.
[0087] Current stimulation of nervous tissue: This mode has the
same function as Voltage stimulation but allows the physician to
use current manipulation. This will be most applicable to research
settings.
[0088] Automatic Temperature RF lesioning: This is a lesioning
mode, which means that RF is applied to create a zone of heating.
The temperature in this heated zone is set by the user and
controlled by the generator. This is a neuro-destructive technique,
designed to ablate the nerve so as to intervene with the
transmission of a pain signal. This mode uses a Power PID control
system to maintain a temperature profile set by the physician prior
or during the application of RF energy. This mode applies a
continuous waveform of radiofrequency energy over the entire
treatment time.
[0089] Manual RF lesioning: This mode has the same function as the
Automatic Temperature Lesioning mode, ablation of nervous tissue at
neuro-destructive temperatures set by the physician. It can be used
for research and development of new lesioning parameters or instead
of the automatic mode. It involves the manual increase of the Power
in order to obtain and maintain the desired temperature for
lesioning. This mode applies a continuous waveform of
radiofrequency energy over the entire treatment time.
[0090] Pulsed RF lesioning: In this mode, there is a non-continuous
application of energy (pulsed waveform) that is intended to allow
the tissue to maintain a lower temperature (non neuro-destructive)
while still allowing for application of voltages and current over
the treatment time. The goal is to manipulate an electrical field
surrounding the nerve and create some beneficial effect on the
painful nerve without destroying it with heat.
[0091] Intradiscal lesioning: This mode has a different intended
use. This mode is used for therapy involving intervertebral discs.
There are a variety of different mechanisms of therapy that make
this technique effective but they are restricted to accessing the
intravertebral disc with the correct probe and applying RF to a
resistive element which then radiates heat to the surrounding
tissue or through direct application of RF energy to create heating
of the tissue.
[0092] The most common modes that are currently used for treatment
in the field of Interventional Pain Management are: Voltage
Stimulation followed by Temperature Lesioning for nervous tissue
and Intradiscal lesioning for Intravertebral discs.
[0093] Treatment methods in pain management are usually procedures
that are relatively repeatable by the physician. Certain variables
will change in the hands of different physicians and with the
treatment of different patients, but there are standard operations
that the equipment used for the treatments must allow. For example
in facet joint denervation, the physician must have access to
equipment that has stimulation and lesion capabilities. These
capabilities are considered treatment methods. The treatment
methods that are available in the preferred embodiment are grouped
by function so that the user can easily move between the
appropriate treatment methods while avoiding the information for
the treatment methods that they do not intend to use at that point.
As previously mentioned, the physician selects their treatment mode
either by plugging in the appropriate probe (allowing the Probe
Type Determiner to select the treatment mode) or by manually
selecting the mode based on the available selections.
Flexibility and Adaptability of the system and the User
interface
[0094] The other modes present in this generator are gaining
acceptance and use in Pain Management. Some of these modes are not
well established but are used for research or for teaching
purposes. The benefit of this system is that these treatment modes
can be incorporated in this generator without adding more user
interface controls because of the CPU control algorithms and
software input control systems. There are many treatment modes
currently being developed that would also be easily incorporated
into the existing generator due to the fact that the architecture
is software driven and flexible. The output on a Flat Screen
display and the graphical user interface can be easily modified
when these treatments are added to the system without compromising
the ease of use. In addition, the informational messages can be
maintained for the user and can be easily changed to include
information appropriate for future treatments.
[0095] The table below shows examples of compatible probes, the
modes they elicit and the adjustable settings for the modes. In the
Adjustable settings column, a star "*" before a setting represents
a setting that is adjusted in the advanced settings because it is
seldom adjusted. TABLE-US-00001 TABLE 1 Compatible probes, modes
they elicit and adjustable settings for the modes ADJUSTABLE PROBES
MODES SETTINGS Thermocouple Voltage stimulation mode Stimulation
rate monopolar RF probe Pulse duration Voltage Current stimulation
mode Stimulation rate Pulse duration Current standard RF, Automatic
Set temperature Temperature mode Time Ramp time Power limit
standard RF, Manual Temperature limit Power mode Time pulsed RF
mode Set temperature Time Pulse duration Pulse rate Ramp time Power
limit Thermistor monopolar Voltage stimulation mode Stimulation
rate RF probe Pulse duration Voltage Current stimulation mode
Stimulation rate Pulse duration Current standard RF, Automatic Set
temperature Temperature mode Time Ramp time Power limit standard
RF, Manual Temperature limit Power mode Time pulsed RF mode Set
temperature Time Pulse duration Pulse rate Ramp time Power limit
Intradiscal thermal intradiscal lesioning Peak temperature probe
mode Time Initial temperature Initial time Ramp rate Power
limit
[0096] For example, referring to Table 1, if a Thermocouple
monopolar RF probe is connected, the generator will allocate a
button for selection of each of the 5 available modes that are
applicable to the probe. In this case the available modes are
Voltage stimulation mode, Current stimulation mode, standard RF,
Automatic Temperature mode, standard RF, Manual Power mode, and
pulsed RF mode. The available modes and allocation of buttons is
indicated by the screen. When a mode is selected, for example
Automatic Temperature mode, the generator will allocate a button
for adjustment of each of the adjustable settings. In this case the
adjustable settings are: Set temperature and time. Typical values
are 80.degree. C. and 90 seconds. The adjustable settings, values
and allocation of buttons are indicated by the screen.
Additionally, the screen can show graphical information of certain
aspects of the power delivery in real time and instantaneous
values. For example, as power is being delivered the temperature,
power and impedance are graphed with time and the instantaneous
values are also displayed.
Preferred Method of Operating the Electrical Signal Generator
User Interface According to Probe Recognition
[0097] The electrical signal generator is powered on and if nothing
is connected to the cable connections 56 a message is displayed
that prompts the user to connect a medical instrument to its cable
and connect the cable to the electrical signal generator. The
electrical signal generator is in a state called Standby State. In
this state, the Advanced Settings screen can be accessed by
pressing a button.
[0098] Up until the power output is activated, the physician can
place the medical instrument in the patient using methods known to
those skilled in the art.
[0099] A compatible medical instrument (i.e. probe) is connected to
the cable connections 56 of the electrical signal generator.
Automatically, the electrical signal generator enters a default
mode, which is most commonly used first with the connected medical
instrument. For example, when a thermocouple monopolar RF probe is
connected, the electrical signal generator automatically enters
voltage stimulation mode. When the electrical signal generator has
entered a mode and power output has not been initiated it is in
Ready State.
[0100] The user input controls (buttons and dials) are
multifunctional and the functions depend on the probe connected. A
screen is displayed that indicates which mode is selected, which
modes are available for the connected medical instrument, and which
buttons are used to select the modes. This information is indicated
by displaying all available mode titles in boxes next to the
allocated buttons and highlighting the mode selected. Adjustable
settings applicable to the connected medical instrument and
selected mode are also displayed. The user has the option to go to
any of the modes applicable to the medical instrument
connected.
User Interface According to Mode Selection
[0101] When a compatible probe is connected to the electrical
signal generator the user has the option to access any of the
applicable modes by pressing buttons. In each mode, the user can
adjust settings applicable to that mode. The functions of the user
input controls depend, also, on the mode selected. A screen is
displayed that indicates which settings can be adjusted for the
selected mode, which buttons are used to select the modes and the
values of the adjustable settings. This information is indicated by
displaying all of the adjustable setting titles and their values in
boxes next to the allocated buttons. In certain modes the
adjustable settings are only active in a certain state (i.e.
adjustable in "ready" state and not adjustable in "on" state or
vice versa). This is indicated by highlighting the active setting
boxes. When the user is in the desired mode, the relevant
adjustable settings can be altered. Then the power output is
activated by pressing the Output On/Off Switch and Indicator 54.
The electrical signal is delivered to the medical instrument based
on the mode and adjustable settings. Some settings may be adjusted
while the power output is activated. The screen will also display a
graphical representation of various aspects of the delivered
electrical signal in real time and instantaneous values. The
graphical representation is also dependent on the mode
selected.
[0102] When in voltage stimulation mode the adjustable settings are
stimulation rate, pulse duration and voltage. The settings
indicators 58 also display the values of the adjustable settings.
In every mode the screen also identifies which user input controls
55 are allocated for switching to other modes that are applicable
to the connected probe. For example, when a thermocouple monopolar
RF probe is connected, voltage stimulation mode, current
stimulation mode, automatic temperature lesioning mode, manual
power lesioning mode and pulsed lesioning mode are identified in
the mode selection indicators 60 and can be accessed by pressing
the user input controls 55. Other modes can be accessed by pressing
the appropriate user input controls 55 when in Ready State. When
the mode is changed the screen changes to display the appropriate
settings indicators 58 and other displays such as graphs 59 and
measurements 57.
[0103] Therefore, from Ready State of the default mode the user has
the option to enter a different mode, alter the settings in the
present mode or, if satisfied with the settings, activate the power
output. Typically, if a thermocouple monopolar RF probe is
connected the electrical signal generator would automatically enter
Ready State of the Voltage Stimulation Mode and a physician would
stay in this mode and use the settings that are already set and
activate the power output. When the power output is activated, by
pressing the Output On/Off switch and indicator 54, the electrical
signal generator is in the On State. In the On State, the
electrical signal is delivered to the connected medical instrument
according to the mode and settings. Certain settings are adjustable
during the On State. Typically, a physician would use Voltage
Stimulation Mode to apply a signal that would stimulate a sensory
nerve (50 Hz, 1 volt). If the symptomatic pain is reproduced by
applying this signal, then the medical instrument is close to the
target nerve. The Voltage Stimulation Mode is also used to apply a
signal that would stimulate motor nerves (2 Hz, 2-3 volts). If a
motor nerve is stimulated, the medical instrument is too close to a
motor nerve and must be repositioned.
Saving User Profiles
[0104] For each compatible medical instrument, there are available
modes. For each medical instrument and mode, there are adjustable
settings. To save time, all of the adjustable settings can be set
to preferred values and saved so the next time the same type of
medical instrument and mode is used, the preferred values are
automatically recalled. This can be done for each medical
instrument type and mode that the user accesses, thereby creating a
user profile. Furthermore, several user profiles can be saved for
different situations or multiple users.
[0105] When the electrical signal generator is in Standby State the
user can choose a user profile by pressing a button whose function
is indicated on the screen. Alternatively, a medical instrument can
be connected without choosing a user profile and the last user
profile that was in operation is recalled. The first time a user
accesses a mode, the adjustable settings are set to desired values
and saved to the user profile by pressing a button indicated by the
screen. The next time the user accesses that mode the saved
settings are recalled and displayed. The user has the option of
changing the adjustable settings again if desired. But, since the
user profile is recalled, the user is likely satisfied with the
settings and can simply activate the power output.
[0106] It will be understood that numerous modifications thereto
will appear to those skilled in the art. Accordingly, the above
description and accompanying drawings should be taken as
illustrative of the invention and not in a limiting sense. It will
further be understood that it is intended to cover any variations,
uses, or adaptations of the invention following, in general, the
principles of the invention and including such departures from the
present disclosure as come within known or customary practice
within the art to which the invention pertains and as may be
applied to the essential features hereinbefore set forth, and as
follows in the scope of the appended claims.
* * * * *