Abstract:
An ECT system capable of focusing the electrical signals on a specific portion of the patient&#39;s brain is provided. The ECT system includes a means of applying unidirectional electrical signals and asymmetric electrodes for focusing the signals on the patient. A method of titrating an electro-convulsive therapy (ECT) system and a method of operating an ECT system are also provided. The method includes setting an initial current value, administering an ECT signal to the patient, determining if the seizure threshold has been achieved, and repeating as necessary until the seizure threshold is achieved.

Description:
BACKGROUND 
     1. Technical Field 
     The invention relates generally to the field of electro-convulsive therapy. Specifically, the invention relates to a system and method of administering focused electro-convulsive therapy using titration in the current domain. 
     2. Description of the Related Art 
     Seizure therapy was first recognized as a viable treatment for Schizophrenia in 1934 by the Hungarian neuropsychiatrist Von Meduna. Early seizure therapies used pharmacological inducement methods. These early pharmacological methods were plagued by adverse side effects and unpredictability. In 1937, two Italian physicians, Cerletti and Bini, used electrical stimulation to induce the seizures for the seizure therapy. The success of this method quickly led to its adoption throughout the world. The use of electrical stimulation to induce seizures is generally referred to as electro-convulsive therapy (ECT). 
     ECT was in widespread use in the 1940&#39;s and 1950&#39;s for treatment of many severe mental health disorders including schizophrenia. However, the development of pharmacological alternatives to seizure therapy in the mid-1950&#39;s signaled the decline of ECT use. Currently, ECT is only sparingly used. However, due to limitations in the pharmacological alternatives, many psychiatrists have recognized the continuing viability of ECT and some have suggested that ECT use may be increasing. 
     Early ECT systems used standard 50 or 60 Hz sine wave electrical signals as this type of signal was readily available on the consumer power grid. Once researchers had established a set of stimulus parameters that was effective at producing seizures, there was no longer a need for ECT systems to have parameter varying controls. Consequently, some early ECT systems were not much more than a wall outlet plug, a voltage or current knob, and an ON/OFF switch. 
     Eventually, the electrically induced signals were associated with adverse side effects in the patients such as confusion and amnesia. This led researchers to experiment with the stimulus signals to try to reduce or eliminate the side effects of the treatment. This research led to ECT devices capable of providing a pulse waveform stimulus. Further, prominent ECT researcher, Paul Blachley, decided that, an optimal ECT device should incorporate the capability of monitoring both electroencephalograph (EEG) and electrocardiogram (ECG) signals, have the ability to test the safety of the electrical circuit before delivering the stimulus, and have the ability to allow careful titration to individuals&#39; seizure thresholds. After design and testing efforts, the device envisioned by Blachley, which was known as the MECTA (Monitored Electro-Convulsive Therapy Apparatus) went on the market in 1973, and readily grew in popularity over the following years. Additional improvements continued to be made to the MECTA system over the years including safety improvements and the capability of continuous signal monitoring during treatment. 
     Conventional ECT systems use alternating current (ac) signals. Typically, when using ac signals to generate seizures, symmetric electrodes are used on the patient. Since the electrodes are symmetric and the current is bidirectional, the current distribution in the patient will be essentially symmetric in the vicinity of both electrodes. Consequently, with conventional ECT systems, the ability to focus the electrical signals on a specific portion of the patient&#39;s brain is extremely limited. 
     Also, in administering ECT, it is important to calibrate the ECT system to the individual patient&#39;s seizure threshold. This process is called titration. The titration process is important to ensure that seizures are generated in the most efficient way possible. Efficiently generating the seizures allows for more effective treatment and minimizes the side effects of the treatment to the patient. Conventional ECT systems use a total charge energy titration method in which the pulse width or number of pulses of the signals is manipulated until the patient&#39;s seizure threshold is reached. Unfortunately, it is not possible in conventional systems to perform the titration process by varying only the current. However, the ability to perform a titration process by only adjusting the current, may lead to more efficient determination of the patient&#39;s seizure threshold and minimize adverse side effects to the patient. 
     The invention addresses these and other disadvantages of the conventional art. 
     SUMMARY 
     The disclosure provides an ECT system with the capability of focusing the electrical signals on a specific portion of the patient&#39;s brain. The system includes a means of applying unidirectional electrical signals and asymmetric electrodes for focusing the signals on the patient. The disclosure also provides a method of operating an ECT system including titration in the current domain. Using the titration method of the invention allows a more precise determination of the seizure threshold and thereby, minimizes adverse side effects of the ECT treatment on the patient. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a block diagram of an ECT system according to the invention; 
         FIGS. 2A and 2B  are block diagrams of the delivery circuitry and hardware safety monitors of the system shown in  FIG. 1 ; 
         FIGS. 3A through 6A  are cross-sectional views of negative electrodes according to some embodiments of the invention; 
         FIGS. 3B through 6B  are plan views of negative electrodes according to some embodiments of the invention; 
         FIG. 7A  is a cross-sectional view of a positive electrode according to an embodiment of the invention; 
         FIG. 7B  is a plan view of a positive electrode according to an embodiment of the invention; 
         FIG. 8  is a flowchart of a method of providing Focal Electrically Administered Seizure Therapy to a patient; and 
         FIG. 9  is a flowchart of a method of titrating an ECT system in the current domain to determine a patient&#39;s seizure threshold. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Example embodiments are described below with reference to the accompanying drawings. Many different forms and embodiments are possible without deviating from the spirit and teachings of this disclosure and so the disclosure should not be construed as limited to the example embodiments set forth herein. Rather, these example embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. In the drawings, the sizes and relative sizes of components and regions may be exaggerated for clarity. 
     It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the disclosure. 
     The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, elements, and/or components, but do not preclude the presence or addition of one or more other features, elements, components, and/or groups thereof. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one skilled in the art to which this disclosure pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
       FIG. 1  is a block diagram of an ECT system according to the invention. 
     Referring to  FIG. 1 , an ECT system  10  includes several connections to the patient. The first connection is the ECT stimulus electrodes  12  through which an ECT treatment signal is applied to the patient. The ECT system  10  also includes several patient monitoring inputs  13 ,  14  and  16  that connect to the patient to receive EEG, ECG and/or OMS (optical motion sensor) signals, respectively. 
     The ECT system  10  further includes a user interface  18  through which the user, typically a psychiatrist, interacts or interfaces with the ECT system  10 . In one embodiment of the user interface, a plurality of knobs  20  is included for setting the parameters that define the ECT signals. These parameters include the frequency of the signal, the pulse width of each individual pulse in the signal, the current level, and the duration of the ECT signal. According to some embodiments, the current of the ECT signal can be adjusted independent of the voltage using the knobs  20  on the user interface  18 . The current may also be adjusted independently using the other input means described below, such as the touch screen  22 . 
     The user interface  18  also includes a touch screen  22  which is a touch-sensitive display that allows the user to input commands to the system by touching certain portions of the screen. The system is menu driven so that the user can quickly and efficiently move through the command options. A display  24  is provided to display certain information to the user both prior to and during treatment. A chart recorder  26  provides a hard copy output of the patient monitoring signals. The ECT system  10  further includes a speaker  28  that sounds an audible alarm when certain failures occur in the system and as a safety feature whenever the ECT section is activated. Indicators  30  are also provided as indicator lights for the user. A stimulus control section  32  is provided to allow the user to initiate a treatment. A remote control section  34  may also be provided that allows the user to initiate a treatment while out of reach of the stimulus control section  32 . The remote control section  34 , which works in conjunction with the paddles ( 334 B,  336 B of  FIG. 2B ), disables the (front panel) stimulus control section  32  so that when remote-control-equipped paddles are plugged into the ECT system  10 , a treatment cannot accidentally be initiated from the stimulus control section  32  on the user interface  18 . 
     At the heart of the ECT system  10  is a computer system  36  which orchestrates the operation of the system. The computer system includes four processors: a system processor  38 , a safety processor  40 , a digital signal processor  42 , and a front panel processor  44 . The system processor  38  is coupled to the knobs  20 , the touch screen  22 , the display  24 , and the chart recorder  26  of the user interface  18 . The knobs  20  and touch screen  22  are coupled to the system processor  38  via the front panel processor  44  that emulates a standard keyboard interface. Thus, the system processor communicates to and from the knobs  20  and the touch screen  22  as it would communicate with a standard IBM keyboard. Thus, the knobs  20  and the touch screen  22  can be replaced by a keyboard to provide input to the ECT system  10  for testing and maintenance. 
     The system processor  38  is also coupled to a patient monitoring section  46  through a sensor control block  48 . The sensor control block  48  includes logic that decodes signals received from the system processor  38  and configures the patient monitoring section  46  into various modes responsive thereto. These modes include the normal operational mode in which the patient monitoring signals are received from the patient and test modes wherein the accuracy of the section is tested. 
     The computer system  36  also includes a safety processor  40 . The safety processor  40  is primarily responsible for creating and controlling delivery of the stimulus waveform and coordinating the various safety tests and checks that are performed on and by the ECT system  10 . The safety processor  40  is coupled to the system processor  38  via a serial interface (SERIAL  1 ). The safety processor  40  is also coupled to a safety monitoring section  50  which includes equipment monitors  52  and safety monitors  54 . These monitors  52  and  54  monitor both the equipment as well as the stimulus to determine whether or not the system is performing within specification and, if not, to disable any further treatments. 
     The safety monitor  54  is further coupled to an ECT block  56  which generates the ECT signal responsive to the safety processor  40 . The ECT block  56  is directly coupled to the timing circuits of an A-to-D converter  58  to receive a Z_PULSE signal that is generated during every sample taken by the A-to-D converter  58 . The Z_PULSE signal is used by the impedance-measuring portion of the ECT block  56  to measure patient impedance. The A-to-D converter  58  digitizes the patient monitoring signals received at inputs  13 ,  14  and  16  (i.e., EEG, ECG and OMS). This digitized data is then operated on by the DSP  42  to filter out unwanted power line frequency interference by the use of a frequency adaptive finite impulse response (FIR) filter as well as to decimate the digitized data for display. 
     Safety processor  40  is directly coupled to the speaker  28 , the indicators  30 , the stimulus control  32 , and the remote control  34 . The safety processor  40  initiates an ECT treatment sequence, under certain predetermined conditions, responsive to inputs received from either the stimulus control  32  or the remote control  34 . Both the ECT block  56  and the safety processor  40  also actuate either the speaker  28  or the indicators  30  if certain conditions exist, e.g., internal self-test failed. This provides redundant fault and “arming status” indications for safety purposes. 
     The final section of the ECT system  10  is the isolated data output section  60 . This section is coupled to the computer system  36  via three serial ports: a synchronous serial port (SYNC SERIAL PORT) and two asynchronous serial ports (SERIAL  2 , SERIAL  3 ). The computer system  36  is isolated from the isolated data output section  60  by opto-isolator blocks  62  and  64 . The opto-isolator block  62  is interposed between the DSP  42  and a digital-to-analog converter  66 . The DSP  42  transmits the digitized patient monitoring signals to the digital-to-analog converter  66  in order that those signals may be observed by external equipment coupled to analog outputs  68 . Similarly, the system processor  38  communicates the display data via opto-isolator block  64  to an RS-232 interface block  70 , which provides two RS-232 serial output ports  72  to enable this data to be stored, displayed, or printed by an external computer. The opto-isolators,  62  and  64 , here protect the patient and the operator from shock hazards that may occur due to, e.g., electrical faults. 
     The construction and operation of the ECT system  10  is described in greater detail in U.S. Pat. Nos. 5,755,744 and 6,014,587, which are herein incorporated by reference in their entirety. 
       FIGS. 2A and 2B  are block diagrams of the delivery circuitry and hardware of the safety monitors of the system shown in  FIG. 1 . 
     Referring to  FIGS. 2A and 2B , the three outputs of a pulse driver (+, −, and POWER) are connected to the center-tapped primary winding of a first transformer T 1 . The first transformer T 1  is a step up transformer so that the voltage across the secondary winding is equal to the turns ratio times the voltage across the primary. The current in the secondary, on the other hand, is reduced by the turns ratio. In the preferred embodiment, the turns ratio is equal to 16.6:1. 
     A relay R 1  is interposed between the outputs of the secondary winding and the two paddles  334 B and  336 B. The optional remote control unit  338  is shown connected between relay R 1  and the paddles  334 B and  336 B. However, the optional remote control unit  338  is not required. When the optional remote control unit  338  is not provided, paddles  334 B and  336 B could be simple electrodes that are used when the treatment is initiated from the stimulus control section  32 . 
     The relay R 1  is used to switch a dummy load R 7  into and out of the circuit of the secondary winding of the first transformer T 1 . When the relay is in the position shown in  FIG. 2B , the dummy load R 7  is switched into the circuit and when the relay R 1  is in its other position, the dummy load R 7  is taken out of the circuit and the winding is connected to the paddles  334 B and  336 B. The state of the relay R 1  is controlled by a logic gate  382  whose output is connected to the coil of the relay via line  340 . The logic gate  382  includes two inputs  342  and  344  for receiving a hardware shutdown signal HW_SD and a control signal CNTL 2 . The logic gate  382  switches from the dummy load to the patient, i.e., the paddles, if the control signal CNTL 2  is asserted and the hardware shutdown signal HW_SD is not asserted. This provides the system with the ability to shunt the pulse to the dummy load R 7  under software control as indicated by the assertion of the control signal CNTL 2 , which is under control of the safety processor  40 . The control signal CNTL 2  allows the system to perform an internal self-test in which a pre-treatment ECT signal is applied to the dummy load R 7  and the characteristics of the ECT signal are then examined by the safety hardware and the system rendered inoperable if any of these safety tests fail. 
     The safety monitoring section also includes a second relay R 2 , which is used to either short out, or leave unshunted, a 5 Kohm resistor R 8  in the output circuit under certain test conditions. This 5 Kohm load is shorted by R 2 , thus effectively shorting the secondary winding of the first transformer T 1  when a control signal CNTL 3  is asserted. This control signal is applied to the coil of relay R 2  via input  346 . The 5 Kohm resistor and relay R 2  are used during the self-tests of the instrument&#39;s ability to measure static impedances at zero ohms and 5 Kohms. 
     A second transformer T 2  is used to measure the voltage delivered to the dummy load during pre-treatment testing. The voltage across the primary of the second transformer T 2  is stepped down to the secondary, which is then measured by a voltage monitoring circuit  348 . A current is provided to the secondary winding by an AC current source  350 , which generates a fixed current responsive to the Z_PULSE received on input  352 . This causes a current of approximately 40 μA through the secondary of the second transformer T 2 . Because the current AC amplitude is fixed, then the voltage measured by the voltage monitoring circuit  348  is proportional to the static impedance (of the patient or of the impedance self-test resistor R 8 ). The measured voltage DELIV_V is provided to the safety processor  40  from the voltage monitoring circuit  348  on output  354 . A signal corresponding to the measured impedance IMP is provided by the voltage monitoring circuit  348  to an amplifier  356  whose output is then rectified by precision rectifier  358  and filtered by low pass filter  360 . The output of low pass filter  360  is a signal Z on output  362  that is proportional to the measured static impedance. 
     The circuits described above measure what is termed “static” impedance. Static impedance in the context of ECT is the impedance measured under test conditions of very low currents applied to the patient (or test resistors). Static impedance changes little with continued application of the current used to perform the measurement. “Dynamic” impedance in the context of ECT, on the other hand, is the effective impedance presented by the patient&#39;s scalp and the paddle electrodes to the applied treatment current. Dynamic impedance is the impedance observed at very high applied currents, where the scalp tissue exhibits non-linear impedance behavior. The dynamic impedance seen in ECT is much lower than the static impedance seen in ECT, and furthermore, decreases generally during the duration of the treatment. Dynamic impedance is calculated by the system processor by dividing the delivered voltage by the delivered current. Signal Z on line  362  is not used to obtain dynamic impedance. 
     The circuit also includes a third transformer T 3 , which is used to measure the current through the output circuit of the first transformer T 1 . The third transformer T 3  is a (voltage) step up transformer whose secondary is coupled to a current monitoring circuit  364  which measures the current through the output circuit. This measured current signal DELIV_I is then provided to the safety processor  40  on output  366 . 
     The circuit also provides an energy monitor circuit. The energy monitor includes an analog multiplier  388 , a voltage-to-frequency converter  390 , a two-stage counter  392  and an energy limit select circuit  394 . The analog multiplier has two inputs: one of which is connected to the voltage monitoring circuit  348  to receive the measured voltage signal DELIV_V; and the second input is connected to the current monitoring circuit  364  to receive the measured current signal DELIV_I. The analog multiplier then multiplies these two signals together to produce a delivered power signal DELIV_P on output  396 . The delivered power signal is then provided to a voltage-to-frequency converter  390  which converts the voltage level of the delivered power signal to a clock signal having a frequency proportional to that power signal level. The clock signal is provided to a clock input of a counter  392 , which, in the preferred embodiment, is implemented by cascading two binary counters. The counters produce a binary count that increments with each rising edge of the clock signal from the voltage-to-frequency converter  390 . This binary count is then provided to a maximum energy limit select circuit  394  which compares the binary count to a preset limit. If the binary count exceeds this preset limit, the circuit  394  asserts a signal ENERGY_MAX on output  398  to indicate that the amount of energy delivered to the patient during this treatment has exceeded a pre-selected limit. In the preferred embodiment, the pre-selected limit is adjustable with the use of jumpers to allow for different limits to be set in different countries or under different conditions. It should be apparent that the voltage-to-frequency converter  390  and counter  392  are but one implementation of what is essentially an integrator, which integrates the delivered power signal DELIV_P over time. Other integrators, of course, can be used. 
     The paddles  334 B and  336 B may be part of an optional remote control package that allows the user to initiate an ECT treatment from the paddles  334 B and  336 B. Otherwise, the user can only initiate a treatment from the front panel ‘Start Treatment’ switch. One of the paddles includes a two-stage switch represented by switches S 11  and S 12  in  FIG. 2B . The first switch S 11  initiates a pre-treatment test sequence. Actuation of the first switch S 11  is detected by measuring the current through the optional remote control unit. This is accomplished by switching different resistances into the circuit according to which switch is actuated. The first switch S 11  is normally open, as indicated in  FIG. 2B . In addition, the second switch S 12  is normally in the position shown. In this default state, a circuit is formed with resistors R 9  and R 10  across which a voltage is supplied by remote control power supply  400 . The current supplied by the power supply  400  is detected by a current monitoring circuit  402  which is coupled to the power supply  400  by a fourth transformer T 4 . The current monitor  402  produces a signal RC_SENSE, which is proportional to the measured current supplied by the power supply  400 . This signal RC_SENSE is provided to a threshold detector  404 , which compares the current level of the signal RC_SENSE to determine whether the current level exceeds a predetermined amount. If insufficient current is detected, the circuit  404  assumes that the remote control unit  338  is not connected. If the circuit, however, detects this minimum current level, then the circuit  404  switches the state of switches S 13 , S 14  and S 15  so as to disable the front panel switch S 16  so that a treatment cannot accidentally be initiated from the stimulus control section  32  on the user interface  18 . 
     If the test switch S 11  is actuated, on the other hand, resistor R 12  is coupled in parallel with resistor R 10 , thereby presenting a different load to the remote control power supply  400 . This current is also measured by the current monitor  402 . 
     The treatment switch S 12  actually corresponds to the second stage of the two-stage switch comprised of S 11  and S 12 . Therefore, S 12  can only be actuated if S 11  is also actuated. If S 12  is actuated (and therefore S 11 ), a circuit is formed with R 9 , R 11  and light-emitting diode D 3  of an opto-coupler. Passing a current through diode D 3  causes a signal to be produced by optical detector Q 3 , which is then passed on to the safety processor as the TREAT_RELEASE signal through switch S 13 . This signal can then be used to determine if the treatment switch S 12  is released prior to the full treatment duration that was programmed by the front panel controls. 
     A bridge rectifier  380  may be interposed between the relay R 1  and the paddles  334 B and  336 B depending on the position of a relay R 20 . The position of the relay R 20  is determined by the signal SIGNAL_DIR. When the relay R 20  is in the position shown in  FIG. 2B  (the first position), a bi-directional, or pulsed alternating current, signal is applied directly from the relay R 1  to the paddles  334 B and  336 B. In other words, when the relay R 20  is in the first position, the bridge rectifier  380  is bypassed. However, when the relay R 20  is in the second position (the opposite position of that shown in  FIG. 11B ), the relay R 1  is coupled to the paddles  334 B and  336 B through the bridge rectifier  380 , thereby delivering a unidirectional, or pulsed direct current, ECT signal to the paddles  334 B and  336 B. When the unidirectional ECT signal is applied to the paddles  334 B and  336 B, the paddle  334 B can be referred to as a positive paddle and the paddle  336 B can be referred to as a negative paddle. The unidirectional ECT signal can be used to focus the ECT stimulus on specific portions of the patient&#39;s brain, thereby providing more efficient treatment. 
       FIGS. 3A through 6A  are cross-sectional views of negative electrodes according to some embodiments of the invention.  FIGS. 3B through 6B  are plan views of negative electrodes according to some embodiments of the invention. 
     In conventional ECT systems, the electrodes attached to the paddles  334 B and  336 B are symmetric. In other words, the electrodes attached to the paddles  334 B and  336 B are the same for both paddles. The electrodes in conventional systems are typically circular with a diameter of about 2 inches. However, according to the invention, the electrodes attached to the paddles  334 B and  336 B are asymmetric. In other words, the electrode attached to the positive paddle  334 B (the positive electrode) may be different in one or more of size, shape, and area from the electrode attached to the negative paddle  336 B (the negative electrode). According to some embodiments, both the positive and negative electrodes are made from solid  303  stainless steel. However, the positive and negative electrodes may be made from different materials. Also, the positive electrode may be made from a different material than the negative electrode. 
     Referring to  FIGS. 3A through 6B , a negative electrode  600  includes an electrical contact portion  602  and a patient contact portion  604 . The electrical contact portion  602  electrically connects the negative electrode  600  to the negative paddle  336 B. The patient contact portion  604  of the negative electrode  600  is placed on the patient&#39;s scalp during treatment along with the positive electrode  610  (as shown in  FIGS. 7A and 7B ) and determines the distribution of the electrical current in the patient&#39;s brain. The electrical contact portion  602  may be generally cylindrical in shape. According to some embodiments, the electrical contact portion  602  is cylindrically shaped and has a height of about 0.5 inches and a diameter of about 0.32 inches. 
     The patient contact portion  604  may be substantially rectangular in shape, with rounded corners. According to some embodiments, the patient contact portion  604  may be rectangular with the length of the short axis of about 1 inch and the length of the long axis of about 2.5 inches. The corners may have a small radius of curvature as shown in  FIG. 3B  or a greater radius of curvature as shown in  FIG. 4B . As an example, the radius of curvature of the patient contact portion  604  in  FIGS. 3B and 4B  may be about 0.125 and 0.25 inches, respectively. The corners may have an even greater radius of curvature as shown in  FIG. 5B , such that the sides of the patient contact portion  604  are substantially semicircular. As an example, the radius of curvature of the patient contact portion  604  in  FIG. 5B  may be about 0.5 inches. According to a preferred embodiment, as shown in  FIGS. 6A and 6B , the patient contact portion  604  may be substantially rectangular with short and long axis lengths of 2 and 3 inches, respectively, with a radius of curvature of the corners of 0.25 inches. 
       FIG. 7A  is a cross-sectional view of a positive electrode according to an embodiment of the invention.  FIG. 7B  is a plan view of a positive electrode according to an embodiment of the invention. 
     Referring to  FIGS. 7A and 7B , the positive electrode  610  may include an electrical contact portion  612  and a patient contact portion  614 . The electrical contact portion  612  of the positive electrode  610  may be substantially similar to the electrical contact portion  602  of the negative electrode  600  described above. The patient contact portion  614  of the positive electrode  610  may be substantially different in one or more of size, shape, and area from the patient contact portion  604  of the negative electrode  600 . For example, the patient contact portion  614  of the positive electrode  610  may be substantially circular shaped with a diameter of about 0.75 inches. 
       FIG. 8  is a flowchart of a method of providing Focal Electrically Administered Seizure Therapy to a patient. 
     Referring to  FIG. 8 , the first step in the method of providing ECT to a patient consists of applying electrodes to the patient&#39;s scalp. When asymmetric electrodes are used, the electrodes may be arranged on the patient&#39;s scalp so as to focus electrical signals on a specific portion of the patient&#39;s brain. As an example, a negative electrode may be positioned on a posterior portion of the patient&#39;s head and the positive electrode may be positioned on an anterior portion of the head. Further, the negative electrode may be larger than the positive electrode. Next, a titration procedure is performed on the patient. The titration procedure is used to estimate the seizure threshold, or the lowest dose of electricity needed to produce a seizure. Titration usually is conducted at the first treatment of a patient with an electrical stimulus administration that is sufficiently low so that most patients do not have a seizure. As an example, the first electrical stimulus may be at a level at which a seizure would result in only about 15% of the general population. If in fact no seizure occurs, one or more parameters of the ECT signal are changed and the modified stimulus is applied to the patient. This process of applying the signal, determining if a seizure results, and adjusting the ECT signal is repeated until a satisfactory seizure is produced. Generally, the titration procedure must be completed within five applications of the stimulus to the patient in a single session due to limitations on the patient&#39;s physiology and the capabilities of anesthetic technology. 
     A titration procedure is desirable before administering ECT treatment because there are marked individual differences among patients in their seizure threshold. Using standard approaches to titration, at least a 50-fold range has been identified in seizure threshold values. A good deal of this variability is due to individual differences in skull anatomy resulting in variability of current shunted away from the brain through the scalp and skull. Only a small portion of current in any pulse actually enters the brain. In the past, titrating dosage has been primarily manipulated in terms of the number of pulses; either by manipulating the frequency of pulses (i.e. the number of pulses per second) or the duration of the pulse train. Despite the fact that people vary in the amplitude of the pulse in their brain tissue, adjustment for these individual differences has only manipulated the total number of pulses the patient receives. However, titrating in the current domain, in accordance with embodiments of the invention, can be more efficient and require lower charge when determining the seizure threshold. Compared to traditional techniques, titration in the current domain may result in less severe cognitive side effects from the ECT treatment. 
     Two methods are generally used to determine if a seizure has been satisfactorily produced during the titration procedure. Most modem procedures use EEG signals to determine if a seizure has been produced. Typically, two channels of EEG monitors are connected to the patient to monitor for seizures. The second method is to monitor for motor seizures. This may be done using an optical motion sensor attached to the patient. 
     Once the titration procedure is completed and the seizure threshold is determined, the ECT system parameters are set to provide the desired treatment to the patient. Finally, the desired ECT signal is administered to the patient to induce seizures. 
       FIG. 9  is a flowchart of a method of titrating an ECT system in the current domain to determine a patient&#39;s seizure threshold. 
     Referring to  FIG. 9 , the method of titrating an ECT system in the current domain includes first setting the parameters of the ECT system so as to provide a low current initial ECT signal to the patient. Conventional ECT systems have a minimum current level of 500 mA. However, according to some embodiments of the invention, a minimum current level of 100 mA may be used for titration in the current domain. Therefore, the low current initial ECT signal can be 100 mA. In the next step of the method, the low current initial ECT signal is administered to the patient. Then, a determination is made as to whether the patient&#39;s seizure threshold has been reached. If the seizure threshold is reached, the method ends. If the seizure threshold is not reached, the parameters of the ECT system are set to provide an incrementally higher current ECT signal, the higher current signal is administered to the patient, and a determination is made as to whether the patient&#39;s seizure threshold is reached. This process continues until the patient&#39;s seizure threshold is reached. 
     According to some embodiments of the invention, the current is doubled for each successive application of the stimulus until the seizure threshold is determined. Also, the current may be adjusted from about 100 mA to about 800 mA. 
     According to embodiments of the invention, the titration method can be performed by adjusting the current of the ECT signal rather than the number of pulses or the width of pulses as in conventional systems. Using the current titration method of the invention allows a more precise determination of the seizure threshold and thereby, minimizes adverse side effects of the treatment on the patient. 
     It should be appreciated that the above titration process may be embodied in an article of machine-readable media containing code that, when executed, causes the ECT system to perform these functions. 
     According to the invention, as described above, an ECT system includes a rectification circuit to allow unidirectional, or direct current stimulus to a patient. The ECT system also includes asymmetric positive and negative electrodes to allow focused stimulus of specific portions of the patient&#39;s brain. 
     According to some embodiments of the invention, a method of administering an ECT treatment to a patient includes adjusting the current of an ECT signal independently from the voltage to allow titration in the current domain. Therefore, a patient&#39;s seizure threshold can be more efficiently and reliably determined. 
     The foregoing is illustrative of the invention and is not to be construed as limiting thereof. Although a few example embodiments of the invention have been described, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from the novel teachings and advantages of the invention. For example, several shapes and sizes of electrodes are specifically shown, but many more shapes and sizes of electrodes are possible. Accordingly, all such modifications are intended to be included within the scope of the invention as defined in the following claims.