Abstract:
Disclosed are methods and systems and methods for patient-feedback control of non-invasive deep brain or superficial neuromodulation using sound impacting one or multiple points in a neural circuit to produce acute effects and, with application in multiple sessions, Long-Term Potentiation (LTP) or Long-Term Depression (LTD) to treat indications such as neurologic and psychiatric conditions. One or more of sonic transducer positioning, intensity, frequency, dynamic sweeps, phase/intensity relationships, and firing patterns are changed through feedback from the patient to optimize patient experience through up-regulation or down regulation. Examples are decreases in acute pain or tremor due to more effective impact on the neural targets.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This patent application claims priority to provisional patent applications Application No. 61/295,760, filed Jan. 18, 2010 entitled “PATIENT FEEDBACK FOR CONTROL OF ULTRASOUND FOR DEEP-BRAIN NEUROMODULATION.” The disclosures of this patent application are herein incorporated by reference in their entirety. 
     
    
     INCORPORATION BY REFERENCE 
       [0002]    All publications, including patents and patent applications, mentioned in this specification are herein incorporated by reference in their entirety to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference. 
       FIELD OF THE INVENTION 
       [0003]    Described herein are systems and methods for control of Ultrasonic Stimulation including one or a plurality ultrasound sources for neuromodulation of target deep brain regions to up-regulate or down-regulated neural activity. 
       BACKGROUND OF THE INVENTION 
       [0004]    It has been demonstrated that focused ultrasound directed at neural structures can stimulate those structures. If neural activity is increased or excited, the neural structure is said to be up regulated; if neural activated is decreased or inhibited, the neural structure is said to be down regulated. Neural structures are usually assembled in circuits. For example, nuclei and tracts connecting them make up a circuit. The potential application of ultrasonic therapy of deep-brain structures has been suggested previously (Gavrilov LR, Tsirulnikov EM, and IA Davies, “Application of focused ultrasound for the stimulation of neural structures,” Ultrasound Med Biol. 1996;22(2):179-92. and S. J. Norton, “Can ultrasound be used to stimulate nerve tissue?,” BioMedical Engineering OnLine 2003, 2:6). Norton notes that while Transcranial Magnetic Stimulation (TMS) can be applied within the head with greater intensity, the gradients developed with ultrasound are comparable to those with TMS. It was also noted that monophasic ultrasound pulses are more effective than biphasic ones. Instead of using ultrasonic stimulation alone, Norton applied a strong DC magnetic field as well and describes the mechanism as that given that the tissue to be stimulated is conductive that particle motion induced by an ultrasonic wave will induce an electric current density generated by Lorentz forces. 
         [0005]    The effect of ultrasound is at least two fold. First, increasing temperature will increase neural activity. An increase up to 42 degrees C. (say in the range of 39 to 42 degrees C.) locally for short time periods will increase neural activity in a way that one can do so repeatedly and be safe. One needs to make sure that the temperature does not rise about 50 degrees C. or tissue will be destroyed (e.g., 56 degrees C. for one second). This is the objective of another use of therapeutic application of ultrasound, ablation, to permanently destroy tissue (e.g., for the treatment of cancer). An example is the ExAblate device from InSightec in Haifa, Israel. The second mechanism is mechanical perturbation. An explanation for this has been provided by Tyler et al. from Arizona State University (Tyler, W. J., Y. Tufail, M. Finsterwald, M. L. Tauchmann, E. J. Olsen, C. Majestic, “Remote excitation of neuronal circuits using low-intensity, low-frequency ultrasound,” PLoS One 3(10): e3511, doi:10.137/1/journal.pone.0003511, 2008)) where voltage gating of sodium channels in neural membranes was demonstrated. Pulsed ultrasound was found to cause mechanical opening of the sodium channels, which resulted in the generation of action potentials. Their stimulation is described at Low Intensity Low Frequency Ultrasound (LILFU). They used bursts of ultrasound at frequencies between 0.44 and 0.67 MHz, lower than the frequencies used in imaging. Their device delivered 23 milliwatts per square centimeter of brain—a fraction of the roughly 180 mW/cm 2  upper limit established by the U.S. Food and Drug Administration (FDA) for womb-scanning sonograms; thus such devices should be safe to use on patients. Ultrasound impact to open calcium channels has also been suggested. 
         [0006]    Alternative mechanisms for the effects of ultrasound may be discovered as well. In fact, multiple mechanisms may come into play, but, in any case, this would not effect this invention. 
         [0007]    Approaches to date of delivering focused ultrasound vary. Bystritsky (U.S. Pat. No. 7,283,861, Oct. 16, 2007) provides for focused ultrasound pulses (FUP) produced by multiple ultrasound transducers (said preferably to number in the range of 300 to 1000) arranged in a cap place over the skull to affect a multi-beam output. These transducers are coordinated by a computer and used in conjunction with an imaging system, preferable an fMRI (functional Magnetic Resonance Imaging), but possibly a PET (Positron Emission Tomography) or V-EEG (Video-Electroencephalography) device. The user interacts with the computer to direct the FUP to the desired point in the brain, sees where the stimulation actually occurred by viewing the imaging result, and thus adjusts the position of the FUP according. The position of focus is obtained by adjusting the phases and amplitudes of the ultrasound transducers (Clement and Hynynen, “A non-invasive method for focusing ultrasound through the human skull,” Phys. Med. Biol. 47 (2002) 1219-1236). The imaging also illustrates the functional connectivity of the target and surrounding neural structures. The focus is described as two or more centimeters deep and 0.5 to 1000 mm in diameter or preferably in the range of 2-12 cm deep and 0.5-2 mm in diameter. Either a single FUP or multiple FUPs are described as being able to be applied to either one or multiple live neuronal circuits. It is noted that differences in FUP phase, frequency, and amplitude produce different neural effects. Low frequencies (defined as below 300 Hz.) are inhibitory. High frequencies (defined as being in the range of 500 Hz to 5 MHz is excitatory and activate neural circuits. This works whether the target is gray or white matter. Repeated sessions result in long-term effects. The cap and transducers to be employed are preferably made of non-ferrous material to reduce image distortion in fMRI imaging. It was noted that if after treatment the reactivity as judged with fMRI of the patient with a given condition becomes more like that of a normal patient, this may be indicative of treatment effectiveness. The FUP is to be applied 1 ms to 1 s before or after the imaging. In addition a CT (Computed Tomography) scan can be run to gauge the bone density and structure of the skull. 
         [0008]    An alternative approach is described by Deisseroth and Schneider (U.S. patent application Ser. No. 12/263,026 published as US 2009/0112133 A1, Apr. 30, 2009) in which modification of neural transmission patterns between neural structures and/or regions is described using ultrasound (including use of a curved transducer and a lens) or RF. The impact of Long-Term Potentiation (LTP) and Long-Term Depression (LTD) for durable effects is emphasized. It is noted that ultrasound produces stimulation by both thermal and mechanical impacts. The use of ionizing radiation also appears in the claims. 
         [0009]    Adequate penetration of ultrasound through the skull has been demonstrated (Hynynen, K. and FA Jolesz, “Demonstration of potential noninvasive ultrasound brain therapy through an intact skull,” Ultrasound Med Biol, 1998 Feb;24(2):275-83 and Clement GT, Hynynen K (2002) A non-invasive method for focusing ultrasound through the human skull. Phys Med Biol 47: 1219-1236.). Ultrasound can be focused to 0.5 to 2 mm as TMS to 1 cm at best. 
       SUMMARY OF THE INVENTION 
       [0010]    It is the purpose of this invention to provide methods and systems and methods for patient feedback control of non-invasive deep brain or superficial neuromodulation using ultrasound impacting one or multiple points in a neural circuit to produce acute effects and, with application in multiple sessions, Long-Term Potentiation (LTP) or Long-Term Depression (LTD). One or more of ultrasound transducer positioning, frequency, intensity, and phase/intensity relationships are changed through feedback from the patient to optimize the patient experience through up-regulation or down regulation. Examples are decreases in acute pain or tremor due to more effective impact on the neural targets. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  shows a control mechanism in which the patient controls delivery parameters to optimize delivery impact. 
           [0012]      FIG. 2  illustrates a set of neural targets that are to be down-regulated using ultrasound neuromodulation under patient-feedback control to adjust acute pain. 
           [0013]      FIG. 3  shows a block diagram of the feedback control algorithm. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    It is the purpose of this invention to provide methods and systems for the adjustment of deep brain or superficial neuromodulation using ultrasound or other non-invasive modalities to impact one or multiple points in a neural circuit under patient-feedback control. 
         [0015]    The stimulation frequency for inhibition is 300 Hz or lower (depending on condition and patient). The stimulation frequency for excitation is in the range of 500 Hz to 5 MHz. In this invention, the ultrasound acoustic frequency is in range of 0.3 MHz to 0.8 MHz to permit effective transmission through the skull with power generally applied less than 180 mW/cm 2  but also at higher target- or patient-specific levels at which no tissue damage is caused. The acoustic frequency (e.g., 0.44 MHz that permits the ultrasound to effectively penetrate through skull and into the brain) is gated at the lower rate to impact the neuronal structures as desired (e.g., say 300 Hz for inhibition (down-regulation) or 1 kHz for excitation (up-regulation). If there is a reciprocal relationship between two neural structures (i.e., if the firing rate of one goes up the firing rate of the other will decrease), it is possible that it would be appropriate to hit the target that is easiest to obtain the desired result. For example, one of the targets may have critical structures close to it so if it is a target that would be down regulated to achieve the desired effect, it may be preferable to up-regulate its reciprocal more-easily-accessed or safer reciprocal target instead. The frequency range allows penetration through the skull balanced with good neural-tissue absorption. Ultrasound therapy can be combined with therapy using other devices (e.g., Transcranial Magnetic Stimulation (TMS), transcranial Direct Current Stimulation (tDCS), Deep Brain Stimulation (DBS) using implanted electrodes, implanted optical stimulation, stereotactic radiosurgery, Radio-Frequency (RF) stimulation, vagus nerve stimulation, other local stimulation, or functional stimulation). 
         [0016]    The lower bound of the size of the spot at the point of focus will depend on the ultrasonic frequency, the higher the frequency, the smaller the spot. Ultrasound-based neuromodulation operates preferentially at low frequencies relative to say imaging applications so there is less resolution. As an example, let us have a hemispheric transducer with a diameter of 3.8 cm. At a depth approximately 7 cm the size of the focused spot will be approximately 4 mm at 500 kHz where at 1 Mhz, the value would be 2 mm. Thus in the range of 0.4 MHz to 0.7 MHz, for this transducer, the spot sizes will be on the order of 5 mm at the low frequency and 2.8 mm at the high frequency. Spot size being smallest is not necessarily the most advantageous; what is optimal depends on the shape of the target neural structure. Such vendors as Keramos-Etalon and Blatek in the U.S., and Imasonic in France can supply suitable ultrasound transducers. 
         [0017]      FIG. 1  shows the basic feedback circuit. Feedback Control System  110  receives its input from User Input  120  and provides control output for positioning ultrasound transducer arrays  130 , modifying pulse frequency or frequencies  140 , modifying intensity or intensities  150 , modifying relationships of phase/intensity sets  160  for focusing including spot positioning via beam steering, modifying dynamic sweep patterns  170 , and or modifying timing patterns  180 . Feedback to the patient  190  occurs with what is the physiological effect on the patient (for example increase or decrease in pain or decrease or increase on tremor. User Input  120  can be provided via a touch screen, slider, dials, joystick, or other suitable means. 
         [0018]    An example of a multi-target neural circuit related to the processing of pain sensation is shown in  FIG. 2 . Surrounding patient head  200  is ultrasound conduction medium  290 , and ultrasound-transducer holding frame  260 . Attached to frame  260  are transducer holders  274 ,  279 ,  284 . These are oriented towards neural targets respectively holder  274  towards the Cingulate Genu  210 , holder  279  towards the Dorsal Anterior Cingulate Gyms (DACG)  230 , and holder  284  towards Insula  220 . The assembly targeting Cingulate Genu  210 , includes transducer holder  274  containing transducer  270  mounted on support  272  (possibly moved in and out via a motor (not shown)) with ultrasound field  211  transmitted though ultrasound conducting gel layer  271 , ultrasound conducting medium  290  and conducting gel layer  273  against the exterior of the head  200 . Examples of sound-conduction media are Dermasol from California Medical Innovations or silicone oil in a containment pouch. 
         [0019]    The assembly targeting Dorsal Anterior Cingulate Gyms  230 , includes transducer holder  279  containing transducer  275  mounted on support  277  (possibly moved in and out via a motor (not shown)) with ultrasound field  231  transmitted though ultrasound conducting gel layer  276 , ultrasound conducting medium  290  and conducting gel layer  278  against the exterior of the head  200 . 
         [0020]    The assembly targeting Insula  220 , includes transducer holder  284  containing transducer  280  mounted on support  282  (possibly moved in and out via a motor (not shown)) with ultrasound field  221  transmitted though ultrasound conducting gel layer  283 , ultrasound conducting medium  290  and conducting gel layer  286  against the exterior of the head  200 . 
         [0021]    The locations and orientations of the holders  274 ,  279 ,  284  can be calculated by locating the applicable targets relative to atlases of brain structure such as the Tailarach atlas or via imaging (e.g., fMRI or PET) of the specific patient. 
         [0022]    The invention can be applied to a number of conditions including, but not limited to, pain, Parkinson&#39;s Disease, depression, bipolar disorder, tinnitus, addiction, OCD, Tourette&#39;s Syndrome, ticks, cognitive enhancement, hedonic stimulation, diagnostic applications, and research functions. 
         [0023]    One or more targets can be targeted simultaneously or sequentially. Down regulation means that the firing rate of the neural target has its firing rate decreased and thus is inhibited and up regulation means that the firing rate of the neural target has its firing rate increased and thus is excited. With reference to  FIG. 2  for the treatment of pain, the Cingulate Genu  210 , and DACG  230 , and Insula  220  would all be down regulated. The ultrasonic firing patterns can be tailored to the response type of a target or the various targets hit within a given neural circuit. 
         [0024]      FIG. 3  shows an algorithm for processing feedback from the patient to control the ultrasound neuromodulation during a session  300 . Before the real-time session begins, the initial parameters sets are set  305  by the system. This can be automatically, by the user healthcare professional instructing the system, or a combination of the two. These include setting the envelope and change slopes based on selected applications and targets for positioning for targets  310 , up- and down-regulation frequencies  315 , sweeps for dynamic transducers  320 , phase/intensity relationships  325 , intensities  330 , and timing patterns  335 . These are followed by the user setting what is to be controlled by the patient during the real-time feedback, namely list of variables that are adjustable  340 , order of those variables to be adjusted  345 , and repetition period for adjustments  350 . 
         [0025]    Once the initialization is complete the real-time part of the session begins based on patient-controlled input  360  (e.g., via touch screen, slider, dials, joy stick, or other suitable mean). During real-time processing, the outer loop  365  applies for each element in selected list of adjustable variables in selected order to adjust a modification within the envelope according to the change slope under patient control with repetition at the specified interval with iteration until there is no change felt by the patient. The process includes applying to applications 1 through k  370 , applying to targets 1 through k  372 , applying to variables in designated order  374 , physical positioning (iteratively for x, y, z)  380  including adjusting aim towards target  382  and, if applicable to configuration, adjust phase/intensity relationships  384 , in addition to adjustment of configuration sweeps if there is/are dynamic transducer(s)  390 , adjust intensity  392 , and adjusting timing pattern  394 . 
         [0026]    In like manner, patient-feedback control of other modalities is possible such as control of deep-brain stimulators (DBS) using implanted electrodes, Transcranial Magnetic Stimulation (TMS), transcranial Direct Current Stimulation (tDCS), implanted optical stimulation, radio-Frequency (RF) stimulation, Sphenopalatine Ganglion Stimulation, other local stimulation, or Vagus Nerve Stimulation (VNS). 
         [0027]    The various embodiments described above are provided by way of illustration only and should not be construed to limit the invention. Based on the above discussion and illustrations, those skilled in the art will readily recognize that various modifications and changes may be made to the present invention without strictly following the exemplary embodiments and applications illustrated and described herein. Such modifications and changes do not depart from the true spirit and scope of the present invention.