Reducing electrosensation during application of alternating electric fields by ensuring that successive increases in amplitude occur during opposite phases of an AC waveform
When transducer arrays (i.e., arrays of electrode elements) are used to apply alternating electric fields to a subject's body, the subject may experience electrosensation, particularly during portions of the waveform where the amplitude of the AC voltage is ramping up. This electrosensation can be ameliorated by synchronizing the step-to-step transitions in amplitude with the AC signal so that when a given step-to-step transition occurs while the AC signal has a given polarity, the very next step-to-step transitions will occur while the AC signal has the opposite polarity.
1 . A method of ameliorating electrosensation while applying an electric field to a target region in a living body, the method comprising:
applying an alternating electric field having frequency between 50 kHz and 1 MHz to the target region; and
increasing an amplitude of the alternating electric field in a stepwise manner, wherein the stepwise increase in amplitude includes at least 10 steps,
wherein each step of the stepwise increase in amplitude is synchronized with the alternating electric field such that when a given step increases the amplitude of the alternating electric field while the alternating electric field has a given polarity, an immediately subsequent step will increase the amplitude of the alternating electric field while the alternating electric field has a polarity that is opposite to the given polarity.
2 . The method of claim 1 , wherein each step of the stepwise increase in amplitude is synchronized with the alternating electric field such that when a given step increases the amplitude of the alternating electric field while the alternating electric field has a given instantaneous value X G , an immediately subsequent step will increase the amplitude of the alternating electric field while the alternating electric field has an instantaneous value of −X G , ±20%.
3 . The method of claim 1 , wherein each step of the stepwise increase in amplitude is synchronized with the alternating electric field such that when a given step increases the amplitude of the alternating electric field while the alternating electric field is operating at a given phase φ G , an immediately subsequent step will increase the amplitude of the alternating electric field while the alternating electric field is operating at a phase of φ G +180°, ±10°.
4 . The method of claim 1 , wherein the alternating electric field has a frequency between 75 kHz and 500 kHz.