Reducing Electrosensation When Treating a Subject Using a Rotating Alternating Electric Field by Gradually Increasing the Amplitude of the Field
When transducer arrays (i.e., arrays of electrode elements) are used to apply alternating electric fields (e.g., tumor treating fields or TTFields) to a subject's body, the subject may experience electrosensation. This electrosensation can be ameliorated by changing the way the voltage increases from zero to its peak when the AC voltage is initially applied to the transducer arrays.
1 . A method of selectively destroying or inhibiting the growth of rapidly dividing cells located within a target region of a subject's body, comprising the steps of:
imposing an AC electric field in the target region with a field orientation that rotates with respect to the target region, wherein the electric field has a frequency between 50 kHz and 1 MHz,
wherein the electric field has an amplitude that increases from an initial level to a final level over the course of at least 0.1 s.
2 . The method of claim 1 , wherein when the amplitude of the electric field is at the final level, the electric field has a field strength of at least 1 V/cm in at least a portion of the target region.
3 . The method of claim 1 , wherein the electric field is imposed in the target region via insulated electrodes.
4 . The method of claim 1 , wherein the electric field has an amplitude that increases from the initial level to the final level over the course of at least 1 s.
5 . The method of claim 4 , wherein when the amplitude of the electric field is at the final level, the electric field has a field strength of at least 5 V/cm in at least a portion of the target region.
6 . The method of claim 1 , wherein the electric field has an amplitude that increases from the initial level to the final level over the course of at least 0.3 s, wherein when the amplitude of the electric field is at the final level, the electric field has a field strength of at least 5 V/cm in at least a portion of the target region, and wherein the frequency of the electric field is between 80 kHz and 300 kHz.
7 . The method of claim 1 , wherein the frequency of the electric field is between 80 kHz and 300 kHz.
8 . The method of claim 1 , wherein the electric field has an amplitude that remains at the final level for at least 100 s.
9 . The method of claim 1 , wherein the rotation of the AC electric field is accomplished by simultaneously applying AC voltages having different phases to at least three electrodes.
10 . The method of claim 1 , wherein the increase in amplitude from the initial level to the final level is linear.
11 . An apparatus for selectively destroying or inhibiting the growth of rapidly dividing cells located within a target region of a subject's body, the apparatus comprising:
at least three electrodes, each of which has a surface configured for placing against the subject's body; and
an AC voltage source having at least three outputs, each output being electrically connected to a respective one of the electrodes,
wherein each of the at least three outputs has a frequency between 50 kHz and 1 MHz, and
wherein each of the at least three outputs has an amplitude that increases from an initial level to a final level of at least 50 V RMS over the course of at least 0.1 s.
12 . The apparatus of claim 11 , wherein each of the at least three outputs has an amplitude that remains at the final level for at least 30 s.
13 . The apparatus of claim 11 , wherein each of the at least three electrodes comprises a conductive substrate, and
wherein each of the surfaces configured for placing against the subject's body comprises an insulating material having a dielectric constant of at least 20 disposed on a respective conductive substrate.
14 . The apparatus of claim 11 , wherein each of the at least three outputs has an amplitude that increases from the initial level to the final level over the course of at least 1 s, and
wherein the final level is at least 100 V RMS.
15 . The apparatus of claim 14 , wherein each of the at least three outputs has a frequency between 80 kHz and 300 kHz.
16 . The apparatus of claim 11 , wherein each of the at least three outputs has a frequency between 80 kHz and 300 kHz.
17 . The apparatus of claim 11 , wherein the AC voltage source has a first output at a given frequency, a second output at the given frequency that is offset by 120° with respect to the first output, and a third output at the given frequency that is offset by 240° with respect to the first output.
18 . The apparatus of claim 11 , wherein the AC voltage source has a first output at a given frequency, a second output at the given frequency that is offset by 90° with respect to the first output, a third output at the given frequency that is offset by 180° with respect to the first output, and a fourth output at the given frequency that is offset by 270° with respect to the first output.
19 . The apparatus of claim 11 , wherein the AC voltage source simultaneously applies sinusoidal signals at a first frequency to each of the at least three outputs, wherein the signals applied to each of the at least three outputs are modulated by sinusoids at a second frequency that is at least ten times lower than the first frequency, and the modulating sinusoids are phase shifted.
20 . The apparatus of claim 11 , wherein the increase in amplitude from the initial level to the final level is linear.