Using staggered changes in amplitude and frequency to ameliorate electrosensation during treatment with alternating electric fields
When transducer arrays (i.e., arrays of electrode elements) are used to apply alternating electric fields (e.g., TTFields) to a subject's body, the subject may experience electrosensation. This electrosensation can be ameliorated by (a) increasing the amplitude of the field in a series of steps, and allowing some time to pass for the subject to acclimate to each step before the amplitude is increased to the next-higher value, (b) starting out at a frequency that is higher than the recommended frequency for each indication (e.g., higher than 200 kHz for treating glioblastoma), subsequently decreasing the frequency to the recommended frequency in a series of steps, and allowing some time to pass for the subject to acclimate to each step before the frequency is decreased to the next-lower value, and (c) avoiding (or at least minimizing) situations in which an increase in amplitude and a decrease in frequency occur simultaneously.
1 . An apparatus for applying electrical signals to first, second, third and fourth sets of at least one electrode element, the apparatus comprising:
an AC signal generator having a first output for applying an AC voltage between the first set of at least one electrode element and the second set of at least one electrode element, a second output for applying an AC voltage between the third set of at least one electrode element and the fourth set of at least one electrode element, and at least one control input, wherein the AC signal generator is configured so that the at least one control input controls an amplitude of the first output, a frequency of the first output, an amplitude of the second output, and a frequency of the second output; and
a controller configured to apply a sequence of control signals to the at least one control input of the AC signal generator, wherein the sequence of control signals controls the AC signal generator so that (a) when the first output is activated at a given time, the first output has an initial amplitude and an initial frequency, (b) at a first set of times that follow the given time while the first output remains active, the amplitude of the first output increases while the frequency of the first output remains constant, and (c) at a second set of times that follow the given time while the first output remains active, the frequency of the first output decreases while the amplitude of the first output remains constant, wherein the first set of times and the second set of times are mutually exclusive,
wherein the sequence of control signals further controls the AC signal generator so that (a) when the second output is activated at a certain time, the second output has an initial amplitude and an initial frequency, (b) at a third set of times that follow the certain time while the second output remains active, the amplitude of the second output increases while the frequency of the second output remains constant, and (c) at a fourth set of times that follow the certain time while the second output remains active, the frequency of the second output decreases while the amplitude of the second output remains constant, wherein the third set of times and the fourth set of times are mutually exclusive, and
wherein the sequence of control signals causes the AC signal generator to (i) activate the first output for an interval of time, (ii) subsequently activate the second output for an interval of time, and (iii) subsequently repeat (i) and (ii) at least 10 times in an alternating sequence, whereby there will be at least 10 activations of the first output and at least 10 activations of the second output,
wherein each of the at least 10 activations of the first output corresponds to a respective first set of times and a respective second set of times, and
wherein each of the at least 10 activations of the second output corresponds to a respective third set of times and a respective fourth set of times.
2 . The apparatus of claim 1 , wherein each of the respective first sets of times includes at least 10 times, each of the respective second sets of times includes at least 3 times, each of the respective third sets of times includes at least 10 times, and each of the respective fourth sets of times includes at least 3 times.
3 . The apparatus of claim 1 , wherein each of the respective first sets of times includes at least 50 times, each of the respective second sets of times includes at least 3 times, each of the respective third sets of times includes at least 50 times, and each of the respective fourth sets of times includes at least 3 times.
4 . The apparatus of claim 1 , wherein each interval of time when the first output is activated has a duration of at least 800 ms, and
wherein each interval of time when the second output is activated has a duration of at least 800 ms.
5 . The apparatus of claim 1 , wherein the first sets of times and the second sets of times are interspersed with each other, and
wherein the third sets of times and the fourth sets of times are interspersed with each other.
6 . The apparatus of claim 1 , wherein the initial frequency of the first output is at least 50% higher than a final frequency of the first output, and
wherein the initial frequency of the second output is at least 50% higher than a final frequency of the second output.
7 . The apparatus of claim 6 , wherein the final frequency of the first output is between 75 kHz and 300 kHz, and
wherein the final frequency of the second output is between 75 kHz and 300 kHz.
8 . The apparatus of claim 1 , wherein each of the respective first sets of times includes at least 50 times, each of the respective second sets of times includes at least 3 times, each of the respective third sets of times includes at least 50 times, and each of the respective fourth sets of times includes at least 3 times,
wherein each interval of time when the first output is activated has a duration of at least 2 seconds,
wherein each interval of time when the second output is activated has a duration of at least 2 seconds,
wherein the first sets of times and the second sets of times are interspersed with each other,
wherein the third sets of times and the fourth sets of times are interspersed with each other,
wherein the initial frequency of the first output is at least 50% higher than a final frequency of the first output, and
wherein the initial frequency of the second output is at least 50% higher than a final frequency of the second output.
9 . The apparatus of claim 8 , wherein the final frequency of the first output is between 75 kHz and 300 kHz, and
wherein the final frequency of the second output is between 75 kHz and 300 kHz.
10 . An apparatus for applying electrical signals to first and second sets of at least one electrode element, the apparatus comprising:
an AC signal generator having (i) an output for applying an AC voltage between the first set of at least one electrode element and the second set of at least one electrode element and (ii) at least one control input, wherein the AC signal generator is configured so that the at least one control input controls an amplitude of the output and a frequency of the output; and
a controller configured to apply a sequence of control signals to the at least one control input of the AC signal generator, wherein the sequence of control signals controls the AC signal generator so that (a) when the output is activated at a given time, the output has an initial amplitude and an initial frequency, (b) at a first set of times that follow the given time while the output remains active, the amplitude of the output increases while the frequency of the output remains constant, and (c) at a second set of times that follow the given time while the output remains active, the frequency of the output decreases while the amplitude of the output remains constant, wherein the first set of times and the second set of times are mutually exclusive,
wherein the first set of times includes at least 10 times,
wherein the second set of times includes at least 3 times,
wherein the first set of times and the second set of times are interspersed with each other,
wherein the initial frequency of the output is at least 50% higher than a final frequency of the output, and
wherein the final frequency of the output is between 75 kHz and 300 kHz.