Arrays for delivering tumor treating fields (TTFields) with individually accessible electrode elements and temperature sensors
Tumor treating fields (TTFields) can be delivered to a subject's body at higher field strengths by switching off one or more electrode elements in a transducer array that are overheating. This may be accomplished by using thermistors that sense the temperature of each electrode element. Portions of the wiring of each transducer array is shared between the electrode elements and the thermistors by using a plurality of conductors, each of which electrically connects (a) a pin of a connector, (b) a respective electrode element, and (c) a respective thermistor. In some embodiments, all of the thermistors are wired in series. In other embodiments, all the thermistors share a common connection.
1. An apparatus for applying an alternating electric field to a subject's body using a plurality of electrode elements, wherein each of the plurality of electrode elements is disposed in thermal contact with a respective thermistor, the apparatus comprising:
an AC signal generator that generates an AC output signal;
a connector that includes a plurality of pins, wherein each of the pins corresponds to a respective one of the plurality of electrode elements;
a first plurality of switches, wherein each of the first plurality of switches is configured to selectively either apply or not apply the AC output signal to a respective one of the pins;
an amplifier configured to accept an electrical signal from each of the thermistors and generate a corresponding output, wherein the electrical signals from the thermistors arrive via the same pins that correspond to the plurality of electrode elements; and
a controller configured to, based on the output of the amplifier, control the first plurality of switches so as to individually adjust the duty cycle of the AC signal that is applied to each of the plurality of pins.
2. The apparatus of claim 1 , wherein the controller is configured to (a) determine, based on the output of the amplifier, when at least one of the electrode elements is hotter than other electrode elements and (b) control the first plurality of switches so as to reduce the duty cycle of the AC signal that is applied to at least one respective pin.
3. The apparatus of claim 1 , wherein the controller is configured to (a) determine, based on the output of the amplifier, when at least one of the electrode elements is hotter than a threshold level and (b) control the first plurality of switches so as to reduce the duty cycle of the AC signal that is applied to at least one respective pin.
4. The apparatus of claim 1 , wherein the plurality of electrode elements comprises at least four electrode elements, wherein the plurality of pins comprises at least four pins, and wherein the first plurality of switches comprises at least four switches.
5. The apparatus of claim 1 , wherein the plurality of electrode elements comprises at least nine electrode elements, wherein the plurality of pins comprises at least nine pins, and wherein the first plurality of switches comprises at least nine switches.
6. The apparatus of claim 1 , further comprising a second plurality of switches, each of which is arranged to route a signal from a respective one of the plurality of pins to a first input of the amplifier,
wherein the controller is further configured to control the second plurality of switches so as to sequentially select each of the plurality of pins and to sequentially obtain temperature readings from each of the thermistors.
7. The apparatus of claim 6 , wherein the connector includes an additional pin, and wherein the apparatus further comprises an additional switch arranged to route a signal from the additional pin to a second input of the amplifier.
8. The apparatus of claim 7 , further comprising a third plurality of switches, each of which is arranged to route a signal from a respective one of the plurality of pins to the additional pin, and
wherein the controller is further configured so that when a given switch from the first plurality of switches is opened, the controller closes a respective corresponding switch from the third plurality of switches.
9. The apparatus of claim 1 , further comprising:
a second plurality of switches, each of which is arranged to route a signal from a respective one of the plurality of pins to a first input of the amplifier; and
a third plurality of switches, each of which is arranged to route a signal from a respective one of the plurality of pins to a second input of the amplifier,
wherein the controller is further configured to control the second plurality of switches and the third plurality of switches so as to sequentially route signals to the first and second inputs of the amplifier from pairs of the plurality of pins that correspond to both terminals of each of the thermistors in turn, and to sequentially obtain temperature readings from each of the thermistors.