Generating tumor treating fields (TTFields) with high uniformity throughout the brain
This application discloses configurations for arranging transducer arrays on a person's head to impose tumor treating fields (TTFields) in the brain at field strengths that are as uniform as possible throughout the entire brain. In some embodiments, L-shaped sets of electrodes are positioned near the right and left ears, each with a horizontal arm above the ear and a vertical arm behind the ear. Optionally, these embodiments may be combined with a second pair of electrodes positioned on top of the head and behind the neck. In other embodiments, one pair of electrodes is positioned above the right ear and on the left/rear portion of the neck; and a second pair of electrodes is positioned above the left ear and on the right/rear portion of the neck. These configurations improve the uniformity of the electric fields imposed throughout the brain, and are particularly useful for preventing and/or treating metastases.
1. A method of applying an alternating electric field to a brain in a person's body, the body having a mid-coronal plane and a mid-sagittal plane, the method comprising:
affixing a first set of electrode elements to the person's head on a right side of the mid-sagittal plane, superior to the external opening of the person's right ear canal;
affixing a second set of electrode elements having a second centroid to the person's body on a left side of the mid-sagittal plane and behind the mid-coronal plane, with the second centroid positioned inferior to an external opening of the person's left ear canal, and superior to the person's C7 vertebra;
affixing a third set of electrode elements to the person's head on a left side of the mid-sagittal plane, superior to the external opening of the person's left ear canal;
affixing a fourth set of electrode elements having a fourth centroid to the person's body on a right side of the mid-sagittal plane and behind the mid-coronal plane, with the fourth centroid positioned inferior to an external opening of the person's right ear canal, and superior to the person's C7 vertebra; and
repeating, in an alternating sequence (a) applying an alternating voltage between the first set of electrode elements and the second set of electrode elements, and (b) applying an alternating voltage between the third set of electrode elements and the fourth set of electrode elements,
wherein the repeating is performed after affixing the first, second, third, and fourth sets of electrode elements.
2. The method of claim 1 , wherein the second centroid and the fourth centroid are positioned superior to a midpoint of the person's C2 vertebra.
3. The method of claim 1 , wherein the second centroid and the fourth centroid are positioned inferior to a midpoint of the person's C2 vertebra.
4. The method of claim 1 , wherein the second centroid and the fourth centroid are positioned inferior to the person's C3 vertebra and superior to the person's C6 vertebra.
5. The method of claim 1 , wherein the specific locations at which the first, second, third, and fourth sets of electrode elements are affixed to the person's body are determined by
running finite element simulations for an individual person to calculate a resulting electric field for each combination of positions for the first, second, third, and fourth sets of electrode elements, and
selecting the combination of positions for the first, second, third, and fourth sets of electrode elements that results in the lowest value of ψ, where ψ=σ T ÷MEAN T , σ T =SD([μ i ]|i ∈ {α, β, γ, δ, in}), and MEAN T =mean([μ i ]|i ∈ {α, β, γ, δ, in}).
6. The method of claim 1 , wherein the alternating voltage has a frequency between 100 and 300 kHz.
7. A method of determining where to position a set of electrode elements on a person's body before the set of electrodes is used to apply an alternating electric field to a brain in the person's body, the body having a mid-coronal plane and a mid-sagittal plane, the method comprising:
(a) simulating affixation of a first set of electrode elements to the person's head at a first plurality of positions on a right side of the mid-sagittal plane, superior to the external opening of the person's right ear canal;
(b) simulating affixation of a second set of electrode elements having a second centroid to the person's body at a second plurality of positions on a left side of the mid-sagittal plane and behind the mid-coronal plane, with the second centroid positioned inferior to an external opening of the person's left ear canal, and superior to the person's C7 vertebra;
(c) simulating affixation of a third set of electrode elements to the person's head at a third plurality of positions on a left side of the mid-sagittal plane, superior to the external opening of the person's left ear canal;
(d) simulating affixation of a fourth set of electrode elements having a fourth centroid to the person's body at a fourth plurality of positions on a right side of the mid-sagittal plane and behind the mid-coronal plane, with the fourth centroid positioned inferior to an external opening of the person's right ear canal, and superior to the person's C7 vertebra;
(e) simulating application of an alternating voltage between the first set of electrode elements and the second set of electrode elements at each of the first plurality of positions and at each of the second plurality of positions, respectively;
(f) simulating application of an alternating voltage between the third set of electrode elements and the fourth set of electrode elements at each of the third plurality of positions and at each of the fourth plurality of positions, respectively;
(g) determining, based on steps (e) and (f), which of the first plurality of positions, which of the second plurality of positions, which of the third plurality of positions, and which of the fourth plurality of positions results in an alternating electric field in the person's brain with high uniformity; and
(h) outputting, based on a result of step (g), a recommended position for the first set of electrode elements, a recommended position for the second set of electrode elements, a recommended position for the third set of electrode elements, and a recommended position for the fourth set of electrode elements.
8. The method of claim 7 , wherein the simulated affixation has the second centroid and the fourth centroid positioned superior to a midpoint of the person's C2 vertebra.
9. The method of claim 7 , wherein the simulated affixation has the second centroid and the fourth centroid positioned inferior to a midpoint of the person's C2 vertebra.
10. The method of claim 7 , wherein the simulated affixation has the second centroid and the fourth centroid positioned inferior to the person's C3 vertebra and superior to the person's C6 vertebra.
11. The method of claim 7 , wherein step (g) comprises selecting the combination of positions for the first, second, third, and fourth sets of electrode elements that results in the lowest value of ψ, where ψ=σ T ÷MEAN T , σ T =SD([μ i ]|i ∈ {α, β, γ, δ, in}), and MEAN T =mean([μ i ]|i ∈ {α, β, γ, δ, in}).