B.Sc. final project · University of Tehran · ICEE 2026

PM-TI

Sharper deep-brain stimulation.
No surgery. No new hardware.

StudentHassan Keshtkar

SupervisorDr. Hoda Ameri

SchoolECE · University of Tehran

PaperICEE 2026

scroll · or press →

Problem · 01

Millions live with a brain that misfires.

When the drugs stop working, the target sits deep inside the brain.

Gowers' 1886 sketch of Parkinson's disease — **Parkinson's**8.5 M+ people

Spiral drawing test of an essential-tremor patient — **Essential tremor**~1 in 100

EEG 3 Hz spike-and-wave discharge — **Epilepsy**50 M people

Solution · 01

Deep Brain Stimulation works.

Electrodes at the target. The tremor stops.

Solution · 01

A few volts, right where it matters.

Parkinson's · tremor · dystonia · epilepsy — in clinics since the 90s.

Problem · 02

But it needs brain surgery.

skull openinginfection · bleedinghardware for life

Lateral skull X-ray with two DBS leads — **X-ray** · two DBS leads · CC BY-SA

Solution · 02

Temporal Interference.

Stimulate deep — from the scalp.

Solution · 02

Two kHz fields. Neurons ignore each one.

2000 Hz from one pair, 2010 Hz from the other.

Solution · 02

Where they meet, a 10 Hz beat is born.

Neurons follow the beat — only where both fields overlap.

Solution · 02 · in two lines

Two frequencies, one beat.

TI · 1

s_{1} (t) = E_{1} \cos (ω_{1} t), s_{2} (t) = E_{2} \cos (ω_{2} t), ω_{2} = ω_{1} + Δ ω

TI · 2 · envelope

{| E_{AM} |}_{TI} = 2 \min (E_{1}, E_{2})

The weaker field sets the envelope. Nothing else.

E₁ · 2000 Hz

E₂ · 2010 Hz

E₁ + E₂envelope · 10 Hz

200 ms

Problem · 03

The hotspot is wide.

≈ 30 mm across a 70 mm phantom. The neighbours get stimulated too.

more electrodes more channels bigger hardware → a smarter waveform

k = 1 · conventional TI · |E_AM,y|

01 · envelope

Solution · 03 · our work · ICEE 2026

PM-TI: one carrier, opposite phase modulation.

PM-TI · 1

s_{1} (t) = E_{1} \cos (ω_{c} t + φ (t)), s_{2} (t) = E_{2} \cos (ω_{c} t - φ (t))

φ (t) = \arccos (\frac{\cos (ω_{m} t)}{k}), k \geq 1, ω_{m} ≪ ω_{c}

envelope · E₁ ≠ E₂

E₂ / E₁0.60

Unequal fields get penalised. k turns the penalty up.
No new electrodes — a new waveform.

Solution · 03 · one number to tune

Turn k up. The focus tightens.

Same electrodes. Same current. Same peak.

1.00

k · focusing parameter

29.5mm

FWHM · along y = 0

1 3

|E_AM,y| · live · auto, or drag the slider

Results · simulation · 70 mm phantom

Same peak. A third of the width.

k = 1 · conventional TI

k = 2 · PM-TI

k = 3 · PM-TI

0.0mm

FWHM · k = 1

0.0mm

FWHM · k = 2

−53 %

0.0mm

FWHM · k = 3

−69 %

envelope along y = 0k=1k=2k=3

peak change < 0.5 %

Live · sweep along x · compare the envelope

Off-centre, the beat dies faster with k.

k = 1

V/m

|E_AM|—

k = 2

V/m

|E_AM|—

k = 3

V/m

|E_AM|—

x · mm · along y = 0

x = 0.0 mm

drag on any map or the profile to scrub

Results · measurement

We built it. We measured it.

Bench test: saline phantom, probe, oscilloscope showing the 10 Hz beat — **21 Aug 2026** · test day · the beat on the scope

Probe in the saline phantom — probe · 10 mm pitch

phantom70 mm saline

scan7 × 7 · 49 points

carrier · beat2005 Hz · 10 Hz

runsk = 1 · 2 · 3

Results · simulation vs. measurement

The phantom agrees.

k = 1

k = 2

k = 3

simulation

measurement

0.00

correlation · simulation vs measurement

0.0mm

measured FWHM · k = 2 · from 33.9 mm

−49 %

0.0mm

measured FWHM · k = 3 · from 33.9 mm

−58 %

recorded at the centre · k = 3 · band-passed

240 ms

PM-TI · phase-modulated temporal interference

Sharper. Non-invasive.
Software-only.

Same electrodes. Same current. A third of the footprint.

−69%

focus width

surgery

new electrodes

StudentHassan Keshtkar

SupervisorDr. Hoda Ameri

School of ECEUniversity of Tehran

PaperICEE 2026

scan · this page, live hkk.fyi/pmti

PM-TI

Millions live with a brain that misfires.

Deep Brain Stimulation works.

A few volts, right where it matters.

But it needs brain surgery.

Temporal Interference.

Two kHz fields. Neurons ignore each one.

Where they meet, a 10 Hz beat is born.

Two frequencies, one beat.

The hotspot is wide.

PM-TI: one carrier, opposite phase modulation.

Turn k up. The focus tightens.

Same peak. A third of the width.

Off-centre, the beat dies faster with k.

We built it. We measured it.

The phantom agrees.

Sharper. Non-invasive.Software-only.

Sharper. Non-invasive.
Software-only.