Transcranial Focused Ultrasound for BOLD fMRI Signal Modulation in Humans

Leo Ai, Jerel K. Mueller, Andrea Grant, Yigitcan Eryaman, Wynn Legon

arXiv 2016 · 10.48550/arxiv.1603.00415

human healthyhealthyfmri

Abstract

Transcranial focused ultrasound (tFUS) is an emerging form of non-surgical human neuromodulation that confers advantages over existing electro and electromagnetic technologies by providing a superior spatial resolution on the millimeter scale as well as the capability to target sub-cortical structures non-invasively. An examination of the pairing of tFUS and blood oxygen level dependent (BOLD) functional MRI (fMRI) in humans is presented here.

Abstract via datacite.

Specieshuman

Subjects6, 1swept participants

Sessions per subjectnot reported

Randomisednot reported

Blindingnot reported

Sham / controlnone

Auditory controlnot reported

Readout timingonline

Anaesthesianot applicable

Readoutsfmri — BOLD GRE-EPI at 3T; 7T pilot

Direction of effectmixed or unclearFocal BOLD responses at the sonication focus in 3 of 6 participants at 3T (no group effect) and in one participant at 7T (caudate).

Adverse eventsnot reportedTransducer surface heating tested on an agar phantom in the scanner (about 1 degC rise); no safety observations in participants reported.

Exposures

Exposure 1: 3T: primary motor cortex hand knob, 0.5 MHz

Target: primary motor cortex — “primary motor cortex hand knob of the dominant hemisphere”
Device: not reported

Pulse timing
Waveform	pulsed
Fundamental frequency (kHz)	500	✓✓✓
Pulse duration (ms)	0.36	✓✓✓⚑
Pulse repetition frequency (Hz)	1,000	✓✓✓
Duty cycle (%)	36pulse duration × PRF gives 36%	✓✓✓⚑
Sonication duration (s)	0.5	✓✓✓

Pressure and intensity, by domain
Free-field pressure (kPa)	not reported
Free-field Isppa (W/cm²)	not reported
Free-field Ispta (W/cm²)	not reported
In-situ estimate	measurementsingle value
In-situ pressure (kPa)	not reported
In-situ Isppa (W/cm²)	6	✓✓✓⚑
In-situ Ispta (W/cm²)	not reported

Protocol, in the paper’s words

180 cycles of the 0.5 MHz acoustic frequency were pulsed at 1 KHz (36% duty cycle); 500 cycles of the PRF delivered, a 500 ms stimulus. Event-related design: 90 stimuli of 0.5 s delivered every 6-7 TRs (12-14 s).

Exposure 2: 7T: left head of caudate, 0.86 MHz

Target: caudate nucleus — “left head of caudate”
Device: not reported

Pulse timing
Waveform	pulsed
Fundamental frequency (kHz)	860	✓✓✓
Pulse duration (ms)	0.488	✓✓✓
Pulse repetition frequency (Hz)	1,000	✓✓✓
Duty cycle (%)	50pulse duration × PRF gives 48.8%	✓✓✓
Sonication duration (s)	0.5	✓✓✓

Pressure and intensity, by domain
Free-field pressure (kPa)	not reported
Free-field Isppa (W/cm²)	not reported
Free-field Ispta (W/cm²)	not reported
In-situ estimate	measurementsingle value
In-situ pressure (kPa)	not reported
In-situ Isppa (W/cm²)	6	✓✓✓
In-situ Ispta (W/cm²)	not reported

Protocol, in the paper’s words

420 cycles of the 0.86 MHz acoustic frequency (50% duty cycle) pulsed at 1 KHz with a 500 ms duration. Block design, 5 off/on cycles, stimulation delivered every 6 TRs during on cycles.

Flags from extraction

n_subjects — Total never stated; 6 participants at 3T and 1 volunteer at 7T given as group sizes.
exposures[0].timing.pulse_duration_ms — Pulse duration not stated in ms; 180 cycles at 0.5 MHz and 420 cycles at 0.86 MHz stated instead. Left not_reported.
exposures[0].in_situ.isppa_w_cm2 — Isppa of 6 W/cm2 was set after transmission through a 6 mm fragment of human parietal bone in a water tank, not in a brain; recorded as in_situ measurement. Same value stated for both transducers.
exposures[0].timing.duty_cycle_pct — Text states 36% for 180 cycles at 0.5 MHz and 1 KHz PRF (arithmetically 18%); recorded as stated.
exposures[0].device.family — Transducers not attributed to a maker in the text for the exposures; only tank hydrophone and function generator named.

Notes: Conference-style paper (arXiv 1603.00415); not checked against E8 here.