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Content uploaded by Charlie Demené
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All content in this area was uploaded by Charlie Demené on May 03, 2018
Content may be subject to copyright.
Functional Ultrasound Imaging of the Brain Activity
in Human Neonates
Charlie Demene1, Miguel Bernal1, Catherine Delanoe2, Stéphane Auvin3, Valérie Biran4, Marianne Alison5, Jérome
Mairesse6, Elisabeth Harribaud2, Mathieu Pernot1, Mickael Tanter1*, Olivier Baud4,6*.
1 Institut Langevin, CNRS UMR 7587, Inserm U979, ESPCI Paris, PSL Research University, 75005 Paris, France. 2 Assistance
Publique - Hôpitaux de Paris, Neurophysiology Unit, Robert Debré University Hospital, 75019 Paris, France. 3 Assistance
Publique - Hôpitaux de Paris, Pediatric Neurology Department, Robert Debré University Hospital, 75019 Paris, France.
4 Assistance Publique - Hôpitaux de Paris, Neonatal Intensive Care Unit, Robert Debré University Hospital, 75019 Paris, France.
5 Assistance Publique - Hôpitaux de Paris, Pediatric Radiology Department, Robert Debré University Hospital, 75019 Paris,
France. 6 Institut National de la Santé et de la Recherche Médicale (Inserm) U1141, 75019 Paris, France.
Abstract—The recent introduction of functional ultrasound
(fUS) based on ultrafast Doppler imaging for blood flow
detection unveiled a gigantic field of applications in
Neuroimaging. Its considerable sensitivity, temporal and spatial
resolution enabled to image the neurovascular coupling in
unprecedented situations such as olfactory stimulation or spatial
representation in an awake animal. However, to date those
applications have been restricted to small animal studies. Here
we present for the first time fUS imaging in human. We were
able to image a broad spectrum of cerebral activity in neonates,
from quiet sleep to epileptic seizures, and we could even detect
undescribed phenomenon under the form of slowly propagating
vascular changes.
Keywords— fUS, functional ultrasound imaging, epilepsy,
ultrafast Doppler, brain.
I. INTRODUCTION
Functional neuroimaging in clinical setting is to date very
limited, since the use of functional-capable modalities is
challenging at bedside. NIRS and EEG are portable devices
and provide useful information, but their spatial resolution is
poor, and fMRI systems are expensive, with limited
availability, and non-adapted for a large scope of applications
from neonate imaging to surgical imaging. Recently, the use of
ultrasonic plane waves transmitted at ultrafast frame rates was
shown to increase up to 50 times the sensitivity of ultrasound to
blood flow [1]. This new Ultrafast Doppler (UfD) imaging
modality was shown to enable the spatiotemporal description
of brain activation through neurovascular coupling in rodents
[2]. Functional ultrasound imaging (fUS) enabled high
temporal (ms) and spatial (100µm) imaging of somatosensory
[2] and olfactory responses [3], of epileptic seizures [4], resting
state connectivity [5] and spatial representation [4]. However,
to date those applications have been restricted to small animal
studies. Here we show for the first time fUS imaging in human.
We show that using an in-house light weight portable probe,
fUS imaging along with simultaneous EEG recording is
feasible on neonates, at bedside, during long periods of time
and without any discomfort for the patient. fUS imaging was
capable of detecting slight variation of cerebral blood volume
correlated with burst of electrical activity on the EEG in quiet
sleep in healthy neonates, and also to image spatiotemporal
dynamics of unilateral seizures in a pathological case.
II. MATERIALS AND METHODS
A. Patient recruitment
The study was approved by the local institutional review
boards and ethical committee (Comité de Protection des
Personnes (CPP) “Ile-de-France II”, protocol #120601, ID-
RCB #2012-A01530-43), and strictly complies with the ethical
principles for medical research involving human subjects of the
World Medical Association Declaration of Helsinki, and
written consent was obtained from parents of all patients.
Examinations were conducted at bedside, with minimal
discomfort for recruited neonates: setting the complete headset
This work was supported by a research grant from the European Research
Council under the European Union's Seventh Framework Programme
(FP7/2007-2013) / ERC Advanced grant agreement n° 339244-
FUSIMAGINE), the ANR-10-IDEX-0001-02 PSL* and support from Institut
N
ational de la Santé et de la Recherche Médicale (Inserm), PremUp
Foundation, and sponsored by the Département de la Recherche Clinique et du
Développement, Assistance Publique-Hôpitaux de Paris.
Fig. 1. a. Custom compact ultrasonic probe, 50 euro cent coin is given
for scale. b. The probe is inserted in the in-house made biocompatible
mount, enable one rotation degree of freedom. c. EEG+fUS (+ video and
audio recording) can monitor a neonate at bedside. d. Ultrasonic probe
and EEG electrodes setup on a pathological neonate.
(UfD-EEG) required at most 10 minutes and all patients were
then free to move.
B. Ultrafast Doppler imaging
A custom probe (8-MHz central frequency, 0.3-mm pitch,
128 elements, and 80-% bandwidth) (Vermon, France)(Fig.1
a.) was inserted into an in-house device consisting in a semi-
rigid biocompatible silicon mount enabling single-plan pivot
(Fig.1 b.), filled with ultrasound gel for acoustic coupling. This
device was held together with EEG electrodes using soft non-
adhesive strips. The probe was placed against the anterior
fontanel and directed toward the brain region of interest using
the pivot.
C. EEG recording
An EEG system (Nihon Kohden EEG1200, Cachan,
France) was used to record an 8 channel EEG (Fig.1 c.), the 8
electrodes placed on the scalp around the ultrasonic probe
being localized in the standard 10-20 EEG assembly (Fig.1 d.).
D. Synchronisation
EEG recording and UfD acquisitions (AixplorerTM research
platform, Supersonic Imagine, France) were electronically
synchronized using a triggering signal sent from the
AixplorerTM system to the EEG acquisition system.
Continuous and synchronized video recordings of the patients
were also obtained to compare clinical events and UfD/EEG
data.
E. Ultrasound sequences
Ultrasonic plane wave transmissions with 3 tilted angles
(angles -3° 0° 3°) were fired at a 3-kHz pulse repetition
frequency (PRF) during 600 ms. Sets of 3 backscattered echoes
recorded for each tilted transmission were then processed on
the fly using an in-house GPU-based beamformer and
coherently compounded [6] in order to produce high-quality
images at a 1-kHz ultrafast frame rate. These stacks of 600
ultrafast images were then saved to disk for further off-line
processing. This process could be repeated once per second.
F. Post Processing
Ultrafast imaging datasets were filtered to remove clutter
filtering and motion artefacts using a dedicated
multidimensional spatiotemporal filter based on singular value
decomposition [7]. This strategy was shown to strongly
outperform conventional clutter filters, and is a requirement for
ultrasensitive Doppler imaging in such a clinical setting (with
brain pulsatile motion, probe motion, breathing motion,
neonate moderate motion, slow blood flow detection). After
filtering, Power Doppler images were computed in order to be
quantitative and proportional to blood volume.
To obtain a temporal profile of brain activation, this Power
Doppler signal is normalized toward its value during a baseline
period of time (light sleep or inter-ictal periods for epileptic
activity) to give a relative variation in percent. This values can
be averaged in Regions of Interest (ROI) or used as dynamic
relative blood volume variation maps.
III. RESULTS
A. Quiet Sleep fUS Imaging
Sleep in neonates is characterized by alternating phases
known as active and quiet sleep. While active sleep is
characterized by a continuous EEG activity with mixed delta
and theta frequencies, EEG during quiet sleep is predominantly
discontinuous, with bursts of 50-200µV electrical activity
separated by inter-bursts of very low energy), a feature known
as “tracé alternant”.
We performed fUS+EEG at bedside on unrestrained full-
term sleeping neonates and without any sedative drugs, and
fUS images were obtained in a coronal plane through the
anterior fontanel. The time course of the average cortical UfD
signal during quiet sleep in both ROIs was compared to EEG
recordings obtained on 8 channels during this same time period
Fig. 2. a. Positionning of the custom ultrasonic probe and the 8 EEG electrodes. b. Location on the Bmode image of the fUS blood volume image and the 3
regions of interest c. Typical evolution of the EEG during intermittent epileptic seizures: bursts of electrical activity are observed during the seizures. d.
Increase of the fUS signal in the three regions of interest in the right hemisphere during those seizures. e. – f. snapshots of the imaged brain area between
seizures (e., second red arrow) and during a seizure (f. first red arrow).
(Fig. 1d). UfD average cortical signal variations were
correlated with EEG bilateral bursts of slow waves (50-
150μV). We selected typical bursts/interburst interval
sequences (n=13) on the 2 closest channels to the US probe to
temporally register them with the average UfD signal. Slight
variations in the average UfD signal were recorded with a
4.8±1.4% increase in blood volume during and just after the
activity burst, with a good signal-to-noise ratio (p<0.0001
compared to baseline), before recovering to baseline around
10s after the beginning of the burst. This is the first evidence
that fUS is feasible in human neonates and is closely correlated
with EEG-recorded electrical events, even those of very low
amplitude during quiet sleep.
B. Epileptic Seizures fUS Imaging
We then studied a full term neonate presenting tuberous
sclerosis complex with a hemimegalencephaly (right
hemisphere) causing a drug-resistant structural epilepsy
characterized by frequent unilateral epileptic seizures. The
patient was investigated using fUS+EEG at day 14 after
parental consent was obtained (Fig.2 a.). A period of two and a
half hours was recorded, with a series of 6 ictal periods when
the patient showed few movements and inconspicuous tremors.
jerky eye movements, contrasting with massive ictal EEG
activity ipsilateral to the hemimegalencephaly. During ictal
events, very significant 50-60% increases in the UfD signal
were observed in right cortical areas (ROI 1 and 2 on figure 2
b) when compared to contralateral areas (ROI 3 on figure 2 c)
(p<10-5 in all seizures) (Fig. 2e-f). The spatial location of the
maximum UfD changes varied during and after the recorded
ictal periods, depicting that the highest ictal activity moved
from one location to another during the seizures (Fig. 2 d.).
IV. DISCUSSION
Altogether, these data demonstrated that real-time fUSI is
feasible in humans at bedside. First we showed that fUS
imaging presents for the clinical setting a unique combination
of portability, low cost, usability, spatial and temporal
resolution that make it a modality of choice for bedside
functional neuroimaging in the future, especially in neonatal
patients. Second we have shown we could image dynamics and
location of transient events such as ictal and post ictal events in
epileptic seizures, a category of neurological phenomenon
unreachable for imaging modalities such as fMRI or PET, and
spatially indescribable for EEG. Third, the unique spatio-
temporal resolution of fUS imaging allowed for the observation
of how neuro-vascular changes propagate throughout the
cortex in response to ictal events, which brings new
fundamental insights to the understanding of seizures in
humans.
ACKNOWLEDGMENT
We acknowledge Thomas Tisseuil, from Nihon Kohden for
is kind support with the EEG.
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