University of Oulu

Teemu Myllylä

Optoelectronics and Measurement Techniques Unit, University of Oulu

Finland

6/21/20171

Towards continuous monitoring of the glymphaticsystem of the human brain

University of Oulu

Outline ‒ Glymphatic system

- Blood brain barrier (BBB) and brain clearance

‒ Multimodal human brain monitoring in Oulu

- BBB disruption monitoring

- Multimodal human imaging in Magnetic Resonance Imaging (MRI)

‒ Towards wearable monitoring

- A combined opto-capacitive-microwave imaging device

- Sensing method

- Validation experiments

6/21/20172

Towards continuous monitoring of the glymphaticsystem of the human brain

University of Oulu

(G)lymphatic system

‒ Lymphatic vessels are present throughout the body

‒ Density of lymph vessels correlates with the rate of tissue

metabolism

‒ Lymphatic flow is responsible for flushing out harmful

fluids from the body system, such as

- toxins

- metabolic waste products

- soluble proteins

6/21/20173

Source: https://www.extremetech.com/

University of Oulu

Glymphatic system

‒ The Glymphatic system is the counterpart of the

lymphatic system elsewhere in the body.

‒ As a whole, it is responsible for flushing out toxins,

metabolic waste products, soluble proteins and

other harmful fluids from the body system into the

CSF drainage

Raper, Daniel, Antoine Louveau, and Jonathan Kipnis. "How Do Meningeal

Lymphatic Vessels Drain the CNS?." Trends in Neurosciences 39.9 (2016): 581-

586.

6/21/20174 Source: http://www.samanthamonarch.com/

University of Oulu

Glymphatic system

‒ CSF flows from perivascular space via

astroglial cell aquaporin channels (AQP4),

through brain tissue.

6/21/20175

Source: http://biofoundations.org/

University of Oulu

Focused ultra sound (FUS) Alzheimer diseace therapy, 2014

BBB and Brain clearance

University of Oulu

Sham SUS

No.

of p

laqu

es/s

ectio

n

Sham SUS

Pla

que

burd

en

(% s

urfa

ce a

rea)

E

B

D

Sha

mS

US

Striatal section Hippocampal section

Sham SUS

C

Pla

que

burd

en

(% s

urfa

ce a

rea)

F

G

55 60 65 75

2.0

1.5

1.0

0.5

0.0

7050

SUS

Sham

Baseline

Age (weeks)

A

DC

3–mer/CTFb

9–mer*56

HMW

GAPDH

Sham SUS Sham SUS

A B

250

75

50

25

15

10

250

75

50

25

15

10

E

Rat

io o

f Ab/

GA

PD

H

HMW *56 3–mer/CTFb HMW *56 3–mer/CTFb Sham SUS

pg A

b42/

mg

tota

l pro

tein

MWM

*56

3–mer/CTFb

HMW

9–mer

GAPDH

1–mer

MWM

Sham

SUS

Rat

io o

f Ab/

GA

PD

H

Fig. 2. SUSreduces Ab plaques in an AD mouse

model. (A and B) Representative images of free-

floating coronal sections from APP23 transgenic

mice (first cohort) with and without SUStreatment.

Campbell-Switzer silver staining revealed compact,mature plaques (amber) and more diffuse Ab de-

posits (black). A stained section at a higher magnifi-

cation isshown in panel (B).(Cand D)Quantification

of amyloid plaquesrevealed a56%reduction in the

area of cortex occupied by plaques (unpaired t test,

P= 0.017) and a 52% reduction in plaque number

per section (t test, P= 0.014) in SUS-treated com-pared to sham-treated APP23mice(n= 10pergroup).

(E and F) Representative sections of SUS-treated

brains versus control brains stained with Thioflavin

S(E)and 4G8(F).(G)Plaqueload plotted asafunctionof age confirmed that the SUS-treated group had

significantly lower plaqueload than thesham-treated

group.Baseline plaque load at the onset of treatment

is indicated by open circles. Scale bars, 1 mm (panel

A) and 200 mm (panel B).

Fig. 3. SUStreatment reduces different Ab spe-

cies. (A to D) Western blotting of extracellular-

enriched (A) and Triton-soluble (B) fractions of thebrains of the first cohort of APP23 mice with 6E10

and 4G8 anti-Ab antibodies revealed a reduction in

distinct Ab species in both fractions in SUS-treated

compared to sham-treated mice. These data arequantified in (C) and (D), respectively. The Western

blots show significant reductions of HMW spe-

cies, the 56-kD oligomeric Ab*56 (*56) and trimeric

Ab (3-mer)/CTFb, in the extracellular-enriched

fraction and of *56 and 3-mer/CTFb in the Triton-

soluble fraction (unpaired t tests, P< 0.05). GAPDH

(glyceraldehyde 3-phosphate dehydrogenase) wasused for normalization. MWM, molecular weight

marker.(E)ELISA for Ab42 in the Triton-soluble frac-

tion revealed asignificant reduction in SUS-treated

compared to sham-treated mousebrains(unpairedt test, P< 0.05; n = 10 per group).

RESEARCH ARTICLE

www.ScienceTranslationalMedicine .org 11 March 2015 Vol 7 Issue 278 278ra33 3

on May 3, 2016

http://stm.sciencem

ag.org/D

ownloaded from

BBB and Brain clearance

University of Oulu

Outline ‒ Glymphatic system

- Blood brain barrier (BBB) and brain clearance

‒ Multimodal human brain monitoring in Oulu

- BBB disruption monitoring

- Multimodal human imaging in Magnetic Resonance Imaging (MRI)

‒ Towards wearable monitoring

- A combined opto-capacitive-microwave imaging device

- Sensing method

- Validation experiments

6/21/20178

Towards continuous monitoring of the glymphaticsystem of the human brain

University of Oulu

BBB disruption monitoring

The BBB forms a major obstacle for brain drug delivery, especially in the treatment of brain tumours. A method involving BBB disruption (BBBD) induced with intra-arterial mannitol infusion, developed at the University of Portland, is exploited at the Oulu University Hospital to treat CNS lymphoma.

9

Myllylä T. et al. ”Studies for drug delivery

detection during blood brain barrier

disruption therapy”, 7th Imaging in Drug

Discovery Conference, October 7-8, 2014 in

Dublin, Ireland, (2014).

University of Oulu

Grand average DC-EEG and average NIRS traces illustrating characteristic responses

evoked by intra-arterial mannitol infusion

V. Kiviniemi, V. Korhonen, J. Kortelainen, S. Rytky, T. Keinänen, T. Tuovinen, M. Isokangas, E. Sonkajärvi, T. Siniluoto, J. Nikkinen, S.

Alahuhta, O. Tervonen, T. Turpeenniemi-Hujanen, T. Myllylä, O. Kuittinen, J.Voipio,”Real-time monitoring of human blood-brain barrier

disruption”, PLOS ONE (2017).10

BBB disruption monitoring

University of Oulu

‒ Drivers of lymphatic and CSF flow

- Body movements, muscle contractions

- Cardiovascular system, arterial and cardiac pulsations

- Blood pressure, which indirectly maintains force of pressure in the lymphatic channels

- Respiratory pulsations induce counter pulsations probably cleaning the perivenulous accumulations

- Very low frequency (VLF) waves modulate CSF convection

=> simultaneous measurement of brain and physiological signals are of interest

Multimodal imaging in MRI- Towards continuous monitoring of the glymphatic system

University of Oulu

A. Zienkiewicz, N. Huotari, L. Raitamaa, V. Raatikainen, H. Ferdinando, E. Vihriälä,

V. Korhonen, T. Myllylä, V. Kiviniemi, “Continuous blood pressure recordings

simultaneously with functional brain imaging - studies of the glymphatic system,

SPIE proceeding, PhotonicsWest (2017).

Korhonen, V., Hiltunen, T., Myllylä, T., Wang, X., Kantola, J., Nikkinen, J., Zang, Y.,

LeVan, P. and Kiviniemi, V. , "Synchronous Multiscale Neuroimaging Environment

for Critically Sampled Physiological Analysis of Brain Function: Hepta-Scan

Concept," Brain connectivity 4(9), 677-689 (2014)

Functional ultrafast MRI, NIRS, blood pressure, EEG, ECG, CO2

expiration and oxygen saturation (SpO2) recordings simultaneously.

A collaboration project in Oulu

- Oulu University Hospital

- Medical Research Center

(Oulu Neuroimaging group, OFNI)

- Oulu Biocenter

- University of Oulu

(Optoelectronics and Measurement

Techniques Unit)

Multimodal imaging in MRI- Towards continuous monitoring of the glymphatic system

University of Oulu

The glymphatic system is more active during sleep [Xie L. et al. "Sleep drives metabolite clearance from the adult brain." science 342.6156 (2013): 373-377]

=> For sleep studies, a wearable, over-night monitoring method needed

Requirements:

- easy to use (small)- suitable for long-term measurements- doesn’t affect sleep quality- completely safe method

6/21/201713

Continuous monitoring of the glymphatic system

University of Oulu

Outline ‒ Glymphatic system

- Blood brain barrier (BBB) and brain clearance

‒ Multimodal human brain monitoring in Oulu

- BBB disruption monitoring

- Multimodal human imaging in Magnetic Resonance Imaging (MRI)

‒ Towards wearable monitoring

- A combined opto-capacitive-microwave imaging device

- Sensing method

- Validation experiments

6/21/201714

Towards continuous monitoring of the glymphaticsystem of the human brain

University of Oulu

Dynamics of CSF volume and flow in subarachnoid space

reflect dynamics of the glymphatic system?

‒ CSF acts as a cushion behind the skull, providing basic mechanical

as well as immunological protection to the brain.

‒ Cerebrospinal fluid (CSF) is a clear, colourless liquid including water

(H2O) approximately with a concentration of 99 %.

6/21/201715

Raper, Daniel, Antoine Louveau, and Jonathan Kipnis.

"How Do Meningeal Lymphatic Vessels Drain the

CNS?." Trends in Neurosciences 39.9 (2016): 581-586.

Continuous monitoring of the glymphatic dynamics- By measuring of CSF in the subarachnoid space

University of Oulu

NIRS sensing

‒ Near Infra-red Spectroscopy

(NIRS)

6/21/201716

Monte Carlo simulation of a multilayered brain. Photon trajectory maps for 830 nm

for source-detector separations of 30 mm (left) and 40 mm (right).

Korhonen, V. O., Myllyla, T. S., Kirillin, M. Y., Popov, A.

P., Bykov, A. V., Gorshkov, A. V., Sergeeva, E.,

Kinnunen, M. and Kiviniemi, V. , "Light propagation in

NIR spectroscopy of the human brain," Selected

Topics in Quantum Electronics, IEEE Journal of 20(2),

289-298 (2014).

University of Oulu

NIRS sensing

6/21/201717

Isosbestic point for oxy- and deoxy Hb

The Beer-Lambert law

Isosbestic point for oxy Hb and water

University of Oulu

Capacitive sensing

‒ Dielectric properties of tissue are well studied,

however, utilization of a capacitive sensor for

non-invasive CSF sensing are not reported

• Capacitors are sensitive to change in

volume of fluid, and even flow

• Can measure total water volume (in blood

and CSF)

• Low manufacturing costs

• Skin (electrical) conductance not needed

6/21/201718

University of Oulu

Capacitive sensor

‒ Basic operation principle: creating step

excitations to the unknown capacitance CX by

using a fixed resistor RC with known voltage

values and measuring the time interval of each

charge time constant which is dependent on CX

‒ The exact value of the unknown CX, which is the

capacitive field over the sensor plates, can be

determined with the obtained results

6/21/201719

Cref: 220 pF Cx

Rc: 4,7 Mohm

Trig

Tresh

Out

TimerLMC555

DAQNI USB-6212

Counter in

The basic construction of the capacitance measuring device.

University of Oulu

Capacitive sensor

‒ The time of high and low periods of the square wave

(charging and discharging sequences), shown in Fig

below, is read by a counter using 80 Mhz clock

frequency.

‒ the value of Cx can be determined using the equation

on left if a reference capacitor is in parallel with Cx.

6/21/201720

Vcap: voltage over the unknown capacitance.

Vout

Vouth: 3,1 V

Voutl: 0,2 V

Vtrig: 1,14 V

Vtresh: 2,27 V

Vout: timers output (charging) voltage.

Vcap

T = time periods of the square wave. T is 0,34 ms when Cx is not connected which corresponds frequency of 2,9 kHz.

Fig. Signals and voltages of the capacitance measuring device.

University of Oulu

Capacitive sensor

‒ In addition, the device uses a multiplexer (Texas Instruments CD4051) which enables selecting Cx from eight different sources

6/21/201721

Capacitance measurement device connected to a multiplexer. Cx can be selected from eight different sources (channels 0 i/o - 7 i/o).

Capacitance measurement device (fig.1)

MultiplexerCom o/i

0 i/o

1 i/o

2 i/o

3 i/0

4 i/o

5 i/o

6 i/o

7 i/0

CD4051

University of Oulu

Microwave imaging technique

‒ One recent example is wideband microwave head imaging system for on-the-spot detection of intracranial hemorrhage. The dielectric contrast between healthy brain tissues and a hemorrhage that causes a strong microwave scattering.*

‒ The system uses a compact sensing antenna with directional radiation, and a portable, compact microwave transceiver for signal transmission and data acquisition

‒ System operates from 0.75–2.55 GHz

‒ The collected data is processed to create a clear image of the brain using an improved back projection algorithm

6/21/201722

*Mobashsher, Ahmed Toaha; Mahmoud, A.; Abbosh, A. M. Portable

wideband microwave imaging system for intracranial hemorrhage detection

using improved back-projection algorithm with model of effective head

permittivity. Scientific reports, 2016, 6.

University of Oulu

Validation of sensitivity

‒ 3D simulations using

- COMSOL Multiphysics for capacitive technique

- Cone-Shaped Distribution (CSD) for microwave technique

- Monte Carlo for optical technique

‒ Multilayered phantom measurements

- Mimicking both optical and dielectric properties of brain tissues

- In vivo measurements in MRI

6/21/201723

University of Oulu

Simulations

‒ Geometric setup: a capacitor is placed on top of a human head with layers of skin, skull and

cerebrospinal fluid

6/21/201724

Geometric setup (left). The change in volume of the CSF is plotted against the change in capacitance for different configurations of the capacitor (right).

University of Oulu

‒ Capacitive sensor test and simulation was done using the same geometric setup and method

‒ Both simulation and real measurement show that small changes in water volume can be detected.

6/21/201725

Average response of the capacitive sensor (right) and the simulation result (left). The thickness of the layer of water was varied from 1 mm to 10 mm.

Phantom experiments

Myllylä T, Vihriälä E, Pedone M, Korhonen V, Surazynski L, Wróbel M, Zienkiewicz A, Hakala J, Sorvoja H, Lauri J, Fabritius T, Jędrzejewska-Szczerskae M,

Kiviniemi V, Meglinski I (2017) Prototype of an opto-capacitive probe for non-invasive sensing cerebrospinal fluid circulation, Invited Paper, Proc. SPIE 10063.

University of Oulu

@1900 MHz

Tissue Source Permittivity Elec. Cond. (S/m)

Skin Skin (Dry) 38.71429860635464 1.224532125743767

Skull Cancellous Bone Cancellous 19.213035781740164 0.6199036157247495

Skull Cortical Bone (Cortical) 11.716472852861365 0.2924341961945009

Cerebrospinal Fluid Cerebrospinal Fluid 67.05564806810452 2.9972739179098724

Brain Cerebellum 45.884888803827074 1.7652286689074284

Brain (Grey Matter) Brain (Grey Matter) 49.88159397536683 1.4502995498876796

Brain (White Matter) Brain (White Matter) 36.8683967651613 0.9575054584828246

Source

https://www.itis.ethz.ch/virtual-population/tissue-properties/database/dielectric-properties/

Human Skull Electrical and Mechanical Parameters

Phantom experiments

University of Oulu

- Oulu Functional Neuro-Imaging group (OFNI)

- Health & Wellness Measurements group (HWM)

Alexander Bykov, Jaakko Hakala, Markus Harju, Vesa Kiviniemi, Vesa Korhonen, JanneLauri, Igor Meglinski, Matteo Pedone, Lukasz Surazynski, Marko Tuhkala, Erkki Vihriälä, Aleksandra Zienkiewicz

Thank you!

Contact: Teemu.Myllyla@oulu.fi

6/21/201727

Acknowledgement