so we’re all under a little bit of
pressure some of us more than others I’m
a presumably under a little more
pressure up here if you’ve ever been to
the the doctor and I think probably
everybody listening has been your
pressure has been measured you know how
about you what your internal pressure is
and as you can see on the screen your
your blood pressure was probably
measured with a blood pressure cuff that
looks something like this so what does
blood pressure come from it’s the the
force the pressure of the blood pumping
through your body pressing on your
artery what is measured as a function of
the stiffness of the artery so your age
your your physical condition whether or
not you’re giving a talk to an audience
of hundreds whether you’re relaxed in
the back of the room we’re hopefully
tweeting but blood pressure has been
used for a long time and one of the
reasons that it’s it’s it’s a biomarker
that doctors like is that they have a
lot of data on it and there’s a lot of
history in terms of what it means to
have a normal blood pressure or an
abnormal blood pressure but it’s
actually kind of complicated to get you
have this blood pressure cuff you can do
that in the home you can do that at the
doctor I have a vision where we make it
a little bit easier but how do we make
it easier if you were to take your your
fingers and put them next to your
esophagus either on the left or the
right of your of your neck if you’re to
stop talking for a second you can feel
your pulse and if your fingers were very
very sensitive I argue that your fingers
could actually tell you your blood
pressure so if you sort of pressed a
little bit on your neck your relax a
little bit on your neck how your your
blood pressure I have that stiffness of
your neck felt as you were pressing on
it might tell you something about what
your bread your blood pressure actually
was so what you’re seeing on the screen
is an exploration of the act of
deforming tissue so your body is there’s
bones inside but most of its the soft
tissue that you deform
and tissue deforms from the blood
pumping through it so internal pressure
making the tissue to form and you can
deform your tissue by applying external
pressure but pressing on your body what
you’re looking at here is an ultrasound
probe analogous to what you’d find at
MGH or Beth Israel Hospital or any
Hospital around the world and there’s an
ultrasound image of in this case the
brachial artery but we’ve measured the
amount of force that is being applied
during the image acquisition so it’s an
ultrasound probe what you’re seeing this
blue frame around the ultrasound probe
is a 3d printed clamshell that attaches
to the outside of the probe and inside
of that clamshell is a force sensor that
allows us to measure how hard were
pressing how hard we’re trying to deform
the tissue from the outside of the body
while the blood pressure is pushing on
the inside and you can see when you
apply just a little bit of force I would
normally point with a laser pointer but
I guess the image on the Left far left
where we’re applying one Newton of force
the the artery the brachial artery in
this case is not very deformed as we
increase the force a little bit more up
to five Newtons the artery is getting a
little more a little more compressed so
this is an observation how do we use
this now so the and this notion that we
can sort of feel our pulse to get to a
vision where we can potentially just
measure our blood pressure we’ll get up
in the morning when we’re shaving I have
a lot of experience with shaving maybe
not the face but certainly in my head or
applying makeup so I have a vision where
we want to just take a device that sort
of comfortably fits into the palm of
your hand you just touch it to your neck
again in five seconds I have a measure
of blood pressure so how do we do that
so a little bit of an anatomy lesson
first so this is the on the top we’re
seeing the carotid artery around the
carotid artery we see the esophagus we
see the vertebrae and in the bottom
image we see an ultrasound probe that’s
been used to acquire a cross-sectional
slice of that anatomy in the center you
see the carotid you see the esophagus or
the shadow and the the right half of the
image and you see the vertebra sort of
deep below on the backside of the art
so what we’re looking at in this video
sequence is a application of an
ultrasound probe slightly resting on the
carotid artery where the patient or a
caregiver is just modulating the amount
of external pressure that’s being
applied and so you can see that in the
video by the the distance between the
surface of the skin and say the
musculature to the left of the artery
getting slower or getting smaller and
smaller and smaller so we’re steadily
increasing the amount of pressure that’s
applied from the outside of the body at
the same time you’re seeing the
pulsating of the artery from the inside
of the body you seeing this pulsation of
the of the blood pressure pumping
through the carotid artery so we were to
take that video and that that sequence
of ultrasound imagery and select a few
frames of it we see sort of a low a
medium and a high level of force on the
left to the right of the frame and the
plot that we’re seeing in the bottom of
the screen is a is the diameter of the
minor axis of the artery so it’s the the
distance from the top to the bottom of
the artery as we’re slowly increasing
our force so as you would expect if if
we didn’t have any blood pressure and we
just had this too filled with fluid we
press it press it press it we get narrow
and narrow narrow and you’re seeing that
general trend of decreasing and but
you’re seeing the internal pressure of
the of the blood pulsating the artery
bigger bigger bigger as we go
so those three frames that we’re seeing
correspond to those three peaks and so
this is the data that we can use
destroyed that start to understand if
our fingers were sensitive enough and
could measure the diameter how did we do
that not sure yet I think it measures
the diameter of the of the artery and
maybe we can get something about blood
pressure this changing diameter and this
changing diameter is impacted by how
we’re pressing up from the outside and
how blood is pressing on the inside okay
so this is what we do so to try to
answer this question
started collecting a bunch of data at
Mass General Hospital and a couple of
clinical trials used a conventionally a
commercially available ultrasound probe
and again on the outside of this probe
we mounted a a force sensor that
measures how hard were pressing the
probe against the body and then use that
to acquire really two pieces of data the
the bottom video or the video is again
the sequence of acquiring the ultrasound
imagery across the carotid and you see
the forces being increased and you see
the pulsation of the carotid from the
internal force and the the plot on the
bottom right is the force that we
applied during the imaging process how
hard we’ve pushed on the outside of the
body as we’re acquiring this imagery
I’ll just point out there’s these three
little peaks at the beginning of the
force sequence and that’s just to allow
us to synchronize the data so the our
ability to measure force and our ability
to acquire this ultrasound data they’re
not tied together two separate systems
so that we can align the data we do this
pulse pulse pulse so we can synchronize
and then slowly ramp up our force and
acquire that force data and it’s imagery
data so we have this data set now and we
really solved this this massive
computational problem which as it turns
out with enough work and a doctoral
student working on it for five years can
give it to the point where this massive
computation runs in real time
but as input we use this ultrasound data
as a function of known applied force so
at the top of us the input is image
image image image and each image has an
applied force associated with it now we
model the tissue we model the carotid
artery we model the bone as a as a slab
of tissue with a an artery or pressure
vessel that has a certain diameter that
we don’t know it has an internal
pressure that we don’t know and we don’t
know the properties of the tissue so we
use this complete observed data set of
applied pressure and what the ultrasound
imagery is giving us and from the
ultrasound imagery we can see how the
tissue is deforming and we iteratively
solve this very large
model just this numerical model using
what’s called finite element modeling
but it’s a sort of a network of little
Springs and masses connected together to
simulate what tissue actually is and out
of that model we estimate a large number
of things we estimate well what is the
actual average tissue stiffness what is
the average stiffness of the artery what
is the diameter of the artery and most
importantly what is the internal
pressure of the artery so we just
published a paper earlier this year as
it’s sort of hot off the presses work
that’s happening in my group this was
sort of our first clinical trial on 24
single visit volunteers the ground truth
that we can compare our measurement to
is the blood pressure cuff our accuracy
here compared to the blood pressure cuff
on both systolic and diastolic 7% and 9%
which is actually very very good because
the blood pressure cuff itself is only
good to about 10% so we don’t know
whether the error is in the cuff for the
errors in our measurement but also the
other thing that gives us a lot of
extreme confidence there we go is now
following an individual over a long
period of time so this is a another
volunteer this is a actually a
hypertensive medicated hypertensive
volunteer who came into the lab seven
visits over a one-month period and this
individual came in right after being
medicated right after taking the
medication and that tends to drop the
blood pressure and then we tracked over
a period of time as the medication sort
of works through the system and blood
pressure increases until it gets to the
end of the month where that probably be
another dose to be required but what
we’re seeing is very very good tracking
agreement for the individual on a
measure of blood pressure from the blood
pressure cuff and from our technique of
taking a little handheld device that
almost looks like an ultrasound probe
and just getting an image of the carotid
artery and applying a little bit of load
so ultimately we want to try to enable
at the bedside at the at the vanity
while you’re shaving or applying makeup
you know instead of just shaving pick up
this device touch it get a measure of
blood pressure and that gives you far
more frequent measurements so we don’t
really understand in the context of
daily living how our blood pressure
varies if you want to get your blood
pressure now you typically have to get
the cuff out so this would give us a
weight of more far more frequently get
our underlying physiological data and
that can teach us a lot about the
physiology about our normal variation
but ultimately the direction that we’re
going is how do we now use this to
enable a blood pressure patch and I’m
gonna leave this as the teaser because
of something we’re working on now and to
do this blood pressure patch I argue you
need three things you need an approach
an algorithm a way to make this
measurement and that’s what we’ve
demonstrated was sort of this handheld
device a way to acquire data that’s
ultrasound and force and to process that
data and give a very strong estimate of
the internal pressure our blood pressure
but then you also need a a way to make
this a thing that you wear and then you
also need a manufacturing process so
I’ll leave that as a teaser for maybe
for next year
and our ongoing work is miniaturizing
these devices getting more data on other
hypertensive patients there’s a lot of
application in other areas where
pressure may be interesting so blood
pressure is certainly one arterial
pressure but venous pressure is another
area and with that thank you for
listening
you
pressure some of us more than others I’m
a presumably under a little more
pressure up here if you’ve ever been to
the the doctor and I think probably
everybody listening has been your
pressure has been measured you know how
about you what your internal pressure is
and as you can see on the screen your
your blood pressure was probably
measured with a blood pressure cuff that
looks something like this so what does
blood pressure come from it’s the the
force the pressure of the blood pumping
through your body pressing on your
artery what is measured as a function of
the stiffness of the artery so your age
your your physical condition whether or
not you’re giving a talk to an audience
of hundreds whether you’re relaxed in
the back of the room we’re hopefully
tweeting but blood pressure has been
used for a long time and one of the
reasons that it’s it’s it’s a biomarker
that doctors like is that they have a
lot of data on it and there’s a lot of
history in terms of what it means to
have a normal blood pressure or an
abnormal blood pressure but it’s
actually kind of complicated to get you
have this blood pressure cuff you can do
that in the home you can do that at the
doctor I have a vision where we make it
a little bit easier but how do we make
it easier if you were to take your your
fingers and put them next to your
esophagus either on the left or the
right of your of your neck if you’re to
stop talking for a second you can feel
your pulse and if your fingers were very
very sensitive I argue that your fingers
could actually tell you your blood
pressure so if you sort of pressed a
little bit on your neck your relax a
little bit on your neck how your your
blood pressure I have that stiffness of
your neck felt as you were pressing on
it might tell you something about what
your bread your blood pressure actually
was so what you’re seeing on the screen
is an exploration of the act of
deforming tissue so your body is there’s
bones inside but most of its the soft
tissue that you deform
and tissue deforms from the blood
pumping through it so internal pressure
making the tissue to form and you can
deform your tissue by applying external
pressure but pressing on your body what
you’re looking at here is an ultrasound
probe analogous to what you’d find at
MGH or Beth Israel Hospital or any
Hospital around the world and there’s an
ultrasound image of in this case the
brachial artery but we’ve measured the
amount of force that is being applied
during the image acquisition so it’s an
ultrasound probe what you’re seeing this
blue frame around the ultrasound probe
is a 3d printed clamshell that attaches
to the outside of the probe and inside
of that clamshell is a force sensor that
allows us to measure how hard were
pressing how hard we’re trying to deform
the tissue from the outside of the body
while the blood pressure is pushing on
the inside and you can see when you
apply just a little bit of force I would
normally point with a laser pointer but
I guess the image on the Left far left
where we’re applying one Newton of force
the the artery the brachial artery in
this case is not very deformed as we
increase the force a little bit more up
to five Newtons the artery is getting a
little more a little more compressed so
this is an observation how do we use
this now so the and this notion that we
can sort of feel our pulse to get to a
vision where we can potentially just
measure our blood pressure we’ll get up
in the morning when we’re shaving I have
a lot of experience with shaving maybe
not the face but certainly in my head or
applying makeup so I have a vision where
we want to just take a device that sort
of comfortably fits into the palm of
your hand you just touch it to your neck
again in five seconds I have a measure
of blood pressure so how do we do that
so a little bit of an anatomy lesson
first so this is the on the top we’re
seeing the carotid artery around the
carotid artery we see the esophagus we
see the vertebrae and in the bottom
image we see an ultrasound probe that’s
been used to acquire a cross-sectional
slice of that anatomy in the center you
see the carotid you see the esophagus or
the shadow and the the right half of the
image and you see the vertebra sort of
deep below on the backside of the art
so what we’re looking at in this video
sequence is a application of an
ultrasound probe slightly resting on the
carotid artery where the patient or a
caregiver is just modulating the amount
of external pressure that’s being
applied and so you can see that in the
video by the the distance between the
surface of the skin and say the
musculature to the left of the artery
getting slower or getting smaller and
smaller and smaller so we’re steadily
increasing the amount of pressure that’s
applied from the outside of the body at
the same time you’re seeing the
pulsating of the artery from the inside
of the body you seeing this pulsation of
the of the blood pressure pumping
through the carotid artery so we were to
take that video and that that sequence
of ultrasound imagery and select a few
frames of it we see sort of a low a
medium and a high level of force on the
left to the right of the frame and the
plot that we’re seeing in the bottom of
the screen is a is the diameter of the
minor axis of the artery so it’s the the
distance from the top to the bottom of
the artery as we’re slowly increasing
our force so as you would expect if if
we didn’t have any blood pressure and we
just had this too filled with fluid we
press it press it press it we get narrow
and narrow narrow and you’re seeing that
general trend of decreasing and but
you’re seeing the internal pressure of
the of the blood pulsating the artery
bigger bigger bigger as we go
so those three frames that we’re seeing
correspond to those three peaks and so
this is the data that we can use
destroyed that start to understand if
our fingers were sensitive enough and
could measure the diameter how did we do
that not sure yet I think it measures
the diameter of the of the artery and
maybe we can get something about blood
pressure this changing diameter and this
changing diameter is impacted by how
we’re pressing up from the outside and
how blood is pressing on the inside okay
so this is what we do so to try to
answer this question
started collecting a bunch of data at
Mass General Hospital and a couple of
clinical trials used a conventionally a
commercially available ultrasound probe
and again on the outside of this probe
we mounted a a force sensor that
measures how hard were pressing the
probe against the body and then use that
to acquire really two pieces of data the
the bottom video or the video is again
the sequence of acquiring the ultrasound
imagery across the carotid and you see
the forces being increased and you see
the pulsation of the carotid from the
internal force and the the plot on the
bottom right is the force that we
applied during the imaging process how
hard we’ve pushed on the outside of the
body as we’re acquiring this imagery
I’ll just point out there’s these three
little peaks at the beginning of the
force sequence and that’s just to allow
us to synchronize the data so the our
ability to measure force and our ability
to acquire this ultrasound data they’re
not tied together two separate systems
so that we can align the data we do this
pulse pulse pulse so we can synchronize
and then slowly ramp up our force and
acquire that force data and it’s imagery
data so we have this data set now and we
really solved this this massive
computational problem which as it turns
out with enough work and a doctoral
student working on it for five years can
give it to the point where this massive
computation runs in real time
but as input we use this ultrasound data
as a function of known applied force so
at the top of us the input is image
image image image and each image has an
applied force associated with it now we
model the tissue we model the carotid
artery we model the bone as a as a slab
of tissue with a an artery or pressure
vessel that has a certain diameter that
we don’t know it has an internal
pressure that we don’t know and we don’t
know the properties of the tissue so we
use this complete observed data set of
applied pressure and what the ultrasound
imagery is giving us and from the
ultrasound imagery we can see how the
tissue is deforming and we iteratively
solve this very large
model just this numerical model using
what’s called finite element modeling
but it’s a sort of a network of little
Springs and masses connected together to
simulate what tissue actually is and out
of that model we estimate a large number
of things we estimate well what is the
actual average tissue stiffness what is
the average stiffness of the artery what
is the diameter of the artery and most
importantly what is the internal
pressure of the artery so we just
published a paper earlier this year as
it’s sort of hot off the presses work
that’s happening in my group this was
sort of our first clinical trial on 24
single visit volunteers the ground truth
that we can compare our measurement to
is the blood pressure cuff our accuracy
here compared to the blood pressure cuff
on both systolic and diastolic 7% and 9%
which is actually very very good because
the blood pressure cuff itself is only
good to about 10% so we don’t know
whether the error is in the cuff for the
errors in our measurement but also the
other thing that gives us a lot of
extreme confidence there we go is now
following an individual over a long
period of time so this is a another
volunteer this is a actually a
hypertensive medicated hypertensive
volunteer who came into the lab seven
visits over a one-month period and this
individual came in right after being
medicated right after taking the
medication and that tends to drop the
blood pressure and then we tracked over
a period of time as the medication sort
of works through the system and blood
pressure increases until it gets to the
end of the month where that probably be
another dose to be required but what
we’re seeing is very very good tracking
agreement for the individual on a
measure of blood pressure from the blood
pressure cuff and from our technique of
taking a little handheld device that
almost looks like an ultrasound probe
and just getting an image of the carotid
artery and applying a little bit of load
so ultimately we want to try to enable
at the bedside at the at the vanity
while you’re shaving or applying makeup
you know instead of just shaving pick up
this device touch it get a measure of
blood pressure and that gives you far
more frequent measurements so we don’t
really understand in the context of
daily living how our blood pressure
varies if you want to get your blood
pressure now you typically have to get
the cuff out so this would give us a
weight of more far more frequently get
our underlying physiological data and
that can teach us a lot about the
physiology about our normal variation
but ultimately the direction that we’re
going is how do we now use this to
enable a blood pressure patch and I’m
gonna leave this as the teaser because
of something we’re working on now and to
do this blood pressure patch I argue you
need three things you need an approach
an algorithm a way to make this
measurement and that’s what we’ve
demonstrated was sort of this handheld
device a way to acquire data that’s
ultrasound and force and to process that
data and give a very strong estimate of
the internal pressure our blood pressure
but then you also need a a way to make
this a thing that you wear and then you
also need a manufacturing process so
I’ll leave that as a teaser for maybe
for next year
and our ongoing work is miniaturizing
these devices getting more data on other
hypertensive patients there’s a lot of
application in other areas where
pressure may be interesting so blood
pressure is certainly one arterial
pressure but venous pressure is another
area and with that thank you for
listening
you
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