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today's video is about milking the
thorium cow
it's an amazing piece of science
before we start
there are two or three things that i
need to tell you so you can understand
quite how fantastic it is
the first thing is that to treat cancer
one can use
highly radioactive
atoms
which are taken to the tumor
by complexing them that's binding them
to a protein that is attracted to the
tumor rather than the rest of the body
the second point is that when a
radioactive element decays
the product of the decay can be far more
radioactive
than the original atom that decays you
can have thorium that's not very
radioactive decaying into something
that's much more radioactive
and the third point just before we start
is that
when you have a really radioactive atom
even a nanogram that is ten to the minus
nine of a gram
a thousand millionth
of a gram
has more than a hundred times as many
atoms as there are cells in your body
so you need only a tiny amount of this
highly radioactive material to give a
really big dose to the tumor
so brady was at the oak ridge national
lab in tennessee in the united states
and he was given a tour by rose bowle
who is an expert in the handling of
these highly radioactive elements
we are at building 7920
this is the
small hot cell room we call them caves
this is where we do a lot of our medical
isotope purification or the starting
part of it and we'll show you the rest
of it later some of the material we work
with is very highly radioactive and so
we need shielding to protect us from the
dose that comes from that material
so we work with it with remote handles
this is jay who is doing the operation
of the remote operators here we call
them
manipulators
and he's going to show us the
thorium-229 cow
that we use to milk our medical isotopes
from the guy who was doing it looked
like a magician it was amazing how he
could manipulate these robot arms do you
think you'd be good at it i'm sure i'd
be terrible the thorium is dissolved in
nitric acid that's how we store it we
don't want to take it back to the solid
it becomes a very
insoluble oxide
so we keep it in liquid solution the
thorium cow
is a sample of thorium-229 they thought
it was just waste but then they suddenly
realize this fantastic application
and it's called a cow
because it keeps on giving
more and more actinium just in the same
way that a cow
keeps on giving milk
but the difference is you don't have to
feed the thorium
but you do have to feed a cow
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yeah this is old material but at the
time that it was made we didn't have a
medical isotope application so this was
something that would have been thrown
away as waste material that we were able
to go and recover
something very useful out of it the
chemistry or perhaps the physics behind
it
is that
thorium-229 gives out an alpha particle
which has mass 4 and contains two
protons so you go two elements to the
left to radium and then the radium gives
out a beta particle that's an electron
and it goes
one element to the right and you get to
actinium two to five
the first stage of the milking is to
remove the thorium from solution
so that you can then process the
actinium
and they do this with a resin solid acid
which is something like this material
here this is also a solid acid
essentially tiny
pellets of polystyrene
which have been treated so they have
acid groups on it see the columns he's
pulled that rack out if you notice
it was up against the wall to start with
our thorium we run it through that
column to separate it from the actinium
that's an anion exchange column it has a
glass frit on the top that holds the
resin down for when we dump water on top
it doesn't disturb the resin bed
and
it's stored with water on it right now
until we go to do the next run the next
separation run so there's there's
nothing radioactive in there at the
moment you're not sort of muting
anything there at the moment no not in
that column in fact we keep our uh
radioactive material off of the column
between runs because
if the radiation will destroy the resin
so now they have solution which contains
actinium and some radium they put it
through series of other columns to
purify it
with
resins and they adjust the acidity of
the solution
so that first all the radium is removed
and eventually all they're left with is
pure actinium and today we're
packaging it in small glass v vials in
order to ship it to the customer
so over on this next place here this is
where they're doing the evaporation of
the material
they are only going to produce a sample
of about a nanogram
a nanogram is such a small amount of
material
that you can't actually see it
the problem is that whoever is going to
buy it needs to know where it is
so they use a bottle
which has a v-shaped bottom
conical bottom so as you concentrate the
liquid it goes right down to the bottom
we try to evaporate it down in the v
part the very bottom because the
customers usually dissolve this up in
about 100 or 200 microliters of solution
which is about two to three drops they
evaporate it and you get the bottle and
right at the bottom is a tiny bit of
actinium so the question is how do they
know if they've got any there and they
have an extraordinarily cunning piece of
kit which they call the gamma-ray camera
which measures
some of the gamma rays that are given
out
by the actinium when it decays
a gamma ray is like
light beam or photon of light but very
short wavelength so it will go through a
lot of materials including through the
shielding at the front of the box
another way you can see the element is
that as it decays it actually gives out
a glow of blue light the glow is pretty
weak so if you want to photograph it you
have to switch out all the lights and do
a long exposure
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they're bagging out the dried
actinium-225
so we took it to complete dryness in
those glass vials
so she'll work it all the way down to
the bottom of the bag
and then they'll run a
heat seal across there
the plastic is melted there into a band
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i should say they sell the bottle for a
thousand dollars
just wait a moment a thousand dollars
for one thousandth
of a microgram
means that you would have to pay
a thousand million dollars for a gram of
this material
of course you couldn't make a gram of
this material and it would be so
radioactive that nobody could handle it
but
that just gives you an idea of the sort
of price
of this material they use it to make
medications and so the medi this is
actually they tell me is one of the less
expensive ingredients necessarily in the
final medicine once they get it made
we're very motivated by the fact the
application
everybody knows somebody who's had
cancer or some family member that has
cancer and is dealing with that
so
we're very excited to be able to work
with something that we know gets
immediate application
you know a lot of the research that we
do
down the road it might develop into
something but
ours
it goes out weekly for patients to be
treated
so it's very nice being that closely
connected with the product
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