[James Stuart Olson] Hello.
Lesley Williams [Brunet] Hello to you.
[James Stuart Olson] Hello.
[Lesley Williams Brunet] It seems we're okay.
(inaudible) Comes out of the box.(laughing) (inaudible).
[James Stuart Olson] But will you be coming back here?
[Lesley Williams Brunet] Yes, I'm going to get you some water.
[James Stuart Olson] Okay. Thanks, Lesley.
Lesley Williams [Brunet] (inaudible)
[James Stuart Olson] Yeah, I would.
[Lesley Williams Brunet] (inaudible) We have coffee.
I think we (inaudible)
[Peter Almond] Water will be fine. Lesley, thank you.
[James Stuart Olson] I guess one of the first thing that I'm interested in is
the evolution of some of the equipment.
We start off with the external beam equipment.
I think also for my own knowledge,
what the difference between a linear accelerator
is or a cyclotron, an X-ray machine.
What are the advantages or disadvantages
of protons, neutrons, and electrons?
Those technical kinds of questions.
(laughing) We started off
with the evolution of external beam.
[Peter Almond] You just want me to (crosstalk) level it.
When X-rays were discovered by accident.
But shortly after that,
people started making X-ray tubes which have
electrons start at one side and go across and
hit a target and produce the X-ray.
Is this a cathode?
Well, within the X-ray tube,
you have to apply
a high voltage across the tube to accelerate
the electrons to hit
the target and then produce the X-rays.
With development, you can get the voltage across the tube
up to about 300,000 volts.
The higher the voltage,
the faster the electrons go in,
the higher the X-rays that come out.
Now the reason you want high energy X-rays
is that the higher the energy,
the more they penetrate into the body.
In the early days when it was
very low voltage on the tubes,
the X-rays produced essentially would go into
the body and they would penetrate,
but they would very rapidly lose their intensity.
You couldn't put much radiation dose deep in the body.
All of it would be at the surface.
[James Stuart Olson] Therefore there can be more damage at surface tissues.
[Peter Almond] Yes. Well, of course,
you want to put the dose.
If the tumor is at depth,
that's where you want to put the radiation energy,
but you have to go through the surface
and then the surface got a higher energy.
In those days, radiation therapy was limited by
the skin dose and people got erythematous skin reactions.
Very severe in those days or radiation therapy.
It was all limited by
the skin reaction and
how much dose you could put it there.
Because the radiation went through.
But clearly so if you could get
more radiation going deeper and deeper,
then you could spare skin.
But up to about 300,000 electron volts,
on a regular basis you could do with regular X-ray tubes.
There were some special tubes made that went up higher,
but they were never wanted (inaudible).
Just too difficult and large and cumbersome.
But for the normal X-rays used in treatment,
250-300,000 electron volts were used.
But even at that energy,
you would get about 50 percent of the dose at
about six or seven centimeters in,
and a 100 percent on the surface and
only 50 percent of six or seven centimeters.
You were again, really limited
by how much dose the skin will tolerate.
You could try using
the radiation coming in
from different directions to meet in the middle.
You can do that.
But even if you lost 50 percent
by six or seven centimeters into the body,
people are thicker than that.
Even using beams coming
from different directions, it's a problem.
One really wanted to go in
higher energy to get more penetration.
But the X-ray machines for doing
that just really cannot be built,
at least not successfully and not on a regular basis.
That took us up to about World War II
when those machines were in, shortly thereafter.
Those energy when it's people
(inaudible) and others who thought now if we
could find a radioactive material that had a gamma-ray,
which was the same as the X-rays,
but much higher energy maybe that can be used.
Groom it. Before the war had in England built a number
of external treatment machines using radium.
But radium had a lot of disadvantages.
One is, it's very expensive.
Two, you had to get a lot of it to put
into a unit to use for external beam.
They were never successful.
They were extremely dangerous in many ways.
Too much radium around.
That didn't seem to work.
Cobalt 60 seemed to be
promising because it had
a high-energy gamma ray coming out.
The average energy was over a million volts.
That's a big advantage.
The other thing that happens when you
go to the higher energies,
when you deposit energy
with a radiation beam in the patient,
the X-rays interact and
set in motion electrons and it's
the electrons that deposit the energy.
If your X-rays are low energy,
the electrons coming off are
fairly low energy and they don't go any distance.
You go up in higher energy.
You said electrons in motion require a lot of energy,
which go in the forward direction and
deposit their energy downstream,
and by the time you get to cobalt 60 energies, now,
it takes about half a centimeter or so for
the radiation dose to meet its maximum in the body.
So the skin dose now is maybe
50 percent of what the maximum doses,
which is a half a centimeter,
and then the dose at say,
10 centimeters could be 50 percent.
You do two things. You put the radiation dose deeper into
the body and at the same time you square
the skin and radiation reactions with cobalt
60 are much less than the old X-rays machines.
Old X-ray machines in that range are
100-200 KV were called ortho voltage.
[James Stuart Olson] Ortho?
[Peter Almond] Ortho. You'll see that term.
It's ortho voltage therapy and ortho voltage machines.
We had a whole suite of
ortho voltage machines when I first came.
As I said, it was the skin dose
that limited the treatment.
Cobalt 60 immediately said,
well, skin dose is going to be far less,
which it was clinically and it was still there,
but it was far less and you're
putting the radiation much deeper.
Second thing is with the cobalt 60,
you could get enough of it in terms of its activity
to put in a machine so the output was high
enough and so that you could do this radium.
It just didn't put out.
You couldn't get enough radium to really
have a treatment over a short enough time.
But cobalt 60, you could get enough cobalt into
the unit treatment times for reasonable length.
Because you had enough radiation,
you could move the patient about 80 centimeters,
to a 100 centimeters from the source where you had
a nice distance between the source and the patients.
There are various reasons you want to do that.
But about a meter is about the optimum from the source.
You could get to that with cobalt 60.
Cobalt 60 looked like
having a lot of advantages and (inaudible)
others and development of the cobalt
60 immediately allowed you
to do a lot of things you couldn't.
What if that was true? If you went from say,
250,000 electron volts to 1 million electron volts.
If you could go up to 10,
20 million electron volts,
you really stop because now
the skin dose rarely gets very, very low.
The maximum dose is
about several centimeters into the body.
By the time the 50 percent dose
is 16 centimeters into the body,
you can really start with a lot of
radiation dose into deep seeded tumors.
You're not limited by any skin reaction whatsoever.
Difficulty is getting to
20 (laughing) electron volts for your X-ray machine.
One of the first possibilities
for that was the device called the Beta Trans,
in which Magnetic induction is used.
It's somewhat like a transformer.
You have electrons going around in
a circular motion inside of a tube,
which has got a vacuum in it.
It looks like a great big
doughnut and was in fact called the
doughnut. But so wide.
If you change the magnetic field
while these electrons are going around,
you can induce them to gain energy.
You're changing the field and their energy is increased,
and the radius of this motion stays the same.
If you time things just right,
you can get them going around many
times picking up energy every time they go
around and you can get out to energies at 20 MeV or more.
A fellow by the name of (inaudible) in
Switzerland had this idea many years before the war.
Dr. Kirsten, University of Illinois,
during the war develop these.
I think they had implications
for X-raying big pieces of equipment.
(laughing) Clearly had some military applications here.
But in the University of Illinois,
they realized that they could generate these electrons,
they could strike a target form
the X-rays and these X-rays were very high-energy X-rays.
They suddenly realized that
if you can make those X-rays,
there's obviously a medical application here.
In fact, they had a graduate student on the program
who had a brain tumor and they got
a local radiologist to treat him with these X-rays.
That's how that got started.
Then some people realized there
was an application here and right after the war,
a number of companies in particular Allis-Chalmers in
this country and then another company in Europe decided,
well maybe this was an application that can be used in
treatment of cancer and so
betatrons were built for that purpose.
We got one here.
In fact, when Grim came in '49 and '50,
he was already talking
to the people about getting a betatron.
They were already making plans for that.
It didn't come until the new hospital was ready,
but it came about that time we had
an old Allis-Chalmers 22 MeV betatron.
It's greater a find it was,
you could put more dose deeper.
There was no skin reaction,
so you could treat deep seeded tumors
and this is why Fletcher used it
primarily for external treatment of cervical cancers.
He developed a box technique,
and wrote one field from the front,
one from the back,
one each from either side and cross fired them.
Travel with the betatron was,
it was fairly low output.
Treatments took longer than one would like.
[James Stuart Olson] In terms of the time it took?
[Peter Almond] Yeah.
[James Stuart Olson] Okay.
[Peter Almond] The output was around if on a good day,
perhaps 60 rads a minute.
Today we'll run machines at 400 rads.
Back then, your expectations
were not as high, so you could get it.
It was very noisy because it had
a frequency that produced a lot of noise.
It was a big machine,
wasn't particularly easy to use.
Anyhow, but clearly 20 MeV X-rays were great advantage.
Anderson had the cobalt and they had 20 MeV.
The drawbacks of the betatron
was that they were big machines,
they did have low output and if you
wanted to use the electrons
directly and people were beginning to think about,
well, we use electrons to produce X-rays.
What happens if we just use the electrons themselves?
It's very difficult to get
the electrons out of a betatron.
Can be done,
we had one machine here called the
Siemens betatron, which did it.
But it was not particularly easy.
We tried to get them out of
the old Allis-Chalmers betatron,
but you've got the electrons which are
charged with an electrical charge and it was going
around in a magnetic field
and the magnetic field makes them go
around in a circular motion
and that magnetic field is there.
Now if you want to get them out going straight,
it's very difficult (crosstalk) because
you got to time.
Somehow rather make the electrons
think the electromagnetic field
isn't there and come on out.
They wouldn't have come out straight,
they would always be curved and it was just a mess.
The betatron inherently has the problem with low output,
you can't get the electrons out, fairly big machine.
At the same time,
you can accelerate electrons in a straight line,
if you get them in an appropriate electromagnetic field.
What happened during the war, of course,
when radar got developed,
they became very interested in producing
very strong sources of electromagnetic radiation,
which is what radar is.
Two devices were developed the magnetron and cyclotron.
Magnetron generally was European and
came out of England and
the cyclotron out of the United States.
But these were two devices which produced
enough power in the electromagnetic radiation
to have good radar installations.
People knew that if you
could take that electromagnetic radiation,
put it into a linear structure which is
designed with a series of cavities along it,
If you did that just right,
you could introduce electrons at one end
along with the electromagnetic radiation.
The electrons would ride
the electromagnetic radiation down to the other end,
picking up energy as they went down
these little cavities and
come out with high energies at the other end.
Because it was linear, they
were called linear accelerators.
You put in electromagnetic radiation
at one end along with electrons
and you run them down these cavities and they
were circular cavities put into and all the way down.
People started to build some linear accelerators.
When you first do something,
(laughing) you find out all the problems with it.
But certainly you can do
this and now the electrons are going straight.
You can either take the electrons
that still go straight until you bend them
with a magnet or they can hit
a target and produce X-rays.
[James Stuart Olson] What's our timing on linear accelerators now date wise?
[Peter Almond] Well, this happened right after World War II,
linear accelerators and betatrons have
about the same period of birth,
if you like and certainly for medical practices,
we're still talking in the 1940s,
1950s, the history of them.
Betatrons are relatively simple machines,
there's wasn't much to them.
They're just big,
but if you could build them,
you could build them and get good X-rays.
Linear accelerators are complicated machines.
There are a lot of systems.
Electromagnetic radiation,
you got to produce the electrons,
you got to keep a high vacuum there,
they got to be kept at the right temperature.
Just multiple systems in linear accelerators.
To get all of these working all right,
just together took a long time to develop.
The early linear accelerators for medical purposes,
although they worked were not too reliable or successful.
[James Stuart Olson] The Dr. (inaudible) tell me
that even when we're using here,
they still broke down a lot. (crosstalk).
[Peter Almond] At that point he
might have thought so but they didn't actually.
(crosstalk) (laughing) Because we were very
important in medical applications that you know what
your up-time is and
what percentage of running time you had.
You get anything below 90 percent you're in trouble,
and we would keep us running.
But certainly they would
break down and you don't want them to
breakdown at the critical time, so high reliability.
Linear accelerators are difficult to get
a very higher until you've really worked out all that.
It took a lot longer.
The first betatrons here in '54,
the next one in '60.
It was 10 years later,
we started in '69 or '68,
thinking about getting linear accelerators.
It took us 10 years or more
before even we thought about linear accelerators.
We wrote a request for a proposal for
a linear accelerator in about '69 and
the bids came in and
Raytheon got the bid and they worked with
the French company to build this device.
The French had built one or two and this was
the machine that the accelerating part was in
a room this long (laughing)
two stationary sections and it went through
the wall into a big rotating gantry.
[James Stuart Olson] What I remember now, I think in
1970s on the 10th Congress was here,
they really wanted to get that installed by then.
[Peter Almond] Yeah, that's right. We did,
we put that in,
These machines could go up to,
if you want it, 35 million electron volts.
We ran out again at about 20 million electron volts.
But it enabled us to get
not only high-energy X-rays out what Fletcher wanted for,
but it enabled us to get electrons out,
nice thing about electrons is they
do just treat the surface.
But because you could change the energy of the electrons,
we could treat tumors right on
the surface or a centimeter deep
or two centimeters deep
or three centimeters deep we could vary.
With electrons is no dose beyond where
you deposit their energy for the treatment.
They just stop. X-rays keep
going right through the bottom.
With X-rays, you end up giving us
a total dose to the patient very low.
But nevertheless,
much more tissue gets irradiated with X-rays.
As you know, some people wonder whether that
then causes this later on second tumors.
That's been looked at extensively
here and I'm not sure there's much evidence for it.
If Maryland Stovall is
the person that is the expert in this institution now,
but second tumors due to levels of radiation
and she's looked at it and I
haven't talked to her recently about the her results.
For surface tumors for chess walls, for example,
after mastectomies, where
you may have a centimeter of tissue.
You've got lung underneath it.
Lung, of course, is extremely sensitive to radiation.
You overdose it, you get necrosis,
and fibrosis for the lung.
You would like the radiation to treat
the chest wall but not go into the lung.
Electrons allow you to do that.
When we got the electron beam when
(inaudible) was still alive,
Fletcher, we develop the techniques
for treating the chest wall with electrons.
Unsparing the lung underneath
and electrons allowed you to do that.
We did a lot of those treatments,
I can tell you, and set up the whole techniques.
It also allow to
even the super clear from the internal memory with
electrons because we could just put the dose where
we wanted it with the electrons.
For things like on your hand and stuff like that,
it's ideal because you could just go down at
whatever length you want the electrons in,
and it would spare the other side of the body,
whatever part you're talking about.
Anyhow, linear accelerators came along.
They were slower in developing
because they're much more complex than them.
But they have a much greater potential.
They have a higher output.
You can get a much larger radiation field
with them than with the Beta trans.
Beta trans are also limited to how big the field,
this dimension, and you got some parts of the body,
you want big fields.
I would say during the 70s,
when there were a lot of Beta trans around,
there was still some Beta tran companies selling
Beta trans linear accelerator companies started to
really refine the design
and the reliability of a linear accelerators.
In particular, Varian,
which is an American company
builders Low Energy linear accelerator.
Accelerating structure was about a foot-long,
and it accelerated up to
four million votes and
became a replacement rarely for cobalt 60.
The forensics MV linear accelerators
eventually have become
so reliable much greater capabilities that cobalt 60,
it's no longer is being used in the United States.
One or two places around the world.
Developing countries use cobalt
60 because it is cheaper travel with cobalt
60 every five years you got to change
the source app and that's expensive.
Cobalt 60 decays with a half-life over to five years.
After you've used it for about five years,
the output gets so low that treatments get too long.
The replacement sources cost a lot of money.
Secondly, it's good to have
a licensed person come in and do it
without creating a radiation problem.
Cobalt 60, after 40 years
of use finally replaced by linear accelerators.
Its linear accelerators are safer and they have
some other things about them which make them
superior to cobalt 60 is just a painter.
But Varian they first came out with a forum,
the linear accelerator, which was very successful.
Chest X-rays didn't use electrons,
but the high output
and that became a very useful machine.
They also started to produce
some higher energy machines up to about,
actually, I had one that went to 35,
but that was really too big and didn't happen.
But as the linear accelerators came along,
Beta trans slowly disappeared.
By the mid-1980s, I suspect,
all the Beta tran companies were out of business
and there was nothing wrong with their radiation,
the machines just weren't
competitive with linear accelerators so they disappeared.
But the linear accelerators do
produce the same radiation,
but they do produce electrons more efficiently.
Do produce X-rays outputs,
or you can have almost any output you like.
We run at about 400 rads per minute for X-rays.
You could go higher,
but then there's a little danger if you have
it too high and so treatments are short.
Then it allows you to do all the modern things
that are done with linear accelerators now because
you can put collimators on them that are
multi-leaf and shape fields
just to the shape of the rectangle fields.
They've got these fingers to shape the field.
If you want any shape field and
then that shape could move during the treatment.
It's computer-controlled made so
you can change the shape.
You can rotate these linear accelerators
around the patient while the treatment's going on,
while the shape of the field is
changing and at the same time,
you can change the intensity of the radiation coming on.
What you do now it's
called intensity-modulated radiotherapy, IMRT.
You simply and you rotate the beam around while doing it.
You really focus all the radiation
onto the tumor not in terms only of position,
but the shape of the tumor.
You can do that and if it's close to critical structures,
you can shape the radiation so it misses
the critical structures and
put the radiation right where you want.
When you consider where we were when
linear accelerators all of this started
to where we are today it really is
amazing that computers have
obviously made this all possible.