In the early days of photography, all you had were shades of grey.
Every colour on the spectrum, from red to violet,
was squashed down by the photographic process.
And actually, early photographic film didn't even manage that.
It used chemicals that were mostly sensitive to blue light.
So if something was bright red, the chemicals would barely react to it.
It'd just look black on camera.
Which is why dark rooms,
where the photo-sensitive film was developed,
could be lit with red light without ruining the pictures.
It turned out that film like that would also react to x-rays.
Now, visible light can pass through some solid objects
as anyone who's ever held their hand up to a light
and looked at their veins can tell you.
But x-rays, with a higher energy and shorter wavelength
pass through objects a lot more easily.
So the picture doesn't get scattered into a blurry mess.
So an x-ray photo takes those short wavelengths
and translates them into something that our eyes can see.
Unfortunately that higher energy
also means that x-rays are ionising radiation.
They come with a risk of cancer and radiation poisoning.
Before that was known, fluoroscopes, which used a constant beam of x-rays,
seemed like a great idea.
Now they are very carefully controlled.
But x-rays aren't just one wavelength.
They're also on a spectrum, from soft x-rays to hard x-rays.
And there's a team, here in Christchurch, New Zealand,
who are doing something that, in hindsight, seems really obvious.
What if you take x-rays at several different frequencies
and then translate all those frequencies to different colours?
- Part of the light spectrum is the x-ray spectrum.
And in there, we've got a range of energies,
sometimes they're called soft and hard x-rays.
But the typical medical imaging device doesn't use that information.
Sometimes it's used in airport security.
They typically have a couple of detectors, layers,
on top of each other.
And they get those crude signals out
and then present it to the eye as two different colours.
But we're actually getting eight different colours
and we're doing a lot of computer processing
before we get a 3D image of what the materials are.
So we actually measure, that's bone, that's water, that's fat.
We started thinking about it-- myself, in about 2002.
The designers of the detector started 10 years before that.
It came out of high energy physics.
It came out of CERN's research and trying to find the Higgs Boson.
Equally importantly, they found a much better way
of imaging inside humans than they had before.
Each photon that comes in, we actually measure the energy of it.
Photons come in so fast, it has to do it very, very quickly.
The pixels are 110 microns square, so the size of a hair's breadth,
and each one of them is about three to four thousand transistors.
They're doing a lot of processing.
We've only got a two-dimensional image, so we've actually got to turn that
into a three-dimensional image. And that's called computed tomography.
We do a lot of computer processing
and produce 3D slices any way through the object.
With the resolution we've got,
we've got to solve tens of billions of equations.
And we've got to try and do that very quickly.
- The goal is to make it as easy as possible for people to understand.
For bone, you'd typically use white
because that's what people think is what bone should be.
But if you're looking at something like iodine,
a solution of iodine is clear.
So we typically assign red and most people in medicine
are used to seeing things assigned to different colours.
It's a combination of what looks good,
what's intuitive to them, what's easy to understand.
We've got to the point we can now test things in humans
and we're about to start our first clinical trial.
The challenges in going from where we were in 2006
on our first mouse, to being able to do the first human,
we had to move to the human energy range.
So the x-rays you need to get through a mouse
are much softer, lower energy
and we need to be able to do large areas of detectors
so you can actually scan someone in a reasonable timeframe.
And then there's the data handling issues.
Typically we think of scanning one litre of volume
giving us about 10 gigabytes of data.
Can you actually scan a large object and manage that kind of data?
At the moment our scanner uses about half as many x-rays
as a standard CT.
But if you think of imaging something like a wrist,
which is not radiosensitive, it's not a thyroid gland,
it's not a breast gland.
The actual dose from a wrist scan is very, very low.
Depending on which country you live in,
it's the equivalent of several hours to a day or two of background radiation.
Most x-ray detectors need to have a certain amount
of photons before you can measure them.
Otherwise you're in the electronic noise.
Whereas we work at very, very low count rates
and so we can measure the statistical, or the quantum noise quite easily.
So we can operate at lower doses.
Our goal is to keep the dose the same but provide 10 times as much information.
- There are all sorts of different ways of looking inside the body.
I'm really excited, in the next six months
we're going to scan lots of interesting bits,
like broken arms and gout in the fingers.
Maybe in a year's time, start looking at
more exciting things like diseases of blocked arteries.
We can actually say,
not just simply there's something absorbing,
but whether it is calcium or iodine or fat,
that's an injury, is there a bit of metal in there or whatever.
We can answer those questions.
And so we've got a great prospect of actually seeing a lot of things
that haven't been seen before.
- Thanks to all the team at Mars Bioimaging and the University of Canterbury.
Pull down the description for more about them and about their work.