In the last section we began a discussion of invasive
techniques. In this section, we begin by looking at what we call
non-invasive techniques. The key for non-invasive techniques is that it
does not hurt the organism when they’re being done.
Let’s begin by looking (on page two) at variety of
different types of non-invasive techniques. As you can see here, some of
these are ones that you have already heard of, like X-Rays and CAT scans and
other things. So let’s walk through each of these for a few minutes and
talk about each of them. As you probably know, some of these are already
used in medicine, so you’re a little bit more familiar with these than you
are with some of the other ones that we talked about in the last section.
The first one that we want to talk about are called x-rays
and shown on slide three. X-Rays are basically the typical X-Ray that you
see in your doctor’s office, but it can also be used to examine brain and
spinal structures. What is commonly done is to inject dyes. Dyes then go
into the brain and you can watch where the dye is. The dye then surrounds
different tumors and allows you to see the brain better. You can also
insert air into the spinal column and then rotate the table. As you do
that, the air can go up into ventricles of the brain and you can examine
them. The problem is when you do this technique, it gives you a massive
headache and it’s not very pleasant.
What are some advantages of X-rays? Well, as you can see
on slide four, they’re relatively cheap and they’re very good at looking at
basic things, such as brain structures. They’re very good at determining if
you have some primary brain damage such as blood; especially when you use
contrast mediums. However, as you can see in slide five, there are some
disadvantages. When you inject air, you get major headaches as we talked
about earlier. You can’t look at function very well, and of course you
can’t see the detail that you can see in other procedures that we have.
Related to x-rays (as we see in slide six) is Cerebral
Angiography. Basically Angiography is going to be looking at things within
the vascular system. What it uses are radio-opaque dyes. So, we inject a
particular type of dye into the vertebral or carotid artery and let it float
around in there for a while, kind of like we did with autoradiography. Then
we x-ray the brain. What happens is that the dyes block the x-rays and
allows you to see the brain arteries extremely well. Then you look for a
variety of different things. You might look for balloon shapes which would
indicate there is some kind of potential aneurysm beginning to occur and
would need to be taken care of. If you have some kind of deformity where
the artery is moved from where it should be, that would indicate some kind
of tumor or other problem.
Again, it’s a relatively straightforward technique, it’s
less expensive than some of the other techniques, but again it doesn’t give
you the detail. But, if you are looking for deformities in the vascular
system, this is probably a good way to go.
Well, let’s take a look at the next technique that
developed after x-rays. This is shown on slide seven, and is called
Computerized Axial Tomography, or what is called CT or CAT scans. Generally
the CT scan is a fancy x-ray. But it uses a computer to create the image.
The x-ray unit goes around the head and puts x-rays through a detector on
the opposite side. Ultimately what it does is gives you a picture of a
slice of tissue. It gives very good detail at that particular level. These
are pictures that you see in De Armond. What they have done is shot a
variety of different pictures. What you do normally is start at the bottom
or top and you take slices going from the ventral to the dorsal aspect of
the head. Then you go medial/lateral and then you go anterior/posterior.
So in essence what you do is three or four different views of the brain.
From that, you can get a pretty good idea of locations of particular damage
or particular anomalies.
Now related to CT scans are what we call PET scans. This
is called Positron Emission Tomography and is shown in slide eight. It’s
very similar to CAT scans and can be used for brain structures. However,
it’s not commonly used for structures today because we use other
techniques. Primarily what Positron Emission Tomography does is examine
brain functioning. When you do that, it gives you pretty good resolution
about what’s going on within the brain. What’s the procedure? Well, the
procedure (as we see in slide nine) is first make a radioactive label.
Usually what we do is use carbon 11 or oxygen 15 and we attach it to a
glucose molecule. We then inject the glucose molecules, which is basically
radioactive glucose into the brain or into the body. It then goes into the
brain and when it does that, it goes into particular parts of the brain that
is being used. And as we can see in slide 10, we’ve made the glucose hot,
we’ve put it into the patient, and now you’re transmitting particles of all
your cells. But the particles concentrate in a couple things. First the
concentrate in tumor sites because they’re highly vascular and they also
concentrate in places that use lots of glucose
When you’re thinking about things or doing a particular
behavior glucose is being used by the bran. Of course, when you do that,
that’s where the glucose is going to concentrate. Ultimately a scanner picks
up a particle and the computer makes a picture of where the glucose is
concentrated, just like it does in the CAT scan.
Again, as we see in slide 11, you can see where the tumors
are, you can determine which part of the brain’s operating and doing a
particular task (such as with movement, thinking, individual processing, or
whatever).
So what have we found with PET scans. Well as we see in
slide 12, as we look at some psychological / psychiatric disorders, people
with schizophrenia show lots more activity in frontal and occipital lodes
than normal people. Of course people who have depression have decreased
glucose levels than normal people. So ultimately, PET scans can be used for
a wide variety of disorders, and they’re very good at what they do.
What are some advantages of PET scans? Well as we see in
slide 13, they’re great for looking at brain functioning and helping us to
understand how the brain is working. For the most part they’re relatively
safe.
What are some disadvantages? Well, as we see in slide 14,
the cyclotron that makes the radioactive glucose is expensive, thus PET
scans are expensive. In addition, although we consider it to be a
non-invasive technique, it is actually an invasive technique because you’re
adding something into the organism. You can also get the label too hot.
That is, you get too much radioactivity which causes different problems.
Well, other technologies have come along. Two of these
technologies I want to talk about in some detail. The first of these is
called Magnetic Resonance Imagery, which we see in slide 15. It’s very
similar to a CAT scan, but instead of using X-rays, MRI’s use magnetic
fields. What it does is cause the nuclei, the atoms to be spin. When you
add particular radio frequencies they begin to emit frequencies as well.
Ultimately, what you do is have a detector to detect those frequencies and
make a picture. The most common atom that we look at is hydrogen.
MRI’s can be basically used to examine anything, but we
use it to examine brain structures. It’s great to determine things about
tumors, strokes, and other things such as hydrocephalus which is basically
water on the brain. But again, it can be used to examine anything. In
fact, I’m going to get an MRI on my little finger on Monday. So, it’s
something that we use, is very common, and relatively safe.
Well what’s it used for? Well as we see in slide 17, it’s
very good at detecting certain types of diseases, such as multiple
sclerosis. In multiple sclerosis, you have is a deterioration of the myelin
sheath surrounding neurons, which we will talk about in great detail later.
Normally in your brain, you have very little water in white matter because
these are pathways of axons. Thus, you get lots of resonance in gray
matter. What happens with MS is the white matter basically begins to
deteriorate and you develop what is called gliosis. As a result glial cells
move in and they have lots of water. So, it’s a very good detector of
things like MS. It’s also good for finding tumors, strokes, focal point
seizures and again as we said before, it can be used on any part of the body
as well.
What are some advantages of MRI’s? Well, as we can see in
slide 19, it can be used again on any structure. But more importantly, it
provides better detail than CT scans. It also doesn’t use X-rays. Finally,
it’s great for identifying different focal point seizures or different focal
points where small tumors may be beginning to develop.
What’s a disadvantage? Well, as we see in slide 20, MRI’s
are expensive. On my little finger it’ll probably cost $2,000. You’ll also
have lots of loud banging noises when you’re doing it which can be scary to
people. It’s lying in a long tube and you’re hearing all this noise going
around your head. It’s not a fun thing.
Well what’s the next technique that we want to look at?
Well the next technique is called Functional MRI’s and is shown in slide
21. They’re very similar to MRI’s but instead of looking only at
structures, they look at function. Here what we do is we look at oxygen
metabolism instead of hydrogen metabolism. And again, what we do is we have
the same kind of systems that we did before with a MRI, but basically you’re
just looking at a different mechanism. Basically this gives you higher
resolution than PET scans, so consequently you get better detail about
what’s going on in particular brain lesions.
What’s the next one; well as we see on slide 22, is Single
Photon Emission Computerized Tomography or what’s called Spect. Spect is
very similar to PET scan but it is just basically more refined.
The next technique that I want to talk about is called
super quantum interference device or what are called Squids and shown in
slide 23. Squid, in essence, is like an MRI and used to pick up changes in
magnetic fields. The idea is when neurons fire, they create changes in
magnetic fields. So what you could do is you could develop monitors to
basically look at that. So, changes in magnetic fields indicate changes in
neuro activity. The key about Squid is that you can monitor changes much
faster than the other techniques, in fact you can monitor changes at the
millisecond level. So it’s extremely, extremely sensitive and it’s more
sensitive than any other technique have out right now.
There are a couple studies that I want you to know about.
The first of these studies is in slide 24 by Williamson and Kauffman.
Basically what they did was they use SQUID to monitor the brain of a person
playing the piano. Basically what they found was that the brain heard the
sounds in different places and were louder than if they were quiet. In
addition, the brain distance between areas that hear low Cs and high Cs on
the piano were basically the same distance from middle C. So, what you have
on the temporal lobe where you listen to and hear information is a spot
where low C hits. If you go to middle C or high C, you basically have those
changes that are basically the same identical distance that you have from
low C to middle C, and middle C to high C.
Another study looked at faces. Basically what they found
(and shown in slide 25) is that the places where the brain remembers faces
is different from where it remembers objects. Faces are often recognized in
the right hemisphere (where it specializes in spatial configurations)
primarily in the occipital cortex and others. Objects such as spatulas are
basically processed where the particular object is going to be used (frontal
lobes within the motor cortex). In essence you want an object to be located
close to where you want to use the information. Whereas faces are more
abstract and you want it in other locations that specializes in more spatial
types of diagnosis and things.
Well let’s look onto the next system. That is called
Magnetic Source Imagery or MSI. Basically what MSI does is use Squids to
measure ions in the brain or other areas. Magnetic Source Imagery basically
uses magneto encepholography which measures magnetic fields of the brain or
magneto cardiography which is measuring magnetic fields of the heart. It is
very similar to Squid but basically uses SQUID devices to get better images
for each of those structures.
Now, I’ve given you on slide 27, a variety of different
techniques of where you can look at for more information, especially for
Squid or other general medical techniques. So you might want to look at
these if you want more information about each of these techniques. That
kind of gives you a little bit better idea and understanding. Some of these
sites have pictures and assorted other things.
In the next section, we’re going to begin talking about
neuro-psychological techniques for examining brain functioning and structure
and so until that time, have a great day.
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