What do Physicists do in… What do Physicists do in…

““REAL LIFEREAL LIFE””

Many work with Many work with doctors in the field of doctors in the field of

MedicineMedicine

Doctors often need to look Doctors often need to look inside our bodies without inside our bodies without

cutting them open….cutting them open….

Some you may have heard of…Some you may have heard of…

X-raysX-rays…..…..CTCT scans….. scans…..MRIMRI scansscansAnd new ones you may not have And new ones you may not have

heard of yet….heard of yet….

PETPET scans….. scans…..MEGMEG

are essential in the development of many scanning technologies

Here is Here is youryour chance chance to…to…

Find out the basics of how these Find out the basics of how these scans work scans work

See how important physics is to See how important physics is to modern medicine.modern medicine.

X-raysX-rays Very little Very little ordinary ordinary

lightlight can pass through can pass through skin. It’s either skin. It’s either absorbedabsorbed at the at the surface or surface or reflectedreflected back….. back…..

To “see” inside we To “see” inside we need a kind of “light” need a kind of “light” with with more energymore energy……

Skin

Ordinary Light

X rays

Taking “X rays”Taking “X rays”

The patient is placed in front

of a source of X RAYS

X ray Tube

A photo graphic plate is

placed on the other

side of the patient

Most of the X rays

pass through

the patient’s body…….

X-rays are absorbed by bone X-rays are absorbed by bone but can pass through skin and but can pass through skin and

soft tissuesoft tissue

bone

Soft tissue

Photographic

plate

X rays that are absorbed in the photographic plate cause chemical changes. These show as darkened areas when the plate is developed.

X-rays are also X-rays are also partlypartly absorbed by absorbed by some tissues in the body this creates a some tissues in the body this creates a

more subtle picture.more subtle picture.

bone

Soft tissue

Photographic

plate

What part of the body do these X Rays show?What part of the body do these X Rays show?

Answer:

A knee

Advantages of Basic X ray Advantages of Basic X ray ImagingImaging

X rays are easy to produceX rays are easy to produce X ray machines are relatively cheapX ray machines are relatively cheap In controlled doses X ray images are In controlled doses X ray images are

safe to the patientsafe to the patient

Disadvantages of X ray Disadvantages of X ray ImagingImaging

In large doses X rays can be harmful In large doses X rays can be harmful to healthto health

Images are only “shadow prints” in Images are only “shadow prints” in one “plane”…..no 3D informationone “plane”…..no 3D information

Imaging of soft tissues and organs is Imaging of soft tissues and organs is not always very detailed.not always very detailed.

True or False Challenge…True or False Challenge…1.1. X rays are made of the same “stuff” X rays are made of the same “stuff”

as visible light. They are both forms as visible light. They are both forms of “electromagnetic radiation”.of “electromagnetic radiation”.

2.2. X rays were discovered completely X rays were discovered completely by accident during a physics by accident during a physics experiment carried out in 1965.experiment carried out in 1965.

3.3. X rays can damage healthy tissues.X rays can damage healthy tissues.

CT ScansCT ScansCTCT or “CAT” scans take X ray imaging to or “CAT” scans take X ray imaging to

““CC” stands for “Computed”” stands for “Computed”

““TT” stands for “ Tomography”” stands for “ Tomography”

In short….In short….CT scanners are CT scanners are complex X ray complex X ray machinesmachinesattached to attached to very very clever clever computerscomputersusing using complicated complicated mathematicsmathematics to to build up build up images of our insides.images of our insides.

The patient is placed on a bedThe patient is placed on a bed

The scanner (X ray machine) is the shape of The scanner (X ray machine) is the shape of a ringa ring

The patient is slowly moved through the The patient is slowly moved through the ring as the scan takes place…ring as the scan takes place…

Looking end on….Looking end on….

X ray tube

X ray detector

Patient

X Rays are produced in an X ray tube, pass through the patient and are detected by the detector

The scanner rotates the X ray tube and detector so the patient is scanned from all angles

There are no photographic plates in CT There are no photographic plates in CT scanners. All images are created by scanners. All images are created by

computers using the information they computers using the information they receive from the x-ray detectorreceive from the x-ray detector

The image produced is like a “slice” The image produced is like a “slice” through the body. through the body.

ribs

spine

Advantages of CT scansAdvantages of CT scans

Images are like “slices” Images are like “slices” Compared other scanners (MRI and Compared other scanners (MRI and

PET) CT machines are quite cheap.PET) CT machines are quite cheap.

Disadvantages of CTDisadvantages of CT

Still use X rays that can damage Still use X rays that can damage healthy tissues (in large doses).healthy tissues (in large doses).

Imaging of soft tissues is improved Imaging of soft tissues is improved but still not always as detailed as but still not always as detailed as doctors require.doctors require.

True or False Challenge…True or False Challenge…

4.4. CT stands for Complex Tomography.CT stands for Complex Tomography.

5.5. CT scans make images of your insides in CT scans make images of your insides in slices. Computers can now take these slices. Computers can now take these slices and make a 3D picture of your slices and make a 3D picture of your insides.insides.

6.6. With CT scans the patient receives a With CT scans the patient receives a lower dose of x rays than with a standard lower dose of x rays than with a standard X ray machine.X ray machine.

MRIMRI What do the letters stand for?What do the letters stand for?

MM……….. Magnetic……….. Magnetic

RR………… Resonance………… Resonance

II…………. Imaging…………. Imaging

MRI scanners MRI scanners do notdo not use use X raysX rays..

MRI Explained...MRI Explained...

Your science studies Your science studies have shown you have shown you that your body is that your body is made up of living made up of living

cellscells……

Which are made up Which are made up

of of moleculesmolecules … …

Which are made up Which are made up

of of atomsatoms

electron

neutron

proton

The simplest atom is…The simplest atom is…

Hydrogen1 electron

1 proton

It’s nucleus contains just one proton

In the 1940’s physicists In the 1940’s physicists discovered that the nuclei of discovered that the nuclei of some atoms have a property some atoms have a property

called “SPIN”…called “SPIN”……….Like a wobbling spinning top..Like a wobbling spinning top.

This causes the nucleus act like a tiny magnet….

N

S

After many years of investigation After many years of investigation physicists found they could affect the physicists found they could affect the

tiny nuclear magnets of hydrogen tiny nuclear magnets of hydrogen atoms using very strong atoms using very strong magnetsmagnets and and

radio wavesradio waves……

Bring in the magnets….Bring in the magnets….

S N

Note: The nuclear magnets can line up in two possible directions A pulse of radio waves can cause some of the

nuclear magnets absorb energy and “flip”

This high energy situation cannot be sustained for long. Many will “flip” back….When this happens energy is released as a tiny

pulse of radio waves !!!

… ….watch how the magnetic field affects the tiny nuclear magnets.watch how the magnetic field affects the tiny nuclear magnets

This tiny pulse of radio This tiny pulse of radio waves that can be detected waves that can be detected

and analysed. and analysed. The timing, and the energy of The timing, and the energy of

these signals, reveals these signals, reveals information about the information about the HydrogenHydrogen

atoms and what types of atoms and what types of molecules they are attached to.molecules they are attached to.

So what has all this got to do So what has all this got to do with looking inside your body?with looking inside your body?

What is your body mostly made of?What is your body mostly made of?

What is the chemical name of water? What is the chemical name of water?

HH22OOHydrogen in the most abundant element in Hydrogen in the most abundant element in your body (approx 63% of all the atoms are your body (approx 63% of all the atoms are

H)H)

Organic molecules Organic molecules that make up tissues likethat make up tissues like

FATFATMUSCLEMUSCLE

TENDONSTENDONS etc. etc.

contain a large number of Hydrogen contain a large number of Hydrogen atomsatoms

It took physicists over It took physicists over 4040 years to turn their years to turn their discovery of nuclear magnets into images of discovery of nuclear magnets into images of

the human body.the human body.But the results are amazing…But the results are amazing…

All this from manipulating the magnetic properties of hydrogen nuclei !

The patient is placed on a bed and then The patient is placed on a bed and then moved into a large hollow tube.moved into a large hollow tube.

The tube contains a very powerful The tube contains a very powerful magnetmagnet….….

Using an MRI Scanner…

Most MRI scanners use Most MRI scanners use

magnetsmagnetsAn electric current passes through a massive coil made of a special “superconducting” material

This creates a very strong magnet (x 20000 times stronger than earths magnetic field)

This may seem like a really easy way to create a strong magnet

but there is a catch……

Superconducting materials Superconducting materials only work correctly when they only work correctly when they

are really cold…..are really cold…..But not just cold But not just cold

like freezer like freezer temperatures….temperatures….

Can you guess how Can you guess how cold?cold?

degrees CelsiusThat’s colder than on the surface of Pluto!

To achieve these temperatures To achieve these temperatures the superconducting coils need the superconducting coils need

to sit in a container filled to sit in a container filled with…with…

Thankfully the patient is insulated from this extremely low temperature whilst inside the magnet.

The magnet used is The magnet used is incredibly strong!incredibly strong!

Stand 1m away with a large spanner Stand 1m away with a large spanner in your hand…. you would not be in your hand…. you would not be able to hold on to it.able to hold on to it.

Patients have to remove all metallic Patients have to remove all metallic objects and credit cards…objects and credit cards…

Patients may have metal objects Patients may have metal objects inside their bodies…inside their bodies…

Patients may be asked the Patients may be asked the following questions:following questions:

Have you ever worked in the army or Have you ever worked in the army or metal working industry?metal working industry?Metal fragments (especially in the eye) could become dislodgedMetal fragments (especially in the eye) could become dislodged

Do you have a pacemaker?Do you have a pacemaker?If yes you cannot have an MRI scanIf yes you cannot have an MRI scan

Do you have any dental implantsDo you have any dental implantsSome could become magnetisedSome could become magnetised

Do you have any metal pins or staples in Do you have any metal pins or staples in your body?your body?Some could become magnetised and need to be checked that they Some could become magnetised and need to be checked that they will hold in place during the scanwill hold in place during the scan

With the patient safety check complete the scan can begin…The part of the body to The part of the body to

be scanned is placed be scanned is placed in the centre of the in the centre of the primary magnetprimary magnet

XThe magnet field produced has to be very steady and strong

This field causes the Hydrogen nuclei in the patients body to line up with the field

X

Three further coils are embedded into the tube….GRADIENT MAGNETS… these are used to fine tune the magnetic field so particular body parts and tissue types can be focused on.The patient will know when these magnets are switched on…they can make a loud banging noise.More coils provide a pulse of radio waves that cause some of the “nuclear magnets” to flip….

The machine waits and records any radio signals that are then emitted by the patients body…..

This information is sent to a This information is sent to a computer which uses it to build computer which uses it to build

up an image ….up an image ….

CT compared to MRICT compared to MRI

CT scanners scan a patient in “slices” but CT scanners scan a patient in “slices” but the angle of the slice depends on how the the angle of the slice depends on how the patient is positioned in the machine.patient is positioned in the machine.

MRI scanners scan a whole section of the MRI scanners scan a whole section of the body then the doctor can request to view body then the doctor can request to view

a slice of the patient at a slice of the patient at anyany angle… angle… MRI scans can reveal a lot more detail.MRI scans can reveal a lot more detail.

View an MRI scan from any View an MRI scan from any angle..angle..

Are MRI Scans Safe?Are MRI Scans Safe?

Research has failed to show up any risk to healthResearch has failed to show up any risk to health Patients do not feel a thing….not even a tingle!Patients do not feel a thing….not even a tingle! Scans typically take 30 mins+Scans typically take 30 mins+ Staying still and putting up with clanging noises Staying still and putting up with clanging noises

are the only discomforts a patient has to suffer!are the only discomforts a patient has to suffer!

a further group of people may find a further group of people may find it impossible to have an MRI it impossible to have an MRI

scan….!scan….!

What is the name of the What is the name of the condition that causes a fear condition that causes a fear

of…of…

““Claustrophobia”Claustrophobia”

Many claustrophobics cannot have MRI scans

True or False Challenge?True or False Challenge?

7.7. It is dangerous for a patient to stay It is dangerous for a patient to stay in an MRI scanner for too longin an MRI scanner for too long

88.. Superconducting magnets are cheap Superconducting magnets are cheap to make and use.to make and use.

9. 9. Claustrophobics are not allowed to Claustrophobics are not allowed to have CT scanshave CT scans

““snapshot”snapshot” images are useful images are usefulbut doctors sometimes need but doctors sometimes need “real “real time”time” pictures of how parts of your pictures of how parts of your

body are functioning…body are functioning…e.g. How your heart is e.g. How your heart is

functioning.functioning.Moving images can be achieved with MRI but PET scanning can give excellent results…

Introductions to Introductions to PETPET((positron emission tomographypositron emission tomography))

PETPET SCANNERS LOOK LIKE SCANNERS LOOK LIKE CTCT SCANNERS…SCANNERS…

The key The key differences:differences:

--NONO X RAY TUBE. X RAY TUBE.

-The ring is -The ring is surrounded by surrounded by ““Gamma RayGamma Ray” ” detectorsdetectors

What are “gamma rays” What are “gamma rays” and “positrons” ?and “positrons” ?

A little detour….

You will have heard of…You will have heard of…ElectronsElectrons

ProtonsProtons

NeutronsNeutronsThese are the building blocks of atoms.These are the building blocks of atoms.

Physicists have discovered a whole host of Physicists have discovered a whole host of otherother particles that exist !!!particles that exist !!!

AND ASWELL:AND ASWELL: Every particle has it’s own Every particle has it’s own ANTI ANTI PARTICLEPARTICLE……

Its….Its….

equivalentequivalent

The antiparticle of the electron The antiparticle of the electron is called a…is called a…

When an electron and a positron meet When an electron and a positron meet they annihilate…they annihilate…

The energy released creates 2 gamma rays

PET scan patients are injected PET scan patients are injected with a specially created substance with a specially created substance

called a “RADIOTRACER”….called a “RADIOTRACER”….

Usually a “Radioactive” type Usually a “Radioactive” type of glucose.of glucose.

The radiotracer is a source of positrons which leads to the production of gamma

rays…

INSIDE THE PATIENTS BODY!

These pass through the patients body and are picked

up by the scanner.

Looking at the scanner: end on….Looking at the scanner: end on….

Ring of gamma ray detectors

Patient

The radio tracer produces positrons which annihilate with electrons in the patients body producing pairs of gamma rays.

The energy and position of all the gamma rays are recorded and turned into an image by a computer.

The radiotracer concentrates itself The radiotracer concentrates itself in certain tissue types…in certain tissue types…

This glucose type radiotracer has concentrated itself in high glucose using cells like the brain, kidneys and cancer cells.

PET Scans are very PET Scans are very expensive…expensive…

The biggest cost is in the production of The biggest cost is in the production of the RADIOTRACERS.the RADIOTRACERS.

The hospital needs to have access to a The hospital needs to have access to a ““CYCLOTRONCYCLOTRON” to create them” to create them

(several million euro to buy one!)(several million euro to buy one!)

Radiotracers have to be used straight after they are Radiotracers have to be used straight after they are produced….they cannot be stored.produced….they cannot be stored.

True or False?True or False?

10.10. PET scanning poses no risk to PET scanning poses no risk to patient health. Doctors can use them patient health. Doctors can use them as often as they like.as often as they like.

11.11. “Antimatter” is just an idea “Antimatter” is just an idea invented by science fiction writers.invented by science fiction writers.

12.12. Gamma rays are also a form of Gamma rays are also a form of “electromagnetic radiation” like light “electromagnetic radiation” like light and X rays.and X rays.

Brief Introduction to Brief Introduction to MEGMEG(magnetoencephalography)(magnetoencephalography)

MEG is different to all the other techniques…MEG is different to all the other techniques…

It doesn’t put anything into a patients body….It doesn’t put anything into a patients body….

No X rays/Strong Magnetic Fields/Radio No X rays/Strong Magnetic Fields/Radio waves/Radiotracers.waves/Radiotracers.

It just measures something It just measures something that is already there…that is already there…

Your body is full of tiny electric Your body is full of tiny electric currents!currents!

These tiny currents produce tiny magnetic fieldsThese tiny currents produce tiny magnetic fields

MEG is able to measure some of these.MEG is able to measure some of these.

MEG is mostly used to MEG is mostly used to image image brain activitybrain activity..

MEG scanners MEG scanners measure tiny magnetic measure tiny magnetic fieldsfields produced by produced by electrical brain electrical brain activity.activity.

These fields are so These fields are so weak (weak (10,000 million10,000 million times weaker that the times weaker that the earths magnetic field) earths magnetic field) that the scanner needs that the scanner needs to be in a specially to be in a specially shielded room.shielded room.

So now you know how So now you know how important PHYSICS is to important PHYSICS is to

MEDICINEMEDICINE