1. What do Physicists do in… “REAL LIFE”
Many work with doctors in the field of
Medicine

2. are essential in the development of many scanning technologies
Doctors often need to look inside our bodies without cutting them open….
"Medical Physicists"
are essential in the development of many scanning technologies
Some you may have heard of…
X-rays…..CT scans…..MRI scans
And new ones you may not have heard of yet….
PET scans…..MEG

3. Here is your chance to… Find out the basics of how these scans work
See how important physics is to modern medicine.

4. X-rays Skin X rays Ordinary Light
Very little ordinary light can pass through skin. It’s either absorbed at the surface or reflected back…..
To “see” inside we need a kind of “light” with more energy…
X rays
Skin

5. 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…….

6. X-rays are absorbed by bone but can pass through skin and soft tissue
Photographic
plate
bone
X rays that are absorbed in the photographic plate cause chemical changes. These show as darkened areas when the plate is developed.
Soft tissue

7. X-rays are also partly absorbed by some tissues in the body this creates a more subtle picture.
Photographic
plate
bone
Soft tissue

8. What part of the body do these X Rays show?
A knee
Answer:

9. Advantages of Basic X ray Imaging
X rays are easy to produce
X ray machines are relatively cheap
In controlled doses X ray images are safe to the patient

10. Disadvantages of X ray Imaging
In large doses X rays can be harmful to health
Images are only “shadow prints” in one “plane”…..no 3D information
Imaging of soft tissues and organs is not always very detailed.

11. True or False Challenge…
X rays are made of the same “stuff” as visible light. They are both forms of “electromagnetic radiation”.
X rays were discovered completely by accident during a physics experiment carried out in 1965.
X rays can damage healthy tissues.

12. CT Scans another level…. CT or “CAT” scans take X ray imaging to
“C” stands for “Computed”
“T” stands for “ Tomography”
another level….

13. In short…. CT scanners are complex X ray machines attached to
very clever
computers
using complicated
mathematics to
build up
images of our insides.

14. The patient is placed on a bed
The scanner (X ray machine) is the shape of a ring
The patient is slowly moved through the ring as the scan takes place…

15. Looking end on…. X ray tube
X Rays are produced in an X ray tube, pass through the patient and are detected by the detector
Patient
The scanner rotates the X ray tube and detector so the patient is scanned from all angles
X ray detector

16. The image produced is like a “slice” through the body.
There are no photographic plates in CT scanners. All images are created by computers using the information they receive from the x-ray detector
ribs
spine
The image produced is like a “slice” through the body.

17. Advantages of CT scans Images are like “slices”
Compared other scanners (MRI and PET) CT machines are quite cheap.

18. Disadvantages of CT
Still use X rays that can damage healthy tissues (in large doses).
Imaging of soft tissues is improved but still not always as detailed as doctors require.

19. True or False Challenge…
CT stands for Complex Tomography.
CT scans make images of your insides in slices. Computers can now take these slices and make a 3D picture of your insides.
With CT scans the patient receives a lower dose of x rays than with a standard X ray machine.

20. MRI scanners do not use X rays.
What do the letters stand for?
M……….. Magnetic
R………… Resonance
I…………. Imaging
MRI scanners do not use X rays.

21. MRI Explained...
Your science studies have shown you that your body is made up of living cells… Which are made up of molecules … Which are made up of atoms

22. It’s nucleus contains just one proton
The simplest atom is…
1 electron
Hydrogen
1 proton
It’s nucleus contains just one proton

23. In the 1940’s physicists discovered that the nuclei of some atoms have a property called “SPIN”…
….Like a wobbling spinning top.
This causes the nucleus act like a tiny magnet…. N S

24. After many years of investigation physicists found they could affect the tiny nuclear magnets of hydrogen atoms using very strong magnets and radio waves…
Bring in the magnets….
This high energy situation cannot be sustained for long. Many will “flip” back….
….watch how the magnetic field affects the tiny nuclear magnets
When this happens energy is released as a tiny pulse of radio waves !!! S N
A pulse of radio waves can cause some of the nuclear magnets absorb energy and “flip”
Note: The nuclear magnets can line up in two possible directions

25. This tiny pulse of radio waves that can be detected and analysed.
The timing, and the energy of these signals, reveals information about the Hydrogen atoms and what types of molecules they are attached to.

26. So what has all this got to do with looking inside your body?
What is your body mostly made of?
What is the chemical name of water?
H2O
Hydrogen in the most abundant element in your body (approx 63% of all the atoms are H)
Water

27. Organic molecules that make up tissues like FAT MUSCLE TENDONS etc.
contain a large number of Hydrogen atoms

28. It took physicists over 40 years to turn their discovery of nuclear magnets into images of the human body. But the results are amazing…
All this from manipulating the magnetic properties of hydrogen nuclei !

29. The patient is placed on a bed and then moved into a large hollow tube.
Using an MRI Scanner…
The tube contains a very powerful magnet….

30. Superconducting Most MRI scanners use magnets but there is a catch……
An electric current passes through a massive coil made of a special “superconducting” material
This creates a very strong magnet (x times stronger than earths magnetic field)
This may seem like a really easy way to create a strong magnet
but there is a catch……

31. That’s colder than on the surface of Pluto!
Superconducting materials only work correctly when they are really cold…..
But not just cold like freezer temperatures….
Can you guess how cold?
-269
That’s colder than on the surface of Pluto!
degrees Celsius

32. To achieve these temperatures the superconducting coils need to sit in a container filled with…
Liquid Helium
Thankfully the patient is insulated from this extremely low temperature whilst inside the magnet.

33. The magnet used is incredibly strong!
Stand 1m away with a large spanner in your hand…. you would not be able to hold on to it.
Patients have to remove all metallic objects and credit cards…
Patients may have metal objects inside their bodies…

34. Patients may be asked the following questions:
Have you ever worked in the army or metal working industry?
Metal fragments (especially in the eye) could become dislodged
Do you have a pacemaker?
If yes you cannot have an MRI scan
Do you have any dental implants
Some could become magnetised
Do you have any metal pins or staples in your body?
Some could become magnetised and need to be checked that they will hold in place during the scan

35. With the patient safety check complete the scan can begin…
The part of the body to be scanned is placed in the centre of the primary magnet X
The 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

36. Three further coils are embedded into the tube…
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. X
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…..

37. This information is sent to a computer which uses it to build up an image ….

38. CT compared to MRI
CT scanners scan a patient in “slices” but the angle of the slice depends on how the patient is positioned in the machine.
MRI scanners scan a whole section of the body then the doctor can request to view a slice of the patient at any angle…
MRI scans can reveal a lot more detail.

39. View an MRI scan from any angle..

40. Are MRI Scans Safe?
Research has failed to show up any risk to health
Patients do not feel a thing….not even a tingle!
Scans typically take 30 mins+
Staying still and putting up with clanging noises are the only discomforts a patient has to suffer!
a further group of people may find it impossible to have an MRI scan….!
BUT

41. What is the name of the condition that causes a fear of…
confined spaces
“Claustrophobia”
Many claustrophobics cannot have MRI scans

42. True or False Challenge?
It is dangerous for a patient to stay in an MRI scanner for too long
8. Superconducting magnets are cheap to make and use.
9. Claustrophobics are not allowed to have CT scans

43. Introductions to PET (positron emission tomography)
“snapshot” images are useful
but doctors sometimes need “real time” pictures of how parts of your body are functioning…
e.g. How your heart is
functioning.
Moving images can be achieved with MRI but PET scanning can give excellent results…

44. PET SCANNERS LOOK LIKE CT SCANNERS…
The key differences:
-NO X RAY TUBE.
-The ring is surrounded by “Gamma Ray” detectors

45. What are “gamma rays” and “positrons” ?
A little detour….

46. You will have heard of… Antimatter Electrons Protons Neutrons
These are the building blocks of atoms.
Physicists have discovered a whole host of other particles that exist !!!
AND ASWELL: Every particle has it’s own ANTI PARTICLE…
Its….
equivalent
Antimatter

47. The antiparticle of the electron is called a…
POSITRON
When an electron and a positron meet they annihilate…
The energy released creates 2 gamma rays

48. PET scan patients are injected with a specially created substance called a “RADIOTRACER”….
Usually a “Radioactive” type
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.

49. Looking at the scanner: end on….
The radio tracer produces positrons which annihilate with electrons in the patients body producing pairs of gamma rays.
Patient
The energy and position of all the gamma rays are recorded and turned into an image by a computer.
Ring of gamma ray detectors

50. The radiotracer concentrates itself in certain tissue types…
This glucose type radiotracer has concentrated itself in high glucose using cells like the brain, kidneys and cancer cells.

51. PET Scans are very expensive…
The biggest cost is in the production of the RADIOTRACERS.
The hospital needs to have access to a “CYCLOTRON” to create them (several million euro to buy one!)
Radiotracers have to be used straight after they are produced….they cannot be stored.

52. True or False?
10. PET scanning poses no risk to patient health. Doctors can use them as often as they like.
11. “Antimatter” is just an idea invented by science fiction writers.
12. Gamma rays are also a form of “electromagnetic radiation” like light and X rays.

53. Brief Introduction to MEG (magnetoencephalography)
MEG is different to all the other techniques…
It doesn’t put anything into a patients body….
No X rays/Strong Magnetic Fields/Radio waves/Radiotracers.
It just measures something that is already there…

54. Your body is full of tiny electric currents!
These tiny currents produce tiny magnetic fields
MEG is able to measure some of these.

55. MEG is mostly used to image brain activity.
MEG scanners measure tiny magnetic fields produced by electrical brain activity.
These fields are so weak (10,000 million times weaker that the earths magnetic field) that the scanner needs to be in a specially shielded room.

56. So now you know how important PHYSICS is to MEDICINE
MRI CT
MEG
X rays
PET