" Physics applications in Imaging technology"

1. Overview On Applications of
Radiological Physics in Medical
Industry
K.K.D.Ramesh,
Chief Physicist & RSO,
Manipal Super Specialty
Hospital,

2. Aim
 To create an Idea about how the
Physics principles & Engineering
Technology are used in Radiation
generating equipments in Medical
industry

3. Introduction
 Medical Industry is one of the emerging
sector in India, all MNC companies like
Siemens, Philips, GE, Elekta, Varian are
considering India is a good market as
availability of resources and manpower.
So Software, Biomedical and
Mechanical people demand will more
in this field.

4.  Use of high energy EM waves
(Radiation) rapidly increasing in Health
care industry.
 Especially in diagnosis with the help of
X-ray , CT, MRI, & PET have made
drastic revolution in diagnosis
application with minimal non-invasive
surgeries.

5. WHAT IS RADIATION?
5
Emission of energy as electromagnetic waves or as a
moving subatomic particles which causes ionization
A) Electromagnetic waves/spectrum
Includes visible light, radio waves, gamma rays, and X-
rays
 Have an associated wavelength and frequency.
Ionizing Non-Ionizing

6. TYPES OF RADIATION
6
ELECTROMAGNETIC OR
PHOTONS
(i) Ionizing (ii) Non-Ionizing
B. PARTICLE: Electron , Alpha ,
Neutron, Proton,
(i) Ionizing

7. WHAT IS IONIZING RADIATION ?
7
The Ionizing radiation has capability to
remove particles or electrons from an
atom.
Electromagnetic
X rays , Gamma rays
Particle Nitrogenous bases (purine & pyrimidine)
Electron , Alpha , Neutron, Proton,

8. HOW RADIATIONS INTERACTS ?
8
Ionizing radiation has enough energy to
rip the electrons from their atoms,
destroying the molecules. This can lead
to DNA damage, which in turn leads to
cell death, and damaged tissues and
organs.
In a cell, ionization can trigger off:
Either an effective repair mechanism
with subsequent correct cell division,
Or a faulty repair mechanism resulting
in the appearance of cancerous cells or
the death of the cells.

9. Coherent scattering
 Classical scattering or Rayleigh scattering
No energy is changed into electronic motion
No energy is absorbed in the medium
The only effect is the scattering of the photon
at small angles.
 In high Z materials and with photons of
low energy
K
L
M
λ
λ
x_ray_coherent_scattering.vlc

10.  A photon interacts with an atom and
ejects one of the orbital electrons.
Photoelectric effect (1)
hν-EB
x_ray_photoelectric.vlc

11. Photoelectric effect (2)
 τ/ρ ∝ Z3
/E3
 The angular
distribution of
electrons depends on
the photon energy.
≈15 keV
L absorption edge
≈88 keV
K absorption
edge

12. Compton effect (1)
 The photon interacts with an atomic
electron as though it were a “free”
electron.
The law of conservation of energy
The law of conservation of momentum








−
−
+= 1
1
1
22
2
00
cv
cmhh
/
'νν
θφ
ν
θφ
νν
sin
/
sin
'
cos
/
cos
'
×
−
=
×
−
+=
22
0
22
0
1
1
cv
vm
c
h
cv
vm
c
h
c
h
K
L
M
hν θ
φ
hν’
Free
electron
Compto
n
electron
…………(1)
………(2)
…...…………(3)
_ray_compton_scattering (1).vlc

14. Compton effect (2)
α = hν0/m0c2
= hν0/0.511
)cos(
)cos(
φα
φα
ν
−+
−
=
11
1
0hE
)cos(
'
φα
νν
−+
=
11
1
0hh
hν0
θ
φ
hν’
Free electron
E
By (1), (2), (3)

15. Pair production
 The photon interacts
with the
electromagnetic field
of an atomic nucleus.
 The threshold energy
is 1.02 MeV.
 The total kinetic
energy for the
electron-positron pair
is (hν-1.02) MeV.
hν
E-
E+
+
-
0.51 MeV
0.51 MeV
Positron annihilation
x_ray_pair_production.vlc

16. The probability of pair production
 Π ∝ Z2
/atom

17. Many work with doctors
in the field of
MedicineMedicine

18. Doctors often need to look inside our
bodies without cutting them open….
Some you may have heard of…Some you may have heard of…
X-raysX-rays…..CTCT scans…..MRIMRI scans,
PETPET scans…..
And new ones you may not haveAnd new ones you may not have
heard of yet….heard of yet….
are essential in the development of many scanning technologies

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

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

21. 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…….

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

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

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

25. 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

26. CT Scans
CTCT scans take X ray imaging to
“CC” stands for “Computed”
“TT” stands for “ Tomography”

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

28. 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 ringThe patient is slowly moved through the ring
as the scan takes place…as the scan takes place…

29. 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

30. There are no photographic plates in CT scanners. All
images are created by computers using the information
they receive from the x-ray detector
The image produced is like a “slice” through
the body.
ribs
spine
CT Scan.mp4

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

32. 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.

33. MRI
What do the letters stand for?
MM……….. Magnetic
RR………… Resonance
II…………. Imaging
MRI scannersMRI scanners do notdo not useuse X raysX rays..

34. MRI Explained...
Your science studies
have shown you that
your body is made up
of living cellscells…
Which are made up of
moleculesmolecules …
Which are made up of
atomsatoms
electron
neutron
proton

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

36. 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

37. After many years of investigation physicists found
they could affect the tiny nuclear magnets of
hydrogen atoms using very strong magnets and
radio waves…
S N
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 !!!
Bring in the magnets….Bring in the magnets….

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

39. 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?
HH22OO
Hydrogen in the most abundant element in yourHydrogen in the most abundant element in your
body (approx 63% of all the atoms are H)body (approx 63% of all the atoms are H)

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

41. 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 !

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

43. Most MRI scanners use
magnets
An 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……

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

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

46. 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 metallicPatients have to remove all metallic
objects and credit cards…objects and credit cards…
 Patients may have metal objects insidePatients may have metal objects inside
their bodies…their bodies…

47. 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 dislodgedMetal fragments (especially in the eye) could become dislodged
 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 implants
Some could become magnetisedSome could become magnetised
 Do you have any metal pins or staples in
your body?
Some could become magnetised and need to be checked that theySome could become magnetised and need to be checked that they
will hold in place during the scanwill hold in place during the scan

48. 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 magnetprimary 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

49. 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…..

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

51. 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 anyany
angle…
 MRI scans can reveal a lot more detail.

52. View an MRI scan from any angle..

53. Are MRI Scans Safe?
 Research 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 are
the only discomforts a patient has to suffer!
a further group of people may find ita further group of people may find it
impossible to have an MRI scan….!impossible to have an MRI scan….!

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

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

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

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

58. You will have heard of…
Electrons
Protons
Neutrons
These are the building blocks of atoms.These are the building blocks of atoms.
Physicists have discovered a whole host ofPhysicists have discovered a whole host of otherother particlesparticles
that exist !!!that exist !!!
AND ASWELL:AND ASWELL: Every particle has it’s ownEvery particle has it’s own ANTIANTI
PARTICLEPARTICLE……
Its….Its….
equivalentequivalent

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

60. 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.

61. 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.

62. 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.

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

64. Radiation therapy
Utilizes Medical Linear
Accelerators for External radiation
&
 Radioactive sources for the
internal Radiation/Brachytherapy
How a Linear Accelerator Works - HD.mp4
What is HDR Brachytherapy.mp4

65. So now you know how important
PHYSICS is to MEDICINE

66. Thanks for your Attention