Proton therapy is a type of radiation therapy that uses proton beams to treat tumors. Proton beams deposit most of their radiation in the tumor, minimizing dose to surrounding healthy tissue. This allows higher tumor doses while reducing side effects. Protons have a finite range, so their energy can be precisely controlled to target the tumor. Multiple proton energies are used to spread the beam over the tumor distance and create a uniform dose called a spread-out Bragg peak. Proton beams are generated by cyclotrons or synchrotrons and the beam is manipulated and shaped using magnetic and material scattering and modulation to conform the dose to the tumor. Proton therapy is used to treat various cancers such as eye tumors, brain tumors, and prostate

1. PROTON THERAPY
Ankita Pandey

2. WHAT IS THE PROTON THERAPY
• Proton therapy is a type of external beam
radiation therapy — a treatment that uses
high-energy proton beams to treat tumors

5. Rationale behind radiotherapy
• High tumor dose
• Lower dose to normal organs

6. PROBLEMS WITH PHOTON
THERAPY TREATMENT

7. MORE EXIT
DOSE
EXPONENTIAL
DOSE FALL OF
MORE TISSUE
IRRADIATION
LOW LET

8. EXIT DOSE
INCREASES
Dmax
increases

9. DOES PROTON THERAPY HAS
SOLUTION ?

10. Dose rises
slowly with
depth
Rapid
dose fall
off
No tissue
irradiated
Tissue recieves low
dose

13. PROTON RADIOBIOLOGY

14. LET and RBE

16. • The relative biologic effectiveness (RBE) of
protons is generally considered to be about
1.1 that of X-rays, similar enough to make
tumor and normal-tissue effects with protons
predictable based on X-ray experience.

17. WHAT IS “SOBP” ?

19. A ‘‘spread-out Bragg
peak’’ (SOBP) can be
created by using a
range of proton
energies
Whereas most of the
radiation dose in a patient
with external-beam photons
is deposited outside the
target, most of the radiation
dose with a proton beam
can be placed inside the
target, affording a significant
opportunity to decrease
normal-tissue damage

20. • For clinical use, the beams are spread
longitudinally and laterally and then shaped
appropriately to conform the high dose
regions to the target volume.

22. HOW IS PROTON GENERATED

24. CYCLOTRON

25. passed through an energy
selection system, which
makes the beam's energy
variable for use in each of
the treatment rooms
served by this beam
Electromagnets are positioned
along the line to route the proton
beams around corners and into
each treatment room

29. SYNCHROTRON

30. accelerate batches
(pulses) of protons to the
desired energy
Once a batch has reached
the required energy, it is
extracted and transmitted
via the “beam to the
treatment room
line
Each cycle can produce
protons of a different
energy

34. • Protons are accelerated with cyclotrons or
synchrotrons
• An accelerated proton beam entering the
treatment delivery head is very thin and it is not
suitable for treating three dimensional,
arbitrarily-shaped tumor targets.
• It is broadened longitudinally and laterally and
sculpted to conform to the target shape
• There are two main approaches
1. passively-scattered proton therapy (PSPT)
2. magnetic scanning of narrow “beamlets” of
protons

35. PASSIVE SCATTERING
proton therapy is delivered through a
double-scattered mode in which the
narrow beam of protons is scattered
twice and flattened to produce a
clinically useful beam size and intensity
Field sizes of up to 25
cm in diameter are
achievable with
current double
scattering delivery
modes.

37. A set of focusing magnets is
used to reduce the
diameter of the proton
pencil beam.
Scanning magnets scan the
beam in the lateral
directions
Range-shifter plates are inserted into the
beam path after delivery of the distal-
most layer of proton doses for treating
the second-most distal and subsequently
increasingly more-superficial layers.

38. The dose delivered at each spot or
layer is adjustable, resulting in a
modulated dose distribution at
each spot or layer as well as
between layers, which is known as
intensity-modulated proton
therapy (IMPT).

40. • Potential disadvantages of scanning delivery
modes include
1. a greater demand for accuracy in target
localization
2. reduced speed in treatment delivery increasing
the risk of errors related to intra-fraction organ
motion
3. increased complexity of the dose-delivery
control system and subsequent quality
assurance needs

41. BEAM SHAPING
• Range Modulator
• Aperture
• Range compensator

42. Range modulation

44. Beam aperture
Range
compensator
•conform the dose distribution laterally
•made from blocks of brass
•thickness (2 cm to 8 cm)
•Conforms dose distribution to the
distal shape of the target
•made of a nearly water-
equivalent material such as Lucite

45. • The aperture and compensator for each beam
are designed by the planning system, and the
design information is used to fabricate these
devices using computer-controlled milling
machines.

46. Gantry
• Protons may be delivered from the beam line
to the treatment area via a gantry or a fixed
beam

47. advantages of the gantry system over a
fixed beam
• increase in possible beam angles
• Simpler strategies for patient immobilization
and internal organ motion tracking

48. disadvantage of the
gantry system over a fixed beam
• increase in equipment cost, shielding material,
and space required

49. CLINICAL IMPLICATIONS

50. Choroidal Melanomas and Other Eye
Lesions
• One of the first sites treated with proton
therapy was the eye. Eye treatments could be
provided with relatively low-energy protons
delivered through a fixed beam. Large
numbers of patients have been treated across
the world for choroidal melanomas

52. MEDULLOBLASTOMA

53. Retroperitoneal sarcoma

54. Craniopharyngioma

55. Ependymoma

56. Maxillary sinus carcinomas

57. Lymphomas

58. Prostate cancer

59. • Barriers for the development and proliferation of
proton therapy facilities include
1. the significant cost and complexity of delivery
systems
2. the requirement for more intense physics,
dosimetry, and engineering support in
treatment planning
3. quality assurance
4. equipment operation and maintenance