1. RADIATION THERAPY
BY
MR. SEMBIAN.N
ASSOCIATE PROFESSOR
MAHARISHI MARKANDESHWARCOLLEGEOF NURSING
MULLANA

2. Introduction
 The decision to use radiation therapy (RT) in cancer
treatment depends on many factors such as the:
 Type of cancer:
 Some cancers such as lymphoma are very sensitive to RT
and some are resistant to treatment e.g. melanoma
 Efficacy of other modalities
 Chemotherapy and (or) surgery may be sufficient alone
 Patient’s general health
 Local and distant extent of disease

3.  Similar considerations apply to surgical resection and
chemotherapy.
 All of these modalities may be used together or alone.
 Tumor management decisions require MULTIDISCIPLINARY
APPROACH.
 Each patient should be individually assessed by a team of
specialists.
 For many pediatric cancers chemotherapy may be sufficient
alone. However, RT (with or without surgery) may be an
important part of local control (ensure that the tumor does not
come back where it started).

4.  There are two main categories of radiation
treatments:
 Radical: Attempt to cure disease
 Palliative: To relieve symptoms - not expected to
cure disease

5. Radiation Therapy (RT)
 Radiation therapy = High energy X-rays, aimed
at a tumor to kill the cancer cells within it. These
X-rays have to be directed at the tumor with
accuracy - so that the cancer gets hit and normal
surrounding tissues are secure.
 In simple terms high energy X-rays work by
damaging the cell nucleus and stopping the cell
from dividing. Ionizing events damage the
chromosomes.

6.  The fundamental unit used to describe the interaction
of radiation with matter is the amount of energy
absorbed per unit mass. This is called the absorbed
dose and is measured in rads or Gray.
 100 rads = 1 Gray
 1 rad = 1 cGy = one hundredth of a Gray
 Different energy ranges of X-rays are used. There are:
 Superficial, (low energies)
 Megavoltage, (high energies)

7. Radiotherapy physics
 Working in radiotherapy physics, you would be
responsible for the precision and accuracy of
treatments by using advanced computer
calculations to develop individual patient
treatment plans.
 Planning starts with image of the cancer to be
treated usually taken on a CT or MRI scanner,
outlining the target volume and then planning
the treatment beams to be used to treat the
tumor, making sure the radiation dose to
surrounding tissue is minimized.

8.  ensuring that equipment used in
radiotherapy is calibrated accurately and
used safely and ensuring the imaging
equipment used during treatment allows the
Radiotherapy team to update the treatment
plan during a course of treatment.

9. Biological basis of
radiation therapy
1. Cells can be “killed” by ionizing radiation.
2. Most important target appears to be nuclear
DNA.
3. Radiation damage to DNA results in non-viable
offspring.
4. Rapidly dividing cell populations are the most
sensitive to ionizing radiation (e.g. tumors,
epithelial cells, hemopoietic cells

10. The physical goal of
radiation therapy
physics perspective the goal of
 radiation therapy could be simply stated as
“Deliver a high dose to all parts of the tumor
while minimizing the dose to surrounding
normal tissue.”

11. Types of ionizing radiation
 Alpha, beta and gamma Radioactive atoms
give out ionising radiations.
 However, it turns out that there are three
distinct types of radiation, each with very
different properties.
 These radiations alpha (a), beta (b) and
gamma (g).
 Alpha and beta radiations are streams of
particles, whereas gamma radiation is part of
the electromagnetic spectrum.

14.  Ionising alpha
 Alpha particles are the same as the nuclei of helium.
This means that they have a (relatively) large mass..
Alpha particles don’t travel very fast – because they
have such a large mass.This means that they tend
to run into with plenty of other atoms.

15.  Therefore, they cause a lot of ionisation by
pulling electrons off the atoms. All these
collisions mean that they lose energy quickly, so
they have a short range in air and they are easily
stopped by anything solid – even a piece of
paper will stop alpha radiation.

16. Fast beta
 Beta radiation is a stream of fast moving electrons.These
particles have very little mass (about 7000 times lighter than an
alpha particle) and travel close to the speed of light (300,000
km/s).They tend to pass through the air and solid matter without
many collisions with other atoms. So beta radiation is only
weakly ionising. However, it means that it has a long range in air
and will pass through paper, and thin sheets of aluminium and
steel. However, it is stopped by lead or thick pieces of other
metals.

17. Penetrating gamma
 Gamma radiation is at the high frequency end
of the electromagnetic spectrum. It has a very
short wavelength (much less than the radius of
an atom) and will pass through atoms with very
little chance of being deflected or absorbed. It
has an extremely long range in air and will get
through thin samples of most materials without
any noticeable decrease in intensity. However,
its intensity is reduced by lead or very thick
pieces of other metals.The thicker the sample,
the greater the reduction in intensity

18.  Ionizing radiation
 Radioactive substances give out radiation all of the
time.
 Radiation can be harmful, but it can also be useful -
the uses of radiation include to:
 detect smoke
 gauge the thickness of paper
 treat cancer
 sterilize medical equipment.

19.  Radiation can be absorbed by substances in its
path. For example, alpha radiation travels only a
few centimetres in air, beta radiation travels tens of
centimetres in air, while gamma radiation travels
many metres. All types of radiation become less
intense the further the distance from the
radioactive material, as the particles or rays
become more spread out.

20. Mechanism of action
 Radiation therapy works by damaging the DNA of
cancerous cells.This DNA damage is caused by energy
changes, photon or charged particle.This damage is
either direct or indirect ionization of the atoms which
make up the DNA chain. Indirect ionization happens as
a result of the ionization of water, forming free
radicals, notably hydroxyl radicals, which then damage
the DNA.

21.  In photon therapy, most of the radiation effect is
through free radicals.
 Cells have mechanisms for repairing single-strand
DNA damage and double-stranded DNA damage.
 However, double-stranded DNA breaks are much
more difficult to repair, and can lead to dramatic
chromosmal abnormalities and genetic deletions.
Targeting double-stranded breaks increases the
probability that cells will undergo cell death

22.  Cancer cells are generally less differentiated and
more stem cell-like; they reproduce more than
most healthy differentiated cells, and have a
diminished ability to repair sub-lethal damage.
 Single-strand DNA damage is then passed on
through cell division; damage to the cancer
cells' DNA accumulates, causing them to die or
reproduce more slowly

23.  One of the major limitations of photon radiation
therapy is that the cells of solid tumors become
deficient in oxygen. Solid tumors can outgrow
their blood supply, causing a low-oxygen state
known as hypoxia.
 Oxygen is a potent radiosensitizer increasing the
effectiveness of a given dose of radiation by
forming DNA-damaging free radicals.
 Tumor cells in a hypoxic environment may be as
much as 2 to 3 times more resistant to radiation
damage than those in a normal oxygen
environment.

24.  Much research has been devoted to overcoming
hypoxia including the use of high pressure oxygen
tanks, hyperthermia therapy (heat therapy which
dilates blood vessels to the tumor site), blood
substitutes that carry increased oxygen, hypoxic cell
radiosensitizer drugs such as misonidazole

25. Superficial RT
 Also called "orthovoltage"
 Generated by X-ray tube.
 Most of the energy is deposited at the skin surface - so
still sometimes used to treat skin cancers.
 When RT first started in the early 1900s, all treatment
was given using superficial radiation. Huge amounts of
radiation had to be given to the skin surface in order to
treat at a depth.
 The dose of radiation used to be measured in "skin
erythema units" - the more radiation that was given,
the redder the skin became - not very accurate!
 Now many radiotherapy departments do not use this
type of RT at all.

26. Megavoltage RT
 Much more energetic and penetrating
 Used for treatment of deep seated tumors
 The maximum dose of radiation is deposited
below the skin surface (how far below
depends on the energy of the radiation used).
 Megavoltage RT is generated mainly by 2
means:-

27. linear accelerator (LINAC)
 is the device most commonly used for external
beam radiation treatments for patients with cancer.
 used to treat all parts/organs of the body-
 delivers high-energy x-rays to the region of the
patient's tumor.
 The LINAC is used to treat all body sites, using
conventional techniques
 These photos show the machine most commonly
used to deliver external beam radiotherapy
treatment.

28.  All linacs generate high energy x-rays (photons)
which are then carefully aimed at the area the
Consultant Oncologist wishes to treat.
 They can be used to treat all areas of the body
from head to toe.
 Intensity-Modulated RadiationTherapy(IMRT)
 ImageGuided RadiationTherapy
(IGRT)
 Stereotactic Radiosurgery
(SRS)
 Stereotactic Body RadioTherapy
(SBRT)

29. IMRT
 More advanced linacs have the capability to deliver
another type of treatment, that is used to treat
areas that are on, or close to the skin's surface.This
treatment uses electrons instead of high energy x-
rays (photons)
 The newest linacs also have a capability to treat
using Intensity modulated radiation
therapy (IMRT).These linacs have Multi leaf
collimators (MLC's) that are used to alter the shape
of the beam. Without these, the machine can only
treat square or rectangular shapes (treatment
fields) without having to attach blocks of lead to the
machine

30.  All linacs have some method that radiographers can
use to ensure they are treating in the correct place.
 Most modern machines take a digital image using
the bottom arm.This image is called an EPI (
Electronic portal image) or PI (portal image).These
images are checked against those generated during
your radiotherapy planning, by the radiographers,
before they deliver any treatment (verification). The
number and frequency of images that are taken
depends on each department's imaging protocols.

31.  IMRT also allows higher radiation doses to be
given, to the patient, with fewer side effects
caused.
This technique is normally of most benefit for
patients who are having their pelvis
(prostate or gynecological cancers) or head and
neck treated.
 IMRT is not suitable for all treatment areas, but
therapist would recommend, during initial
consultation ,clinical oncologist whether it would
be suitable for you.

32. image guided radiotherapy(IGRT).
 Some radiotherapy treatment machines also
have an 'On Board Imager' (OBI) It consists of a x-
ray unit (arm to the left of the linac) and a detector
(arm to the right of the linac).

33.  This system gives higher quality verification images
and allows for another radiotherapy technique
called image guided radiotherapy(IGRT).
 IGRT aims to further increase the accuracy of
radiotherapy treatment, by accounting for daily
changes, such as that of organ motion which in turn
helps to reduce some of the associated treatment
side effects.

34.  Some tumors are not in a fixed position within the
body
 exact location can change slightly from day to
day. IGRT involves determining the position of the
tumor everyday before giving any radiotherapy
treatment and then altering the settings /
treatment positioning if the tumour has moved.

35. Radiotherapy planning
 Radiotherapy planning is the process that
occurs in between patient planning CT scan date
and patient radiotherapy treatment start date.
 it is all done on computers with the information
the therapy radiographers obtained when you
had your planning CT scan.
 there is a delay between your CT scan date and
your radiotherapy treatment start date.

36.  After taking radiotherapy planning CT scan, the 3D
data is sent to the planning department. clinical
oncologist will then outline the area (volume) they
wish to treat and also outline areas they wish to
avoid with the radiation.
 It is then the therapy radiographers’ or physicists’
job to produce a method (radiotherapy plan) to
treat the area the clinical oncologist wants, whilst
avoiding the areas s/he wishes to avoid.
 The finished plan has iso-dose curves to show
which areas are receiving what dose (amount) of
radiation.They are very similar to traditional
weather maps to show the low and high pressure
systems.

37.  Area the clinical oncologist wishes to treat is
outlined in red dotted marks .
 The other lines represent the dose of radiation the
patient will receive .
 The yellow line represents 100% of the dose and the
dark green line represents 98% of the dose.
 The right kidney (outlined in purple on the left of the
image) receives no dose.


39.  To enable the clinical oncologist to accurately outline
the area they wish to treat, they might use a
combination of the data from the radiotherapy CT
planning scan and an MRI scan.
 This is often the case with brain tumours and is
called MRI fusion.
 In this image the clinical oncologist is using both MRI
(inner circle) and CT data to outline the tumours in this
patient's brain.
 With some brain tumours the clinical oncologist wants
to treat the area where the tumour was located before
it was taken out (de-bulked) by the surgeon.
 MRI Fusion allows the pre-operative MRI scan to be
overlaid with the post-operative CT planning scan.

41.  Intensity-Modulated Radiation
Therapy(IMRT) planning allows the clinical
oncologist to shape how the radiation dose will be
in the patient.
 If you look at the top image, on this page, again you
can see they have outlined the spinal cord. (maroon
line).
 The computer planners have made an excellent plan
to avoid treating the spinal cord, but have had to
come very close to it.

43.  In the IMRT plan , they have managed to curve
the radiation dose perfectly around the spinal
cord and even avoid treating the patient's
vertebra (Purple line).
 As we said in the IMRT section, IMRT is not
suitable for all radiotherapy treatments or
patients
 but as you can clearly see, when it is suitable a
superior plan can be created for the patient.

44. radiation therapy Lasers
 Lasers are used
in radiotherapy ( radiati
on therapy ) treatment
to ensure the patient is in
the correct position for
treatment.They are
mounted on the walls
and the ceiling.

45. Electrons
 More
advanced linacs have the
capability to deliver
another type or
radiotherapy
treatment that is used to
treat areas that are on,
or close to the skin’s
surface.This treatment
uses electrons instead
of high energy x-
rays (photons).

46.  To treat with electrons the radiographers will
attach an electron applicator to the head of the
treatment machine.They then have to place an
insert into the end of this applicator that is
specific to the exact shape and size required for
each patient's treatment

47. Multi-Leaf Collimators
 Many radiotherapy
treatment
machines have built
in Multi leaf
collimators (MLC's)
 Multi leaf
collimators are used
to alter the shape of
the beam.

48.  Without these, the linac can only treat square or
rectangular shapes (treatment fields) without
having to attach blocks of lead onto the
machine, to shield out the radiation where it is
not required.
 MLC leaves range from 0.4mm - 1cm wide
(depending on the linacs brand and type) and
each leaf can be moved individually to match
each patients specific radiotherapy treatment
plan.This photo shows the head of the gantry -
the irregular shape in the middle is created by
the MLC's.

49. SBRT
 involves the delivery of a single high dose
radiation treatment or a few fractionated
radiation treatments (usually up to 5
treatments). A high potent biological dose of
radiation is delivered to the tumor, improving
the cure rates for the tumor, in a manner
previously not achievable by standard
conventional radiation
therapy

50.  specialized form of radiation
involves the use of multiple
radiation beam angles, expert
Radiation Oncologists
specialized in this technique are
able to safely deliver high doses
of radiation, with very sharp
dose gradient outside the
tumor and into the surrounding
normal tissue

51. How SBRT Differs from
Conventional Therapy
 With conventional therapy, radiation is delivered in
relatively small doses over the course of several
weeks, with patients receiving daily treatments
during that time.
 With SBRT, physicians are able to deliver a greater
combined dose of radiation over the course of far
fewer treatments. SBRT has shown dramatically
better outcomes than conventional radiation therapy.

52.  Whereas two-year success rates for conventional
treatment range from 30 to 40 percent, the success
rates for SBRT range from 80 to 90 percent —
comparable to those of resection surgery but with
far fewer risks.
 Despite the fact that SBRT delivers higher
biological dosage of radiation, patients have
experienced fewer side effects, including radiation
pneumonia. Slight fatigue for one week following
treatment is SBRT’s most common side effect.

53. How SBRT Works
 Planning begins with diagnostic imaging to help
locate the tumor and determine the area that will
be treated.This includes four-dimensional
imaging that maps the target area as it moves
over time with the patient’s breathing cycle. In the
only invasive part of the treatment, gold seeds,
called fiducials, are sometimes implanted into the
tumor before images are taken. Because the
fiducials are visible in planning scans and at the
time of treatment, physicians use them to ensure
that the high-dose envelope of radiation is
accurately overlying the tumor.

54.  Radiation oncologists work with medical
physicists to develop a radiation plan that
ensures safe exposure to normal structures.
Each of the treatment sessions takes 30 to 60
minutes and, unlike with more invasive
therapies, the patient leaves each treatment
free of significant pain or side effects.
Treatments do not have to be administered on
consecutive days, but the entire course of
therapy is usually concluded within 10 days.

55.  Good response - Lung cancer candidates for
SBRT are patients with small tumors —
 localized tumors (up to 6-7 cm), or a few
tumors
 poor response = Patients whose tumors are
located centrally or close to airways or the
heart - centimeters or less

56. Cobalt Source
 The Cobalt-60 source is contained inside a
cylindrical stainless-steel capsule and sealed by
welding.
 20 mm diameter cobat-60 source will be used for
treatment.
 The machine has capacity to load 200
RMM(Rontgen per Minute at 1 Meter) source.
 Cobalt sources are the cheapest in the world and
are effectively being used in most of the
teletherapy units in India.

57.  Linear accelerators (LINAC) use high energy
electrons or high-energy X-rays for treatment of
deep-seated tumors. High energy γ-emitting
radioisotopes, such as Cobalt-60, Cesium-137 and
Europium-152 are also used for cancer treatment.
 Among various radioisotopes, Cobalt-60 is the
most widely used in teletherapy machines,
considering the energy of emitted photons,
halflife, specific activity, and means of production.
Cobalt-60 has a half-life of 5.3 years and emits high
energy (1.17 and 1.33 MeV) γ-rays.

58.  Sources of very high specific activity (~ 250
curie/gm) and high source strength (~10 kilo curie)
are used in teletherapy machine..
 Although linear accelerators offer superior beam
characteristics and faster treatments, these units
are expensive and complex. In developing countries
like India, Cobalt-60 machines are more suitable
than LINAC, considering the cost and maintenance
issues. More than 50% of all human cancers are
amenable to Cobalt-60 teletherapy

59.  Source Head :It is a shielded container that
houses the radioactive source. Uranium is the
major shielding material used in the machine,
because of its high density and high mass
number.
 The machine has source-to-skin distance of 80
cm, which is an important parameter of the
machine. It is achieved by the compact design of
source head and collimator.

60.  Gantry : Gantry is the part of the unit that
holds the source head and counter weights. It
can rotate around the patient about a
horizontal axis by ±180°.The gantry is
mounted on the base housing.

61.  Patient Support System or Couch :The unit has
a sophisticated Patient Support System on
which the patient has to lie down during
treatment. It consists of a turntable mounted
eccentrically with the isocenter to support
another system of tables providing required
motions for positioning the tumour site at the
isocenter.All the motions are motorised and the
couch is under fully computerised control.The
indexed patient positioning system enables
quick, accurate and reproducible patient
positioning.

62.  Controller :The controller is fully computerised
and the interaction between the operator and
the unit is achieved through a computer
monitor, keyboard and mouse. Data on every
treatment are registered on the computer's
hard disk and may be retrieved for control
purposes. Separate unit mounted control
panels are provided on both the sides of the
couch.The necessary interlocks and corrective
actions for radiation safety are also provided by
the control system

65. Radiobiology
 Radiobiology is the study of how radiation therapy
interacts with cancer cells and normal cells.
 Radiotherapy damages the DNA causing double
strand breaks which are un-repaired or mis-
repaired.This leads to cell death.
 Some tumors are very sensitive to radiation
treatment, or radiosensitive - for example
lymphomas and seminomas..

66.  Some tumors are quite insensitive, or radio
resistant - for example melanoma.
 Lack of Oxygen (hypoxia) in the center of tumors
leads to radio resistance.
 Chemotherapy acts as a radiation sensitizer
(makes the RT more effective) and can also make
side effects from radiation more severe.
 All cancer cells vary in sensitivity depending on
their position in the cell cycle.
 Waiting at least 6 hours between radiotherapy
treatments gives normal tissue the chance to
repair and this is why radiation therapy is split up
into small amounts or "fractions."

67.  Repair
 Repair is the one of the primary reasons to
fractionate radiotherapy. As discussed in DNA
Damage and Repair, there are three types of
damage that ionising radiation can cause to
cells:
 Lethal Damage, damage which is fatal to the cell
 Sublethal Damage, damage which can be repaired
before the next fraction of radiation is delivered

68.  Potentially Lethal Damage, damage which can be
repaired under certain circumstances (usually when the
cell is paused in the cell cycle due to external factors)
 By splitting radiation dose into small parts, cells are
allowed to repair sublethal damage.
 Malignant cells have often suppressed - preventing
them from undergoing efficient repair.
 Normal tissue cells with intact repair pathways are
able to repair the sublethal damage by the time the
next fraction is delivered

69. Redistribution
 When radiotherapy is given to a population of cells,
they may be in different parts of the cell cycle.Cells
in S-phase are typically radioresistant, whereas
those in late G2 and M phase are relatively sensitive.
A small dose of radiation delivered over a short time
period (external beam or high dose brachytherapy)
will kill a lot of the sensitive cells and less of the
resistant cells. Over time, the surviving cells will
continue to cycle. If a second dose of radiation is
delivered some time later, some of these cells will
have left the resistant phase and be in a more
sensitive phase, allowing them to be killed more
easily.

70.  Reoxygenation
 Tumours may be acutely or chronically hypoxic.This
oxygenation status may change during treatment.
 Acute Hypoxia
 Acute hypoxia is due to transient closure of
capillaries or arterioles servicing parts of the tumour.
While this vessel is closed, the tumour cells become
hypoxic and resistant to the indirect action of
radiation.These vessels are usually only closed for
short times but may occur during a fractionated dose
of radiation. Splitting the dose into fractions raises
the possibility of the closed vessel being open the
next time around, and therefore allowing the tumour
cells to be killed.

71.  Chronic Hypoxia
 Chronic hypoxia is due to the poor vasculature of
tumours and the distance oxygen must travel to
reach cells that are far from the capillaries.These
chronically hypoxic cells are also resistant to
radiation. Fractionated radiotherapy kills cells that
lie close to the capillary more effectively.As these
cells are removed, the chronically hypoxic cells are
able to move closer to their nutrient source, and
therefore become relatively oxic. Oxic cells can be
killed.

72.  Repopulation
 Repopulation is the last of the classical 4 R's. Repopulation is the increase in cell
division that is seen in normal and malignant cells at some point after radiation is
delivered.
 Repopulation of normal tissues
 Repopulation occurs in different speeds depending on the tissue. In general,
early responding tissues begin repopulation at about 4 weeks. By increasing
treatment time over this amount, it is possible to reduce early toxicity in that
tissue. Late responding tissues only begin repopulation after a conventional
course of radiation has been completed, and therefore repopulation has minimal
effect on these effects (the repair 'R' is more important for late tissues).
 Repopulation of malignant tissues
 Some tumours exhibit accelerated repopulation, a marked increase in their
growth fraction and doubling time, at 4 - 5 weeks.This is seen most notably in
squamous cell carcinoma of the head and neck as well as the cervix. Accelerated
repopulation is a dangerous phenomenon that must be countered if treatment
time extends over five weeks. Methods to do this include accelerated treatment
with hyperfractionation to minimise late effects.

73.  Radiosensitivity
 Radiosensitivity is a newer member of the R's. It
reminds us, that apart from repair pathways,
redistribution of cells, reoxygenation of
malignant cells and repopulation there is an
intrinsic radiosensitivity or radioresistance in
different cell types. Radiosensitive cells include
haemotological cells, epithelial stem cells,
gametes and tumour cells from haemotological
or sex organ origin. Radioresistant cells include
myocytes, neurons and tumour cells such as
melanoma or sarcoma.

74. Immobilization
 Radiotherapy planning can be quite simple or
very complex depending on:
 The aim of treatment (palliative v curative)
 Tumor location
 How much radiation is required to kill that
particular type of cancer
 When high dose radiotherapy is given, it is
really important that the patient is absolutely
still during treatment and that the treatment
"set up" is reproducible from day to day.

75. • most crucial parts of radiation therapy
treatment.
• For accurate delivery of a prescribed radiation
dose to a target volume,while sparing
sourrounding normal and critical tissues.
• Without proper immobilization,the patient is
at risk for improper treatment and unwanted
side effects
• Immobilization such as molds,
casts,headrests,and other devices are
constructed to reduce setup error and patient
movement during treatment.

76.  can reduce the time for daily patient set
up.
 A well constructed immobilizing system
can reduce the time for daily patient set
up

77. Desirable characteristics
of immobilization devices
• Ease of use.
• Ease of making the device.
• Comfort for the patient.
• Minimal space requirement for storage.
• Resistance to bending and streching.
• Minimal perturbation of the beam so as not to
produce artefacts in image acquisition.

78. Immobilization Devices
 Planning usually starts with a visit to the mould
room.
 Here a mask or other immobilization device is made
for the patient to wear during treatment. The mask
is made with a plastic that becomes soft with heat
and then sets when it cools. Thus an impression of a
part of the body can be made.
 This mask is used for:
 1. Patient immobilization - for precise, reproducible
treatment, patients should not be able to move.
 2. So that reference marks (to show where the
radiation should go) need not be on the patient's
skin, but can be placed on the mask instead.

79. HEAD,NECK AND BRAIN
IMMOBILIZATION

81. Brain tumors
 1)GTC frame for fractionated therapy
2)BRW system for single fraction
radiosurgery.

82. THORAX AND BREAST
IMMOBILIZATION
VACLOK:
• placed around the
patients upper body.
• The air is then vaccumed
out of the bag for a
custom fit and sealed in
order to retain its shape.
• vacloks are
radiotranslucent ,almost
air equivalent. they are
washable and reusable.

83. • 2)BREAST BOARD: is used
specifically for the treatment
of breast cancer.
• It has several adjustable
features to allow for the
manipulation of patients
arms,wrists,head and
shoulders.
• Breast boards are generally
constructed of carbon
fiber,allowing the device to be
lightweight and durable.

84. PELVIC IMMOBILIZATION
 Immobilization
systems such as
vacloks, belly
boards,and the hip-
fix(using
aquaplast) system
are commonly used
during treatments
of pelvic region

85. IMPROVED IMMOBILIZATION
TECHNIQUES
SMALLER TREATMENT
VOLUME
HIGHER CONTROLLED
DOSES
HIGHLY PRECISED
TREATMENT
HIGHER CURE
RATE

86. Immobilizatio
n Device
Function Preparation
of Device
Special
characteristic
s
Bite block Stabilize jaw
to ensure
same mouth
position each
time
Dental
impressions
are taken
Fixed to a
calibrated
arm, which is
attached to
the
treatment
couch
Only used if
child will bite
down firmly
on the piece

87. Thermal
plastics
Used for head
placement
Plastic sheets
make masks
to fit contours
of patient
head and face
Causes slight
increase in
radiation
surface
dosage
Vacuum-
molded
thermoplastic
s
Can be used
to stabilize a
variety of
different body
parts
Vacuum
draws plastic
tightly over
cast, plastic
mold may be
fitted to the
body part and
fastened to
the treatment
couch
Good visibility
(clear)
Can draw
directly on it

88. Polyurethane
foams
Used for a
variety of body
parts
Place body part
on a polystyrene
bag that is filled
with chemicals,
chemicals
generate
expanding
polyurethane
foam
Expensive
Requires skill to
be done properly
Fumes are
produced
Vacuum bags Conforming bag
that can be
reused for
several patients
Patient lies on
bag in treatment
position
Air is evacuated
from the bag
Bag conforms to
body
Can be adjusted
after forming
and reused for
several patients
Require
increased surface
dosage

89. Radiosurgery
 In stereotactic radiosurgery (SRS), the
word stereotactic refers to a three-dimensional
coordinate system that enables accurate correlation
of a virtual target seen in the patient's diagnostic
images with the actual target position in the patient
anatomy
 Radiosurgery is performed by a multidisciplinary
team of radiation oncologists, and
medical physicists to operate and maintain highly
sophisticated, highly precise and complex
instruments
 medical images that are obtained via computed
tomography, magnetic resonance, and angiography

90.  General indications for radiosurgery include
many kinds of brain tumors, such as acoustic
neuromas, germinomas, meningiomas,metast
ases, trigeminal neuralgia, arteriovenous
malformations and skull base tumors, among
others.
 Expansion of stereotactic radiotherapy to
extracranial lesions is increasing, and includes
metastases, liver cancer, lung cancer,
pancreatic cancer, etc

91. Gamma Knife
 The Gamma Knife is used to treat brain tumors by
administering high-intensity cobalt radiation
therapy in a manner that concentrates the
radiation over a small volume.
 The device aims gamma radiation through a
target point in the patient's brain.The patient
wears a specialized helmet that is surgically fixed
to the skull, so that the brain tumor remains
stationary at the target point of the gamma rays.
 An ablative dose of radiation is thereby sent
through the tumor in one treatment session,
while surrounding brain tissues are relatively
spared.

93.  Gamma Knife therapy- Each individual beam is of
relatively low intensity, so the radiation has little
effect on intervening brain tissue and is
concentrated only at the tumor itself.
 Gamma Knife radiosurgery has proven effective for
patients with benign or malignant brain tumors up
to 4 centimeters in size, vascular malformations
such as an arteriovenous malformation (AVM), pain .
 For treatment of trigeminal neuralgia, the
procedure may be used repeatedly on patients.
 the mid- and long-term risks and adverse
effects of ionizing radiation on human tissue

94.  Conformal proton beam radiation therapy
 proton beam radiation may be able to deliver
more radiation to the tumor while reducing side
effects on normal tissues.
 Protons can only be put out by a special
machine called a cyclotron or synchrotron.
 This machine costs millions of dollars and
requires expert staff.
 This is why proton beam therapy costs a lot and
is only in a small number of radiation treatment
centers.

95. Proton beam therapy
 Protons may also be used in radiosurgery in a procedure
called Proton BeamTherapy (PBT) or simply proton therapy
 Protons are produced by a medical synchrotron or cyclotron,
extracting them from proton donor materials and accelerating
them in successive travels through a circular, evacuated conduit
or cavity, using powerful magnets, until they reach sufficient
energy (usually about 200 MeV) to enable them to approximately
traverse a human body, then stop.
 They are then released toward the irradiation target which is
region in the patient's body.
 In some machines, which deliver only a certain energy of protons,
a custom mask made of plastic will be interposed between the
initial beam and the patient, in order to adjust the beam energy
for a proper amount of penetration.
 Because of the Bragg Peak effect( the energy loss of ionizing
radiation during its travel through matter) , proton therapy has
advantages over other forms of radiation, since most of the
proton's energy is deposited within a limited distance

96.  so tissue beyond this range (and to some extent
also tissue inside this range) is spared from the
effects of radiation.This property of protons,
which has been called the "depth charge effect"
allows for conformal dose distributions to be
created around even very irregularly shaped
targets, and for higher doses to targets
surrounded or backstopped by radiation-
sensitive structures such as the optic chiasm or
brainstem. In recent years, however, "intensity
modulated" techniques have allowed for similar
conformities to be attained using linear
accelerator radiosurgery.

97. Intra operative radiation
therapy (IORT)
 is external radiation given directly to the tumor or
tumors during surgery. It may be used if the tumors
can’t be removed completely or if there’s a high risk
the cancer will come back in the same area.The
surgeon finds the cancer while the patient is
under anesthesia ([an-es-THEE-zhuh] drugs are used
to make the patient sleep and not feel pain). Normal
tissues are moved out of the way and protected with
special shields, so IORT lets the doctor give one large
dose of radiation to the cancer and limit the effects
on nearby tissues. IORT is usually given in a special
operating room that has radiation-shielding walls.