introduction of Radiotherapy

ZMT 335
128/1/2018 Dr. Nik Noor Ashikin Bt Nik Ab Razak
TOPIC 1
Introduction of Radiotherapy

1.1 Introduction
1.2 Principle of Radiation Therapy
1.3 Types of Radiation Therapy
1.4 External Radiation Therapy Equipment's
& Technique
1.5 Risk & Side Effect

1.1 Introduction

What is Radiotherapy???

Radiation therapy?
Radiotherapy?
Radiation oncology?
1.1 Introduction

1.1 Introduction
8
1
• Radiation therapy (also radiotherapy or
radiation oncology, sometimes abbreviated to
XRT)
2
• Use of ionizing radiation as part of cancer
treatment to control malignant cells (not to be
confused with radiology, the use of radiation in
medical imaging and diagnosis)

1.1 Introduction
9
3
• Radiation therapy works by damaging the DNA
within cancer cells and destroying their ability
to reproduce
4
• When the damaged cancer cells are destroyed
by radiation, the body naturally eliminates them.
Normal cells can be affected by radiation, but they
are able to repair themselves

1.1 Introduction
Radiation therapy is used two different ways:
(depend on tumor type, location, stage and general health of patient)
TO CURE CANCER
(Curative / adjuvant / therapeutic treatment)
-therapy has survival benefit and it
can be curative
-Destroy tumors that have not spread
to other body parts
-Reduce the risk that cancer will return
after surgery or chemotherapy
TO REDUCE SYMPTOMS
(Palliative)
-very advanced tumors
-probability of cure is very small or
negligible
-Alleviate pain by reducing the size of
a tumor

1.1 Introduction
11
5
• Approximately 45 % are cured
• 22% – surgery (independently or in combination)
• 18% – radiation therapy (independently or as a
leading method)
• 5% – chemotherapy (independently or, more
often, it is combined with surgery and radiation
therapy)

1.2 Principle of RT

1. Delivering of an optimal
dose to the tumor
2. Minimal damage of
surrounding organs &
tissues.
RT
GOAL
1.2 Principle of RT

1.2 Principle of RT
14
1
• Radiation therapy uses special equipment to
deliver high doses of radiation to cancerous
tumours, killing or damaging them so they
cannot grow, multiply, or spread
2
• The radiotherapy machine aims specific amounts
of the radiation only to the area of the body that it
is pointed at and nowhere else

1.2 Principle of RT
15
3
• Although some normal cells may be affected by
radiation, most appear to recover fully from the
effects of the treatment
4
• What does ionising radiation do?
• Ionizing radiation deposits energy that injures or
destroys cells by damaging their genetic material
(DNA), making it impossible for these cells to
continue to grow28/1/2018 Dr. Nik Noor Ashikin Bt Nik Ab Razak

1.2 Principle of RT
Type of Radiation
Directly ionising radiation
Charged particles (Electron,
Proton)
Indirectly ionizing radiation
X-rays, Gamma Rays, Neutron
(Eject charged particles which
carryout further ionization)

1.2 Principle of RT
Sources of radiation used in
RT
X – rays
(Low energy)
Conventional X-
ray tube &
Bremsstrahlung
production
Gamma rays
From
Radioactive
Isotopes
(Radioactivity)
High energy
x-rays
Linear
accelerator
(Bremsstrahlung
-production)
High energy
Electrons
Linear
Accelerator
Thermionic
emission and
acceleration.

Types Of Radiation Therapy
1. External beam
radiotherapy
(EBRT/ XBRT) @
teletherapy
- outside the body
2. Brachytherapy @
sealed source
radiotherapy
-sealed radioactive
sources placed precisely
in the area under
treatment
3. Systemic
radioisotope therapy
@ unsealed source
radiotherapy
-infusion or oral
ingestion

1.3.1 External Beam Therapy (EBT)
20
1
• Source of radiation is at a distance from the
patient (about 80 or 100 cm) - External to the
patient
2
• Radiation is focused on to the area of the
lesion

21
3
• Radiation given in multiple daily fractions
4
• Treated for 1- 6 weeks, usually for 5 days a
week

External Beam Radiotherapy
sources of Radiation
Kilo Voltage X – Rays
Superficial therapy :
100 – 150 KVp
Deep X – Ray
therapy : 150 – 400
KVp
Gamma Rays
(Telecurie units)
137Cs Unit (not
popular) : 662 KeV
60 Co Unit :1.25 MeV
(Avg)
High Energy X- Rays &
Electrons
Linear Accelerator
4 – 21 MV

1.3.2 Brachytherapy
23
5
• Brachytherapy uses encapsulated (sealed)
radioactive sources to deliver a high dose to
tissues around the source
6
•Source of radiation (radioactive material ) is either
(kept in the) placed into natural cavities of the body
or implanted in the tissue

1.3.2 Brachytherapy
24
7
• High dose to the tumour tissue and less dose
to other organs
8
• Different sources and techniques available

Methods of application in Brachytherapy
Intracavitary
sources are (kept in) inserted
temporarily into the natural
cavities of the body
eg, Uterus, Oesophagus,
bronchus
Interstitial
sources are implanted in
the tissue
eg, Breast, tongue,
prostate
Mould
Surface applicator with
radioactive sources to
treat skin lesions

Brachytherapy - Methods
Preloading
Applicators are
placed in the
patient with active
sources
Afterloading
Hollow needles,
tubes, catheters
or other
applicators are
inserted
Remote after
loading
Applicators are
kept in patient and
then radioactive
sources are placed
in the applicator
with a remote
control unit.

Will the patient become radioactive?
• Will not become permanently radioactive.
• Patients who are given radioactive substances such as iodine,
phosphorus, or strontium by mouth or into a vein will be instructed
on precautions to take until their bodies no longer contain enough
radioactivity to be hazardous to others.
1.3.2 Brachytherapy

1.4 External Radiation Therapy Equipment's
& Technique

Radiation Therapy Equipment's
1. γ –Rays
(Radioactive Source based)
Tele Cesium
Radium
Bomb
Cobalt-60
-Gamma
Knife
2. X - Rays
Linear
Accelerator
-3DCRT
-SRS/SRT
-IMRT
-IGRT
-Rapid Arc
-SBRT
Tomotherapy
Cyber Knife
3. Particle Beam
-Protons
-Carbon
-Neutrons

1.4.1 γ –Rays

1. Cobalt Unit
1.4.1 γ –Rays

1.4.1 γ –Rays
-Co-60-
RADIOSURGERY
“GAMMA KNIFE”
TECHNIQUE

1.4.2 X –Rays

• X-rays
• Single energy 4 or 6MV X-rays
• Dual energy 6 and 15 or 18 MV (low
and high energy)
• Electrons
• 4 MeV to 21 MeV - variable
Varian Accelerator
Siemens
Accelerator
1.4.2 X –Rays
EQUIPMENT

No more
lead blocks!
1.4.2 X –Rays
EQUIPMENT

1.2 Principle of RT1.4.2 X –Rays
EQUIPMENT

Synchrony™
camera
Linear
accelerator
Manipulator
Image
detectors
X-ray sources
Targeting System
Robotic Delivery System
EQUIPMENT

• High energy beam
• 1 moving source
• 5mm – 4cm target
1.4.2 X –Rays
1. RADIOSURGERY
“X KNIFE”
TECHNIQUE

1.4.2 X –Rays
2. IMRT
TECHNIQUE

1.5 Risk & Side Effect

1.5.1 Risk
50
1
• Radiotherapy can damage or destroy normal cells as well
as destroying cancer cells and cause treatment side
effects
2
• There may be a small risk of long term, or late,
permanent effects from radiotherapy

1.5.2 Side effects
51
3
• Usually temporary side effects
4
• The extent of the possible side effects depends on
general health, treatment dose, and the area of body that
is being treated

1.5.2 Side effects
52
5
• The most common side effect is fatigue
6
• Specific side effects within the area being treated may
include reddening and itching of the skin

Meet the Radiation Oncology Team

• Radiation Oncologist
• The doctor who oversees the radiation therapy
treatments.
• Medical Radiation Physicist
• Ensures that complex treatment plans are properly
tailored for each patient.
• Dosimetrist
• Works with the radiation oncologist and medical
physicist to calculate the proper dose of radiation given
to the tumor.
• Radiation Therapist
• Administers the daily radiation under the doctor’s
prescription and supervision.
• Radiation Oncology Nurse
• Cares for the patient and family by providing
education, emotional support and tips for managing
side effects.

• 1. ENERGY
• 2. ACTIVITY
• 3. EXPOSURE
• 4. KERMA
• 5. DOSE
• 6. ABSORBED DOSE
• 7. EQUIVALENT DOSE
• 8. EFFECTIVE DOSE
1.6 Radiation measurement

1.ENERGY
•Basic unit for energy = joule (J)
•In radiation field, the units is too big. Smaller units is used;
electron-Volt (eV).
•1 eV = energy needed to transfer 1 electron using 1 volt.
•1 eV = 1.062 x 10-19 joule
•1 joule = 0.624 x 1019 eV

2. ACTIVITY
• ACTIVITY (A) = Number of decays(nucleus transformation –
dN) per second (dt), measured in BEQUERELS (Bq).
• A = dN/dt
• 1 Bequerel = 1 decay per second
• An older unit (non SI) is the CURIE ( Ci )
1 Ci = 3.7 x 1010 Bq = 37 GBq

3. EXPOSURE
•Exposure is symbolized by X, is absolute value of total charge, dQ
of the ions of one sign produced in air when all the electrons
liberated by photons in air of mass dm are completely stop in air.
•X = dQ/dm
• Coulomb per kilogram (C/kg)
• 1R = 2.58 × 10−4 coulomb/kg air
•The average energy required to produce ion pairs in a material, is
33.85 eV per ion pair (IP) for air. Thus, for every coulomb per
kilogram of exposure, air absorbs 33.85 J/kg of energy

RADIATION EXPOSURE
Primary ion pairs
Produced as ionizing
radiation.
Interacts with atoms of an
attenuating medium
Eg: electrons and positive ions
Secondary ion pairs
Produced as primary ion
pairs Dissipate (dissapear)
their energy by ionizing
nearby atoms
59

60
LIMITATION OF
EXPOSURE
Defined only for
photons (x-rays &
gamma rays)
Not defined
for energies
> 3 MeV
E ≥ 3 MeV,
Difficult to determine how many
secondary ion pairs are produced
outside of the measurement
volume
Must
occur in
air

FLUENCE
The fluence,  , is the quotient of dN by da, where dN is the number
of particles incident on a sphere of cross section dA, thus
 = dN/dA
The unit of fluence is m-2

4. KERMA
• The quantity kerma, K, is defined as:
K=dEtr/dm
where dEtr is the sum of the initial kinetic energies of all charged ionizing
particles liberated by uncharged ionizing particles in a material of mass
dm.
Kerma in air, Ka, is used for radiation protection measurement purposes.
The SI unit of kerma is the joule per kilogram (J/kg), termed gray (Gy).

5. DOSE
• Used to visualized total radiation effects received by a material
(biological or non-biological).
• Relates with the total amount of energy transferred.
• A few units available:
• Absorbed dose (D)
• Equivalent dose (H)
• Effective equivalent dose, etc.

6. ABSORBED DOSE
• Absorbed dose is defined as the energy imparted by ionising radiation to
matter of mass m in a finite volume V.
• ABSORBED DOSE is measured in the SI unit of the gray (Gy) 1 gray =1
Joule / kg
An older unit (non SI) is the rad.
100 rad = 1 gray ( Gy)
1 rad = 10 mGy

7. EQUIVALENT DOSE
• Gives an approximate biological effect for certain amount of irradiation dose.
• Different radiations have different biological effectiveness for the same amount
of energy absorbed. To allow for this, each radiation type is given a radiation
weighting factor, WR, (sometimes called a quality factor, Q).
• H = D x Q x N
• D = Absorbed dose; Q = Quality factor
• N = Multiply factor, considering other factors such as geometrical. Normally
assumed = 1.

•Tissue EQUIVALENT DOSE (HT,R) = AVERAGE Absorbed dose
for TISSUE (DT,R) x Radiation weighting factor (WR ).
•(HT,R) = (DT,R) x (WR )
•Equivalent dose is measured in the SI unit of sievert ( Sv).
An older unit (non SI) is the rem
100 rem = 1 sievert (Sv)
1 rem = 10 mSv .

radiation weighting factor
Radiation type WR
--------------------------------------
X –rays 1
gammas 1
betas 1
alphas 20
fast neutrons 10
protons 5

8. EFFECTIVE DOSE
A summation of the tissue equivalent doses, each multiplied
by the appropriate tissue weighting factor:
E = ∑wT·HT
where HT is the equivalent dose in tissue T and wT is the
tissue weighting factor for tissue T.

Tissue weighting factors
• Multipliers of the equivalent dose to an organ or tissue
to account for the different sensitivities to the induction
of stochastic effects of radiation.

Pre-TASK 1
Direct Action & Indirect Action of radiation
on DNA
Watch the videos in e-learn and answer the quiz
http://ozradonc.wikidot.com/rb:radiobiology-introduction
https://www.youtube.com/watch?v=tq6FDyFeCN0

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