Linear accelerators (LINACs) are commonly used for external beam radiation therapy. [LINACs] use microwave technology to accelerate electrons which are then directed at a metal target to produce high-energy x-rays. Key LINAC components include an electron gun, accelerator structure in the gantry, and a treatment head housing components like collimators and flattening filters to shape the beam. LINACs have advanced over generations from early isocentric units to today's computer-driven systems that provide wide ranges of energy and precision treatment capabilities like IMRT.

1. LINEAR ACCELATOR
(LINAC)
PRESENTED BY: ROFIDA ZEIN ELABDIN

2. OUTLINES
►Introduction(Definition ) .
► History .
►Components .

3. INTRODUCTION
What is Linear Accelerator ?
The term linear accelerator means, charged particles
travel in straight lines as they gain from an alternating
electro magnetic field.

4. A linear accelerator (LINAC) is the device most commonly
used for external beam radiation treatments for patients
with cancer.

5. HOW DOSE WORK
• The linear accelerator uses
microwave technology to
accelerate electrons in a part
of the accelerator called the
"wave guide", then allows
these electrons to collide with
a heavy metal target. As a
result of the collisions, high-
energy x-rays are produced
from the target.

6. WHO OPERATES THIS EQUIPMENT ?
• The radiation oncologist .
• The medical radiation physicist.
• The dosimetrist .
• Radiation therapists .

7. HISTORY
• In the late 1940s, the idea of using linear accelerator in
the medical application become interested .
• Medical Linear Accelerators have been in clinical use
since the early 1950s .

8. EARLY ACCELERATORS
▫ The first one was installed at
Hammersmith In 1952 .
▫ In 1956 ,The first patient was
treated at Standford university in
united state
▫ There had an 8-MeV x-ray beam
and limited gantry motion .

9. 2ND GENERATION ACCELERATORS
▫ Second generation were
isocentric units which can rotate
360 degree .
▫ There were built between 1962
and 1982 .
▫ Improved in accuracy and dose
delivery.

10. 3RD GENERATION ACCELERATORS
▫ There were improved in
accelerator guide, magnet
systems, and beam-modifying
systems.
▫ There provide wide ranges of
beam energy, dose rate, field
size and operating modes .
▫ These accelerators are highly
reliable and computer driven

11. COMPONENTS

12. DRIVE STAND :
• the gantry rotates on horizontal axis bearings within the
drive stand , which is secured on the floor in treatment .
• There are four major components housed in the stand :
• 1-klystron / Magnetron .
• 2- waveguide .
• 3- circulator.
• 4- cooling .

13. THE KLYSTRON :
• provides the source of microwave power used to
accelerate electrons . ( By amplifying introduced
radiowaves ).

14. THE MAGNETRONS:
• Electron tube that provide
microwave power to accelerate
electrons .
• Preferred for lower e.Energies.
( > 10 MeV ), for higher
energies Klystron might be a
better choice.

15. COOLING SYSTEM (THE WATER):
• Which is actually a
thermal stability system
, allows many
components in the
gantry and dive stand
to operate at constant
temperature

16. GANTRY :
• detecting the photon (x-ray) or electron beam at
pt’s tumor.
►The gantry consist of:
• Electron gun.
• Accelerator Structure.
• Treatment Head.

17. Electron Gun :
It is responsible for producing electrons and injecting them
into the accelerator structure .
Accelerator Guide :
Accelerator Guide, sometimes called the
accelerator structure, can be mounted in the gantry :
horizontally ( High-energy machines ),
or vertically ( low-energy machines ).
Microwave power (produced in the klystron) is
transported to the accelerator structure , in which
corrugations are used slow the waves .

18. Treatment Head :
Several components designed to
shape and monitor the treatment
beam are located in the treatment
head .
For photon therapy , these
components may consist of bending
magnet, x-ray target , primary
collimator , beam flattening filter , ion
chamber , secondary collimator
, and one or more slots for wedges
, blocks , and compensators

19. MODULATOR CABINET :
 This important component of
the linear accelerator is usually
located in the treatment room
and is the noisiest part of the
ensemble .

20.  In some system , the Modulator cabinet contains three
major components :
 the fan control (cooling the power-distribution system ) .
 auxiliary power-distribution system ( contains the
emergency off button that shuts off the power to the
treatment unit ) .
 primary power-distribution system

21. BENDING MAGNET:
• It direct the e vertically toward
the lying patient .
• It can bend e. group ( 90 – 270º)
toward x-ray target , or toward
scattering foil for e. production )
• Necessary for energies greater
than 6 MeV

22. X-RAY TARGET
• To produce X-ray beams, it’s a transmission target ,
x-rays continue in the forward direction
toward patient.
• It’s placed at the focus of bending magnet.

23. BEAM FLATTENING FILTER:
• A conical metal absorber that absorbs more central
photons than the periphery ones.
• Shapes the X-ray in its cross sectional shape.
• Necessary to create a beam of sufficient area and
uniformity.
• Construction: Tungsten, steel, lead, uranium and
Aluminum.
• In dual energy photons use to 2 beam flattening filters.

24. SCATTERING FOIL:
• The electron beams are in pencil-like shapes.
• These narrow pencil beams need to be broadened and
uniformed .
• Different S.F. for each e. energy .
• Made of Aluminum or Copper.
• Thin Foil (or multiple) , intermediate , or High Z
material .

25. MONITOR IONIZATION CHAMBER:
• Monitor integrated dose, Field Symmetry , and dose
rate .
• Radiation that leaving target or scattering foils passes
through a monitor ionization chamber produces ionizing
current .
• This current is proportional to the beam intensity.

26. COLLIMATORS:
• By adjusting upper and lower collimator jaws .
• Made of High Z# like Tungsten or Lead .
• The jaws create rectangular shape up to 40x40 cm.
• Multileaf Collimators:-
• Heavy, metal field-shaping device used to create
custom blocks.
• It became a key element in treatment delivery with the
advent of IMRT.

27. MULTILEAF COLLIMATORS:

28. TREATMENT COUCH :
• The treatment couch is the
area on which Pt’s are
positioned to receive their
radiation treatment , and It
has the ability to move
• ( updown),(RtLt),(InOut).

29. REFERENCE
 the physics of radiation therapy – Faiz Khan.
 Radiation Oncology Physics-Handbook IAEA 2005.