Cobalt 60 & LINAC unit

Question 1

Who invented the Cobalt-60 teletherapy machine in Canada in 1950s?

Answer 1

Harold E. Johns

Question 2

It is manufactured in the nuclear reactor by irradiation of Cobalt 59 with slow neutrons for many months.

Answer 2

Cobalt 60 source

Question 3

Half-life of Cobalt 60

Answer 3

5.27 years

Question 4

HVL of Cobalt 60

Answer 4

12 mm lead

Question 5

Smaller source is preferred becos of

Answer 5

smaller penumbra

Question 6

It is the useful beam for treatment?

Answer 6

y-ray beam

Question 7

The y emission of 1.17 MeV and 1.33 MeV gives an average energy of?

Answer 7

1.25 MeV

Question 8

Contaminants of y-ray beam:

Answer 8

Scattered X-ray
Bremsstrahlung X-ray
Electrons

Question 9

Results from the interaction of y-ray with Cobalt-60 source, capsule, housing and collimator.

Answer 9

Scattered X-ray

Question 10

Results from the interaction of B-particle with the source and the steel capsule.

Answer 10

Bremsstrahlung X-ray

Question 11

Results from the interaction of y-ray with plastic tray that holds the block.

Answer 11

Electrons

Question 12

Plastic tray that holds the block

Answer 12

Cerrobend Block (Lead)

Question 13

It is the number of transformations per second for each gram of radionuclide decaying at a fixed rate.

Answer 13

Specific Activity

Question 14

The specific activity of Cobalt-60 source ranges from about?

Answer 14

75 to 200 curies per gram

2.8 to 7.4 TBq per gram

Question 15

The high specific activity makes it possible to fabricate a small source with high y-ray output which results in:

Answer 15

1. Large dose rate
2. Long SSD
3. Smaller penumbra
4. Improved depth dose distribution

Question 16

A typical installation has an output of..

Answer 16

750 to 9,000 Ci

Question 17

Output is usually measured not in Ci but in?

Answer 17

rhm (Roentgen per hour at one meter)

Question 18

The output determines the?

Answer 18

Treatment time

Question 19

The housing used for shielding and containing the device for positioning the source?

Answer 19

Source Head

Question 20

The source head is a steel shell filled with?

Answer 20

Lead, Tungsten, Depleted Uranium

Question 21

The max. exposure rate in off position at 1m distance should not exceed..

Answer 21

2 mR/hr

Question 22

The collimator system should not transmit..

Answer 22

5% of primary beam

Question 23

The source head has a diameter of BLANK and wieghs BLANK

Answer 23

diameter of 1 meter,

weighs 1 ton or more

Question 24

Methods of bringing the source from OFF to ON position:

Answer 24

Rotating Wheel, Sliding Drawer, Mercury Shutter, Shutter

Question 25

Rotation is done by a stall type motor

Answer 25

Rotating Wheel

Question 26

Pulled forward by a motor with spring coming under tension

Answer 26

Sliding Drawer

Question 27

Mercury is allowed to flow into space immediately below the source

Answer 27

Mercury Shutter

Question 28

This is fixed in front of the aperture and consisting of heavy metal alloy

Answer 28

Shutter

Question 29

- Developed by H.E. Johns - Consist of a series of movable interleaved bars. - Made from lead-tungsten/tungsten

Answer 29

Collimator

Question 30

This provides rectangular field size. Equpped with a light localizer (that serves both as a field illuminator and range finder for SSD set-up)

Answer 30

Collimator

Question 31

A device which uses high frequency electromagnetic waves to accelerate charged particles such as electron to high energies through a linear tube.

Answer 31

Linear Accelerator

Question 32

Used to produce high energy electron beam for treating superficial tumors or for treating deep seated tumors.

Answer 32

Linear Accelerator

Question 33

Acceleration of electron is achieved either through:

Answer 33

traveling electromagnetic waves and stationary electromagnetic waves

Question 34

2 types of linear accelerator

Answer 34

direct linear accelerator and helical linear accelerator

Question 35

Major Components:

Answer 35

1. Drive Stand 2. Gantry 3. Treatment Couch 4. Console Electronic Cabinet

Question 36

Klystron, Waveguide, Circular and Cooling System

Answer 36

Drive Stand

Question 37

Electron, Accelerator Structure and Treatment Head

Answer 37

Gantry

Question 38

A special type of electronic tube that generates microwave that is introduced to accelerator structure via waveguide system.

Answer 38

Magnetron/Klystron

Question 39

This produces higher energy radiation and has longer life than magnetron

Answer 39

Klystron

Question 40

A copper tube filled with an insulating gas that conducts the microwave from the klystron or magnetron into the accelerator structure

Answer 40

Waveguide

Question 41

Directs the RF energy into the waveguide & prevents any reflected microwaves from returning to the klystron

Answer 41

Circulator

Question 42

Allows many components in the gantry and drive stand to operate at constant temperature

Answer 42

Cooling system

Question 43

Drive stand:

Answer 43

A. Magnetron/Klystron B. Waveguide C. Circulator D. Cooling system

Question 44

Gantry:

Answer 44

A. Electron Gun B. Accelerator Structure C. Treatment Head

Question 45

Responsible for the production of electrons

Answer 45

Electron Gun

Question 46

Consist of a concave tungsten cathode backed by a tungsten heating coil

Answer 46

Electron Gun

Question 47

Electrons are the injected into the accelerator guide with an initial energy of 50keV

Answer 47

Electron Gun

Question 48

An evacuated cylindrical chamber 1 to 2 m long, divided into compartment called Resonance Cavities

Answer 48

Accelerator structure

Question 49

It has a special inner structure so that microwave power accelerates electrons in a straight path to the correct energy

Answer 49

Accelerator Structure

Question 50

Accelerator guide mounted in the gantry horizontally

Answer 50

In a High Energy Machine (18-25 MV rays)

Question 51

Accelerator guide mounted in the gantry vertically

Answer 51

In a Low Energy Machine (6 MV rays)

Question 52

Provides sufficient shieding against leakage radiation in accordance with radiation protection guidelines

Answer 52

Treatment Head

Question 53

Consist of a thick shell of high density shielding material such as lead, tungsten or lead-tungsten alloy

Answer 53

Treatment Head

Question 54

Treatment Head components:

Answer 54

``` Bending magnet X-ray target Beam flattening filter Dose monitoring chamber Collimator assembly Shadow try Electron scattering ```

Question 55

It functions to bend the electron group through a net angle of approx. 90 to 270 degrees and onto the x-ray target

Answer 55

Bending magnet

Question 56

To produce x-ray, electrons are made to strike a target made of metal such as tungsten, copper or aluminum

Answer 56

X-ray target

Question 57

It equalizes the intensity of the beam over its cross section. (Made from lead, tungsten, uranium, steel and Al)

Answer 57

Beam flattening filter

Question 58

Used for electron beam therapy, the electrons are made to strike a scattering foil to scatter and flatten the beam.

Answer 58

Electron scattering foil

Question 59

- Consist of several ion chambers or a single chamber with multiple plates - Functions to monitor dose rate and field sysmmetry (flatness of beam)

Answer 59

Dose monitoring chamber

Question 60

Plastic transparent tray that supports field shaping blocks for x-ray therapy

Answer 60

Shadow Tray

Question 61

- Limits the beam and provides a continous range of field sizes from 0x0 to 40x40cm^2 - The field size is defined by the localizing system

Answer 61

Collimator

Question 62

Treatment head consists of 2 sets of collimator:

Answer 62

- fixed primary collimator | - movable x-ray collimator