Clinical Radiation Generators

Question 1

used to describe treatment with beams of very soft (low-energy) x-rays produced at potentials below 20 kV.

Answer 1

grenz-ray therapy

Question 2

A ______ or _____ operates at potentials of 40 to 50 kV and facilitates irradiation of accessible lesions at very short source (focal spot) to surface distances (SSD).

Answer 2

contact therapy, endocavitary machine

Question 3

have been used in the treatment of superficial rectal cancers.

Answer 3

Endocavitary x-ray machines

Question 4

The term _____ applies to treatment with x-rays produced at potentials ranging from
50 to 150 kV.

Answer 4

superficial therapy

Question 5

This machine operates typically at a tube current of 2 mA.

Answer 5

Contact therapy

Question 6

A filter of 0.5- to 1.0-mm-thick aluminum is usually interposed in the beam to absorb the very soft component of the energy spectrum. What type of machine is this?

Answer 6

Contact therapy

Question 7

This machine is usually operated at a tube current of 5 to 8 mA.

Answer 7

Superficial therapy

Question 8

The term _____, or deep therapy, is used to describe treatment with x-rays produced at potentials ranging from 150 to 500 kV.

Answer 8

orthovoltage therapy

Question 9

Most orthovoltage equipment is operated at ____ kV and ___ mA.

Answer 9

200 to 300, 10 to 20

Question 10

X-ray therapy in the range of 500 to 1,000 kV has been designated as ____.

Answer 10

high-voltage therapy or supervoltage therapy

Question 11

_____ units have been used to generate x-rays from 300 to 2,000 kV.

Answer 11

Resonant transformer

Question 12

X-ray beams of energy 1 MV or greater can be classified as ____

Answer 12

megavoltage beams

Question 13

The ______ machine is an electrostatic accelerator designed to accelerate charged particles.

Answer 13

Van de Graaff

Question 14

Van de Graaff machines are capable of reaching energies up to ____

Answer 14

10 MV

Question 15

This generator is enclosed in a steel tank
and is filled with the gas mixture at a
pressure of about 20 atm.

Answer 15

Van de graff

Question 16

_____are used for generating high-energy x-ray beams, mostly in the range of 4 to 25 MV, and electron beams in the range of 4 to 25 MeV.

Answer 16

Medical linear accelerators (LINAC)

Question 17

Medical linear accelerators (LINAC) are
used for generating high-energy x-ray
beams, mostly in the range of _____,
and electron beams in the range of ____

Answer 17

4 to 25 MV, 4 to 25 MeV

Question 18

‒The _____ in which the electrons are accelerated by microwaves, consists of a highly evacuated vacuum tube with its
interior divided by copper discs or diaphragms of varying aperture
and spacing.

Answer 18

ACCELERATOR STRUCTURE

Question 19

‒ A section of electronics where direct current (DC) voltage is converted
into high-voltage flat-topped DC pulses of a microseconds in duration.

Answer 19

MODULATOR

Question 20

This prevents the microwave reflections from returning to the microwave power source (magnetron/ klystron).

Answer 20

Circulator

Question 21

‒A rectangular copper tube to provide a path for microwaves to travel from the source (magnetron or klystron) to the accelerator structure.

Answer 21

WAVE GUIDE

Question 22

‒ A device that produces microwaves.

Answer 22

MAGNETRON

Question 23

It functions as a high-power oscillator,
generating microwave pulses of several microseconds duration and with a
repetition rate of several hundred pulses per second.

Answer 23

Magnetron

Question 24

is a microwave amplifier

Answer 24

Klystron

Question 25

Treatment head consists of a well-shielded shell of ____ alloy.

Answer 25

lead-tungsten

Question 26

In LINAC, the focal spot is approximately ____ in diameter.

Answer 26

2 to 3 mm

Question 27

The ____ is usually made of thick piece of lead and has a conical shape-thick in the middle and thin around the periphery to provide differential attenuation.

Answer 27

flattening filter

Question 28

The point of intersection of the collimator axis and the axis of rotation of the gantry is known as the ______.

Answer 28

isocenter

Question 29

____ is an electron accelerator that combines the principle of both linear accelerator and cyclotron.

Answer 29

Microtron

Question 30

uses a standing wave linac structure (instead of single cavity as in a circular microtron) to accelerate electrons. Such an accelerator is suited for higher energy beams (e., 50 MV).

Answer 30

racetrack microtron

Question 31

Betatron is developed by _____ in ___

Answer 31

Donald William Kerst, 1941

Question 32

Can provide x-ray and electron therapy beams over a wide range of energies, from less than 6 to more than 40 MeV, they are inherently low-electron-beam current devices.

Answer 32

Betatron

Question 33

A charged particle accelerator, mainly used for nuclear physics research.

Answer 33

Cyclotron

Question 34

In radiation therapy, these machines have been used as a source of high-energy protons for proton beam therapy.

Answer 34

Cyclotron

Question 35

Half life of C-60

Answer 35

5.26 years

Question 36

Y ray energy of C-60

Answer 36

1.17, 1.33 MeV

Question 37

Of all the radionuclides, it has proved to be the most suitable for external beam radiotherapy.

Answer 37

60Co

Question 38

usually in the form of solid cylinder, discs, or pellets, is contained inside a standard stainless-steel capsule and sealed by welding.

Answer 38

60Cobalt source

Question 39

The term ___ means the region, at the edge of a radiation beam, over which the dose rate changes rapidly as a function of lateral distance.

Answer 39

penumbra

Question 40

§ It is the transmission through the edge of the collimator block. § The region irradiated by photons which are transmitted through the edge of the collimator block. § The inner surface of the blocks is made parallel to the central axis of the beam. § The extent of this penumbra will be more pronounced for larger collimator opening.

Answer 40

Transmission Penumbra

Question 41

Caused by the source (or focal spot) having finite size

Answer 41

Geometric penumbra

Question 42

Is dose gradation zone caused by the combined effect of transmission penumbra, and lateral scatter of radiation (photon and electrons) within the patient.

Answer 42

Physical Penumbra