Vocab List

Question 1

Tumor

Answer 1

Abnormal growth of tissue resulting from uncontrolled progressive multiplication of cells that serves no function.

Question 2

D-max

Answer 2

The depth at which electronic equilibrium occurs for photon beams. Depth of maximum absorbed dose and ionization photons in a treatment field.

Question 3

Given Dose

Answer 3

Dose delivered at the depth of D-max through a single treatment field.

Question 4

Monitor Unit

Answer 4

Unit of output measure used for linear accelerations.

1 mu= 1cGy

Question 5

Isocenter

Answer 5

Point of intersection of 3 axis of rotation of treatment unit.

1. Gantry
2. Couch
3. Collimator

Question 6

Central Axis

Answer 6

Central portion of the beam, emanating from the target. Does not diverge.

Question 7

SSD set up

Answer 7

Distance from source to patient’s skin

Question 8

SAD set up

Answer 8

Distance from source to axis of rotation of the treatment unit.

Question 9

Collimator field size

Answer 9

Open field size, projected at a reference distance, usually isocenter (100cm)

Question 10

Blocked (Effective) Field Size

Answer 10

Equivalent rectangle field dimension of the open treatment area within the collimated field.

Question 11

Photon Energy

Answer 11

Small pocket of electromagnetic energy.

Question 12

Electron Energy

Answer 12

Negatively charged subatomic energy that can be accelerated by a variety of machines or can be admitted from decaying isotopes.

Question 13

Wedge

Answer 13

Tool that modifies the asides distribution of a beam to correct for tissue in homogeneities.

Question 14

Compensating Filter

Answer 14

Correct for tissue and homogeneities.

Question 15

Cerrobend Block

Answer 15

Used to form (shape) the treatment field. 
50% Bismuth
26.7% Lead
13.3% Tin
10% Cadmium

Question 16

MLC

Answer 16

Distinct part of a linear accelerator that allows treatment field shaping through the use of motorized leaves in the head of the machine.

Question 17

Electron Applicator (Cone)

Answer 17

Extended metal structure ised to restrict the useful beam to the required size.

Question 18

Bolus

Answer 18

Tissue equivalent material placed on the skin to increase skin dose and even out irregular contours on the patient.

Question 19

Beamsplit

Answer 19

Allows part of the beam to pass through while reflecting the other part of the beam.

Question 20

Alpha Cradle

Answer 20

Immobilization devices, made from styrofoam.

Question 21

Aquaplast

Answer 21

Thermoplastic immobilization device.

Question 22

Bite Block

Answer 22

Used to helo immobilize and help position the tongue.

Question 23

Positioning Lasers

Answer 23

Used to set up the patient correctly.

Question 24

Single Field

Answer 24

treat the patient with one field

Question 25

Parallel Opposed Field

Answer 25

Paid of fields directed along the same axis, form opposite sides.

Question 26

Tangential Field

Answer 26

Two oblique fields, similar to a breast bridge.

distance from midline to lateral portion

Question 27

Rotation/ Arc Therapy

Answer 27

Isocentric technique when beam moves continuously about the patient.

Question 28

Brachytherapy

Answer 28

Uses radioactive material to deliver dose administered directly into the tumor.

Question 29

Isodoses

Answer 29

Shows distribution of absorbed dose in points of equal dose.

Question 30

Critical Organ Dose

Answer 30

Organs that limit the dose or the dose that can be tolerated by critical sructures.

Question 31

OAR

Answer 31

Organs at Risk

Question 32

Gap

Answer 32

The distance between the borders of two adjacent fields usually measured on the patient’s skin. Used to measure and verify the depth of two adjacent fields.

Question 33

Image Guided Radiation Therapy (IGRT)

Answer 33

The use of imaging to compare the position of external set up marks and internal anatomy to the treatment plan.

Question 34

Intensity Modulated Radiation Therapy (IMRT)

Answer 34

Delivers nonuniform exposure across the beam’s eye view using a variety of techniques and equipment.

Question 35

Volumetric Modulated Arc Therapy (VMAT)

Answer 35

A type of specialized IMRT where VMAT delivers radiation by rotating machine through 1 or more arcs while radiation is continuously delivered.

Question 36

Tomotherapy

Answer 36

Type of rad therapy in which the radiation is delivered slice by slice.

Question 37

Linear Accelerator

Answer 37

Radiation Therapy treatment unit that accelerates electrons and produces x-rays and electron treatment.