Linac Components Flashcards by Jennifer Montoya

3 main components of linac

drive stand, gantry, tx couch

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modulator sends

sends high voltage flat topped pulsating DC current to klystron & magnetron & e- gun

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fan control switch is part of

modulator cabinet

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fxn of fan control switch

auto turn on/off as needed for cooling

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aux power distrib panel contains what button

emergency off button

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prim power distrib panel supplies

major power route

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magnetron is the source of

high freq microwaves in lower E

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klystron is a ? amplifier

microwave amplifier (not a source) used for high E

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klystron is a component of

drive stand

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wave guide is made of

copper pipes filled w/freon, hexaflouride, or HF6/sulfur

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grid pulse is the force that drives

e- to the accelerator tube

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circulator prevents ?

backflow of microwaves

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e- gun is a component of

gantry

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e- gun introduces

e- into accelerator tube

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accelerator guide is mounted in what direction

mounted horizontally & vertically

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traveling wave accel tube allows e- to ride on ?

high freq microwave in 1 direction only

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in standing wave accel tube, alternating EM flds produce ?

2 alternating high freq waves moving in opposite directions

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drift tube are bunching cavities that regulate?

speed of e- so they arrive in bunches

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bending magnet is a component of

tx head

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bending magnet changes directions of e- and directs them

vertically toward pt

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target is what kind ?

transmission target

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primary collimator limits what

max fld size

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beam flattening filter used for what beam

photon beams only

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scattering foil used for what beam

e- beams only

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monitor ion chamber located where

before 2nd collimator

secondary collimators aka

jaws

MLC define what

define field size & shape

linac temp

- 40 deg C or 104 deg F | - beyond sys will shut down

photon flow thru head

bending mag->target->prim coll->flattening filter->ion chamber->sec coll->wedge->block

e- flow thru head

bending mag->prim coll->scattering foil->ion chamber->sec coll->e- cone

dynamic wedge has minimum ? in wedge direction

field size

concrete vs lead price

concrete less expensive

compensating filter retains what

skin sparing advantage is retained

wedge filter reduces dose over

sloping & obl surface

compensating wedge compensates for

- partial field or irregular shape contour | - missing wedge of tissue

beam hold occurs when dose rate is

too high for mlc to reach proper position

thoraceus filter made up of what

tin-copper-aluminum (cat)

dose monitor unit of linac located

w/i tx head

e- E selected on linac indicates ? on skin surface

probable E

e- beam collimated as close to

the source

sagital laser aligns with

axis of gantry rotation

mlc main advantage

generate field of nearly any size & shape

auxiliary power distribution panel is located where

modulator cabinet

primary power distribution panel is located where

modulator cabinet

pump breaker is located where

modulator cabinet

aux power distrib panel shuts off

power to unit

aux power distrib panel fuses

power & timer for filament

high volt power supply breaker protects modulator by

tripping off when overload

microwaves flow thru ? to accelerator tube

waveguide

gas in ? helps keep microwave from breaking down

waveguide

wave guide is a component of

drive stand

grid pulse is a component of

drive stand

circulator is a component of

drive stand

mach output controlled by variance in ? & RF

grid pulse

? connects klystron to accelerating tube

circulator

accelerator guide is a component of

gantry

drift tube is a component of

gantry

failure of ? affects output E

e- gun

? similar to cathode

e- gun

e- gun made of what metal

W (tungsten)= high Z, high temp

magnetic field interacts with EM microwaves in what

accelerator tube

microwaves have a very distinct

path

e- need to follow ? path in accelerator guide

microwaves

traveling wave accel tube must be

gas evacuated

how many bunching cavities in high E linac

primary collimator is a component of

tx head

target is a component of

tx head

beam flattening filter is a component of

tx head

scattering foil is a component of

tx head

monitor ion chamber is a component of

tx head

secondary collimator is component of

tx head

MLC is a component of

tx head

ODI is a component of

tx head

bending magnet for high E is

270 deg

bending magnet for low E is

90 deg

bending magnet for very low E is

no magnet b/c mounted vertically

focal spot of e- stream upon exiting magnet is ?

3mm

target is made of what

W- tungsten

target is retracted for ?

primary collimator is fixed or able to move

fixed

primary collimator is located where in tx head

below target and above flattening filter/scattering foil

beam flattening filter makes the beam more?

homogenous

beam flattening filter shape

thicker in center and thinner at edges

beam flattening filter located where

on carousel in tx head

beam flattening filter does what

absorbs more photons from center & less from periphery of beam

scattering foil is made up of what

2 foils stacked on each other, separated by a few cm

scattering foil closest to source is made of what/does what?

- Pb | - scatters (broadens) beam & makes 3mm pencil beam

scattering foil lower made of what/does what?

- low Z | - flattens e- beam

scattering foil located where

carousel in tx head

scattering foil can create what radiation

usu < 5% brems

monitor ion chamber registers what

radiation output (integrated dose) & records field flatness & beam symmetry

monitor ion chamber how many

2 required

secondary collimators do what

moveable & define field size

dynamic wedge has minimum ? at toe of wedge

collimator setting

dynamic wedge has minimum what?

dynamic wedge not compatible with what on some blocked fields

MLC direction

concrete vs lead shielding of n

- concrete better | - Pb must have borated plyethylene to shield n

concrete vs lead installation

concrete easier

compensating filter used to avoid

bolus effect

compensating filter distance from pt

at least 15 cm (20cm according to khan)

compensating filter shaped to mimic

various depths of missing tissue

compensating filter made of what

Al, Pb, Pb plastic, cerrobend

compensating filter used most with what tx

lung, h&n

wedge filter depends on

depth & field size

wedge filter is the angle between

50% isoline & perpendicular to beam CAX

wedge filter higher E machines use

70-80% isolines with wedge

beam hold is when the beam is turned off until

mlcs catch up