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Polystyrene and Water as Soft Tissue Substitutes in

Radiotherapy Dose Calculations:

A Monte Carlo based Inter-Comparison

By

Ambreen Aslam

M.Phil. Physics 4thSemester

University Of Agriculture , Faisalabad

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Cancer

In Paistan cancer is amon! the ma"or causes of death# $arious

factors are causin! a massi%e cancer& such as :

Increased Population

'(cessi%e use of Tobacco

)nhealthy Diet

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Paistan Cancer !an by "y#e $%&O'()(*

# Type of Cancer Rate WorldRank

# Type of Cancer Rate WorldRank

1 *reast +,# ./ , *ladder 0#/1 /2

2 3ral ,#42 +2 +2 5i%er 0#1, +60

3 5un! 6#/+ +0+ ++ Prostate 0#. +14

4 Stomach 1#11 ,6 +0 3%ary 0#1 /+

5 Cer%ical 1#.1 6/ + 3ther 7eoplasms +#.6 +46

6 'sopha!us 1#+6 40 +4 Pancreas 2#,2 +60

7 5ymphomas 4#/. +21 +. )terine 2#.+ +40

8 Colon-Rectum 4#2/ +4, +1 Sin 2#+ +62

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"reatment "y#es

Common cancer treatment types include : Chemotherapy

Radiotherapy

Tar!eted Therapy

Photo-dynamic Therapy

8here Radiation therapy or radiotherapy is the most commontreatment of cancer& it uses hi!h-ener!y particles to destroy or

dama!e cancer cells# It is most effecti%e treatment of cancereither by itself or alon! 8ith other forms of treatment#

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Cancer "reatment using!adi+thera#y

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Phant+ms

Phantoms are models of the human body9or!ans usedin computeried analysis#

Phantoms are desi!ned to impro%e the accuracy of

treatment plan %erification in radiosur!ery andradiotherapy#

They allo8 D dose %erifications and estimate the most

probable dose distributions sho8in! their response fordifferent beam ener!ies on numerous tissue and bonee;ui%alent materials#

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"he C!S !adi+surgery &eadPhant+m

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M+nte Carl+ "echni-ue

To simulate radiation transport in radiotherapyMonte Carlo techni;ues are used 8idely and are

pro%ed to be most effecti%e#

Monte Carlo techni;ues are based upon samplin!the random numbers#

These techni;ues are bein! used from last fifty

years and there are commercial treatments plannin!systems employin! Monte Carlo codes#

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/Snrc

'

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Sub C+des +f /Snrc

The EGSnrc CodeSystem

+thersub0

c+des

1OS23nrc

$Phant+m 1esign

and

m+deling*

BAMnrc

$56AChead

M+deling*

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BAMnrc

The *'AMnrc code 8as desi!ned to simulate radiation beams

emer!in! from any radiation source lie Co-12 =Cobalt-12>

and lo8 ener!y (-rays#

this '#

This code 8as 8ritten in M3RTRA7& 8hich is a

preprocessor for @3RTRA766#

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1OS23nrc

D3SBnrc is another '

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Pr+7ect Meth+d+l+gy

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Phant+m Materials

Phantom

Materal

!effCompo"ton

=fraction by 8ei!ht>

Ma"" attenaton

coeffcent

$m2%k&'

Ma"" ener&y

a("orpton

coeffcent

$m2%k&'

)lectron

*en"ty

$e%&'

+oft T""e 7,64

1$-,1-1172'

6$-,111---'

7$-,-26---'

8$-,7618283'

2,74.1-/3$6 M0'

2,1.1-/3$1- M0'

1,78.1-/3$6 M0'

1,54.1-/3$1- M0'3,32.1-23

Poly"tyrene 5,741$-,-77418'

6$-,22582'

2,62.1-/3$6 M0'

2,-6.1-/3$ 1- M0'

1,7-.1-/3$6 M0'

1,44.1-/3$1- M0'3,23.1-23

PMM 6,56

1$-,-8-538'

6$-,5848'

8$-,31614'

2,65.1-

/3

$6 M0'

2,1-5.1-/3$1- M0'

1,72.1-

/3

$6 M0'

1,48.1-/3$1- M0'3,24.1-23

Water 7,511$-,11184'

8$-,8881-6'

2,77.1-/3$6 M0'

2,21.1-/3$1- M0'

1,8-.1-/3$6 M0'

1,56.1-/3$1- M0'3,34.1-23

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Pr+7ect Parameters

eam )ner&e" 1M$& +2M$

Phantom

*men"on"+.+.4. cm

0oel "e 2#. cm

eld +e" .. cm0 & +2+2 cm0

# of "tore" +#. billion

Calclaton" PDDs& Profiles

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Phant+m 1imensi+ns

! lt

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!esults

). Comparisons of PDDs for Soft Tissue Equivalence ofPMMA

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'. Comparisons of PDDs for Soft Tissue Equivalence ofPolystyrene

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8. Comparisons of PDDs for Soft Tissue Equivalence of Water

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Mean 9 1i:erence f+r 1i:erent S" e-uivalentMaterials $P+st0Buildu# !egi+n*

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Mean 9 rr+r f+r 1i:erent S" e-uivalent Materials$P+st0Buildu# !egi+n*

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C+nclusi+ns

@or 1 M$ smaller field sie is better& and for +2 M$ lar!er

field sie is more useful for substitution of these materials as

Soft Tissue ';ui%alent#

The composition and other properties of a material should be

close to those of reference material in order to become

e;ui%alent or substitute#

Water is most Soft Tissue e;ui%alent Material amon! all other

tested phantoms#

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Future !ec+mmendati+ns

7o lar!er field sies for input beams 8ere tried for this 8or&

it can also be e%aluated for +.+. cm0& 0202 cm0& 0.0. cm0

and 22 cm0#

3ther photon beam ener!ies such as Co-12 and +0 M$& 02

M$& 04 M$ etc# can also be used for the current 8or#

3ther phantom materials that ha%e composition closer to SoftTissue and Water such as Solid Water& Plastic Water etc can

also be e%aluated for substitution purposes#

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"han 3+u ;