16_06_2014_tps historical overview.pdf

8/11/2019 16_06_2014_TPS historical overview.pdf

1/15

D r. R o zen fe ld is a ra d ia tio n p h ys ic is t a t S t. Ja m e s H o sp ita l in C h ica go H e ig h ts , Ill in o is .

A d d res s rep rin t re qu e s ts to M a rtin R o zen fe ld . P h .D .. D e pa rtm e n t o f R ad ia tio n O n co lo gy . S t. Ja m e s H o sp ita l, C h icag o

H e igh ts . IL , 6 04 1 1 .

V o lu m e 8 , N u m be r 3

{149}

a y , 19 88

{149}

adioGr aphics

5 5 7

T re a tm e n t P la n n in g w ith E x te rn a l B e a m s

In tro d u ctio n a n d H is to r ica l O v erv ie w

M a rtin R o z e n fe ld , P h .D .

E dito rs N ote :

A va lue d fe a tu re o f the A nn ua l M e e tin gs o f th e R S N A

fo r m a ny ye ars h as b ee n th e S y m p os ium o n B a s ic P hys ics

p rep a red an d p re se n te d by a c om m itte e o f th e A m e rican

A sso c ia tio n o f P h ys ic is ts in M e d ic in e in co op e ra tion w ith

th e P ro g ram C om m itte e o f the R S N A . R a d ioG rap h ics is

p le ase d to pu b lis h th e sy m po s ium pre se n te d o n N o ve m b er

2 8 , 1 98 7 in co n jun c tio n w ith the 7 3 rd S c ien tif ic A ss em b ly

a nd A nn ua l M e e ting o f th e S oc ie ty . T he sy m p os iu m . T re a t-

m e n t P la nn in g w ith E x te rn a l B ea m s w ill ap pe a r s e ria lly in

th is a nd su bs eq u en t issu e s o f R ad io G ra ph ics .

T h is firs t a r tic le in the s e ries p rese n ts an in trod u c tio n to

e x te rn a l p ho ton b ea m trea tm e n t p lan n ing . In s ub se qu en t

iss u es , D r. J o hn

C u nn in gh a m w ill co ns ide r d os im e tric p rin c i-

p Ie s ; D r. F ra n k H e n d rick so n w ill d is cu ss th e ro le o f the ph y s i-

c ian . e m p h as iz ing the im po rtan ce o f c lo se co op e ra tion

be tw e e n ph ys ic ia n an d ph ys ic is t; D r. S ub ra m a n ia J aya ra -

m a n w ill id en tify the m an y co n trib u tio ns o f the c lin ica l

ph ys ic is t to trea tm e n t p la nn in g ; an d D r. G orn S v en sso n w ill

ex p lo re the a ll- im po rtan t s ub je c t o f q ua lity as su ra n ce .

O ne o f the o b jec tive s o f R a d io G rap h ics is to kee p th e

su bsp e c ia lis t p h ys ic ia n ab rea s t o f d eve lop m e n ts in o the r

as pe c ts o f rad io lo g y . W e b e lie ve th is se r ie s ad m irab ly fu l-

f ills th a t ob je c tiv e an d w ill p ro ve to be o f in te res t to d ia g -

no s tic an d the ra pe u tic ra d io lo g is ts a like .

R a d io lo g is ts w ho w ish to use th is m a te ria l fo r g rou p

te ac h ing o r w h o , fo r o th e r re a son s , d e s ire it in an au d iov i-

su a l fo rm a t a re rem in de d th a t th is a n d m o s t p re v io u s sym -

po s ia a re ava ilab le as

s l ide - tape

se ts tha t m a y b e o r-

de re d b y w rit ing to R S N A E d uc a tio n a l A ud io -V isu a l

M a te ria ls . P .O . B o x 10 1 68 , C h ica go . IL 6 0 61 0 . o r b y ca llin g

(3 12 ) 9 43 -0 45 0.

In t r oduct ion

R e cen tly , th e re ha ve b ee n a nu m be r o f

sy m po s ia dn d ca te go rica l co u rse s d evo te d to

va rio us a sp ec ts o f ra d ia tion trea tm en t p lan -

n ing . T h is s e ries o f a rtic les is de s ign ed to

p res en t th is im po rta n t m a te ria l so tha t th e na d i-

o log y res ide n t ca n ga in an ov e rv iew o f th e

sub jec t in s u ffic ie n t de ta il to und ers ta nd th e

con ten t as w e ll as the s ign ific an ce o f m ore

co m p le x m a te ria l an d fu tu re d ev e lop m en ts .

T h is , the firs t a rtic le in th e se rie s , w ill p res en t

som e h is to ry and g iv e an in trod uc tion and

ove rv iew o f e x te rn a l b eam trea tm e n t p la n -

n ing w ith ph o ton bea m s.

H is tor y

In e xam in in g the h is to ry o f tre a tm e n t p lan -

n in g w ith e x te rna l be am s , it is ins truc tive to

c on s ide r the firs t tre a tm e n t o f c an ce r w ith x

ra ys a s d esc rib ed in th e b oo k e n titled , T he

L ife a nd T im es o f E m il H . G nu bb e , by P au l C .

H o dg es , M .D . T h is firs t tre a tm en t is re po rte d to

h av e be en de live re d b y E m il G ru bb e in C h ica -

go , o n Ja nu ary 29 , 18 96 , a few m o n ths a fte r

th e d isco ve ry o f x ra ys .

W h ile s till a m e d ica l s tude n t a nd bu ilde r o f

C ro ok es tub es , G ru bbe be ga n ex perim en tin g

w ith x ra ys a s s oo n as he h eard o f R oe n tge n s

d isco ve ry . T o tes t the h a rdn es s o f h is

C ro oke s tub e be am , h e w o u ld fluo ro sco pe h is

o w n ha nd . T h is soo n le d to itch ing , s w e lling , in -

flam m atio n a nd b lis te rin g . T h e id ea o f u s in g x

n ay s to trea t ca nc e r oc cu rre d to sev e ra l o f

G ru bb e s m e d ica l sch oo l in s truc to rs w h en the y

s aw the re ac tion o n the ba ck o f h is le ft h and .

A pa tien t w ith rec u rren t b rea s t c an ce r w as m e-

fe m m ed to G m ub be fo r x -ray tre a tm e n t b y on e o f

th os e in stru cto rs .

T h is firs t trea tm e n t w as pe rfo rm ed w ith a

C n oo kes tu be p lac ed in co n tac t w ith th e s k in ,

w ith sh ee ts o f lea d u se d to d e fin e the fie ld .

T he trea tm en t tim e w as es tim a te d fro m the

tim e ne ces sa ry to p ro duc e the rea c tio n o n

G ru bb e s ha nd . T h e firs t rad ia tio n tre a tm en t

w as d e liv e red in 1 8 fra c tio ns w ith a trea tm e n t

tim e o f o ne h our ea ch .


2/15


3/15

-I

-I

0

a

B

0

3

.u

a

3

3

3

Ia

T re a tm en t V ar ia b les

S o urc e: IC R U R ep ort 2 9

T he ne x t p rob lem fac ed , the n as n ow , is

c hoo s ing th e trea tm en t va ria b les tha t w ill y ie ld

th e d es ire d d os e d is tr ib u tion . A com prom ise is

inva ria b ly req u ired to ac h ieve a h igh u n ifo rm

d ose th ro ug ho u t th e ta rge t v o lum e w h ile m in i-

m iz ing th e d os e

to c ritic a l o rg a ns . H o w c lo s e ly

o ne re ach es the id ea l d ep en ds o n a n um b er

o f fac to rs re la ted to the s ize , sh ap e an d loc a -

tion o f the ta rg e t vo lum e as w e ll as to th e ca -

pa b ilit ie s o f th e trea tm en t m a ch ine a nd tre a t-

m e n t

p la nn in g fa c ilit ie s a s o u tlin ed in T ab le IV .

R oz snfs ld T rea tm en t p lann ing

V o lum e 8 , N um b er 3 {149} ay , 1 98 8 {149}a d l o G r a p h i c s

5 5 9

te rm s u se d in d os im e try to avo id co n fus io n

w he n co m m un ica ting w ith p hy s ic is ts on o th e r

na d io the rap is ts . N o te , ho w eve r, tha t th ese

do se de fin itio ns re fe r to ta rge t areas , w h ile the

p re v io u s d e fin itio n s re fe rred

to ta rg et vo lumes .

It is im po rta n t to k eep in m ind tha t trea tm en t

p lann in g m u st b e do ne in th re e d im e ns ion s .

A ny tw o d im e ns io na l p lan , fo r w h ich the se d e f-

in itio ns ap p ly , as sum es u n ifo rm ity o f th e s ize

an d s ha pe o f a ll th e s tru c tu res in th e th ird d i-

m en s io n . T h is as sum ptio n m a y, o n m ay n o t, in -

trod uce a s ign ifican t e nn on in a ny p artic u la r

c as e .

In m o de rn p rac tice , the th ree d im e ns io na l

ta rge t vo lum e is g en era lly de te rm ine d by

ph ys ica l e xam in a tio n an d c lin ica l jud gm e n t

a ide d b y a h os t o f ex p lo ra to ry an d im a g ing

tech n iqu es . D e sp ite the use o f the se m od ern

d iag no s tic tec hn iqu es , th e de te rm in a tion o f

the s ize an d loc a tio n o f the tissu es to be in ra d i-

a ted ca nn o t be d on e w ith a p rec is ion co m e -

sp on d ing to tha t o f m od ern tre a tm e n t m a -

ch in es . H e nc e , c lin ic a l jud gm e n t m u st p la y a

m a jo r ro le in ch oo s ing the ta rg e t vo lu m e.

T ab le lii

D o se D e fi ni ti on s

A . T he m ax im um ta rg et a bso rbe d do se is

th e h ig he st a bs orb ed d os e in th e ta rg et

a r ea t ha t can b e r e ga rd e d a s cli ni ca ll y

m ean ing f u l

...

T he m in im um a re a reco m me nde d fo r

th is p urpo se is 2 cm 2 ...

B . T h e

m in im um ta rg et ab so rb ed d ose is

th e lo we st a bso rb ed d ose in th e ta rg et

a rea . N o are a lim it is reco m me nd ed

w he n re po rting m in im um ta rg e t a b -

s orb e d d o se .

N o te : F o r th e fo llo w in g d e fin itio n s , ca l-

cu la te the dos e a t e ach o f a la rge nu m-

b e n o f la tti ce p o in ts , u n if or m ly d is tn ib u t-

e d in th e ta rg et a re a.

C . T he m ea n ta rg et a bso rb ed d ose is th en

ca lcu la te d a s th e m ea n o fth e a b so rb e d

d o se v alu e s in th e se la ttic e p o in ts . .

.

D . T h e m ed ian ta rge t ab so rb ed do se is

the c en tra l v a lue am ong th e se t o f v a l-

ue s o f the a bs o rbe d d os e a t a ll la ttice

po in ts in the ta rg e t a rea , w he n am -

r an g ed a cc or din g to m a g nitu d e.

E . T he m oda l ta rge t a bs o rbe d d os e is the

a b so rb e d d o se th a t o c cu rs m o s t fre -

qu en tly a t la ttice po in ts in th e ta rg et

area.

T ab le IV

C ho os in g T rea tm en t V ariab le s

1

.

B e a m typ e a n d e n e rg y

2.

T r ea tm e n t s e tu p

a . G e o m e tr ic a l c o ns id e ra tio n s

b. C om bin in g b ea ms

3. D o se c alc ula tio n

a. B as ic b ea m da ta

b . M e th o ds fo r c alc ula tin g d o se d is tr ib u tio n s

c . M etho ds fo r c a lcu la ting trea tm en t tim es o r

m o n it or u n its


4/15

U)

0

.0

a

a

>1

4-

C

S

E

4-

a

S

I-

I M on ito r u n its = th e d ig ita l rea do u ts o f the m o n ito r io n iza tio n c ha m b ers o f h ig h en e rgy th e ra p y m a ch in es .

2 A n is oce n tr ic the ra py un it is o ne in w h ich the x -ra y b e am is con s ta n tly d irec te d a t a fix ed po in t o n the a x is ab o u t

w h ich the u n it ro ta tes ; a no n iso cen tric th e rap y u n it p e rm its th e d irec tio n o f the b ea m to be va ried b y m e an s o f s up po rt-

ing , tra ns la ting an d p iv o tin g m e ch an ism s.

T rea tm en t p la nn in g R oz snfs id

5 6 0

R a d i o G r a p h i c s

{149}

a y , 19 88

{149}

o lum e 8 , N um b er 3

G e ne ra lly , low e r ene rg ies sho u ld b e u sed

fo r les io ns ap proa ch in g the s k in , w h ile h igh e r

e ne rg ies w ill be n ec ess a ry to tre a t a ce n tra lly

loc a ted les io n in a la rge p a tien t a de qu a te ly .

T h is is on ly o ne exa m p le o f the m an y g eo m etm i-

c a l co ns ide ra tio ns th a t m ust be take n in to ac -

c ou n t to ach ieve th e d es ired do se d is tr ib u tio n .

A n um ber o f the se , es pe c ia lly m e tho ds fo r

co m b in in g bea m s, w ill be con s ide red in g rea t-

e m d e ta il la te r. F ina lly , the ca pa b ilit ie s o f the

d os im e tn ic m e th ods m u st be ca re fu lly co ns id -

e m ed , s ince the y a re v e ry im p ortan t c om p o-

n en ts o f th e too ls ne ed ed fo r tre a tm en t p la n -

n ing . B a s ic be am d a ta w ill n o t o n ly be nee de d

to c a lcu la te do se d is tr ibu tion s fo r p ro po se d

trea tm en t p lans , b u t a ls o to ca lc u la te th e

trea tm e n t tim e o n m o n ito r un its1 to de live r th e

p res cribed d os e .

In p rac tice , a ll the bas ic be am da ta lis te d

in T a b le V a re ba se d on m e asu rem e n ts . T he o-

ne tica lly , th e b ea m ca n be d iv ide d in to p rim a -

m y a nd sca tte r co m po ne n ts . O n e w a y to e s ti-

m a te the p rim ary co m p on en t in a ph an to m is

b y ex tra po la ting m ea su red de p th -d ose da ta

to z e ro fie ld s ize w h ere the re s ho u ld be n o

sca tte r. D iffe re n t trea tm en t m a ch ine s sho w

d iffe ren t va ria tio ns in d ose an d en erg y as

fu nc tion s o f th e d is tan ce be tw e en th e p o in t o f

m ea sure m en t an d th e c en tra l a x is o f the

b ea m . T he to ta l b ea m da ta a lo ng the cen tra l

a x is can b e p res en te d in d iffe ren t w ay s . P en -

ce n t de p th do se is t h e m o st co nv en ie n t to use

w ith n on is oce n tn ic2 u n its , w h ile th e o the rs a re

m o re c on ven ien t fo r iso ce n tn ic trea tm en t m a -

ch ine s . It is im porta n t to re co gn iz e , h ow e ver,

th a t ea ch o f thes e e xp re ss ion s o f be am d a ta

p rov ide s a m etho d fo r de te rm in in g , on the ba -

s is o f a ca lib ra tion a t a s tan da rd lo ca tion an d

fo r a s ta nd ard fie ld s ize , th e d os e a t a d iffe ren t

d ep th a nd fo r a d iffe re n t fie ld s ize . T he m a in

d iffe ren ce in the va riou s w a ys o f e xp re ss ing to -

ta l b ea m d a ta is i n the ch o ice o f co nd itio ns fo r

the s ta nd ard ca lib ra tion . P e rcen t d ep th d o -

se in c lud es be am atte nu a tion , a nd in ve rs e -

sq ua re e ffe c t.

T he m e are , in g en era l, tw o w a ys th a t th is

m e asu red d a ta ca n b e m an ip u la ted to d e te r-

m in e the c om p le te d ose d is tr ib u tio n fo r cas es

o f c lin ica l in te res t. T h es e a re lis ted in T ab le V I. In

on e , th e co n trib u tion s o f th e p rim ary an d sc a t-

te re d ra d ia tio n a re co n s ide re d sep ara te ly an d

are the n c om b in ed a fte r co rrec ting e ach fo r

the co nd ition s o f th e sp ec ific ca se . In the o th e r

m e th od , co nn ec tion s a re ap p lie d d ire c tly to th e

m ea su re d da ta . T he firs t m e tho d is m o re ge ne n-

a l; it can be a pp lied to a lm o st an y c lin ica l s itu a -

tio n . T he s eco nd m e tho d requ ire s le ss com pu-

ta tio n . T he va riou s tech n iqu es th a t h av e b ee n

de ve lop ed fo r c on ne c tin g the to ta l b eam da ta

a re lis te d in o rde r o f a cc u rac y a nd co m p le x ity .

T a b le V

B as ic B e a m D ata

A .

Pr imary

b e a m

1 .

Z e ro fie ld d o se

2.

O ff

a x is r at io

3 , R a dia l e n er gy v ar ia tio n

B . S c atte re d r ad ia tio n

1

. C o l li m a to r s c a tt e r

2 . P h an to m s ca tte r

C T ota l b ea m d ata

1

.

P erc en t d ep th d os e, P D D

2 . T is s ue a ir

rat io , T A R

3 . T issu e m ax im um ra tio , T MR

4,

T is su e p ha nto m ra tio , T P R

T a b le V I

M e t h o ds f o r C a lc u la ti n g D o s e D i st ri b u ti o n

A . A dd ition o f p rim ary b eam an d s ca tte r co ntn i-

but ions

B . C orre ctio ns to s ta nd ard d ata fo r irre gu la r s um -

f ac e s a n d t is s ue h e te ro g e ne it y

1

.

E f fe c ti ve a t te n u a ti o n c o e ff ic ie n t

2 . Is o d o se s h if t m e th o d

3 . E ffec tive S S D (so u rce s k in d is ta nce )

method

[ 4.

E q uiv ale n t T A R ( tis su e a ir r atio ) m e th o d

5,

Batho p o w e r law m eth o d


5/15

-I

0

a

B

0

3

IC

a

a

a .

0

U,

s en .

A . S ou rc e s kin d is ta nc e

( SS D ) tr ea tm e n ts

1 . O u tp ut in a im a td

2 . B ac k s c a tte n fa c to r

3 , P erc en ta ge d ep th

dos e

R oz enfe ld

T rea tm en t p lann ing

V o lu m e 8 , N um b er 3 {149}

T h e d iffe re nce s in th e m eth od s fo r co rn -

pu tin g the trea tm en t tim e or m o n ito r un its fo r

so u rce s k in d is tan ce (S S D ) and s ou rce a x is d is -

tan ce (S A D ) te chn iq ue s m u st be re co gn ize d

s inc e th ey a re bo th in c om m o n u sa ge . A s m d i-

ca te d in T ab le V II, the o rig in a l m e tho d fo r th e

S S D tec hn iq ue w a s ba se d on a n in a ir ca li-

b ra tion a t the re fe ren ce d is ta nc e . T he n th e

ba cks ca ttem fa c to r an d p erce n ta ge de p th

do se w e re ap p lie d to o b ta in th e do se ra te a t

the d es ired d ep th a nd fie ld s iz e . W ith h ig h en -

e rg y u n its , the ca lib ra tion is c o m m on ly a t th e

d ep th o f th e m a x im um do se in a p han tom , so

th e ba cks ca tten fac to r is a lre ady ac cou n te d

fo r. F o r the S A D te ch n iqu e , th e ca lib ra tio n is

d on e a t th e is oc en te m , e ithe r in a ir, a t d m a x , o n

a t a n a rb itra ry de p th . T he n th e a pp ro p ria te m a-

tio , tis sue a ir ra tio (T A R ), tiss ue m ax im um ra tio

( T M R ) or tissu e ph an tom ra tio (T P R ) is us ed to

o b ta in the d ose ra te a t th e d es ired fie ld s iz e

a nd w ith the a pp ro p ria te de p th o f ov e rly in g

tissu e . T he fo rm u la s us ed fo r the S S D an d S A D

ca lcu la tion s ap pe ar id en tica l, ho w e ve r, th e

po s ition o f the re fe ren ce po in t is d iffe ren t. In

S S D ca lc u la tio ns , it is ta ke n to be a t th e d ep th

o f th e m ax im u m do se ; in S A D c a lcu la tion s , it is

tak en to be a t the iso ce n ten . T h us , an in ve rs e

sq ua re c on ne c tio n w ill be ne ces sa ry w he n

sw itch ing fro m o ne te chn iq ue to th e o th e r w ith

a g ive n tre a tm en t u n it.

C onst r a ints

F re qu en tly , o ne w o u ld lik e to b e a b le to

im p lem e n t a sp ec ific s e tup on ly to fin d tha t

the lim ita tio ns o f the eq u ipm en t o r the po s itio n

o f the le s ion p lac es c on s tra in ts o n w h a t can

be ac h ieve d . A s ind ica ted in T ab le V III, no n iso -

ce n tric u n its a re g en era lly ve ry flex ib le w ith m e -

sp ec t to a im ing th e be am an d can p rov ide tis -

su e c om p ress io n w ith c lo se d -en d co ne s . T he y

a re aw kw a rd , ho w eve r, in d irec ting m u ltip le

T ab le V II

M eth o d s fo r C o m pu tin g T re a tm en t T im es o r M on ito r U n its

B . S o urc e a xis d is ta nc e (S A D)

t reatments

1 . 1e fe m e nc e p o in t in a ir

a . O u tp u tin a im

b . T is su e a imr a tio

( T A R )

2.

R e fe re n ce p o in t a t

dm

a . O u tp u ta td

b .

T is s ue m a x im u m

r at io ( T M R )

3 . R efe re nc e p oin t

a t a rb it ra ry d e p th

a . O utpu t a t cho se n

dep t h

b . T is su e p ha nto m

ratio ( T P R )

be am s a t a ce n tra l lo ca tion . A g iven is oce n tn i-

ca lly m o un ted un it on the o th e r h an d , fac ili-

ta te s d ire c tin g m u ltip le b ea m s a t a co m m o n

vo lum e , bu t m ay no t ha ve th e sp ec ific fea tu re

tha t w ou ld b e id ea l fo r a g iven trea tm e n t

p lan . L im ita tio n o f c om p u ta tion a l cap ab ility

m ay in tro du ce d iffe ren t e rro rs , d ep en d ing o n

the pa rticu la r cas e an d trea tm e n t p lan ch o -

T ab le V III

C on stra in ts in C ho os in g

T re a tm en t S e tu p I

A .

T re a tm e n t m a c h in e

1

.

X -r ay o r e le ctr on e n er gie s

2 . N on is o c e n tn ic m ou n t

a . F le x ib le o r ie n ta ti on

b . C o ne c om p re ss io n

3 . Is oc en tn ic m o un t

a . In de pe nd en t ja ws

b . D yn am ic w ed ge s

c . M u lt i- le a f c o ll im a to rs

d .

D y n a m i c t re a t m e n t

B . C o m p u ta ti on a l c a pa b ili ti es

1 . D im e ns io ns (tw o o r th re e)

2 . In ho mo ge ne ity c orre ctio ns

3 , O p ti m iz a tio n

M ay, 19 88 {149}a d i o G r a p h i C s

5 6 1


6/15

U)

4-

C

a

4-

U)

C

0

C )

T a b le I X

C on s tra in ts in C ho o s in g T re a tm en t S etu p II

G eo me tric al B ea m

Al lgnm en t S y s t e m s

A . N on is o c e n tn ic m ou nt

a . L ig ht lo ca lize r a nd co ne s

b . Back pointer

C.

P in a n d a mc

d . B rid ge s

e . M o ld s a n d c a s ts

B . Is oc en tn ic u n its a n d s im u la to rs

a . B ea m d efin in g lig ht b ea m

b . O p tic al d is ta n ce in d ic ato rs

c . W all a nd c eilin g la se rs

d . O p tic al b ac k p oin te r

C o m b in in g B e am s

F ig ure 2

___%

A s in g le be am on th e le ft co m pa red to op po s in g 4 M V b eam s o n the

n igh t, d em ons tra te s th e b as ic p rinc ip le o f a ch iev in g a u n ifo rm do se b y

co m bin ing be am s w ith e qu a l an d op po s ite do se gra d ien ts .

3 M a tch ing fie lds

=

th e tec hn iq ue o f po s ition in g a d jac en t fie lds so a s to ac h ieve as ne ar ly un ifo rm a d o se a s po ss ib le .

T rea tm en t p lann ing R oz enf { 149} ld

56 2 R a d i o G r a p h i c s {149} ay , 1 98 8 {149}o lu m e 8 , N u m be r 3

S om e co ns tra in ts in c ho os ing th e o p tim um

trea tm en t va ria b les d ep end m ore o n th e p a-

tien t tha n on th e tre a tm en t un it. O bs truc ting

bo dy pa rts , s uch a s the sh ou ld e rs , m a y lea d to

the re je c tion o f w ha t o th e rw ise w ou ld ha ve

be en a n ide a l p lan . S o m e tim es th e p ro b lem of

m a tch in g fie ld s3 is e xa ce rb a ted w h en tu m or o r

an es pe c ia lly s ens itive h ea lthy o rga n is fou nd

to b e pre sen t a t th e p ro po se d m atch lin e .

If c r it ica l a lig nm e n t is co ns id e red esp ec ia l-

ly im porta n t to th e im p le m en ta tio n o f a p ro -

po sed p la n , th en o ne or m ore o f th e typ ic a l

be am a lign m en t sys te m s lis te d in T ab le IX

sho u ld be a va ila b le . M a ny o f th ese a re s ta n -

da nd equ ipm e n t o n com m erc ia l trea tm en t

machines.

It w ill g en e ra lly be fou nd tha t e ve n w ith

th e m o st s oph is tica ted tre a tm e n t m a ch in es ,

s a tis fac to ry re su lts w ill n o t be ach ie ve d u n less

m o re th an o ne b ea m is d ire c ted tow ard a

d ee p s ea te d le s ion . T h e o p tim um p la cem en t

o f th es e be am s c an be co ns id e red as th e

a rt o f ra d io the rap y . N o t on ly m u st th e con -

s tn a in ts lis te d e a rlie r a nd th e loca tio n o f th e

ta rg e t vo lu m e in re la tion to v ita l s tru c tu res b e

co n s id e red , b u t th e re su lt o f c o m b in in g b e a m s

in d iffe ren t w ay s m ust be ke p t in m in d in o rd e r

to a rriv e a t a n o p tim um trea tm en t p lan . T h e

ne x t se rie s o f F igu re s , sho w in g th e e ffe c t o f

co m b in ing b eam s in d iffe ren t w a ys , m a y be

co n s id e re d a sh o rt co u rse in co m p o s itio n in

th e a rt o f ra d io th e ra p y .

A s ing le be am o n the le ft o f F ig u re 2 co rn -

pa re d w ith op po s ing 4 M V b ea m s on th e m ig h t,

d e m o n stra te s th e b as ic p r in c ip le o f a ch ie v in g

a u n ifo rm d os e by co m b in ing be am s. A ra the r

u n ifo rm do se is f o un d in th e ce n tra l re g ion o n

th e n ig h t, w h ere th e do se co n tribu tion s from

th e o pp os ing bea m s fa ll o ff, a pp ro x im a te ly in

a lin ea r fa sh ion , in o pp os ite d ire c tio ns . T he

d ose is n o t u n ifo rm in the en tire o ve rlap reg ion ,

b eca us e th e d os e from ea ch be am d oe s n o t

fa ll o ff lin ea rly o ven the en tire reg io n .

If t w o b ea m s a re d ire c ted a t a n an g le to

o ne a no th e r fro m the sa m e s ide , as on th e le ft

o f F igu re 3 , th e is od ose lines in the re g ion o f

the o ve rlap a re s tra igh t an d fa ll o ff line a rly

w ith in c re as ing de p th ap prox im a te ly the sam e

as w ou ld th e isod os e lin es o f a s ing le fie ld d i-

re c te d d o w n w a rd . A h o t sp o t, o f

12 0% in th is

cas e , u su a lly ap pe ars a t th e ape x o f the ove n-

la p re g io n .

A re g ion o f u n ifo rm d ose can be

ge ne ra ted b y add in g a th ird fie ld fro m b e low

w ith an o pp os ing d ose gra d ien t, a s in the pa t-

te rn s ho w n on th e rig h t o f th is F ig u re .

F ig ure 3

T w o b ea m s d irec te d a t an a ng le to e ach o the r fro m the sa m e s ide

y ie ld isod os e lin es in th e re g ion o f ov e rlap tha t a re s tra ig h t an d fa ll o ff

line a rly (le ft). T h en a reg io n o f un ifo rm do se ca n b e g en era te d b y a dd -

in g a th ird fie ld fro m b e low (n ig h t).


7/15

R oz enfe id


V o lu me

8 , N um b er 3 {149}ay , 1 98 8 {149}a d i o G r a p h i c s

5 6 3

F ig u re 2

N B . N u m b ers o n iso do se lin es

=

o f do se d e live re d re la tive to th a t d e liv e re d a t a sp ec ifie d p o in t. S e e do se

sp ec ifica tio ns . pa g e 5 7 0 .

0

0

B

a .

3

3

Ia

0

a

B

(0


8/15


9/15

>

C )

0

-J

w

U-

0

Ui

w

0

LU

L I

>

1 )

C. ,

4

0

0

0)

0

LU

(9

0

LU

V o lu m e 8 , N um b er 3

{149}

a y , 1 988

{149}

adloGr aphics

R oz enfe ld T rea tm en t p la nn in g

0

0

B

a.

3

3

Ia

F ig ure 5

A co m b ina tio n o f s ta tio na ry a

w ed ge d fie ld s , o n the n igh t,

y ie lds a 1 0% v aria tio n in d ose

in th e ove rla p reg io n . T he

w e dg ed fie ld s , o n the le ft, ea ch

a rce d th rou gh 9 0 {17 6}ie ld s a

m o re u nifo rm d is tr ib utio n.

(C urve d a rro w s in c en te r o f fig -

u re sh ow a rcs th ro ug h w hic h

th e w ed ge d b ea m s m ove .)

5 6 5


10/15

T rea tm en t p lann ing R oz enf { 149} ld

56 6

R a d i o G r a p h i c s

{149}a y , 1 9 8 8 {149}

o lum e 8 , N um b er 3

U)

E

a

S

C

C

.0

E

0

C )

F ig ure 6

A co m ple te no ta tio n do es no t y ie ld a s u n ifo rm a d is tr ib u tion as th a t p rod uc ed by th e

w e dg ed a rcs fo r th is o ff-c en te r ta rg e t vo lum e. T he s ca llope d sha pe o f th e c u rve s in th e

lo w d o se reg io n is

d ue to a ppro x im ations in the com pu te r p ro g ra m .

A n o th e r w a y to tre a t th is re g io n w ith a

v ie w to ach ie v ing a u n ifo rm d ose d is tr ib u tio n is

to use a n in fin ite nu m b er o f op po s in g p a ins o f

p o rta ls p ro duc ed by a 3 60 {17 6 }o ta tio n o f the

s o u rc e d u rin g th e tre a tm e n t. T h e re s u lt, a s

s h o w n in F ig u re 6,

is no t a s u n ifo rm as tha t p ro -

d uce d b y th e w ed ge d arcs . T h e re aso n fo r th is

is th a t the fie ld s from b e low a re a ttenu a te d by

a g rea te n th ick nes s o f tis sue an d do no t co rn -

pe ns a te fo r th e op pos in g fie lds fro m ab ov e

tha t ex pe rie nce little a ttenu a tion b e fo re

rea ch ing th e isoc en te r. It sh ou ld be no te d th a t

th e d o s im e try sy s te m u se d to g e n e ra te th e se

cu rve s , a lo n g w ith m o st o th e r d o s im e try s ys-

te m s, a p p ro x im a te s a c o m ple te n o ta tio n w ith

a fin ite nu m b er o f fix ed be am s . T he su m m ation

o f do ses fro m the se a d jace n t fie ld s cau se s the

sca llo ped sh ap e o f the cu rve s in th e low do se

reg ion . T he a c tua l do se d is tribu tio n due to th e

n o ta tion o f the so u rce w ou ld , o f c ou rse , b e

q u ite sm o o th . W e h ave no t bo th e re d to

sm oo th o u t th is a rtifac t c aus ed b y th e m e th od

o f a p p ro x im a ti on .

W ith a ll op pos in g p a ins ex pe rien c ing e qu a l

a tte nua tio n , a 3o 0 {17 6 }o ta tio n abo u t th e c en te r

o f th e c on to u r, as in F igu re 7 , sh ou ld y ie ld a

un ifo rm fie ld . T h e d os e is qu ite u n ifo rm in the

reg io n o f ove rla p o f a ll th e fie ld s . N o te , h ow ev -

e n , th a t the sh ape o f th e h igh do se re g ion is a n

e llip se w ith its lo n g a x is in th e d ire c tio n o f th e

sh o rt ax is o f the co n to u r. T h is e ffe c t is d ue to

th e d iffe re n ce in a tte n u a tio n o f the be am s

th ro ug h the sh ort a nd lo ng d im en s ion s o f the

pa tien t. If it is ne ces sa ry to ac h ieve a h igh

d o se re g io n in th e sh a p e o f a n e llip se w h os e

lo ng ax is is in th e d ire c tio n o f th e lo ng ax is o f

th e co n to u r, th e n o p p o s in g a rc s sh o u ld b e

use d as in F igu re 8 .


11/15

C O M P L E T E R O T A T IO N , O N C E N T E R

0

0

B

a .

3

3

Ia

0

a

B

0

1 2 0 {1 7 6 }A R C S , 4 M V

R oz enfe ld T rea tm en t p lann ing

V o lum e 8 , N u m be r 3

{149}

ay , 1 98 8

{149}

adloGr aphics

5 6 7

F ig ure 7

A com ple te ro ta tio n ab ou t the cen te r o f th e con tou r y ie ld s a un ifon m d is tr ibu tion in the m e-

g io n o f ov e rlap o f a ll the fie ld s . T h e sha pe o f the h ig h d ose reg io n is a n e llipse w ith its lon g

ax is in the d irec tio n o f the sho rt ax is o f the con to u r.

F ig ur e 8

A h igh d os e re g ion in the sh ap e o f an e llipse w hos e lon g a x is is in th e d ire c tion o f the lon g

a x is o f the co n tou r c an b e ach ie ve d by u s ing op po s in g a rcs (1 2 0 {1 76 }rc s in th is c ase ).


12/15

U)

E

a

S

C

C

.0

E

0

C )

M V

O P P O S IN G F IE L D S

Is M V W E D G E D

R E V E R S E D

4 M e V

\

5 6 8 R a d i o G r a p h i c s {149}a y , 1 98 8 {149}o lum e 8 , N u m be r 3

T rea tm en t p la nn in g

L ,

F ig ure 9

H e re , a n o ff-ce n te r re g ion a long th e lo ng ax is o f a con tou r is in m ad i-

a te d w ith o pp os ing 4 M V x-ray be am s (u pp er) a nd o pp os ing , w e dg ed

1

8 M V x-ray be am s (lo w er). T he d is tribu tio n u s in g 4 M V ca nno t b e

im p ro ve d u po n b y us in g w ed ge s . A dd in g w ed ge s to th e 18 M V

b eam s, to a c t a t tis sue co m pens a ton s , p ro du ces a 5% va ria tio n

th rou gh the e ntire re gion .

R oz enfe ld

A no th e r com m on m od e o f trea tm en t us -

in g op po s ing fie ld s is sh ow n in F igu re 9 . It co rn -

pa re s the us e o f 4 M V an d 1 8 M V x ra ys to irm a -

d ia te a n o ff-c en te r reg io n a lon g the lo ng ax is

o f the co n tou r. T h e d is tr ib u tio n us ing 4 M V can -

n o t b e im p ro ve d up on by u s in g w ed ge s , s inc e

th ey w o u ld inc reas e the a lrea dy h ig h m e d ia l

e n tran ce dos es . T h e p rob lem is in su ffic ien t

p en e tra tio n w h ich c an b e s o lved b y incre as -

ing the e ne rgy to a t le as t 18 M V . T h en ad d ing

w ed ge s to ac t as tissu e co m p ens a to rs doe s

im prov e th e d os e d is tr ibu tion , p ro du c ing a

5% varia tion th roug ho u t th e en tire reg io n .

M o st o f th e co m m o n m e tho ds fo r c om b in -

in g be am s hav e b een e xam in ed . T he n ex t few

ex am p le s , a lth ou gh no t as co m m on , a re p re -

se n ted to sho w som e n ew o r u nu sua l se tu ps

tha t m igh t be e nco un te red . F igu re 10 is p re -

se n ted to sho w a s itua tio n in w h ich a u n ifo rm

//

F ig ure 1 0

A u nifo rm d is tr ib utio n is a ch ie ve d w ith rev e rse d

w ed ge s w he re the ne ed fo r tissu e co m pe ns a tio n be -

co m e s th e o ve rrid in g fac to r.


13/15

R oz en f o ld


V o lum e 8 , N um ber 3 {149}ay , 1 98 8 {149}adioGr aphics

5 6 9

F ig u re 1 1

U sing an op tim iza tion p ro g ra m , th is irreg u la r ta rge t vo lum e is a lm ost

e xa ctly co ve re d

b y the 9 0% is od ose line a nd the do se a t th e c en te r,

m a rked b y the X , is lim ited to 5 0% .

13

0

0

B

a .

3

3

Ia

w

0

a

B

0

d is tr ib u tio n is ach ieve d w ith an g led bea m s.

H e re , the ne ed fo r tissu e c om p en sa tion ov en -

ride s th e n ee d to c om p en sa te fo r the ex pec t-

e d ho t s po t a t the ap ex o f th e o ve rlap reg ion .

T h us , th e w ed ge s m us t be rev e rse d from the ir

u su al p la ce me nt.

F in a lly , F ig u re 1 1 s h ow s an ex am p le o f

w h a t c an be ac h ieve d by op tim iza tion p ro -

g ram s . In th is ca se , the ta rge t vo lum e is a lm ost

e x a c tly co v e re d b y th e 9 0% is od ose lin e a nd

th e d os e a t th e ce n te r, m a rked by the X , w as

lim ite d to 5 0% . T h is 18 fie ld p la n w ith tw o iso -

c en te rs and fie ld s izes co n fo rm ing to the

s hap e o f th e ta rge t vo lu m e can b e e xec u ted

by s om e m o de rn co m pu te r c on tro lled trea t-

m e n t m ac h ine s w ith on ly on e p a tie n t se tup .

W ork is u nd erw ay a t som e ce n te rs to d ev e lop

s che m e s fo r op tim iz ing trea tm en ts w h ich tak e

in to a cco un t th e va ria tio n in th e s ize a nd

s ha pe o f the ta rg e t vo lu m e in th ree d im e n-

s io ns . A lth ou gh th e th ree d im e ns io na l ta rge t

v o lum e ha s an irreg u la r s ha pe in m o st c as es ,

n ad io th e ra p is ts fre qu en tly d raw the ta rge t

a re a as a c irc le , squ a re , o n rec ta ng le , s in ce

th ose a re the sh ap es o f the is od ose c u rve s us u -

a lly ob ta in ed by s ta nd ard p la ns . T he us e o f o p -

tim iz a tio n w ou ld a llow the ra d io th e rap is t to

d e fin e th e ta rge t v o lum e m o re p re c ise ly ,

b ase d o n the c ha ra c te ris tic s o f th e tu m or m a th -

e n th an o n the ch arac te ris tics o f the tre a tm e n t

m ac h ine .


14/15


15/15

R oz enf { 149} ld T rea tm en t p lann ing

V o lum e 8 , N um ber 3 {149} ay , 198 8 {149}adioGr aphics

5 7 1

S u m m a r y

In th is firs t o f a se ries o f a rtic les o n R ad ia -

tion T rea tm en t P la nn in g bas ed on th e B a s ic

P h ys ics S ym p os ium o f the A m e rica n A ss oc ia -

tion o f P hys ic is ts in M e d ic ine a t the 73 rd A nn ua l

m ee ting o f the R S N A , an a tte m p t ha s be en

m ad e to p rov id e a b ro ad o ve rv ie w o f th e p ro -

c e s s o f d e s ig n in g a n o p tim a l ra d ia tio n th e ra p y

re g im en . T he essen tia ls o f trea tm e n t p lan n in g

ha ve b ee n ide n tified a nd e sse n tia l te rm s h ave

be en de fine d . V a ria b les to be se le c ted h ave

be en ide n tified an d co ns tra in ts in ch oo s ing

trea tm e n t p la ns ha ve b ee n n o te d . T he e ffe c t

o f com b in ing m u ltip le be am s to a ch iev e the

m ost ad van tag eo us d is tr ibu tion o f rad ia tio n

do se w ith in the pa tien t ha s b ee n d isc us sed

and the v ita l im porta nce o f app rop ria te q ua li-

ty co n tro l h as be en em pha s ize d . F u tu re a rti-

de s w ill c ons id e r sp ec ific as pe c ts o f th is d is c i-

p line in d e ta il.

16_06_2014_tps historical overview.pdf

Documents