RADIOTHERAPY
a c t i v e
s o u r c e s
p r o d u c e
i o n i z i n g
r a d i a -
t i o n , w h i c h d e s t r o y s o r s l o w s d o w n t h e
d e v e l o p m e n t o f a b n o r m a l c e l l s . N o r m a l
c e l l s s h o u l d s u f f e r l i t t l e o r n o d a m a g e i n
t h e l o n g t e r m , b u t s h o r t - t e r m
d a m a g e i s
a s i d e e f f e c t o f r a d i o t h e r a p y .
WHY IS IT DONE
R a d i o t h e r a p y m a y b e u s e d o n i t s o w n i n
a n a t t e m p t t o d e s t r o y a l l t h e a b n o r m a l
c e l l s i n v a r i o u s t y p e s o f c a n c e r , s u c h a s
s q u a m o u s c e ll c a rc in o m a
( a t y p e o f s k i n
c a n c e r ) a n d
H o d g k in ’s d is e a s e
( a c a n c e r
o f l y m p h o i d t i s s u e ) . I t m a y a l s o b e u s e d
i n c o n j u n c t i o n w i t h o t h e r c a n c e r t r e a t -
m e n t s . F o r e x a m p l e , s u r g i c a l e x c i s i o n o f
a
c a n c e r o u s
t u m o u r
i s
o f t e n f o l l o w e d
b y r a d i o t h e r a p y t o d e s t r o y a n y r e m
a i n -
i n g
t u m o u r
c e l l s ,
s u c h
a s
i n
t h e
t r e a t m e n t o f
b re a s t c a n c e r.
R a d i o t h e r a p y
m a y
a l s o
b e
u s e d
t o
r e l i e v e t h e s y m p t o m s o f a c a n c e r t h a t
i s t o o a d v a n c e d t o b e c u r e d . A n e x a m
-
p l e
o f
s u c h
p a llia t iv e
t r e a t m e n t
i s
r a d i o t h e r a p y
t o
r e d u c e
t h e
s i z e
o f a
b ra in t u m o u r
i n o r d e r t o
r e l i e v e h e a d -
a c h e s a n d p a r a l y s i s .
I f t h e b e n e f i t s o f d e s t r o y i n g d i s e a s e d
t i s s u e o u t w e i g h t h e r i s k s o f d a m a g e t o
h e a l t h y t i s s u e , r a d i o t h e r a p y m a y b e u s e d
t o
t r e a t
n o n c a n c e r o u s
d i s e a s e s ;
f o r
e x a m p l e , p a r t o f a n o v e r a c t i v e t h y r o i d
g l a n d
( s e e
t h y ro to x ic o s is )
m a y
b e
d e s t r o y e d u s i n g r a d i o a c t i v e i o d i n e .
HOW IT IS DONE
R a d i o t h e r a p y i s u s u a l l y p e r f o r m e d
o n
a n
o u t p a t i e n t
b a s i s .
X -ra y s
( o r
s o m
e -
t i m e s
e l e c t r o n s ) ,
w h i c h a r e
p r o d u c e d
b y a m
a c h i n e c a l l e d a l i n e a r a c c e l e r a t o r ,
a r e
a i m e d a t
t h e
t u m o u r
f r o m
m a n y
d i r e c t i o n s .
A l t e r n a t i v e l y ,
a
s o u r c e
o f
r a d i a t i o n ,
i n t h e f o r m
o f t i n y p e l l e t s ,
i s
i n s e r t e d
i n t o
t h e
t u m o u r
t h r o u g h
a
h o l l o w
n e e d l e
( s e e
in t e rs t it ia l ra d io -
th e ra p y )
o r
i n t o
a
b o d y
c a v i t y
( s e e
in t ra c a v ita ry t h e ra p y ).
T h e s e
t e c h n i q u e s
USE OF RADIOTHERAPY
Radiotherapy destroys cancer cells using
radiation. A linear accelerator is used for
external radiation (right). The position and
dose of radiation are carefully calculated to
minimize exposure of normal cells to the
radiation, allowing them to recover with
little or no long-term damage.
Internal radiation (below) involves
placing radioactive materials in the body,
directly into or around a cancer.
External radiation
The patient lies still on a table under the machine.
A radiographer operates the machine, which
sendsX-rays, in the predetermined directions
and amounts, through the diseased areas of the
patient’s body. The machine can be tilted to
irradiate the cancer from different angles (see
below, centre). The procedure causes no
discomfort, and usually lasts a few minutes, but
setting up the equipment may take 30 minutes.
INTERNAL RADIATION
Radiation source
Bladder
Radioactive
pellets
Prostate
gland
R
Use of radioactive pellets
Tiny radioactive pellets are inserted, via a hollow
needle, directly into the organ or tissue to be
treated (here, the prostate gland).
Rays from different directions
By aiming relatively low-energy rays coming
from many directions at a tumour, a large
enough dose ofradiation is achieved in
the locality ofthe tumour to destroy it
completely (see above).
Before
treatment
There is a
proliferation of
lymphoid tissue
in this lung
X-ray of a
patient with
Hodgkin’s
disease.
After
treatment
The invading
lymphoid
tissue has
diminished
following
radiotherapy.
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