Biomedical Engineering Reference
In-Depth Information
1.
R
ADIATION IN THE
T
REATMENT OF
C
ANCER
Introduction ............................................................................................1
Types of Radiation Used in the Treatment of Cancer.............................2
Why Does Radiation Work?....................................................................3
A Single Treatment Beam .......................................................................4
Multiple Treatment Beams......................................................................6
The Volume Effect...................................................................................7
Intensity-Modulated Radiation Therapy (IMRT)...................................8
Treatment Design and Delivery..............................................................9
Tumor and normal tissue delineation .......................................................9
Dose prescription ......................................................................................9
Treatment planning and evaluation.........................................................10
Dose delivery...........................................................................................10
Safety.......................................................................................................10
Summary ...............................................................................................11
I
NTRODUCTION
The prognosis for someone diagnosed with cancer is not as dire as is
commonly believed. Many cancers, such as early stage cancer of
the larynx, childhood leukemia, and Hodgkin's disease, are highly
curable. Unfortunately, others, such as pancreatic cancer, have a poor
prognosis. The curability of most cancers lies somewhere between
these extremes.
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Early in its development, a malignant tumor is generally well
localized. As most cancers develop, they tend to spread to neigh-
boring lymph nodes and, as metastases, to noncontiguous organs.
When the disease is localized, a local treatment such as surgical
excision or radiation therapy is indicated. When the tumor is in-
accessible or is intimately entwined with a vital anatomic structure,
