Theory, Design and Tests on a Prototype Module of a Compact ...

2 1. INTRODUCTION TO THE HADRONTHERAPY
may be the only effective treatment, sometimes in conjunction with
surgery.
It may not be possible to irradiate some lesions with these conventional
beams or to remove them surgically because of the proximity of
critical tissues <strong>and</strong> proton therapy may be the only possible form of
treatment.
If neutron or proton beams are not available the alternatives are
very expensive chronic medical care or treatment at overseas centers.
Radiation therapy machines are expensive, high technology equipment,
but the advantages are
• A sterile environment is not required.
• Few people are involved in patient treatment, which does not
necessarily require the daily presence of a Radiation Oncologist
or any other clinician.
• Most patients are treated as out-patients <strong>and</strong> therefore do not
occupy scarce <strong>and</strong> expensive hospital beds.
• Irradiation is not traumatic for patients, who are not anaesthetized
<strong>and</strong> usually do not get sick from the treatment.
Radiation therapy is therefore cost-effective <strong>and</strong> often cheaper than the
alternatives of surgery, chemotherapy <strong>and</strong> chronic health care.
Neutrons <strong>and</strong> protons are both nuclear particles of approximately
the same mass. However, the fact that neutrons are uncharged <strong>and</strong>
protons are charged particles results in their having vastly different
physical properties <strong>and</strong> biological effects. Using conventional photon
radiation as the st<strong>and</strong>ard, the dose distributions of fast neutrons are
very similar, but their biological effects offer advantages for the treatment
of certain types of tumours, while the advantages of protons lie
in their physical dose distributions.
Many large tumours have central cores, which lack oxygen because
the blood supply has been reduced by the proliferating tumour cells.
Other tumours are slow-growing <strong>and</strong> the cells spend a relatively short
time in the dividing phase of the cell cycle, where they are most sensitive
to radiation. These tumours are resistant to conventional photon
radiation but are far less resistant to neutron irradiation, which therefore
in principle has a better chance of effecting a cure. Examples of
tumours that are effectively treated by neutrons include salivary gl<strong>and</strong>
tumours, large breast tumours <strong>and</strong> certain tumours of other soft tissues.
However, because radiation causes damage to the normal tissue
in front of a deep-seated tumour, a so-called isocentric beam delivery
system (one which rotates about the patient) is essential so that the patient
can be irradiated from several different angles. This concentrates
the dose at the tumour <strong>and</strong> limits the dose to normal tissue.
High energy protons are particularly suitable for treating cancer
or other (benign) abnormalities near sensitive structures such as the
optic nerve, spinal cord, kidneys, etc., where other forms of radiation