Pion radiotherapy uses subatomic particles called pions that are produced when a target is bombarded with protons. Pions are selected by momentum and lose energy as they travel through tissue until they are captured by a tumor nucleus. This makes the nucleus unstable and it breaks apart violently, damaging nearby cells with fragments over a small radius. Although pion therapy centers opened in the past, results were no better than X-ray therapy and it is now only used for clinical research.

2. PION RADIOTHERAPY
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3. Outline
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4.  Pion or pi meson is a subatomic particle consists of one quark
and one anti-quark. They hold the nucleus together
 They have small rest mass, zero baryon number ,short lifetimes,
and antiparticles.
 Decay
π⁺ –› μ⁺ + ν
π¯ –› μ¯ + ν͂
π° –› hν₁ + hν₂
Introduction
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5.  the energy of the bombarding particle & target material must be appropriate
 When the target is bombarded the pions are released nearly isotropitally
with different momenta.
 Pions of specific momenta may be selected by magnetic fields.
 Pions lose energy in flight through tissue
Mechanism of Pion Production
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7.  When the π¯ reaches the tumour it has slowed down so much
that a nucleus captures it.
 The nucleus is now unstable and breaks up violently into
smaller fragments.
 These fragments damage surrounding cells within a small
radius
Negative pion in Radiotherapy
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8.  As the pion comes to rest, it is captured by the nucleus.
 Unstable nucleus explodes, producing short range, heavily ionizing
nuclear fragments and alpha particles, as well as neutrons, protons,
y-rays and pi-mesic X-rays
 30 MeV of the total rest energy (139 MeV) of the pi-meson appears in
the form of heavy ions, alpha particles and protons.
Radiated particle & Radiation type
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9.  Protons with 400-800 MeV energy produced in cyclotron or
linac are used for pion beam production for RT.
 100 MeV pions are of interest in radiation therapy
 Pions have low dose rate
Energy range & Dose rate
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10.  First pion centre at Los Alamos, New Mexico closed in 1981,
Second in Switzerland & Another has opened in Canada
 But this is only for clinical research, currently
 Early results showed no better or worse than conventional Xray
therapy
Applications & Popularity
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