726
M. Dohlus et al.
Cyclotrons have to produce 10–20 times larger currents. In fact the machine
output energy is fixed and absorbers of variable thickness have to be inserted in
a 15–20 m long Energy Selection System which reduces the energy to the treatment
requirements. In the process of beam degrading, down to the minimal required
energies, and re-shaping a large fraction of particles is lost.
As mentioned above, carbon and other light ions have a larger RBE with respect
to X-rays and protons. The physical and radiobiological arguments of this can be
summarized as follows. In a cell, a carbon ion leaves about 24 times more energy
than a proton having the same range. This produces—very close to the particle
track—a dense column of ionization, especially near the Bragg-peak region of the
track, causing many ‘Double Strand Breaks’ and ‘Multiple Damaged Sites’, when
crossing the DNA contained in the cell nucleus. In this way, the effects on the cell
are qualitatively different from the ones produced by sparsely ionizing radiations,
such as X-rays and protons. In addition, the biological effect of carbon ions is less
dependent of the oxygenation of the target and therefore their use is indicated against
hypoxic and otherwise radio-resistant tumours.
Due to the much more complex DNA damage, the RBE values of the light ions at
the Bragg peak can be about three times larger than the one for X-rays and protons.
In the slowing down of an ion in tissue this effect becomes important when LET
becomes larger than about 20 keV/μm. For carbon ions this happens in the last
5 cm of their range in water.
11.3.2.3 Cyclotrons and Synchrotrons in Hadron Therapy
Proton Therapy
The first facilities that treated patients with protons and ions were based on existing
accelerators built for fundamental research in nuclear and particle physics: LBL at
Berkeley (USA); GWI in Uppsala (Sweden); JINR in Dubna (Russia); PMRC-1 in
Tsukuba (Japan); UCL, in Louvain La Neuve (Belgium); MPRI-1 in Indiana (USA)
60 MeV protons at Chiba (Japan). Moreover pions where used at TRIUMPH and
PSI (SIN at that time) in the periods 1979–1994 and 1980–1993, respectively. The
clinical results have shown that pions are not superior to protons and light ions
neither to obtain conformal dose volumes nor in the treatment of radioresistant
tumours.
The proton therapy facilities running in the world are listed in Table 11.7. The
data are extracted from PTCOG online database [90] and the data on the number of
patients are updated to December 2015.
Table 11.7 includes three centres producing 60–70 MeV proton beams which
are exclusively used for the treatment of eye tumours and malformations. The most
recent facilities in the table are hospital-based, in the sense that they feature an
accelerator built specifically for medical purposes and have more treatment rooms so
that several hundred of patients can be treated every year. The companies which have
built the accelerators and the high-tech parts of these centres are: Optivus (USA),
M. Dohlus et al.
Cyclotrons have to produce 10–20 times larger currents. In fact the machine
output energy is fixed and absorbers of variable thickness have to be inserted in
a 15–20 m long Energy Selection System which reduces the energy to the treatment
requirements. In the process of beam degrading, down to the minimal required
energies, and re-shaping a large fraction of particles is lost.
As mentioned above, carbon and other light ions have a larger RBE with respect
to X-rays and protons. The physical and radiobiological arguments of this can be
summarized as follows. In a cell, a carbon ion leaves about 24 times more energy
than a proton having the same range. This produces—very close to the particle
track—a dense column of ionization, especially near the Bragg-peak region of the
track, causing many ‘Double Strand Breaks’ and ‘Multiple Damaged Sites’, when
crossing the DNA contained in the cell nucleus. In this way, the effects on the cell
are qualitatively different from the ones produced by sparsely ionizing radiations,
such as X-rays and protons. In addition, the biological effect of carbon ions is less
dependent of the oxygenation of the target and therefore their use is indicated against
hypoxic and otherwise radio-resistant tumours.
Due to the much more complex DNA damage, the RBE values of the light ions at
the Bragg peak can be about three times larger than the one for X-rays and protons.
In the slowing down of an ion in tissue this effect becomes important when LET
becomes larger than about 20 keV/μm. For carbon ions this happens in the last
5 cm of their range in water.
11.3.2.3 Cyclotrons and Synchrotrons in Hadron Therapy
Proton Therapy
The first facilities that treated patients with protons and ions were based on existing
accelerators built for fundamental research in nuclear and particle physics: LBL at
Berkeley (USA); GWI in Uppsala (Sweden); JINR in Dubna (Russia); PMRC-1 in
Tsukuba (Japan); UCL, in Louvain La Neuve (Belgium); MPRI-1 in Indiana (USA)
60 MeV protons at Chiba (Japan). Moreover pions where used at TRIUMPH and
PSI (SIN at that time) in the periods 1979–1994 and 1980–1993, respectively. The
clinical results have shown that pions are not superior to protons and light ions
neither to obtain conformal dose volumes nor in the treatment of radioresistant
tumours.
The proton therapy facilities running in the world are listed in Table 11.7. The
data are extracted from PTCOG online database [90] and the data on the number of
patients are updated to December 2015.
Table 11.7 includes three centres producing 60–70 MeV proton beams which
are exclusively used for the treatment of eye tumours and malformations. The most
recent facilities in the table are hospital-based, in the sense that they feature an
accelerator built specifically for medical purposes and have more treatment rooms so
that several hundred of patients can be treated every year. The companies which have
built the accelerators and the high-tech parts of these centres are: Optivus (USA),