linear accelerator drift tube
DESCRIPTION
Linear Accelerator Drift Tube. Positive Ion Cyclotron Operation. CS-15 Positive Ion Cyclotron Washington University School of Medicine. Target. Targets for Cyclotron. 1. Metals : 111 Cd(p,n) 111 In( 111 In-DTPA) 201 Hg(d,2n) 201 Tl( 201 Tl-chloride) 68 Zn(p,2n) 67 Ga( 67 Ga-citrate) - PowerPoint PPT PresentationTRANSCRIPT
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Linear Accelerator Drift Tube
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Positive Ion Cyclotron Operation
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CS-15 Positive Ion CyclotronWashington University School of
Medicine
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Target
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Targets for Cyclotron
1. Metals:111Cd(p,n)111In (111In-DTPA)201Hg(d,2n)201Tl (201Tl-chloride)
68Zn(p,2n)67Ga (67Ga-citrate)
2. Gases:14N(d,n)15O (H2
15O, 15O2)14N(p,)11C (11C-acetate, 11C-
palmitate, 11C- glucose)
3. Liquids:16O(p,)13N (13N-ammonia)18O(p,n)18F (18F-FDG)
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Simple X-ray Tube
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• Fast neutrons (E of 1.5 MeV) have a low probability of interaction with other nuclei.• They are thermalized or slowed down (0.025 eV) to interact with other nuclei.• Moderators (low MW materials like heavy water, beryllium or graphite) are distributedin spaces between fuel rods
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University of Missouri Research Reactor (MURR)Columbia, MO
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Nuclear Fission
235U144 + n 236U144
236U144144Ba88 + 89Kr53 + 3n
99Mo42 + 135Sn50+ 2n
• 236U unstable - undergoes fission immediately
• wide range of fission products - usually 1/3 and 2/3 split of the mass number
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Fission products useful in nuclear medicine include:99Mo, 131I, 133Xe, 137Cs and 90Sr
Mo-99 I-131
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Reactor-Produced Radionuclides:Thermal Neutron Reactions
• (n, reaction: formed by reactions between targets and thermalized neutrons
YAz + n Y+1Az +
A=target; A=isotope producedsame atomic number, different mass
• (n, reaction– not carrier-free, since target and product are same– radioisotopic purity can be high if cross section is
sufficiently large (e.g. 176Lu(n,)177Lu)
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Reactor-Produced Radionuclides:Thermal Neutron Reactions, cont’d
• (n, p reaction: formed by reactions between targets and thermalized neutrons
YAz + n YBz-1 + p
A=target; B=isotope produceddifferent atomic number, same mass
• (n, p reaction– carrier-free, since target and product are different– example: 64Zn(n,p)64Cu
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Fisson/Reactor Products Cyclotron Products
• Generally decay by - emission because of excess neutrons
• Not many are useful for diagnostic imaging, but several are useful for radiotherapy
• Generally decay by + emission or electron capture because of excess protons
• Many are useful for diagnostic imaging
(gamma scintigraphy or positron emission tomography)
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Photoelectric Effect:The energy of an incoming gamma ray is completely absorbed by the atom, and the energy absorbed is used to eject an electron from the atom.
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Pair Production:The energy of an incoming gamma ray (>1.02 MeV) is completely absorbed by the nucleus, and the energy absorbed is used to eject an electron and a positron from the atom.
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Alpen, E.L. (1998) Radiation Biophysics Academic Press, San Diego, p. 87
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Alpen, E.L. (1998) Radiation Biophysics Academic Press, San Diego, p. 105
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Hall, E.J. (1994) Radiobiology for the Radiologist J.B. Lippincott Company, Philadelphia, p. 154
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Latorre Travis, E. (1989) Primer of Medical Radiobiology Year Book Medical Publishers, Inc.,Chicago, p. 92
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LET
RB
E
Hall, E.J. (1994) Radiobiology for the Radiologist J.B. Lippincott Company, Philadelphia, p. 160
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Hall, E.J. (1994) Radiobiology for the Radiologist J.B. Lippincott Company, Philadelphia, p. 160
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Alp
en, E
.L. (
1998
) R
adia
tion
Bio
phys
ics
Aca
dem
ic P
ress
, San
Die
go, p
. 52