CYCLOTRON Pawitra Masa-at 4937092 SIRS/M January 31, 2007
Basics of PET Tracer Production
Generates high-energy particles Generate PET radionuclide Generates TRACER
One of the earliest types of particle accelerators
Cyclotron are source of a large number of high-energy (MeV) range charged particle .
Accelerations proton to 11 MeV .
MINI trace (GE)
Accelerate protons to 9.6 MeV
PET trace (GE)
16.5 MeV negative ion cyclotron
Six target proton and deuteron
Physics of cyclotron
A device invented by E . O . Lawrence and M . S . Livingston at Berkeley in 1931
that is used to accelerate charged particles by means of a magnetic field .
A particle of mass (m ) and charge (q ) moving with a velocity ( v ) will interact with a magnetic field of strength ( B ) whose direction is perpendicular to the plane of its travel with force
The force of the magnetic field
The force of the electric field
Charged Particle in an EM Field
Centripetal force on particle in an orbit
The force of the magnetic field is perpendicular to the particle's direction, resulting in a circular path inside the cyclotron. Equating F with a centripetal force gives
Homogeneous magnetic field in which case,
Where then T (time) can be written as
RF oscillator frequency
For particle of constant mass , the frequency does not depend upon the radius of the particle’s orbit.
As the beam spirals out, its frequency does not decrease, and must continue to accelerate, as it travelling more distance in the same time.
As mentioned earlier, this is a constant frequency orbital accelerator,
but one in which the orbit radius increases. Frequency given by
Max KE achievable: ………… ..
Major Exterior Component
Major Interior Component
High vacuum (10 -6 , 10-8) needed to reduce interaction of accelerated particles with air molecules.
prevents the creation of other unwanted nuclides.
Electrical insulation of the DEEs.
All material needs to be compatible with level of vacuum .
Provide the source of ions (proton or deuteron) that that will be accelerated
Introduce the ion into magnetic field
The input to the ion source is 99.9995% pure hydrogen.
mounted in the centre of the cyclotron.
p+ e- e-
Ion source system (cont) Ion Source
Provide the magnetic field
Makes the ion travel in circular orbit
Keeps the beam of ions focused and compact.
Charged Particle in an EM Field
Radiofrequency System (RF)
Pulls the ions out of the ion source.
The RF oscillates about the two Des at high frequency and voltage.
Push and Pull particles around the cyclotron
Accelerates the ions to the specified energy prior to its bombardment.
RF System (cont) Flaps Fine tuning RF frequency Stem Supplying RF power to Dee’s
Electrode inside the cyclotron.
Pulse with fluctuating negative and positive charges.
to “push” and “pull” the ions through the circular acceleration.
DEEs Ion Source
Thin carbon foil placed at the extraction radius
Electron are tripped off Ion become Positron.
Remove the “-” e - in the case of F-18 production
No beam losses here.
Beam Extraction (cont) H - Ion source Creates the ion Orbits controlled by magnet field RF System Accelerates the ion Carbon foil H + Extraction System Changes polarity of ions 16.5 MeV p+ e- e- p+ e- e- p+ e- e-
Targets are located outside the cyclotron
The high energy particle beam of protons hit the nucleus (of the target material) & cause a nuclear reaction.
The target material can be a gas, liquid or solid.
Reactions with different particles need to accelerate different particles
Different reaction thresholds need to accelerate to different energies
Uses of Cyclotrons
Multi-particle, multi-energy cyclotrons:
very flexible, but
often positive ion cyclotrons
usually 2 types of particles (p and d) and
1 fixed energy for each particle
typical for negative ion cyclotrons
Advantage of Cyclotron
Produce atom has different charge.
High specific activity / short half-life.
For PET studying
Nuclide T 1/2 Production
Carbon-11 20.4 min 10 B(d,n) 11 C
Nitrogen-13 9.96 min 12 C(d,n) 13 N
Oxygen-15 2.05 min 14 N(d,n) 15 O
16 O(p,pn) 15 O
Fluorine-18 110 min 18 O(p,n) 18 F
Nuclide T 1/2
Cobalt-57 272 d marker for in-vitro kits.
Gallium-67 78 h tumour imaging & localization of infection