TY - CHAP
T1 - Neutron field measurements in a water filled head phantom
AU - Auterinen, Iiro
AU - Ember, P.
AU - Kaita, Karoliina
AU - Seren, Tom
PY - 1997
Y1 - 1997
N2 - In Boron Neutron Capture Therapy (BNCT) the selective
therapeutic dose is delivered by the neutron capture
reaction 10B (n, alfa) 6Li reaction. The neutron capture
crosssection of 10B is inversely proportional to the
neutron velocity, thus thermal neutrons are most likely
to cause the desired effect in the tissue. In epithermal
beam irradiations the epithermal neutrons slow down in
tissue through collisions, mainly with hydrogen, forming
a thermal neutron field. The boron capture dose
distribution can be calculated if both the boron and
thermal neutron distributions are known.
Experimental verification of treatment planning and beam
characterisation requires that the thermal field
intensity and distribution has to be measured in
phantoms. Neutron activation dosimetry is the best method
for accurate and quantitative determinations but it is
not so practical for field mapping.
Thermal neutron field mapping can be done using a
continuously operated detector. Such a detector can be
produced by using the reaction 6Li (n, alfa) 3H
(Q=4,78MeV). The shape of the neutron capture
cross-section of 6Li resembles that of 10B, so both the
boron capture dose and the detector signal depend on the
neutron spectrum the same way. The alfa and 3H particles
can be detected with a silicon PN-diode. Such a detector
was prepared using a PN junction diode with an aluminium
layer on the P type surface in close contact with natural
lithium (7,42% 6Li) containing epoxy. The measurements
were done in a water filled cubic phantom with PMMA walls
and a cylindrical extension, 20 cm in diameter and 20 cm
long, simulating a human head. The detector was moved
with a remote controlled 3D transport mechanism. The
measured and calculated thermal flux distributions were
in close agreement.
Activation detectors i.e. foils of diluted 197Au were
used to gain absolute quantitative information about the
neutron flux in the phantom. Five detectors were placed
into the phantom and the phantom was then exposed to
irradiation. The activities induced by the 197Au (n,
gamma) 198Au reaction were measured and the experimental
reaction rates calculated from the activities and the
irradiation history. The results were compared to the
calculated reaction rates.
AB - In Boron Neutron Capture Therapy (BNCT) the selective
therapeutic dose is delivered by the neutron capture
reaction 10B (n, alfa) 6Li reaction. The neutron capture
crosssection of 10B is inversely proportional to the
neutron velocity, thus thermal neutrons are most likely
to cause the desired effect in the tissue. In epithermal
beam irradiations the epithermal neutrons slow down in
tissue through collisions, mainly with hydrogen, forming
a thermal neutron field. The boron capture dose
distribution can be calculated if both the boron and
thermal neutron distributions are known.
Experimental verification of treatment planning and beam
characterisation requires that the thermal field
intensity and distribution has to be measured in
phantoms. Neutron activation dosimetry is the best method
for accurate and quantitative determinations but it is
not so practical for field mapping.
Thermal neutron field mapping can be done using a
continuously operated detector. Such a detector can be
produced by using the reaction 6Li (n, alfa) 3H
(Q=4,78MeV). The shape of the neutron capture
cross-section of 6Li resembles that of 10B, so both the
boron capture dose and the detector signal depend on the
neutron spectrum the same way. The alfa and 3H particles
can be detected with a silicon PN-diode. Such a detector
was prepared using a PN junction diode with an aluminium
layer on the P type surface in close contact with natural
lithium (7,42% 6Li) containing epoxy. The measurements
were done in a water filled cubic phantom with PMMA walls
and a cylindrical extension, 20 cm in diameter and 20 cm
long, simulating a human head. The detector was moved
with a remote controlled 3D transport mechanism. The
measured and calculated thermal flux distributions were
in close agreement.
Activation detectors i.e. foils of diluted 197Au were
used to gain absolute quantitative information about the
neutron flux in the phantom. Five detectors were placed
into the phantom and the phantom was then exposed to
irradiation. The activities induced by the 197Au (n,
gamma) 198Au reaction were measured and the experimental
reaction rates calculated from the activities and the
irradiation history. The results were compared to the
calculated reaction rates.
M3 - Conference abstract in proceedings
SN - 951-45-7639-X
T3 - University of Helsinki: Department of Physics. Report Series in Physics
BT - Proceedings of the XXXI Annual Conference of the Finnish Physical Society
A2 - Rauhala, Eero
A2 - Sainio, M.E.
PB - University of Helsinki
CY - Helsinki
T2 - XXXI Annual Conference of the Finnish Physical Society
Y2 - 13 March 1997 through 15 March 1997
ER -