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Figure 1 shows registered images of the original patient
image (a), phantom 1 (b), and phantom 2 (c). Tissue
density was more accurate in phantom 2, despite some
small holes not being filled with bone resin.
Conclusion
Two phantoms were created, one with a single material,
and a second with two materials (tissue and bone). These
two phantoms provide an ability to more closely simulate
the patient and provide a means to more accurately
measure dose delivered in a patient surrogate.
EP-1436 A newly designed water-equivalent bolus
technique enables BNCT application to skin tumor.
K. Hirose
1
, K. Arai
1
, T. Motoyanagi
1
, T. Harada
1
, R.
Shimokomaki
1
, T. Kato
1
, Y. Takai
1
1
Southern TOHOKU BNCT Research Center, Radiation
Oncology, Koriyama, Japan
Purpose or Objective
The accelerator-based boron neutron capture therapy (AB-
BNCT) system was developed in order to enable the
installation of safe hospital BNCT. An important feature of
AB-BNCT system is its capability of delivering great doses
to deep-seated tumors under condition in which a
beryllium target and neutron-beam-sharping assembly are
adjusted for production of epithermal neutron that is
applicable
for
more
types
of
tumor
localization.Conversely, AB-BNCT is less suitable for
superficial cancers, such as malignant melanoma. In this
study, we developed a newly water-equivalent bolus
technique that has no production of prompt gamma ray
and no influence on complicating dose calculation, and we
evaluated the effect of this technique on treatment
quality for a case of malignant melanoma patient.
Material and Methods
A water-equivalent bolus was prepared as follows.
Urethane foam was cut down into the size of 3-cm larger
than the superficial lesion, infiltrated with distilled water
with deaeration, and covered with a thin film. The
simulated patient was played by a healthy man and
simulated condition was originated from a malignant
melanoma patient with the lesion of 3-cm diameter
localized in a sole of right foot. The superficial lesion was
bordered by a catheter and covered with a water-
equivalent bolus. Using treatment planning system SERA,
the tumor is depicted as a region surrounded by the
catheter with 5-mm thickness, and also skin is depicted as
the other region except for tumor with 3-mm thickness
from body surface. A water-equivalent bolus was
delineated as water. This was placed into air in calculation
in condition with no bolus. For comparison with bolus-like
effect of a covered collimator, the outline of an imaginary
collimator cover was set as a mass of polycarbonate or a
water tank filled with water with 20-50-mm thickness. For
calculation of photon-equivalent dose (Gy-Eq), blood 10B
concentrations, 10B tumor/blood concentration ration,
and CBE factor for 10B(n,α)7Li reaction were assumed to
be 25 ppm, 3.5, 4.0. Tolerance dose of the skin was
regarded as 18 Gy-Eq.
Results
In condition with no bolus, irradiation time was 121.6 min,
and tumor Dmax and Dmean were 125 Gy-Eq, and 74.3 Gy-
Eq, respectively. In condition with water-equivalent bolus
technique, irradiation time was 72.1% decreased (33.9
min) compared with no bolus condition. Also tumor Dmax
and Dmean were 54.4 Gy-Eq and 45.0 Gy-Eq, and the dose
homogeneity was dramatically improved. Skin Dmax
became greatly less than tolerable dose (11.5 Gy-Eq,
59.6% decrease).The bolus-like effect of covered
collimator with a mass of polycarbonate or water tank was
not sufficient. Dose homogeneity and irradiation time was
largery worse than the condition with a water-equivalent
bolus.
Conclusion
Although this study was examined for a single case of
melanoma patient, our results revealed that water-
equivalent bolus technique could have a great
effectiveness on dose improvement of AB-BNCT for
superficial
cancers.
EP-1437 New Cobalt-60 system for reference
irradiations and calibrations
C.E. Andersen
1
1
DTU Nutech Technical University of Denmark, Center
for Nuclear Technologies, Roskilde, Denmark
Purpose or Objective
Cobalt-60 plays an important role as reference beam
quality in radiation dosimetry and radiobiology. Only few
systems are available on the commercial market for the
therapeutic dose range (~1 Gy/min), and it is therefore of
interest for research and calibration laboratories that a
new irradiator (Terabalt T100 Dosimetric Irradiator) has
been introduced by UJP Praha, Czech Rebublic. In 2013,
DTU Nutech in Denmark acquired the first unit of this new
model, and the purpose of this contribution is to report on
(i) the main characteristics of this gamma irradiator found
during the commissioning work, and on (ii) additional
developments carried out in order to apply the irradiator
for highly precise, automated (i.e. computer controlled)
irradiations.
Material and Methods
The irradiator has a fixed horizontal beam axis about 110
cm above the floor. A collimator system enables field sizes
from 5x5 cm
2
to 40x40cm
2
at the reference point at 100
cm from the source. The irradiator is equipped with a
GK60T03 cobalt-60 source having an activity of 250 TBq
corresponding to a dose rate of about 1.1 Gy/min at the
reference point (Sep. 2016). The source is fully computer
controlled. A special rig of 10x10 cm
2
aluminum profiles
has been designed in collaboration with UJP Praha. This
rig is equipped with a water-tank lift and an xyz-stage for
precise positioning of ionization chambers and other
dosimeters at the reference point. An optical system is