The 13th Symposium on Accelerator Science and Technology, Suita, Osaka, Japan, October 2001

PRESENT STATUS OF PROTON THERAPY STATUS AT THE WAKASAWAN ENERGY RESEARCH CENTER
K.Kume, T.Hasegawa, S.Fukuda, S.Fukumoto, GKagiya, S.Kakiuchi, !.Maruyama, K.Yamamoto
and N.Yokohama
The Wakasa Wan Energy Research Center, Tsuruga, Japan
Abstract
Proton therapy project is proceeding at the Wakasa Wan
Energy Research Center, Japan. Construction of anaccelerator complex and a therapy beam line has been
finished by this summer. The whole system will be shownin this presentation. Some obtained data will also bepresented.

horizontal direction (Fig.l ). These two ports were
designed to have a same isocenter position. Beam fromthe synchrotron can be stopped at a beam stopper (BS)before entering the therapy beam line.

1 INTRODUCTION
Ion beams are thought to have a better control ability intheir depth dose distribution because of the existence ofBragg peaks for radiotherapy, in comparison with photons
and electrons[l]. The accelerator complex at the Wakasa
Wan Energy Research Center (WERC) can deliver p up to200MeV, which can reach 25cm depth in water, andproton therapy project has been planned. It must be notedthat this is the only present facility in Japan where sharean ion accelerator between medical and other purposes.

2 BEAM PRODUCTION AND DELIVERY
Beam production and delivery system can be divided
into following three parts: (1) an accelerator complex
including an ion source, (2) a beam transport and anirradiation field production system for each port. The
construction of the former was finished last year, and thelatter this August.

2.1 An Accelerator Complex
An accelerator complex is consisted of a Cs spatter ionsource, a 5MV tandem accelerator to deliver IOMeV p,
and a 200MeV proton synchrotron. 8nA of the p beam
current has been achieved, where I OnA was planned. Fora medical reason, accelerated beam energy can be chosenfrom 80,90,100,I20,I40,I60,I80 and 200MeV and allthese energies except several of them were actuallyaccelerated. The accelerator system will be described in
the same symposium[2].
The beam comes at the frequency of 0.5Hz from theaccelerator as a pulse beam. The time structure of thebeam is enough flat to produce a uniform irradiation areafor a medical use.

2.2 A Beam Transport and an Irradiation FieldProduction System,
The therapy beam line consists of two ports, one ofwhich is delivering proton beams from vertical direction,and the other from the direction 9.5 degree upper than theFigure I. Constructed clinical beam ports and positioning
X-ray CT with a movable bed.
To be used for medical use, beam size can be widened
to cover a target(= cancer) volume of I OOmm x I OOmm xI OOmm at most. Ridge filters are used to get a spread out
Bragg peak (SOBP) , and a pair of wobbler magnets and ascatterer system for are used to get above lateral size. A
snout box, where a patient collimator and a patient bolus
are in, is located at each end of two ports. Obtained beamprofile with both of wobbler magnets and a scatterer
system working show that the flatness at the irradiation
field (SOBP60mm x (IOOmmi) to give 3Gy/min has
been achieved with 2.5% accuracy at 180MeV ( Figs.land 2 ), which is enough for a clinical application. Otherridge filters will be produced and tested.
Beam delivery can be interrupted whether by manually
shutting BS or by automatically when measured doses in
two dosimeters reach preset values. BS operations isavailable at two places, one of which is at the central
control room with operators present, the other at theclinical control room with medical doctors present.

3 THERAPY SYSTEM
The therapy system is divided into two parts; (I)treatment planning, and (2) clinical irradiation.

3.1 Treatment Planning
Before each clinical trial, a patient bolus( polyethylene ) and a patient collimator ( brass ) must be
produced, designed at a treatment planning system {TP)using a portrait taken at X-ray CT (Hitachi W3000AD)-438-The 13th Symposium on Accelerator Science and Technology, Suita, Osaka, Japan, October 2001

next to the beam course. This CT is also used for apositioning purpose at the irradiation ( Fig.3 ).
TP is being developed by Hitachi, which can simulate
the dose distribution in a patient body by both of broad
and pencil beam algorithms; The output is the shape ofthe bolus and collimator, a beam energy, a digital imageof the tumour target (DRR), and an irradiation record. TPis now under verification .of the accuracy by measuring
the dose distribution with designed boluses andcollimators.

3.2 Clinical Irradiation
Each tumour target will be positioned by using the Xray CT and a movable bed ( Fig.3 ), to the isocenter.
Positioning accuracy is supposed to be under lmm, and is
now under verification.

However, there are some problems to be solved before
the real clinical trial. (I) Because the power supply for iscommon for all two ports, it takes an hour to change ports.
This time must be shrink to treat several patients per a day.
(2) It also takes an hour to change p beam energy, andmust be shrink. (3) More ridge filters shall be provided tobe ready to treat various size of tumour. Only two filters
have been provided so far to produce 60mm SOBP at
180MeV and 30mm SOBP at lOOMeV. (4) TP has notbeen verified yet. Detailed dose distribution using boluses
and collimators designed at TP must be measured. (5)Accuracy of patient positioning system shall be measured.
The clinical trial will start after these problems aresolved and some administrative matters are clear. If
everything is clear, the first trial will be started by the end
ofthe 200 1 financial year.

6 REFERENCES

4 CONCLUSION AND DISCUSSION
The proton therapy beam line and the clinicalirradiation system are constructed at WERC. Some
degrees of p energy can be accelerated, and enough strong
intensity and a uniform irradiation field are obtained.

[1] Wilson, R. R.: Radiological use of fast protons.
Radiology, 47,487-491, 1946.
[2] Hatori, S. eta/.: To be presented in this symposium.
movable bed

depth dose

X-ray CT100

50200150

Vertical andhorizontal
irradiation
system250depth(mmlFigure 2. The measured depth dose profile at 60mm
SOBP (spread out Bragg peak) production for 180MeVp.

Figure 4. Patient positioning system.
lal.era! dose distribution-100·-80-60-40-20

2040

6060tOO

distance from center ( mm)Figure 3 Lateral dose distribution for 180MeV p.

-439-(positioning)