Use of accelerators for medical
treatment in Tomsk region (Russia)
Tomsk Polytechnic University
A.P. Potylitsyn
Cyclotron U-120 is operated in
NPI TPU from the beginning of 1960’s.
The main parameters:
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•
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Magnet diameter - 120 cm;
Magnet field
- 14,5 T;
Acceleration radius - 53 cm;
RF system
- 9-17 MHz;
Beam density on the external target ~ 10 uA/cm2;
Number of experimental channels - 5;
Accelerated ions - p, d, He2, N, O, Ne, Ar;
Max energy - 1,2 MeV ∕ nucleon.
Actuality
Since 1984 Cancer research institute of Тomsk Scientific
Center of Russian Academy of Medical Science uses the
cyclotron U-120 of Tomsk Polytechnic university for
realization of neutron therapy program, preoperative or
postoperative neutron therapy as a method of combined
treatment of various localizations of cancer with photon
therapy;
For last 10 years in Cancer research institute of TSC RAMS
fast neutron beam is applied to treatment cancer of a
mammary gland and its relapses as an independent method of
cancer therapy or in a combination with electron or gammatherapy;
Since 1989 betatron PMB-6 is used for intra-surgical therapy
in operational room.
MAINTENANCE
OF NEUTRON THERAPY
HARDWARE
AND
THEORETICAL
DOSIMETRY
NEUTRONS
RADIOBIOLOGICAL
ASPECTS OF
NEUTRON
THERAPY
COMPUTER DOSE
CALCULATION
AND
RADIOBIOLOGICAL
PLANNING METHODS OF
NEUTRON THERAPY
The neutron channel diagram
for neutron therapy
Radiation protection
deuterons
NEUTRONS
collimator
patient
Beryllium
target 3 mm
The deuterons beam (40 uA) hits the beryllium target.
Neutrons are formed at deuterons and beryllium nucleus
interaction. The neutron beam is formed by collimator and acts
upon malignant tumour of a patient.
<En> = 6.3 MeV, D = 0.5 cGy/min per uA.
The neutron channel drawing
(using beam of the cyclotron U – 120 for neutron therapy )
Dose field min – 4x4cm2;
Dose field max – 15x15cm2.
Measuring system diagram
1- deuterons beam; 2- target;
3-beam current monitor;
4- collimator; 5-phantom;
6,11- ionization chambers;
7,12- preamplifiers; 8,13- dosimeters;
9,10- ionization chambers moving mechanism.
Dosimetric and radiobiological
researches
Doze, rel. units
1 – field
S=225 cm2;
2 – field
S=48 cm2.
cm
Neutrons doze distribution vs. tissue
depth
The neutron doze distribution in tissue-equivalent
media calculated for 6×8 сm2 radiated aria in plane
which parallel to 8 сm side
cm
.
cm
Dose, rel. units
The neutron absorbed doze distribution in skin
near its surface
1 – 0 cm;
2 – 20 cm.
mm
Average specific KERMa of neutrons
for
various
tissues
and
materials
СРЕДНЯЯ УДЕЛЬНАЯ КЕРМА ( фГр* м^ 2 ) НЕЙТРОНОВ
ДЛЯ РАЗЛИЧНЫХ ТКАНЕЙ И МАТЕРИАЛОВ
SBT
BT
Adipose tissue
Brain
Polyethylene
Water
4.5
7
3.8
6
5.6
4.8
5
6.3
4
4.8
3
2
1
0
Influence of a adipose tissue
adipose tissue
Dose, rel. units
layer on doze distribution of neutrons
g/cm2
Distribution of the neutrons absorbed doze
in view of and without taking into account
heterogeneity in a pulmonary tissue.
Doze, rel. units
Д о з а, о т н. е д.
1,2
1
0,8
0,6
0,4
0
2
6
10
Глубина
Depth,
cm
14
18
20
relative number of
surviving cells
Dependence of a relative number of surviving
cells on the absorbed doze gamma-radiation (1)
and neutrons (2).
Doze, Gy
Total distribution of equal-effective dozes at
neutrons and gamma – radiations treatments
Conclusions
For last 20 years treatment of 1000 patients is done
on a cyclotron U-120;
Efficiency of neutron therapy at separate localizations
of cancerous growth allows prolonging non-relapse
period and the general life expectancy of patients;
In 2007 - 2011гг perspective scientific researches on
neutron therapy of resistant cancerous growth are
planned in Cancer research institute of TSC RAMS.
In additional to neutron therapy we are engaged
dosimetric planning of intra-surgical radiation
therapy and remote gamma-therapy, and also their
combination.
For this aim we are planning to use electron
accelerators:
- Betatron PMB–6 with energy 6 MeV (electron
beam);
- Linac CL75–5–MT with energy 6 MeV (gamma
beam).
Linear accelerator СL75 – 5 – МТ
D = 5 Gy/min
at distance 1 m.
The main tasks:
Ranging of a maximum permissible single doze
in view of type and volume of an irradiated
tissue;
Choice of a total doze for postoperative distant
gamma-therapy (DGT), for supplementing intrasurgical radiation therapy (ISRT) after some time
interval;
Choice of admissible value of the single doze
ISRT spent after preoperative DGT;
Calculation of distribution of the total absorbed
doze of electron beam and gamma - radiations.
Distant gamma-therapy (DGT)
Лшр
Ла
Ллла
Радиальное
распределение
и изодозные
кривые
Radial distribution
and equal-doze curves
in a plane which
are в
плоскости, проходящей через ось симметрии пучка в
passing through an axis of symmetry of a conic beam of gammaводном фантоме, облучаемом коническим пучком
radiation in the irradiated water phantom.
гамма-излучения.
Distant gamma-therapy,
multiple-fields irradiation
4-fields irradiation diagram
Small-sized betatron in operating-room
Betatron features:
Electron energy – 6 MeV
Electron beam power at
70 cm distance – up to 6
Gy/min
Frequency – 200 Hz
Consumption power– 2
kWt
Diagram of electron outlet
from small-sized betatron
1 – electromagnet
2 – accelerating chamber
3 – outlet winding
Irradiation by electron beam
Longitudinal absorbed doze
distribution of an electron beam in
the water phantom on an axis of the
beam.
Profile absorbed doze distribution
of an electron beam in a water
phantom.
Irradiation by electron beam
Isodoze distribution at interaction electron
beam with 5,4 MeV energy and a water phantom
Total distribution of the absorbed electron
beam doze and gamma - radiations doze
along a line, which perpendicular to axis of a
electron beam
Сечение Х - Х
X-X
cross section
• 8 Gy
• 10 Gy
• 15 Gy
D [отн.
units
rel.ед.]
Doze,
1.4
1.2
1
0.8
• Gammaradiation
0.6
0.4
0.2
0
-15
-10
-5
0
X [см]
5
10
15
Total distribution of the absorbed electron
beam doze and gamma - radiations doze
along a axis of a electron beam
• 8 Gy
• 10 Gy
• 15 Gy
rel. units
Doze,
D [отн. ед.]
Сечение
Y-Y
Y-Y
cross section
1,4
1,2
1
• Gammaradiation
0,8
0,6
0,4
0,2
0
-15
-10
-5
0
Y [см]
5
10
15
Comparison of the absorbed dozes
and corresponding biological effects
Значения
and TDF
Doze
дозы
и ВДФ values
(time-doze-fractioning)
80
60
70
77
40
20
0
42
29
8
10
Dozes, Gy
Дозы
41
15
TDF
ВДФ
Isodoze distribution of total absorbed
electron beam and gamma - radiations dozes
Contour Graph 1
14
12
Y, сm
Y Data
10
8
6
e
4

2
0
6
8
10
12
14
16
X, сm
X Data
20
18
20
22
Distribution of radiation in non-uniform
media at implants presence
Development Parallel Monte-Carlo application for the cancer
treatment planning by means high performance clusters with
geometry reconstruction from DICOM images. Simulation and
experimental study of transition effects for the absorbed dose in
tissues adjacent to metal implants.
It is well known that in homogeneous media the absorbed
dose is smooth function of coordinates. But near the interfaces with
dissimilar media dose varies steeply. For particle energies,
applicable for radiation treatment, absorbed dose essentially
increases near upstream side of metal implant, it has deep minimum
near downstream side of metal plate and then with increasing
distance from plate it tends to the value corresponding to
homogeneous media. As it was shown in our calculations this
behavior is due to perturbation in the charged particles flux caused
by high Z material.
Most powerful and exact method allowing to
take in to account the effect described above in
the radiation treatment planning is method of
statistical simulation – Monte Carlo (MC).
Disadvantage of the method is slow
convergence, it is very time expensive.
Because of this fact a high performance cluster
or grid is suggested as way to obtain exact
solution for acceptable time.
Radiation acts upon water phantom in
which on some depth there is a plate
from a titanium-nickel alloy.
NiTi
}
d
d - depth,
3 or 10 cm.
NiTi layers are placed at 3 cm and 10 cm depth.
Kjdhkl
The histogram
of a doze onпучка
an axis
of a conic beam
Доза
на оси конического
гамма-квантов
в of gammaquantums
in the water
phantom with
NiTi layers
(are
водном
фантоме
(гистограмма)
со слоями
NiTi
(точки).
designated by a dotted line)
Penetration of radiation through a matter is studied in Tomsk
Polytechnic University for years. Monte Carlo simulation and
analytical methods such as the perturbation theory are used for
calculations of spatial, angular and energy distributions of
photons and electrons in energy interval 10^3 - 10^{12} eV. New
effective methods have been developed for solution of a great
variety of scientific and applied problems. Two candidates for
realization parallel MC code could be considered. First –
GEANT4 code system. There is even example of realization
radiation treatment planner with DICOM images as source for the
geometry construction in GEANT4 source tree. Second candidate
under consideration is our home made code system, which we
call CASCADE.
It is based on original algorithms, developed on
the basis of strict solution of kinetic equations for the
transition probability densities of charged particles.
As result it is much more fast as compared with
corresponding application based on GEANT4.
Although we intensively use GEANT4 for simulation
of high energy experiments and detectors, but for low
energies which are used in radiation treatment we
assume CASCADE as good base for realization of the
parallel radiation treatment planner.
For Geant4 based parallel treatment planning
system any can use DINE environment or ParGeant
interfaces based on TOPC. For now in our cluster
applications we use TOPC tools.
TPU cluster consists of 24 computational nodes.
Each of the nodes has two dual core processors. Total
performance of the cluster is about 1TFLOP.
Summary:
For last 15 years treatment of 1200 patients is done on a
betatron PMB-6;
The linear accelerator СL75–5–МТ is exploited for 3 years,
time of operation ~30 %, treatment of 300 patients is done;
The method providing a choice of maximum permissible
dozes on the basis of several radiobiological models is
developed;
The approaches providing radiobiological planning at
combination ISRT and an distant gamma irradiation are
received;
The method and the program of calculation of gamma- and
electron distributions in tissue-equivalent media is developed;
The researches of laws of distribution of radiation in nonuniform media at implants presence made from NiTi are
carried out;
Training on master's degree courses « Medical physics» is
carried out; students may prepare the final qualifying works
using the neutron-,gamma- and electron beams of
accelerators.
Thanks a lot for attention!