Use of accelerators for medical Use of accelerators for medical treatment in Tomsk region (Russia)treatment in Tomsk region (Russia)

Tomsk Polytechnic UniversityTomsk Polytechnic University

A.P. Potylitsyn

Cyclotron U-120 is operated in Cyclotron U-120 is operated in

NPI TPU from the beginning of 1960’s.NPI TPU from the beginning of 1960’s.

The main parameters:The main parameters:• 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.

ActualityActuality

Since 1984 Cancer research institute of Since 1984 Cancer research institute of ТТomsk Scientific omsk Scientific Center of Russian Academy of Medical Science uses the Center of Russian Academy of Medical Science uses the cyclotron U-120 of Tomsk Polytechnic university for cyclotron U-120 of Tomsk Polytechnic university for realization of neutron therapy program, preoperative or realization of neutron therapy program, preoperative or postoperative neutron therapy as a method of combined postoperative neutron therapy as a method of combined treatment of various localizations of cancer with photon treatment of various localizations of cancer with photon therapy;therapy;For last 10 years in Cancer research institute of TSC RAMS For last 10 years in Cancer research institute of TSC RAMS fast neutron beam is applied to treatment cancer of a fast neutron beam is applied to treatment cancer of a mammary gland and its relapses as an independent method of mammary gland and its relapses as an independent method of cancer therapy or in a combination with electron or gamma-cancer therapy or in a combination with electron or gamma-therapy;therapy;Since 1989 betatronSince 1989 betatron PMB-6 PMB-6 is used for is used for intra-surgical intra-surgical therapy therapy in operationalin operational room room. .

 HARDWARE

ANDTHEORETICAL

DOSIMETRYNEUTRONS

 RADIOBIOLOGICAL

ASPECTS OFNEUTRONTHERAPY

COMPUTER DOSE CALCULATION

ANDRADIOBIOLOGICAL

PLANNING METHODS OFNEUTRON THERAPY

    

         

  

          

MAINTENANCE MAINTENANCE OF NEUTRON THERAPYOF NEUTRON THERAPY

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.

  

 

     

collimator

NEUTRONS

             

deuterons

Beryllium target 3 mm

patient

Radiation protection

The neutron channel diagram channel diagram for for neutron therapy

The neutron channel drawingchannel drawing

((using beam of the cyclotron U – 120 for neutron therapyusing beam of the cyclotron U – 120 for neutron therapy ))

Dose field min – 4x4cm2;Dose field max – 15x15cm2.

Measuring system diagramMeasuring system diagram1- 1- deuterons beamdeuterons beam; 2- ; 2- targettarget; ;

3-3-beam current monitorbeam current monitor;;4-4- collimator collimator; 5-; 5-phantomphantom;;

6,11-6,11- ionization ionization chamberschambers; ; 7,12-7,12- preamplifiers preamplifiers; 8,13-; 8,13- dosimeters dosimeters; ;

9,10-9,10- ionization ionization chambers moving mechanism.chambers moving mechanism.

Dosimetric and radiobiological Dosimetric and radiobiological researchesresearches

1 – field 1 – field

S=225 cmS=225 cm22;;

2 – field 2 – field

S=48 cmS=48 cm22..

Neutrons doze distributionNeutrons doze distribution vs. tissue vs. tissue depthdepth

cm

Do

ze, r

el. u

nits

The neutron doze distribution in tissue-equivalent The neutron doze distribution in tissue-equivalent media calculated for media calculated for 6×8 с6×8 сmm22 radiated ariaradiated aria in plane in plane

which parallel to which parallel to 8 с8 сm sidem side

cm

cm

.

The neutron absorbed doze distribution in The neutron absorbed doze distribution in skinskin

near its surfacenear its surface

mm

Do

se, r

el. u

nit

s

1 – 0 cm;2 – 20 cm.

Average specific KERMa of neutronsAverage specific KERMa of neutrons

for various tissues and materialsfor various tissues and materials

Influence of a adipose tissue

layer on doze distribution of neutrons D

ose

, rel

. un

its

adip

ose

tissu

e

g/cm2

Distribution of the neutrons absorbed doze Distribution of the neutrons absorbed doze in view of and without taking into account in view of and without taking into account

heterogeneity in a pulmonary tissue.heterogeneity in a pulmonary tissue.D

oze

, rel

. un

its

Depth, cm

Dependence of a relative number of surviving Dependence of a relative number of surviving cells on the absorbed doze gamma-radiation (1) cells on the absorbed doze gamma-radiation (1)

and neutrons (2).and neutrons (2).

rela

tive

nu

mb

er

of

surv

ivin

g ce

lls

Doze, Gy

Total distribution of equal-effectiveTotal distribution of equal-effective dozes at dozes at neutrons and gamma – radiations treatmentsneutrons and gamma – radiations treatments

ConclusionsConclusions

For last 20 years treatment of 1000 patients is For last 20 years treatment of 1000 patients is done done on a cyclotron on a cyclotron U-120;U-120;

Efficiency of neutron therapy at separate localizations Efficiency of neutron therapy at separate localizations of cancerous growth allows prolonging non-relapse of cancerous growth allows prolonging non-relapse period and the general life expectancy of patients;period and the general life expectancy of patients;

In 2007 - 2011гг perspective scientific researches on In 2007 - 2011гг perspective scientific researches on neutron therapy of resistant cancerous growth are neutron therapy of resistant cancerous growth are planned in Cancer research institute of TSC RAMS.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 tasksThe main tasks::

Ranging of a maximum permissible single doze Ranging of a maximum permissible single doze in view of type and volume of an irradiated in view of type and volume of an irradiated tissue;tissue;Choice of a total doze for postoperative distant Choice of a total doze for postoperative distant gamma-therapy (DGT), for supplementing intra-gamma-therapy (DGT), for supplementing intra-surgical radiation therapy (ISRT) after some time surgical radiation therapy (ISRT) after some time interval;interval;Choice of admissible value of the single doze Choice of admissible value of the single doze ISRT spent after preoperative DGT;ISRT spent after preoperative DGT;Calculation of distribution of the total absorbed Calculation of distribution of the total absorbed doze of electron beam and gamma - radiations.doze of electron beam and gamma - radiations.

Distant gamma-therapy (DGT)Distant gamma-therapy (DGT)

Лшр Ла Ллла Радиальное распределение и изодозные кривые в плоскости, проходящей через ось симметрии пучка в водном фантоме, облучаемом коническим пучком гамма-излучения.

Radial distribution and equal-doze curves in a plane which are passing through an axis of symmetry of a conic beam of gamma-radiation in the irradiated water phantom.

44--fields irradiation diagramfields irradiation diagram

Distant gamma-therapy, Distant gamma-therapy, multiplemultiple--fields irradiationfields irradiation

Small-sized betatron inSmall-sized betatron in operating-roomoperating-room

Betatron features:Betatron features:Electron energyElectron energy – – 6 6 MeVMeV

Electron beamElectron beam power atpower at 70 70 cm distancecm distance – – up toup to 6 6 Gy/minGy/min

FrequencyFrequency – – 200 200 HzHz

ConsumptionConsumption powerpower– – 2 2 kWtkWt

Diagram of electron outlet Diagram of electron outlet from small-sized betatronfrom small-sized betatron

1 – electromagnet1 – electromagnet

2 – 2 – accelerating chamberaccelerating chamber

3 – 3 – outlet outlet windingwinding

Longitudinal absorbed doze distribution of an electron beam in

the water phantom on an axis of the beam.

Irradiation by electron beamIrradiation by electron beam

Profile absorbed doze distributionof an electron beam in a water

phantom.

Isodoze distribution at interaction electronbeam with 5,4 MeV energy and a water phantom

Irradiation by electron beamIrradiation by electron beam

Total distribution of the absorbed electron Total distribution of the absorbed electron beam dozebeam doze and gamma - radiations doze and gamma - radiations doze

along a line, which perpendicular to axis of a along a line, which perpendicular to axis of a electron beamelectron beam

• 8 Gy• 10 Gy• 15 Gy• Gamma-radiation

Сечение Х - Х

0

0.2

0.4

0.6

0.8

1

1.2

1.4

-15 -10 -5 0 5 10 15

X [см]

D [

отн

. ед

.]

X-X cross section

Do

ze,

rel.

un

its

Total distribution of the absorbed electron Total distribution of the absorbed electron beam dozebeam doze and gamma - radiations doze and gamma - radiations doze

along a axis of a electron beamalong a axis of a electron beam

• 8 Gy• 10 Gy• 15 Gy• Gamma-radiation

Сечение Y - Y

0

0,2

0,4

0,6

0,8

1

1,2

1,4

-15 -10 -5 0 5 10 15

Y [см]

D [

отн

. ед

.]

Y-Y cross section

Do

ze,

rel.

un

its

Comparison of the absorbed dozesComparison of the absorbed dozesand corresponding biological effectsand corresponding biological effects

Дозы ВДФДозы ВДФ

Doz

e an

d T

DF

(tim

e-do

ze-f

ract

ioni

ng)

valu

es

Dozes, Gy TDF

X, сm

Y,

сmIsodoze distribution of total absorbedelectron beam and gamma - radiations dozes

e

Distribution of radiation in non-uniform Distribution of radiation in non-uniform media at implants presencemedia 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 Radiation acts upon water phantom in which on some depth there is a plate which on some depth there is a plate from a titanium-nickel alloy.from a titanium-nickel alloy.

}

d - depth, 3 or 10 cm.

NiTi

d

NiTi layers are placed atNiTi layers are placed at 3 3 cmcm andand 10 10 cm depthcm depth. .

Kjdhkl Доза на оси конического пучка гамма-квантов в водном фантоме (гистограмма) со слоями NiTi (точки). The histogram of a doze on an axis of a conic beam of gamma-quantums in the water phantom with NiTi layers (are 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.

SummarySummary::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 non-uniform 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!