ARTCOLL PACKAGE FOR GAMMA ART6000 TM ROTATING GAMMA SYSTEM EMISSION SPECTRA CALCULATION

Transcription

1 ARTCOLL PACKAGE FOR GAMMA ART6000 TM ROTATING GAMMA SYSTEM EMISSION SPECTRA CALCULATION Radovan D Ili}. PhD Institute of Nuclear Sciences Vin~a Belgrade, Serbia and Tomasz K. Helenowski, M.D. 936 Burnham Court GLENVIEW, IL 60025, USA Author's rasacale@gmail.com in Serbia tkh@tkh.com in USA Belgrade - Chicago 2006

2 The Asymmetric Rotating Gamma System Gamma ART 6000 Figure 1. The RGS ART 6000 System view. The GAMMA ART 6000 Rotating Gamma System s design is based on the USA patents No. 5,528,653; No. 5,757,866; and 6,512,813 B1. The system utilizes concentric 360 degree arcs formed by convergent gamma-ray beams that are emitted from 30 Cobalt-60 cylindrical sources. The design of the GAMMA ART 6000 combines the accuracy of the static gamma design and the arching of the accelerator based stereotactic radiosurgery system. The rotation of the Cobalt-60 gamma-ray beams during treatment is the major enhancement resulting in many advantages. By rotating the source body, primary collimators and secondary collimators together, a smaller number of radiation sources are utilized. Because the beams converge from greater solid angle as compared with the static design, the radiation dose to normal, healthy tissue surrounding the target is reduced, since the dose to the normal tissue is spread over a greater volume. The secondary collimators are built-in, eliminating the need for secondary collimator helmets, simplifying setup and changing of the treatment spot size. The use of fewer Cobalt-60 sources also reduces the cost for changing the sources.

3 Compared to the linear accelerator based radiosurgery systems, the RGS design employs much larger number of arcs in a single fraction to minimize dose to organs and tissues surrounding the izocenter location, without increasing the treatment time and the positional uncertainties. The RGS system delivers dose from 6 groups of cobalt sources spaced at 60 degree increments around the central axis of the treatment machine. Each group contains 5 sources increasingly inclined from the transverse plane. The first source is located at an incline of 13 degrees which increases to 43 degrees for the fifth source. Additionally, each of the 6 groups contains a slight offset of incline angle. Figure 2. The helmets with holes for Cobalt-60 sources and a secondary collimators plugging. The combined effect of this geometry, when rotated during treatment is to produce a region of dose that can be thought of as five conical wedges whose axis is coincident with the rotation of the treatment machine. The treatment planning system Explorer 3D is implemented on a graphic computer workstation running Windows 2000 / NT. Dose calculation is accomplished in two steps. First, for each shot, a normalized dose rate matrix is generated. The individual shot matrix is then scaled, weighted and summed into a single dose rate matrix. Actual dose times are derived from the prescription dose and the dose rate matrix, and then adjusted for the age of the radioactive sources.

4 ARTCOLL PACKAGE Overview of Package ARTCOLL package calculates emission spectra at end of collimator for Gamma ART6000 TM Rotating Gamma System, using the FOTELP-COLL and RED-COLL versions of Monte Carlo FOTELP code ( The ARTCOLL package is a Windows and LINUX application and consists of two programs. First, the FOTELP-COLL, with full physics and real shape and with dimensions of the photon source from C0-60 source, is simulating their transport and gives an emission spectra of primary and secondary particles (photon and electron) at the end of primary or secondary collimators. This program is providing the experiments with collimators for obtaining 3D distribution of absorbed dose in phantoms. Second, the RED-COLL treating only photon transport from suorce to end of primary collimator. Program RED-COLL servs for fast, routine simulations of the emission spectra with good statistics (more then billion photons from source). The FOTELP-KNF code with full physics and real shapes and materials, uses preprocessed emission spectra for calculating 3D dose during single rotation of ART6000 (see FOTART package). Programs FOTELP-COLL and RED-COLL can simulate collimators RGS ART 6000 as independent packages. They are providing simulations of collimators different from those in ART 6000, such as collimators Leksell GammaKnife or collimators of therapeut accelerators, and also with the phantoms of various forms, dimensions and material composition. 1. Collimator configuration Program FOTELP-COLL with Monte Carlo techniques is simulating photon transport from Cobalt-60 source through that source and all parts of primary and secondary collimator, and in the end through the experimental phantom. The emission spectra of all primary and secondary particles that had reached the bases of primary or secondary collimator can be used for the continuation of simulation in other parts of collimator or experimental phantom. This opportunity was realized primarily to reduce the need of long-term simulation from the source to phantom by using the emission spectra. Fig 3. shows the cross section of ART 6000 collimator, cross section 4 of the photon source

5 and water phantom. The figure is illustrating all problems JDET Figure 3. The ART 6000 conllimators cross section of photon flow simulation, electrons and positrons, and their secondary particles through all the elements of collimator construction The FOTELP-COLL usage The preparation of FOTEL-COLL program for simulation begins with writing of geometry model in accordance to a used geometry module RFG. User already has previously prepared geometry models for all ART 6000 collimator types, and in folder INP2K5 they have the names: THA2K5... Input files for "4mm" collimator THB2K5... Input files for "8mm" collimator THC2K5... Input files for "14mm" collimator THD2K5... Input files for "18mm" collimator Each geometry form can be controlled by program rfgt.for in folder RFGTEST, and the procedure is described in fot-2k3.pdf. Program FOTELP-COLL has three simulation opportunities that user can choose by doing input of flag values ISURF and JDET in fotelp.inp. The flag values have following meanings: ISURF=10 for the simulation of emission spectra at the end of primary collimator with JDET=20 or secondary collimator with JDET=14 with the spectra written in file ASURF.DAT. Sometimes it is useful to know the emission spectra close under the photon source, what can be obtained with flags ISUR=10 and JDET=12.

6 ISURF=20 with the emission spectra of 3D dose simulations in water or some other phantom. This simulation is performed by program when file ASURF.DAT is used with name ASURF.INP. Option ISURF=20 is implementing for the emission spectra at the end of primary or secondary collimator. ISURF=30 for simulation of 3D absorbed doses in phantom. FEPDAT - Transition probabilities For materials used in collimators construction, FEPDAT.EXE creates files of PEC type, that are needed for the simulation with collimator materials contained in FEPDAT.INP. FOTELP - Input data preparation In the FOTCOM.FOR file there are maximal values declarated in PARAMETER statements. IGZON = 22 - number of geometry zones in RFG.INP; MATER = 8 - number of different materials in FEPDAT.INP; LEL = MATER*5 number of elements in all materials; LNE = 150 number of energy bins; MSUR = 2, number of lines in file ASURF.INP; MPIX, MPIY, MPIZ = 161 x 161 x161 voxel numbers along X,Y,Z axis. After adjusment of these values, you should create FOTELP.EXE. User must carefully check out FOTELP.INP according to the FOTINF.DOC file and set the values in blue, red and magenta color in this file. First and second steps in simulation Start FOTELP.EXE and after few minutes you will have the simulation test with ISURF=10 for NPOC=1E6 photons. After copying ASURF.INP file=asurf.dat file, do the simulation on target with ISURF=20 that you will change into FOTELP.INP. Result of simulation Result of these simulation provide file FIGDOS.DAT. That one is the matrix of deposited energies in target EMEP(k,i,j) in MeV/kg. The matrix user can be read for independent graphical presentations with dimension emep(kzk,ixi,jyj) open(8,file='figdos.dat') read(8,*) kzk,ixi,jyj do k=1,kzk

7 do j=1,jyj read(8,108) (emep(k,i,j),i=1,ixi) 108 format(64e11.3) close(8) Note: From the FOTELP.INP file take your dimensions of EMEP matrix. In ARTCOLL package the user is provided with program acdose.for for calculating the absorbed dose around izocenter of "tumor" in phantom. This program uses files 2 figdose.dat ( E ) and summa2.dat ( E ) for that purpose. Change of target distance i When you want new simulation with the variable target position, you should keep ASURF.INP file as referent, and then do the changes in files RFG.INP and FOTELP.INP. In RFG.INP file, move the lines D31 and D32 for DZ by writing new values in magenta of the field. For that same DZ, change Zt value in magnet of the field in FOTELP.INP. Change of collimator materials If you wish to change collimator materials but without the change of geometry of collimator types, you should choose the material codes in file material.dat, and after compiling fmatsel.for user can start fmatsel.exe. The further work should be done by following the previously procedures from, under the condition to carefully create input file FOTELP.INP. The trick is that the fields marked in the italic blue in FOTELP.INP should correspondent to the indexes of new materials written in FEPDAT.INP file. That is easy thing to do if you consult FOTELP.INP before making changes. Geometry file RFG.INP C [ THD2K5 August 17, 2005 ] C [ RGS ART 6000 '18 mm' collimator, Chicago - Tomasz Helenowski ] C [ Cylinders ] D1 [ OBLIK=6; JED=2; KOEF = 2.5, 2.5 ] D2 [ OBLIK=6; JED=2; KOEF = 1.3, 1.3 ] D3 [ OBLIK=6; JED=2; KOEF = 0.25, 0.25 ] D5 [ OBLIK=6; JED=2; KOEF = 1.3, 1.3 ] D6 [ OBLIK=6; JED=2; KOEF = 0.3, 0.3 ] D7 [ OBLIK=6; JED=2; KOEF = 1.0, 1.0 ] D8 [ OBLIK=8; JED=2; KOEF = 1.0, 1.0, ; TRANS=0.0, 0.0, ] D9 [ OBLIK=6; JED=2; KOEF = 8.0, 8.0 ] D10 [OBLIK=6;JED=2;KOEF=0.05,0.05;TRANS=-0.075, ] D11 [OBLIK=6;JED=2;KOEF=0.05,0.05;TRANS= 0.000, ] D12 [OBLIK=6;JED=2;KOEF=0.05,0.05;TRANS= 0.075, ] D13 [OBLIK=6;JED=2;KOEF=0.05,0.05;TRANS= 0.000, ] D14 [OBLIK=3;JED=2;KOEF=100.0, 100.0, ] C [ Planes ] i

8 D20 [ OBLIK=2; JED=1; KOEF = 0.0, 0.0, 1.0, ] D21 [ OBLIK=2; JED=1; KOEF = 0.0, 0.0, 1.0, ] D22 [ OBLIK=2; JED=1; KOEF = 0.0, 0.0, 1.0, ] D23 [ OBLIK=2; JED=1; KOEF = 0.0, 0.0, 1.0, ] D24 [ OBLIK=2; JED=1; KOEF = 0.0, 0.0, 1.0, ] D25 [ OBLIK=2; JED=1; KOEF = 0.0, 0.0, 1.0, ] D26 [ OBLIK=2; JED=1; KOEF = 0.0, 0.0, 1.0, ] D27 [ OBLIK=2; JED=1; KOEF = 0.0, 0.0, 1.0, ] D28 [ OBLIK=2; JED=1; KOEF = 0.0, 0.0, 1.0, ] D29 [ OBLIK=2; JED=1; KOEF = 0.0, 0.0, 1.0, ] D30 [ OBLIK=2; JED=1; KOEF = 0.0, 0.0, 1.0, ] D31 [ OBLIK=2; JED=1; KOEF = 0.0, 0.0, 1.0, 2.5 ] D32 [ OBLIK=2; JED=1; KOEF = 0.0, 0.0, 1.0, 18.5 ] C [ Complex space ] D51 [ OBLIK=1; LOGIC= 10I(26 I-27) ] D52 [ OBLIK=1; LOGIC= 11I(26 I-27) ] D53 [ OBLIK=1; LOGIC= 12I(26 I-27) ] D54 [ OBLIK=1; LOGIC= 13I(26 I-27) ] D55 [ OBLIK=1; LOGIC= (3I(26I-27))I-51I-52I-53I-54 ] D56 [ OBLIK=1; LOGIC= 2I(28I-30) ] D57 [ OBLIK=1; LOGIC= 2I(27I-28) ] D58 [ OBLIK=1; LOGIC= 6I(24I-25) ] D59 [ OBLIK=1; LOGIC= (5I(24I-25))I-58] D60 [ OBLIK=1; LOGIC= 8I(22I-23) ] D61 [ OBLIK=1; LOGIC= (7I(22I-23))I-60 ] D62 [ OBLIK=1; LOGIC= 9I(32I-31) ] D71 [ OBLIK=1; LOGIC= 3I(26I-27) ] D72 [ OBLIK=1; LOGIC= 5I(24I-25) ] D88 [ OBLIK=1; LOGIC= 2I(23I-24) ] D89 [ OBLIK=1; LOGIC= 2I(26I-27) ] D85 [ OBLIK=1; LOGIC= 89I-71 ] D73 [ OBLIK=1; LOGIC= 7I(22I-23) ] D74 [ OBLIK=1; LOGIC= 5I(25I-26) ] D63 [ OBLIK=1; LOGIC= (1I(22I-30)I-56I-57I-89I-74I-72I-73I-88) ] D64 [ OBLIK=1; LOGIC= 1I(20I-21) ] D65 [ OBLIK=1; LOGIC= 1I(21I-22) ] D66 [ OBLIK=1; LOGIC= 1I(31I-20) ] D67 [ OBLIK=1; LOGIC= (14I-(1I(22I-30))I-64I-62I-65I-66) ] C [ Material zones ] Z1 [ DOMEN = 51 ] Z2 [ DOMEN = 52 ] Z3 [ DOMEN = 53 ] Z4 [ DOMEN = 54 ] Z5 [ DOMEN = 55 ] Z6 [ DOMEN = 56 ] Z7 [ DOMEN = 57 ] Z8 [ DOMEN = 58 ] Z9 [ DOMEN = 59 ] Z10 [ DOMEN = 60 ] Z11 [ DOMEN = 61 ] Z12 [ DOMEN = 74 ] Primary collimator end Z13 [ DOMEN = 65 ] Z14 [ DOMEN = 64 ] Lexan detektor Z15 [ DOMEN = 66 ] Z16 [ DOMEN = 62 ] Z17 [ DOMEN = 63 ] Z18 [ DOMEN = 67 ]

9 Z19 [ DOMEN = 85 ] Z20 [ DOMEN = 88 ] Secondary collimator end Z21 [ DOMEN =-14 ] K [ End of data ] FEPDAT.INP Material data file Input file fepdat.inp is prepared by user starting from the material being used for photon source, collimators and phantom, For RGG ART 6000 these materials were accepted: Co, Fe, W, Air, Lexan and Tissue Soft (ICRU 4 components), and their index values in file material.dat are 26, 27, 74, 104, 219 and 262. Preserving that sequence, one starts program fmatsel.exe which prepares input fepdat.inp. After running program fepdat.exe one obtaines file fepdat.out which becomes the first part of input file fotelp.inp. From the end of fepdat.out, here on the user is writing the remaining of fotelp.inp file: 0.010, 0.06, 0.06 Cutoff Energy: photon, electron, positron [MeV] (These values should be chosen carefully due to time of simulation) , 0, 0, 0 Atomic relaxation, Delta electron, Bremsstrahlung (If any number is greater then zero, the program is following the process coresponding to that number). Zones number, JGEM, ISURF, JDET 21, 202, 10, 12 JGEM = 101 for one cylindrical source; JGEM=202 for 4 x 26 cylindrical sources Zones, Material index, JAWA, Material (comment) JAWA = 0 electron history to cutoff energy JAWA = 1 electron history in following material (see fot-2k3.pdf) 1, 2, 1 Co 2, 2, 1 Co 3, 2, 1 Co 4, 2, 1 Co 5, 1, 1 Fe 6, 3, 1 W 7, 1, 1 W 8, 4, 0 Air 9, 3, 1 W 10, 4, 0 Air 11, 3, 1 W 12, 6, 0 Air 13, 1, 1 Fe 14, 5, 1 Lexan 15, 4, 0 Air 16, 4, 0 TISSUE 17, 1, 1 Fe 18, 4, 0 Air

10 19, 3, 1 W 20, 4, 0 Air 21, -2, 0 Vacuum 0.0, 0.0, 10.5 Target center (X tm,y tm,z tm ) 0.001, 0.050, , 2.60, , , , , , 2, 0, , Number of photon, Cutoff time [minutes] 1.33, , , 1.0, X_base, 0.5 Y_base and Z_target [cm] 40, 40, 60 Number of bins alog above lines The scheme of photon source, primary and secondary collimator with phantom is shown at Figure.3. In planning the routine therapy, fotelp-coll is to be used only at the beginning or when necessary in order to obtain an emission spectra at the bottom of primary collimator with option ISURF=10 and flag JDET=20. (See details in fotinp.doc). Sometimes there is a need of knowing the distribution of deposed energy in phantom, when any of 4 collimator types is to be used. Program fotelp-coll has such an opportunity, and a following text is related to that usage which user starts from the command line. a) The choice of source material, primary collimator and protection. Number of materials (first line) is to be chosen by starting program fmatsel.exe, then the codes of materials from file material.dat (second line), lower and upper energy of particles (MeV), the factor of scale MFAK=8 (third line) and parameters of angular distributions 1, 1, 1 (fourth line). At the end, the file fepdat.inp appears for starting program fepdat.exe which is calculating cross section and transition probabilities for the chosen materials. b) Data preparation for the simulation starts with putting data into file fotelp.inp. Then the program fotelp.exe simulates photon transport and obtaining of ASURF.DAT file with particles emission spectra. This program uses any rfg.inp geometry file for simulation for collimators of 4mm, 8mm, 14mm or 18mm type (THA2K5, THB2K5,THC2K5 or THD2K5), because any of them has an identical primary collimator. c) For this way of using program FOTELP-COLL one should consult fot-3k3.pdf where all the details of data preparation are described.

11 1.2. The RED-COLL code At the beginning of FOTELP-COLL program description we pointed that collimator simulations run with full-physics model so that the entire physical picture of photon and secondary particles transport is to be preserved. Since very small number of particles arrive at target - patients head, the simulation of that picture is demanding lots of time. For the acceptable result of simulation it is needed to take between 10 8 and 10 9 photons in 4 As the emission spectra is simulation characteristics, it's long duration can be tolerated because the spectra can be obtained independetly from it's usage in therapy planning. However, that approach may be abandoned when certain processes that occur with charged particles in construction materials are not of interest for tumor radiating. If we ignore processes of secondary interest and focus main attention at the simulation of primary and scattered photon transport, than the program RED-COLL can be written with reduced physical picture which provides only emission spectra at the end of primary collimator. With program RED-COLL, simulation of RGS ART 6000 collimator takes much less time than simulation with programs FOTEL-COLL. In paragraph 1.1. The procedures for preparation and usage of program FOTELP-COLL are described. For the program RAD-COLL these procedures and all input files are prepared in the same way Single collimator and phantom's experiments A single RGS ART 6000 channel consists of photon source, primary and secondary collimator. When the phantom is placed at some distance at collimator axis, one gets an experimental channel that is suitable for numerical experiments in radiotherapy. In all phases of developing program FOTELP-COLL such need was taken in consideration. Here we describe two opportunities in using that program. First one is regarding homogenuos and second heterogenuos phantoms. Homogenous phantoms is obtained when instead of cylindrical phantom, which is limited by cylinder D9 and planes D31 and D32, we place a box in RFG.INP. Phantoms can be filled with water or some other material. For those configurations one can use the characteristic of program FOTELP-COLL to provide 3D absorbed dose in voxels. Heterogenous phantoms is obtained when instead of cylindrical phantom, which is limited by cylinder D9 and planes D31 and D32, we place a dish with shape of box having the wall in RFG.INP. Phantoms can be filled with water or some other material, and the wall can be of material equal to scull. Exploration of such phantoms is supported by the characteristic of program FOTELP-COLL to provide 3D absorbed dose in voxels. Procession of simulation results with various phantoms is supported by program acdose.for for calculating the absorbed dose around "tumor" izocenter in phantom. Program acdose.for uses files figdose.dat 2 E ) and summa2.dat ( E ) to calculate dose when user chooses voxel numbers around ( i izocenter. i