Status and Recent Developments Makoto Asai SLAC On

Status and Recent Developments Makoto Asai (SLAC) On Behalf of the Geant 4 Collaboration May 26 th, 2007 Third Mc. Gill Workshop on Monte Carlo Techniques in Radiotherapy Delivery and Verification Geant 4 - Status and Recent Developments M. Asai (SLAC)

Contents 4 General introduction and brief history 4 Geant 4 license 4 Highlights of recent developments 4 4 Kernel 4 EM physics 4 Hadronic physics User support processes Geant 4 - Status and Recent Developments M. Asai (SLAC) 2

General introduction and brief history Geant 4 - Status and Recent Developments M. Asai (SLAC)

What is Geant 4? 4 Geant 4 is the successor of GEANT 3, the world-standard toolkit for HEP detector simulation. 4 Geant 4 is one of the first successful attempt to re-design a major package of HEP software for the next generation of experiments using an Object-Oriented environment. 4 A variety of requirements have also taken into account from heavy ion physics, CP violation physics, cosmic ray physics, astrophysics, space science and medical applications. 4 In order to meet such requirements, a large degree of functionality and flexibility are provided. 4 G 4 is not only for HEP but goes well beyond that. Geant 4 - Status and Recent Developments M. Asai (SLAC) 4

Flexibility of Geant 4 4 In order to meet wide variety of requirements from various application fields, a large degree of functionality and flexibility are provided. 4 Geant 4 has many types of geometrical descriptions to describe most complicated and realistic geometries 4 4 CSG, BREP and Boolean solids 4 Placement, replica, divided, parameterized, reflected and grouped 4 XML interface Everything is open to the user 4 Choice of physics processes/models 4 Choice of GUI/Visualization/persistency/histogramming technologies Geant 4 - Status and Recent Developments M. Asai (SLAC) 5

Physics in Geant 4 4 4 Geant 4 offers 4 EM processes, 4 Hadronic processes, 4 Photon/lepton-hadron processes, 4 Optical photon processes, 4 Decay processes, 4 Shower parameterization, 4 Event biasing techniques, and 4 you can plug-in more. Geant 4 provides sets of alternative physics models so that the user can freely choose appropriate models according to the type of his/her application. 4 In other words, it is the user’s responsibility to choose reasonable set of physics processes/models that fits to his/her needs. 4 For example, some models are more accurate than others at a sacrifice of speed. Geant 4 - Status and Recent Developments M. Asai (SLAC) 6

Geant 4 – Its history 4 Dec ’ 94 - Project start 4 Apr ’ 97 - First alpha release 4 Jul ’ 98 - First beta release 4 Dec ’ 98 - First Geant 4 public release - version 1. 0 4 … 4 June 30 th, ’ 06 - Geant 4 version 8. 1 release 4 4 July 27 th, ’ 06 - Geant 4 8. 1 -patch 01 release Dec 15 th, ’ 06 - Geant 4 version 8. 2 release 4 Feb 23 rd, ’ 07 - Geant 4 8. 2 -patch 01 release 4 May 11 th, ’ 07 - Geant 4 version 8. 3 release 4 June 29 th, ’ 07 - Geant 4 version 9. 0 release (planned) 4 We currently provide two to three public releases every year. 4 Current version Bimonthly beta releases are available to the registered beta-testers. Geant 4 - Status and Recent Developments M. Asai (SLAC) 7

Geant 4 Collaboration TRIUMF Lebedev Collaborators also from nonmember institutions, including Budker Inst. of Physics IHEP Protvino MEPHI Moscow Pittsburg University J. W. Goethe Universität Geant 4 - Status and Recent Developments M. Asai (SLAC) 8

Geant 4 - Status and Recent Developments M. Asai (SLAC) 9

http: //top 25. sciencedirect. com/index. php? subject_area_id=21 Geant 4 - Status and Recent Developments M. Asai (SLAC) 10

Beam line and radiation protection Geant 4 - Status and Recent Developments M. Asai (SLAC) 11

GEANT 4 based proton dose calculation in a clinical environment: technical aspects, strategies and challenges Harald Paganetti Geant 4 - Status and Recent Developments M. Asai (SLAC) 12

Screen shots of g. Mocren http: //geant 4. kek. jp/g. Mocren/ Geant 4 - Status and Recent Developments M. Asai (SLAC) 13

Modeling of encapsulated 192 Ir source (Courtesy of Mc. Gill University) 3. 5 mm 1. 1 mm 0. 6 mm 5 mm 2 m Micro. Selectron Classic HDR source (part no. 080950) Geant 4 - Status and Recent Developments M. Asai (SLAC) 14

Hampton University (Collaboration: Proxima Therapeutics, de. Paul) Active Mammosite → Absolute real-time position measurement (within ± 1 mm) → Absolute real-time dose measurement → Modelization of the dose distribution using CT scan data & 4 D phantom Jacquelyn Winston, M. Sc. : Detector Rachel Black, Ph. D. : Detector, Geant 4 & VTK Geant 4 - Status and Recent Developments M. Asai (SLAC) 15

Geant 4 - Status and Recent Developments M. Asai (SLAC) 16

Radial dose and anisotropy functions of encapsulated source (Courtesy of Mc. Gill University) Radial dose function GEANT 4: ~0. 4% higher than Williamson and Li (Med. Phys. 22, 809 -819, 1995) Anisotropy function GEANT 4: ± 1% agreement with Williamson and Li Geant 4 - Status and Recent Developments M. Asai (SLAC) 17

Prostate brachytherapy - LDR 125 I source, Amersham 6711 Validation of the model: radial dose function J. -F. Carrier, Ph. D. project Geant 4 - Status and Recent Developments M. Asai (SLAC) 18

Octree geometry compression – DICOM images Examples: CT phantom + thorax patient Voxel number v/s DGT Geant 4 - Status and Recent Developments M. Asai (SLAC) 19

Comparison with commercial treatment planning systems M. C. Lopes 1, L. Peralta 2, P. Rodrigues 2, A. Trindade 2 1 IPOFG-CROC Coimbra Oncological Regional Center - 2 LIP - Lisbon CT images used to CT-simulation with a Rando phantom define the geometry: Experimental data obtained with TLD Li. F dosimeter a thorax slice from a Rando anthropomorphic phantom Agreement better than 2% between GEANT 4 and TLD dosimeters Geant 4 - Status and Recent Developments M. Asai (SLAC) 20

Geant 4 license Geant 4 - Status and Recent Developments M. Asai (SLAC)

The New Geant 4 License In response to user requests for clarification of Geant 4’s distribution policy, the collaboration recently announced a new license. • Makes clear the user’s wideranging freedom to use, extend or redistribute Geant 4, even as part of some for-profit venture. • The license was released along with the Geant 4 release 8. 1 in June 2006. • Simple enough that you can read and understand it. • http: //cern. ch/geant 4/license/Geant 4 - Status and Recent Developments (SLAC) M. Asai

The New Geant 4 License has 8 points. The points are written clearly and simply. 1, 2 and 3) tell the world who the software came from, and don’t claim you are us. Installation, use, reproduction, display, modification and redistribution of this software, with or without modification, in source and binary forms, are permitted on a non- exclusive basis. Any exercise of rights by you under this license is subject to the following conditions: 1. Redistributions of this software, in whole or in part, with or without modification, must reproduce the above copyright notice and these license conditions in this software, the user documentation and any other materials provided with the redistributed software. 2. The user documentation, if any, included with a redistribution, must include the following notice: "This product includes software developed by Members of the Geant 4 Collaboration ( http: //cern. ch/geant 4 ). " If that is where third-party acknowledgments normally appear, this acknowledgment must be reproduced in the modified version of this software itself. 3. The names "Geant 4” and “The Geant 4 toolkit” may not be used to endorse or promote software, or products derived therefrom, except with prior written permission by license@geant 4. org. If this software is redistributed in modified form, the name and reference of the modified version must be clearly distinguishable from that of this software. Geant 4 - Status and Recent Developments M. Asai (SLAC)

The New Geant 4 License 4) If you choose to give it away free to everyone, we can have it for free too. 5) You can’t patent the parts we did. 4. You are under no obligation to provide anyone with any modifications of this software that you may develop, including but not limited to bug fixes, patches, upgrades or other enhancements or derivatives of the features, functionality or performance of this software. However, if you publish or distribute your modifications without contemporaneously requiring users to enter into a separate written license agreement, then you are deemed to have granted all Members and all Copyright Holders of the Geant 4 Collaboration a license to your modifications, including modifications protected by any patent owned by you, under the conditions of this license. 5. You may not include this software in whole or in part in any patent or patent application in respect of any modification of this software developed by you. Geant 4 - Status and Recent Developments M. Asai (SLAC)

The New Geant 4 License We don’t claim that it works, and we’re not responsible if it doesn’t. 6. DISCLAIMER THIS SOFTWARE IS PROVIDED BY THE MEMBERS AND COPYRIGHT HOLDERS OF THE GEANT 4 COLLABORATION AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, IMPLIED WARRANTIES OF MERCHANTABILITY, OF SATISFACTORY QUALITY, AND FITNESS FOR A PARTICULAR PURPOSE OR USE ARE DISCLAIMED. THE MEMBERS OF THE GEANT 4 COLLABORATION AND CONTRIBUTORS MAKE NO REPRESENTATION THAT THE SOFTWARE AND MODIFICATIONS THEREOF, WILL NOT INFRINGE ANY PATENT, COPYRIGHT, TRADE SECRET OR OTHER PROPRIETARY RIGHT. 7. LIMITATION OF LIABILITY THE MEMBERS AND COPYRIGHT HOLDERS OF THE GEANT 4 COLLABORATION AND CONTRIBUTORS SHALL HAVE NO LIABILITY FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, CONSEQUENTIAL, EXEMPLARY, OR PUNITIVE DAMAGES OF ANY CHARACTER INCLUDING, WITHOUT LIMITATION, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES, LOSS OF USE, DATA OR PROFITS, OR BUSINESS INTERRUPTION, HOWEVER CAUSED AND ON ANY THEORY OF CONTRACT, WARRANTY, TORT (INCLUDING NEGLIGENCE), PRODUCT LIABILITY OR OTHERWISE, ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. 8. This license shall terminate with immediate effect and without notice if you fail to comply with any of the terms of this license, or if you institute litigation against any Member or Copyright Holder of the Geant 4 Collaboration with regard to this software. Geant 4 - Status and Recent Developments M. Asai (SLAC)

The New Geant 4 License That’s it. • Through the generous support of many governments and institutions, you, the community, have already paid for Geant 4. • We, the Geant 4 collaboration, want you to enjoy the software and use it where ever you can. • http: //cern. ch/geant 4/license/Geant 4 - Status and Recent Developments (SLAC) M. Asai

Highlights of recent developments - kernel 4 4 Scorer and filter classes Nested parameterization Parallel navigation Event biasing (variance reduction) Geant 4 - Status and Recent Developments M. Asai (SLAC) 27

Sensitive detector vs. primitive scorer Sensitive detector 4 You have to implement your own detector and hit classes. 4 One hit class can contain many quantities. A hit can be made for each individual step, or accumulate quantities. 4 Basically one hits collection is made per one detector. 4 Hits collection is relatively compact. Primitive scorer 4 Many scorers are provided by Geant 4. You can add your own. 4 Each scorer accumulates one quantity for an event. 4 4 G 4 Multi. Functional. Detector creates many collections (maps), i. e. one collection per one scorer. Keys of maps are redundant for scorers of same volume. I would suggest to : 4 Use primitive scorers 4 if you are not interested in recording each individual step but accumulating some physics quantities for an event or a run, and 4 if you do not have too many scorers. 4 Otherwise, consider implementing your own sensitive detector. Geant 4 - Status and Recent Developments M. Asai (SLAC) 28

List of provided primitive scorers Concrete Primitive Scorers ( See Application Developers Guide 4. 4. 6 ) 4 Track length 4 G 4 PSTrack. Length, G 4 PSPassage. Track. Length 4 Deposited energy 4 G 4 PSEnergy. Depsit, G 4 PSDose. Deposit, G 4 PSCharge. Deposit 4 Current/Flux 4 G 4 PSFlat. Surface. Current, G 4 PSSphere. Surface. Current, G 4 PSPassage. Current, G 4 PSFlat. Surface. Flux, G 4 PSCell. Flux, G 4 PSPassage. Cell. Flux 4 Others 4 G 4 PSMin. Kin. EAt. Generation, G 4 PSNof. Secondary, G 4 PSNof. Step Surface. Current : Surface. Flux : Cell. Flux : Count Sum up Sum of L / V of number of 1/cos(angle) of injecting particles in the geometrical cell. particles at defined surface angle at defined surface. L : Total step length in the cell. 4 V : Volume Geant 4 - Status and Recent Developments M. Asai (SLAC) 29

List of provided filter classes 4 4 4 G 4 SDCharged. Filter, G 4 SDNeutral. Filter 4 Accept only charged/neutral tracks, respectively G 4 SDKinetic. Energy. Filter 4 Accepts tracks within the defined range of kinetic energy G 4 SDParticle. Filter 4 Accepts tracks of registered particle types G 4 SDParticle. With. Energy. Filter 4 Accepts tracks of registered particle types within the defined range of kinetic energy G 4 VSDFilter 4 Abstract base class which you can use to make your own filter class G 4 VSDFilter { public: G 4 VSDFilter(G 4 String name); virtual ~G 4 VSDFilter(); public: virtual G 4 bool Accept(const G 4 Step*) const = 0; … Geant 4 - Status and Recent Developments M. Asai (SLAC) 30

For example… My. Detector. Construction: : Construct() { … G 4 Logical. Volume* my. Cell. Log = new G 4 Logical. Volume(…); G 4 VPhysical. Volume* my. Cell. Phys = new G 4 PVParametrised(…); G 4 Multi. Functional. Detector* my. Scorer = new G 4 Multi. Functional. Detector(“my. Cell. Scorer”); G 4 SDManager: : Get. SDMpointer()->Add. New. Detector(my. Scorer); my. Cell. Log->Set. Sensitive. Detector(my. Scorer); G 4 VPrimitive. Sensitivity* total. Surf. Flux = new G 4 PSFlat. Surface. Flux(“Total. Surf. Flux”); my. Scorer->Register(total. Surf. Flux); G 4 VPrimitive. Sensitivity* proton. Suf. Flux = new G 4 PSFlat. Surface. Flux(“Proton. Surf. Flux”); G 4 VSDFilter* proton. Filter = new G 4 SDParticle. Filter(“proton. Filter”); proton. Filter->Add(“proton”); proton. Surf. Flux->Set. Filter(proton. Filter); my. Scorer->Register(proton. Surf. Flux); } Geant 4 - Status and Recent Developments M. Asai (SLAC) 31

Nested parameterization 4 Suppose your geometry has three-dimensional regular reputation of same shape and size of volumes without gap between volumes. And material of such volumes are changing according to the position. 4 4 E. g. voxels made by CT Scan data (DICOM) Instead of direct three-dimensional parameterized volume, use replicas for the first and second axes sequentially, and then use onedimensional parameterization along the third axis. 4 It requires much less memory for geometry optimization and gives much faster navigation for ultra-large number of voxels. Geant 4 - Status and Recent Developments M. Asai (SLAC) 32

Parallel navigation 4 Occasionally, it is not straightforward to define sensitivity, importance or envelope to be assigned to volumes in the mass geometry. 4 4 Typically a geometry built machinery by CAD, GDML, DICOM, etc. has this difficulty. New parallel navigation functionality allows the user to define more than one worlds simultaneously. 4 4 New G 4 Transportation process sees all worlds simultaneously. A step is limited not only by the boundary of the mass geometry but also by the boundaries of parallel geometries. Materials, production thresholds and EM field are used only from the mass geometry. In a parallel world, the user can define volumes in arbitrary manner with sensitivity, regions with shower parameterization, and/or importance field for biasing. 4 Volumes in different worlds may overlap. Geant 4 - Status and Recent Developments M. Asai (SLAC) 33

New example. N 07 4 4 Mass geometry 4 sandwich of rectangular absorbers and scintilators Parallel scoring geometry 4 Cylindrical layers Geant 4 - Status and Recent Developments M. Asai (SLAC) 34

Moving objects 4 In some applications, it is essential to simulate the movement of some volumes. 4 4 E. g. particle therapy simulation Geant 4 can deal with moving volume 4 In case speed of the moving volume is slow enough compared to speed of elementary particles, so that you can assume the position of moving volume is still within one event. 4 Two tips to simulate moving objects : 1. Use parameterized volume to represent the moving volume. 2. Do not optimize (voxelize) the mother volume of the moving volume(s). Geant 4 - Status and Recent Developments M. Asai (SLAC) 35

Highlights of recent developments - EM physics 4 4 4 Revised multiple scattering algorithm and a new single scattering process Refinements in energy loss process Compton scattering - extended energy range Polarization Very low energy extension Geant 4 - Status and Recent Developments M. Asai (SLAC) 36

New multiple scattering 4 4 4 4 Step limit defined at first step and reevaluated after a boundary 4 applied only if range > safety step = fr. max (range, l) 4 new default fr = 0. 02 (instead of 0. 2) 4 strong constraint only for low energy particles ensure that a track always goes few steps in any volume (at least 3) step limit min becomes material dependant, via λ : 4 step limit min = max (0. 04 λ, 5 nm) Re-evaluate safety radius before to perform lateral displacement 4 d < safety (safety is often underestimated) Correlate final direction with lateral displacement 4 u∙d = f (l) taken from Lewis theory Angular distribution : both central part and tail slightly modified Single Coulomb scattering at boundaries 4 1 very small step (~ l elastic) before boundary crossing 4 apply approximate single Coulomb scattering in this step 4 reduce artifact step size dependence ? Geant 4 - Status and Recent Developments M. Asai (SLAC) 37

Result of upgrades 8. 1 7. 1 Geant 4 - Status and Recent Developments M. Asai (SLAC) 38

Electron scattering (L. Urban, CERN-OPEN-2006 -077, g 4 8. 2) Geant 4 - Status and Recent Developments M. Asai (SLAC) 39

Electron energy deposition in semi-infinite media (Sandia data, g 4 8. 1) Dose (Me. V/mm) (O. Kadri, 11 th Geant 4 workshop, Lisbon, 2006) 0. 521 Me. V e- in Al 0. 5 Me. V e- in Ta 4 configurations of EM physics, standard cuts and step limits R/R 0 Max diff 15% Al Ta Energy deposition precision better 3%; deviation in peak less than 10% Geant 4 - Status and Recent Developments M. Asai (SLAC) 40

Proton scattering (L. Urban) FWHM of projected angle NSS IEEE 2004 Conf. Rec. , Vol. 3, 1907 CERN-OPEN-2006 -077 Geant 4 - Status and Recent Developments M. Asai (SLAC) 41

Proton and ion stopping in water (QBBC Physics List) Dose deposition normalized to peak A. Bagulya et al. , 11 th Geant 4 workshop, Lisbon, 2006 Geant 4 - Status and Recent Developments M. Asai (SLAC) 42

Stopping powers of protons in Standard EM package in comparison with evaluated data NIST – 8. 1 ICRU – 7. 1 (A. Ivantchenko, V. Ivanchenko, 11 th Geant 4 workshop, Lisbon, 2006) Precision of evaluated data. Geant 4 about 2% and above 1 Developments Me. V and less below - Status Recent M. Asai (SLAC) 43

Comments on stopping powers 4 4 4 SRIM-2006 claims the systematic uncertainty better 5 % NIST claims the systematic uncertainty: 4 2 % at high energies 4 5 % at 1 Me. V 4 10 % at 10 – 100 ke. V 4 20 % below 10 ke. V Geant 4 stopping power is material dependent: 4 NIST materials allows to use the precise parameterization of stopping powers, which agrees both with NIST and SRIM’ 06 4 Hand-typed materials – ICRU parameterization Different level of agreement between NIST/ICRU/SRIM for 8. 1 4 E > 10 Me. V - 2% 4 0. 5 Me. V < E < 10 Me. V – 5% 4 E < 0. 5 Me. V – 20% for some materials much better 4 Better agreement for pure materials All parameterizations are within uncertainty Geant 4 - Status and Recent Developments M. Asai (SLAC) 44

Geant 4 - Status and Recent Developments M. Asai (SLAC) 45

Geant 4 - Status and Recent Developments M. Asai (SLAC) 46

Highlights of recent developments - Hadronic physics 4 4 4 Isotope dependency High precision neutron process New elastic scattering Geant 4 - Status and Recent Developments M. Asai (SLAC) 47

Isotope Dependence and Neutron HP 4 Isotope dependence 4 Users have always been able to build “custom” elements by choosing a specific combination of isotopes 4 4 the electromagnetic code respected this choice 4 the hadronic code ignored it, using instead natural abundances In Geant 4 8. 3 the hadronic code now properly calculates cross sections based on the user-defined isotope choice 4 High precision neutron code models capture, fission, elastic and inelastic neutron interactions for 20 Me. V down to thermal energies 4 depends on G 4 NDL database of cross sections and final state information 4 this list is rather large, but still not complete (some isotopic data is missing) Geant 4 - Status and Recent Developments M. Asai (SLAC) 48

Elastic Scattering 4 Continuous improvement of elastic scattering models since Geant 4 7. 1 4 The old GHEISHA-style model G 4 LElastic used non-relativistic scattering and parameterized the interactions based on that 4 New relativistically correct model now available but should not be used with the LHEP-based physics lists (upsets the parameterization) 4 A new unified elastic process, model and cross section data set are now available for physics lists other than LHEP-based (QGSP, etc. ) 4 G 4 UHadron. Elastic. Process 4 the new elastic scattering process which uses CHIPS parameterized cross sections (see below) for p, n incident on H and He 4 all other particles use original GHEISHA cross sections 4 good for all long-lived hadrons, deuterons, tritons, alphas 4 G 4 Hadron. Elastic 4 a new elastic scattering model which uses coherent elastic scattering at high energies (> 1 Ge. V) 4 G 4 QElastic. Cross. Section 4 new hadron elastic cross section data set based on the CHIPS ( chiral invariant phase space) parameterization of cross section data Geant 4 - Status and Recent Developments M. Asai (SLAC) 49

User support processes Geant 4 - Status and Recent Developments M. Asai (SLAC)

User Support 4 Geant 4 Collaboration offers extensive user supports. 4 Users workshops 4 Tutorial courses 4 Hyper. News and mailing list 4 Bug reporting system 4 Requirements tracking system 4 Daily “private” communications 4 Technical Forum http: //cern. ch/geant 4/ Geant 4 - Status and Recent Developments M. Asai (SLAC) 51

Geant 4 users workshop 4 Users workshops were held or are going to be held hosted by several institutes for various user communities. 4 KEK - Dec. 2000, Jul. 2001, Mar. 2002, Jul. 2002, Mar. 2003, Jul. 2004, Jan. 2005, Jan. 2006 4 SLAC - Feb. 2002 4 Spain (supported by INFN) - Jul. 2002 4 CERN - Nov. 2002 4 NASA/ESA/Vanderbilt - Jan. 2003, May. 2004, Mar. 2005, Oct. 2005, Nov. 2006 4 Helsinki - Oct. 2003, Jun. 2005 4 Bordeaux - Nov. 2005 4 Hebden Bridge (U. K. ) - Sep. 2007 4 Local workshops of one or two days were held or are planned at several places. Refer to our web site. Geant 4 - Status and Recent Developments M. Asai (SLAC) 52

Geant 4 tutorials / lectures 4 4 4 In addition to the users workshops, many tutorial courses and lectures with some discussion time slots were held for various user communities. 4 CERN School of Computing 4 Italian National School for HEP/Nuclear Physicists 4 MC 2000 4 MCNEG workshop 4 IEEE NSS/MIC 4 KEK, SLAC, DESY, FNAL, INFN, Frascati, Karolinska, Gran. Sasso, etc. 4 ATLAS, CMS, LHCb 4 Tutorials/lectures at universities 4 Italy - Genoa, Bologna, Udine, Roma, Trieste, … 4 U. K. - Imperial 4 U. S. /Canada – Vanderbilt, Mc. Gill Geant 4 collaboration is happy to offer tutorial courses if requested. SLAC Geant 4 team is offering tutorial courses regularly. 4 http: //geant 4. slac. stanford. edu/ Geant 4 - Status and Recent Developments M. Asai (SLAC) 53

Hyper. News 4 Hyper. News system was set up in April 2001 Geant 4 - Status and Recent Developments M. Asai (SLAC) 54

Hyper. News 4 4 24 categories Not only “user-developer”, but also “user-user” information exchanges are quite intensive. Geant 4 - Status and Recent Developments M. Asai (SLAC) 55

Geant 4 North American Medical Users Organization - G 4 NAMU Launched in May of 2005 to provide a meeting place for the rapidly growing Geant 4 medical user community of North America • Bring this community together to share issues and advice, to develop regional collaboration and to communicate as a group to the Geant 4 developers. • Current membership includes 79 members from 37 institutions throughout Canada and the United States • http: //geant 4. slac. stanford. edu/g 4 namu/ Geant 4 - Status and Recent Developments M. Asai (SLAC)