Anthropomorphic Phantoms Analytical and voxel models Status and perspectives

1. Anthropomorphic PhantomsAnalytical and voxel models Status and perspectives Giorgio Guerrieri July 13th, 2005

2. Mathematical phantoms The size and shape of the body and its organs are described by mathematical expressions representing combinations and intersections of planes, circular and elliptical cylinders spheres, cones, tori, … Voxel phantoms Based on digital images recorded from scanning of real persons by computer tomography (CT) or magnetic resonance imaging (MRI). NRPB Mathematical Phantom (National Radiological Protection Board) Gibbs Phantom (1984) NORMAN Phantom (MRI data of a volunteer) MIRD5 Phantom (Medical Internal Radiation Dose Committee, pamphlet no 5) Zubal Phantom (from CT and MRI data) ORNL Phantom (Oak Ridge National Laboratory) Missing in Geant4 Already developed by other group using Geant4, not public A wide panorama of phantoms

3. Interest on Anthropomorphic Phantoms 2005, April: Monte Carlo Topical Meeting, Tennessee In the session about “Tomographic Models for Radiation Protection Dosimetry”, many talks about anthropomorphic phantom (mainly voxel-based models) have been presented: - GSF Male And Female Adult Voxel Models Representing ICRP Reference Man By Keith Eckerman - Effective Dose Ratios For The Tomographic Max And Fax Phantoms By Richard Kramer - Reference Korean Human Models: Past, Present and Future By Choonsik Lee - The UF Family of Paediatric Tomographic Models By Wesley Bolch and Choonik Lee - Development And Anatomical Details Of Japanese Adult Male/ Female Voxel Models By T. Nagaoka - Dose Calculation Using Japanese Voxel Phantoms For Diverse Exposures By Kimiaki Saito - Stylized Versus Tomographic Models: An Experience On Anatomical Modelling At RPI By X. George Xu - Use Of MCNP With Voxel-Based Image Data For Internal Dosimetry Applications By Michael Stabin - Application Of Voxel Phantoms For Internal Dosimetry At IRSN Using A Dedicated Computational Tool By Isabelle Aubineay-Laniece - The Use Of Voxel-Based Human Phantoms In FLUKA By Larry Pinsky - The Future Of Tomographic Modelling In Radiation Protection And Medicine (Panel discussion)

4. Anthropomorphic Phantoms for Geant4 toolkit • The representation of the human body is useful for radiation protection and medical physic simulation applications. In particular for applications in radiation shielding of habitats for astronauts, such as transfer vehicles and surface habitats for future manned exploration missions. The development of anthropomorphic phantoms, together with Geant4 physics modelling, makes possible to study the radiation damage to the astronauts' organs during interplanetary missions. • The models of anthropomorphic phantoms can be used not only in space science, but also for cancer therapy studies too.

5. First Step Analytical Phantom DICOM interface Voxel Phantom Anthropomorphic Phantoms for Geant4 toolkit The project for Geant4 toolkit is addressed to develop anthropomorphic phantom that can beentirelycustomized by the user. As in URD, the user shall be able to: - Choose model for each body part to add to the phantom (ORNL, MIRD) - Add single voxel-based body part from DICOM file (CT, MRI)

6. First attempts to model the shape of a human being and its internal organs in order to calculate absorbed radiation doses were made by Snyder et al. (1969) and Koblinger (1972). These were based on the anthropomorphic MIRD-type phantom, which was originally developed for the dosimetry of internal radionuclide sources. The Medical Internal Radiation Dose Committee creates MIRD5 that has been the basis for various derivations, like the ORNL Mathematical Phantom Series. W. S. Snyder, M. R. Ford, G. G. Warner, H. L. Fisher jr MIRD Pamphlet # 5 Revised: “Estimates of absorbed fraction for monoenergetic photon sources uniformly distributed in various organs of a heterogeneous phantom”, J Nucl Med Suppl 3, 1969. K. F. Eckerman, M. Cristy, J. C. Ryman “The ORNL Mathematical Phantom Series”, http://homer.ornl.gov/vlab/VLabPhan.html Analytical Model The anatomies of new-born, and children of age 1 year, 5 year, 10 year, 15 year and adult male and female had been modelled at the Oak Ridge National Laboratory by Cristy and Eckerman (1987).

7. Sketch of the gastrointestinal tract model Skeletal system An example of how MIRD5 describes brain Exterior of the phantom Brain Modelling with geometries

8. The sizes and the positions of geometrical representations of body parts are taken from the document: ORNL Mathematical Phantom Series From ORNL Series: model of trunk as elliptical cylinder This document allows to create different phantoms choosing its age and sex. Back view Front view “Final” result

9. Body regions Trunk, neck, head, legs, male genitalia, breasts Skeletal systemLeg bones, arm bones, pelvis, spine, skull, rib cage, clavicles, scapulae Gastrointestinal tract and contentsEsophagus (thoracic + abdominal portions),stomach (wall + contents), small intestine, upper large intestine (ascending colon wall and contents, transverse colon wall and contents), lower large intestine (descending colon wall and contents, lower large sigmoid colon wall and contents) Heart and contents Outer surface of heart, left ventricle (wall + contents), right ventricle (wall + contents), left atrium (wall + contents), right atrium (wall + contents), heart (wall + contents) Organs Adrenals, brain, gall bladder (wall + contents), kidney, liver, lung,ovary, pancreas, spleen, testes, thymus, lobes of thyroid, urinary bladder (wall + contents), uterus Anthropomorphic Phantom: URD (1) - The goal of the project is the development of a Geant4 package addressed to the modelingof an anthropomorphic phantom providing a realistic description of the human body and anatomy. - The phantom consists of a mathematical model of:

10. Anthropomorphic Phantom: URD (2) Elemental composition of tissues: • The user shall be able to define composition of each tissue • The user shall be able to associate a defined material to each part of phantom Event: • The user shall be able to retrieve the position and material of the body region traversed by tracks User interface: • The user shall be able to select a phantom by the sex, the age, the model • The user shall be able to construct a phantom using single parts from different models by choosing among MIRD, ORNL or Voxel (from CT/MRI DICOM data) • The user shall be able to add sensitivity to specific organs • The user shall be able to create specific body region corresponding to subset of the phantom Visualization: • The user shall be able to visualize the geometrical set-up • The user shall be able to visualize the particle tracks

11. Anthropomorphic Phantom: Design • The anthopomorphic phantom will be implemented exploiting the object oriented technology • A rigorous software process is adopted. • The object oriented technology allows extensive code reuse, flexibility, easy extension of the software.

12. Abstract Factory • The design pattern Abstract Factory is adopted to define anatomic structures. • The user can model organs communicating with the abstract interface G4VBodyFactory, independently from their concrete classes. The Abstract Factory provides an interface for creating families of related object without specifying their concrete classes. It makes exchanging product families easy. It can use different product configurations simply by changing the concrete factory.

13. Builder The creational pattern Builder separates the construction of a complex object from its representation so that the same construction process can create different representations. The Builder object provides the director with an abstract interface for constructing the product. Thanks to the abstract interface G4VPhantomBuilder, all one has to do to change the product's internal representation is define a new kind of builder. Unlike creational patterns that construct products in one shot, the Builder pattern constructs the product step by step under the director's control.

14. In both ORNL and MIRD mathematical phantoms most of the organs can be easily approximated with solids or part of them that currently are not implemented in the Geant4 Geometry Package: • Ellipsoid • Circular and elliptical oblique cone • Elliptical cone • Torus with elliptical section Problems …

15. Geant4 functionality has to be extended, developing the software to describe the ellipsoid Design of the new class G4Ellipsoid G4Ellipsoid The ellipsoid and part of it are used to describe several organs like stomach, ovaries, brain, or lungs and kidneys...

16. 1-Dimensional Test This test consisted of 1D-flux of geantinos with direction parallel to X axis impinging onto an ellipsoid. The ellipsoid has semi-axis lengths: a = 7. µm , b = 10. µm, c = 15. µm. The solid is spaced in an enclosed box volume defined world which sizes are 40.µm. The number of events generated in the test is 10^4. The same test was performed for 1D-beams with direction parallel to Y and Z directions. The path length of the geantinos was verified to be equal to the sizes of the ellipsoid, as expected. Path Length

17. 2-Dimensional Test This test consisted of an isotropic flux of geantinos impinging onto an ellipsoid. The ellipsoid has semi-axis lengths: a = 7. µm, b = 10. µm, c = 15. µm. The solid is spaced in an enclosed box volume defined world which sizes are 40 µm. The number of the events generated in the test is 5 ·10^5. Projection on plane XY, YZ, ZX

18. Ellipsoid cut by two planes along the Z-axis The software implementing the ellipsoid has been included in Geant4 CVS repository in Geometry/solids/specifics. This work will be documented by an INFN pre-print (in progress) G4Ellipsoid The new class G4Ellipsoid is meant to be publicly available in the next Geant4 release.

19. Solids CSG solids: - box - tube - cone - sphere - parallelepiped - trapezoid - general trapezoid Boolean solids: - union - subtraction - intersection Materials Materials definitions - isotopes - elements - elements built from isotopes - complex materials - molecules - mixtures built from elements and/or other complex materials by fractional mass Numerical expressions Actual definitions of numerical elements: - constant - quantity - expression - Cartesian position and rotation GDML Geometry Description Markup Language The Geometry Description Markup Language work-package is meant to provide geometry data exchange format for the LCG applications. The work-package consists of the GDML Schema part, which is a fully self-consistent definition of the GDML syntax, and the GDML I/O part, which provides means for writing out and reading in GDML files. What users gain is the reduced time when writing their geometry description as no need for re-compilation and re-linking of their applications is required even for one number change. The other advantage is that it allows them easy exchange of geometry data without a need to reveal their source code and makes life easier for developers as well because they can use the GDML data for tracing bugs and problems in geometry processing code. The GDML work-package can be useful for simplify geometry description of body parts

20. The GDML work-package read out geometries implemented in Geant4. If other solids will be implemented (the ellipsoid...) in the Geant4 Geometry Package, the GDML Processor is to be extended with them. • Currently GDML can create volumes parametrized and replica only of boxes and tubes. [UR 1.2.10] The rib cage is represented by a series of bands between two concentric, right vertical, elliptical cylinder. Problems …

21. The GDML Schema has been extended with the new solid, the ellipsoid, and the GDML Processor is now able to draw ellipsoid. The next official GDML distribution will have the extension to read the new solid (once the G4Ellipsoid is available in G4 release) http://simu.cvs.cern.ch/cgi-bin/simu.cgi/simu/GDML2/GDMLSchema/ The GDML package has been extended to create volumes parametrized for the elliptical tube. Extending GDML

22. Implementation of an anthropomorphic phantom example We have explored GDML functionality for a preliminary implementation of an example of an analytical anthropomorphic phantom. Elements of “Human phantom” example: • Primary Particle • Geometry • Physics • Messengers

23. Definition of primary particle type, primary vertex and momentum Primary particle can be originated in different conditions - The user can choose the type of particle - The user can originate beam with defined energy and initial direction - The user can originate particle from a sphere (isotropic flux) Primary Particle

24. The Geometry is generated from a GDML file through GDML Processor GDML file is created by the user, through User Interface. - The user can choose phantom by sex (Male or Female) - The user can choose phantom by model (ORNL, MIRD or MIX) - The user can choose which body part is to be built - The user can set sensitivity for each body part Geometry

25. Materials Materials are defined in GDML file There are three materials defined for different body parts: - Skeleton: for the parts of skeleton system - Lung: for the lungs - Soft Tissue: for all other body part These are defined by their elemental composition and densities.

26. The body parts can be sensible volumes In body part volume the energy deposit is collected The energy deposit is given by the primary particles and all the secondaries generated. Sensitive Body Part

27. Geant4 phantom has messengers to control: - Visualizations (OPENGL, VRML, DAWN) - Primary Particles in term of initial energy and direction - Geometry set-up Messengers

28. <?xml version="1.0" encoding="UTF-8" ?> <gdml xmlns:gdml="http://cern.ch/2001/Schemas/GDML" ... <define> (...) </define> <materials> (...) </materials> <solids> (...) </solids> <structure> (...) <volume name="BreastsVolume" > <materialref ref="SoftTissue" /> <solidref ref=”BreastsVolume” /> </volume> <volume name="BodyVolume" > <materialref ref="SoftTissue" /> <solidref ref="Body" /> <physvol> <volumeref ref="BrainORNLVolume" /> <positionref ref="BrainORNLPos" /> <rotationref ref="BrainORNLRot" /> </physvol> (...) </volume> (...) Through macro file adultFemale.mac # Initialize Phantom /phantom/startUserPhantom # Define Sex /phantom/setUserPhantomSex Female # Define Model /phantom/setUserPhantomModel ORNL # Body part and Sensitivity /bodypart/addBodyPart Stomach yes /bodypart/addBodyPart Spleen no /bodypart/addBodyPart Brain yes ... # Finalize GDML file /phantom/closeUserPhantom Set sensitivity GDML file is processed by GDML Processor and the user phantom is built... Example of geometry setup

29. Female ORNL Anthropomorphic Phantom

30. Female ORNL Anthropomorphic Phantom Skull Spine Thyroid Esophagus Lungs Arm Bones Breasts Spleen Heart Pancreas Stomach Liver Kidneys Upper Large Intestine Pelvis Ovaries Uterus Lower Large Intestine Urinary Bladder Leg Bones Not visible: Brain (in the skull)

31. TrackID: 2 -> LegBonesORNLVolume -> Energy deposit: 3.4576726 MeV TrackID: 2 -> BodyVolume -> Energy deposit: 5.1323606 MeV TrackID: 2 -> BodyVolume -> Energy deposit: 5.1711365 MeV TrackID: 2 -> BodyVolume -> Energy deposit: 701.06096 keV TrackID: 16 -> BodyVolume -> Energy deposit: 807.59738 keV TrackID: 23 -> BodyVolume -> Energy deposit: 1.497982 keV TrackID: 22 -> BodyVolume -> Energy deposit: 2.3391091 keV TrackID: 21 -> BodyVolume -> Energy deposit: 220.25512 eV TrackID: 20 -> BodyVolume -> Energy deposit: 10.468365 keV TrackID: 19 -> LegBonesORNLVolume -> Energy deposit: 16.651015 keV TrackID: 24 -> BodyVolume -> Energy deposit: 4.0614721 keV Female ORNL Anthropomorphic Phantom> Run 1 < Particle: gamma Energy: 100. MeV no. Particle: 20 Beam Direction: along Z axis Visualization system: OpenGL Output of run 1

32. TrackID: 19 -> ArmBonesORNLVolume -> Energy deposit: 2.148 keV TrackID: 34 -> ArmBonesORNLVolume -> Energy deposit: 70.168538 keV TrackID: 33 -> BodyVolume -> Energy deposit: 19.493675 keV TrackID: 32 -> BodyVolume -> Energy deposit: 42.318809 keV TrackID: 31 -> SpleenORNLVolume -> Energy deposit: 119.96815 keV TrackID: 30 -> SpleenORNLVolume -> Energy deposit: 3.9230135 MeV TrackID: 29 -> PancreasORNLVolume -> Energy deposit: 1.0284905 MeV TrackID: 18 -> BodyVolume -> Energy deposit: 543.1 eV TrackID: 37 -> BodyVolume -> Energy deposit: 33.841459 keV TrackID: 36 -> LiverORNLVolume -> Energy deposit: 986.16275 eV TrackID: 35 -> LiverORNLVolume -> Energy deposit: 1.9230902 keV Female ORNL Anthropomorphic Phantom> Run 2 < Particle: gamma Energy: 100. MeV no. Particle: 20 Beam Direction: along X axis Visualization system: OpenGL Output of run 2

33. A first model of analytical anthropomorphic phantom has been created for Geant4 simulation toolkit Conclusions • A new solid ellipsoid has been designed, implemented and tested to extend the Geant4 geometry package.The solid enables the representations of many body parts. • GDML work-package has been extended and now it's able to read the ellipsoid from Geant4 geometry and to create volumes parametrized of elliptical tube. • GDMLwork-package seems to be useful to simplify the geometry description of the analytical anthropomorphic phantom.

34. Analytical Phantom Organs Customized Phantom DICOM interface Future • Development of a prototype of analytical anthropomorphic phantom to be used in simulation applications of radioprotection study or medical physics. • Allow user to build customized anthropomorphic phantom with organs described by analytical model and DICOM interfacecreating a voxel-analytical phantom.

35. Anthropomorphic PhantomsAnalytical and voxel models Status and perspectives Giorgio Guerrieri July 13th, 2005