Corso per l’utilizzo del codice GEANT4 in campo medico Catania, 12-14 Ottobre 2009

1. CT data: Monte Carlo and DICOM standard Corso per l’utilizzo del codice GEANT4 in campo medico Catania, 12-14 Ottobre 2009 Barbara Caccia Stéphane Chauvie Istituto Superiore di Sanità, Roma Santa Croce e Carle Hospital, Cuneo

2. Radiotherapy Tretment planning Medical accelerator Patient

3. Patient!

4. Patient For Geant4 patient is a detector: materials + geometry

6. G4Material: compound • Compound: composition by fraction of mass a = 14.01*g/mole; G4Element* elN = new G4Element(name="Nitrogen",symbol="N",z= 7.,a); a = 16.00*g/mole; G4Element* elO = new G4Element(name="Oxygen",symbol="O",z= 8.,a); density = 1.290*mg/cm3; G4Material* Air = new G4Material(name="Air",density,ncomponents=2); Air->AddElement(elN, 70.0*perCent); Air->AddElement(elO, 30.0*perCent);

7. Example: gas • It may be necessary to specify temperature and pressure • (dE/dx computation affected) G4double density = 27.*mg/cm3; G4double temperature = 325.*kelvin; G4double pressure = 50.*atmosphere; G4Material* CO2 = new G4Material(“CarbonicGas", density, ncomponents=2 kStateGas, temperature, pressure); CO2->AddElement(C,natoms = 1); CO2->AddElement(O,natoms = 2);

8. Define detector geometry • Three conceptual layers • G4VSolid -- shape, size • G4LogicalVolume -- daughter physical volumes, material, sensitivity, user limits, etc. • G4VPhysicalVolume -- position, rotation G4VSolid G4LogicalVolume G4VPhysicalVolume G4Material G4Box G4VisAttributes G4PVPlacement G4VSensitiveDetector G4Tubs G4PVParameterised

9. Nothing could describe a single patient

10. User written functions define: the size of the solid (dimensions) Function ComputeDimensions(…) where it is positioned (transformation) Function ComputeTransformations(…) Optional: the type of the solid Function ComputeSolid(…) the material Function ComputeMaterial(…) Limitations: Applies to simple CSG solids only Daughter volumes allowed only for special cases Very powerful Consider parameterised volumes as “leaf” volumes Parameterised Physical Volumes

11. G4PVParameterised G4PVParameterised(const G4String& pName, G4LogicalVolume* pCurrentLogical, G4LogicalVolume* pMotherLogical, const EAxis pAxis, const G4int nReplicas, G4VPVParameterisation* pParam); • Replicates the volume nReplicas times using the parameterisation pParam, within the mother volume • The positioning of the replicas is dominant along the specified Cartesian axis • If kUndefined is specified as axis, 3D voxelisation for optimisation of the geometry is adopted • Represents many touchable detector elements differing in their positioning and dimensions. Both are calculated by means of a G4VPVParameterisation object • Alternative constructor using pointer to physical volume for the mother

12. Dose calculation: CT

13. Hounsfield Units Segnale su detettori TAC ρel= ρ NA Z/A

14. Hounsfield Units Spettro non monocromatico We must determine: mass densityρ and elemental composition wi

15. Visualization

16. CQ: uniformity Confronto tra numero CT medio di una ROI al centro del fantoccio con quello delle ROI ai bordi del fantoccio Valutazione della graduale variazione dei numeri CT in un fantoccio omogeneo

17. CQ: CT numbers Inserti di differente materiale con numeri CT variabili nel range di interesse

18. CT numbers linearity

19. DICOM object Simulator CT, MR, NM, PT, SC, US, XA, DR…. DR PET RM CT CT DICOM class Image Storage Query / retrieve Print Worklist Modality Performed Procedure Modality INTEROPERABILITY & CONNECTIVITY Radiotherapy Radiology Nuclear medcine SPECT Medical Physics HIS/RIS/PACS

20. The DICOM Standard DICOM covers: • Communication protocols over networks • File formats (on different types of media) • Information Object Definitions (content) • Services (functionality) • Grayscale display • Security • Hanging protocols • Structured reporting • Etc.

21. DICOM Functional Groupings Image Related Workflow and Information Management Image Related Information Transfer Persistent Object Storage Query Request Retrieve Request Persistent Object Storage Print Management Media Interchange Print Images

22. DICOM Transfer overNetwork & Media D I C O M [ . . . . . . . F I L E . . . . . . . . . . ] Media Transfer = Meta Data + Data Set Group 2 ( Describes Data Set) Patient Name Patient ID Rows Columns Bits Stored … Header Image Group 0( Describes Service: C-Store) Network Transfer = Command + Data Set D I C O M [ . . . . . M E S S A G E . . . . . . . ]

23. DICOM Information Object Definitions Information Entities Modules Attributes Image Pixel Module Patient Module Patient Information Row/Col Size Photometric Interpretation General Study Module Patient Study Module* Study Information Series Information Frame of Reference Module General Series Module General Equipment Module Instance (Image) Information Image Plane Module Image Pixel Module Contrast/Bolus Module General Image Module VOI LUT Module* Overlay Plane Module* Image Module SOP Common Module

24. Network Addressing with DICOM Handshake Requirements Association / Negotiation ID: CT_AE1IP: 10.3.253.8Port: 104 ID: WK_AE1IP: 10.3.253.9Port: 4006 CT Config File Wkstn Config File Node Level Security

25. Typical Network Flow DICOM AE “B” DICOM AE “A” A-ASSOCIATE-RQ A-ASSOCIATE-AC or A-ASSOCIATE-RJ DICOM Messages A-RELEASE-RQ A-RELEASE-RSP or A-ABORT Either AE Only The AE Which Initiated The Association May Release It However, Either May Initiate An A-ABORT