Corso per lutilizzo del codice GEANT4 in campo medico Catania, Ottobre 2009 Barbara Caccia Stéphane Chauvie Istituto Superiore di Sanità, Roma Santa Croce e Carle Hospital, Cuneo CT data: Monte Carlo and DICOM standard

Radiotherapy Tretment planning Patient Medical accelerator

Patient!

Patient For Geant4 patient is a detector: materials + geometry

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);

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);

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

Nothing could describe a single patient

Parameterised Physical Volumes 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

G4PVParameterisedG4PVParameterised 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

Dose calculation: CT

Hounsfield Units Segnale su detettori TAC ρ el = ρ N A Z/A

Hounsfield Units Spettro non monocromatico We must determine: mass density ρ and elemental compositio n w i

Visualization MaterialHU interval Air[1000:950] Water/tissue[950:125] ICRP cortical bone[125: 2000] Steel3095

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

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

CT numbers linearity

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

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.

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

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

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

Network Addressing with DICOM Handshake Requirements ID: CT_AE1 IP: Port: 104 ID: WK_AE1 IP: Port: 4006 IP AddrAE TitlePort # Fusion WK_AE14006 IP AddrAE TitlePort # Fusion CT_AE1104 Association / Negotiation CT Config File Wkstn Config File Node Level Security

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