Corso per l’utilizzo del codice GEANT4 in campo medico

Catania, 12-14 Ottobre 2009

Barbara Caccia

Stéphane Chauvie

Istituto Superiore di Sanità, RomaSanta Croce e Carle Hospital, Cuneo

CT data: Monte Carlo and DICOM standard

Radiotherapy Tretment planning

Patient

Medical accelerator

Patient!Patient!

PatientPatient

For Geant4 patient is a detector: materials

+

geometry

G4Material: compound G4Material: compound G4Material: compound 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);

ExampleExample: : gasgasExampleExample: : gasgas

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 geometryDefine detector geometryDefine detector geometryDefine 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 patientNothing could describe a single patient

Parameterised Physical VolumesParameterised Physical VolumesParameterised Physical VolumesParameterised Physical VolumesUser 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

G4PVParameterisedG4PVParameterisedG4PVParameterisedG4PVParameterisedG4PVParameterised(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 volumeThe 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 objectAlternative constructor using pointer to physical volume for the mother

Dose calculation: CTDose calculation: CT

Hounsfield UnitsHounsfield Units

Segnale su detettori TAC

ρel= ρ NA Z/A

Hounsfield UnitsHounsfield Units

Spettro non monocromatico

We must determine:

mass density ρ

and elemental

composition wi

VisualizationVisualization

Material HU interval

Air [−1000:−950]

Water/tissue [−950:125]

ICRP cortical bone [125: 2000]

Steel 3095

CQ: uniformityCQ: 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 numbersCQ: CT numbers

Inserti di differente materiale

con numeri CT variabili nel

range di interesse

CT numbers linearityCT numbers linearity

INTEROPERABILITY & CONNECTIVITY

RadiotherapyRadiotherapy

Nuclear medcineNuclear medcineRadiologyRadiology

Medical PhysicsMedical Physics

CTCT RMRM SPECTSPECT

CTCT

PETPETDRDR

SimulatorSimulator

HIS/RIS/PACS

DICOM classDICOM classImage StorageImage Storage

Query / retrieveQuery / retrieve

PrintPrint

Worklist ModalityWorklist Modality

Performed Procedure Performed Procedure ModalityModality

DICOM objectDICOM objectCT, MR, NM, PT, SC, US, CT, MR, NM, PT, SC, US,

XA, DR….XA, DR….

The DICOM StandardThe 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 InterchangeMedia Interchange

Print ImagesPrint Images

Print ManagementPrint Management

Image Related Workflow andImage Related Workflow andInformation ManagementInformation Management

Query RequestQuery Request

Image Related Image Related Information TransferInformation Transfer

Persistent Object StoragePersistent Object Storage

Persistent Object StoragePersistent Object Storage

Retrieve Retrieve RequestRequest

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 Image ModuleModule

Patient Patient ModuleModule

General General Study Study

ModuleModule

Patient Patient Study Study

Module*Module*

General General Series Series

ModuleModule

Frame of Frame of Reference Reference ModuleModule

General General Equipment Equipment

ModuleModule

General General Image Image

ModuleModule

Image Image Plane Plane

ModuleModule

ContrasContrast/Bolus t/Bolus ModuleModule

Overlay Overlay Plane Plane

Module*Module*

VOI VOI LUT LUT

ModuleModule**

SOP SOP CommoCommo

n n ModuleModule

Image Image Pixel Pixel

ModuleModule

Image Pixel Image Pixel ModuleModule

Image Pixel Image Pixel ModuleModule

Row/Col SizeRow/Col SizePhotometric InterpretationPhotometric Interpretation

Row/Col SizeRow/Col SizePhotometric InterpretationPhotometric Interpretation

Patient Patient InformationInformation

Study Study InformationInformation

Series Series InformationInformation

(Image) Information

InstanceInstance

Information

Entities

Modules Attributes

Network Addressing with DICOM Handshake Requirements

ID: CT_AE1IP: 10.3.253.8Port: 104

ID: WK_AE1IP: 10.3.253.9Port: 4006

IP Addr AE Title Port #

10.3.253.1 Fusion 104

10.3.253.9 WK_AE1 4006

IP Addr AE Title Port #

10.3.253.1 Fusion 104

10.3.253.8 CT_AE1 104

Association / Association / NegotiationNegotiation

CT Config FileCT Config File Wkstn Config FileWkstn Config File

Node Level Node Level SecuritySecurity

Typical Network Flow

DICOM AE “A”DICOM AE “A” DICOM AE “B”DICOM AE “B”A-ASSOCIATE-RQA-ASSOCIATE-RQ

A-ASSOCIATE-ACA-ASSOCIATE-AC

A-RELEASE-RSPA-RELEASE-RSP

A-RELEASE-RQA-RELEASE-RQ

Only The AE Which Initiated The Association May Release ItOnly The AE Which Initiated The Association May Release ItHowever, Either May Initiate An A-ABORTHowever, Either May Initiate An A-ABORT

Only The AE Which Initiated The Association May Release ItOnly The AE Which Initiated The Association May Release ItHowever, Either May Initiate An A-ABORTHowever, Either May Initiate An A-ABORT

ororA-ASSOCIATE-RJA-ASSOCIATE-RJ

DICOM MessagesDICOM Messages

ororA-ABORTA-ABORTEither AEEither AE