Virtual CT Simulator QA 2 topics Electromechanical. Virtual Simulator CT QA. What is Virtual CT Simulator (VSim)? Original Simulators

Size: px

Start display at page:

Download "Virtual CT Simulator QA 2 topics Electromechanical. Virtual Simulator CT QA. What is Virtual CT Simulator (VSim)? Original Simulators"

Loraine Shelton
7 years ago
Views:

1 Virtual CT Simulator QA 2 topics Electromechanical Virtual Simulator CT QA Virtual CT simulation software Performance and Image quality Alex Markovic, PhD Director, Medical Radiation Physics Program, Rosalind Franklin University, North Chicago, IL Lead Therapeutic Physicist, NorthShore University Health System, Evanston, IL CT operator console Alex Prasad 2 Original Simulators What is Virtual CT Simulator (VSim)? TG66:Quality assurance for computed-tomography simulators and the computed tomographysimulation process X ray tube A virtual simulator is a set of software which recreates the treatment machine and which allows import, manipulation, display, and storage of images from CT and/or other imaging modalities. Image intensifier 3 4

Simulators What is Virtual CT Simulator (VSim)?

2 Examples of VSim software packages: Varian SomaVision GE Advantage SIM Elekta Group - CMS Focal Phillips AcQSim 3 Siemens syngo RT Oncologist Phillips AcQSim VSim Software Features DRR generation Automatic structure segmentation Interpolation of contours Manual and semi-automatic (eg. smart brush ) contouring tools Volume expansion to apply margins 4D Visualization of organ motion Isocenter placement, design of treatment fields Moving laser support 5 6 Advantages of VSim Relevant Guidance Documents No guidance document dedicated to Vsim QA Efficient workflow Doctors are usually present during the CT scan Good time to have them complete their contouring and planning work. Poor scans can be repeated Doctors work is less likely to be delayed Vsim software can be installed on doctor s PC or can be accessed through Citrix TG 2(1993): Specification and acceptance testing of CT scanners TG 53(1998) QA of treatment planning NCRP report #99: Quality Assurance for Diagnostic Imaging TG 66 (2003): QA for CT-simulators and CT simulation process TG 117 (in progress): The Use of MRI Data in Treatment Planning and Stereotactic Procedures Spatial Accuracy and Quality Control Procedures TG132 (In progress): Use of Image Registration and Data Fusion Algorithms and Techniques in Radiotherapy 7 Treatment Planning 8

smart brush ) contouring tools Volume expansion to apply margins 4D Visualization of organ motion Isocenter placement, design of treatment fields Moving laser support 5 6 Advantages of VSim Relevant

3 Why Perform QA on the VSim? Ensure data to and from VSim transfers correctly Reduce possibility of treatment errors due to inaccurate transfer of data Ensure complete dataset is sent VSim Quality Management Program Acceptance testing - manufacturer procedure, if it exists Commissioning - resident physicist establishes procedures baseline values, mostly for electromechanical/imaging system components Periodic QA ensures consistency of baseline values End of warranty tests - 6 weeks prior to end of warranty 9 Post service/upgrade tests 10 Data Transfer from CT to VSim Node Setup VSim IP address Data transfer VSim AE Title CT scanner DICOM export configuration screen 11

Management Program Acceptance testing - manufacturer procedure, if it exists Commissioning - resident physicist establishes procedures baseline values, mostly for

4 Data Transfer Issues trouble in paradise Data Transfer from VSim to TPS DICOM RT Information standard to move images, etc VSim hosts file VSim hosts file does not include CT scanner IP Routers are mac layered Dicom service has stopped on VSim IT has secretly upgraded the router When in doubt reboot! Images: CTs, DRRs Structure sets: Points of interest, bolus, 3D objects Plan parameters: Tx fields, tolerance tables, Rx, patient orientation, fractionation, machine ID, accessories 14 Network Transfer Glossary SOP: service object pair (CT -> Vsim) SCP: Service Class Provider (eg VSim) SCU: Service Class User (eg CT) ftp: file transfer protocol UID: Unique identifier (transfer session ID) Data Transfer issues from VSim Eg: Beam to energy TPS does not transfer GE Advantage sim DICOM conformance statement XiO TPS DICOM conformance statement 15 16

$Images: CTs, DRRs Structure sets: Points of interest, bolus, 3D objects Plan parameters: Tx fields, tolerance tables, Rx, patient orientation, fractionation, machine ID, accessories 14 Network$

5 Patient orientation Machine definition Movable lasers Structure segmentation DRR accuracy 4DCT SRS 17 patient orientation Ensure images are transferred to VSim and TPS correctly and they display correct orientation Implications: Reversed beam orientation Contours drawn on wrong side of patient HFS FFS HFP 18 patient orientation CT screen Incorrect patient orientation TPS screen 19 machine definition Available beam energies Position and limits of jaws Collimator rotation MLC type (52,58, , 120 HD, m3, 160 leaf) Angle convention (IEC , IEC 1217 or non-iec) Tolerance levels should be tight Implications are numerous: missing or incorrect beam parameters transferred to TPS 20

Incorrect patient orientation TPS screen 19 machine definition Available beam energies Position and limits of jaws Collimator rotation MLC type (52,58, 82 120, 120 HD, m3,

6 machine definition machine definition machine definition - verification movable lasers Mechanical system Absolute, relative position accuracy Scan phantom with radio-opaque reference point and mm markings Test system through its maximum mechanical extents Implications: incorrect isocenter markings which may not be caught until film is reviewed 1) Set up beams in VSim 2) Transfer to TPS 3) Verify Parameters: Machine/energy scale gantry angle rotations field size etc TPS 23 24

mechanical extents Implications: incorrect isocenter markings which may not be caught until film is reviewed 1) Set up

7 movable lasers Scales Radiopaque markers structure delineation Bifurcating structures or disconnected structures Contouring in sagittal cuts Contour interpolating Double contours (external skin) Copy structures, expansion, Boolean operations Unclosed contours Accurate volume reporting structure delineation contour interpolation structure delineation double contours Ensure correct position TPS single contour TPS - Shifted external contour axial VSim - Before interpolation VSim -After interpolation Does the TPS allow double contours? TPS - Shifted external contour sagittal 27 28

26 structure delineation contour interpolation structure delineation double contours Ensure correct position TPS single contour TPS - Shifted

8 structure delineation volume reporting Contour object of known dimensions in VSim Verify volume, dimensions Ensure same volume, dimensions are reported in TPS Set CT image level to ½ of object s max, set window to <50 Implication: incorrect DVH reporting VSim Incorrect windowing TPS 29 DRR accuracy Physicians rely on accurate DRRs to: delineate blocking set field size dimensions view organ projections Implications: Under or over coverage of disease Inadequate sparing of healthy tissue 30 DRR accuracy VSim acceptance testing 4DCT Scan plate between plastic slabs Radiopaque markers AP DRR on VSim workstation Acquires >10 images per couch position Accurate tracking of motion surrogate Analyze motion in three planes 31

field size dimensions view organ projections Implications: Under or over coverage of disease Inadequate sparing of healthy tissue 30 DRR accuracy VSim acceptance testing 4DCT Scan

9 VSim Acceptance testing 4DCT Test to verify that total deflection of movement is being acquired by 4DCT system Should be done in 3 axes Implications: incorrect size of MIP (maximum intensity projection) mm measure d deflection VSim Acceptance testing SRS/SBRT Image quality High contrast resolution Low contrast detectability, noise Image fusion Accuracy of fusion module MRI distortion 34 Use of VSim in SRS Image fusion - distortion Use of VSim in SRS Image fusion - distortion TG 117 (in progress): The use of MRI Data in Treatment Planning and Stereotactic Procedures Spatial Accuracy and Quality Control Procedures TG132 (In progress): Use of Image Registration and Data Fusion Algorithms and Techniques in Radiotherapy Treatment Planning MRI test phantom Implications of image distortion: - Incorrect anatomical rendering Acceptable registration MRI CT Poor registration Deformable/translational or translational only QA of MRI to test image distortion Evaluate fusion with MRI/CT phantom Fused image sets 36

distortion 34 Use of VSim in SRS Image fusion - distortion Use of VSim in SRS Image fusion - distortion TG 117 (in progress): The use of MRI Data in Treatment Planning and Stereotactic Procedures

10 VSim Periodic QA Questions? Low likelihood of VSim parameters changing over time Yearly: repeat acceptance tests Focus on testing after upgrades and external system changes Next Talk: CT Sim: Electromechanical, image quality Guru Prasad 39

repeat acceptance tests Focus on testing after upgrades and

CT RADIATION DOSE REPORT FROM DICOM. Frank Dong, PhD, DABR Diagnostic Physicist Imaging Institute Cleveland Clinic Foundation Cleveland, OH

CT RADIATION DOSE REPORT FROM DICOM Frank Dong, PhD, DABR Diagnostic Physicist Imaging Institute Cleveland Clinic Foundation Cleveland, OH CT Patient comes out... Patient goes in... Big Black Box Radiology