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Section 1:Section 1:IntroductionIntroduction
Siemens Medical Solutions, Inc.Oncology Care Systems Group4040 Nelson AvenueConcord, CA 95420
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MVision Physicist Self-Led TrainingMVision Physicist Self-Led TrainingRev. C
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Section Guide
Section 1: Introduction and Preview
Section 2: Cone Beam Geometry Calibration
Section 3: Image Quality QA
Section 4: Adaptive Targeting
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Section 1: ObjectivesSection 1: Objectives
At the completion of this section, you will be able to:
Identify the fundamentals of MVision
List the physicist calibration and QA tasks related to MVision
Perform flat panel 2D gain calibration
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Section 1: Table of ContentsSection 1: Table of Contents
Overview
Performance Parameters
Target Monitor Units
Beam Tuning Comparison
Acquisition Time
MVision Advantages
Looking Ahead
Physicist QA Tasks
New Tools for MVision
MVision QA and Maintenance
Section 1 Review
Section 1 Quiz
Lab: 2D Gain Calibration
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MVision OverviewMVision OverviewMVision imaging is the process of: Acquiring 2D images Reconstructing a 3D image data set
from the 2D images Advantages: Patient Imaging and treatment on the
same machine Quick comparison between the CT plan
images to the MVision images prior treatment
Adapt the patient CT plan as necessary
At each arc increment, a
small amount of dose is
delivered to acquire one
frame of MVision
images
The Gantry moves at a
constant speed as it
does in an arc
treatment
MVision arc
starts here
(270°)
MVision arc
ends here
(110°) completing
the acquisition
Figure 1.0
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MVision OverviewMVision Overview Product goals Workflow integration Syngo imaging platform Improve patient positioning accuracy by
using 3D space Use of the existing equipment (LINAC
Flat Panel, syngo workstation) Secondary imaging system not required
At each arc increment, a
small amount of dose is
delivered to acquire one
frame of MVision
images
The Gantry moves at a
constant speed as it
does in an arc
treatment
MVision arc
starts here
(270°)
MVision arc
ends here
(110°) completing
the acquisition
Figure 1.0
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MVision Performance ParametersMVision Performance ParametersParameter Value
CT number range -1000 to +3095
CT number accuracy ±40 HU: The shift of the mean (from expected value of
0 HU) in the center 2 cm ROI within a 20 cm solid water
equivalent
CT number uniformity 60 HU (cupping effect): Difference between maximum
intensity of regions in the periphery and the central
region
Spatial resolution 0.3 lp.mm: Measured with 1.0 mm voxel reconstruction
Table 1.0
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Parameter Value
Low contrast resolution 5%: 2 cm diameter region is visible with 5 mm slice
thickness with 10 cGy dose
Noise 4%: with 10 cGy dose: Measured in the 2 cm ROI within
a 17.5 cm diameter solid water phantom
Reconstruction field-of-view 27 cm diameter in transaxial slices; 27 cm in the axial
direction
Reconstruction matrix size 128 x 128, 256 x 256, 512 x 512
MVision Performance ParametersMVision Performance Parameters
Table 1.0
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Parameter Value
Slice thickness From as small as 1.4 mm minimum up to arbitrary
thickness by means of thick MPR
Acquisition reconstruction and
auto-registration time
Typically 2.5 min for acquisition and reconstruction;
typically 3 min for acquisition, reconstruction and auto-
registration for 256 x 256 x 270
Geometry accuracy <1 mm: This is defined by how well distance can be
measured within the scanned volume
MVision Performance ParametersMVision Performance Parameters
Table 1.0
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MVision Target Monitor UnitsMVision Target Monitor Units
MVision preset MU
Target MU = (MVision preset
MU x 0.9)
Target MU = (MVision preset MU
x 0.9) - 5%
Target MU = (MVision preset MU x 0.9) + 5%
3 2.7 2.56 2.83
5 4.5 4.275 4.725
8 7.2 6.84 7.56
10 9 8.55 9.45
15 13.5 12.82 14.17
18 16.2 15.39 17.01
20 18 17.1 18.9
40 36 34.2 37.8
60 54 51.3 56.7
Table 1.1
MVision target monitor units
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Beam Tuning ComparisonBeam Tuning Comparison
Regular 6MV 50MU/Min
MVision 6MV 50MU/Min
Lower Dose per pulse
Higher radiation pulse repetition frequency~ 4 ms
Higher Dose per pulse
Lower radiation pulse
repetition frequency~ 24 ms
Same radiation pulse
time duration~ 3.4s
Figure 1.1
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Acquisition TimeAcquisition Time
For each projection image
Figure 1.2
//
//
Rad On time
Beam Integration for dosimetry& transmit to Control Console
FP Readout
Safety margin for non-smooth gantry motion
Total time for acquisition of one projection image
Gantry Position 1 Gantry Position2
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MVision AdvantageMVision Advantage
Minimizes artifacts caused by dental implants
Kilovoltage CTKilovoltage CT MVisionMVision
With courtesy from:J. Pouliot, UCSFWith courtesy from:J. Pouliot, UCSFFigure 1.3 - a Figure 1.3 - b
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MVision AdvantageMVision Advantage
Minimizes artifacts caused by metal prostheses
With courtesy from: J. Pouliot, UCSFWith courtesy from: J. Pouliot, UCSFFigure 1.4
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Looking AheadLooking Ahead
Exit Dosimetry
Import MVision images in the TPS to calculate actual dose distribution
With courtesy from: J. Pouliot, UCSF, April 29, 2005 Stanford IGRT Short CourseWith courtesy from: J. Pouliot, UCSF, April 29, 2005 Stanford IGRT Short CourseFigure 1.5
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MVision Physicist QA TasksMVision Physicist QA Tasks
Figure 1.6 Perform MVision
Geometry Calibration
Create or update
MVision Protocol
Perform MVision Gain
Calibration
Perform Flat Panel
Alignment QA
Perform 2D
Gain Calibration
Perform MVision
Image QA
Physicist tasks include:
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MVision Physicist QA TasksMVision Physicist QA Tasks
Perform MVision
Geometry Calibration
Perform MVision Gain
Calibration
Perform Flat Panel
Alignment QA
Perform 2D
Gain Calibration
Physicist tasks include:
Create or update
MVision Protocol
Perform MVision
Image QA
Figure 1.6
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Tools for MVisionTools for MVision
Figure 1.7b
Figure 1.7a
OPTIVUE 1000 ST Flat Panel
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Tools for MVisionTools for MVisionOPTIVUE 1000 ST Flat Panel
Figure 1.8
Scintillator
Incident X-rays
Capacitive
Storage
Element
Visible Light
+ + + + + + + Electrical Charge
Photodiode
Digital Image
Charge Readout and Analog
to Digital Signal
Conversion
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Tools for MVision Tools for MVision
Table 1.2
FEATURE OPTIVUE 1000ST Specifications
Detector weight (Kg) 23
Detector size (mm) 672 x 599 x 44
Active detection area (cm2) 41 x 41
Maximum acquisition rate (fps) 7 frames per second
Image display time Near real time
Detector efficiency (port only) Max recommended dose: 3 MU
Detector non-linearity<±2% for free-run acquisition
<±3% for triggered acquisition
1. These are minimum specifications; below these values, the detectors are rejected.
2. As measured using the PIPSpro QC-3V phantom.
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Tools for MVision Tools for MVision
Table 1.2
FEATURE OPTIVUE 1000ST Specifications
Detection method Indirect
Matrix size (pixels) 1024 x 1024
Pixel size (µm) 400
Pixel bit depth 16 bits
Spatial resolution (f50 in lp/mm)1 ≥0.41 lp/mmm at 6MV
Contrast/noise ratio 1, 2 (port during) ≥600 @ 50 MU (1024 x 1024)
Contrast/noise ratio 1, 2 (port only) 125 @ 1 MU (1024 x 1024)
1. These are minimum specifications; below these values, the detectors are rejected.
2. As measured using the PIPSpro QC-3V phantom.
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Tools for MVisionTools for MVisionService Patient
Used to perform MVision and 2D imaging calibration tasks
Site Name Purpose Physicist Task Siemens Service Task
Calibration Gain-SID1 2D Gain Calibration
Calibration-Other 1.52 Dead Pixel Map Calibration
Calibration-Other 2.03Dead Pixel Map Calibration, MVision Gain
Calibration and Geometry Calibration
FlatPanelAligment Flat panel alignment calibration for 2D imaging
FlatPanelAligment CB Flat panel alignment calibration for MVision imaging
1 Each gain site assumes a different SID value : 120, 130, 140, 145, 150, 155 and 160 cm
2 Not used for MVision users
3 Physicist should only perform MVision Gain Calibration and Geometry Calibration
Table 1.3
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Tools for MVisionTools for MVisionService Patient
Figure 1.9
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Tools for MVisionTools for MVisionImage Quality Patient
Used to perform MVision and 2D Imaging QA tasks
Site Name Purpose Physicist Task Siemens Service Task
Image QA Create MVision Fields for Image QA and acquire
the Flat Panel alignment QA images1
OPTIVUE ATP: AG9 Perform 2D Image Quality ATP for AG9 (1000ST)
Flat Panel
OPTIVUE ATP: AL7 Perform 2D Image Quality ATP for AL7 Flat Panel
UniformitySet1B, 2B
and 3B : AG9Perform AG9 Flat panel image uniformity check
UniformitySet1B, 2B
and 3B : AL7
Perform AL7 Flat panel image uniformity check
1 Siemens service will acquire a reference image for the flatpanel alignment QA during MVision tune-upTable 1.4
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Tools for MVisionTools for MVisionImage Quality Patient
Figure 1.10
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XRETIC Crosshair Reticule
Fits in Slot 3 of the machine accessory holder
Is used to:
Perform flat panel alignment QA
Set image quality phantom alignment
Perform flat panel alignment calibration (Siemens service only)
Tools for MVisionTools for MVision
Figure 1.11
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Tools for MVisionTools for MVision
Figure 1.12
XRETIC Calibration
The physicist may check the
XRETIC calibration using the
Lab7 XRETIC Calibration Check
Product label
Tungsten wire (2 extra wires are delivered with product)
Digital resistor plug (Siemens code XRETIC)
Wire tension and position adjustment
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Flat panel alignment QA
The XRETIC reticule and the Image Quality patient are used to perform this check
Deliver the Daily QA port only field using the site Image QA and check
Visually inspect the alignment of the image with the Coherence green crosshair
Measure the offset between green crosshair and acquired image
Recommended Frequency: Daily
Tolerance: ±1mm
MVision QA and MaintenanceMVision QA and Maintenance
Figure 1.13
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Flat panel alignment QA
If the measured offset is larger than ±1mm the physicist may check
XRETIC calibration
Light versus Radiation Field coincidence
If corrections are needed on either of the above please contact Siemens Service
MVision QA and MaintenanceMVision QA and Maintenance
Figure 1.13
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2D Gain Calibration
Used to correct differences in the Flat Panel diodes behavior on 2D imaging
Service Patient is used to acquire Port During Gain fields at different Photon Energies, Dose Rates, Source to Imager Distances (SID), Monitor Units and Field Sizes
The 2D gain fields are grouped on different sites identified by different SID
Each site contains four gain fields (except for SID 120 which has two gain fields)
MVision QA and MaintenanceMVision QA and Maintenance
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2D Gain Calibration
Physicists or Therapists may acquire the 2D Gain Fields Suggested 2D Gain Calibration frequency: every 2 Weeks Coherence Therapist prompts the user to re-acquire the 2D gains
every four weeks The gain files are overwritten every time a new gain calibration is
performed See Lab 1: 2D Gain Calibration for instructions on how to perform gain
calibration
MVision QA and MaintenanceMVision QA and Maintenance
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MVision QA and MaintenanceMVision QA and MaintenanceFlat Panel 2D Gain Calibration
Figure 1.14
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2D Gain History
To verify if the gains are up to date check the 2D gain history file “Gain_History.txt”
MVision QA and MaintenanceMVision QA and Maintenance
Figure 1.15
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2D Gain Images Location
The 2D Gain images are stored at :
C:\Coherence\data\PortalImaging\Gain
MVision QA and MaintenanceMVision QA and Maintenance
Figure 1.16
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MVision Beam Output Calibration
Physicist should calibrate the MVision beam output prior service engineer performing the dose scale factor (DSF) calibration
MVision beam tuning should be performed in the following order
Siemens installer performs MVision beam peaking to comply with MVision imaging requirements
Site Physicist performs MVision beam output calibration
Siemens Installer performs the Dose Scale Factor Calibration
MVision QA and MaintenanceMVision QA and Maintenance
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MVision QA and MaintenanceMVision QA and MaintenanceControl Console pages used for MVision
Cone Beam Calibration Cone Beam Calibration is
used to visualize the dose
scale factor calibration
points
Softpots Softpots is used to
calibrate MVision beam
output
Figure 1.17
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MVision QA and MaintenanceMVision QA and MaintenanceMVision dose page
DOSE SET 17 DOSE SET 17
is the dose
page used to
calibrate
MVision Beam
Output
CB-AJ is
displayed
when the
Cone Beam
dose page
is selected
D1_C0D1_C0 is not used
for MVision acquisitions
Figure 1.18
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Cone Beam Calibration page
MVision QA and MaintenanceMVision QA and Maintenance
Dose Scale Factor Dose Scale Factor calibration
points. The smaller and the
larger monitor units values
represent the range of MU
allowed to scan patients with
MVision
Dose Margin Factor Dose Margin Factor is used as
an additional safety if the
MVision dose deviates by more
than 20%
Gantry Speed Factor Gantry Speed Factor is used to
fine tune the gantry speed for
optimal MVision acquisitionFigure 1.19
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Section 1: ObjectivesSection 1: Objectives
Now that you have completed this section, you should be able to :
Identify the fundamentals of Mega Voltage MVision
List the physicist calibration and QA tasks related to MVision
Perform Flat Panel 2D Gain
Page 40 July 2007 Copyright © Siemens AG 2007. All rights reserved.
Section 1: ReviewSection 1: Review
Performance Parameters
Target Monitor Units
Beam Tuning Comparison
Acquisition Time
MVision Advantages
Physicist QA Tasks
New Tools for MVision
MVision QA and Maintenance
During this self-led training, you have read through the following topics:
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Section 1 Quiz
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The primary goal of MVision is:
Correct - Click anywhere to continueCorrect - Click anywhere to continueIncorrect - Click anywhere to continueIncorrect - Click anywhere to continueYou must answer the question before continuingYou must answer the question before continuing
Submit ClearSubmit
A) Reconstruct a 3D image data set from 2D images
B) Position the patient more accurately
C) Spare critical organs
D) Increase the tumor dose
E) All of the above
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The OPTIVUE 1000ST Flat Panel is called an indirect detector because it converts:
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A) X-ray into charge
B) Charge into current
C) X-ray into visible light
D) All of the above
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Only the physicist should create or update an MVision protocol.
Submit Clear
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A) True
B) False
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What is the recommended frequency to perform 2D gain calibration?
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A) Every week as required
B) Every two weeks
C) Annually
D) If the Flat Panel Daily QA fails
E) B and D are correct
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If the Daily Flat Panel QA is out of the +/- 1mm specification, the physicist should:
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A) Perform the Flat Panel alignment
B) Check the XRETIC calibration
C) Calibrate the XRETIC
D) Check the light to radiation field coincidence
E) B and D are correct
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A 10MU MVision protocol is used to image a patient. The delivered (target) MU should be:
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A) 10MU
B) 9MU
C) Between 8.55MU and 9.45MU
D) 11MU
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The MVision Beam Output Calibration should be checked by the physicist after the Service Engineer performs the Dose Scale Factor calibration.
Submit Clear
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A) True
B) False
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The MVision Physicist tasks include:
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A) 2D and MVision gain calibration
B) Create/Modify MVision protocols
C) Perform dead pixel map calibration
D) All of the above
E) A and B
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Whenever performing the flat panel alignment QA, the user should:
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A) Check if the alignment image is within +/- 1mm of the Coherence green crosshair
B) Calibrate the XRETIC to acquire the alignment images
C) Use the Service Patient to acquire the alignment image
D) All of the above
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To check the 2D gain history, one should:
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A) Acquire new gain files and open the Gain_History.txt file
B) Delete the Gain_History.txt file and acquire new Gains
C) Open the Gain_History.txt file
D) Calibrate the beam output prior and check the Gain files
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The Physicist should use the Image Quality patient to:
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A) Perform flat panel uniformity check
B) Calibrate the MVision Image Geometry
C) Perform the flat panel alignment QA
D) Perform MVision Image QA
E) C and D are correct
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The Physicist should use the Cone Beam Calibration to check if the dose scale factor points are within the MU range intended to scan patients and perform calibration tasks.
Submit Clear
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A) True
B) False
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The D1_C0 Softpot should be calibrated in order to:
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A) Get optimal dose delivery for MVision
B) Compensate for the beam formation time
C) Adjust the dose per projection image
D) Correct MVision beam output
E) It should not be calibrated
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