Acknowledgements
QA for the TomoTherapy Hi
™
Hi--Art
Art™
Katja Langen, PhD
Sanford Meeks, PhD
Disclosures
MDACCO has received grant funding from
TomoTherapy, Inc.
Robert J. Staton, PhD
Medical Physicist
Topics
The TomoTherapy units at MD Anderson Orlando
• Review of the TomoTherapy system
Tomo1 (SN 02)
Tomo2 (SN 50)
• Commissioning and Twinning
• QA Program
• Routine
• After Component Replacement
• Patient DQA
• TQA
TomoTherapy
TomoTherapy
• Helical delivery of IMRT
6 MV Accelerator
Primary Collimator
• Same hardware is used for MVCT
Binary MLC
85cm
(64 leaves – 6.25mm )
• IGRT for every patient
85 cm Gantry Aperture
40 cm CT FOV
Approximately
50cm
TomoTherapy
TomoTherapy
Fan beam,
continuously
rotates
Patient
Divides beam into 64 beamlets
each beamlet can be on/off for a
percentage of each projection
Target
OAR
TomoTherapy
TomoTherapy
Fan beam,
Fan beam,
continuously
rotates
Patient
continuously
rotates
Target
OAR
TomoTherapy
TomoTherapy
Fan beam,
Fan beam,
continuously
rotates
continuously
rotates
Fan Beam
lateral
Helical Tomotherapy
longitudinal
400 mm
lateral
10, 25, or 50 mm
longitudinal
Delivery
- 51 projections per
rotation: 360º/51=7º
-Temporal modulation
leaf opening time
during projection
-Typical gantry rotation:
15-30 seconds
-Typical treatment time:
Prostate: 5 Min
H&N: 7 Min
from: W. Kalender, Computed Tomography: Fundamentals,
System Technology, Image Quality, Applications
Delivery Instructions (Sinograms)
Sinogram
Sinogram
1 gantry rotation
Sinogram
Megavoltage CT images
6 MV Accelerator (tuned to 3.5 MV for MVCT)
Primary Collimator
( 5 mm Slice Width)
Binary MLC
85cm
(all leafs open during MVCT)
85 cm Gantry Aperture
40 cm CT FOV
Approximately
50cm
Commissioning
IGRT using megavoltage CT images
Prostate
Head + Neck
• Done in conjunction with TomoTherapy physicist
• Machines are assembled and tested in the
factory and then partially disassembled for
shipment
• Verify that the beam properties matches the
machine data taken in the factory and the gold
standard
• TomoTherapy TPS uses gold standard data for
all dose calculations
Commissioning Tests
•
•
Hardware Alignment
•
Source position
•
Jaws
•
MLC
•
Lasers
Beam
•
Output Stability
•
Beam Profiles - Transverse, Beam Width, PDD
•
Static Output Calibration
•
MVCT image quality
•
IMRT phantom tests
Water Tank
Standard Imaging – 2D Scanning Tank
Scanning Data
Scanning Data
PDD 25 mm Field Width
Cone 25 mm Field Width
15mm Calculated
50mm Calculated
100
100mm Calculated
100
Calculated
150mm Calculated
Measured
90
90
200mm Calculated
Install measured
15mm Install Measured
80
80
70
70
50mm Install Measured
100mm Install Measured
Dose (Normalized)
Dose (Normalized)
150mm Install Measured
60
50
40
200mm Install Measured
60
50
40
30
30
20
20
10
10
0
0
0
5
10
15
20
25
-300
-200
-100
0
Distance (cm)
100
200
300
Distance (mm)
Scanning Data
Commissioning - IMRT Tests
Penumbra 25 mm Field Width
• On-axis and off-axis target for each beam
15mm Calculated
50mm Calculated
100
100mm Calculated
90
150mm Calculated
80
Calculated & Delivered Dose: 25mm Beam, On-Axis Tumor
200mm Calculated
Calculated & Delivered Dose: 25mm Beam, Off-Axis Tumor
Calculated
Calculated
15mm Install Measured
70
2.0
Measured
2.0
Measured
Dose (Normalized)
50mm Install Measured
60
1.5
1.5
Dose (Gy)
150mm Install Measured
Dose (Gy)
100mm Install Measured
50
1.0
1.0
200mm Install Measured
40
0.5
0.5
30
-20
10
0
-25
-20
-15
-10
-5
0.0
0.0
20
0
Distance (mm)
5
10
15
20
25
-15
-10
-5
0
Distance (cm)
5
10
15
20
-20
-15
-10
-5
0
Distance (cm)
5
10
15
20
Twinning
• For multiple machines, you can match
the beam characteristics
After Commissioning
•
• Recommissioning
• Facilitates the transfer of patients from
one machine to the other in case of down
time
•
End to End phantom tests
•
H&N phantom
•
Pelvis phantom
•
Cheese phantom
•
Film & Ion Chamber
DQAs for phantom plans and test cases
•
Independent calibration check - RPC TLDs
•
Setup your QA program
•
•
QA Program
Daily QA
Reference data for monthly and part replacement QA
•
TMR/PDD in solid water
•
TomoDose Profiles
Daily Output Constancy
Routine:
Daily QA Output measurements:
Daily, Patient DQA, Monthly, Annual
•
Static procedure, gantry at 0°, 5x40 cm field
•
Readings taken at a depth of 5 cm and 10 cm
After Component Replacement:
Magnetron, MLC, Target
Daily Output Summary
Daily Output Constancy
Hi*Art II, S/N 002
850
+5%
840
830
+3%
+2%
810
800
790
-2%
-3%
780
770
760
- Very temperature sensitive
-if machine is not at operating temp. (38-40 ºC)
output measurement can be unreliable
-5%
17-Feb-08
7-Sep-07
28-Nov-07
17-Jun-07
4-Jan-07
27-Mar-07
25-Jul-06
15-Oct-06
4-May-06
11-Feb-06
1-Sep-05
22-Nov-05
11-Jun-05
21-Mar-05
9-Oct-04
30-Dec-04
19-Jul-04
6-Feb-04
28-Apr-04
17-Nov-03
6-Jun-03
27-Aug-03
16-Mar-03
750
Date
Daily Energy Constancy
Daily IMRT Procedure
HI*ART II S/N 002, ENERGY CHECK
0.4350
0.4300
+3 %
+2 %
0.4250
0.4200
1) Scan
0.4150
0.4100
DATE
14-Nov-07
28-Apr-07
10-Oct-06
24-Mar-06
5-Sep-05
17-Feb-05
1-Aug-04
14-Jan-04
28-Jun-03
0.4000
1J
0.4050
08
-2 %
-3 %
10-Dec-02
DEPTH DOSE AT 15 cm
Output (cGy) (60sec Readings)
820
- Typically within 2 % of nominal output
- If outside 3 %, adjust PFN (output) at end of day
- Observed long term drifts
- About 2 weeks after magnetron replacement
- End of target life
2 ) Register
4) Treat
-compare to
known offsets
- two point dose
measurements
3) Align
-test couch and
laser movements
DQA Setup
Patient Plan DQA
- Deliver plan into phantom
- Measure dose point with Ion chamber and dose
distribution with EDR film
Ion chamber high
dose, low gradient
region
DQA Setup
DQA – Point Dose Measurement
TomoTherapy Point Dose Verification
Temperature
24.0
Pressure
759.0
CTP
1.008
Electrometer
Calculate dose distribution in the phantom
C
mm Hg
Inovision 35040
Chamber
Phantom
0
Exradin A1SL, SN
30562
Solid H20 ("Cheese" Phantom)
System Calibration Factor (C21)
0.6660
[Gy/nC]
Ion Chamber Position In Phantom
1 BELOW
Film Plane
Electrometer Reading for Phantom Irra
2.081
Doseplan
1.381
Dosemeas
1.397
[nC]
[Gy]
Ratio (Dm eas /Dplan)
1.012
Pass
1.1780
% Difference
[Gy]
DQA Film Analysis
DQA film analysis
Expected isodose lines vs measurement
Film
DQA Film Analysis
DQA – Point Dose Measurement
Film and dose profiles
5%
3%
06-07 DQA Results
10
8
6
% Difference
4
2
0
-2
-4
-6
-8
-10
11/14/2007
8/6/2007
4/28/2007
1/18/2007
10/10/2006
7/2/2006
3/24/2006
12/14/2005
Date
DQA with Array devices
Available array devices
DQA with Array devices
Advantages:
Sun Nuclear – MapCHECK
Time savings
IBA Dosimetry – Matrixx
No film processing issues
PTW – 2D-ARRAY seven29
Real time comparison
Disadvantages:
Resolution
Tomo DQA with MapCHECK
Tomo DQA with MapCHECK
Head and Neck
- Initial tests have shown good results for
TomoTherapy DQA
-Gamma test results
- Absolute dose (3%, 3mm)
- HN: 98.5% passing
- Prostate: 99.6% passing
Tomo DQA with MapCHECK
Tomo DQA with MapCHECK
Prostate
Import into TomoTherapy
Monthly QA
Monthly QA
-Output measurement with farmer chamber
-Output measurement with farmer chamber
-Laser alignments, x-z localization procedure
-Laser alignments, x-z localization procedure
- Cone profile, lateral profile
(TomoDose - diode array)
- Cone profile, lateral profile
(TomoDose - diode array)
- Beam profile, longitudinal profile
- Beam profile, longitudinal profile
- MVCT dose and HU
- MVCT dose and HU
-Table position accuracy (ruler vs. readout)
-Table position accuracy (ruler vs. readout)
Fan Beam
TomoDOSE
lateral
Check profile monthly
longitudinal
400 mm
lateral
10, 25, or 50 mm
longitudinal
TomoDOSE lateral beam profile
Accuracy of TomoDOSE
1.2
1
Relative Reading
0.8
0.6
0.4
0.2
0
-30
-20
-10
0
Off axis distance (mm)
10
20
30
Accuracy of TomoDOSE
Monthly QA: Cone Profile
Monthly QA: Cone Profile
Monthly QA
-Output measurement with farmer chamber
-Laser alignments, x-z localization procedure
- Cone profile, lateral profile
(TomoDose - diode array)
- Beam profile, longitudinal profile
- MVCT dose and HU
-Table position accuracy (ruler vs. readout)
Longitudinal Profile
Monthly QA
-Output measurement with farmer chamber
- Static Gantry at 0°
- Continuous table
movement
- Measure current
-Laser alignments, x-z localization procedure
- Cone profile, lateral profile
(TomoDose - diode array)
- Beam profile, longitudinal profile
FWHM
- MVCT dose and HU
-Table position accuracy (ruler vs. readout)
Monthly MVCT QA
Test Consistency
1.824
0.48
1.56
0.33
HU
Noise
Uniformity
Spatial resolution
Dose
- takes 1 MVCT scan
Weekly QA (by TomoTherapy Service)
- Output
- Cone beam profile
- Check error Log files
- Check TCS
- Check Data Server
- Check various mechanical parameters
Weekly QA (by TomoTherapy Service)
Rotational Variation (by TomoTherapy Service)
6 MV Accelerator
- Output
- Cone beam profile
Rotational Variation
- Check error Log files
- Check TCS
- Check Data Server
- Check various mechanical parameters
Primary Collimator
85cm
Binary MLC
40
FOV
CT
cm
- Treatment beam
- All MLC leafs open
- Rotate gantry
- Collect detector data
- Compare detector data
to Gold Standard
Approximately 50cm
Rotational Variation
Annual QA
-Beam data (PDD, long. and lateral profiles)
-Mechanical alignment tests (Jaw, MLC alignment)
Follow TomoTherapy’s recommended
test procedures
Phantom end-to-end test
Annual QA, Beam Data
-Collect beam data for all (three) commissioned
beam widths (1.0, 2.5, 5.0 cm)
-Cheese Phantom based end-to-end tests
- RPC TLD
RPC TLD Measurements (Static Field)
20 s beam-on time
with 5x40 field gives
~270 cGy to TLDs
1 cm
2.5 cm
5 cm
Central
Target
+ 0.5 %
+ 2.8 %
+ 2.1 %
Peripheral
Target
+ 1.3 %
+ 1.0 %
+ 0.8 %
Annual QA Alignment Tests
-Source should be aligned with center of jaw
Measure output at different jaw positions
Max output indicates jaw center
Annual QA Alignment Tests
Annual QA: Y-Divergence/Jaw Twist
-Test Y-divergence and jaw twist
Film below iso, irradiate from 0º and 180º
Aligned Jaw
Iso
Film
Twisted Jaw
Divergence center
off from rotation plane
Annual QA Alignment Tests
Time Requirement
-Source should be aligned with MLC
- Daily: Including warm up time: 1 hour
Run odd leaf only and even leaf only profile
Compare to all leaf open profile -> T-G profile
Look for symmetry in TG-Profile
- DQA: 20-30 minutes per case
- Monthly: 2-3 hours
- Annual: 1-2 days
QA Following Major Component Replacement
QA Following Major Component Replacement
Magnetron
Typically every 3-4 months
MLC
Typically lasts about 18 Months
Tomo service engineer
-Adjusts beam profile and output using a
rotational variation procedure
Tomo service engineer
-Checks alignment with T+G test
-Measures leaf latency
update leaf latency file for future plans
Physicist: (2 h)
-Check output and energy
-Check beam profile using TomoDose array
-Run 1-2 DQA procedures (IC+Film)
QA Following Major Component Replacement
Target
Typically lasts 8-10 Months
Tomo service engineer
-Checks Linac alignment
-Adjusts beam profile and output using a
rotational variation procedure
Physicist: (1-2 days)
- Beam profiles (TomoDose)
Do annual QA
Physicist: (3-4 h)
-Check multiple current patient DQAs. 6-8 DQA
Target Wear Warning Signs
Beam profile change:
• Service engineers checks beam profiles weekly
• Physics QA includes monthly TomoDOSE test
Target Wear Warning Signs
Variations in lateral beam profile
TomoDOSE
Energy Variation
Component replacement
Target :
HI*ART II S/N 002, ENERGY CHECK
Target changes
0.4350
• Can typically be predicted
+3 %
+2 %
0.4250
0.4200
• Scheduled over weekend
Magnetron :
0.4150
• Fails suddenly
0.4100
14-Nov-07
28-Apr-07
10-Oct-06
24-Mar-06
5-Sep-05
17-Feb-05
1-Aug-04
14-Jan-04
28-Jun-03
0.4000
1J
0.4050
08
-2 %
-3 %
10-Dec-02
DEPTH DOSE AT 15 cm
0.4300
DATE
On-board detector
• 1 day (or one night job)
TomoTherapy TQA
•
TQA software being released by TomoTherapy
•
Uses detector data to measure beam properties and
delivery systems
•
Conclusion
Routine Machine QA:
• Comparable to other machines in terms of time
•
Output
•
Beam Profile
•
Energy
Major component replacement:
•
Lasers
• More frequent than ‘regular’ Linac
•
Couch synchrony
•
MLC
Allows access to detector data for QA for development
of personalized QA tests
Thank You
• Some replacement can be predicted
• TQA may help with prediction of these failures