qa for the tomotherapy hi -art ™ · 2008-12-03 · tomotherapy patient target fan beam,...
TRANSCRIPT
Robert J. Staton, PhDMedical Physicist
QA for the TomoTherapy HiQA for the TomoTherapy HiQA for the TomoTherapy Hi---ArtArtArt™™™
Acknowledgements
Katja Langen, PhDSanford Meeks, PhD
MDACCO has received grant funding fromTomoTherapy, Inc.
Disclosures
The TomoTherapy units at MD Anderson Orlando
Tomo1 (SN 02) Tomo2 (SN 50)
Topics
• Review of the TomoTherapy system
• Commissioning and Twinning
• QA Program
• Routine
• After Component Replacement
• Patient DQA
• TQA
TomoTherapy
• Helical delivery of IMRT
• Same hardware is used for MVCT
• IGRT for every patient
Binary MLC(64 leaves – 6.25mm )
85 cm Gantry Aperture
40 cm CT FOV
85cm
Approximately 50cm
6 MV Accelerator
Primary Collimator
TomoTherapy
TomoTherapy
Patient
Target
Fan beam,
continuouslyrotates
OAR
TomoTherapy
each beamlet can be on/off for apercentage of each projection
Divides beam into 64 beamlets
TomoTherapy
Patient
Target
Fan beam,
continuouslyrotates
OAR
TomoTherapy
Fan beam,
continuouslyrotates
TomoTherapy
Fan beam,
continuouslyrotates
TomoTherapy
Fan beam,
continuouslyrotates
Fan Beam
400 mmlateral
10, 25, or 50 mm
longitudinal
lateral
longitudinal
Helical Tomotherapy
from: W. Kalender, Computed Tomography: Fundamentals,System Technology, Image Quality, Applications
Delivery
- 51 projections perrotation: 360º/51=7º
-Temporal modulationleaf opening timeduring projection
-Typical gantry rotation:15-30 seconds
-Typical treatment time:Prostate: 5 MinH&N: 7 Min
Delivery Instructions (Sinograms)
1 gantry rotation
Sinogram Sinogram
Sinogram
Binary MLC(all leafs open during MVCT)
85 cm Gantry Aperture
40 cm CT FOV
85cm
Approximately 50cm
6 MV Accelerator (tuned to 3.5 MV for MVCT)
Primary Collimator( 5 mm Slice Width)
Megavoltage CT images
IGRT using megavoltage CT images
Prostate Head + Neck
Commissioning• Done in conjunction with TomoTherapy physicist
• Machines are assembled and tested in thefactory and then partially disassembled forshipment
• Verify that the beam properties matches themachine data taken in the factory and the goldstandard
• TomoTherapy TPS uses gold standard data forall 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
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25
Do
se(N
orm
aliz
ed)
Distance (cm)
PDD 25 mm Field Width
Calculated
Measured
Install measured
Scanning Data
0
10
20
30
40
50
60
70
80
90
100
-300 -200 -100 0 100 200 300
Dos
e(N
orm
aliz
ed)
Distance (mm)
Cone 25 mm Field Width15mm Calculated
50mm Calculated
100mm Calculated
150mm Calculated
200mm Calculated
15mm Install Measured
50mm Install Measured
100mm Install Measured
150mm Install Measured
200mm Install Measured
Scanning Data
0
10
20
30
40
50
60
70
80
90
100
-25 -20 -15 -10 -5 0 5 10 15 20 25
Do
se(N
orm
aliz
ed)
Distance (mm)
Penumbra 25 mm Field Width 15mm Calculated
50mm Calculated
100mm Calculated
150mm Calculated
200mm Calculated
15mm Install Measured
50mm Install Measured
100mm Install Measured
150mm Install Measured
200mm Install Measured
Commissioning - IMRT Tests
• On-axis and off-axis target for each beam
0.0
0.5
1.0
1.5
2.0
-20 -15 -10 -5 0 5 10 15 20
Do
se(G
y)
Distance (cm)
Calculated & Delivered Dose: 25mm Beam, On-Axis Tumor
Calculated
Measured
0.0
0.5
1.0
1.5
2.0
-20 -15 -10 -5 0 5 10 15 20
Do
se(G
y)
Distance (cm)
Calculated & Delivered Dose: 25mm Beam, Off-Axis Tumor
Calculated
Measured
Twinning
• For multiple machines, you can matchthe beam characteristics
• Recommissioning
• Facilitates the transfer of patients fromone machine to the other in case of downtime
After Commissioning
• 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
• Daily QA
• Reference data for monthly and part replacement QA
• TMR/PDD in solid water
• TomoDose Profiles
QA Program
Routine:
Daily, Patient DQA, Monthly, Annual
After Component Replacement:
Magnetron, MLC, Target
Daily QA Output measurements:
• Static procedure, gantry at 0°, 5x40 cm field
• Readings taken at a depth of 5 cm and 10 cm
Daily Output Constancy
Daily Output Constancy
Hi*Art II, S/N 002
750
760
770
780
790
800
810
820
830
840
850
16-
Ma
r-03
6-Ju
n-03
27-
Au
g-03
17-
No
v-0
3
6-F
eb-
04
28-
Ap
r-04
19-J
ul-0
4
9-O
ct-0
4
30-
De
c-0
4
21-
Ma
r-05
11-
Jun-
05
1-S
ep-
05
22-
No
v-0
5
11-
Fe
b-06
4-M
ay-0
6
25-J
ul-0
6
15-O
ct-0
6
4-Ja
n-07
27-
Ma
r-07
17-
Jun-
07
7-S
ep-
07
28-
No
v-0
7
17-
Fe
b-08
Date
Out
put(
cGy)
(60
sec
Re
adin
gs)
+5%
-5%
+3%+2%
-3%-2%
Daily Output Summary
- 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
- Very temperature sensitive-if machine is not at operating temp. (38-40 ºC)output measurement can be unreliable
Daily Energy Constancy
+3 %+2 %
-3 %-2 %
HI*ART II S/N 002, ENERGY CHECK
0.4000
0.4050
0.4100
0.4150
0.4200
0.4250
0.4300
0.4350
10-D
ec-0
2
28-J
un-0
3
14-J
an-0
4
1-Au
g-04
17-F
eb-0
5
5-Se
p-05
24-M
ar-0
6
10-O
ct-0
6
28-A
pr-0
7
14-N
ov-0
7
1J
08
DATE
DEPT
HDO
SEAT
15cm
Daily IMRT Procedure
1) Scan 2 ) Register-compare toknown offsets
3) Align-test couch andlaser movements
4) Treat- two point dosemeasurements
Patient Plan DQA
- Deliver plan into phantom- Measure dose point with Ion chamber and dose
distribution with EDR film
DQA Setup
Ion chamber highdose, low gradientregion
DQA Setup
Calculate dose distribution in the phantom
DQA – Point Dose Measurement
TomoTherapy Point Dose Verification
Temperature 24.0 0C
Pressure 759.0 mm Hg
CTP 1.008
Electrometer Inovision 35040
Chamber Exradin A1SL, SN 30562
Phantom 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 [nC]
Doseplan 1.381 [Gy]
Dosemeas 1.397 [Gy]
Ratio (Dmeas/Dplan) 1.012 Pass
1.1780 % Difference
DQA Film Analysis
Film
DQA film analysis
Expected isodose lines vs measurement
DQA Film Analysis
Film and dose profiles
DQA – Point Dose Measurement
5%3%
06-07 DQA Results
-10
-8
-6
-4
-2
0
2
4
6
8
10
12/14/2005
3/24/2006
7/2/2006
10/10/2006
1/18/2007
4/28/2007
8/6/2007
11/14/2007
Date
%D
iffer
ence
DQA with Array devices
Available array devices
Sun Nuclear – MapCHECK
IBA Dosimetry – Matrixx
PTW – 2D-ARRAY seven29
DQA with Array devices
Advantages:
Time savings
No film processing issues
Real time comparison
Disadvantages:
Resolution
Tomo DQA with MapCHECK
- Initial tests have shown good results forTomoTherapy DQA
-Gamma test results- Absolute dose (3%, 3mm)- HN: 98.5% passing- Prostate: 99.6% passing
Tomo DQA with MapCHECK
Head and Neck
Tomo DQA with MapCHECK
Prostate
Tomo DQA with MapCHECK
Import into TomoTherapy
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)
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)
Fan Beam
400 mmlateral
10, 25, or 50 mm
longitudinal
lateral
longitudinal
Check profile monthly
TomoDOSE
TomoDOSE lateral beam profile
0
0.2
0.4
0.6
0.8
1
1.2
-30 -20 -10 0 10 20 30
Off axis distance (mm)
Rel
ativ
eRea
din
g
Accuracy of TomoDOSE
Accuracy of TomoDOSE Monthly QA: Cone Profile
Monthly QA: Cone ProfileMonthly 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
- Static Gantry at 0°- Continuous tablemovement
- Measure current
FWHM
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)
Monthly MVCT QA
Test Consistency
HUNoiseUniformitySpatial resolutionDose
- takes 1 MVCT scan
1.56
1.824
0.48
0.33
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)
- Output- Cone beam profile
- Check error Log files- Check TCS- Check Data Server- Check various mechanical parameters
Rotational Variation
Rotational Variation (by TomoTherapy Service)
Binary MLC
40 cm CT FOV
85cm
Approximately 50cm
6 MV Accelerator
Primary Collimator
- Treatment beam- All MLC leafs open- Rotate gantry- Collect detector data
- Compare detector datato Gold Standard
Rotational Variation Annual QA
-Beam data (PDD, long. and lateral profiles)
-Mechanical alignment tests (Jaw, MLC alignment)
�Follow TomoTherapy’s recommendedtest procedures
Annual QA, Beam Data
-Collect beam data for all (three) commissionedbeam widths (1.0, 2.5, 5.0 cm)
-Cheese Phantom based end-to-end tests
- RPC TLD
Phantom end-to-end test
1 cm 2.5 cm 5 cm
CentralTarget
+ 0.5 % + 2.8 % + 2.1 %
PeripheralTarget
+ 1.3 % + 1.0 % + 0.8 %
RPC TLD Measurements (Static Field)
20 s beam-on timewith 5x40 field gives~270 cGy to TLDs
Annual QA Alignment Tests
-Source should be aligned with center of jaw
Measure output at different jaw positionsMax output indicates jaw center
Annual QA Alignment Tests
-Test Y-divergence and jaw twistFilm below iso, irradiate from 0º and 180º
Iso
Film
Aligned Jaw
Twisted Jaw
Divergence centeroff from rotation plane
Annual QA: Y-Divergence/Jaw Twist
Annual QA Alignment Tests
-Source should be aligned with MLC
Run odd leaf only and even leaf only profileCompare to all leaf open profile -> T-G profileLook for symmetry in TG-Profile
Time Requirement
- Daily: Including warm up time: 1 hour
- DQA: 20-30 minutes per case
- Monthly: 2-3 hours
- Annual: 1-2 days
QA Following Major Component Replacement
MagnetronTypically every 3-4 months
Tomo service engineer-Adjusts beam profile and output using arotational variation procedure
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
MLCTypically lasts about 18 Months
Tomo service engineer-Checks alignment with T+G test-Measures leaf latency
� update leaf latency file for future plans
Physicist: (3-4 h)-Check multiple current patient DQAs. 6-8 DQA
QA Following Major Component Replacement
TargetTypically lasts 8-10 Months
Tomo service engineer-Checks Linac alignment-Adjusts beam profile and output using arotational variation procedure
Physicist: (1-2 days)- Beam profiles (TomoDose)� Do annual QA
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 On-board detector
Energy Variation
+3 %+2 %
-3 %-2 %
HI*ART II S/N 002, ENERGY CHECK
0.4000
0.4050
0.4100
0.4150
0.4200
0.4250
0.4300
0.4350
10-D
ec-0
2
28-J
un-0
3
14-J
an-0
4
1-Au
g-04
17-F
eb-0
5
5-Se
p-05
24-M
ar-0
6
10-O
ct-0
6
28-A
pr-0
7
14-N
ov-0
7
1J
08
DATE
DEPT
HDO
SEAT
15cm
Target changes
Component replacement
Target :
• Can typically be predicted
• Scheduled over weekend
Magnetron :
• Fails suddenly
• 1 day (or one night job)
TomoTherapy TQA
• TQA software being released by TomoTherapy
• Uses detector data to measure beam properties anddelivery systems
• Output
• Beam Profile
• Energy
• Lasers
• Couch synchrony
• MLC
• Allows access to detector data for QA for developmentof personalized QA tests
Conclusion
Routine Machine QA:
• Comparable to other machines in terms of time
Major component replacement:
• More frequent than ‘regular’ Linac
• Some replacement can be predicted
• TQA may help with prediction of these failures
Thank You