Download Commissioning of linear accelerators: From acceptance to first

2011 Award Recipient
Commissioning of linear
accelerators: From acceptance to
first clinical treatment
Indrin J. Chetty PhD, FAAPM
Professor and Director of Medical Physics
Dept. of Radiation Oncology
Henry Ford Health System
Disclosure/COI
My department receives research support from:
• Varian Medical Systems
• Philips HealthCare
Where should we begin?
Review guidance documents and relevant literature
AAPM
TG No. 45
Nath
et al.
AAPM TG No. 45 Nath et al.
Commissioning of Treatment Planning Systems
Routine QA of CT-based IGRT
Routine QA of Linear accelerators
The Edge and TrueBeam Systems
Functionality
• Immobilization devices for cranial and extracranial
SRS and SBRT
• Flattened and Flattening filter free (FFF) beams for
high dose rate delivery, 10X FFF (2400 MU/min)
• Micro-MLC with leaf widths down to 2.5 mm
and field size of 22x40 cm
• six deg. of freedom (6DOF) robotics couch
•
Several different imaging modalities for accurate
localization including MV EPID, kV On-board imager,
optical-based systems and EM-based (Calypso) tracking
Small field measurements highly complex and challenging!!!
Survey of 40 identical radiosurgery units
Courtesy: T. Solberg, Univ of Pennsylvania
Small field sizes: detector volume and electron range
1x1 cm2 field
W. Laub and T. Wong, Med. Phys. 30:341-347 (2003)
Small field dosimetry measurements require
utmost care!
Small Field Depth
doses from J Kim et al.
JACMP 13: 2012
Small Field Depth
doses from J Kim et al.
JACMP 13: 2012
10x10 mm
Detector Limitations
change
Courtesy: T. Solberg, Univ of Pennsylvania
“Daisy Chain” normalization
Khelashvili et al. JACMP:13: (2012)
Courtesy: Cindy Qin, Henry Ford Hospital
What can be done during commissioning?
Select detectors appropriate for the type of data
C Glide-Hurst, M Bellon, R. Foster et al. Medical Physics 40 (2013)
Select detectors appropriate for the type of data
C Glide-Hurst, M Bellon, R. Foster et al. Medical Physics 40 (2013)
Compare your data with that from other institutions
Small field photon output factors
C Glide-Hurst, M Bellon, R. Foster et al. Medical Physics 40 (2013)
Compare your data with that from other institutions
C Glide-Hurst, M Bellon, R. Foster et al. Medical Physics 40 (2013)
Treatment Planning: Definition of Targets and OARs
MRI Distortion
Courtesy: T. Solberg, Univ of Pennsylvania
MRI/CT fusion Verification
Courtesy: T. Solberg, Univ of Pennsylvania
SRS and SBRT: dose calculation algorithm
Recommendation of AAPM TG Report No. 101 (Benedict et al Med
Phys 37: 2010)…..Algorithms accounting for 3D scatter (e.g.
convolution/superposition, Monte Carlo) perform adequately in
most situations, including (in many cases) under circumstances
where there is a loss of e’ equilibrium such as lung/tissue interface
or tumor margin in lung medium. Pencil beam algorithms
accounting only for 1D scatter are not recommended….
Minimum field size (3.5 cm) and energy (low X) constraints:
RTOG 0236, 0813, 0915
Treatment Delivery: Isocentricity and the MLC
J Kim et al. JACMP 13: 2012
Isocentricity (Winston/Lutz Test)
Winston-Lutz test with fields defined by the MLC
J Kim et al.
JACMP 13: 2012
W-L test variation
over 30 days
Wen et al. JACMP
2015, in press
Commissioning of localization systems
How good is the image quality?
J Kim et al.
JACMP 13:
2012
MV image quality:
Low Contrast Detectability
 Las Vegas phantom on 2.5x and 6xFFF: constancy check
2.5 MV
6MV FFF
Note: content filter applied
Courtesy: Kwang Song, PhD (HFH)
kV and 2.5MV image quality
Leeds phantom (spatial resolution and low contrast detectability)
kV
2.5 MV
Note: content filter applied
Courtesy: Kwang Song, PhD (HFH)
CBCT image quality
Spatial resolution
Courtesy: Kwang Song, PhD (HFH)
CBCT image quality
HU sensitivity
Compare HU values at different materials between expected and measured
Courtesy: Kwang Song, PhD (HFH)
CBCT image quality
HU Uniformity
Compare HU values at 5 positions between base line and the current
Courtesy: Kwang Song, PhD (HFH)
Courtesy: Kwang Song, PhD (HFH)
Courtesy: Kwang Song, PhD (HFH)
Courtesy: Kwang Song, PhD (HFH)
End-to-end Tests: Image-based: Hidden Target Tests
Image known “hidden targets” with multiple systems
Define Isocenter
• Insert 2mm BB
• Setup with various
errors
Phantom Localization
• Floor mounted Xray
• CBCT
Courtesy: N. Wen, Henry Ford Hospital
Determine setup
error
• AP/Lat MV films
• Statistics
Localization systems
Comparison between floor mounted, planar x-ray and CBCT
Average values (mm) based on 12 measurements in each plane
Translations
Planar x-ray
CBCT
Rotations
6D-robotics
19/24 cases were
within ±0.3°
Max. deviation was
0.7 deg. about the
P/A axis
J Kim et al. JACMP 13: 2012
Dosimetric Impact of Rotations
711 ETX 3D/2D
registrations
combined in all
directions
J Kim et al. JACMP
13: 2012
Commissioning of a 6D robotics couch with rails
Gardner et al. Journal of Applied Clinical Physics (JACMP), In Press 2015
Commissioning of a 6D robotics couch with rails
Rel.
attenuation of
the couch with
rails “in” and
“out”.
Commissioning of the QFIX couch top: CT scan
CT scan showing relevant dimensions (b) “rails out” position,
(c) periodic structure of the rails
Commissioning of a 6D robotics couch with rails
Without
model
With
model
Garder, Gulam et
al. JACPM 2015
in press
End-to-end Testing: Dosimetric
Imaging/sim
Image-based localization
Tx planning
Eval of planned and delivered doses
Courtesy: T. Solberg, Univ of Pennsylvania
End-to-end testing:
Dose
J Kim et al.
JACMP 13: 2012
Measurement Suite: AAPM TG-119: Ezzell et al. Med Phys 36: 2009
C Glide-Hurst, M Bellon, R. Foster et al. Medical Physics 40 (2013)
End-to-end
testing: Dose
C Glide-Hurst and
M Bellon, R Foster
et al. Med Phys 40
(2013)
Independent Verification: IROC (RPC) Phantoms
Courtesy: T. Solberg, Univ of Penn
Independent Verification: IROC (RPC) Phantoms
Phantom
Lung
Phantom
Spine
Phantom
TLD
Location
PTV_TLD_
sup
PTV_TLD_i
nf
IROC vs Inst
Criteria
Film Plane
0.97
0.92-1.02
Axial
Coronal
Gamma
Index
100%
100%
0.98
0.92-1.02
Sagittal
100%
≥80%
PTV_TLD_
sup_ant
1.01
0.93-1.07
Axial
90%
≥85%
PTV_TLD_i
nf_ant
1.00
0.93-1.07
PTV_TLD_
sup_post
1.00
0.93-1.07
Sagittal
91%
≥85%
PTV_TLD_i
nf_post
0.99
0.93-1.07
Wen et al. JACMP 2015, in press
Criteria
≥80%
≥80%
Case Study: Single Isocenter Multiple
Brain Mets
 46 yr old male
 high grade metastatic
eurothelial tumor of the
urinary bladder
 Three mets in the left frontoparietal region
 Prescription: 18Gy @ 90%
 3 partial arcs (0°, 30° and
60°)
Courtesy: Winston Wen, PhD (HFH)
Patient Specific QA: Gafchromic (EBT) film
PATIENT PLAN
Point
Dose
Plan MU
Rdg (Meas)
[nC]
Dose (Meas) Dose (iPlan)
[Gy]
[Gy]
Beam 1
2141
1.9008
4.6122
4.536
Beam 2
2198
1.3322
3.2325
3.205
Beam 3
2101
3.0400
7.3764
7.453
Axial
Plane
Coronal
Plane
Courtesy: Winston Wen, PhD (HFH)
Diff.
1.68%
0.86%
-1.03%
Image Verification: Treatment
VRT
(cm)
LNG
(cm)
LAT
(cm)
ROT
(deg)
PITCH
(deg)
ROLL
(deg)
CBCT Shifts
-0.32
-0.22
-0.05
-0.1
-1.1
-0.9
PRE-TREATMENT
VERIFICATION (G 0 CCW)
0.01
0.01
-0.01
-0.2
0.1
0.4
MID-TREATMENT
VERIFICATION: BEAM 2
(G 180 CCW)
-0.02
-0.03
0.01
0.1
0.2
0.1
MID-TREATMENT
VERIFICATION: BEAM 3
(G 120 CCW)
-0.01
-
0.03
-
0.6
0.4
Courtesy: Winston Wen, PhD (HFH)
Case Study: Single Isocenter Multiple
Lesions- Lung
 69 yr old female
 NSCLC
 Two nodules in the
right upper-middle
lobes 10Gy x 4 fr
 Right Hilum 6Gy x 4
fr
 Two partial arcs
Courtesy: Winston Wen, PhD (HFH)
Patient Specific QA: Gafchromic Film
Plan MU
Rdg
(Meas)
[nC]
Dose
(Meas)
[Gy]
Dose
(iPlan)
[Gy]
Beam 1
1968
1.5747
3.7593
4.041
Beam 2
2133
1.4144
3.3766
3.283
Total
4101
2.989
7.1360
7.3240
PATIENT PLAN
Point
Dose
Gamma
2%/2mm
Passing Rate 99.1%
Diff
-6.97%
2.85%
-2.57%
Image Verification
Courtesy: Winston Wen, PhD (HFH)
Summary
Perform comprehensive commissioning and testing all aspects
related to simulation, treatment planning, image-guidance
and treatment delivery. For SBRT, this includes the motion
management systems
Commissioning should be facilitated through the record/verify
system in clinical mode
End-to-end testing of image-based localization and the entire
process, from simulation to dose delivery must be performed
Independent verification of the beam model data, absolute
calibration, and end-to-end testing is helpful
Acknowledgements
Tim Solberg, PhD (Univ of Pennsylvania)
Henry Ford Hospital:
Ning (Winston) Wen, PhD
Carri Glide-Hurst, PhD
Kwang Song, PhD
Stephen Gardner, MS
James Gordon, PhD
Other Colleagues
Cecilia Haddad, PhD
Brazilian Society of Radiation Oncology
Varian Medical Systems, Palo Alto, CA
Thank you!