future audit approaches - uk dosimetry audit network...2013/12/13 · •phantom setup and delivery...
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FUTURE AUDIT
APPROACHES David Bernstein
On Behalf of RTTQA IMRT Subgroup
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RTTQA IMRT SubGroup
• “To review and improve Quality Assurance of UK IMRT
trials”
• 9 Step IMRT credentialing program
• Steps 6-9 = dosimetry audit
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Dosimetry Audit by RTTQA
Physicist
TPS Tests
Clinical Plan Fluence
Measurements
Clinical Plan Dose Point
Measurements
Current Audit Procedure
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Each audit
visit: 1 day at
host centre,
including 4.5-
5hours linac
time. Additional
preparation
and analysis
time.
Current Audit Procedure
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Current Audit Procedure
PARSPORT 6 Centres
COSTAR 20 Centres
ART DECO 26+14 Centres
Each audit
visit: 1 day at
host centre,
including 4.5-
5hours linac
time. Additional
preparation
and analysis
time.
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Hierarchy of IMRT complexity or
uncertainty?
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IMRT Fluence Complexity
MU/Gy
[1]
PIMV
[2] PIMV/nnz
MI_x
[3]
MI_y
[3]
MI_xy
[4]
Least
Most
CHHIP CHHIP ARTDECO PIVOTAL COSTAR COSTAR
COSTAR COSTAR COSTAR ARTDECO PIVOTAL CHHIP
ARTDECO PIVOTAL PIVOTAL COSTAR CHHIP PIVOTAL
PIVOTAL ARTDECO PARSPORT CHHIP ARTDECO ARTDECO
PARSPORT PARSPORT CHHIP PARSPORT PARSPORT PARSPORT
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Dong et al, IMRT DP QA results [5]
27
24 447
18 200 12
3
8
12
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Hierarchy of IMRT complexity or
uncertainty?
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Reducing Audit Workload and
Streamlining • New approach to assess dosimetry for different trials and
centres needed due to increasing workload
• Can not use a hierarchical approach confidently as a
basis of reducing workload
• However can streamline the process and identify new
approach to audits
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New Approach Requirements
• Flexibility for centres
• Reduced linac time
• Independent absolute dose check
• Reflect centre participation in multiple trials with multiple
treatment methods
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New Approach Requirements
• Flexibility for centres
• Reduced linac time
• Independent absolute dose check
• Reflect centre participation in
multiple trials with multiple
treatment methods
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Postal Audit
Farmer
Chamber
Insert
Top
Insert
Base
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Postal Audit
• Solid Water phantom developed by RTTQA IMRT
Subgroup
• Equipment supplied by RTTQA/NPL
• Results analysed by RTTQA/NPL
• Phantom setup and delivery performed by host centre
• Cornerstone is the NPL Alanine service
• Modular design to allow future modifications, e.g. to
include inhomogeneities
• Fiducial markers inserted to facilitate IGRT setup
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Postal Audit Process
1 • Output using local calibrated Electrometer-Farmer Chamber
2 • Output using supplied Alanine
3 • Trial plan dose point using local Electrometer-Farmer Chamber
4 • Trial plan dose point using supplied Alanine
5 • Trial plan film measurement using supplied Gafchromic film
6 • Gafchromic Film calibration irradiation
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Audit Streamlining
Established RTTQA guidelines to determine
• When a centre is to receive an audit
• What form the audit will take
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Audit Streamlining
Yes
Yes
Yes
No
Audit Visit
Local QA
Postal
Audit
Yes
No
New TPS/
Delivery
algorithm
Previous
RTTQA
visit?
< 1year
ago?
< 3years
ago?
Audit Visit
No
No
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New Audit Visit Process
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Dosimetry Audit by RTTQA
Physicist
Clinical Plan Fluence
Measurements
Clinical Plan Dose Point
Measurements
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Work in Progress
• Pilot Alanine Audits currently taking place (Varian &
Elekta)
• Establish which subset of alanine to read out
• Resolve apparent systematic ArcCheck SemiFlex results
• To roll out both audit methods early 2014
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References • [1] ConorK.McGarry, Assessing software upgrades, plan properties and patient geometry
• using intensity modulated radiation therapy (IMRT) complexity metrics, Med.Phys. 38(4), April 2011
• [2] Martha M.Coselmon, Jean M. Moran, Jeffrey D. Radawski, and Benedick A. Fraass,
• Improved IMRT delivery efficency using intensity limits during inverse planning,Med. Phys. 32(5), May 2005
• [3] S.Webb, Use of a quantitative index of beam modulation to characterize dose conformality:illustration by a comparison of full beamlet IMRT, few-segment IMRT (fsIMRT) and conformal unmodulated radiotherapy, Phys. Med. Biol. (2003) 48 2051
• [4] N.Giorgia,F.Antonella,V.Eugenio,C.Alessandro,A.Filippo,andCLuca, ‘What is an acceptably smoothed fluence? Dosimetric and delivery considerations for dynamic sliding window IMRT, Radiation Oncology 2, 42 (2007)
• [5[ L. Dong, et al. Patient-specific point dose measurement for IMRT monitor unit verification. Radiation Oncology , 56, 3, p867-877, July 2003.
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Acknowledgements
• Emma Wells
• Yat Tsang
• Laura Ciurlionis
• Olivia Niasmith
• Elizabeth Miles
• Catharine Clark
• Nicki Groom
• Karen Venables
• Edwin Aird
• Hayley James
• John Conibear
• Teresa GuerreroUrbano
• Helen Baines
• Antony Carver