Radiological Physics Center

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Radiological Physics Center
David Followill, Ph.D. and RPC Staff
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Radiological Physics Center

• Formed in 1968 and located at
  MD Anderson Cancer Center
  (1 of 12 longest
  running grants).
• Our Mission is to assure NCI and cooperative
  groups that institutions participating in
  clinical trials deliver prescribed radiation
  doses that are comparable and consistent,
  (minimize dose uncertainty), make corrections and
  report findings to the community.
• Funded continuously for 44 years as cooperative
  clinical trial groups have changed and expanded
  internationally
• Use of remote and onsite dosimetry audits

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RPC Scope of Monitoring

• Monitoring 1888 inst. participating in clinical
  trials - includes 210 non-North American sites
  41 countries (since 2006 45?)
  - 23,000 beams
  -
  3500 machines

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Components of RPC QA Program

• 1. Remote audits of machine output
• 1,888 institutions, 14,000 beams measured with
  TLD and OSLD in North America and Internationally
• 2. Patient Treatment record reviews
• 474 charts reviewed for GOG, NSABP, NCCTG, RTOG
  (brachytherapy)
• 3. On-site dosimetry reviews
• 41 institutions visited in 2011
  (150
  accelerators/450 beams measured)
• 4. Credentialing - Phantoms
• 500 irradiations in 2011

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RPC Verification of Institutions Delivery of
Tumor Dose
Reference calibration (NIST traceable)
Evaluated by RPC Dosimeters
Correction Factors Field size shape Depth of
target Transmission factors Treatment time
Evaluated by RPC visits and chart review
Evaluated by RPC phantoms
Tumor Dose
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So, how are we doing?
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OSLD/TLD Beam Output Checks
3-4 of the beams require a repeat
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Comprehensive On-Site Audits
Reference Beam Calibration Percent of Inst. with
1 beam out of Criteria (since
2002) Photons Electrons OSLD/TLD (5)
7-11 6-12 Visits (3) 13 15
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On-Site Dosimetry Review Audit
Discrepancies Discovered (Jan. 05 Mar. 11)
Discrepancies Regarding Number of Institutions Receiving rec. (n 156) Number of Institutions Receiving rec. (n 156)
Review QA Program Review QA Program 115 (74)
Photon Field Size Dependence (small FSD) Photon Field Size Dependence (small FSD) 62 (40)
Wedge Factor (WF) Wedge Factor (WF) 50 (32)
Off-axis Factors (OAF)/Beam symmetry Off-axis Factors (OAF)/Beam symmetry 46 (29)
Electron Calibration Electron Calibration 27 (17)
Photon Depth Dose Photon Depth Dose 25 (16)
Electron Depth Dose Electron Depth Dose 18 (12)
Photon Calibration Photon Calibration 13 (8)
Review Temp/Press Correction Review Temp/Press Correction 11 (7)
Change to TG-51 Change to TG-51 9 (6)
Electron Cone Ratios Electron Cone Ratios 8 (5)
Using Multiple Sets of Data Using Multiple Sets of Data 8 (5)
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Treatment record reviews

• RPC performs independent retrospective review and
  recalculation of doses for RTOG, NCCTG and GOG
  brachy. patients
• Errors in dose calculation and doses reported to
  study groups are discovered and corrected
• The RPC review has resulted in changing the
  reported dose on 546 (27) of the1993
  protocol patients reviewed since 2005.
• - 13 are EBRT dose errors
  -
  87 are brachytherapy dose errors

We revise the dose data in 1 of every 3 charts
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RPC Phantoms
Pelvis (10)
Thorax (10)
Spine (8)
HN (30)
Liver (6)
SRS Head (10)
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Benefits of RPC Phantoms
Phantom
Patient

• Independent end to end audit
• Imaging
• Planning/dose calculation
• Setup
• delivery
• Uniform phantoms and dosimeters
• Standardized analysis
• Uniform pass/fail criteria
• Allows inst. to inst. comparison
• Established infrastructure

Phantom
Patient
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Phantom Results
Comparison between institutions plan and
delivered dose.
Phantom HN Prostate Spine Lung
Irradiations 1139 313 120 458
Pass 686 (79) 162 (82) 22 (63) 178 (75)
Fail 187 35 13 59
Criteria 7/4mm 7/4mm 5/3mm 5/5mm
RTOG Inst. Acceptable 557 (54) 206 (20) 83 (8) 289 (28)
Pass 928 (81) 265 (85) 78 (65) 361 (79)
Fail 211 48 42 97
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Phantom Results
Comparison between institutions plan and
delivered dose.
HN Prostate Spine Lung
Irradiations (all years) 1139 313 120 458
Pass (all years) 928 (81) 265 (85) 78 (65) 361 (79)
Fail (all years) 211 48 42 97
         
Irradiations (2011) 109 56 40 80
Pass (2011) 101 (93) 45 (80) 31 (78) 68 (85)
Fail (2011) 8 11 9 12
Criteria 7/4mm 7/4mm 5/3mm 5/5mm
Failure rate doubles going to 5/3mm criteria
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Why do we continue to find errors?

1. Too busy
2. Advanced technology/ Dont understand process
3. Communication/Fear of punishment
4. Training/Failure to ask for help
5. Cant accept the fact that an error could be mad

Human Errors!
WHO report on Radiotherapy Risk Profile states
that 60 of all radiotherapy incidents are
attributable to human error.
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Lets get past these hurdles! Questions?