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Published byEmory Randall Modified over 9 years ago
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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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Reference calibration (NIST traceable) Correction Factors: Field size & shape Depth of target Transmission factors Treatment time Evaluated by RPC Dosimeters Evaluated by RPC visits and chart review RPC Verification of Institutions’ Delivery of Tumor Dose Tumor Dose Evaluated by RPC phantoms
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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) PhotonsElectrons OSLD/TLD (±5%) 7-11% 6-12% Visits (±3%) ~13% ~15%
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Discrepancies Regarding: Number of Institutions Receiving rec. (n = 156) Review QA Program115 (74%) Photon Field Size Dependence (small FSD)62 (40%) Wedge Factor (WF)50 (32%) Off-axis Factors (OAF)/Beam symmetry46 (29%) Electron Calibration27 (17%) Photon Depth Dose25 (16%) Electron Depth Dose18 (12%) Photon Calibration13 (8%) Review Temp/Press Correction11 (7%) Change to TG-519 (6%) Electron Cone Ratios8 (5%) Using Multiple Sets of Data8 (5%) Discrepancies Discovered (Jan. ’05 – Mar. ’11) On-Site Dosimetry Review Audit
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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) Liver (6) H&N (30) SRS Head (10) Spine (8)
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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 PhantomPatient Benefits of RPC Phantoms PhantomPatient
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Phantom Results PhantomH&NProstateSpineLung Irradiations1139313120458 Pass 686 (79%) 162 (82%) 22 (63%) 178 (75%) Fail187351359 Criteria7%/4mm 5%/3m m 5%/5m m RTOG Inst. Acceptable 557 (54%) 206 (20%) 83 (8%) 289 (28%) Pass 928 (81%) 265 (85%) 78 (65%) 361 (79%) Fail211484297 Comparison between institution’s plan and delivered dose.
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Phantom Results Comparison between institution’s plan and delivered dose. H&NProstateSpineLung Irradiations (all years)1139313120458 Pass (all years)928 (81%)265 (85%)78 (65%)361 (79%) Fail (all years)211484297 Irradiations (2011)109564080 Pass (2011)101 (93%)45 (80%)31 (78%)68 (85%) Fail (2011)811912 Criteria7%/4mm 5%/3mm5%/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/ Don’t understand process 3.Communication/Fear of punishment 4.Training/Failure to ask for help 5.Can’t accept the fact that an error could be mad WHO report on “Radiotherapy Risk Profile” states that 60% of all radiotherapy incidents are attributable to human error. Human Errors!
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Let’s get past these hurdles! Questions?
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