Results from 1069 IMRT irradiations of an anthropomorphic head and anthropomorphic head and neck phantom Andrea Molineu, Nadia Hernandez, Paola Alvarez, Geoffrey Ibbott, Jim Galvin and David Followill and David Followill
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And shipped around the world And shipped around the world pp pp
IMRT H&N Phantom IMRT H&N Phantom • Primary PTV 4 cm diameter 4 TLD • Secondary PTV 2 cm diameter Primary Primary Secondary Secondary y 2 TLD 2 TLD PTV PTV PTV PTV PTV PTV Organ at Organ at • Organ at risk Risk Risk 1 cm diameter 1 cm diameter • 1º PTV treated to 6.6 Gy 1º PTV t t d t 6 6 G 2 TLD • 2º PTV treated to 5.4 Gy • Axial and sagittal • Axial and sagittal • OAR limited to < 4.5 Gy OAR limited to < 4 5 Gy radiochromic films Designed in collaboration with RTOG; Molineu et al, IJROBP, October 2005
Criteria for credentialing Criteria for credentialing • RPC/Inst dose in PTVs: 0.93-1.07 • distance to agreement in high gradient region near OAR: 4 mm region near OAR: 4 mm Dose Dose regions Distance to Distance to agreement region
IMRT H&N Phantom Results IMRT H&N Phantom Results • 1069 irradiations were analyzed • 866 irradiations passed the criteria • 203 irradiations did not pass the criteria 203 irradiations did not pass the criteria • 730 institutions are represented 81% of irradiations passed the criteria
IMRT H&N Phantom Results cont. IMRT H&N Phantom Results cont. IMRT H&N Phantom Results cont. IMRT H&N Phantom Results cont. • 146 failed by absolute dose only • 146 failed by absolute dose only • 24 failed by DTA only • 33 failed by both absolute dose and DTA and DTA % Pixels pass p 1PTV 2PTV DTA (mm) Gamma mean 0.98 0.98 1.7 90 std dev std dev 0.048 0 048 0 042 0.042 1 9 1.9 14 14 range 0.44 – 1.23 0.40 – 1.23 0 – 17 9 - 100
Gamma calculation Gamma calculation Gamma calculation Gamma calculation plan plan gamma gamma film
Gamma calculation Gamma calculation Gamma calculation Gamma calculation plan plan gamma gamma film
Gamma criteria proposal Gamma criteria proposal Gamma criteria proposal Gamma criteria proposal • 85% of pixels pass 85% of pixels pass 7%/4mm gamma 120 100 • Use axial and sagittal g 80 films 60 40 • replace current DTA p 20 criteria 0 5 7 9 1 3 5 7 9 1 3 5 7 9 7 7 7 8 8 8 8 8 9 9 9 9 9 This is expected to decrease the current pass rate to around 75% p %
IMRT Technique IMRT Technique q Criteria Failed Pass Rate Pass Rate IMRT technique Attempts Dose and (%) Dose DTA DTA 88 88 279 279 23 23 5 5 5 5 Dynamic MLC Dynamic MLC 85 79 9 0 3 IMAT 76 613 105 17 25 Segmental 43 7 3 1 0 Solid Attenuator 92 91 6 1 0 TomoTherapy 1069 146 24 33 total
Linear Accelerator Manufacturer Linear Accelerator Manufacturer Criteria Failed Linear Pass Accelerator Rate Attempts Dose and Dose DTA Manufacturer Manufacturer (%) (%) DTA DTA 67 115 32 4 2 Elekta 69 69 131 131 31 31 4 4 6 6 Siemens Siemens 92 91 6 1 0 TomoTherapy 84 732 77 15 25 Varian 1069 146 24 33 total
Treatment Planning System Treatment Planning System g g y y Criteria Failed Treatment Pass Rate planning Attempts Dose and (%) Dose DTA system DTA 88 353 27 8 7 Eclipse 75 406 80 9 13 Pinnacle 92 91 6 1 0 TomoTherapy 75 133 17 6 10 XiO 78 86 16 0 3 Other 1069 146 24 33 total
Linear Accelerator and TPS Linear Accelerator and TPS Criteria Failed Linac/TPS Linac/TPS Pass Pass Attemp Attemp Dose and Combination Rate (%) ts Dose DTA DTA 65 65 81 8 25 5 3 3 0 0 Elekta/Pinnacle 77 22 2 1 2 Elekta/XiO 66 73 21 0 4 Siemens/Pinnacle 70 37 6 3 2 Siemens/XiO 92 91 6 1 0 HiArt/TomoTherapy 90 337 20 7 7 Varian/Eclipse 80 260 37 6 9 Varian/Pinnacle 77 74 9 2 6 Varian/XiO
Tightened criteria Tightened criteria Tightened criteria Tightened criteria—5%/4 mm 5%/4 mm 5%/4 mm 5%/4 mm Treatment Pass Rate Pass Rate planning (%) system Eclipse 71 Failures Pinnacle 55 double to 405 double to 405 TomoTherapy 78 53 XiO Other Other 56 56
Conclusions Conclusions Conclusions Conclusions • Important QA tool Important QA tool • Aids improvements to IMRT delivery • All major linear accelerator and planning All j li l t d l i systems have ability to pass
Happily ever after Happily ever after Happily ever after . . . Happily ever after . . . The investigation was supported by PHS grants The investigation was supported by PHS grants CA10953, CA81647 and CA21661 awarded by the NCI, DHHS.
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