Dosimetry for IMRT

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Problems with Conventional Output Factors Standard Reference Conditions Small Field Conditions • Small field openings p g obscure the source which is difficult to measure and error prone. • Amount of phantom scatter changes as well as lateral disequilibrium disequilibrium. • Partial volume effects can mask machine output factor.
Scan Phantom Across a Narrow Beam Jaw field width (FW) • If the source were a point source, source the measured primary dose would be directly proportional to the jaw field width and inversely proportional to the scan speed. • Nearly equal phantom scatter conditions <strong>for</strong> all jaw settings. • No partial volume effects once scanning is complete. Beam’s eye view
Page 1: Dosimetry for IMRT Thomas Rockwell
Page 4 and 5: Outline • Dosimetry Issues Releva
Page 6 and 7: Non-Uniform Intensity Changes the E
Page 8 and 9: Signal (fC) 12000 10000 8000 6000 4
Page 10 and 11: Outpuut Factorr 0.9 0.8 00.7 0.6 05
Page 12 and 13: High Uncertainty in Output Factors
Page 16 and 17: Animation of Scanning Path From the
Page 18 and 19: Animation of Scanning Path From the
Page 20 and 21: Dose D Ratio Dosse Impact of Source
Page 22 and 23: No Difference Between Water and Sol
Page 24 and 25: Small Vs. Farmer Chambers A1SL: 0.0
Page 26 and 27: The Same Technique Could Be Applied
Page 28 and 29: Measurements Would Benchmark Source
Page 30 and 31: Audit for TRS 398 Reference Dosimet
Page 32 and 33: IMRT Is About Using Small Fields In
Page 34 and 35: Meeting for the Dosimetry Code of P
Page 38 and 39: Examples of Small and Novel Fields
Page 40 and 41: Calculate Using MC Using method of
Page 42 and 43: Dose Calibration Correction Factor
Page 44 and 45: “Effective kQ” for Tomo 1. Dete
Page 46 and 47: ICRU Committee on IMRT Sponsors •
Page 48 and 49: QA for IMRT • Appropriate QQA of
Page 50 and 51: 1 mm Bands Leaf Positioning Errors
Page 52 and 53: Radiation Field Edge Offset 0.7mm o
Page 54 and 55: Dynamic Multileaf Collimator MLC (D
Page 56 and 57: TomoTherapy py Leaf Latencyy • To
Page 58 and 59: End-to-End QA
Page 60 and 61: Dose (GGy) On and Off-Axis Results
Page 62 and 63: Delivery QA Panel
Page 64 and 65:
NNote t th the High Gradients Compa
Page 66 and 67:
Independent Calculation
Page 68 and 69:
Gamma Function � ( r , r ) �{[
Page 70 and 71:
Molineu et al IJROBP 2005 Ibott et
Page 72 and 73:
Dm/Dc 1.2 1.15 1.1 1.05 1 0.95 0.9
Page 74 and 75:
Frequency Inter-Institution Dose Ac
Page 76 and 77:
QA Accuracy y for IMRT • Previous
Page 78 and 79:
Monitor Units Calculations for MMod
Page 80 and 81:
Monitor Backscatter for Square On O
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Dosimetry for IMRT

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