CobRaLeaf 2012

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CobRaLeaf 2012

  1. 1. AMPICON 2012Mangalore, India01.11.2012 A manual Multileaf Collimator for use in Cobalt-60 teletherapy Gernot Echner, DKFZ Heidelberg Stefan Ueltzhoeffer, Precisis AG
  2. 2. G. EchnerDept. of Med. Phys. in RT11/12/2012 | Page 2 Introduction • Recent reports: Need for affordable Radiotherapy in LMI1 Rosenblatt et.al (IAEA), Radiotherapy&Oncology 104, (2012) 269- 271 • Quest for MLC for Co-60 machines IAEA, Radiation Oncology Physics Handbook, 2005 • Industrial partner for development: Precisis AG, Germany
  3. 3. G. EchnerDept. of Med. Phys. in RT11/12/2012 | Page 3 Background / Development constraints • Adaptable to Co-60 • Up-to-date Dosimetry: <2% Leakage, Single Focus, Rounded Leafends (small Penumbra) • Field size 20x30 cm2 • Power source independent / Mechanical MLC • Low Maintenance: Stable mechanism, Standard parts • Low cost Image: © Ideenkoch - Fotolia.com
  4. 4. G. EchnerDept. of Med. Phys. in RT11/12/2012 | Page 4 Technical Solution (1) Drive: Closed-loop Pneumatics Leaf Material: Brass • Optimal “Spring” properties Density = 8.47 g/cm3 • High force μCuZn39Pb3 = 0.4311 cm-1 HVL = 1.6079 cm • Low wearing 6*HVL = 9.65 cm ≙ 1.563 %
  5. 5. G. EchnerDept. of Med. Phys. in RT11/12/2012 | Page 5 Technical Solution (2) • Drive integrated into Leaves (Compactness) • Workflow: Mechanical field adjustment
  6. 6. G. EchnerDept. of Med. Phys. in RT11/12/2012 | Page 6 Dosimetry: Material & Methods Material • PTW Ion chamber • Theratron Elite80 (Ø1.5cm) & Theratronics Equinox (Ø2.0cm) • GafChromic EBT film • PTW Phantom/Virtual Water Methods • 80cm/85cm/100cm SSD • Varying field size • pdd & skin dose • Interleaf & End2End Leakage • Penumbra: 80% / 20% Images: © Precisis AG
  7. 7. G. EchnerDept. of Med. Phys. in RT11/12/2012 | Page 7 Dosimetry: Results Penumbra Penumbra with depth Penumbra with fieldsize Penumbra / cm Penumbra / cm Source Ø 2.0 cm: Source Ø 2.0 cm, Depth 10 cm Reference Penumbra: 0.85 cm Penumbra: 0.69 cm – 1.39 cm Source Ø 1.5 cm: Reference Penumbra: 0.55 cm
  8. 8. G. EchnerDept. of Med. Phys. in RT11/12/2012 | Page 8 Dosimetry: Results Leakage Interleaf Leakage End2End Gap Average Leakage ~1.5% End2End Gap ~5% Max < 3% Improved planned
  9. 9. G. EchnerDept. of Med. Phys. in RT11/12/2012 | Page 9 Summary Features: • Drive: Closed-loop Pneumatics, power independent • Field size: 20cm x 30cm • Leaf width: 10mm • Focus: Single focus + rounded leaf ends • Penumbra: < 10mm (Reference Field) • Leakage: < 2% • Compact design (65cm x 35cm x 12,5cm; 45kg) Marketed by Precisis AG as „Cob(alt)Ra(diation)Leaf“
  10. 10. G. EchnerDept. of Med. Phys. in RT11/12/2012 | Page 10 Outlook • mark -> patient treatment • Automatic Interlocking system • Improve ergonomics (easier movement) • Adaptation also to non-Theratronics machines Image: © Anatoly Maslennikov - Fotolia.com
  11. 11. G. EchnerDept. of Med. Phys. in RT11/12/2012 | Page 11 Acknowledgments Thank you for your attention Martin Baumann1, Gernot Echner1, Armin Runz 1, Marco Langhans1, Roland Schwandtner2, Dr. Jozef Kurzeja2, Prof. Irenaeus Admietz2, Mr. Stefan Ueltzhoeffer3, Andrei Ciresianu4, Mark Xu4, Shawn Luimes4, Prof. Wolfgang Schlegel1 1Deutsches Krebsforschungszentrum, Heidelberg 2Klinikf.Strahlentherapie, Evangelisches Krankenhaus Witten 3Precisis AG, Heidelberg 4Best Theratronics, Ottawa, Canada
  12. 12. G. EchnerDept. of Med. Phys. in RT11/12/2012 | Page 12 Backup Information Skin dose for 85 cm SSD Equinox Jaw size Field size Skin dose, 85 cm SSD Skin dose, 100 cm SSD (cm) 5x5 54,70% 54,70% 6x6 10x10 59,90% 58,70% 12x12 20x20 79,50% 74,50% 25x25 20x30 79,40% Properties Tungsten (Densimet®, Plansee) Density: 18.0 g/cm3 Minimum Attenuation w/o coherent scattering (cm2/g) for E=1.332 MeV: 0.0521 μW= 0.9378 cm-1 HVL = ln2/μ=0.739 cm 6*HVL ( Residual:1.563 %) = 4.43 cm (target) Residual: 2.0 % -> 5.644 HVL = 4.17 cm (minimum) Fieldsize Study 100.00% Tumor/PTV Co-60 80.00% => Linac_EN Linac_DE Approx. 60.00% Cases Gesamt 80% Maximum 40.00% of edge length 20.00% cases 0.00% treatabl 10cm 20cm 30cm 40cm e in 1 Max. Edge length Maximum Edge length is >= field

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