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What we have learnt

What we have learnt. Optimise IGRT Trust the number! Changes in GTV/CTV/PTV importance CTV controversies Reproducibility Software automation Workload. GTV v CTV v PTV. Of what use now?. Of what use next week?. GTV anti anatomy defines cancer CTV anatomy fixed boundaries

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What we have learnt

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  1. What we have learnt • Optimise IGRT • Trust the number! • Changes in GTV/CTV/PTV importance • CTV controversies • Reproducibility • Software automation • Workload

  2. GTV v CTV v PTV Of what use now? Of what use next week? • GTV • antianatomy • defines cancer • CTV • anatomy • fixed boundaries • defines risk • PTV • nonanatomy • geometric construct • defines field • GTV • bigger/smaller • less distinct • CTV • visible • fixed boundaries (anatomic, not 3D) • reducing volume • unchanging risk • PTV • invisible • constant margin

  3. Changes in GTV/CTV/PTV importance • requires a refined skill set • deliberate placement of lines around contours • by whatever method, and repeat it tomorrow • similar to voluming a new scan every day • Some variability in tissue contrast • deliberate placement of lines around volumes • by whatever method, and repeat it tomorrow • new challenge for RO • CTV is king • must be based on anatomical boundaries (Pixel Wars) • moves but never disappear! • clinical risk gets less not more • IMRT planning is easier! • Previous control structures • Previous DVH coverage • Seeking “perfect” conformality

  4. CTV controversies • problem of the absolute measurement • Today "I expand involved nodes by 1cm” Same expansion ??? Same border Next week Same volume

  5. Reproducibility • The Pixel Wars • Voluming by numbers • Where is the risk? • More surgical approach 1. Autocontour the fat of the neck (CT numbers 800>970) 2. Include the carotid/jugular vessels 3. Exclude the SM gland 4. Close off the LN-bearing fat at the posterior SCM 5. Remove superfluous areas CTV=1.1606 cm^3 6. Repeat the exercise CTV=1.13294 cm^3

  6. Software automation • Autocontouring software

  7. Workload/year Now If use MGRT routinely • 100 H&N • 1 RO • 100 simulations (0.5FTE) • 100 volumings (0.5FTE) • 1 RT(S) • 100 simulations (0.1FTE) • 1 RT(D) • 100 plans (0.5FTE) • 1RP • 100 QAs • 100 H&N • 1 RO • 700 simulations • 700 volumings • 1RT(S) • 700 simulations • 1 RT(D) • 400 plans • 1RP • 400 QAs

  8. Summary • MGRT • Possible, time consuming, Gratifying quality improvement • Department • Time critical teamwork; DANGER!! • RO • Workload, reproducibility (CTV), on time • RT(S) & RT(P) • On time • RP • workload

  9. Thank you

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