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Enhancing IGRT: Key Insights on GTV, CTV, and PTV for Improved Oncology Practices

This comprehensive overview addresses critical elements of Image-Guided Radiation Therapy (IGRT), focusing on tumor delineation, including Gross Tumor Volume (GTV), Clinical Target Volume (CTV), and Planning Target Volume (PTV). Key topics include the importance of reproducibility, the challenges of contouring, and software automation for efficiency. We delve into anatomical boundaries versus non-anatomical definitions and their implications for clinical risk management. Emerging trends and controversies in CTV delineation are discussed to foster improved oncological outcomes and workflow optimization.

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Enhancing IGRT: Key Insights on GTV, CTV, and PTV for Improved Oncology Practices

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Presentation Transcript

  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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