How to determine margins for planning target volume (PTV): From 2D to 3D planning in radiotherapy for head and neck cancer? Portal imaging assessment for set-up errors

Bayman E., Ataman Ö. U., Kinay M., Akman F.

Turk Onkoloji Dergisi, vol.25, no.3, pp.104-110, 2010 (Scopus) identifier

  • Publication Type: Article / Article
  • Volume: 25 Issue: 3
  • Publication Date: 2010
  • Journal Name: Turk Onkoloji Dergisi
  • Journal Indexes: Scopus
  • Page Numbers: pp.104-110
  • Keywords: Portal imaging for head and neck radiotherapy, Set-up errors
  • Istanbul Medipol University Affiliated: No


Objectives To evaluate set-up errors using Electronic Portal Imaging (EPI) for Three Dimensional Conformal Radiotherapy (3D CRT) protocol for head and neck carcinoma in Dokuz Eylül University Department of Radiation Oncology (DEUDRO). Methods Ten patients between July 2004 - September 2005 were included. Seven EPIs/5 weeks per patient were planned to evaluate by two independent observers. Differences between Digitally Reconstructed Radiography (DRR) images and EPIs measured in cranio-caudal (CC), anterior-posterior (AP) and medio-lateral (ML) directions. Random (σ) and the systematic (S) errors were calculated and used in van Herk margin formula (2.5 × σ + 0.7 × σ) for PTV margin. Results Ninety three EPIs with 186 [93 (50%) CC, 78 (42%) AP and 15 (8%) ML] measurements were evaluated. The s were AP: 2.6 mm, CC: 2.9 mm, ML: 1 mm. The Σ AP: 3.9 mm, CC: 1.8 mm, ML: 1.9 mm. PTV margins calculated were AP: 11.7 mm, CC: 6.6 mm, ML: 5.8 mm. Conclusion 3DCRT protocol for head and neck cancer was amended using these PTV margins. These maybe wide especially for IMRT, and can reduce with better immobilization systems. © 2010 Association of Oncology.