Details

Autor(en) / Beteiligte

• Huang, Kitty, M.D.C.M., M.Sc
• Palma, David A., M.D., M.Sc., F.R.C.P.C., Ph.D
• Scott, Danielle, M.R.T.T., B.Sc
• McGregor, Danielle, B.Sc. (Hons.), M.R.T.T
• Gaede, Stewart, Ph.D
• Yartsev, Slav, Ph.D
• Bauman, Glenn, M.D., F.R.C.P.C
• Louie, Alexander V., M.D
• Rodrigues, George, M.D., F.R.C.P.C., M.Sc

Titel

Inter- and Intrafraction Uncertainty in Prostate Bed Image-Guided Radiotherapy

Ist Teil von

• International journal of radiation oncology, biology, physics, 2012-10, Vol.84 (2), p.402-407

Ort / Verlag

New York, NY: Elsevier Inc

Erscheinungsjahr

2012

Quelle

MEDLINE

Beschreibungen/Notizen

• Purpose The goals of this study were to measure inter- and intrafraction setup error and prostate bed motion (PBM) in patients undergoing post-prostatectomy image-guided radiotherapy (IGRT) and to propose appropriate population-based three-dimensional clinical target volume to planning target volume (CTV–PTV) margins in both non-IGRT and IGRT scenarios. Methods and Materials In this prospective study, 14 patients underwent adjuvant or salvage radiotherapy to the prostate bed under image guidance using linac-based kilovoltage cone-beam CT (kV-CBCT). Inter- and intrafraction uncertainty/motion was assessed by offline analysis of three consecutive daily kV-CBCT images of each patient: ( 1 ) after initial setup to skin marks, ( 2 ) after correction for positional error/immediately before radiation treatment, and ( 3 ) immediately after treatment. Results The magnitude of interfraction PBM was 2.1 mm, and intrafraction PBM was 0.4 mm. The maximum inter- and intrafraction prostate bed motion was primarily in the anterior–posterior direction. Margins of at least 3–5 mm with IGRT and 4–7 mm without IGRT (aligning to skin marks) will ensure 95% of the prescribed dose to the clinical target volume in 90% of patients. Conclusions PBM is a predominant source of intrafraction error compared with setup error and has implications for appropriate PTV margins. Based on inter- and estimated intrafraction motion of the prostate bed using pre- and post-kV-CBCT images, CBCT IGRT to correct for day-to-day variances can potentially reduce CTV–PTV margins by 1–2 mm. CTV–PTV margins for prostate bed treatment in the IGRT and non-IGRT scenarios are proposed; however, in cases with more uncertainty of target delineation and image guidance accuracy, larger margins are recommended.