Geometric and dosimetric evaluations of an online image-guidance strategy for 3D-CRT of prostate cancer.

Published

Journal Article

PURPOSE: To evaluate an online image-guidance strategy for conformal treatment of prostate cancer and to estimate margin-reduction benefits. METHODS AND MATERIALS: Twenty-eight patients with at least 16 helical computed tomography scans were each used in this study. Two prostate soft-tissue registration methods, including sagittal rotation, were evaluated. Setup errors and rigid organ motion were corrected online; non-rigid and intrafraction motion were included in offline analysis. Various clinical target volume-planning target volume (CTV-PTV) margins were applied. Geometrical evaluations included analyses of isocenter shifts and rotations and overlap index. Dosimetric evaluations included minimum dose and equivalent uniform dose (EUD) for prostate and gEUD for rectum. RESULTS: Average isocenter shift and rotation were (dX,dY,dZ,theta) = (0.0 +/- 0.7,-1.1 +/- 4.0,-0.1 +/- 2.5,0.7 degrees +/- 2.0 degrees ) mm. Prostate motion in anterior-posterior (AP) direction was significantly higher than superior-inferior and left-right (LR) directions. This observation was confirmed by isocenter shift in perspectives AP (1.8 +/- 1.8 mm) and RL (3.7 +/- 3.0 mm). Organ motion degrades target coverage and reduces doses to rectum. If 2% dose reduction on prostate D(99) is allowed for 90% patients, then minimum 3 mm margins are necessary with ideal image registration. CONCLUSIONS: Significant margin reduction can be achieved through online image guidance. Certain margins are still required for nonrigid and intrafraction motion. To further reduce margin, a strategy that combines online geometric intervention and offline dose replanning is necessary.

Full Text

Duke Authors

Cited Authors

  • Wu, Q; Ivaldi, G; Liang, J; Lockman, D; Yan, D; Martinez, A

Published Date

  • April 1, 2006

Published In

Volume / Issue

  • 64 / 5

Start / End Page

  • 1596 - 1609

PubMed ID

  • 16580509

Pubmed Central ID

  • 16580509

International Standard Serial Number (ISSN)

  • 0360-3016

Digital Object Identifier (DOI)

  • 10.1016/j.ijrobp.2005.12.029

Language

  • eng

Conference Location

  • United States