Clinical comparison of positional accuracy and stability between dedicated versus conventional masks for immobilization in cranial stereotactic radiotherapy using 6-degree-of-freedom image guidance system-integrated platform

Kazuhiro Ohtakara, Shinya Hayashi, Hidekazu Tanaka, Hiroaki Hoshi, Masashi Kitahara, Katsuya Matsuyama, Hitoshi Okada

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

Purpose: To compare the positioning accuracy and stability of two distinct noninvasive immobilization devices, a dedicated (D-) and conventional (C-) mask, and to evaluate the applicability of a 6-degrees-of-freedom (6D) correction, especially to the C-mask, based on our initial experience with cranial stereotactic radiotherapy (SRT) using ExacTrac (ET)/Robotics integrated into the Novalis Tx platform. Materials and methods: The D- and C-masks were the BrainLAB frameless mask system and a general thermoplastic mask used for conventional radiotherapy such as whole brain irradiation, respectively. A total of 148 fractions in 71 patients and 125 fractions in 20 patients were analyzed for the D- and C-masks, respectively. For the C-mask, 3D correction was applied to the initial 10 patients, and thereafter, 6D correction was adopted. The 6D residual errors (REs) in the initial setup, after correction (pre-treatment), and during post-treatment were measured and compared. Results: The D-mask provided no significant benefit for initial setup. The post-treatment median 3D vector displacements (interquatile range) were 0.38 mm (0.22, 0.60) and 0.74 mm (0.49, 1.04) for the D- and C-masks, respectively (p < 0.001). The post-treatment maximal translational REs were within 1 mm and 2 mm for the D- and C-masks, respectively, and notably within 1.5 mm for the C-mask with 6D correction. The pre-treatment 3D vector displacements were significantly correlated with those for post-treatment in both masks. Conclusions: The D-mask confers positional stability acceptable for SRT. For the C-mask, 6D correction is also recommended, and an additional setup margin of 0.5 mm to that for the D-mask would be sufficient. The tolerance levels for the pre-treatment REs should similarly be set as small as possible for both systems.

Original languageEnglish
Pages (from-to)198-205
Number of pages8
JournalRadiotherapy and Oncology
Volume102
Issue number2
DOIs
Publication statusPublished - 02-2012

All Science Journal Classification (ASJC) codes

  • Hematology
  • Oncology
  • Radiology Nuclear Medicine and imaging

Fingerprint Dive into the research topics of 'Clinical comparison of positional accuracy and stability between dedicated versus conventional masks for immobilization in cranial stereotactic radiotherapy using 6-degree-of-freedom image guidance system-integrated platform'. Together they form a unique fingerprint.

  • Cite this