Poster - 48: Clinical assessment of ExacTrac stereoscopic imaging of spine alignment for lung SBRT
- Nova Scotia Cancer Centre, Nova Scotia Cancer Centre, Nova Scotia Cancer Centre (Canada)
Purpose: To evaluate the validity of using spine as a surrogate for tumor positioning with ExacTrac stereoscopic imaging in lung stereotactic body radiation therapy (SBRT). Methods: Using the Novalis ExacTrac x-ray system, 39 lung SBRT patients (182 treatments) were aligned before treatment with 6 degrees (6D) of freedom couch (3 translations, 3 rotations) based on spine matching on stereoscopic images. The couch was shifted to treatment isocenter and pre-treatment CBCT was performed based on a soft tissue match around tumor volume. The CBCT data were used to measure residual errors following ExacTrac alignment. The thresholds for re-aligning the patients based on CBCT were 3mm shift or 3° rotation (in any 6D). In order to evaluate the effect of tumor location on residual errors, correlations between tumor distance from spine and individual residual errors were calculated. Results: Residual errors were up to 0.5±2.4mm. Using 3mm/3° thresholds, 80/182 (44%) of the treatments required re-alignment based on CBCT soft tissue matching following ExacTrac spine alignment. Most mismatches were in sup-inf, ant-post, and roll directions which had larger standard deviations. No correlation was found between tumor distance from spine and individual residual errors. Conclusion: ExacTrac stereoscopic imaging offers a quick pre-treatment patient alignment. However, bone matching based on spine is not reliable for aligning lung SBRT patients who require soft tissue image registration from CBCT. Spine can be a poor surrogate for lung SBRT patient alignment even for proximal tumor volumes.
- OSTI ID:
- 22689353
- Journal Information:
- Medical Physics, Journal Name: Medical Physics Journal Issue: 8 Vol. 43; ISSN 0094-2405; ISSN MPHYA6
- Country of Publication:
- United States
- Language:
- English
Similar Records
SU-E-J-34: Setup Accuracy in Spine SBRT Using CBCT 6D Image Guidance in Comparison with 6D ExacTrac
SU-E-J-259: Quantification of Rotational Localization Offset in Radiation Therapy
Is ExacTrac x-ray system an alternative to CBCT for positioning patients with head and neck cancers?
Journal Article
·
Mon Jun 15 00:00:00 EDT 2015
· Medical Physics
·
OSTI ID:22494060
SU-E-J-259: Quantification of Rotational Localization Offset in Radiation Therapy
Journal Article
·
Sun Jun 01 00:00:00 EDT 2014
· Medical Physics
·
OSTI ID:22339789
Is ExacTrac x-ray system an alternative to CBCT for positioning patients with head and neck cancers?
Journal Article
·
Thu Nov 14 23:00:00 EST 2013
· Medical Physics
·
OSTI ID:22230759