A new approach to quantifying lung damage after stereotactic body radiation therapy
Authors: Palma, David A.; van Söörnsen de Koste, John R.; Verbakel, Wilko F. A. R.; Senan, Suresh
Source: Acta Oncologica, Volume 50, Number 4, May 2011 , pp. 509-517(9)
Publisher: Informa Healthcare
Radiological pneumonitis and fibrosis are common after stereotactic body radiotherapy (SBRT) but current scoring systems are qualitative and subjective. We evaluated the use of CT density measurements and a deformable registration tool to quantitatively measure lung changes post-SBRT. Material and methods. Four-dimensional CT datasets from 25 patients were imported into an image analysis program. Deformable registration was done using a B-spline algorithm (VelocityAI) and evaluated by landmark matching. The effects of respiration, contrast, and CT scanner on density measurements were evaluated. The relationship between density and clinician-scored radiological pneumonitis was assessed. Results. Deformable registration resulted in more accurate image matching than rigid registration. CT lung density was maximal at end-expiration, and most deformation with breathing occurred in the lower thorax. Use of contrast increased mean lung density by 18 HU (range 16––20 HU; p == 0.004). Diagnostic scans had a lower mean lung density than planning scans (mean difference 57 HU in lung contralateral to tumor; p == 0.048). Post-treatment CT density measurements correlated strongly with clinician-scored radiological pneumonitis (r == 0.75; p < 0.001). Conclusions. Quantitative analysis of changes in lung density correlated strongly with physician-assigned radiologic pneumonitis scores. Deformable registration and CT density measurements permit objective assessment of treatment toxicity.
Document Type: Research Article
Affiliations: Department of Radiation Oncology, VU University Medical Center, Amsterdam, The Netherlands
Publication date: May 1, 2011