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Do tumors in the lung deform during normal respiration?

Philips CT Marketing Philips Healthcare

An image registration investigation

Wu J, Lei P, Shekhar R, Li H, Suntharalingam M, D'Souza WD.


Department of Radiation Oncology, University of Maryland, School of Medicine, Baltimore, MD, USA.


* Originally published in the September issue of the International Journal of Radiation Onology, Biology, Physics.



The purpose of this study was to investigate whether lung tumors may be described adequately using a rigid body assumption or whether they deform during normal respiration.


Methods and materials

Thirty patients with early stage non-small-cell lung cancer underwent four-dimensional (4D) computed tomography (CT) simulation. The gross tumor volume (GTV) was delineated on the 4D CT images. Image registration was performed in the vicinity of the GTV. The volume of interest for registration was the GTV and minimal volume of surrounding non-GTV tissue. Three types of registration were performed: translation only, translation + rotation, and deformable. The GTV contour from end-inhale was mapped to end-exhale using the registration-derived transformation field. The results were evaluated using three metrics: overlap index (OI), root-mean-squared distance (RMS), and Hausdorff distance (HD).



After translation only image registration, on average OI increased by 21.3%, RMS and HD reduced by 1.2 mm and 2.0 mm, respectively. The succeeding increases in OI after translation + rotation and deformable registration were 1.1% and 1.4% respectively. The succeeding reductions in RMS were 0.1 mm and 0.2 mm respectively. No reduction in HD was observed after translation + rotation and deformable image registration compared with translation only registration. The difference in the results from the three registration scenarios was independent of GTV size and motion amplitude.



The primary effect of normal respiration on lung tumors was the translation of tumors. Rotation and deformation of lung tumors was determined to be minimal.

For more information about this publication, check out the PubMed listing for this article.

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Oct 29, 2009

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4D, Body, chest, lung cancer, lungs, Oncology, Thorax, tumor

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