AbstractID: 9373 Title: Building a deformable model of the lung using thin plate splines
The advent of dynamic, or “4D”, radiotherapy modeling and treatment techniques
requires an infrastructure to weigh the relative merits of various interventions (breath
holding, gating, tracking). Creation of treatment planning models that account for motion
and deformation can allow the relative merits of such techniques to be evaluated. In
order to develop a treatment planning model of a moving and deforming organ such as
the lung, registration tools that account for deformation are required. We tested the
accuracy of an alignment tool using thin plate splines driven by the selection of control
points and iterative alignment. 11 patients each had 2 sequential CT scans (helical, 3 mm
aperture, pitch 2.0) at breath-held normal inhale and exhale states. The inhale CT scan
was aligned to the segmented (from drawn contours) exhale CT right lung intensity
distribution. 30 control points per patient were used. Alignment accuracy (σ of
difference in actual and predicted position) was determined from locations of vascular
and bronchial bifurcations, and found to be 2.7, 2.4, and 3.4 mm about the AP, LR, and
IS directions. Transformations applied to the lung surface show good agreement. This
technique shows promise for future development of dynamic models of the lung.
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