Songan Mao, Presenter: Nothing to Disclose

Huanmei Wu PhD, Abstract Co-Author: PerkinElmer Inc Varain Inc

George Sandison, Abstract Co-Author: Nothing to Disclose

Shiaofen Fang, Abstract Co-Author: Nothing to Disclose

Due to patient free breathing, tumor and other critical organs deform during cancer radiation treatment. The voxel to voxel mapping among the 3DCT images at different time instances will be of great help in dose calculation and treatment verifi-cation. To address these challenges, an iterative morphing approach has been devel-oped to define the iso-surface feature points and to map the 3D volumes.

To map the tumor (similarly for other critical structures) from the source 3DCT to the target 3DCT, first, the tumor iso-surfaces of both the source and target phases are automatically detected based on neighboring CT intensity patterns. Then, the minimized bounding boxes of the tumor on both the source and target phases are derived based on tumor iso-surface. The feature points (landmarks) on the source iso-surface are selected based on gridding on the minimized bounding box and distances to the iso-surface. Next, for both the source and target phases, the nearest tumor iso-surface intensity and relative positions are projected to the six 2D planes of the bounding boxes. The corresponding landmarks are then mapped from the source to the target phase based on image template matching algorithm. Last, using a modified Shepard morphing approach, the entire tumor volume is mapped from the source phase to the target phase.

A prototype has been developed and preliminary experiments have been performed with the previously acquired 4DCT. The figure below illustrated one set of the experiments where phase 0 was selected as the source phase and phases 7, 8 and 9 as the target phases, respectively. On the source phase, 31 landmarks were obtained on the tumor and the landmarks mapping results are illustrated in Fig. 1. The mapping results were evaluated with the similarity of the image intensity histogram and the displacement of the tumor volume. For the experiment demonstrated, the average landmark intensity differences of the predicted and actual 3D volume were 1.09, 1.36, and 1.08 for the phase 7, 8, and 9, respectively, with the average stdev of 0.82.

We proposed a tumor iterative morphing method for 3D tumor iso-surface and volume mapping from one 3DCT to another with deformation. The dose effects from tumor deformation will be further investigated.

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Mao, S, Wu, H, Sandison, G, Fang, S, An Iterative Morphing Approach for Deformable Volumetric Mapping.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14018395.html