Program Information
Evaluation of the Accuracy of Deformable Image Registration Between KVCT and MVCT Combined with a Histogram Matching Algorithm
M Saito*, Y Shibata , N Sano , H Onishi , University of Yamanashi, Chuo-city, Yamanashi
Presentations
WE-RAM3-GePD-I-5 (Wednesday, August 2, 2017) 10:30 AM - 11:00 AM Room: Imaging ePoster Lounge
Purpose: To evaluate the accuracy of deformable image registration (DIR) using histogram matching algorithm between planning kVCT (pCT) and Tomotherapy pre-treatment MVCT.
Methods: Seven MVCT series acquired in every week were investigated for five prostate patients (76 Gy/38Fr) treated with Tomotherapy. First, histogram-matched MVCT (HM-MVCT) was created by matching the cumulative CT value of an original MVCT to the corresponding pCT. For evaluation of the accuracy of the DIR, dice similarity coefficient (DSC) between virtual pCT, which was generated by deformation the original pCT to the HM-MVCT, and the original MVCT was calculated for CTV, rectum, and bladder, respectively. Then, the dose calculation on the virtual pCT was performed by the same parameter as the planning condition and compared with the dose on the original pCT. All results of HM-method were compared with those of a non-HM method by Wilcoxon test.
Results: The average DSC between the virtual pCT (non-HM method) and the original MVCT was 0.75±0.01, 0.83±0.06, 0.90±0.04, for CTV, rectum, and bladder, respectively. For rectum and bladder, the DSC was improved by using HM method (the DSC was 0.81±0.06 (p=0.001), 0.81±0.04 (0.301), 0.92±0.06 (p=0.002) for CTV, rectum, and bladder, respectively). For the dose calculation, some difference was observed for three methods, especially for small calculation region such as rectum V60 (11.3±5.4 Gy , 7.1±4.5 Gy and 11.1±5.0 for the original pCT, the virtual pCT (non-HM method) and the virtual pCT (HM method), respectively), while there was little difference among these methods for the CTV dose index.
Conclusion: For MVCT, histogram-matching method would improve the accuracy of DIR. Furthermore, dose calculation using the histogram matched image would become an effective tool for adaptive radiotherapy.
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