A technique to rapidly generate synthetic CT for MRI-guided online adaptive re-planning: an exploratory study.
Int J Radiat Oncol Biol Phys. 2018 Dec 11;:
Authors: Ahunbay EE, Thapa R, Chen X, Paulson E, Li XA
Abstract
PURPOSE/OBJECTIVE(S): To develop an automatic and accurate atlas based technique for synthetic CT (sCT) generation to be used for online adaptive replanning during MRI guided radiation therapy (RT).
MATERIALS/METHODS: The proposed method utilizes deformable image registration (DIR) of daily MRI and reference CT with additional corrections to maintain bone rigidity and also transfer of random air regions by thresholding. The DIR is performed with constraints on the bony structures using a special algorithm of ADMIRE (Elekta). The air regions are delineated from low-signal regions on the daily MRI and forced to air density. The bone regions in the MRI (already determined from the CT) are separated from the air regions since both bone and air have low signal density in MRI. All these steps are automated. The generated sCT is compared to reference CT and the alternative voxel-based CT (bCT) for four extra-cranial sites (head and neck, thorax, abdomen, pelvis) in terms of Mean Absolute Error (MAE), gamma analysis of 3D doses and DVH parameters.
RESULTS: Both MAE and dosimetric analysis results were favorable for the proposed sCT generation method. The average MAE for the sCT/bCT were 25.5/66.7, 25.9/65.3, 24.8/44.2 and 16.6/47.7 for head and neck, thorax, abdomen and pelvis while the gamma analysis (1.5%-2mm) yielded 98.7/97.1, 99.1/93.9, 99.5/99.4, 99.7/99.4respectively for those sites.
CONCLUSIONS: The proposed method generates equal or more accurate sCT than those from the bulk density assignment but without the need for multiple MR sequences. The method can be fully automated and applicable for online adaptive replanning.
PMID: 30550817 [PubMed - as supplied by publisher]
from PubMed via alexandrossfakianakis on Inoreader https://ift.tt/2CfPkaU
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