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Generating Pseudo-CT for MRI-Only RT Using T1-Weighted and T2-Weighted MRI Images

S Leu1*, Z Lin1 , Z Huang2 , (1) East Carolina University, Greenville, NC, (2) Saint Thomas Hospital, Brentwood, TN


(Tuesday, 7/16/2019) 10:00 AM - 10:30 AM

Room: Exhibit Hall | Forum 2

Purpose: Increasing interests in using magnetic resonance imaging (MRI) only in radiotherapy treatment require methods for predicting the computed tomography (CT) number and generating the pseudo-CT (pCT) image from MRI. This study aims to develop a voxel-based method to generate pseudo-CT images from two sets of MRI data for dose calculations in radiotherapy treatment plans.

Methods: Pelvic MRI (T1-Flash, T2-TSER) and CT scan data are collected from six patients with carcinoma of the cervix in a prospective study. The CT data and the two different sets of MRI data of multiple patients are segmented into several regions. A regression analysis is used to determine a two-variable polynomial function for each region to relate voxel’s two MRI intensity values to their average CT number. The method is validated by applying a leave-one-out-cross-validation (LOOCV), where the model is trained with data from five patients and then applied to the MRI data of the remaining patient to generate the pseudo-CT. We evaluate the accuracy via mean absolute error (MAE) to find the Hounsfield unit (HU) difference between the pCT and reference-CT (rCT) images.

Results: The mean absolute error across all patients is 40.3 ± 3.0 HU, ranging from 36.7 to 44.4 HU for individual LOOCV cycle.

Conclusion: The proposed voxel-based method generates pCT images with MAE results in close agreement with rCT images. Our MAE results are better than previous results from voxel-based methods or most atlas-based methods and comparable to another study using the more complicated atlas-based method.




IM/TH- MRI in Radiation Therapy: MRI for treatment planning

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