WE-C-116-07: Tumor Enhancement Using Deformable Image Registration for Four-Dimensional Magnetic Resonance Imaging (4D-MRI): A Feasibility Study.
PURPOSE: We have previously developed a 4D-MRI technique using the fast imaging sequence employing steady-state acquisition (FIESTA) sequence, which has suboptimal tumor-to-tissue contrast-to-noise ratio (CNR) due to its T2*/T1 weighting. This study investigated the feasibility of enhancing the tumor-to-tissue CNR using deformable image registration (DIR). METHODS: Five patients with cancers in the liver were included in an IRB-approved study. 4D-MRI images were acquired on a 1.5T GE scanner and reconstructed off line using in-house developed program. All patients were also imaged with a T2-w fast recovery fast spin-echo (FRFSE) sequence at the end-of-exhalation phase. Deformation vectors between respiratory phases of the 4D-MRI were determined using commercial software. Pseudo 'enhanced' 4D-MRI was then generated by applying the deformation vectors to the T2-w FRFSE MR images. Motion trajectories of tumor and diaphragm and tumor-to-tissue CNR were compared between the original T2*/T1-w 4D-MRI and the 'enhanced' T2-w 4D-MRI. To validate our method, we performed a simulation study based on a 4D digital human phantom. MR images with T2*/T1-w and T2-w with were generated by assigning organ intensities corresponding to those in FIESTA and FRFSE images, respectively. RESULTS: In the phantom study, motion trajectories of the hypothesized 'tumor' matched excellently between the original T2*/T1-w 4D-MRI and the 'enhanced' T2-w 4D-MRI. Mean(±SD) absolute difference in motion amplitude was 0.66 (±0.62) mm. In the patient study, tumor and diaphragm motion trajectories closely matched between the two 4D-MRIs: mean correlation coefficient was great than 0.97 in all directions; the mean (±SD) absolute difference in motion amplitude was smaller than 0.55(±0.19) mm. Tumor-to-tissue CNR was significantly improved from 7.57(±5.6) in the original 4D-MRI to 23.75(±15.8) in the 'enhanced' 4D-MRI. CONCLUSION: It is feasible to improve tumor-to-tissue CNR of T2*/T1-w 4D-MRI using the DIR method. The 'enhanced' 4D-MRI retained comparable tumor motion information as the original 4D-MRI. This work is partly supported by funding from NIH (1R21CA165384-01A1) and a research grant from the Golfers Against Cancer (GAC) Foundation.
Yang, J; Cai, J; Wang, H; Chang, Z; Czito, B; Bashir, M; Yin, F
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