Purpose: We have previously developed a novel 4D‐MRI technique using body area (BA) as internal respiratory surrogate. This study is to demonstrate our initial patient results via validating the accuracy of tumor motion measurements and the improvement of tumor‐to‐tissue contrast‐to‐signal ratio (CNR) in the 4D‐MRI. Methods: Five patients with cancer (s) in the liver were enrolled in an IRB‐approved study. All patients underwent 3D/4D CT and MR simulation for treatment planning. 4D‐MRI image were generated by firstly acquiring multiple‐slice multiple‐phase cine‐MR images in the axial plane and then retrospectively binning the images based on respiratory phases. Respiratory signals were determined by tracking changes of the BA of axial MR images. Single‐slice 2D cine MR images were also acquired across the center of the tumor in orthogonal planes (axial, sagittal, and coronal). For data analysis, tumor motion trajectories in the superior‐inferior (SI), anterior‐posterior (AP), and medial‐lateral (ML) directions, were determined from 4D‐MRI and compared to those determined from cine‐MR images, which were used as references. The correlation coefficients (CC) and the differences in tumor motion amplitude were determined between the two. Tumor‐to‐liver CNR was compared between 4D‐MRI and 4D‐CT. Results: 4D‐MRI clearly revealed respiratory motion in all patients. Tumor motion trajectories were comparable between 4D‐MRI and cine‐MR: the mean (± standard deviation (SD)) CC was 0.97(±0.03), 0.97(±0.02), and 0.99(±0.04) in the SI, AP and ML directions, respectively. The mean (±SD) difference in tumor motion amplitude was 0.61(±0.17)mm, 0.32(±0.17)mm, 0.14(±0.06)mm in the SI, AP and ML directions, respectively. The mean tumor‐to‐tissue CNR were improved from 1.52(±2.04) in 4D‐CT images to 7.57(±5.64) in 4D‐MRIs. Conclusion: 4D‐MRI using BA as respiratory surrogate and axial image acquisition has been successfully demonstrated in patients. It is a promising technique for more accurately imaging tumor respiratory motion with improved soft‐tissue contrast. This work is partly supported by funding from NIH (1R21CA165384‐01A1) and a research grant from the Golfers Against Cancer (GAC) Foundation.
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging