TH-CD-207-09: Retrospective 4D-MRI with a Novel Image-Based Surrogate: A Sagittal-Coronal-Diaphragm Point of Intersection (SCD-PoI) Motion Tracking Method




The unreliable stability of internal respiratory surrogates and inconvenience of external respiratory surrogates for current retrospective 4D-MRI techniques largely affects the image quality of 4D-MRI. This study aims at developing image-based surrogate, a sagittal-coronal-diaphragm point of intersection (SCD-PoI) motion tracking method for retrospective 4D-MRI reconstruction.Methods/materials: As a pre-estimate of respiratory motion pattern, single-slice sagittal cines (FIESTA) were acquired at a location near the dome of the diaphragm. Subsequently, multi-slice coronal cines (FIESTA) were acquired and used for 4D-MRI reconstruction with phase sorting. Diaphragm motion trajectories were measured from the point of intersection between sagittal MRI cine plane, coronal MRI cine plain and the diaphragm dome surface. This point is defined as sagittal-coronal-diaphragm point of intersection (SCD-PoI). We pre-estimate respiraotyr motion by tracking SCD-PoI on sagitall cine. Then coronal images were then re-binned to different phased bins according to SCD-PoI motion tracking on coronal cine. This 4D-MRI technique was evaluated on a 4D Digital Extended Cardiac-Torso (XCAT) human phantom with a hypothesized moving tumor, six healthy voluneteers and two cancer patients under an IRB-approved study. Region of interest (ROI: tumor for XCAT and patients, dome of left kidney for healthy volunteers) trajectories on 4D-MRI were measured and compared with the reference (input respiratory curve for XCAT and ROI trajectories extracted from reference single-slice MRI cine (FIESTA) for human subjects). Superior-inferior (SI) mean absolute amplitude difference (D) and cross-correlation coefficient (CC) were calculated.


4D-MRI on XCAT demonstrated highly accurate motion information with a low D (1.13mm) and a high CC (0.98) in the SI direction. Minimal artifacts were observed in human participants’ 4D-MRI, and images were adequate to reveal the respiratory motion of organs and tumor (D=1.08±1.03mm; CC=0.96).


A novel 4D-MRI technique with image-based respiratory surrogate has been developed and tested on a digital phantom and human subjects.