Basic Study of the Imaging Conditions on Tumor Volume Measurement Using 3D-MR Imaging of the Liver While Patient Holds Breath

Abstract

Tumor volumetric measurement using liver 3D-MR imaging tends to cause measurement errors because the liver moves with the diaphragm during imaging while the patient is holding the breath. The breath holding method of the patient when 3D-MR imaging for measurement of tumor volume was performed was discussed using a movable simulated tumor phantom. Furthermore, optimal imaging conditions (breath holding method, slice section, voxel setting and phase encoding direction) with the least influence by body motion were studied. Based on three breath holding methods, the simulated phantom was moved in the direction of the foot-head along the line of the MRI receiver coil. The image sequence was a 3D-T1 weighted fast field echo method. The imaging time was fixed at 20 s. As a result, the breath holding method with the smallest measured volume error is functional residual capacity (FRC) breath hold (0.1 mm/s). The optimum imaging condition is when the imaging section is set in the axial direction and the phase encoding direction is perpendicular to the moving direction with an iso voxel as small as possible. In the case where it is necessary to set the phase encoding in the direction parallel to the proceeding direction, imaging with the setting of rectangular voxel can suppress the measurement error of the volume. In order to measure accurate volume using liver 3D-MR imaging, it is necessary to know the direction of movement of the tumor during respiration and to set appropriate breath holding method, section, phase encoding direction and voxel size.