Internal target volume estimation for liver cancer radiation therapy using an ultra quality 4-dimensional magnetic resonance imaging

Abstract

Purpose: Accurate internal target volume (ITV) estimation is essential for effective and safe radiation therapy in liver cancer. This study evaluates the clinical value of an ultraquality 4-dimensional magnetic resonance imaging (UQ 4D-MRI) technique for ITV estimation. Methods and Materials: The UQ 4D-MRI technique maps motion information from a low spatial resolution dynamic volumetric MRI onto a high-resolution 3-dimensional MRI used for radiation treatment planning. It was validated using a motion phantom and data from 13 patients with liver cancer. ITV generated from UQ 4D-MRI (ITV4D) was compared with those obtained through isotropic expansions (ITV2 mm and ITV5 mm) and those measured using conventional 4D-computed tomography (computed tomography-based ITV, ITVCT) for each patient. Results: Phantom studies showed a displacement measurement difference of <5% between UQ 4D-MRI and single-slice 2-dimensional cine MRI. In patient studies, the maximum superior-inferior displacements of the tumor on UQ 4D-MRI showed no significant difference compared with single-slice 2-dimensional cine imaging (P = .985). Computed tomography-based ITV showed no significant difference (P = .72) with ITV4D, whereas ITV2 mm and ITV5 mm significantly overestimated the volume by 29.0% (P = .002) and 120.7% (P < .001) compared with ITV4D, respectively. Conclusions: UQ 4D-MRI enables accurate motion assessment for liver tumors, facilitating precise ITV delineation for radiation treatment planning. Despite uncertainties from artificial intelligence-based delineation and variations in patients’ respiratory patterns, UQ 4D-MRI excels at capturing tumor motion trajectories, potentially improving treatment planning accuracy and reducing margins in liver cancer radiation therapy.