M4DTrack: A DICOM-Based Imaging Informatics Workflow for User-Supervised 4DCT Lung Tumor Motion Reporting

Four-dimensional computed tomography (4DCT) is routinely used in radiotherapy simulation to evaluate respiration-induced tumor motion, but the motion information is often reviewed visually rather than captured as structured, phase-resolved data. We developed and evaluated M4DTrack, a DICOM-based imaging-informatics workflow for user-supervised 4DCT lung tumor motion analysis and structured, exportable three-dimensional center-of-mass (CoM) motion reporting. M4DTrack imports phase-resolved DICOM CT images, groups images by respiratory phase, displays linked axial/coronal/sagittal views, supports crosshair-based tumor localization and HU inspection, and applies seed or linked 3D-box initialization with sequential phase-to-phase HU-volume propagation. An 8-case lower-lobe lung 4DCT dataset (80 respiratory phases) was analyzed. Directional amplitudes, 3D vector amplitude, maximum phase-wise displacement, and agreement with independent ITV-GTV reference amplitudes were quantified. HU-weighted CoM amplitudes were 2.44 ± 1.44 mm, 2.64 ± 1.37 mm, and 6.04 ± 2.48 mm in X, Y, and Z patient-coordinate directions, respectively. Mean 3D vector amplitude was 7.26 ± 2.50 mm, and mean maximum phase-wise 3D displacement was 6.20 ± 2.10 mm. Biases versus ITV-GTV reference amplitudes were 0.01, - 0.84, and 0.23 mm for X, Y, and Z, respectively, with a 3D vector amplitude bias of - 0.29 mm. M4DTrack provides a user-supervised imaging-informatics bridge between qualitative 4DCT cine review and structured quantitative motion documentation. The pilot results support feasibility for generating exportable, phase-resolved tumor-motion metrics while preserving user-supervised review of 4DCT artifacts, HU-capture uncertainty, adjacent anatomy, and differences between CoM-based and extent-based measurements.