PixelPrint 4D : A 3D Printing Method of Fabricating Patient-Specific Deformable CT Phantoms for Respiratory Motion Applications.

Summary

The authors introduce PixelPrint 4D, a voxel-by-voxel 3D printing workflow using flexible materials to fabricate patient-specific deformable lung phantoms from 4DCT. The phantom closely matched patient anatomy and nonrigid deformation: SSIM was 0.93; mean tumor motion errors were ≤0.7±0.6 mm per axis; and attenuation–volume change relationships were statistically indistinguishable from the patient (ANCOVA P=0.83).

Key Findings

• High structural fidelity: SSIM between phantom and patient lungs was 0.93.
• Realistic motion: mean tumor motion errors ≤0.7±0.6 mm in each orthogonal direction.
• Physiologic attenuation–volume coupling preserved: ANCOVA P=0.83 indicating no significant difference vs patient.
• Voxel-wise density control via PixelPrint produced realistic textures and attenuation profiles under compression.

Clinical Implications

While preclinical, the technology can standardize benchmarking of motion-reduction, 4D dose calculation, and tracking algorithms, accelerating translation of safer, more accurate respiratory imaging and radiotherapy.

Limitations

• Derived from a single patient 4DCT case; generalizability to diverse anatomies/motions requires expansion.
• Compression-based pseudo-4D generation may not capture all in vivo mechanics (e.g., hysteresis, airflow effects).

Future Directions

Scale to multi-patient libraries and left/right lungs, integrate airflow mechanics, and establish multi-center benchmarking datasets for evaluating CT motion-compensation and AI reconstruction/tracking.