Dynamic Cone-Beam Ct Reconstruction Using Spatial and Temporal Implicit Neural Representation Learning (STINR)

Authors

You Zhang
Hua-Chieh Shao
Tinsu Pan
Tielige Mengke

Publication Date

2-6-2023

Journal

Physics in Medicine & Biology

Abstract

Objective. Dynamic cone-beam CT (CBCT) imaging is highly desired in image-guided radiation therapy to provide volumetric images with high spatial and temporal resolutions to enable applications including tumor motion tracking/prediction and intra-delivery dose calculation/accumulation. However, dynamic CBCT reconstruction is a substantially challenging spatiotemporal inverse problem, due to the extremely limited projection sample available for each CBCT reconstruction (one projection for one CBCT volume).

Approach. We developed a simultaneous spatial and temporal implicit neural representation (STINR) method for dynamic CBCT reconstruction. STINR mapped the unknown image and the evolution of its motion into spatial and temporal multi-layer perceptrons (MLPs), and iteratively optimized the neuron weightings of the MLPs via acquired projections to represent the dynamic CBCT series. In addition to the MLPs, we also introduced prior knowledge, in the form of principal component analysis (PCA)-based patient-specific motion models, to reduce the complexity of the temporal mapping to address the ill-conditioned dynamic CBCT reconstruction problem. We used the extended-cardiac-torso (XCAT) phantom and a patient 4D-CBCT dataset to simulate different lung motion scenarios to evaluate STINR. The scenarios contain motion variations including motion baseline shifts, motion amplitude/frequency variations, and motion non-periodicity. The XCAT scenarios also contain inter-scan anatomical variations including tumor shrinkage and tumor position change.

Main results. STINR shows consistently higher image reconstruction and motion tracking accuracy than a traditional PCA-based method and a polynomial-fitting-based neural representation method. STINR tracks the lung target to an average center-of-mass error of 1-2 mm, with corresponding relative errors of reconstructed dynamic CBCTs around 10%.

Significance. STINR offers a general framework allowing accurate dynamic CBCT reconstruction for image-guided radiotherapy. It is a one-shot learning method that does not rely on pre-training and is not susceptible to generalizability issues. It also allows natural super-resolution. It can be readily applied to other imaging modalities as well.

Keywords

Humans, Motion, Lung, Lung Neoplasms, Phantoms, Imaging, Cone-Beam Computed Tomography, Algorithms, Image Processing, Computer-Assisted, Four-Dimensional Computed Tomography, image reconstruction, dynamic imaging, cone-beam CT, implicit neural representation, principal component analysis, motion modeling

DOI

10.1088/1361-6560/acb30d

PMID

36638543

PMCID

PMC10087494

PubMedCentral® Posted Date

2-6-2023

PubMedCentral® Full Text Version

Post-print

Published Open-Access

yes