Deformable image registration (DIR) is critical for accurate clinical diagnosis and effective treatment planning. However, patient movement, significant intensity differences, and large breathing deformations hinder accurate anatomical alignment in multi-modal image registration. These factors exacerbate the entanglement of anatomical and modality-specific style information, thereby severely limiting the performance of multi-modal registration. To address this, we propose a novel LAtent Diffusion-based Domain-Adaptive feature disentangling (LADDA) framework for unsupervised multi-modal medical image registration, which explicitly addresses the representation disentanglement. First, LADDA extracts reliable anatomical priors from the Latent Diffusion Model (LDM), facilitating downstream content-style disentangled learning. A Domain-Adaptive Feature Disentangling (DAFD) module is proposed to promote anatomical structure alignment further. This module disentangles image features into content and style information, boosting the network to focus on cross-modal content information. Next, a Neighborhood-Preserving Hashing (NPH) is constructed to further perceive and integrate hierarchical content information through local neighbourhood encoding, thereby maintaining cross-modal structural consistency. Furthermore, a Unilateral-Query-Frozen Attention (UQFA) module is proposed to enhance the coupling between upstream prior and downstream content information. The feature interaction within intra-domain consistent structures improves the fine recovery of detailed textures. The proposed framework is extensively evaluated on large-scale multi-center datasets, demonstrating superior performance across diverse clinical scenarios and strong generalization on out-of-distribution (OOD) data.

Cone-beam Computed Tomography (CBCT) provides real-time three-dimensional (3D) imaging support for intraoperative navigation. However, high-attenuation metal implants introduce severe metal artifacts in reconstructed CBCT images. These artifacts compromise image quality and therefore may affect diagnostic accuracy. Current CBCT metal artifact reduction (MAR) algorithms overlook the complementary information available across CBCT views, leading to inaccurate projection-domain interpolation and secondary artifacts in the reconstructed images. To tackle these challenges, we propose a novel Unsupervised Projection-domain Multiview Constraint Learning Network (UPMCL-Net), which directly learns from metal-affected data for CBCT MAR without ground truths. In addition, a transformer-based MultiView Consistency Module (MVCM) is constructed to interpolate the projection-domain metal region for cross-view consistency. Finally, a Hybrid Feature Attention Module (HFAM) is designed to adaptively fuse interview and intraview features. Comprehensive experiments conducted on real clinical datasets confirm the performance of UPMCL-Net, showcasing its potential as an efficient, accurate, and reliable approach for CBCT MAR in clinical intraoperative interventions.

Dual-energy CT exploits the different attenuation characteristics of substances under different energy X-rays and collects high- and low-energy data from the same area to differentiate and quantify specific substances, which is now widely used in clinical diagnosis, disease monitoring, and other fields. If the object scanned during dual-energy CT imaging contains metallic material, the reconstructed image will suffer from metal artifacts. Metal artifacts in dual-energy CT result in surrounding tissue structures presenting erroneous CT values, blurred image details, and unclear border demarcation lines, which seriously affects the quality of the images as well as the accuracy of clinical diagnosis. To reduce metal artifacts in dual-energy CT, we combine material decomposition techniques with metal artifact reduction to explore metal artifact reduction methods applied to dual-energy CT.

Cone-beam CT is extensively used in medical diagnosis and treatment. Despite its large longitudinal field of view (FoV), the horizontal FoV of CBCT systems is severely limited due to the detector width. Certain commercial CBCT systems increase the horizontal FoV by employing the offset detector method. However, this method necessitates 360° full circular scanning trajectory which increases the scanning time and is not compatible with specific CBCT system models. In this paper, we investigate the feasibility of large FoV imaging under short scan trajectories with an additional X-ray source. A dual-source CBCT geometry is proposed as well as two corresponding image reconstruction algorithms. The first one is based on cone-parallel rebinning and the subsequent employs a modified Parker weighting scheme. Theoretical calculations demonstrate that the proposed geometry achieves a wider horizontal FoV than the ${90}\%$ detector offset geometry (radius of ${214}.{83}\textit {mm}$ vs. ${198}.{99}\textit {mm}$ ) with a significantly reduced rotation angle (less than 230° vs. 360°). As demonstrated by experiments, the proposed geometry and reconstruction algorithms obtain comparable imaging qualities within the FoV to conventional CBCT imaging techniques. Implementing the proposed geometry is straightforward and does not substantially increase development expenses. It possesses the capacity to expand CBCT applications even further.

In Computed Tomography (CT) imaging, the ring artifacts caused by the inconsistent detector response can significantly degrade the reconstructed images, having negative impacts on the subsequent applications. The new generation of CT systems based on photon-counting detectors are affected by ring artifacts more severely. The flexibility and variety of detector responses make it difficult to build a well-defined model to characterize the ring artifacts. In this context, this study proposes the global dependency-enhanced dual-domain parallel neural network for Ring Artifact Removal (RAR). First, based on the fact that the features of ring artifacts are different in Cartesian and Polar coordinates, the parallel architecture is adopted to construct the deep neural network so that it can extract and exploit the latent features from different domains to improve the performance of ring artifact removal. Besides, the ring artifacts are globally relevant whether in Cartesian or Polar coordinate systems, but convolutional neural networks show inherent shortcomings in modeling long-range dependency. To tackle this problem, this study introduces the novel Mamba mechanism to achieve a global receptive field without incurring high computational complexity. It enables effective capture of the long-range dependency, thereby enhancing the model performance in image restoration and artifact reduction. The experiments on the simulated data validate the effectiveness of the dual-domain parallel neural network and the Mamba mechanism, and the results on two unseen real datasets demonstrate the promising performance of the proposed RAR algorithm in eliminating ring artifacts and recovering image details.

Four-dimensional Cone-beam CT (4D-CBCT) has already been integrated into many commercial radiotherapy systems to facilitate image-guided radiotherapy (IGRT). These techniques reconstruct a sequence of three-dimensional (3D) CBCT volumes based on respiratory phases, providing motion-compensated images. Nevertheless, current 4D-CBCT methods still suffer from poor imaging quality due to the limited number of views used for phase-resolved reconstruction, and deep learning-based methods require high-quality training data, which is commonly unavailable. In this paper, we propose a self-supervised 4D-CBCT imaging method based on dynamic neural attenuation fields (D-NAF). The dynamic pulmonary CBCT images are encoded into a 4D implicit representation incorporating both spatial information and temporal information. Moreover, we employed a separable spatial-temporal encoding method to reduce the dimensionality of the solution space, leading to enhanced convergence and reconstruction quality. The results demonstrate that the proposed method yields superior imaging quality in comparison to alternative approaches, with an RMSE value of 59.82 HU, PSNR of 35.33 dB and SSIM of 0.9358. This method is expected to be a new benchmark for self-supervised 4D-CBCT imaging.

Spectral CT can provide material characterization ability to offer more precise material information for diagnosis purposes. However, the material decomposition process generally leads to amplification of noise which significantly limits the utility of the material basis images. To mitigate such problem, an image domain noise suppression method was proposed in this work. The method performs basis transformation of the material basis images based on a singular value decomposition. The noise variances of the original spectral CT images were incorporated in the matrix to be decomposed to ensure that the transformed basis images are statistically uncorrelated. Due to the difference in noise amplitudes in the transformed basis images, a selective filtering method was proposed with the low-noise transformed basis image as guidance. The method was evaluated using both numerical simulation and real clinical dual-energy CT data. Results demonstrated that compared with existing methods, the proposed method performs better in preserving the spatial resolution and the soft tissue contrast while suppressing the image noise. The proposed method is also computationally efficient and can realize real-time noise suppression for clinical spectral CT images.

Intraoperative Cone-Beam Computed Tomography (CBCT) provides fast multiplanar cross-sectional imaging and three-dimensional reconstructions in clinical scene. However, high-attenuation metallic implants result in the obstruction of low-energy X-rays and further lead to metal artifacts in the reconstructed CT images. Existing metal artifact reduction approaches do not consider automated fine-grained metallic implants segmentation. Imprecise metallic implants segmentation severely limits the clinical practical applicability of MAR approaches. To address the above challenge, in this study, we present a novel DUAL-domain multi-view Weak supervIsed SEgmentation network for Metal Artifact Reduction (DUALWISE-MAR) to coarse-to-fine segment metallic implants without segmentation ground-truth. First, an Iterative Segmentation Refinement Mechanism is constructed to progressively enhance initial coarse label and guide segmentation network close to the ideal metal mask. Second, a Multi-view Consistent Segmentation Network is constructed for data-consistent segmentation to capture the metal shape relationship between adjacent views in projection-domain. Third, a Segmentation Recalibration Module is proposed to calibrate the inaccurate prediction regions in the imagedomain. Extensive experiments have been conducted on the real clinical CBCT dataset and demonstrate that the proposed DUALWISE-MAR framework achieves excellent performance in metal segmentation compared to the state-of-the-art methods.