Pulse-echo ultrasound attenuation tomography
We present the first fully two-dimensional attenuation imaging technique developed for pulse-echo ultrasound systems. Unlike state-of-the-art techniques, which use line-by-line acquisitions, our method uses steered emissions to constrain attenuation values at each location with multiple crossing wave paths, essential to resolve the spatial variations of this tissue property.Approach.At every location, we compute normalized cross-correlations between the beamformed images that are obtained from emissions at different steering angles. We demonstrate that their log-amplitudes provide the changes between attenuation-induced am...
Source: Physics in Medicine and Biology - April 22, 2024 Category: Physics Authors: Naiara Korta Martiartu Parisa Salemi Yolgunlu Martin Frenz Michael Jaeger Source Type: research
X-ray source motion blur modeling and deblurring with generative diffusion for digital breast tomosynthesis
Phys Med Biol. 2024 Apr 19. doi: 10.1088/1361-6560/ad40f8. Online ahead of print.ABSTRACTOBJECTIVE: Digital breast tomosynthesis (DBT) has significantly improved the diagnosis of breast cancer due to its high sensitivity and specificity in detecting breast lesions compared to two-dimensional mammography. However, one of the primary challenges in DBT is the image blur resulting from x-ray source motion, particularly in DBT systems with a source in continuous-motion mode. This motion-induced blur can degrade the spatial resolution of DBT images, potentially affecting the visibility of subtle lesions such as microcalcificatio...
Source: Physics in Medicine and Biology - April 19, 2024 Category: Physics Authors: Mingjie Gao Jeffrey A Fessler Heang-Ping Chan Source Type: research
Ultra-fast < em > in-vivo < /em > directional dark-field x-ray imaging for visualising magnetic control of particles for airway gene delivery
In this study, ultrafast directional dark-field synchrotron X-ray imaging was utlilised to understand how magnetic nanoparticles move within a live, anaesthetised, rat airway under the influence of static and moving
magnetic fields.
Main results: Magnetic nanoparticles emerging from an indwelling tracheal cannula were detectable during delivery, with dark-field imaging increasing the signal-to-noise ratio of this event by 3.5 times compared to the X-ray transmission signal. Particle movement as well as particle retention was evident. Dynamic magnetic fields could manipulate the magnetic particles in-situ.&a...
Source: Physics in Medicine and Biology - April 19, 2024 Category: Physics Authors: Ronan Smith Kaye S Morgan Alexandra McCarron Patricia Cmielewski Nichole Reyne David Parsons Martin Donnelley Source Type: research
Pixel-by-pixel correction of beam hardening artifacts by bowtie filter in fan-beam CT
Phys Med Biol. 2024 Apr 19. doi: 10.1088/1361-6560/ad40fa. Online ahead of print.ABSTRACTBeam hardening (BH) artifacts in computed tomography (CT) images originate from the polychromatic nature of X-ray photons. In a CT system with a bowtie filter, residual BH artifacts remain when polynomial fits are used. These artifacts lead to worse visuals, reduced contrast, and inaccurate CT numbers. This work proposes a pixel-by-pixel correction (PPC) method to reduce the residual BH artifacts caused by a bowtie filter.
Approach: The energy spectrum for each pixel at the detector after the photons pass through the bowtie fil...
Source: Physics in Medicine and Biology - April 19, 2024 Category: Physics Authors: Ping Ye Wei Zhao Taisei Shimomura Kaiwen Li Akihiro Haga Lisheng Geng Source Type: research
The effect of electron backscatter and charge build up in media on beam current transformer signal for ultra-high dose rate (FLASH) electron beam monitoring
Phys Med Biol. 2024 Apr 19. doi: 10.1088/1361-6560/ad40f7. Online ahead of print.ABSTRACTBeam current transformers (BCT) are promising detectors for real-time beam monitoring in ultra-high dose rate (UHDR) electron radiotherapy. However, previous studies have reported a significant sensitivity of the BCT signal to changes in source-to-surface distance (SSD), field size, and phantom material which have until now been attributed to the fluctuating levels of electrons backscattered within the BCT. The purpose of this study is to evaluate this hypothesis, with the goal of understanding and mitigating the variations in BCT sign...
Source: Physics in Medicine and Biology - April 19, 2024 Category: Physics Authors: Charles Pageot Karim Zerouali Dominique Guillet Bryan Richard Muir James Renaud Arthur Lalonde Source Type: research
Fast kV-switching and dual-layer flat-panel detector enabled cone-beam CT joint spectral imaging
Conclusions: A feasibility study of the joint spectral imaging for CBCT by utilizing both the FKS and DL-FPD was conducted, with the first tabletop CBCT system having such a capability being developed, which exhibits improved spectral imaging performance as expected.PMID:38640917 | DOI:10.1088/1361-6560/ad40f3 (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 19, 2024 Category: Physics Authors: Hao Zhou Li Zhang Zhilei Wang Hewei Gao Source Type: research
Experimental comparison of cylindrical and plane parallel ionization chambers for reference dosimetry in continuous and pulsed scanned proton beams
Phys Med Biol. 2024 Apr 19. doi: 10.1088/1361-6560/ad40f9. Online ahead of print.ABSTRACTObjective 
In this experimental work we compared the determination of absorbed dose to water using four ionization chambers (ICs), a PTW-34045 Advanced Markus, a PTW-34001 Roos, an IBA-PPC05 and a PTW-30012 Farmer, irradiated under the same conditions in one continuous- and in two pulsed-scanned proton beams. 
Approach
The ICs were positioned at 2 cm depth in a water phantom in four square-field single-energy scanned-proton beams with nominal energies between 80 MeV and 220 MeV and in the middle of 10x10x10 cm3 ...
Source: Physics in Medicine and Biology - April 19, 2024 Category: Physics Authors: Gloria Vilches-Freixas Geert Bosmans Alexandros Douralis Jonathan Martens Arturs Meijers Ilaria Rinaldi Koen Salvo Russell A S Thomas Hugo Palmans Ana Louren ço Source Type: research
ReconU-Net: a direct PET image reconstruction using U-Net architecture with back projection-induced skip connection
This study aims to introduce a novel back projection-induced U-Net-shaped architecture, called ReconU-Net, based on the original U-Net architecture for deep learning-based direct positron emission tomography (PET) image reconstruction. Additionally, our objective is to visualize the behavior of direct PET image reconstruction by comparing the proposed ReconU-Net architecture with the original U-Net architecture and existing DeepPET encoder-decoder architecture without skip connections.
[Approach] The proposed ReconU-Net architecture uniquely integrates the physical model of the back projection operation into the sk...
Source: Physics in Medicine and Biology - April 19, 2024 Category: Physics Authors: Fumio Hashimoto Kibo Ote Source Type: research
The gamma-variate in contrast-enhanced imaging: a unified view and method from computed to electrical impedance tomography
This study aims to develop a common theoretical and practical hemodynamic extraction basis for DCE modelling across modalities, based on the gamma-variate function.

Approach: The study introduces a framework to generate time-intensity curves for multiple DCE imaging modalities from user-defined hemodynamic parameters. Thus, extensive datasets were simulated for both DCE-CT and EIT, representing different hemodynamic scenarios. Additionally, gamma-variate extensions to account for several physiological effects were detailed in a modality-agnostic manner, and three corresponding fitting strategies, namely no...
Source: Physics in Medicine and Biology - April 19, 2024 Category: Physics Authors: Diogo Filipe Silva Steffen Leonhardt Source Type: research
Suppressing label noise in medical image classification using mixup attention and self-supervised learning
Phys Med Biol. 2024 Apr 18. doi: 10.1088/1361-6560/ad4083. Online ahead of print.ABSTRACTDeep neural networks (DNNs) have been widely applied in medical image classification and achieve remarkable classification performance. These achievements heavily depend on large-scale accurately annotated training data. However, label noise is inevitably introduced in the medical image annotation, as the labeling process heavily relies on the expertise and experience of annotators. Meanwhile, DNNs suffer from overfitting noisy labels, degrading the performance of models. Therefore, in this work, we innovatively devise noise-robust tra...
Source: Physics in Medicine and Biology - April 18, 2024 Category: Physics Authors: Mengdi Gao Hongyang Jiang Yan Hu Qiushi Ren Zhaoheng Xie Jiang Liu Source Type: research
ERSegDiff: a diffusion-based model for edge reshaping in medical image segmentation
Phys Med Biol. 2024 Apr 18. doi: 10.1088/1361-6560/ad4080. Online ahead of print.ABSTRACTMedical image segmentation is a crucial field of computer vision. Obtaining correct pathological areas can help clinicians analyze patient conditions more precisely. We have observed that both CNN-based and attention-based neural networks often produce rough segmentation results around the edges of the regions of interest. This significantly impacts the accuracy of obtaining the pathological areas. Without altering the original data and model architecture, further refining the initial segmentation outcomes can effectively address this ...
Source: Physics in Medicine and Biology - April 18, 2024 Category: Physics Authors: BaiJing Chen Junxia Wang Yuanjie Zheng Source Type: research
Adaptive cascaded transformer U-Net for MRI brain tumor segmentation
Phys Med Biol. 2024 Apr 18. doi: 10.1088/1361-6560/ad4081. Online ahead of print.ABSTRACTOBJECTIVE: Brain tumor segmentation on magnetic resonance imaging (MRI) plays an important role in assisting the diagnosis and treatment of cancer patients. Recently, cascaded U-Net models have achieved excellent performance via conducting coarse-to-fine segmentation of MRI brain tumors. However, they still suffer from obvious global and local differences among various brain tumors, which are difficult to solve with conventional convolutions.APPROACH: To address the issue, this work proposes a novel Adaptive Cascaded Transformer U-Net ...
Source: Physics in Medicine and Biology - April 18, 2024 Category: Physics Authors: Bonian Chen Qiule Sun Yutong Han Bin Liu Jianxin Zhang Qiang Zhang Source Type: research
Biological dose optimization incorporating intra-tumoural cellular radiosensitivity heterogeneity in ion-beam therapy treatment planning
Phys Med Biol. 2024 Apr 18. doi: 10.1088/1361-6560/ad4085. Online ahead of print.ABSTRACT
Treatment plans of charged-particle therapy have been made under an assumption that all cancer cells within a tumour equally respond to a given radiation. However, an intra-tumoural cellular radiosensitivity heterogeneity clearly exists, and it may lead to an overestimation of therapeutic effects of the radiation. The purpose of this study was to develop a biological model that can incorporate the radiosensitivity heterogeneity into biological optimization for charged-particle therapy treatment planning.
Approach. The ...
Source: Physics in Medicine and Biology - April 18, 2024 Category: Physics Authors: Taku Inaniwa Nobuyuki Kanematsu Masashi Koto Source Type: research
Group sparse-based Taylor expansion method for liver pharmacokinetic parameters imaging of dynamic fluorescence molecular tomography
In this study, group sparse-based Taylor expansion (GSTE) method is proposed to address these problems.APPROACH: Firstly, Taylor expansion framework is introduced to reduce time and computational cost. Secondly, group sparsity based on structural prior is introduced to improve reconstruction accuracy. Thirdly, alternating iterative solution based on accelerated gradient descent (AGD) algorithm is introduced to solve the problem.MAIN RESULTS: Numerical simulation and in vivo experimental results demonstrate that, in comparison to existing methods, the proposed approach significantly enhances reconstruction speed without a d...
Source: Physics in Medicine and Biology - April 18, 2024 Category: Physics Authors: Yansong Wu Xuelei He Zihao Chen Xiao Wei Yanqiu Liu Shuangchen Li Heng Zhang Jingjing Yu Huangjian Yi Hongbo Guo Xiaowei He Source Type: research
Anatomy-guided multi-resolution image reconstruction in PET
Phys Med Biol. 2024 Apr 18. doi: 10.1088/1361-6560/ad4082. Online ahead of print.ABSTRACTIn this paper, we propose positron emission tomography (PET) image reconstruction using a multi-resolution triangular mesh. The mesh can be adapted based on patient specific anatomical information that can be in the form of a computed tomography (CT) or magnetic resonance imaging (MRI) image in the hybrid imaging systems. The triangular mesh can be adapted to high resolution in localized anatomical regions of interest (ROI) and made coarser in other regions, leading to an imaging model with high resolution in the ROI with clearly reduc...
Source: Physics in Medicine and Biology - April 18, 2024 Category: Physics Authors: Piia Lesonen Ville-Veikko Wettenhovi Ville Kolehmainen Aki Pulkkinen Marko Vauhkonen Source Type: research
