123 research outputs found
Quantum annealing-based computed tomography using variational approach for a real-number image reconstruction
Objective: Despite recent advancements in quantum computing, the limited
number of available qubits has hindered progress in CT reconstruction. This
study investigates the feasibility of utilizing quantum annealing-based
computed tomography (QACT) with current quantum bit levels. Approach: The QACT
algorithm aims to precisely solve quadratic unconstrained binary optimization
(QUBO) problems. Furthermore, a novel approach is proposed to reconstruct
images by approximating real numbers using the variational method. This
approach allows for accurate CT image reconstruction using a small number of
qubits. The study examines the impact of projection data quantity and noise on
various image sizes ranging from 4x4 to 24x24 pixels. The reconstructed results
are compared against conventional reconstruction algorithms, namely maximum
likelihood expectation maximization (MLEM) and filtered back projection (FBP).
Main result: By employing the variational approach and utilizing two qubits for
each pixel of the image, accurate reconstruction was achieved with an adequate
number of projections. Under conditions of abundant projections and lower noise
levels, the image quality in QACT outperformed that of MLEM and FBP. However,
in situations with limited projection data and in the presence of noise, the
image quality in QACT was inferior to that in MLEM. Significance: This study
developed the QACT reconstruction algorithm using the variational approach for
real-number reconstruction. Remarkably, only 2 qubits were required for each
pixel representation, demonstrating their sufficiency for accurate
reconstruction.Comment: 14 pages, 8 figure
Relativistic Chiral Mean Field Model for Finite Nuclei
We present a relativistic chiral mean field (RCMF) model, which is a method
for the proper treatment of pion-exchange interaction in the nuclear many-body
problem. There the dominant term of the pionic correlation is expressed in
two-particle two-hole (2p-2h) states with particle-holes having pionic quantum
number, J^{pi}. The charge-and-parity-projected relativistic mean field
(CPPRMF) model developed so far treats surface properties of pionic correlation
in 2p-2h states with J^{pi} = 0^{-} (spherical ansatz). We extend the CPPRMF
model by taking 2p-2h states with higher spin quantum numbers, J^{pi} = 1^{+},
2^{-}, 3^{+}, ... to describe the full strength of the pionic correlation in
the intermediate range (r > 0.5 fm). We apply the RCMF model to the ^{4}He
nucleus as a pilot calculation for the study of medium and heavy nuclei. We
study the behavior of energy convergence with the pionic quantum number,
J^{pi}, and find convergence around J^{pi}_{max} = 6^{-}. We include further
the effect of the short-range repulsion in terms of the unitary correlation
operator method (UCOM) for the central part of the pion-exchange interaction.
The energy contribution of about 50% of the net two-body interaction comes from
the tensor part and 20% comes from the spin-spin central part of the
pion-exchange interaction.Comment: 22 pages, 12 figure
Physics, Machine Learning, and Medicine
In this manuscript, the relationship between physics and machine learning(ML)and the application to the medical field were informally described. The recent development of artificial intelligence, which is based on ML, urged us to apply the disease finding, disease classification, a decision-making system, and so on. I believe that the ML based medicine is a natural way to proceed. However, the important thing is not only to apply the ML technology in the various medical problems, but also to understand the causality in those problems : That’s the approach in the physics, and the quantitative consideration in the research in physics yields almost same ways used in the ML. In addition, the state-of-the-art ML such as a deep learning, becomes one of the powerful tools in a discovery in physics. Although, the medical field has a benefit with ML, we’d need to go to the next stage to find solutions in more fundamental problems with the medically developed ML methodology
Cervical Cancer Treatment using AI
In cervical cancer treatment, radiation therapy is selected based on the degree of tumor progression, and radiation oncologists are required to delineate tumor contours. To reduce the burden on radiation oncologists, an automatic segmentation of the tumor contours would prove useful. To the best of our knowledge, automatic tumor contour segmentation has rarely been applied to cervical cancer treatment. In this study, diffusion-weighted images (DWI) of 98 patients with cervical cancer were acquired. We trained an automatic tumor contour segmentation model using 2D U-Net and 3D U-Net to investigate the possibility of applying such a model to clinical practice. A total of 98 cases were employed for the training, and they were then predicted by swapping the training and test images. To predict tumor contours, six prediction images were obtained after six training sessions for one case. The six images were then summed and binarized to output a final image through automatic contour segmentation. For the evaluation, the Dice similarity coefficient (DSC) and Hausdorff distance (HD) was applied to analyze the difference between tumor contour delineation by radiation oncologists and the output image. The DSC ranged from 0.13 to 0.93 (median 0.83, mean 0.77). The cases with DSC <0.65 included tumors with a maximum diameter < 40 mm and heterogeneous intracavitary concentration due to necrosis. The HD ranged from 2.7 to 9.6 mm (median 4.7 mm). Thus, the study confirmed that the tumor contours of cervical cancer can be automatically segmented with high accuracy
Artificial intelligence-assisted interpretation of systolic function by echocardiogram
Objective: Precise and reliable echocardiographic assessment of left ventricular ejection fraction (LVEF) is needed for clinical decision-making. Recently, artificial intelligence (AI) models have been developed to estimate LVEF accurately. The aim of this study was to evaluate whether an AI model could estimate an expert read of LVEF and reduce the interinstitutional variability of level 1 readers with the AI-LVEF displayed on the echocardiographic screen.
Methods: This prospective, multicentre echocardiographic study was conducted by five cardiologists of level 1 echocardiographic skill (minimum level of competency to interpret images) from different hospitals. Protocol 1: Visual LVEFs for the 48 cases were measured without input from the AI-LVEF. Protocol 2: the 48 cases were again shown to all readers with inclusion of AI-LVEF data. To assess the concordance and accuracy with or without AI-LVEF, each visual LVEF measurement was compared with an average of the estimates by five expert readers as a reference.
Results: A good correlation was found between AI-LVEF and reference LVEF (r=0.90, p<0.001) from the expert readers. For the classification LVEF, the area under the curve was 0.95 on heart failure with preserved EF and 0.96 on heart failure reduced EF. For the precision, the SD was reduced from 6.1±2.3 to 2.5±0.9 (p<0.001) with AI-LVEF. For the accuracy, the root-mean squared error was improved from 7.5±3.1 to 5.6±3.2 (p=0.004) with AI-LVEF.
Conclusions: AI can assist with the interpretation of systolic function on an echocardiogram for level 1 readers from different institutions
Relativistic Hartree approach with exact treatment of vacuum polarization for finite nuclei
We study the relativistic Hartree approach with the exact treatment of the
vacuum polarization in the Walecka sigma-omega model. The contribution from the
vacuum polarization of nucleon-antinucleon field to the source term of the
meson fields is evaluated by performing the energy integrals of the Dirac Green
function along the imaginary axis. With the present method of the vacuum
polarization in finite system, the total binding energies and charge radii of
16O and 40Ca can be reproduced. On the other hand, the level-splittings in the
single-particle level, in particular the spin-orbit splittings, are not
described nicely because the inclusion of vacuum effect provides a large
effective mass with small meson fields. We also show that the derivative
expansion of the effective action which has been used to calculate the vacuum
contribution for finite nuclei gives a fairly good approximation.Comment: 15 pages, 8 figure
- …