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Radiographic restoration technique based on a simple scatter-and-noise degradation model to enhance image visibility in cone-beam computed tomography systems using an offset detector

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JOURNAL OF INSTRUMENTATION 2025年第2期20卷 C02042-C02042页

作者： Park, Jiwon Jeon, Duhee Han, Seohee Kim, Woosung Park, Sungmin Cho, Hyosung Yonsei Univ Dept Radiat Convergence Engn Wonju 26493 South Korea

This study presents a novel radiographic restoration technique based on a simple scatter- and-noise degradation model to enhance image visibility in cone-beam computed tomography (CBCT) systems using an offset detector. This method aims to address the challenges of scatter and noise in CBCT images. It involves three main steps: estimating the scattering intensity and transmission function from the acquired projections, restoring projections by removing scatter and noise using the estimated quantities, and reconstructing the image using the standard filtered-backprojection algorithm. To verify the efficacy of the proposed method, we conducted an experiment on a commercially available test phantom using a tabletop setup of the micro-CT configuration, demonstrating significant improvements in key image quality metrics such as contrast-to-noise ratio (CNR), noise power spectrum (NPS), and modulation transfer function (MTF). The CNR value of the restored CBCT image was approximately 2.1, representing a 5.3-fold improvement over the original image;the NPS value evaluated at a spatial frequency of 3 lp/mm was approximately 4.2 x 105, 55.3 times smaller than that for the descattered image;and the spatial resolution evaluated at an MTF value of 0.1 was approximately 1.1 lp/mm, 8.4 times greater than that of the original. Accordingly, our experimental results demonstrate that the proposed method significantly enhances the visibility and quality of CBCT images. The method is entirely software-based, making it practical for implementation without requiring additional hardware or higher radiation doses.

关键词： medical-image reconstruction methods and algorithms computer-aided diagnosis computer-aided software X-ray radiography and digital radiography (DR)

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Low-dose computed tomography denoising via hybrid transformer and residual dense network

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JOURNAL OF INSTRUMENTATION 2025年第3期20卷 C03013-C03013页

作者： Xu, Wenting Kim, Woosung Jeon, Duhee Cho, Hyosung Yonsei Univ Dept Radiat Convergence Engn Wonju 26493 South Korea

Low-dose computed tomography (CT) has become an essential diagnostic tool, but it suffers from lower image quality and higher noise compared to normal-dose CT, leading to reduced diagnostic accuracy. To address this issue, we designed a hybrid network that leverages the capabilities of stochastic window transformer and residual dense network (RDN) for enhanced image denoising. The architecture of the hybrid network is a U-shaped network composed of encoding and decoding parts. The encoding part employs a stochastic window transformer to capture global features using a stochastic window strategy with gaussian shift, effectively reducing noise and preserving image details, while the decoding part utilizes an RDN to enhance image details by integrating information across residual structures and dense blocks, which facilitates feature reuse and improves gradient flow. Additionally, a dual-path feature enhancement module was incorporated into the proposed hybrid network to facilitate direct feature transfer between the encoding and decoding parts, ensuring to get a fusion feature by combining low- and high-level features from both paths. The experimental results demonstrated that our hybrid network significantly outperformed other existing denoising methods, achieving a peak signal-to-noise ratio of approximately 33.8, a structural similarity index measure of 0.92, and a root-mean-squared error of 8.354. Consequently, our method enhances diagnostic accuracy while reducing patient's radiation doses, which provides an effective solution for low-dose CT image denoising.

关键词： medical-image reconstruction methods and algorithms computer-aided diagnosis image filtering image processing

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Comparison of different reconstruction methods for planar images in small gamma cameras

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JOURNAL OF INSTRUMENTATION 2011年第01期6卷 C01030-C01030页

作者： Cornelio, A. Gasperini, F. Lo Meo, S. Lanconelli, N. Moehrs, S. Marcatili, S. Bisogni, M. G. Del Guerra, A. Univ Bologna Dept Phys I-40127 Bologna Italy Univ Pisa Dept Phys I-56127 Pisa Italy Ist Nazl Fis Nucl Sez Pisa I-56127 Pisa Italy

In this work we present a comparison of different methods for reconstructing the position of the events detected by gamma cameras with small Field of View. This task was completed within a project aimed to the development of an ultra high resolution, MR compatible PET detector camera head based on SiPM detector. It is well known that the spatial resolution deteriorates and the displacement error (defined as the deviation of the reconstructed position from the true position) increases at the edges of the detector. Here we investigate the possibility of improving the detector performance by using different reconstruction methods. The usual algorithm based on the barycenter fails to track the true position near the edges of the detector. We implemented and tested four different algorithms: the classic barycenter, a modified barycenter method where we consider not the charge collected, but the charge squared (named "barycenter squared") [1], an algorithm based on the estimation of the skewness of the distribution of the light ("skewness") [2], and finally a method based on the minimization of the difference between the distribution of light and a suitable fitting function ("Newton"). It turns out that the use of reconstruction algorithms different from the classic barycenter can help to improve the performance of the system. In particular, the reconstruction error improves, especially at the edges of the detector. Our simulations show that it is feasible to get submillimeter planar spatial resolutions at the center of the detector and of about 1 mm at the edges of the detector.

关键词： image reconstruction in medical imaging Gamma camera SPECT PET PET/CT coronary CT angiography (CTA) medical-image reconstruction methods and algorithms computer-aided so

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The mechanism of edge effect in CdZnTe pixel detector and an improved design of pixel sizes of anode

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JOURNAL OF INSTRUMENTATION 2020年第4期15卷

作者： Wu, R. Heng, M. J. Zha, G. Q. Jie, W. Q. Northwestern Polytech Univ Sch Mat Sci & Engn MIIT Key Lab Radiat Detect Mat & Devices State Key Lab Solidificat Proc Xian 710072 Shaanxi Peoples R China Northwest Inst Nonferrous Met Res Xian 710072 Shaanxi Peoples R China

In this paper, the mechanism of the edge effect in Cadmium Zinc Telluride (CZT) pixel detectors is studied, and the energy spectrum performance and the charge collection efficiency of peripheral pixels with reduced sizes are analysed by computer-aided simulation and measurement. The results show that the distribution of the weighting potential, which is determined by the electrode structure, has significant influence on the edge effect. Reducing the sizes of peripheral pixels can optimize the weighting potential and improve the detection performance. A detector with reduced peripheral pixel sizes is prepared. We build a gamma imaging system using this kind of detector, test the spectrum response to Cs-137@662 keV and image a M10 nut under the collimated Am-241@59.5 keV. The measured spectrum of the edge/corner/intermediate pixels is consistent with the simulated spectrum and the obtained counting type gray-scale image of the nut clearly shows its shape and sizes. These results prove that reducing peripheral pixel sizes has practical value in gamma imaging technology.

关键词： Detector design and construction technologies and materials Gamma detectors (scintillators, CZT, HPGe, HgI etc) image reconstruction in medical imaging medical-image reconstruction methods and algorithms computer-aided diagnosis

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Study on the TB and non-TB diagnosis using two-step deep learning-based binary classifier

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JOURNAL OF INSTRUMENTATION 2020年第10期15卷

作者： Yoo, S. H. Geng, H. Chiu, T. L. Yu, S. K. Cho, D. C. Heo, J. Choi, M. S. Choi, I. H. Cung, C., V Nhung, N., V Min, B. J. Hong Kong Sanat & Hosp Med Phys & Res Dept 2 Village Rd Hong Kong Peoples R China Radisen Div Artificial Intelligent Clin Res 128Gongduk B-D Seoul South Korea Vietnam Natl Lung Hosp Natl TB Programme Hanoi Vietnam Chungbuk Natl Univ Hosp Dept Radiat Oncol 7761 Sunhwan Ro Cheongju South Korea

A deep learning-based binary classifier was proposed to diagnose tuberculosis (TB) and non TB disease using a chest X-ray radiograph. The proposed classifier comprised two-step binary decision trees, each trained by a deep learning model with convolution neural network (CNN) based on the PyTorch frame. Normal and abnormal images of chest X-ray was classified in the first step. The abnormal images were predicted to be classified into TB and non-TB disease by the second step of the process. The accuracies of first and second step were 98% and 80% respectively. Moreover, re-training could improve the stability of prediction accuracy for images in different data groups.

关键词： medical-image reconstruction methods and algorithms computer-aided diagnosis X-ray radiography and digital radiography (DR)

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On the feasibility of real time imaging in radiotherapy using antiproton beams

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JOURNAL OF INSTRUMENTATION 2009年第6期4卷 P06002-P06002页

作者： Kantemiris, I. Karaiskos, P. Georgiou, E. Angelopoulos, A. Giokaris, N. Dubnicka, S. Fulop, M. Kalogeropoulos, T. E. Univ Athens Dept Phys Nucl & Particle Sect GR-15771 Athens Greece Univ Athens Sch Med Dept Med Phys GR-11527 Athens Greece Inst Accelerating Syst & Applicat Athens 17214 Greece Slovak Acad Sci Inst Phys Bratislava Slovakia Slovak Hlth Univ Inst Prevent & Clin Med Bratislava Slovakia

Antiprotons whose potential in clinical applications has not yet been fully studied and explored, interact in a way similar to the widely used protons. The great advantage of antiprotons over protons is that at the end of their path annihilate and release about 1.88GeV more energy. Although many particles are produced by annihilation most of them escape from the target. Detecting a portion of these particles during patient's irradiation would offer the possibility to monitor the beam in the target in real time. In the current work we investigate the feasibility of real time imaging during radiotherapy by using antiproton beam. In this study a prostate case is simulated using one field and given a typical dose fraction of 2Gy to the target. Monte Carlo code is used to calculate the energy spectrum of the most prominent particles that escape from the target which could be detected outside the patient, as well as the degree of scattering of these particles, as an indication of merit for their use in order to produce an image which represents the absorption of the beam in the target. Results based on these criteria suggest that real time imaging is possible by detecting either charged pions or photons which mainly come from pi(0) decays or e(+)e(-) annihilation.

关键词： medical-image reconstruction methods and algorithms computer-aided so image reconstruction in medical imaging

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Evaluation of liver iron content using synchrotron radiation CT in iron-overload mice

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JOURNAL OF INSTRUMENTATION 2019年第5期14卷 P05023-P05023页

作者： Tang, R. Shi, B. Yan, F. Yang, G. Y. Chen, K-M Shanghai Jiao Tong Univ Rui Jin Hosp Dept Radiol Sch Med Shanghai 200025 Peoples R China Shanghai Jiao Tong Univ Neurosci & Neuroengn Ctr MedX Res Inst Shanghai 200030 Peoples R China

Evaluation of liver iron content (LIC) is crucial for the judgment of hepatic iron overload (HIO). Here, we evaluated the potential utility of synchrotron radiation (SR) CT for quantifying LIC in mice suffered from HIO. The mice models of HIO were made by the injection of iron dextran. A series of total iron injection doses of 0, 12.5, 25, 50 and 100 mg were used. SR CT imaging was performed using a detector with the pixel size of 6.5 mu m x 6.5 mu m at the energy level of 12 keV. The iron micro-depositions were pathologically confirmed using Prussian blue staining. The reconstructed transverse sections were obtained by applying the filtered back projection (FBP) algorithm with PITRE software. 3D visualization was performed using Amira 5.4. LIC was confirmed by an inductively coupled plasma (ICP) spectrometer. SR CT-derived LIC (LICCT) was defined as the volume ratio of iron depositions to the liver. The volume ratio was measured using imageJ software. SR CT presented a high-spatial resolution to clearly display iron micro-depositions in the iron-overload liver. Additionally, iron micro-depositions were found to distribute unevenly on 3D images. The LIC(CT)s were 0, (1.890 +/- 0.172)%, (4.148 +/- 0.282)%, (6.769 +/- 0.201)%, and (12.912 +/- 0.270)% for injection doses of 0 mg, 12.5 mg, 25 mg, 50 mg and 100 mg, respectively. LICCT had a strong linear correlation with injection dose (R-2 = 0.9930, P < 0.0001) or ICP-derived LIC (LICICP) (R-2 = 0.9644, P < 0.0001). The linear correlation between LICCT and LICICP could be expressed by an equation. Using this equation, LIC could be predicted by measuring LICCT. Therefore, SR CT imaging showed potential ability to quantify LIC. The imaging modality may be used for the evaluation of disease progression and therapeutic efficacy in mice models.

关键词： Computerized Tomography (CT) and Computed Radiography (CR) medical-image reconstruction methods and algorithms computer-aided diagnosis

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Material reconstruction with the Medipix2 detector with CdTe sensor

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JOURNAL OF INSTRUMENTATION 2011年第1期6卷 C01037-C01037页

作者： Guni, E. Durst, J. Michel, T. Anton, G. ECAP Univ Erlangen D-91058 Erlangen Germany

The new generation of photon counting pixelated X-ray detectors like the Medipix2 detector are gaining increasing interest in medical imaging. In contrast to conventional systems which integrate the charge released in the sensor they are able to count single photons. With this imaging detector it is possible to determine the energy of the incoming X-rays which opens up a new field of applications. One application is the detection of contrast agents in medical imaging which was shown for a silicon sensor. However the absorption efficiency of silicon is very low for the X-ray energies used in medical imaging. High-Z materials such as Cadmium Telluride (CdTe) are therefore promising candidates for the sensor material. With the hybrid design of the Medipix2 detector we are able to realize a photon counting pixelated X-ray detector with CdTe sensor. Crucial for material reconstruction are the energy response functions. With our simulation tool RoSi we are able to simulate these response functions. In this work first results and simulations concerning material reconstruction with a Medipix2 detector with CdTe sensor are shown.

关键词： X-ray detectors medical-image reconstruction methods and algorithms computer-aided so Detector modelling and simulations I (interaction of radiation with matter, interaction of photons with matter, interaction of hadrons with matter, etc)

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Toward clinical differential phase contrast mammography: preliminary evaluations and image processing schemes

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JOURNAL OF INSTRUMENTATION 2013年第5期8卷 C05009-C05009页

作者： Stampanoni, M. Wang, Z. Thuering, T. David, C. Roessl, E. van Stevendaal, U. Koehler, T. Trippel, M. Singer, G. Kubik-Huch, R. A. Hohl, M. K. Hauser, N. Paul Scherrer Inst Swiss Light Source CH-5232 Villigen Switzerland Univ Zurich Inst Biomed Engn Zurich Switzerland Swiss Fed Inst Technol Zurich Switzerland Paul Scherrer Inst Lab Micro & Nanotechnol CH-5232 Villigen Switzerland Philips Technol GmbH Hamburg Germany Kantonsspital Baden Inst Pathol CH-5404 Baden Switzerland Kantonsspital Baden Dept Radiol CH-5404 Baden Switzerland Kantonsspital Baden Interdisciplinary Breast Ctr Baden Dept Gynecol & Obstet CH-5404 Baden Switzerland

Phase contrast and scattering-based X-ray imaging are very promising tools for medical diagnostics because they are able to provide additional and complementary information to traditional absorption-based methods. In this work, we discuss the investigation of three native breast samples with a grating interferometer equipped with a conventional X-ray tube, the full study being published in ref. [1]. We briefly introduce a method to fuse absorption, differential phase and scattering signals into a unique image with improved diagnostic contents. Our approach yields complementary and inaccessible information on the electron density distribution and the small-angle scattering power of the sample which could potentially answer clinically relevant, yet unresolved questions such as the capability to unequivocally discern between (pre-) malignant changes and post-operative scars or to distinguish cancer-invaded regions within healthy tissue.

关键词： X-ray mammography and scinto- and MRI-mammography image filtering Data processing methods medical-image reconstruction methods and algorithms computer-aided so

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A novel approach to separate absorption, refraction and scattering in analyzer based lung imaging

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JOURNAL OF INSTRUMENTATION 2020年第5期15卷

作者： Menk, R. H. Rigon, L. Brombal, L. Donato, S. Petris, C. Arfelli, F. ELETTRA Sincrotrone Trieste Trieste TS Italy INFN Sect Trieste Trieste TS Italy Univ Trieste Trieste TS Italy Univ Saskatchewan Dept Med Imaging Saskatoon SK S7N 5A2 Canada Univ Calabria Arcavacata Di Rende CS Italy

In analyzer based imaging (ABI) scattering can be efficiently separated from refraction and absorption effects by acquiring three images of the sample. In the scattering image the lungs appear as areas of high intensity signal (area contrast), which is modulated by the local thickness of the scattering tissue intersecting the X-ray path. The scattering signal is also included in the socalled apparent absorption image, where it adds to the absorption contrast thanks to the extinction of rays which are deviated outside the analyzer crystal's acceptance window. The presence of scattering can be emphasized in the ratio between two images acquired with a strongly detuned and a perfectly tuned analyzer crystal, respectively: we name this ratio as the amplified scatter image. In this paper we present ABI scattering methods applied to postmortem mouse lung imaging to assess their diagnostic value. For this purpose images have been acquired at the SYRMEP beamline of the ELETTRA synchrotron in Trieste (Italy) with the Argus time delay integration CCD detector at a photon energy of 25 keV. Subsequently the parametric images, including the amplified scatter image have been obtained, and contrast and signal-to-noise ratio have been evaluated. It is noteworthy that images have been acquired with a radiation dose of some mGy, thus are compatible with dose restricted medical imaging settings such as mammography.

关键词： medical-image reconstruction methods and algorithms computer-aided software X-ray radiography and digital radiography (DR) X-ray monochromators X-ray detectors

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