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List-mode quantitative joint reconstruction of activity and attenuation maps in Time-of-Flight PET

JOURNAL OF INSTRUMENTATION 2023年第9期18卷 P09041页

作者： Hemmati, Hamidreza Kamali-Asl, Alireza Ghafarian, Pardis Rahmim, Arman Zaidi, Habib Ay, Mohammad Reza Univ Tehran Med Sci Res Ctr Mol & Cellular Imaging Tehran Iran Univ Calif Davis Dept Biomed Engn Davis CA USA Shahid Beheshti Univ Dept Med Radiat Engn Tehran Iran Shahid Beheshti Univ Med Sci Masih Daneshvari Hosp NRITLD Chron Resp Dis Res Ctr Tehran Iran Shahid Beheshti Univ Med Sci Masih Daneshvari Hosp PET CT & Cyclotron Ctr Tehran Iran Univ British Columbia Dept Radiol & Phys Vancouver BC Canada BC Canc Res Ctr Dept Integrat Oncol Vancouver BC Canada Geneva Univ Hosp Div Nucl Med & Mol Imaging Geneva Switzerland Univ Geneva Neuroctr Geneva Switzerland Univ Groningen Univ Med Ctr Groningen Dept Nucl Med & Mol Imaging Groningen Netherlands Univ Southern Denmark Dept Nucl Med Odense Denmark Univ Tehran Med Sci Dept Med Phys & Biomed Engn Tehran Iran

Quantitative PET imaging requires accurate determination of patient-specific attenuation maps, which remains challenging on hybrid PET/MRI systems owing to the lack of a direct relationship between MR image intensity and attenuation coefficients. The aim of the present study is to develop a list-mode based algorithm for accurate and robust attenuation correction of PET data using time-of-flight (TOF) emission information. We analyze and address the challenges of list-mode emission-based maximum-likelihood joint estimation of activity and attenuation (LM-MLAA) in state-of-the-art PET imaging. The proposed method exploits a rapid on-the-fly system matrix calculation algorithm based on elliptic integrals while updating the attenuation map from accumulating list-mode coincidences to achieve accelerated image reconstruction. The scattering compensation is incorporated inside it using an iterative approach in such that the current estimation of attenuation map used on a course grid sampling scattering points to make an estimate of scattering. The performance of the proposed LM-MLAA approach was evaluated on Monte Carlo simulations of a phantom at different time resolutions. The contrast and noise for hot and cold regions on reconstructed images at different time resolutions were analysed. The estimated attenuation map exhibits resilience against noise, effectively eliminates high-frequency cross-talk even in the absence of prior information on attenuation coefficients, and enables discrimination among different anatomical regions in the reconstructed image. The error in the mean estimated attenuation coefficients after 50 iterations was similar to 2% in water and similar to -14% in Teflon regions for TOF resolutions corresponding to those of most current commercial PET systems (similar to 500 ps). The proposed LM-MLAA framework can be used for joint reconstruction of activity and attenuation maps from list-mode emission data as standalone or a complementary approach to ex

关键词： Gamma camera SPECT PET PET/CT coronary CT angiography (CTA) medical-image reconstruction methods and algorithms computer-aided diagnosis Multi-modality systems

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Deformable 3D medical image registration with convolutional neural network and transformer

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JOURNAL OF INSTRUMENTATION 2023年第4期18卷 P04029页

作者： Deng, Liwei Zou, Yanchao Huang, Sijuan Yang, Xin Wang, Jing Harbin Univ Sci & Technol Sch Automation Xuefu Rd Harbin 150080 Peoples R China Sun Yat Sen Univ Canc Ctr Dept Radiat Oncol Dungfung Rd East Guangzhou 510060 Peoples R China South China Normal Univ Inst Brain Res & Rehabil Zhongshan Ave West Guangzhou 510631 Peoples R China

Deformable registration of medical images based on deep learning has been the research focus this year. Convolutional Neural Network (CNN) and the transformer are the most common backbone and have been shown to enhance registration accuracy. However, CNN lacks the ability to contact long-distance information, and the transformer lacks the ability to capture local information. Whichever subtle feature loss may lead to disastrous consequences in the analysis of clinical medicine. This paper presented a novel registration network named Information Complementation Network (ICN). We aim to improve the registration accuracy by complementing the lost information. Pure transformers can establish long-distance spatial information about the image. Proposed meshing patch embedding can minimize the loss of local information and expand the receptive field to extract long-distance information. The dual-path decoder in ICN is designed to restore information furthest. We experimented on 3D brain MRI data and quantitatively compared several excellent registration models. Compared with conventional methods, the dice coefficient increased by 3%. Compared with the advanced methods, the dice coefficient increased by 1%. The number of foldings was reduced by about 50% without any loss of registration accuracy. Each evaluation metric of the trained models on liver CT images was higher than other methods. By fully complementing the lost or invalid information, ICN achieved higher registration accuracy and smoother deformation field. The innovation and contribution of this paper have the potential to be applied to clinical research or medical image processing.

关键词： medical-image reconstruction methods and algorithms computer-aided diagnosis image processing MRI (whole body cardiovascular breast others) MR-angiography (MRA)

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Preliminary study of integrated C-arm CT/SPECT imaging system for online adaptive 3D brachytherapy using Monte Carlo simulation

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JOURNAL OF INSTRUMENTATION 2023年第4期18卷 C04005-C04005页

作者： Lee, M. Lee, H. Seong, S. Park, H. Kim, H. Min, C. Choi, H. Choa, H. Yonsei Univ Dept Radiat Convergence Engn Wonju South Korea Yonsei Univ Wonju Severance Christian Hosp Dept Radiat Oncol Wonju Coll Med Wonju South Korea

Recent advancements in high-dose-rate brachytherapy have led to remarkable clinical outcomes. However, these new developments can cause unknown uncertainties with respect to actual dose delivery, which are yet to be clarified. Therefore, an accurate dose verification system is required. Currently, procedures for image-guided adaptive brachytherapy are constrained by the following limitations: (1) patient transportation between the treatment room and CT/MR (computerized tomography/magnetic resonance) imaging room can displace the application position, (2) the physiological and anatomical changes in the patient's body cannot be observed during the treatment schedule involving 3-10 fraction, and (3) the movement of the radioactive source inside the body is impossible to track. This study proposes a concept of an integrated online imaging system, which is based on integrated CT and single-photon emission computed tomography (SPECT), namely, the C-arm CT/SPECT system-a combination of a C-arm fluoro-scopic x-ray imaging system and an attachable parallel-hole collimator over the imaging detector. The Geant4 software is used to simulate the application of the C-arm CT/SPECT system for Ir-192-based brachytherapy in a pelvis-like phantom. To improve the image quality of C-arm CT/SPECT acquired with limited-angle information, we utilized an adaptive-steepest-descent -projection-onto-convex-sets framework that incorporates additional prior information for the proposed system. Furthermore, we confirmed that SPECT images can be obtained using a parallel -hole collimator and estimated the dose distribution in the medium and CT/SPECT fusion imaging during treatment. This strategy is expected to be effectively implemented in online image-guided adaptive brachytherapy and patient-dose verification.

关键词： Multi-modality systems Gamma camera SPECT medical-image reconstruction methods and algorithms C-arm online adaptive 3D brachytherapy

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Experiment and simulation of microwave detection using IQ demodulation method for breast tumor screening

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JOURNAL OF INSTRUMENTATION 2022年第3期17卷

作者： Li, C. P. Yao, Y. Li, Z. H. Cheng, L. Zhang, Y. Liu, H. Q. Lanzhou Univ Lanzhou 730000 Gansu Peoples R China Chinese Acad Sci Inst Plasma Phys Hefei 230031 Anhui Peoples R China Univ Sci & Technol China Hefei 230026 Anhui Peoples R China Hefei Comprehens Natl Sci Ctr Inst Energy Hefei 230071 Anhui Peoples R China

Breast cancer has become the most diagnosed cancer in the world. Microwave detection the breast tumor is attractive due to its high dielectric property contrast between different tissues of tumor. In this paper, we proposed an In-phase-Quadrature (IQ) demodulation-based method to detect the breast tumor with microwave at a frequency of 1.3 GHz. The microwave detection system consists of two signal generators, 12 transmitting/receiving antennas, two talent switches, a phantom and an IQ-Mixer. The amplitude information at the receiving antennas can be obtained by analyzing the difference frequency signals generated with two microwave signal generators. We also use the finite-difference time-domain (FDTD) method for simulation verification, which can simulate the propagation of the electromagnetic wave. Through experiments and simulations of microwave hardware system and FDTD method, it can be proved that the results are consistent. The experimental and simulation results show that when the tumor phantom diameter decreases or its depth from the receiving antenna increases, whether there is a tumor phantom can be clearly distinguished. Moreover, we also explore the effects of different tumor phantom locations on the receiving antennas. The results show that it is feasible to detect the breast tumor with the IQ demodulation method based on microwave.

关键词： medical-image reconstruction methods and algorithms computer-aided diagnosis Plasma diagnostics interferometry spectroscopy and imaging

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Depth resolved pencil beam radiography using AI - a proof of principle study

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JOURNAL OF INSTRUMENTATION 2022年第6期17卷 P06012页

作者： Haggstrom, I Carter, L. M. Fuchs, T. J. Kesner, A. L. Mem Sloan Kettering Canc Ctr Dept Radiol 1275 York Ave New York NY 10021 USA Mem Sloan Kettering Canc Ctr Dept Med Phys 1275 York Ave New York NY 10021 USA Mt Sinai Sch Med Hasso Plattner Inst Digital Hlth Dept Pathol 1468 Madison Ave New York NY USA

Aims: clinical radiographic imaging is seated upon the principle of differential keV photon transmission through an object. At clinical x-ray energies the scattering of photons causes signal noise and is utilized solely for transmission measurements. However, scatter ??? particularly Compton scatter, is characterizable. In this work we hypothesized that modern radiation sources and detectors paired with deep learning techniques can use scattered photon information constructively to resolve superimposed attenuators in planar x-ray imaging. methods: we simulated a monoenergetic x-ray imaging system consisting of a pencil beam x-ray source directed at an imaging target positioned in front of a high spatial-and energy-resolution detector array. The setup maximizes information capture of transmitted photons by measuring off-axis scatter location and energy. The signal was analyzed by a convolutional neural network, and a description of scattering material along the axis of the beam was derived. The system was virtually designed/tested using Monte Carlo processing of simple phantoms consisting of 10 pseudo-randomly stacked air/bone/water materials, and the network was trained by solving a classification problem. RESULTS: from our simulations we were able to resolve traversed material depth information to a high degree, within our simple imaging task. The average accuracy of the material identification along the beam was 0.91 ?? 0.01, with slightly higher accuracy towards the entrance/exit peripheral surfaces of the object. The average sensitivity and specificity was 0.91 and 0.95, respectively. Conclusions: our work provides proof of principle that deep learning techniques can be used to analyze scattered photon patterns which can constructively contribute to the information content in radiography, here used to infer depth information in a traditional 2D planar setup. This principle, and our results, demonstrate that there is information in Compton scattered photons, and

关键词： Compton imaging medical-image reconstruction methods and algorithms computer-aided diagnosis medical-image reconstruction methods and algorithms computer-aided software

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A new limited-angle CT reconstruction algorithm based on the local anisotropic total variation restoration of continuity

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JOURNAL OF INSTRUMENTATION 2022年第12期17卷 P12018页

作者： Xiao, Yu Zhong, Wang Li, Yongcun Hu, Xiaofang Xu, Feng Univ Sci & Technol China Chinese Acad Sci Key Lab Mech Behav & Design Mat 96 JinZhai Rd Hefei 230027 Peoples R China Taiyuan Univ Technol Coll Mech Shanxi Key Lab Mat Strength & Struct Impact 79 Yingzexi Dajie Taiyuan 030024 Peoples R China

A new limited-angle computed tomography(CT) reconstruction algorithm based on local detail information restoration in the CT image projection domain was proposed in this paper. The lost projection information could be repaired with the new algorithm called local anisotropic total variation repair method of sinogram (LATV). According to the continuity of local gradient in sinogram, local high frequency characteristics can be improved which are blurred by conventional TVM. A series of numerical reconstruction experiments were conducted to validate the new algorithm. The overall quality of images reconstructed by new algorithm was better than conventional TVM algorithm when quantitatively evaluated. Then, a local region with rich details was selected in order to evaluate the reconstruction effect of the internal details. From the perspective of three image quality evaluation parameters, it was shown that the local high frequency details were well repaired. Finally, the reconstruction quality was evaluated by actual CT experimental data. The new method also performed better than conventional method. Therefore, the new LATV algorithm proposed in this paper may be a new method suitable for limited-angle CT reconstruction problems.

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

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Reduction of contribution of scattered photons by optimization of energy window settings in 201Tl SPECT imaging: a simulation study

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JOURNAL OF INSTRUMENTATION 2022年第8期17卷 P08017页

作者： Noori-Asl, Mahsa Hosseinifar, Hoora Univ Mohaghegh Ardabili Fac Sci Dept Phys Ardebil Iran

Introduction and Objectives: detection of Compton scattered photons is one of the effective factors in reducing the quality of SPECT images. The aim of this study is to reduce the contribution of scattered counts included in the main energy window for 201Tl SPECT imaging in two steps: first step, by determining the location and width of the optimal main energy window, and second step, by using the optimal correction *** and methods: in this study, the Monte Carlo program is used to simulate the required phantoms (a cylindrical phantom consist of two small cylinders with different diameters and a simple cardiac phantom), and to produce the projections related to different energy ***: according to the simulation results, among the 13 investigated energy windows, the 30%-wide window with the central energy of 75 keV is determined as the optimal main window for 201Tl SPECT imaging. Also, from the results of this study, two energy window settings are proposed as the most suitable settings for scatter correction of 201Tl SPECT images. In the first case, a second energy window (a 34%-wide window centered at 51 keV) with counts approximately equal to the scattered counts of the optimal main window, and in the second case, two narrow windows (a 8%-wide window centered at 56 keV and a 6%-wide window centered at 92 keV) on both sides of the optimal main window and at a certain distance from two sides of this window are determined as the most suitable energy window settings for these ***: using the optimal main window together with the optimal scatter correction settings proposed in this study leads to a significant improvement of the contrast of 201Tl SPECT images with an acceptable noise level.

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

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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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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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