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Sub-millimeter nuclear medical imaging with high sensitivity in positron emission tomography using β⁺γ coincidences

JOURNAL OF INSTRUMENTATION 2014年第1期9卷 P01008-P01008页

作者： Lang, C. Habs, D. Parodi, K. Thirolf, P. G. Univ Munich Fak Phys LS Med Phys D-85748 Garching Germany Max Planck Inst Quantum Opt D-84748 Garching Germany

We present a nuclear medical imaging technique, employing triple-g trajectory intersections from beta(+)-gamma coincidences, able to reach sub-millimeter spatial resolution in 3 dimensions with a reduced requirement of reconstructed intersections per voxel compared to a conventional PET reconstruction analysis. This 'gamma-PET' technique draws on specific beta(+)-decaying isotopes, simultaneously emitting an additional photon. Exploiting the triple coincidence between the positron annihilation and the third photon, it is possible to separate the reconstructed 'true' events from background. In order to characterize this technique, Monte-Carlo simulations and image reconstructions have been performed. The achievable spatial resolution has been found to reach ca. 0.4 mm (FWHM) in each direction for the visualization of a Na-22 point source. Only 40 intersections are sufficient for a reliable sub-millimeter image reconstruction of a point source embedded in a scattering volume of water inside a voxel volume of about 1 mm(3) ('high-resolution mode'). Moreover, starting with an injected activity of 400 MBq for Br-76, the same number of only about 40 reconstructed intersections are needed in case of a larger voxel volume of 2 x 2 x 3 mm(3) ('high-sensitivity mode'). Requiring such a low number of reconstructed events significantly reduces the required acquisition time for image reconstruction (in the above case to about 140 s) and thus may open up the perspective for a quasi real-time imaging.

关键词： Gamma camera, SPECT, PET PET/CT, coronary CT angiography (CTA) Compton imaging Instrumentation for hadron therapy medical-image reconstruction methods and algorithms, computer-aided software

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Large-Area SiPM Pixels (LASiPs) in SPECT

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JOURNAL OF INSTRUMENTATION 2022年第7期17卷 C07021-C07021页

作者： Wunderlich, C. Guberman, D. Paoletti, R. Rugliancich, A. Passeri, A. Ist Nazl Fis Nucl Sez Pisa Largo Bruno Pontecorvo 3 Edificio C I-56126 Pisa Italy Univ Siena Dipartimento Sci Fis Terra & Ambiente Via Roma 56 I-53100 Siena Italy Univ Firenze Dipartimento Sci Biomed Sperimentali & Clin SBSC Viale Morgagni 50 I-50134 Florence Italy

A standard camera for Single Photon Emission Computed Tomography (SPECT) contains 50-100 photomultiplier tubes (PMTs) that occupy at least 50% of its volume. It is shielded by a thick layer of lead which makes it heavy and bulky. Replacing PMTs by silicon photomultipliers (SiPMs) could significantly reduce the weight and size of a SPECT camera. However, the main obstacle is the limited size of SiPMs: even with the largest commercially available SiPM of 6 x 6 mm(2) a few thousand channels would be needed to fill a camera. As a solution, we propose to use Large Area SiPM Pixels (LASiPs) which are built by summing the currents of several SiPMs into a single output. We developed a LASiP prototype summing 8 SiPMs using the MUSIC ASIC. To test the feasibility of using this solution in SPECT, we built a proof-of-concept micro camera that consisted of four of our LASiP prototypes coupled to a 40 x 40 x 8 mm(3) NaI(Tl) crystal. We were able to reconstruct simple images of a Tc-99m capillary with an intrinsic spatial resolution of similar to 2mm and an energy resolution of similar to 11.6%. We also simulated the system with Geant4, finding a good agreement with our experimental results. The simulations were extended to a larger camera, aiming to study the impact of pixel size, shape and noise.

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

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Experimental results of use of triple-energy X-ray beam with K-edge filter in multi-energy imaging

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JOURNAL OF INSTRUMENTATION 2016年第4期11卷 P04009-P04009页

作者： Kim, D. Lee, S. Jeon, P. -H. Eulji Univ Dept Radiol Sci 553 Sanseong Daero Songnam Gyeonggi South Korea Konyang Univ Dept Radiol Sci 158 Gwanjeodong Ro Daejoen South Korea Yonsei Univ Dept Radiol Sci 1 Yonseidae Gil Wonju Gangwon South Korea

Multi-energy imaging is useful for contrast enhancement of lesions, quantitative analysis of specific materials and material separation in the human body. Generally, dual-energy methods are applied to discriminating two materials, but this method cannot discriminate more than two materials. Photon-counting detectors provide spectral information from polyenergetic X-rays using multiple energy bins. In this work, we developed triple-energy X-ray beams using a filter with K-edge energy and applied them experimentally. The energy spectra of triple-energy X-ray beams were assessed by using a spectrometer. The designed triple-energy X-ray beams were validated by measuring quantitative evaluations with mean energy ratio (MER), contrast variation ratio (CVR) and exposure efficiency (EE). Then, triple-energy X-ray beams were used to extract density map of three materials, iodine (I), aluminum (Al) and polymethyl methacrylate (PMMA). The results of the thickness density maps obtained with the developed triple-energy X-ray beams were compared to those acquired using the photon-counting method. As a result, it was found experimentally that the proposed triple-energy X-ray beam technique can separate the three materials as well as the photon-counting method.

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

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Minimizing inconsistencies in gray values in small field-of-view dental computed tomography by modulating reconstruction filter intensity: simulation study

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JOURNAL OF INSTRUMENTATION 2024年第12期19卷

作者： Kim, Woosung Shim, Jiyong Jeon, Duhee Lim, Younghwan Lee, Soohyun Kim, Kyuseok Park, Chulkyu Cho, Hyosung Yonsei Univ Dept Radiat Convergence Engn Wonju South Korea Eulji Univ Dept Biomed Engn Seongnam South Korea Vatech Co R&D Ctr Hwaseong South Korea

Small field-of-view (FOV) cone-beam computed tomography (CBCT), which employs low-cost, small-area flat-panel detectors, is often used in dental CT where only a limited volume of an examined object is reconstructed using the standard filtered-backprojection algorithm. However, when examining with a small FOV, the surrounding structures located outside the FOV exacerbate the inhomogeneity of the inherent distribution of gray values (GVs) in the reconstructed CBCT volume. To address this issue, this study presents an effective method to minimize the inconsistencies in GVs in small FOV CBCT images by modulating reconstruction filter (ramp filter) intensity. To verify the efficacy of the proposed method, a feasibility study was conducted via a simulation using three-dimensional numerical mouth phantoms without metal insert and with metal inserts as highly attenuating dental materials. The mean GVs of the innermost FOV without correction were 60.3 and 63.1 for the cases of no metal and two metal inserts, respectively, which were approximately 7.8% and 6.5% greater than those of the corresponding reference FOVs. In contrast, the mean GVs with correction for all target FOVs were very close (<0.1%) to that of the reference FOV, indicating the efficacy of the proposed method. Consequently, small FOV dental CT images with good homogeneity of the GV distribution were successfully obtained using the proposed method, which is critical, particularly for assessing bone density in dental implantation surgery plan.

关键词： Data processing methods image reconstruction in medical imaging medical-image reconstruction methods and algorithms, computer-aided software Dental computed tomography Small field of view Exomass effect Gray value Ramp filter

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Tracking a moving point source using triple gamma imaging

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JOURNAL OF INSTRUMENTATION 2024年第1期19卷 P01001页

作者： Chmeissani, Mokhtar Kolstein, Machiel Arino-Estrada, Gerard Gabriel Macias-Montero, Jose Puigdengoles, Carles Garcia, Jorge Barcelona Inst Sci & Technol BIST Inst Fis Altes Energies IFAE Campus UAB E-08193 Bellaterra Barcelona Spain Univ Calif Davis Dept Biomed Engn Davis CA 95616 USA

With positron emission tomography (PET), the positron of a beta(+) emitter radioisotope annihilates with a nearby electron producing a pair of back-to-back 511 keV gamma rays that can be detected in a scanner surrounding the point source. The position of the point source is somewhere along the Line of Response (LOR) that passes through the positions where the 511 keV gammas are detected. In standard PET, an image reconstruction algorithm is used to combine these LORs into a final image. This paper presents a new tomographic imaging technique to locate the position of a beta(+) emitting point source without using a standard PET image reconstruction algorithm. The data were collected with a Proof-of-Concept (PoC) PET scanner which has high spatial and energy resolutions. The imaging technique presented in this paper uses events where a gamma undergoes Compton scattering. The positions and energies deposited by the Compton scattered gamma define the surface of a Compton cone (CC) which is the locus of all possible positions of the point source, allowed by the Compton kinematics. The position of the same point source is also located somewhere on the LOR. Therefore, the position of the point source is defined by the 3 gammas and is given by the intersection point of the LOR and the Compton cone inside the Field of View (FOV) of the scanner. We refer to this method as CCxLOR. This new technique can locate the point source with an uncertainty of about 1 mm, after collecting a minimum of 200 CCxLOR events.

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

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Mammogram density classification using deep convolutional neural network

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JOURNAL OF INSTRUMENTATION 2021年第1期16卷

作者： Nithya, R. Santhi, B. SASTRA Deemed Univ Sch Comp Thanjavur 613402 Tamil Nadu India

Artificial intelligence plays an important role in the classification of medical images for computerized diagnosis of the disease. The computer-aided medical imaging analysis system is developed for breast tissue density classification in mammogram images. Mammogram density is considered as significant predictive markers for breast cancer detection, treatment and management. Recently, deep learning techniques achieved impressive results in computer-assisted disease diagnosis. The deep learning technique such as the convolution neural network (CNN) is used for automated classification of mammogram density as fatty, dense and glandular. This study investigates how computer-aided medical imaging analysis system provides a reliable classification of mammogram density. The proposed methodology is evaluated using a mini-MIAS (Mammogram image Analysis Society) database. We obtained an average accuracy of 98.5%. So, the proposed CAD system aids the clinicians in the classification of mammogram density.

关键词： medical-image reconstruction methods and algorithms, computer-aided diagnosis medical-image reconstruction methods and algorithms, computer-aided software X-ray mammography and scinto- and MRI-mammography

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Multi-contrast CT imaging using a high energy resolution CdTe detector and a CZT photon-counting detector

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JOURNAL OF INSTRUMENTATION 2022年第1期17卷 P01004页

作者： Clements, N. Richtsmeier, D. Hart, A. Bazalova-Carter, M. Univ Victoria Dept Phys & Astron 3800 Finnerty Rd Victoria BC Canada

Computed tomography (CT) imaging with high energy resolution detectors shows great promise in material decomposition and multi-contrast imaging. Multi-contrast imaging was studied by imaging a phantom with iodine (I), gadolinium (Gd), and gold (Au) solutions, and mixtures of the three using a cadmium telluride (CdTe) spectrometer with an energy resolution of 1% as well as with a cadmium zinc telluride (CZT) detector with an energy resolution of 13%. The phantom was imaged at 120 kVp and 1.1 mA with 7 mm of aluminum filtration. For the CdTe data collection, the phantom was imaged using a 0.2 mm diameter x-ray beam with 96 ten-second data acquisitions across the phantom at 45 rotation angles. For the CZT detector, we had 720 projections using a cone beam, and the six detector energy thresholds were set to 23, 33, 50, 64, 81, and 120 keV so that three thresholds corresponded to the K-edges of the contrast agents. Contrast agent isolation methods were then examined. K-edge subtraction and novel spectrometric algebraic image reconstruction (SAIR) were used for the CdTe data. K-edge subtraction alone was used for the CZT data. Linearity plots produced similar R-2 values and slopes for all three reconstruction methods. Comparing CdTe methods, SAIR offered less noise than CdTe K-edge subtraction and better geometric accuracy at low contrast concentrations. CdTe contrast agent images of I, Gd, and Au offered less noise and greater contrast than the CZT images, highlighting the benefits of high energy resolution CdTe detectors for possible use in pre-clinical or clinical CT imaging.

关键词： computerized Tomography (CT) and Computed Radiography (CR) medical-image reconstruction methods and algorithms, computer-aided software X-ray detectors

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Optimal contrast enhancement achieved by the synthetic method for bone and tissue separation based on a dual-energy radiographic system

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JOURNAL OF INSTRUMENTATION 2013年第07期8卷 P07009-P07009页

作者： Kim, D. -H. Lee, Y. -J. Jeon, P. -H. Jo, B. -D. Kim, H. -J. Yonsei Univ Dept Radiol Sci Wonju 220710 Gangwon South Korea Yonsei Univ Res Inst Hlth Sci Wonju 220710 Gangwon South Korea

In dual-energy digital radiography (DEDR), the energy subtraction and equivalent thickness methods have been used for detecting thorax lesions. However, the image contrast of the energy subtraction method is low in comparion with that of the equivalent thickness and synthetic methods. Therefore, we applied the equivalent thickness and synthetic methods to material separation to enhance the bone and tissue contrast, and these results were compared with the results of the energy subtraction method in a chest DEDR system. The purpose of this work was to evaluate the image quality of the energy subtraction, equivalent thickness, and synthetic methods. In the energy subtraction method, the optimal weighting factors were selected for bone and tissue visualization, respectively. The equivalent thickness was obtained with a calibration procedure by using combinations of aluminum and polymethyl methacrylate (PMMA) blocks. The synthetic images were acquired with the known equation from the results of the equivalent thickness method. According to these results, the contrast-to-noise-ratio (CNR) values using the equivalent thickness and synthetic methods were improved than those obtained with the energy subtraction method in both aluminum and PMMA enhancement trial. In a cylindrical phantom study, the equivalent thickness and the synthetic method improved the contrast better than energy subtraction method. The synthetic method supplements the air shadows shown in the equivalent thickness method. We compared the enhanced images of bone and tissue with the energy subtraction, equivalent thickness, and synthetic methods. Our results showed that the effects of the synthetic method can improve the image contrast on both bone and tissue and overcome the bone shadows in tissue images in a DEDR system.

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

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A feasibility study for anatomical noise reduction in dual-energy chest digital tomosynthesis

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JOURNAL OF INSTRUMENTATION 2016年第1期11卷 P01016-P01016页

作者： Lee, D. Kim, Y. -s. Choi, S. Lee, H. Choi, S. Kim, H. -J. Yonsei Univ Coll Hlth Sci Dept Radiat Convergence Engn 1 Yonseidae Gil Wonju 220710 Gangwon South Korea Yonsei Univ Dept Radiol Sci 1 Yonseidae Gil Wonju 220710 Gangwon South Korea Yonsei Univ Res Inst Hlth Sci 1 Yonseidae Gil Wonju 220710 Gangwon South Korea

Lung cancer is the leading cause of cancer death worldwide. Thus, early diagnosis is of considerable importance. For early screening of lung cancer, computed tomography (CT) has been used as the gold standard. Chest digital tomosynthesis (CDT) is a recently introduced modality for lung cancer screening with a relatively low radiation dose compared to CT. The dual energy material decomposition method has been proposed for better detection of pulmonary nodules by means of reducing anatomical noise. In this study, the possibility of material decomposition in CDT was tested by both a simulation study and an experimental study using a CDT prototype. The Geant4 application for tomographic emission (GATE) v6 and tungsten anode spectral model using interpolating polynomials (TASMIP) codes were used for the simulation study to create simulated phantom shapes consisting of five inner cylinders filled with different densities of bone and airequivalent materials. Furthermore, the CDT prototype system and human phantom chest were used for the experimental study. CDT scan in both the simulation and experimental studies was performed with linear movement and 21 projection images were obtained over a 30 degree angular range with a 1.5 degree angular interval. To obtain materialselective images, a projectionbased energy subtraction technique was applied to high and low energy images. The resultant simulation images showed that dual-energy reconstruction could achieve an approximately 32% higher contrast to noise ratio (CNR) in images and the difference in CNR value according to bone density was significant compared to single energy CDT. Additionally, image artifacts were effectively corrected in dual energy CDT simulation studies. Likewise the experimental study with dual energy produced clear images of lung fields and bone structure by removing unnecessary anatomical structures. Dual energy tomosynthesis is a new technique;therefore, there is little guidance regarding its integrati

关键词： X-ray radiography and digital radiography (DR) computerized Tomography (CT) and Computed Radiography (CR) medical-image reconstruction methods and algorithms, computer-aided diagnosis medical-image reconstruction methods and algorithms, computer-aided software

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Quasi-real time acquisition and processing for biomedical IR and conventional imaging in surgery applications

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JOURNAL OF INSTRUMENTATION 2019年第3期14卷 P03011-P03011页

作者： Lay-Ekuakille, A. Visconti, P. de Fazio, R. Veneziano, D. Univ Salento Dept Innovat Engn Via Monteroni I-73100 Lecce Italy Asl Reggio Calabria Osped Riuniti Bianchi Melacrino Morelli Via G Melacrino 21 I-89124 Reggio Di Calabria Italy

Surgery decision making is almost basically adopted by imaging, and for internal organs, imaging is the only tool for proceeding on. Interested imaging is obtained by as Xrays, CT (computer Tomography), MRI (Magnetic Resonance Imaging), NMR (Nuclear Magnetic Resonance), ultrasound, scintigraphy, and PET (Positron Emission Tomography). All the above techniques are correlated to specific instrumentation, and their manufacturers include dedicated software to output high quality images. However, despite advances in biomedical instrumentation technology, new issues, regarding insurgence of pathologies so far unknown, require as much techniques to be developed. In this spirit, infrared thermography, for instance, can ride to help us to solve this thorny issue. Infrared images have been used to discriminate interested organs with respect to tissues and adherences that must be taken in consideration for continuing and optimizing the surgery process. Modified linear and circular Hough transform have been used to process captured images. This paper illustrates findings related to quasi-real time acquisition and processing during surgery. Infrared processing has been compared to another technique based on atomic force microscopy-based algorithm. Hough technique is also treated.

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

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