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Implementation of multiphase computed tomography angiography in management of patients with acute ischemic stroke in clinical practice
摘要： Multiphase computed tomography angiography (CTA) provides information on the status of major cranial arteries and extent of brain collateralization. The purpose of the study was to determine whether implementation of multiphase CTA in routine clinical practice was feasible, safe and useful. Patients with acute ischemic stroke (NIHSS (cid:1) 6) were included. Multiphase CTA was performed. Duration of performing multiphase CTA, inter-rater correlation and incidence of contrast-induced nephropathy (CIN) were studied. Infarct volume, incidence of hemorrhagic transformation, the rates of favorable outcome and death were compared between those with poor and intermediate-good collateralization. Multiphase CTA was performed in 108 patients. Mean duration on each multiphase CTA study was 4.8 min. Inter-rater reliability was intermediate-good (weighted kappa 0.7569, p < 0.001). CIN occurred in 3 patients (2.8%). There were no major intracranial/extracranial artery occlusion in 31 patients (29%) and there were severe stenosis or occlusions in 77 patients (71%). In the subgroup of patients with major artery severe stenosis or occlusion, 36 patients (36/77, 47%) had poor collateralization. Despite non-signi?cant difference in acute treatment, the patients with poor collateralization had larger infarct (123 vs 35 cc, p < 0.001) and poorer outcomes (mean modi?ed Rankin scale 3.86 vs 2.73, p = 0.011), while the differences in symptomatic hemorrhagic transformation (2.6 vs 7%, p = 0.385) and death rate (14 vs 12%, p = 0.825) were non-signi?cant, as compared to those with intermediate-good collateralization. Multiphase CTA was feasible and safe. Besides the status of major arteries, multiphase CTA provided information on collateralization, which was associated with the size of infarct and clinical outcomes.
关键词： Multiphase CTA,Asian,Thai,Acute stroke,Computed tomography angiography,Ischemic stroke
更新于2025-09-23 15:23:52
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Design and performance evaluation of high resolution small animal PET scanner based on monolithic crystal: a simulation study
摘要： Dedicated small-animal PET scanners functionality can be optimized by improving the sensitivity and spatial resolution of the scanner. Approximately most of the developed and commercially available small-animal PET scanners are equipped with pixelated scintillators; therefore, their spatial resolution is limited to the crystal pixel size. Complex fabrication, low-sensitivity, and disability in depth of interaction calculation (DOI) are the major disadvantages of pixelated crystals. However, monolithic scintillator crystals are known as one of the most commonly used substitutions, as they have higher sensitivity, DOI recognition, and lower cost. We already designed and implemented a dedicated small-animal PET scanner based on pixelated scintillator crystals and silicon photomultiplier (SiPM). In this study, we plan to present a new optimized design based on the monolithic crystal, with similar performance by the previous scanner. Then we would optimize the thickness of the monolithic crystals for animal PET scanners as a function of sensitivity and spatial resolution. All simulations were performed based on GEANT4, a validated Monte Carlo toolkit. We simulated a recently fabricated scanner with pixelated crystals and compared it with a simulated scanner based on an optimized monolithic crystal. The experimental setup used for comparison and validation is a small Animal PET consisting of ten pixelated modules. This study anticipates that by replacing a pixelated crystal (consist of 24 × 24 LYSO elements, and 2 × 2 × 10 mm3 crystal size) with a monolithic crystal (with 8 mm thickness and 50.2 × 50.2 entrance area), the average spatial resolution stays the same and sensitivity grows ～ 17% in the center of AFOV and also the fabrication cost dives remarkably. Simulation reveals that although the depth of interaction DOI was not taken into consideration, the crystals with 6 mm thickness have acceptable spatial resolution (～ 1.3 mm FWHM at the centre of the AFOV) and relatively good absolute sensitivity (～ 1.6%).
关键词： SPECT,coronary CT angiography (CTA),PET PET/CT,Gamma camera,Models and simulations
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - Krakow (2018.10.16-2018.10.18)] 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - Main Aortic Segmentation from CTA with Deep Feature Aggregation Network
摘要： In this study, we propose a Deep Feature Aggregation network (DFA-Net) for main aortic segmentation from CTA(Computed Tomography Angiography) by aggregating features from forwarding layers to leverage more visual information. To practically verify the effectiveness of our method, we collect 90 CTA volumes from Beijing AnZhen Hospital up to over 60 thousands 2-D slices. First, we use a level-set based algorithm to efficiently generate the dataset for training and validating the deep model. Then the dataset is divided into three parts, 70 instances are used for training and 5 instances are used for validating the best parameters, and the rest 15 instances are used for testing the generalization of the model. Finally, the testing result shows that mIoU(mean Intersection-over-Union) of the segmentation result is 0.943, which indicates that by properly aggregating more visual features in a deep network the segmentation model can achieve state-of-the-art performance.
关键词： CTA,feature aggregation,level set,main aortic segmentation
更新于2025-09-23 15:22:29
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Characterization of monolithic GAGG:Ce coupled to both PMT and SiPM array for gamma imaging in Nuclear Medicine
摘要： GaGG:Ce scintillation crystal is very useful for nuclear imaging purposes, thanks to its several advantages (high density, short decay time, high light yield and good energy resolution, no self-activity, no hygroscopic). However, only the recent improvements in the growth processes make it available with large size, in order to use it in monolithic configuration. The main drawbacks of pixelated crystals, as non-uniform response, high production costs and optical light loss, could be therefore overcome. In this work the characterization of this promising crystal coupled both to a single channel PMT (spectrometric purpose) and to a new technology SiPM (50% PDE and 74% geometrical fill factor) has been performed. The detection efficiency results good both for SPECT (87% at 122 keV) and for PET (18% at 356 keV) applications. However, the unexpected result arises from the energy resolution: at 356 keV 8.9% and 8.0% for single channel PMT and SiPM configuration, respectively. In other terms, the used SiPM allows to achieve higher energy resolution than single channel PMT. Moreover, a high imaging performance has been observed, with a millimeter intrinsic spatial resolution.
关键词： SPECT,PET PET/CT,Gamma camera,Intra-operative probes,Scintillators and scintillating fibres and light guides,coronary CT angiography (CTA),Scintigraphy and whole-body imaging
更新于2025-09-23 15:21:01
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Computed Tomography of Acquired Aortic Diseases
摘要： Computed tomography angiography (CTA) has replaced catheter angiography in the evaluation of aortic disease. CTA is able to evaluate occlusive and aneurysmal disease of the aorta. Inflammatory conditions of the aorta can also be assessed with CTA.
关键词： Aortitis,CTA,Aorta,Atherosclerosis,Aortic aneurysm
更新于2025-09-23 15:21:01
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Fast and efficient detection of 511 keV photons using Cherenkov light in PbF <sub/>2</sub> crystal, coupled to a MCP-PMT and SAMPIC digitization module
摘要： We study the possibility to use the Cherenkov light for the e?cient detection of 511 keV photons with the goal to use it in TOF-PET. We designed and tested two detection modules consisting of PbF2 crystals attached to Planacon MCP-PMT XP85012. Ampli?ed PMT signals are digitized by the SAMPIC module with high readout rate, up to 105 events/s, and a negligible contribution to the time resolution, below 20 ps (FWHM). We developed a fast 2D scanning system to calibrate the PMT time response and studied in details the timing characteristics of the Planacon PMT. Using a radioactive 22Na source we measured a detection e?ciency of 24% for 511 keV photons in a 10 mm thick crystal and a coincidence resolving time of 280 ps. We analyzed the main factors limiting the time resolution of the large-surface detection module and proposed solutions to improve it, which will be tested in our future project.
关键词： Photon detectors for UV, visible and IR photons (vacuum) (photomultipliers, HPDs, others),Cherenkov and transition radiation,Gamma camera, SPECT, PET PET/CT, coronary CT angiography (CTA)
更新于2025-09-23 15:19:57
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Front-end electronics of the Compact High Energy Camera
摘要： The Compact High Energy Camera (CHEC) is an ultra-sensitive single-photon counting camera being developed to image Cherenkov light flashes, peak λ ≈ 400 nm, generated during gamma-ray initiated particle showers. CHEC-S is the second prototype version camera and uses silicon photomultiplier (SiPM) pixels whereas CHEC-M, the first prototype, is based on multi-anode photomultipliers. The development and characterisation of CHEC-M, in the laboratory and on-telescope, validated the CHEC concept [1] and enabled several technical improvements to contribute to a new design. CHEC-S is currently undergoing full characterisation with on-telescope observations being planned for spring 2019. This article describes the new Front-End Electronics (FEE) modules developed and optimised to instrument imaging air Cherenkov telescope cameras equipped with SiPM photodetectors.
关键词： Full-waveform readout,Silicon photomultipliers,CHEC,CTA,Front-end electronics,TARGET,Readout,SST-2M
更新于2025-09-19 17:15:36
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Compton camera based on Timepix3 technology
摘要： The Compton camera concept is based on the reconstruction of recorded Compton scattering events of incoming gamma rays. The scattering of primary gamma ray occurs in the first detector (called scattering detector — usually thin) recording the position and energy of the recoiled electron. The scattered gamma quantum continues towards the second detector (called absorption detector - usually thick) where it is absorbed. The second detector records the energy and the position of this scattered gamma. Using the Compton scattering equation it is possible to determine the scattering angle, and estimate possible directions of the original gamma ray as a surface of a cone. When the Compton camera records the number of such events, the location and the shape of the gamma source can be reconstructed. Timepix3, a hybrid single photon counting imaging pixel detector, is a perfect device for creation of a compact Compton camera. Timepix3 is an event based readout chip (every hit pixel is immediately sent to a readout) and can record the time-of-arrival (ToA) and energy of an incident gamma simultaneously in each pixel. The chip offers high energy resolution (1 keV at 60 keV, 7 keV at 356 keV), as well as time resolution (1.6 ns). The Timepix3 readout chip can be combined with different sensor materials (Si, CdTe, CZT). In this contribution, we present a very compact detector system for imaging with gamma-rays using the Compton camera principle. The system consists of at least two layers of hybrid pixel detectors Timepix3 with the sensors being optimized for gamma-ray tracking. The front detector layer (scattering) is made of silicon of 1 mm thickness, while the last layer (absorbing) is equipped with thick CdTe or CZT sensors up to 2 mm in thickness. The total absorption of the whole detector can be very high if several CdTe or CZT layers are used. The maximal number of layers is not limited, but the practical evaluation was performed with 2 layers. Thanks to Timepix3 simultaneous measurement of ToA and energy, it is possible to precisely detect coincidence events in the detector layers. Based on the energy and position of these events, it is possible to estimate the possible direction of the original gamma. The angular resolution of the presented Compton camera depends on the detected energy, and it is in the order of 1 degree.
关键词： PET PET/CT,coronary CT angiography (CTA),Gamma camera,Particle tracking detectors,Compton imaging,SPECT
更新于2025-09-09 09:28:46
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Simulation and evaluation of high-performance cost-effective positron emission mammography scanner
摘要： Breast cancer is the main cause of tumor deaths in women, thus several imaging modalities have been introduced recently to better diagnose the disease. New breast cancer cases were estimated to reach up to 246,660 in 2017, and the mortality rate was above 40,000. Early diagnosis is widely approved as being essential for an e?ective treatment and it also helps to reduce the incidences and mortality rates. Positron Emission Mammography (PEM) is a breast-dedicated imaging device which uses a pair of annihilation gamma photons to detect abnormalities in the breast tissue. PEM device is compact in nature with a reduced ?eld of view to cover the entire breast region, and it employs few detector modules which makes it cost-e?cient. To e?ectively diagnose breast cancer at a very early stage, a device with high spatial resolution and high sensitivity is required. PEM detectors based on semiconductor materials are characterized by an excellent intrinsic spatial resolution but are not cost-e?ective, whereas detectors based on scintillator crystals are cost-e?ective but have limited intrinsic resolution to detect small breast lesions. This study focuses on improving the resolution of scintillator detectors by simulating a PEM scanner employing 1 × 1 × 10 mm3 laser processed scintillator crystal. The simulation was done with a GEANT4 application for emission tomography (GATE) software, and performance evaluation tests were carried out according to the National Electrical Manufacturers Association (NEMA) standards. The scanner geometry has 90 mm transaxial ?eld of view (FOV) and 105 mm axial FOV. Evaluation results showed that the scanner has 10.6% system sensitivity, 1.0 mm spatial resolution at the center of the FOV (CFOV) and at 2.5 cm transaxial direction. The resolution at the axial 2.5 cm position is 2.1 mm. NEMA image quality test and Derenzo phantom study showed that the scanner can easily resolve 1 mm in diameter hot rods.
关键词： PET PET/CT,X-ray mammography and scinto- and MRI-mammography,coronary CT angiography (CTA),Gamma camera,SPECT
更新于2025-09-09 09:28:46