Computed Tomography Devices Research Articles

Bilgisayarlı Tomografi İle Yapılan Perkütan Torasik Kitle Biyopsilerinde Lenfositlerdeki DNA Hasarının Değerlendirilmesi

Purpose: The increase in the medical and industrial uses of radiation in the last century has caused people to be exposed to higher doses of radiation. Although the harms of high-dose radiation on human health are known, the effects of low-dose radiation on health have not yet been fully elucidated. In this study, we aimed to investigate DNA damage in lymphocytes in patients with lung, pleura/thoracic wall masses planned for percutaneous thoracic mass biopsy with computed tomography (CT). Methods: Sixteen patients referred to the Radiology Clinic of a public institution hospital with lung, pleura/thoracic wall masses and scheduled to undergo a CT-guided percutaneous biopsy were included in the study. All the biopsies were performed with a 128-slice CT device (Definition AS, Siemens Medical Solutions, Forchheim, Germany). Lymphocytes were analyzed using the comet assay in the venous blood samples taken from the patients before and after the biopsy procedure. DNA damage was quantitatively evaluated with the imaging analysis method. Results: In the CT analysis data of the study group, the mean scan distance was found to be 19.92±3.60 sec, the mean total milliampere-seconds was 807.43±304.51, and the mean dose-length product was 765.44±278.36 mGy.cm. The mean comet score was 200.50±40.54 for the cells that migrated before the procedure and 237.37±27.85 for those migrating after the procedure. The post-procedure comet scores significantly increased compared to the pre-procedure comet scores (p=0.038). Conclusion: Post-procedure DNA damage was detected in patients who underwent CT-guided percutaneous biopsy.

Bilgisayarlı Tomografi Görüntülerinden Derin Öğrenme ve Makine Öğrenmesi ile covid-19 Hastalığının Teşhisi

Abstract
 The new virus disease (COVID-19) first came to China towards the end of December 2019 and became a pandemic all over the world. The disease caused a large number of people to be infected and die. Rapid diagnosis of the disease is of great importance in controlling transmission. A computed Tomography device provides successful results in the diagnosis of COVID-19 disease. In this study, two-class (COVID-19 and normal) data sets were created from 7200 lung Computed Tomography images diagnosed between March 2020 and November 2020 in a private hospital with the help of specialist physicians. Verification and testing processes were carried out on Artificial Neural Network (ANN), Support Vector Machine (SVM), K-Nearest Neighbour (KNN) algorithms from Machine Learning algorithms, and ResNet-50, DenseNet-201, InceptionResNetV2, Inceptionv3, VGG-16, Xception architectures from Deep Learning models. As a result of the studies, the DenseNet-201 architecture obtained the highest result from deep learning models with %99,35 training and test %98,75 accuracy rates, respectively. ANN %97,6, KNN %97,4 and SVM %96,9 accuracy rates were obtained from machine learning.

Three-dimensional reconstruction and morphometric analysis of mandible of Hamdani sheep: A computed tomography (CT) study

In this study, anatomical, morphometric and volumetric analyses of the mandible of Hamdani sheep were performed using computed tomography (CT) and three-dimensional (3D) software. For this purpose, 16 (eight males, eight females) Hamdani sheep heads were used. Images of these heads were taken on a 64-detector CT device applying 80 kV, 200 MA, 639 mGY, and 0.625 mm section thickness. Scan images of the mandible of each subject were converted into three-dimensional models using 3D software and reconstructed. Surface, volume and linear measurements (24) of the mandible were performed on the models. All the measurements were expressed as mean ± SD. The examinations determined that the mandible's volume and surface area values were more significant in males than females. Mandible length (GOC-ID) was 169.01±0.74 mm, and its height (GOV-CR) was 95.50±0.64 mm in males. In morphometric evaluations, statistically significant differences were observed between males and females in L2 (PC-ID), L6 (GOC-FMN), L14 (MTR-MH), L19(SI), Volume and Surface area measurement parameters (P<0.05). It is thought that the morphometric data obtained will be a reference in pathological conditions, taxonomy studies, and interventional surgical treatment applications to be performed on the site.

Accuracy of CAD-CAM Surgically Guided Tooth Autotransplantation Using Guided Templates and Custom-designed Osteotomes in Human Cadaver Mandibles

IntroductionA major challenge in dentistry is the replacement of teeth lost prematurely due to trauma, caries, or malformations; especially in growing patients. The aim of this study was to assess the accuracy of CAD-CAM surgically guided tooth autotransplantation in cryopreserved cadaver mandibles using guided templates and custom-designed osteotomes. MethodsCryopreserved human cadaver heads were digitized and scanned using an intraoral optical scanner and a large-volume cone beam computed tomography device. First, virtual surgical planning was performed to create a 3D tooth replica, 2 surgical guides, and a custom-made osteotome for each single-rooted tooth autotransplantation procedure/case. Surgical sockets were created in the selected mandibles using guided tooling consisting of an initial guided osteotomy with implant burs and a final guided osteotomy using custom osteotomes. After tooth autotransplantation, second large-volume cone beam computed tomography images of the 5 cadaver mandibles were obtained. The discrepancy in mm within the 3D space (apical and mesiodistal deviations) between the final position of the autotransplanted teeth and their digitally planned 3D initial position was calculated and analyzed statistically (P < .05). ResultsAll donor teeth were placed without incident within their newly created sockets in the real mandibles. The mean difference between the digitally planned root apex position and the final tooth position was 2.46 ± 1.25 mm. The mesiodistal deviation of the autotransplanted teeth was 1.63 ± 0.96 mm. ConclusionsThe autotransplantation of single-rooted teeth with custom-designed and 3D-printed surgical tooling provided promising results. The technique was able to create surgically prepared sockets that could accommodate transplanted teeth in mandibles.

Risk-minimizing tube current modulation for computed tomography

Every computed tomography (CT) examination is accompanied by radiation exposure. The aim is to reduce this as much as possible without compromising image quality by using atube current modulation technique. CT tube current modulation (TCM), which has been in use for about two decades, adjusts the tube current to the patient's attenuation (in the angular and z‑directions) in away that minimizes the mAs product (tube current-time product) of the scan without compromising image quality. This mAsTCM, present in all CT devices, is associated with asignificant dose reduction in those anatomical areas that have high attenuation differences between anterior-posterior (a.p.) and lateral, particularly the shoulder and pelvis. Radiation risk of individual organs or of the patient is not considered in mAsTCM. Recently, aTCM method was proposed that directly minimizes the patient's radiation risk by predicting organ dose levels and taking them into account when choosing tube current. It is shown that this so-called riskTCM is significantly superior to mAsTCM in all body regions. To be able to use riskTCM in clinical routine, only asoftware adaptation of the CT system would be necessary. With riskTCM, significant dose reductions can be achieved compared to the standard procedure, typically around 10%-30%. This is especially true in those body regions where the standard procedure shows only moderate advantages over ascan without any tube current modulation at all. It is now up to the CT vendors to take action and implement riskTCM.

A Morphometric Comparison of the Skulls of Akkaraman and Kangal Akkaraman Sheep on a Three-Dimensional Model Using Computed Tomography

This study was carried out to make was to determine the craniometric characteristics of the crania of Akkaraman and Kangal Akkaraman sheep, local breeds of Turkey, by using computed tomography (CT). Equal numbers of healthy male Akkaraman and Kangal Akkaraman sheep heads aged 8-12 months were used in the study (n=12/group). The images were obtained by scanning the heads with a CT device. These images were converted into a three-dimensional structure using the 3D Slicer program and their morphometric measurements were calculated. In the study, a total of 13 parameters and 5 indexes were measured in the skull. As a result, the morphometric differences of the skulls of Akkaraman and Kangal Akkaraman sheep were determined by statistical methods. All the characteristics examined were expressed as mean ± SE. Results of our study, when the craniometric data were examined a statistically significant difference was found in skull length, skull width, greatest length of the nasal bone, greatest breadth across the nasal, medial frontal length, cranial width, facial width, height of the foramen magnum, greatest breadth of the foramen magnum, greatest frontal breadth and least breadth between the orbits parameters (P 0.05). It is thought that the presented study may be useful to veterinarians in the fields of surgery and clinical practice, and to studies in the field of zooarchaeology, as well as sheep taxonomy.

Assessment of subjective image quality, contrast to noise ratio and modulation transfer function in the middle ear using a novel full body cone beam computed tomography device

BackgroundMulti slice computed tomography (MSCT) is the most common used method in middle ear imaging. However, MSCT lacks the ability to distinguish the ossicular chain microstructures in detail resulting in poorer diagnostic outcomes. Novel cone beam computed tomography (CBCT) devices’ image resolution is, on the other hand, better than MSCT resolution. The aim of this study was to optimize imaging parameters of a novel full body CBCT device to obtain optimal contrast to noise ratio (CNR) with low effective dose, and to optimize its clinical usability.MethodsImaging of five anonymous excised human cadaver temporal bones, the acquisition of the effective doses and the CNR measurements were performed for images acquired on using Planmed XFI® full body CBCT device (Planmed Oy, Helsinki, Finland) with a voxel size of 75 µm. All images acquired from the specimens using 10 different imaging protocols varying from their tube current exposure time product (mAs) and tube voltage (kVp) were analyzed for eight anatomical landmarks and evaluated by three evaluators.ResultsWith the exception of protocol with 90 kVp 100 mAs, all other protocols used are competent to image the finest structures. With a moderate effective dose (86.5 µSv), protocol with 90 kV 450 mAs was chosen the best protocol used in this study. A significant correlation between CNR and clinical image quality of the protocols was observed in linear regression model. Using the optimized imaging parameters, we were able to distinguish even the most delicate middle ear structures in 2D images and produce accurate 3D reconstructions.ConclusionsIn this ex vivo experiment, the new Planmed XFI® full body CBCT device produced excellent 2D resolution and easily created 3D reconstructions in middle ear imaging with moderate effective doses. This device would be suitable for middle ear diagnostics and for e.g., preoperative planning. Furthermore, the results of this study can be used to optimize the effective dose by selecting appropriate exposure parameters depending on the diagnostic task.

MIST – Mechanical In-situ Stage with Temperature control for X-ray computed tomography

X-ray Computed Tomography (CT) in combination with a tensile/compression stage can deliver great insights in the damage mechanisms of a material. As the material properties change at low and high temperatures, materials may perform differently as they do at room temperature. In this paper, a novel Mechanical In-situ Stage with Temperature control (MIST) for the usage in laboratory CT devices for high resolution - (3 μm)³ - acquisitions is presented. Since the specimen temperature is controlled by air flow, the MIST stage is suitable for testing polymers and allows cooling and heating in one test cycle (-10 °C to +100 °C). The MIST stage is a modification of the CT500 DEBEN tensile/compression stage. It enables mechanical tests that combine the application of force and temperature on a sample at the same time. A technical description of the developed stage is presented. Furthermore, its advantages compared to existing devices are explored and application fields of the MIST are shown.

Traceability and quality assessment of Norway spruce (Picea abies (L.) H.Karst.) logs: the TreeTrace_spruce database

Key messageThe TreeTrace_spruce database contains images and measurements of 100 Norway spruce (Picea abies (L.) H.Karst.) logs from Northeastern France, each about 4.5 m long. The image database includes RGB images of large and small ends of the logs and hyperspectral and computed tomography (CT) images of wood discs sampled at both log ends. The 100 logs were also fully X-ray scanned with a CT device for roundwoods and their top surface was scanned with a terrestrial LiDAR device. The measurements performed on discs include wood local density, growth ring widths and pith location. This database is complementary to another one (TreeTrace_Douglas) resulting from the same ANR project TreeTrace, but if the objectives are similar, the protocols and conditions of acquisition are not the same for these two databases. TreeTrace_spruce dataset is available at https://doi.org/10.57745/WKLTJI and associated metadata are available at https://metadata-afs.nancy.inra.fr/geonetwork/srv/fre/catalog.search#/metadata/cffee2f1-18e1-4b53-9f5b-6cc4c66f1cb8.

OPTIMISING THE PARAMETERS OF COCHLEAR IMPLANT IMAGING WITH CONE-BEAM COMPUTED TOMOGRAPHY.

With computed tomography (CT), the delicate structures of the inner ear may be hard to visualise, which a cochlear implant (CI) electrode array can further complicate. The usefulness of a novel cone-beam CT device in CI recipient's inner ear imaging was evaluated and the exposure parameters were optimised to attain adequate clinical image quality at the lowest effective dose (ED). Six temporal bones were implanted with a Cochlear Slim Straight electrode array and imaged with six different imaging protocols. Contrast-to-noise ratio was calculated for each imaging protocol, and three observers evaluated independently the image quality of each imaging protocol and temporal bone. The overall image quality of the inner ear structures did not differ between the imaging protocols and the most relevant inner ear structures of CI recipient's inner ear can be visualised with a low ED. To visualise the most delicate structures in the inner ear, imaging protocols with higher radiation exposure may be required.

Evaluation of Environmental Radiation and Image Quality by Type of High-Energy Electromagnetic Wave Radiation Computed Tomography

With the enhancement of national income level, the number of computed tomography (CT) exams to diagnose diseases is increasing more and more. To utilize the data for the safety control of X-ray, the image quality of the environmental radiation at the boundaries in the radiation zone of the exam rooms by type of CT using highenergy electromagnetic wave. The locations of the environmental radiation measurement were shielding wall of the door for patients, door for patients, door to CT control room, shielding wall of the door for CT control room, and window to see the patients, and the glass dosimeters were installed 150 to 170 cm above the floor considering the location of the device to be measured for 3 months and analyzed. The environmental radiations in the MDCT room were measured with 3.09 ± 2.31 mSv, 0.51 ± 0.12 mSv, 0.99 ± 0.43 mSv, 0.27 ± 0.03 mSv, and 0.18 ± 0.03 mSv at the door to the control room, the wall of the control room, door for patients, door wall, and window to see the patients, respectively. In the mobile CT room, the radiation was detected only at the door of the control room with 1.65 ± 0.15 mSv, and no radiation was detected at the other boundaries. In the PET-CT room, the radiations were detected with 0.18 ± 0.03 mSv and 0.27 ± 0.03 mSv at the door and door wall, respectively, without detection at the other boundaries. Upon the results of image quality by CT devices, very satisfactory outcomes were found in terms of contrast, clarity of the boundaries, and detection rate of lesions in all the acquired images, and also very satisfactory in the functional evaluations of the organs in PET-CT only. These results are anticipated to be used as the reference data to establish the systemic and efficient systems and policies in the safety control of X-ray in the future.

Calibration of 3D scan trajectories for an industrial computed tomography setup with 6-DOF object manipulator system using a single sphere

In industrial x-ray computed tomography (CT), the application of more complex scan paths in comparison to the typical circular trajectory ( rotation of the measurement object) can extend the potential of CT. One way to enable such 3D scan trajectories is to use a 6-degrees-of-freedom (DOF) object manipulator system. In our case, a hexapod is mounted on top of the rotary table of a commercial CT scanner. This allows for adaptive tilting of the measurement object during the scan. For high accuracy, the geometry calibration of such setups is typically done using the x-ray projections of a calibrated multi-sphere object. Contrary to this, here, we demonstrate a procedure that is based on only a single sphere and can therefore experimentally be implemented with low effort. Using the intrinsic geometry parameters of the CT device as prior information, the hexapod coordinate system with respect to the CT machine coordinate system is determined by means of a one-step optimization approach. The resulting parameters are used to calculate projection matrices that enable the volume reconstruction for 3D scan trajectories. The method is validated using simulated x-ray images and experimental investigations including dimensional measurements. For the used setup, geometric measurement results for 3D scan trajectories that are calibrated with the presented method show in sum increased errors compared to the circular scans. A limited pose accuracy of the manipulator system is discussed as a potential cause. The results nevertheless indicate that the presented method is generally feasible for dimensional CT measurements provided that the pose accuracy is sufficient. The calibration procedure can therefore be a low-cost and easier to implement alternative compared to trajectory calibration methods based on multi-sphere objects, but with a tendency towards lower measurement accuracy. The methodology can in principle be transferred to different setups with 6-DOF manipulator systems, e.g. C-arm CT devices with a robot arm.

A novel dual-energy cone beam computed tomography device for assessment of jaw bone density

<h3>Objective</h3> To evaluate a novel dual-energy cone beam computed tomography (DE-CBCT) device for jaw bone density assessment. <h3>Study Design</h3> An ongoing clinical trial has enrolled 19 subjects with a target enrollment of 24 subjects. All subjects were 21 years and older and required a maxillofacial CT scan for standard-of-care diagnosis. Each subject received 2 examinations: one with a 64-slice multi-detector CT (MDCT) scanner and the second with the experimental DE-CBCT device (RCT720, Ray Co. Seoul, Korea). Asynchronous scanning of a custom hydroxyapatite phantom (concentrations of 0.8, 1.0 and 1.2 g/cc) provided calibration for bone density measurement. DICOM data from both CT examinations were imported into a custom version of OnDemand software<i>.</i> Calibration curves were generated from the MDCT and DE-CBCT scans of the hydroxyapatite phantoms. The MDCT and DE-CBCT scans of study subjects were superimposed and custom tools allowed calculation of bone density within a specified region of interest (ROI). Concordance between the MDCT- and DE-CBCT-derived bone densities was examined. <h3>Results</h3> In our preliminary assessments of data from current subjects, the mean calculated bone density in all the ROIs measured was 0.51 ± 0.27 g/cc for MDCT imaging and 0.50 ± 0.32 for DE-CBCT imaging. The range of the calculated bone densities was 0.06 to 1.1 g/cc for MDCT and 0.04 to 1.3 g/cc for DE-CBCT. Overall, there was strong correlation between bone densities calculated from MDCT scans with those calculated from DE-CBCT scans (r = 0.96, p <0.0001). Bland-Altman analysis identified a bias of 0.01 ± 0.1, and 95% limits of agreement range was -0.19 to 0.21. <h3>Conclusion</h3> The RCT720, a newly-developed DE-CBCT device, produced measurement of bone density equivalent to MDCT and overcomes the inaccuracies of bone density assessment using conventional CBCT scans. <b>Statement of Ethical Review</b> Human/Animal subjects were used and this study was approved by an institutional ethics panel

In vitro assessment of a novel dual-energy cone beam computed tomography device

<h3>Objective</h3> CT attenuation depends on atomic number and physical density of the object. Dual energy systems use two energy spectra and attenuation data from two different exposure conditions to estimate the effect of photoelectric absorption and Compton scatter in generating CT numbers. Based on this principle, a dual energy cone beam CT device (DE-CBCT, RCT-270, Ray Co. Ltd., Korea) was developed to assess jaw bone density and overcome limitations of gray level inhomogeneity in CBCT. <h3>Study Design</h3> We used a human skull phantom and varying concentrations of dipotassium phosphate (K₂HPO₄) to simulate trabecular and cortical bone. 0.2 ml polypropylene tubes with K₂HPO₄ (600mg/ml and 800mg/ml) were placed in empty sockets of the phantom at 3 discrete mandibular sites and scans were acquired. Next, to simulate temporal changes, we used varying concentrations of K₂HPO₄ (400 mg/ml-1200 mg/ml) in the extraction socket of a mandibular second premolar. All scans were made using the Rayscan DE-CBCT unit and repeated thrice. After each scan, the QRM-DE-CBCT phantom was also scanned with the same exposure factors for calibration. Scan calibration and bone density assessments were performed using the vendor's software. <h3>Results</h3> Calculated density of the same K₂HPO₄ placed at different locations (891± 144, 768 ± 29, 541 ± 126) was not statistically different. A similar result was obtained with K₂HPO₄ of higher density (1299 ± 58, 1203 ± 74, 998 ± 125). While simulating changing bone density, increasing concentrations of K₂HPO₄ yielded higher calculated densities, with a linear relationship between K₂HPO₄ concentrations and DE-CBCT calculated density (r² = 0.88). <h3>Conclusion</h3> This study provides an initial assessment of DE-CBCT as a method to better estimate object density which can impact monitoring osseous healing, evaluation of potential implant sites, and augmentation threshold for image segmentation. In ongoing studies, we are characterizing image quality parameters and further assessing the impact of anatomic location. <b>Statement of Ethical Review</b> Ethical Review or exemption was not warranted for this study

Phantom and Animal Study of a Robot-Assisted, CT-Guided Targeting System using Image-Only Navigation for Stereotactic Needle Insertion without Positional Sensors

PurposeTo evaluate the feasibility and accuracy of a robotic system to integrate and map computed tomography (CT) and robotic coordinates, followed by automatic trajectory execution by a robotic arm. The system was hypothesized to achieve a targeting error of <5 mm without significant influence from variations in angulation or depth. Materials and MethodsAn experimental study was conducted using a robotic system (Automated Needle Targeting device for CT [ANT-C]) for needle insertions into a phantom model on both moving patient table and moving gantry CT scanners. Eight spherical markers were registered as targets for 90 insertions at different trajectories. After a single ANT-C registration, the closed-loop software targeted multiple markers via the insertion of robotically aligned 18-gauge needles. Accuracy (distance from the needle tip to the target) was assessed by postinsertion CT scans. Similar procedures were repeated to guide 10 needle insertions into a porcine lung. A regression analysis was performed to test the effect of needle angulation and insertion depth on the accuracy of insertion. ResultsIn the phantom model, all needle insertions (median trajectory depth, 64.8 mm; range, 46.1–153 mm) were successfully performed in single attempts. The overall accuracy was 1.36 mm ± 0.53, which did not differ between the 2 types of CT scanners (1.39 mm ± 0.54 [moving patient table CT] vs 1.33 mm ± 0.52 [moving gantry CT]; P = .54) and was not significantly affected by the needle angulation and insertion depth. The accuracy for the porcine model was 9.09 mm ± 4.21. ConclusionsRobot-assisted needle insertion using the ANT-C robotic device was feasible and accurate for targeting multiple markers in a phantom model.

Morphometric Evaluation of Coccyx with Microcomputed Tomography (Micro CT) and Computed Tomography (CT) Technology

Aim: We investigated the coccyx anatomy accurately in detail by microcomputed tomography (micro CT) and computed tomography (CT) to contribute to the data related to the coccyx anatomy and the potential clinical contribution of these datas in the treatment of coccyx’s pathologies. Material and Methods: Twenty coccyges from embalmed cadavers were examined with a micro CT device. The inferior part of the sacrum and coccyx together with the surrounding soft tissue was removed safely. The tissue was scanned with a micro CT device, and all parameters were measured with micro CT image viewer programs. CT images of 29 patients without coccyx pathology were measured with OsiriX programs. Measured morphometric parameters with micro CT and CT were evaluated using statistical methods. Results: Generally, the morphometric parameters as mean values were larger in males than in females. Mean values for vertical length and coccyx width were higher for CT compared with micro CT images. Coccyx was more flat in the frontal plane in females. There were statistically significant differences between the micro CT and CT images regarding mean vertical length, width, lateral deviation angle, and sacrococcygeal angle and length of the vertebrae (p < 0.05). There were no statistically significant differences in number and width of the vertebrae (p > 0.05). Conclusion: We suggest that examining the normal coccyx morphology will help to better understand and treat the pathologic conditions of the coccyx. We believe our findings will contribute to the data related to the coccyx anatomy.

Intraoperative mobile computed tomography in deep brain stimulation: Comparison between Airo CT and O-arm CT.

Background: A new intraoperative mobile device, called Airo computed tomography (CT), is becoming increasingly used in surgery adding to the current most widespread intraoperative imaging in form of the O-arm CT device. Intraoperative CT imaging has the advantage to reduce the discomfort derived from the patient’s transfer from the operative room to the radiological unit and also the time of control or time of reposition in cases of lead misplacement. This is the first rapport on Airo CT device application in DBS surgery.Methods: In our retrospective study, we have evaluated 52 patients who had DBS from October 2020 to November 2021. All patients underwent a preoperative brain magnetic resonance imaging (MRI) and a stereotactic brain CT scan. We performed an intraoperative CT scan with the Airo device. Images were subsequently transferred to the neuronavigation system (BrainLab cranial software) and merged with preoperative planning images to confirm correct position of leads. Five aspects were compared: patient and surgeon comfort, surgical planning, parenchymal visualization, radioscopic lead visualization, and costs.Results: Both imaging devices are easy-to-use, precise, and safe and have their pros and cons.Conclusion: This is the first study reporting on CT-Airo application in DBS. We advise that if only DBS is considered, the O-arm application might be more suitable. If in addition to DBS cranial surgery is performed, the Airo device is more suitable.

Hardware Optimizations of the X-ray Pre-Processing for Interventional Computed Tomography Using the FPGA

In computed tomography imaging, the computationally intensive tasks are the pre-processing of 2D detector data to generate total attenuation or line integral projections and the reconstruction of the 3D volume from the projections. This paper proposes the optimization of the X-ray pre-processing to compute total attenuation projections by avoiding the intermediate step to convert detector data to intensity images. In addition, to fulfill the real-time requirements, we design a configurable hardware architecture for data acquisition systems on FPGAs, with the goal to have a “on-the-fly” pre-processing of 2D projections. Finally, this architecture was configured for exploring and analyzing different arithmetic representations, such as floating-point and fixed-point data formats. This design space exploration has allowed us to find the best representation and data format that minimize execution time and hardware costs, while not affecting image quality. Furthermore, the proposed architecture was integrated in an open-interface computed tomography device, used for evaluating the image quality of the pre-processed 2D projections and the reconstructed 3D volume. By comparing the proposed solution with the state-of-the-art pre-processing algorithm that make use of intensity images, the latency was decreased 4.125×, and the resources utilization of ∼6.5×, with a mean square error in the order of 10−15 for all the selected phantom experiments. Finally, by using the fixed-point representation in the different data precisions, the latency and the resource utilization were further decreased, and a mean square error in the order of 10−1 was reached.

Mesoscopic damage mechanism and a constitutive model of shale using in-situ X-ray CT device

With the continuous development of shale gas engineering in China, an accurate and adequate understanding of shale damage mechanism has become a critical scientific problem addressed by rock mechanics. So far, many researchers have studied the fracturing process and mechanism of shale in multi-scales. The mesoscopic structural characteristics of shale during loading can be obtained using the in-situ X-ray computed tomography (CT) technology. Some scholars have observed the structure evolution of shale under in-situ uniaxial compression conditions, but the quantitative investigation of damage evolution and constitutive model of shale still requires further studies. Given this, the in-situ micro-CT device was adopted to study the macroscopic mechanical response and the mesoscopic structural evolution of Longmaxi shale under uniaxial compression conditions. The evolution law of the damage variable with the axial strain was analysed according to the characterisation of the damage variable based on the CT image grey variance. In combination with the macroscopic stress-strain curve shape, evolution stage of the mesoscopic void, evolution of the damage variable, mesoscopic mechanism of the macroscopic mechanical response was investigated, and a damage constitutive model of shale under the uniaxial compression test was proposed. The conclusion of this study can provide a foundation for further research into the multi-scale failure mechanism of shale and exert theoretical guidance significance on shale gas fracturing engineering practice.

PIMA-CT: Physical Model-Aware Cyclic Simulation and Denoising for Ultra-Low-Dose CT Restoration.

A body of studies has proposed to obtain high-quality images from low-dose and noisy Computed Tomography (CT) scans for radiation reduction. However, these studies are designed for population-level data without considering the variation in CT devices and individuals, limiting the current approaches' performance, especially for ultra-low-dose CT imaging. Here, we proposed PIMA-CT, a physical anthropomorphic phantom model integrating an unsupervised learning framework, using a novel deep learning technique called Cyclic Simulation and Denoising (CSD), to address these limitations. We first acquired paired low-dose and standard-dose CT scans of the phantom and then developed two generative neural networks: noise simulator and denoiser. The simulator extracts real low-dose noise and tissue features from two separate image spaces (e.g., low-dose phantom model scans and standard-dose patient scans) into a unified feature space. Meanwhile, the denoiser provides feedback to the simulator on the quality of the generated noise. In this way, the simulator and denoiser cyclically interact to optimize network learning and ease the denoiser to simultaneously remove noise and restore tissue features. We thoroughly evaluate our method for removing both real low-dose noise and Gaussian simulated low-dose noise. The results show that CSD outperforms one of the state-of-the-art denoising algorithms without using any labeled data (actual patients' low-dose CT scans) nor simulated low-dose CT scans. This study may shed light on incorporating physical models in medical imaging, especially for ultra-low level dose CT scans restoration.