Ultrafast CT Research Articles

XTransCT: ultra-fast volumetric CT reconstruction using two orthogonal x-ray projections for image-guided radiation therapy via a transformer network

Objective. The aim of this study was to reconstruct volumetric computed tomography (CT) images in real-time from ultra-sparse two-dimensional x-ray projections, facilitating easier navigation and positioning during image-guided radiation therapy. Approach. Our approach leverages a voxel-sapce-searching Transformer model to overcome the limitations of conventional CT reconstruction techniques, which require extensive x-ray projections and lead to high radiation doses and equipment constraints. Main results. The proposed XTransCT algorithm demonstrated superior performance in terms of image quality, structural accuracy, and generalizability across different datasets, including a hospital set of 50 patients, the large-scale public LIDC-IDRI dataset, and the LNDb dataset for cross-validation. Notably, the algorithm achieved an approximately 300% improvement in reconstruction speed, with a rate of 44 ms per 3D image reconstruction compared to former 3D convolution-based methods. Significance. The XTransCT architecture has the potential to impact clinical practice by providing high-quality CT images faster and with substantially reduced radiation exposure for patients. The model's generalizability suggests it has the potential applicable in various healthcare settings.

3-D shape and velocity measurement of argon gas bubbles rising in liquid sodium by means of ultrafast X-ray CT imaging

We present an evaluation study on the characterization of bubbles rising in liquid sodium by applying two-plane ultrafast X-ray computed tomography (UFXCT). It includes a new method for determining the three-dimensional shape and velocity vector of each individual bubble. In the experimental part, argon gas was injected through a single nozzle located slightly above the bottom of a cylindrical vessel filled with liquid sodium. The gas flow rate was varied between 10 and 635 cm3/min to obtain a chain of individual bubbles. In this parameter range, collisions of bubbles, coalescence or breakup are not expected. Measurements were carried out in a wide spatial range starting near the nozzle up to a height of about 200 mm above it. It was convincingly demonstrated that two-plane UFXCT imaging, in combination with the data processing presented here, allows a reliable characterization of the size, shape and velocity of bubbles with a size of a few millimeters in a sodium column of 54 mm diameter. Moreover, a reproducible fluctuation of shape, position and velocity has been observed in the experiments in the lower part of the column.

A deep learning method for high-quality ultra-fast CT image reconstruction from sparsely sampled projections

Few-view or sparse-view computed tomography has been recently introduced as a great potential to speed up data acquisition and alleviate the amount of patient radiation dose. This study aims to present a method for high-quality ultra-fast image reconstruction from sparsely sampled projections to overcome problems of previous methods, missing and blurring tissue boundaries, low-contrast objects, variations in shape and texture between the images of different individuals, and their outcomes. To this end, a new deep learning (DL) framework based on convolution neural network (CNN) models is proposed to solve the problem of CT reconstruction under sparsely sampled data, named the multi-receptive field densely connected CNN (MRDC-CNN). MRDC-CNN benefits from an encoder–decoder structure by proposing dense skip connections to recover the missing information, multi-receptive field modules to enlarge the receptive field, and having no batch normalization layers to boost the performance. The MRDC-CNN with a hybrid loss function format introduces several auxiliary losses combined with the main loss to accelerate convergence rate and alleviate the gradient vanishing problem during network training and maximize its performance. Results have shown that MRDC-CNN is 4–6times faster than the state-of-the-art methods, with fewer memory requirements, better performance in objective quality evaluations, and improved visual quality. The results indicated the superiority of our proposed method compared to the latest algorithms. In conclusion, the proposed method could lead to high-quality CT imaging with quicker imaging speed and lower radiation dose. The source code is available on a GitHub repository at this link.

High-resolution CT with arch/neck/head CT angiography on a mobile stroke unit

BackgroundMobile stroke units (MSUs) performance dependability and diagnostic yield of 16-slice, ultra-fast CT with auto-injection angiography (CTA) of the aortic arch/neck/circle of Willis has not been previously reported.MethodsWe performed a...

Bronchogenic carcinoma: Correlation of CT findings with the surgical and histopathological findings

CT and HRCT how largely replaced radiological procedures such has bronchography and pulmonary angiography for evolution of parenchyma lung diseases. HRCT has enabled the delineation of lung parenchyma down to the level of secondary pulmonary lobule (Mayo R et al., 1987). Further advancement in CT Technologies by spiral CT and ultra fast CT have still consolidated the role of CT in evolution thoracic diseases. Spiral CT facilitate generation of 3D images of lung that or not degraded by respiratory motion and is much faster at acquisition time ensuring evaluation of lung during maximum vascular enhancements. In this study CT evaluation of 50 patients with either proven or strongly suspected bronchogenic carcicnoma based on chest radiographs, bronchoscopy, cytology of bronchial washings or pleural fluid, FNAC or clinical examination was done. The most common cell type in bronchogenic carcinoma was squamous cell carcinoma in 33 patient (66%) followed by adenocarcinoma Majority of the adenocarcinoma cell type are presenting as central masses than peripheral (18% v/s 6%).

P1290RISK FACTORS FOR PROGRESSION OF CORONARY ARTERY CALCIFICATION OVER 5 YEARS IN HEMODIALYSIS PATIENTS

Abstract Background Although progression of coronary artery calcification (CAC) has been established as an important marker for cardiovascular morbidity, very few studies have studied it in end-stage renal disease patients. Thus we examined and evaluate risk factors of calcification changes in dialysis patients. Method Among 28 hemodialysis (HD) patients, CAC was measured in Agatston units at baseline and after five years using the 64 multi-slice ultra-fast CT. The HD patients were classified as progressors or no progressors according to the change in the CAC score across these 2 measurements. Results Over an average 63 months follow-up, participants without CAC at baseline had no incident CAC .The progression of CAC was slow and was found only in 6 patients (21.4%) . It was significantly associated with several cardiovascular risk factors, namely, older age (p=0.03), diabetes (p=0.05), male sex (p=0.02), hypercholesterolemia (p = 0.05), anemia (p=0.017), inflammation (p=0.05), and hyperphosphataemia (p=0.012) . However, calcemia, parathormone levels, dialysis duration, tobacco, high blood pressure and dialysis dose did not seem to influence the progression of CAC in our series. A strong association was found between basal calcification scores and Delta increment at 5 years. Conclusions Our study suggests that CAC progression in dialysis is a complex phenomenon, associated with several risk factors with special regard to elevated basal scores. This progression can be avoided or slowed with appropriate management which must begin in the early stages of chronic kidney disease

Facteurs de risque de progression des calcifications des artères coronaires après 5 ans d’évolution en dialyse

BackgroundAlthough progression of coronary artery calcification (CAC) has been established as an important marker for cardiovascular morbidity, very few studies have studied it in end-stage renal disease patients. Thus we examined and evaluate risk factors of calcification changes in dialysis patients. MethodAmong 28 hemodialysis (HD) patients, CAC was measured in Agatston units at baseline and after five years using the 64 multi-slice ultra-fast CT. The HD patients were classified as progressors or no progressors according to the change in the CAC score across these 2 measurements. ResultsOver an average 63 months follow-up, participants without CAC at baseline had no incident CAC. The progression of CAC was slow and was found only in 6 patients (21.4%). It was significantly associated with several cardiovascular risk factors, namely, older age (P=0.03), diabetes (P=0.05), male sex (P=0.02), hypercholesterolemia (P=0.05), anemia (P=0.017), inflammation (P=0.05), and hyperphosphataemia (P=0.012). However, calcemia, parathormone levels, dialysis duration, tobacco, high blood pressure and dialysis dose did not seem to influence the progression of CAC in our series. A strong association was found between basal calcification scores and Delta increment at 5 years. ConclusionsOur study suggests that CAC progression in dialysis is a complex phenomenon, associated with several risk factors with special regard to elevated basal scores. This progression can be avoided or slowed with appropriate management, which must begin in the early stages of chronic kidney disease.

Peripheral Vascular Anomalies - Essentials in Periinterventional Imaging.

Peripheral vascular anomalies represent a rare disease with an underlying congenital mesenchymal and angiogenetic disorder. Vascular anomalies are subdivided into vascular tumors and vascular malformations. Both entities include characteristic features and flow dynamics. Symptoms can occur in infancy and adulthood. Vascular anomalies may be accompanied by characteristic clinical findings which facilitate disease classification. The role of periinterventional imaging is to confirm the clinically suspected diagnosis, taking into account the extent and location of the vascular anomaly for the purpose of treatment planning. In accordance with the International Society for the Study of Vascular Anomalies (ISSVA), vascular anomalies are mainly categorized as slow-flow and fast-flow lesions. Based on the diagnosis and flow dynamics of the vascular anomaly, the recommended periinterventional imaging is described, ranging from ultrasonography and plain radiography to dedicated ultrafast CT and MRI protocols, percutaneous phlebography and transcatheter angiography. Each vascular anomaly requires dedicated imaging. Differentiation between slow-flow and fast-flow vascular anomalies facilitates selection of the appropriate imaging modality or a combination of diagnostic tools. Slow-flow congenital vascular anomalies mainly include venous and lymphatic or combined malformations. Ultrasound and MRI and especially MR-venography are essential for periinterventional imaging. Arteriovenous malformations are fast-flow vascular anomalies. They should be imaged with dedicated MR protocols, especially when extensive. CT with 4D perfusion imaging as well as time-resolved 3D MR-A allow multiplanar perfusion-based assessment of the multiple arterial inflow and venous drainage vessels of arterio-venous malformations. These imaging tools should be subject to intervention planning, as they can reduce procedure time significantly. Fast-flow vascular tumors like hemangiomas should be worked up with ultrasound, including color-coded duplex sonography, MRI and transcatheter angiography in case of a therapeutic approach. In combined malformation syndromes, radiological imaging has to be adapted according to the dominant underlying vessels and their flow dynamics. Guide to evaluation of flow dynamics in peripheral vascular anomalies, involving vascular malformations and vascular tumors with the intention to facilitate selection of periinterventional imaging modalities and diagnostic and therapeutic approach to vascular anomalies. · Peripheral vascular anomalies include vascular malformations and vascular tumors. Both entities represent a rare disease with an underlying congenital mesenchymal or angiogenetic disorder. · The role of periinterventional imaging is confirmation ofthe diagnosis by assessing the flow dynamics of the vascular anomaly. · Slow-flow congenital vascular anomalies include venous, lymphatic and venolymphatic malformations. Arteriovenous malformations are fast-flow vascular anomalies, whereas hemangiomas are fast-flow vascular tumors that are frequently associated with fast-flow arteriovenous shunts. The periinterventional imaging modalities of choice include dedicated MR protocols and CT with 4D perfusion imaging as well as invasive transcatheter angiography.. · Sadick M, Overhoff D, Baessler B et al. Peripheral Vascular Anomalies - Essentials in Periinterventional Imaging. Fortschr Röntgenstr 2020; 192: 150 - 162.

Pharyngeal distensibility during expiration is an independent predictor of the severity of obstructive sleep apnoea.

Pharyngeal distensibility and collapsibility reflect the passive properties of tissue in the airway, are an indicator of the ease with which an airway can be deformed and are related to the severity of obstructive sleep apnoea (OSA). During normal tidal respiration, the collapsibility of the pharynx during expiration is passive without confounding by neuromuscular activation that occurs during inspiration. We evaluated the distensibility and collapsibility of the upper airway in subjects with OSA during wakefulness using sophisticated dynamic computed tomography (CT) imaging. We hypothesized that the dynamic changes of the upper airway during expiration would be related to the severity of OSA. Twenty-three patients with OSA and eight normal subjects underwent simultaneous measurement of respiratory flow and airway calibre using ultrafast CT. The change in pharyngeal cross-sectional area divided by the change in concomitant flow (as distensibility or collapsibility) was measured and compared across different severities of OSA. The slope of this relationship between delta area and delta flow during expiration was significantly higher in severe OSA when compared with normal controls and mild-moderate OSA. Differences in airway distensibility or collapsibility between severity groups were significant in expiration but not in inspiration. Distensibility or collapsibility contributed most to the apnoea-hypopnoea index in regression modelling. Age, gender, and body mass index (BMI) were not significant independent predictors. Our study demonstrates that airway distensibility during the expiratory phase of awake respiration is correlated with the severity of OSA.

Development of LSI for a new kind of photon-counting computed tomography using multipixel photon counters

X-ray imaging with computed tomography (CT) is widely used for nondestructive imaging of the interior of the human body. In the next decade, photon-counting X-ray CT is expected to reduce the dose needed and enable multicolor imaging. Recently, we proposed a novel photon-counting method that uses a multipixel photon counter (MPPC), with a significantly high signal gain (∼106) and fast temporal response (a few nanoseconds), combined with a high-speed scintillator. To realize photon-counting CT imaging in a wide area irradiated by an extremely high X-ray flux (106-107 Hz/mm2), a multichannel MPPC system is required. Thus, we developed a large-scale integrated circuit (LSI) with ultrafast signal-processing capability for use with a 16-channel MPPC. The developed LSI can extract a pulse current from an MPPC array with a large detector capacitance (∼200 pF) by utilizing an electrical circuit with low input impedance. The LSI offers a high photon count rate above 25 MHz/pixel with noise equal to 1.7 μA for a dynamic range of ∼ 1.3 mA and an energy resolution of 32 % (FWHM) at 60 keV, thereby enabling ultrafast multicolor CT imaging.

Study of Flow Behavior of Granular Material Inside Cylindrical Silo Using Ultrafast X-Ray Imaging Technique

AbstractThis paper presents an application of an ultrafast electron beam X-ray CT scanner for investigating the gravitational flow behavior of granulates through cylindrical silo model. The CT scanner allows obtaining crosssectional images of the granular material distribution with a spatial resolution of approximately 1 mm and a time resolution of 2 kHz. In order to conduct a deep analysis of the granular flow concentration changes, two image processing algorithm steps were applied. The first step deals with preprocessing and re-centering stacks of raw images. The second step divides the preprocessed image into several concentric rings and calculates the mean value to study radial concentration changes. Independent analysis of granular concentration in each ring provides useful knowledge to study the silo discharging during mass flow and funnel flow.

Role of 256 slice CT scan in pre and postoperative evaluation of congenital cardio-vascular anomalies: our experience at a tertiary care teaching hospital

Background: Ultrafast CT (UCT) scan plays an important role in the evaluation of congenital cardiovascular anomalies (CCVA). A major advantage of higher slice multi-detector CT (MDCT), is improved temporal as well as spatial resolution, that helps accurately to delineate complex cardiac and extra-cardiac anomalies with relative ease. Hence this study was aimed to highlight the utility of UCT in the evaluation of congenital cardiovascular anomalies in a large series of patients.Methods: All consecutive patients with suspected CCVA were evaluated by cardiac CT angiography (CCTA) on 256 slice CT scan in a multispecialty tertiary care teaching institute from June 2013 to December2015.Results: A total of 160 cases of CCVA were evaluated by CCTA. 50 patients had multiple anomalies. A total of 216 anomalies were diagnosed. Tetralogy of fallot (TOF) dominated the list of CCVAs (60, 28%) than the other abnormalities. Of them, 25 patients underwent Blalock Taussig (BT) shunt surgeries, 20 patients underwent total repair operation like Rastelli’s operation or augmentation of pulmonary arteries (PAs) while 15 patients were lost to follow up. Most of the patients diagnosed with CCVAs were managed successfully based on the imaging diagnosis of the cardiovascular anomaly.Conclusions: Ultrafast CT scans have immense role in the evaluation of various types of congenital cardiovascular anomalies. It is particularly helpful in the evaluation of extra-cardiac systemic and pulmonary arterial and venous system, postoperative complications, to see the status of shunts, stents and conduits.

Ultra-fast spin-mixing in a diketopyrrolopyrrole monomer/fullerene blend charge transfer state

Transient absorption and time-resolved EPR spectroscopy show an ultra-fast spin-mixing CT state in a small diketopyrrolopyrrole-based molecule blended with fullerene.

Data processing performance analysis for ultrafast electron beam X-ray CT using parallel processing hardware architectures

The ultrafast electron beam X-ray computed tomography (CT) measuring system of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) is primarily operated for fundamental multiphase flow investigations, e.g. in various technical devices, and for validation of enhanced flow simulation models, e.g. developed for computational fluid dynamic codes (CFD). The CT scanner delivers cross-sectional material distributions by contactless measurements with a spatial resolution of approximately 1mm and a temporal resolution of maximal 8kHz. Currently, two central time-consuming processes have been identified limiting the efficient usage of that worldwide unique CT technique: a) the data transfer from the detector system to central data storages (e.g. computer or data base) and b) the data processing. Thus, data pre-processing and data reconstruction algorithms have been adapted for the use at multi-core central processing units (CPUs) and even many-core graphics processing units (GPUs). For optimal data processing results an advanced performance PC with two parallel operated high performance graphics processing units, a six-core processor, a high internal data bus speed and a large memory block has been assembled. The newly developed data processing algorithms induce a performance improvement of approximately 137 for the entire data processing sequence compared to the previous universally applicable single core CPU based data processing tool.

Combined phase distribution and particle velocity measurement in spout fluidized beds by ultrafast X-ray computed tomography

The spout fluidized bed is a very successful combination of spouted and fluidized bed, which is most interesting for processing particles with larger or varying diameter. However, the more complex hydrodynamics of the combined configuration is yet not fully understood. Here, we propose the application of ultrafast X-ray computed tomography (CT), which has proven to be a valuable measurement technique for the analysis of highly dynamic processes, for example multiphase flows. It is able to resolve material distributions with up to 8000 frames per second and a spatial resolution down to 1mm. Especially for opaque systems, such as fluidized beds, ultrafast X-ray CT can reveal details, which are not recoverable by e.g. optical measurement techniques. Besides the recovering of the dynamic phase distribution, determining local particle velocities is essential to understand the complex flow in fluidized beds. As we will demonstrate here for the first time, this is possible via a dual-plane ultrafast X-ray CT by using suitable marker particles. In this article, the methodology for determining particle velocities under highly dynamic conditions within a cylindrical spout fluidized bed is presented. Complementary analysis techniques for different flow conditions have been combined to increase confidence in the velocity data.

Scatter analysis and correction for ultrafast X-ray tomography.

Ultrafast X-ray computed tomography (CT) is an imaging technique with high potential for the investigation of the hydrodynamics in multiphase flows. For correct determination of the phase distribution of such flows, a high accuracy of the reconstructed image data is essential. In X-ray CT, radiation scatter may cause disturbing artefacts. As the scattering is not considered in standard reconstruction algorithms, additional methods are necessary to correct the detector readings or to prevent the detection of scattered photons. In this paper, we present an analysis of the scattering background for the ultrafast X-ray CT imaging system ROFEX at the Helmholtz-Zentrum Dresden-Rossendorf and propose a correction technique based on collimation and deterministic simulation of first-order scattering.

Dépistage et facteurs de risque des calcifications cardiaques chez l’hémodialysé : apport du scanner multi-coupe ultra-rapide et de l’échocardiographie transthoracique

IntroductionCardiovascular disease is the first leading cause of death in hemodialysis patients. In this population, cardiovascular calcifications occur at an earlier age and progress faster than in general population. Patients and methodsIn order to determine the prevalence and risk factors of cardiac calcifications, 49 patients on chronic hemodialysis were screened in the coronary arteries and cardiac valves by the 64 multi-slice ultra-fast CT and the transthoracic echocardiography. Different clinical and biological parameters were studied by the SPSS 10.0 statistical software to determine risk factors. ResultCardiac calcifications were identified in 81.6% of cases in at least one of the two studied sites. The coronary artery involvement was more common than valvular and concerned 69.4% of cases. The mean Agatston coronary artery calcium score (ACACS) was 331.1 and 522.2 in coronary patients and was correlated to alteration of systolic function of LV (r=−0.287, P=0.045). The severity of CACS was positively correlated with age (r=0.332, P=0.02). Coronary calcifications were associated with cardiovascular risk common to those of the general population (age, male sex, systolic blood pressure, diabetes, history of ischemic heart disease), but also to a lesser quality of dialysis. Valvular calcifications were present in 49% of cases and were correlated with left ventricular hypertrophy (P=0.006). The exclusive involvement of the aortic valve was the most common valvular abnormality. Phosphocalcic and lipid parameters, levels of hemoglobin, CRP and uric acid did not predisposed to cardiac calcifications in our patients. DiscussionIn hemodialysis patients, the pathogenesis of cardiovascular calcification is complex and cannot be attributed to a passive process. This process involves several factors that can promote or inhibit calcification. The new multi-slice ultra-fast scanner is a very sensitive method for topographic and quantitative assessment of coronary calcification and is a better alternative to invasive techniques. ConclusionOur study confirms the high prevalence of cardiac calcification in hemodialysis, and highlights the importance of early screening and treatment of predisposing factors.

Ultrafast dynamic computed tomography myelography for the precise identification of high-flow cerebrospinal fluid leaks caused by spiculated spinal osteophytes.

Precise localization and understanding of the origin of spontaneous high-flow spinal CSF leaks is required prior to targeted treatment. This study demonstrates the utility of ultrafast dynamic CT myelography for the precise localization of high-flow CSF leaks caused by spiculated spinal osteophytes. This study reports a series of 14 patients with high-flow CSF leaks caused by spiculated spinal osteophytes who underwent ultrafast dynamic CT myelography between March 2009 and December 2010. There were 10 male and 4 female patients, with an average age of 49 years (range 37-74 years). The value of ultrafast dynamic CT myelography in depicting the CSF leak site was qualitatively assessed. In all 14 patients, ultrafast dynamic CT myelography was technically successful at precisely demonstrating the site of the CSF leak, the causative spiculated osteophyte piercing the dura, and the relationship of the implicated osteophyte to adjacent structures. Leak sites included 3 cervical, 11 thoracic, and 0 lumbar levels, with 86% of the leaks occurring from C-5 to T-7. Information obtained from the ultrafast dynamic CT myelogram was considered useful in all treated CSF leaks. Spinal osteophytes piercing the dura are a more frequent cause of high-flow CSF leaks than previously recognized. Ultrafast dynamic CT myelography adds value beyond standard dynamic myelography or digital subtraction myelography in the diagnosis and anatomical characterization of high-flow spinal CSF leaks caused by these osteophytes. This information allows for appropriate planning for percutaneous or surgical treatment.

Diagnostic and Interventional Radiology for Liver Diseases

Diagnostic and Interventional Radiology for Liver Diseases

Ultrafast Cone-Beam Computed Tomography: A Comparative Study of Imaging Protocols during Image-Guided Therapy Procedure

Objective. To evaluate two ultrafast cone-beam CT (UF-CBCT) imaging protocols with different acquisition and injection parameters regarding image quality and required contrast media during image-guided hepatic transarterial chemoembolization (TACE). Methods. In 80 patients (male: 46, female: 34; mean age: 56.8 years; range: 33–83) UF-CBCT was performed during TACE for intraprocedural guidance. Imaging was performed using two ultrafast CBCT acquisition protocols with different acquisition and injection parameters (imaging protocol 1: acquisition time 2.54 s, and contrast 6 mL with 3 s delay; imaging protocol 2: acquisition time 2.72 s, and contrast 7 mL with 6 s delay). Image evaluation was performed with both qualitative and quantitative methods. Contrast injection volume and dose parameters were compared using values from the literature. Results. Imaging protocol 2 provided significantly better (P < 0.05) image quality than protocol 1 at the cost of slightly higher contrast load and patient dose. Imaging protocol 1 provided good contrast perfusion but it mostly failed to delineate the tumors (P < 0.05). On the contrary, imaging protocol 2 showed excellent enhancement of hepatic parenchyma, tumor, and feeding vessels. Conclusion. Tumor delineation, visualization of hepatic parenchyma, and feeding vessels are clearly possible using imaging protocol 2 with ultrafast CBCT imaging. A reduction of required contrast volume and patient dose were achieved due to the ultrafast CBCT imaging.