CT Scanning Technique Research Articles

The influence of low concentration iodinated contrast agent and low-dose CT scanning technique combined with body mass index on radiation dose and image quality of upper abdominal CT examinations

Objective To investigate the influence of double technology (low concentration iodinated contrast agent and low-dose scan) combined with body mass index (BMI) on radiation dose and image quality of contrast-enhanced upper abdominal CT examination. Methods One hundred and twenty patients who received upper abdominal enhanced CT examination were randomly divided into 4 groups: group A1, the iodinated contrast agent iodixanol (270 mg/ml), BMI<18.5 kg/m2 and 80 kVp; group A2, the iodinated contrast agent iodixanol (270 mg/ml), 18.5 kg/m2≤BMI≤24.9 kg/m2 and 100 kVp; group B1, the iodinated contrast agent ioversol (320 mg/ml), <18.5 kg/m2 and 120 kVp; group B2, the iodinated contrast agent ioversol (320 mg/ml), 18.5 kg/m2≤BMI≤24.9 kg/m2 and 120 kVp. Image quality was subjectively scored, the objective parameters (noise, CT values of abdominal aorta and liver parenchyma, contrast noise ratio of abdominal aorta and liver parenchyma) were evaluated and radiation dose was recorded. The differences of the indexes between A1 and B1 groups, A2 and B2 groups were compared with Mann-Whitney U test and pared-samples t test. Results All CT images were good. No images with 4 scores were obtained. No significant difference was found between group A1 and B1, between group A2 and B2 (P>0.05). There was no significant difference in contrast noise ratio of liver parenchyma (P>0.05), while significant differences existed in CT values of abdominal aorta and liver parenchyma, contrast noise ratio of abdominal aorta between group A1 and B1 (P<0.05). Significant differences existed in the parameters above mentioned between group A2 and B2, respectively (P<0.05). Radiation dose was lower in group A1 than in group B1 and in group A2 than in group B2 (P<0.05), respectively. Radiation dose was decreased by 40.1%(0.89/2.22) in group A1 than group B1 while radiation dose decreased by 56.9% (3.02/5.31) in group A2 than group B2. Conclusion According to BMI, the low concentration iodinated contrast agent and low-dose scan CT scanning technology could effectively reduce radiation dose and generate ideal images during the contrast-enhanced upper abdominal CT examination. Key words: Tomography, X-ray computed; Radiation dosage; Contrast media; Body weight

Volume versus diameter assessment of small pulmonary nodules in CT lung cancer screening.

Currently, lung cancer screening by low-dose chest CT is implemented in the United States for high-risk persons. A disadvantage of lung cancer screening is the large number of small-to-intermediate sized lung nodules, detected in around 50% of all participants, the large majority being benign. Accurate estimation of nodule size and growth is essential in the classification of lung nodules. Currently, manual diameter measurements are the standard for lung cancer screening programs and routine clinical care. However, European screening studies using semi-automated volume measurements have shown higher accuracy and reproducibility compared to diameter measurements. In addition to this, with the optimization of CT scan techniques and reconstruction parameters, as well as advances in segmentation software, the accuracy of nodule volume measurement can be improved even further. The positive results of previous studies on volume and diameter measurements of lung nodules suggest that manual measurements of nodule diameter may be replaced by semi-automated volume measurements in the (near) future.

Cranial Morphology of the Late Oligocene Patagonian Notohippid Rhynchippus equinus Ameghino, 1897 (Mammalia, Notoungulata) with Emphases in Basicranial and Auditory Region.

“Notohippidae” is a probably paraphyletic family of medium sized notoungulates with complete dentition and early tendency to hypsodonty. They have been recorded from early Eocene to early Miocene, being particularly diverse by the late Oligocene. Although Rhynchippus equinus Ameghino is one of the most frequent notohippids in the fossil record, there are scarce data about cranial osteology other than the classical descriptions which date back to the early last century. In this context, we describe the exceptionally preserved specimen MPEF PV 695 (based on CT scanning technique and 3D reconstruction) with the aim of improving our knowledge of the species, especially regarding auditory region (petrosal, tympanic and surrounding elements), sphenoidal and occipital complexes. Besides a modular description of the whole skull, osteological correlates identified on the basicranium are used to infer some soft-tissue elements, especially those associated with vessels that supply the head, mainly intracranially. One of the most informative elements was the petrosal bone, whose general morphology matches that expected for a toxodont. The endocranial surface, together with the surrounding parietal, basisphenoid, occipital, and squamosal, enabled us to propose the location and communication of main venous sinuses of the lateral head wall (temporal, inferior and sigmoid sinuses), whereas the tympanic aspect and the identification of a posterior carotid artery canal provided strong evidence in support of an intratympanic course of the internal carotid artery, a controversial issue among notoungulates. Regarding the arrangement of tympanic and paratympanic spaces, the preservation of the specimen allowed us to appreciate the three connected spaces that constitute a heavily pneumatized middle ear; the epitympanic sinus, the tympanic cavity itself, and the ventral expansion of the tympanic cavity through the notably inflated bullae. We hope this study stimulates further inquires and provides potentially informative data for future research involving other representatives of the order.

An Experimental Study on the Gas Entrainment in Horizontally and Vertically Installed Centrifugal Pumps

In this work, we have studied how gas accumulates in an industrial centrifugal pump under various steady-state two-phase flow conditions. Thereby, we considered both horizontal and vertical pump installation positions. Phase fractions within the impeller region of the pump have been quantitatively disclosed using high-resolution gamma-ray computed tomography (HireCT) and applying time-averaged rotation-synchronized CT scanning technique. The study was made for inlet volumetric gas flow rates between 0% and 5%. To account for different inlet flow conditions, which are assumed to occur during unwanted gas entrainment by hollow vortices, we produced disperse and swirling gas–liquid inlet flows. In this way, the influence of inlet flow boundary conditions on the pump performance as well as gas fraction distributions and gas holdup within the impeller wheel region could be successfully analyzed and compared with respect to the impeller alignment. It was shown that the installation position offers only a minor effect on the pump performance in comparison to the inlet flow conditions. In addition, for the first time, thin gas films at the pressure side of the impeller wheel blades could be visualized in an industrial centrifugal pump.

Helium permeability of polymer materials as liners for composite overwrapped pressure vessels

ABSTRACTPolymers have been identified as replacement materials for metallic liners in composite overwrapped pressure vessels (COPVs) for future space launchers. PEEK, Nylon, and PVDF plastics formed from base powder grades have been permeability tested to determine their susceptibility to the diffusion of helium through flatwise panel cross sections. Permeability, diffusion, and solubility coefficients have been obtained for each material with PVDF and PA11 grades showing the lowest permeability coefficients and hence the best barrier properties to permeation. Crystallinity percentages and internal air void contents in the polymer samples have also been used to assess the differences in permeability between materials with an analysis of void dispersion effects given through X‐ray CT scanning techniques. The measured permeability coefficients have been used to assess the ability of all materials tested to act as a functional polymer liner in a standard COPV with final leak rates predicted based on liner thicknesses and weights. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2016,133, 43675.

Experimental study on CO2 diffusion in bulk n-decane and n-decane saturated porous media using micro-CT

Molecular diffusion has been considered to be an underlying mechanism for many oil recovery processes. Reliable estimation of the molecular diffusion coefficient as a transport property is therefore important for CO2-enhanced oil recovery. In the present work, the dynamic processes of CO2 diffusion in bulk n-decane and n-decane saturated porous media were investigated using the micro-focus X-ray CT (micro-CT) scanning technique. CO2 diffusion was visually and quantitatively analyzed by interpreting the CO2 concentration with grayscale CT images. Next, local CO2 diffusion coefficients, varying with time and position, were calculated from concentration profiles based on Fick's second law. The results showed that the local diffusion coefficients in bulk n-decane demonstrate an exponential function of diffusion distance and time. The total diffusion coefficients in bulk oil under pressure from 1 to 6 MPa and temperature at 29 °C and 35 °C were calculated. The results showed that the initial pressure has a strong influence on the diffusion coefficient, i.e., high CO2 initial pressure leads to high CO2 diffusivity in oil. Experiment results in n-decane saturated porous media showed that the CO2 local diffusion coefficient decreases gradually along the diffusion path with time until reaching a stable state. The total diffusion coefficients in n-decane saturated porous media were smaller than those in bulk oil under the same pressure and temperature conditions because the diffusion path is more complicated than in bulk oil. It is demonstrated that the pathways of porous media impede CO2 mass transfer and decrease the diffusion coefficient.

Targeted computerised tomography scanning of the ankle syndesmosis with low dose radiation exposure.

To devise a new protocol for targeted CTscanning of the distal tibiofibular syndesmosis with minimal radiation exposure to patients. We also aimed to correlate the reduction of the syndesmosis as seen on CT scans with the functional outcome of patients. Prospective study. Forty adults undergoing surgical stabilisation of an acute distal tibiofibular syndesmosis injury were recruited. A targeted five-cut computerised tomography scan protocol was developed. The radiation exposure to the patient with this protocol was only 0.002 mSv. Scans were performed 12 weeks after surgery. The contralateral ankle of every patient was used as a control to determine the accuracy of the reduction of the syndesmosis for that individual patient. American Orthopaedic Foot and Ankle Society (AOFAS) scores were obtained at a minimum of 1 year after surgery. After considering the exclusions, 36 patients formed the study group. A wide variation was observed in the anatomy of the normal syndesmosis. If we considered a difference of more than 2 mm between the normal and injured syndesmosis relationship as significant, 15 (41.6 %) of our patients had a significant difference between the injured and normal sides. AOFAS scores were available for 13 of these patients and were good to excellent in 11(84.6 %). Our study describes a reliable new CT scanning technique for the distal tibiofibular syndesmosis using only five cuts and a low-radiation-dose protocol. Clinical correlation of the findings on the scan with functional outcomes suggests that routine post-operative CT of the syndesmosis is probably not justified.

Structural Morphology of Molars in Large Mammalian Herbivores: Enamel Content Varies between Tooth Positions.

The distribution of dental tissues in mammalian herbivores can be very different from taxon to taxon. While grazers tend to have more elaborated and complexly folded enamel ridges, browsers have less complex enamel ridges which can even be so far reduced that they are completely lost. The gradient in relative enamel content and complexity of structures has so far not been addressed within a single species. However, several studies have noted tooth position specific wear rates in small mammals (rabbits, guinea pigs) which may be related to individual tooth morphology. We investigate whether differentiated enamel content by tooth position is also to be found in large herbivores. We use CT-scanning techniques to quantify relative enamel content in upper and lower molar teeth of 21 large herbivorous mammal species. By using a broad approach and including both perissodactyls and artiodactyls, we address phylogenetic intraspecific differences in relative enamel content. We find that enamel is highly unevenly distributed among molars (upper M1, M2, M3 and lower m1, m2, m3) in most taxa and that relative enamel content is independent of phylogeny. Overall, relative enamel content increases along the molar tooth row and is significantly higher in lower molars compared to upper molars. We relate this differential enamel content to prolonged mineralisation in the posterior tooth positions and suggest a compensatory function of m3 and M3 for functional losses of anterior teeth.

Validation of high-resolution gamma-ray computed tomography for quantitative gas holdup measurements in centrifugal pumps

In this article, the capability of high-resolution gamma-ray computed tomography (HireCT) for quantitative gas–liquid phase distribution measurements in commercially available industrial pumps is experimentally investigated. The object of interest thereby operates under two-phase flow conditions. HireCT System comprises a collimated 137Cs isotopic source, a radiation detector arc with a multi-channel signal processing unit, and a rotary unit enabling CT scans of objects with diameters of up to 700 mm. The accuracy of gas holdup measurements was validated on a sophisticated modular test mockup replicating defined gas–liquid distributions, which are expected in impeller chambers of industrial centrifugal pumps under two-phase operation. Stationary as well as rotation-synchronized CT scanning techniques have been analyzed, which are both used to obtain sharply resolved gas phase distributions in rotating structures as well as non-rotating zones. A measuring accuracy of better than 1% absolute for variously distributed static gas holdups in the rotating frame has been verified with the modular test mockup using HireCT.

Effects of automatic tube potential selection on radiation dose index, image quality, and lesion detectability in pediatric abdominopelvic CT and CTA: a phantom study.

To assess the effect of automatic tube potential selection (ATPS) on radiation dose, image quality, and lesion detectability in paediatric abdominopelvic CT and CT angiography (CTA). A paediatric modular phantom with contrast inserts was examined with routine pitch (1.4) and high pitch (3.0) using a standard abdominopelvic protocol with fixed 120 kVp, and ATPS with variable kVp in non-contrast, contrast-enhanced, and CTA mode. The volume CT dose index (CTDIvol), contrast-to-noise ratio (CNR) and lesion detectability index (d') were compared between the standard protocol and ATPS examinations. CTDIvol was reduced in all routine pitch ATPS examinations, with dose reductions of 27-52 % in CTA mode (P < 0.0001), 15-33 % in contrast-enhanced mode (P = 0.0003) and 8-14 % in non-contrast mode (P = 0.03). Iodine and soft tissue insert CNR and d' were improved or maintained in all ATPS examinations. kVp and dose were reduced in 25 % of high pitch ATPS examinations and in none of the full phantom examinations obtained after a single full phantom localizer. ATPS reduces radiation dose while maintaining image quality and lesion detectability in routine pitch paediatric abdominopelvic CT and CTA, but technical factors such as pitch and imaging range must be considered to optimize ATPS benefits. ATPS automatically individualizes CT scan technique for each patient. ATPS lowers radiation dose in routine pitch pediatric abdominopelvic CT and CTA. There is no loss of image quality or lesion detectability with ATPS. Pitch and scan range impact the effectiveness of ATPS dose reduction.

Yes, but does it produce better doctors?

Yes, but does it produce better doctors?

Evolution of Permeability during Fracturing Processes in Rocks under Conditions of Geological Storage of CO&lt;sub&gt;2&lt;/sub&gt;

We investigated experimentally the change in permeability in three different types of soft rocks including mudstone, sandstone, and tuff from the Fureoi and Takinoue formations, which are representative of the CCS demonstration site at Tomakomai in Japan, and another type of mudstone from the Besho Fm. (B-M). Permeability during deformation, shear fracturing, and post-failure slipping is estimated from measured flow rate and differential pore pressure. In addition, the morphologies of the shear fracture zones were examined using the X-ray CT scanning technique. All the samples exhibit typical brittle-fracturing behaviors, except for the B-M sample which does not show a major shear fracture. During the fracturing process, the permeability increased by one to three orders of magnitude. Further changes in the post-failure slipping and stress relaxation regimes show strong dependence on the type of rocks. Observed changes in permeability can be interpreted as results of fracturing creation, shear zone smoothing, closure and reactivation of fractures under different stress regimes. [doi:10.2320/matertrans.M-M2015802]

Recent advancements in X-ray CT tomography as a geosciences tool for coalbed methane exploration

The quantification of the volume and spatial disposition of pores, fractures or cleats and minerals in coals is a primary and fundamental requirement for CBM reservoir evaluation. Coal as a CBM reservoir is a complex polymeric material with complex porous structures which are important for flow pathway that determine the permeability and producibility of coalbed methane. The CT scan computed tomography is a non-destructive technique that can provide quantitative detection and visualization of interior structure of rocks in 3D within opaque objects. This paper will inform several applications illustrate the possibilities, specific advantages and limitations of CT for non-destructive coal characterization in describing the fracture and cleat characteristics including fracture-size patterns, network geometries in coal which is very useful in quantified and 3D visualization of the spatial disposition of minerals, pores and fractures in coals. As with every technique there are always some restrictions that can happen, however the CT scan technique proved to be an emerging non-destructive analysis which gives promising results in CBM exploration activities

Brain and behaviour of living and extinct echidnas

The Tachyglossidae (long- and short-beaked echidnas) are a family of monotremes, confined to Australia and New Guinea, that exhibit striking trigeminal, olfactory and cortical specialisations. Several species of long-beaked echidna (Zaglossus robusta, Zaglossus hacketti, Megalibgwilia ramsayi) were part of the large-bodied (10kg or more) fauna of Pleistocene Australasia, but only the diminutive (2–7kg) Tachyglossus aculeatus is widespread today on the Australian mainland. We used high-resolution CT scanning and other osteological techniques to determine whether the remarkable neurological specialisations of modern echidnas were also present in Pleistocene forms or have undergone modification as the Australian climate changed in the transition from the Pleistocene to the Holocene. All the living and extinct echidnas studied have a similar pattern of cortical gyrification that suggests comparable functional topography to the modern short-beaked form. Osteological features related to olfactory, trigeminal, auditory and vestibular specialisation (e.g., foramina and cribriform plate area, osseous labyrinth topography) are also similar in living and extinct species. Our findings indicate that despite differences in diet, habitat and body size, the suite of neurological specialisations in the Tachyglossidae has been remarkably constant: encephalisation, sensory anatomy and specialisation (olfactory, trigeminal, auditory and vestibular), hypoglossal nerve size and cortical topography have all been stable neurological features of the group for at least 300,000 years.

Computer A ided Detection of Tumours in Mammograms

Mammography is a special CT scan technique, which uses X-rays and high-resolution film to detect breast tumors efficiently. Mammography is used only in breast tumor detection, and images help physicians to detect diseases due to cells normal growth. Mammography is an effective imaging modality for early breast cancer abnormalities detection. Computer aided diagnosis helps the radiologists to detect abnormalities earlier than traditional procedures. In this paper, an automated mammogram classification method is presented. Symlet, singular value decomposition and weighted histograms are used for feature extraction in mammograms. The extracted features are classified using nai ve bayes, random forest and neural network algorithms.

Determination of dynamic relative permeability in ultra-low permeability sandstones via X-ray CT technique

Forced oil–water displacement is the crucial mechanisms of secondary oil recovery. The knowledge of relative permeability is required in the simulation of multiphase flow in porous media. Obvious dynamic effect of capillary pressure occurs in that the formation of ultra-low permeability reservoir (the permeability is <1 × 10−3 μm2) is tight and the pores and throats are very small. In addition, the significant capillary end effect causes serious errors when calculating relative permeabilities. For these reasons, the JBN method (neglecting capillary pressure) does not apply. Therefore, the dynamic capillary pressure and capillary end effects should be taken into account. This work focuses on calculating two-phase relative permeability of ultra-low permeability reservoir through considering the dynamic capillary pressure and eliminating the influence of capillary end effects. Firstly, laboratory core scale measurements of in situ water phase saturation history based on X-ray CT scanning technique were used to estimate relative permeability. Secondly, a mathematical model of two-phase relative permeability considering the dynamic capillary pressure was established. The basic problem formulations, as well as the more specific equations, were given, and the results of comparison using experimental data are presented and discussed. Results indicate that the dynamic capillary pressure measured at laboratory core scale in ultra-low permeability rocks has a significant influence on the estimation of unsteady-state relative permeability. The mathematical calculating method was compared with the history matching method and the results were close, suggesting reliability for ultra-low permeability reservoirs. Importantly, the proposed methods allow measurement of relative permeability from a single experiment. Potentially this represents a great time savings.

细观渗流的研究与进展

随着渗流力学在各个领域的发展，很多问题需求描述细观的渗流过程例如多孔介质中气液界面的运动。本文基于多孔介质，阐述了经典渗流力学、CT扫描建模技术、逾渗理论、微观渗流仿真模拟技术和拓扑网络模型等若干方法对细观单相渗流与多相渗流的描述与解决方法，并对每种方法的特点进行总结分析，展望了发展前景。 With the development of seepage mechanics in various fields, many problems demand the flow process of micro seepage such as the movement of gas-liquid interface in porous medium. In this paper, the problems and solutions of the single phase and multi phase micro seepage based on the classical seepage mechanics, CT scanning technique, percolation theory, micro seepage simulation technique and topology network model in porous medium are expounded. Also the characteristics of each method were analyzed, and the future development was prospected.

EURECCA consensus conference highlights about colon &amp; rectal cancer multidisciplinary management: The radiology experts review

Some interesting shifts have taken place in the diagnostic approach for detection of colorectal lesions over the past decade. This article accompanies the recent EURECCA consensus group reccomendations for optimal management of colon and rectal cancers. In summary, imaging has a crucial role to play in the diagnosis, staging assessment and follow up of patients with colon and rectal cancer. Recent advances include the use of CT colonography instead of Barium Enema in the diagnosis of colonoic cancer and as an alternative to colonoscopy. Modern mutlidetector CT scanning techniques have also shown improvements in prognostic stratification of patients with colonic cancer and clinical trials are underway testing the selective use of neoadjuvant therapy for imaging identified high risk colon cancers. In rectal cancer, high resolution MRI with a voxel size less or equal to 3 × 1 × 1 mm3 on T2-weighted images has a proven ability to accurately stage patients with rectal cancer. Moreover, preoperative identification of prognostic features allows stratification of patients into different prognostic groups based on assessment of depth of extramural spread, relationship of the tumour edge to the mesorectal fascia (MRF) and extramural venous invasion (EMVI). These poor prognostic features predict an increased risk of local recurrence and/or metastatic disease and should form the basis for preoperative local staging and multidisciplinary preoperative discussion of patient treatment options.

Value of a virtual hepatic segment model in assisting in the ultrasonic localization of intrahepatic lesions

Background During scanning of the right hypochondrium and right intercostal regions with an ultrasonic transducer, several ultrasonic images of oblique sections are obtained. It is still a challenge for ultrasonography to divide these non-conventional sections into an accurate hepatic segmentation pattern. The aim of this research was to investigate the value of the virtual hepatic segment model (VHSM) in assisting the ultrasonic localization of space-occupying hepatic lesions. Methods VHSM was constructed via 3D reconstruction according to the first Chinese visible human dataset. Preoperative ultrasonography, contrast-enhanced CT scan and VHSM techniques were performed in 100 patients with space-occupying focal lesions in the liver parenchyma for segmental localization. The results of these three techniques were compared with the operative findings. Results VHSM was successfully detected on 2D sectional images by 3D reconstruction through surface rendering and volume rendering. The model could simulate ultrasonic directions to conduct a virtual dissection on any section plane, and fine liver segmentation could be displayed in any virtual plane. In 100 patients, there were 112 liver space-occupying focal lesions distributed in 148 liver segmentations. Regarding the positioning accuracies for lesions of different sizes and the lesion segmental distribution accuracies estimated using the three methods mentioned above, ultrasonography exhibited a significantly lower accuracy than VHSM for the segmental localization of lesions (P &lt;0.05), and contrast-enhanced CT was not significantly different from ultrasonography plus VHSM (P &gt;0.05). Conclusion VHSM increased the accuracy of ultrasonic localization of space-occupying hepatic lesions, particularly in hepatic hypovascular regions.

3D reconstruction method and connectivity rules of fracture networks generated under different mining layouts

In current research, a series of triaxial tests, which were employed to simulate three typical mining layouts (i.e., top-coal caving, non-pillar mining and protected coal seam mining), were conducted on coal by using MTS815 Flex Test GT rock mechanics test system, and the fracture networks in the broken coal samples were qualitatively and quantitatively investigated by employing CT scanning and 3D reconstruction techniques. This work aimed at providing a detail description on the micro-structure and fracture-connectivity characteristics of rupture coal samples under different mining layouts. The results show that: (i) for protected coal seam mining layout, the coal specimens failure is in a compression-shear manner and oppositely, (ii) the tension–shear failure phenomenon is observed for top-coal caving and non-pillar mining layouts. By investigating the connectivity features of the generated fractures in the direction of σ1 under different mining layouts, it is found that the connectivity level of the fractures of the samples corresponding to non-pillar mining layout was the highest.