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Objective: To determine whether a simulated low-dose metal artifact reduction (MAR) CT technique is comparable with a clinical dose MAR technique for shoulder arthroplasty evaluation. Materials and methods: Two shoulder arthroplasties in cadavers and 25 shoulder arthroplasties in patients were scanned using a clinical dose (140 kVp, 300 qrmAs); cadavers were also scanned at half dose (140 kVp, 150 qrmAs). Images were reconstructed using a MAR CT algorithm at full dose and a noise-insertion algorithm simulating 50% dose reduction. For the actual and simulated half-dose cadaver scans, differences in SD for regions of interest were assessed, and streak artifact near the arthroplasty was graded by 3 blinded readers. Simulated half-dose scans were compared with full-dose scans in patients by measuring differences in implant position and by comparing readers' grades of periprosthetic osteolysis and muscle atrophy. Results: The mean difference in SD between actual and simulated half-dose methods was 2.42 HU (95% CI [1.4, 3.4]). No differences in streak artifact grades were seen in 13/18 (72.2%) comparisons in cadavers. In patients, differences in implant position measurements were within 1° or 1 mm in 149/150 (99.3%) measurements. The inter-reader agreement rates were nearly identical when readers were using full-dose (77.3% [232/300] for osteolysis and 76.9% [173/225] for muscle atrophy) and simulated half-dose (76.7% [920/1200] for osteolysis and 74.0% [666/900] for muscle atrophy) scans. Conclusion: A simulated half-dose MAR CT technique is comparable both quantitatively and qualitatively with a standard-dose technique for shoulder arthroplasty evaluation, demonstrating that this technique could be used to reduce dose in arthroplasty imaging. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the feasibility of producing 2-dimensional (2D) virtual noncontrast images and 3-dimensional (3D) bone models from dual-energy computed tomography (DECT) arthrograms and to determine whether this is best accomplished using 190 keV virtual monoenergetic images (VMI) or virtual unenhanced (VUE) images. Materials and methods: VMI and VUE images were retrospectively reconstructed from patients with internal derangement of the shoulder or knee joint who underwent DECT arthrography between September 2017 and August 2019. A region of interest was placed in the area of brightest contrast, and the mean attenuation (in Hounsfield units [HUs]) was recorded. Two blinded musculoskeletal radiologists qualitatively graded the 2D images and 3D models using scores ranging from 0 to 3 (0 considered optimal). Results: Twenty-six patients (mean age ± SD, 57.5 ± 16.8 years; 6 women) were included in the study. The contrast attenuation on VUE images (overall mean ± SD, 10.5 ± 16.4 HU; knee, 19.3 ± 10.7 HU; shoulder, 5.0 ± 17.2 HU) was significantly lower (p < 0.001 for all comparisons) than on VMI (overall mean ± SD, 107.7 ± 43.8 HU; knee, 104.6 ± 31.1 HU; shoulder, 109.6 ± 51.0 HU). The proportion of cases with optimal scores (0 or 1) was significantly higher with VUE than with VMI for both 2D and 3D images (p < 0.001). Conclusions: DECT arthrography can be used to produce 2D virtual noncontrast images and to generate 3D bone models. The VUE technique is superior to VMI in producing virtual noncontrast images. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate a contiguous helical CT protocol with two different target noise levels in chest/abdomen/pelvis CT.Methods: 41 patients (study group) underwent a helical scan (P1) with two different target noise levels (SDs), SD = 16 for chest and SD = 13 for abdomen/pelvis. Two further protocols were planned but not executed: a single helical scan with only one SD (SD = 13) for the entire scan range (P2), and two separate helical scans overlapping over the liver and same SD settings as for P1 (P3). All DLPs were recorded. Image quality was assessed qualitatively and quantitatively on all scans. The control group consisted of 40 patients, was scanned with protocol P3 and analysed using the same metrics.Results: DLPs (mean/SD) for P1, P2 and P3 were 859.5/392.9, 1040.2/510.5 and 1027.4/469.4, respectively. P1 offered a mean dose reduction of 17.4% compared to P2, and 16.3% compared to P3 (both p < 0.001). There were no differences in image quality between both patient groups (p > 0.3).Conclusion: Contiguous helical scanning of the chest/abdomen/pelvis with variable target noise levels results in approximately 17% dose reduction if compared to a single acquisition with only abdominal dose settings or two separate acquisitions of the chest and abdomen/pelvis.Key Points: • Low dose chest and standard abdomen CTs can be combined. • Variable SD CT scanning allows for radiation dose reduction. • Variable SD CT scanning maintains image quality. [ABSTRACT FROM AUTHOR]

Malan loess is a grayish yellow or brownish yellow, clastic, highly porous and brittle late Quaternary sediment formed by the accumulation of windblown dust. The present-day pore structure of Malan loess is crucial for understanding the loessification process in history, loess strengths and mechanical behavior. This study employed a modern computed tomography (CT) device to scan Malan loess samples, which were obtained from the east part of the Loess Plateau of China. A sophisticated and efficient workflow for processing the CT images and constructing 3D pore models was established by selecting and programming relevant mathematical algorithms in MATLAB, such as the maximum entropy method, medial axis method, and node recognition algorithm. Individual pipes within the Malan loess were identified and constructed by partitioning and recombining links in the 3D pore model. The macropore structure of Malan loess was then depicted using quantitative parameters. The parameters derived from 2D images of CT scanning included equivalent radius, length and aspect ratio of pores, porosity, and pore distribution entropy, whereas those derived from the constructed 3D structure models included porosity, coordination number, node density, pipe radius, length, length density, dip angle, and dip direction. The analysis of these parameters revealed that Malan loess is a strongly anisotropic geomaterial with a dense and complex network of pores and pipes. The pores discovered on horizontal images, perpendicular to the vertical direction, were round and relatively uniform in shape and size and evenly distributed, whereas the pores discovered on vertical images varied in shape and size and were distributed in clusters. The pores showed good connectivity in vertical direction and formed vertically aligned pipes but displayed weak connectivity in horizontal directions. The pipes in vertical direction were thick, long, and straight compared with those in horizontal directions. These results were in good agreement with both numerical simulation and laboratory permeability tests, which indicate that Malan loess is more permeable in the vertical direction than in the horizontal directions. [ABSTRACT FROM AUTHOR]

CT colonography (CTC) has demonstrated equivalent accuracy to optical colonoscopy in the detection of clinically relevant polyps and tumors but this is only possible when technique is optimized. The two most important features of a high-quality CTC are a well-prepared colon and a distended colon. This article will discuss the dietary, bowel preparation, and fecal/fluid tagging options to best prepare the colon. Strategies to optimally distend the colon will also be discussed. CT scan techniques including patient positioning and radiation dose optimization will be reviewed. With proper technique which includes sufficient bowel preparation, fecal/fluid tagging, bowel distension, and optimized scan technique, high-quality CTC examinations should become more feasible, easier to interpret, and more consistently reproducible leading to increased utilization and increased referrals. [ABSTRACT FROM AUTHOR]

Background: To evaluate the efficacy of automatic bolus tracking in multidetector row CT (MDCT) for pancreatic adenocarcinoma as compared with standard scan delay using the fixed duration contrast injection technique. Materials and Methods: Seventy-nine patients with pancreatic adenocarcinomas underwent three-phase enhanced CT with an individualized scan delay as determined by automatic bolus tracking (protocol 1) or an empiric scan delay (protocol 2). We evaluated enhancement of the aorta, portal vein, hepatic parenchyma, pancreatic parenchyma, and pancreatic adenocarcinoma during each phase. Two radiologists graded the conspicuity of pancreatic adenocarcinoma in the pancreatic parenchymal phase. The results for the different groups were statistically compared. Results: Pancreatic parenchymal enhancement (mean ± standard deviation, 100.2 HU ± 17.6 vs. 88.5 HU ± 22.1; P < 0.05) and tumor-to-pancreas contrast (mean ± standard deviation, 75.3 HU ± 25.0 vs. 63.1 HU ± 24.1; P < 0.05) were significantly greater in protocol 1 than in protocol 2 during pancreatic parenchymal phase. Qualitative results correlated well with quantitative results (reviewer 1: R (s) = 0.78, P < 0.001; reviewer 2: R (s) = 0.66, P < 0.001) Conclusion: The use of automatic bolus tracking with MDCT can significantly improve the degree of contrast enhancement in the pancreatic parenchyma and tumor-to-pancreas conspicuity. [ABSTRACT FROM AUTHOR]

Abstract: Purpose: To compare accuracy of non-enhanced CT (NECT) (no oral or IV contrast) and enhanced CT (ECT) (IV enhanced only) to diagnose small bowel obstruction and evaluate reviewer''s experience impact. Materials and methods: Ninety-nine adult patients underwent 105 NECT and ECT (6 patients had 2 examinations) on a four-detector CT. An abdominal radiologist, an abdominal imaging fellow, a second-year radiology resident retrospectively reviewed NECTs and ECTs separately and independently blinded to outcome. Discrepancy of diameter of proximal and distal small bowel±a transition was considered indication of mechanical bowel obstruction. Reference standard was surgery in 26 and chart review in 79. Results: Mechanical obstruction was present in 56% (59/105). The average sensitivity, specificity, negative and positive predictive and accuracy values for NECT were 88.1% (CI: 80–96%), 77% (CI: 65–89%), 83.0% (CI: 72–95%), 83% (CI: 74–92%), and 83% (CI: 76–90%) with no significant difference between three reviewers. The corresponding numbers for ECT were 87.6% (CI: 79–96%), 75% (CI: 63–88%), 82.6.0% (CI: 71–94%), 82.1% (CI: 73–92%), and 82% (CI: 75–90%) (p >0.5). Area under curve (AUC) of ROC curves of three reviewers did not show significant statistical difference (p >0.5). Conclusions: NECT and ECT have comparable accuracy to diagnose mechanical small bowel obstruction and can be interpreted by reviewers with different levels of expertise. [Copyright &y& Elsevier]

Abstract: Purpose: To prospectively assess the relationship between the time to peak enhancement of hepatocellular carcinomas (HCC) and that of the aorta at 64-detector computed tomography (CT). Materials and methods: The study prospectively included 43 patients with known HCC. All underwent abdominal CT imaging by using BodyPerfusion CT model. The CT data acquisition was initiated with a delay of 8–15s from the beginning of the contrast material administered. The time–density curves (TDC) of the HCC and the aorta were drawn. The times to peak enhancement of the HCC and the aorta were recorded and the correlation between the time to peak enhancement of the HCC and that of the aorta was analyzed. Results: There were three tendencies of TDC of the HCC enhancement, only 23.3% of them were similar to that of the aorta. The mean time to peak enhancement of the aorta and the HCC (86.1%) was 23.38s and 30.04s, respectively. The time to peak enhancement of most HCC was positively and linearly correlated with the time to peak aortic enhancement (r =0.662, P <0.05). Conclusion: The result may potentially allow scan delay optimization at contrast material-enhanced CT image in the detection of HCC according to interindividual variability. [Copyright &y& Elsevier]

Background: Dose modulation can be used to reduce the radiation dose in computed tomography (CT) examinations while still obtaining the necessary diagnostic image quality. Multidetector-row computed tomography (MDCT) provides the possibility of simultaneous reconstruction of thin and thick slices from the same raw data. Purpose: To compare thin slices reconstructed from a dose-modulated helical acquisition and conventional high-resolution computed tomography (HRCT) images taken with the “step and shoot” technique in terms of visibility and motion artifacts, in order to investigate the possibility of excluding “step and shoot” acquisition from the HRCT examination. Material and Methods: Twenty patients were examined by a dose-modulated helical acquisition, “MDCT smart mA,” and by a noncontiguous cross-sectional high-resolution 16-row MDCT examination, “MDCT step and shoot.” Images from four anatomical levels, made anonymous regarding identity and technical data, were analyzed in random order by four thoracic radiologists. Results: “MDCT smart mA” was worse than “MDCT step and shoot” in terms of visibility. Concerning motion artifacts, “MDCT smart mA” was better than “MDCT step and shoot.” Conclusion: Thin images reconstructed from a dose-modulated 16-row helical MDCT acquisition (“MDCT smart mA”), as performed in our study, do not provide sufficient image quality regarding visibility compared to the “MDCT step and shoot” technique for the latter technique to be excluded from the HRCT examination. [ABSTRACT FROM AUTHOR]

Background: High-resolution computed tomography is the image procedure of choice in the evaluation of interstitial lung disease. Multidetector-row computed tomography provides the possibility of simultaneous reconstruction of thin and thick slices from the same raw data, acquired from one single series. Thus, it may be tempting to exclude the step-and-shoot series. Purpose: To compare high-resolution computed tomography (HRCT step-and-shoot) from single-slice CT (SSCT) and 16-channel multidetector CT (MDCT) in terms of visibility and motion artifacts, and to investigate whether thin images reconstructed from helical MDCT are equal to or better than conventional HRCT by SSCT in terms of visibility and motion artifacts. Material and Methods: 20 patients underwent HRCT step-and-shoot by SSCT (SSCT step-and-shoot) and MDCT (MDCT step-and-shoot), and a helical MDCT acquisition (MDCT helical). Images from four anatomical levels were analyzed in random order regarding visibility and motion artifacts. Results: Visibility using MDCT step-and-shoot was significantly better than or equal to SSCT step-and-shoot for segmental bronchi and fissures, but not for subsegmental bronchi. For MDCT helical, visibility was equal to or better than SSCT step-and-shoot for segmental bronchi, but not for fissures and subsegmental bronchi. Concerning motion artifacts, MDCT step-and-shoot and MDCT helical were significantly better than or equal to SSCT step-and-shoot. Conclusion: The image quality (accounting for motion artifacts and visibility) of SSCT step-and-shoot and MDCT step-and-shoot is comparable. The visibility of anatomic structures in images from MDCT helical is inferior to HRCT step-and-shoot. [ABSTRACT FROM AUTHOR]

Background: We performed a pilot study examining the feasibility of a new unprepped CT colonography (CTC) strategy: low fiber diet and tagging (unprepped) vs. low fiber diet, tagging and a magnesium citrate cleansing preparation (prepped). Prior reports of tagging were limited in that the residual stool was neither measured and stratified by size nor did prior reports subjectively evaluate the ease of interpretation by a reader experienced in interpreting CTC examinations. Methods: Prospective randomized to unprepped n = 14 and prepped n = 14. Colonic segments were subjectively evaluated for residual stool that would potentially interfere with interpretation. Scores were given in the following categories: percentage of residual stool that was touching or nearly touching mucosa, the largest piece of retained stool, effectiveness of tagging, height of residual fluid, degree of distention, ease of interpretation, and reading time. Results: Ease of the CT read (scale where 4 = optimal read) averaged 1.3 for the unprepped group and 2.3 for the prepped group. The mean read time averaged 17.5 min for unprepped and 17.9 min for prepped. The degree of distention (scale where 4 = well distended) averaged 3.7 for unprepped and 3.6 for prepped. Supine and prone images combined, the unprepped group had 160 segments with stool; prepped group had 58 segments. The amount of stool covering the mucosa in all segments averaged 1.6 (33%-66% coverage) in the unprepped group and 0.35 (<33% mucosal coverage) in the prepped group. The mean size of the largest piece of stool was 33.67 mm for unprepped and 4.01 mm for prepped. Percentage of tagged stool was not significantly different between the groups (range of 94-98%). The height of residual fluid averaged 8.37 mm for unprepped and 13.4 mm for prepped. Three polyps in three patients were found during optical colonoscopy (OC) in the unprepped group (5, 6, and 10 mm), none of which were prospectively detected at CTC. Three polyps in three patients were detected during OC in the prepped group (5, 10, and 15 mm), two of which were prospectively detected at CTC. Two false-positive lesions were observed at CTC in one patient in the prepped group. Conclusion: There was more stool in the unprepped group and while this factor did not slow down the reading time, it made the examination subjectively harder to interpret and likely caused the three polyps in this group to be missed. We conclude that a truly unprepped strategy that leaves significant residual stool, even if well tagged, is not desirable. [ABSTRACT FROM AUTHOR]

Focuses on the use of multislice computed tomographic angiography (CTA) in diagnosing peripheral arterial occlusive disease. Range that can be covered by a multislice CTA; Factor that limits CTA; Details of how CTA acquires data; Persons who are not recommended to receive CTA.

Multislice scanning has substantially improved the performance of CT scanners, and thus the relation between scan duration, available scan length, and spatial resolution along the patient axis (zaxis). Near-isotropic imaging of whole organ systems is already possible with 4-slice scanners, but only with 8 to 16-slice scanners can the scan duration be shortened as well. Reconstructing overlapping thin-section data ("secondary raw data set") provides the basis for image reconstruction in any desired plane. By using thick multiplanar reformation (MPR) techniques, image quality can be improved while keeping patient dose low. Using unfavorable scanfling parameters, exposure dose can be substantially increased compared with single-slice scanning, but thick MPR and individual-dose modulation techniques can provide the basis for dose reduction. Low-kVp scanning, in particular, is useful in children and slim adults and is an excellent technique to improve image contrast in CT angiographic studies. Short spiral scans should be avoided with multislice CT since overranging (extra rotations at the beginning and end of the scan, used for data interpolation) can substantially increase patient dose. Future trends include the introduction of thinner detector rows, wider detector arrays, faster tube rotation, and area detectors than can also be used for fluoroscopy. Noise-reduction techniques and individual dose modulation will gain importance with higher isotropic resolution. Functional and perfusion imaging, as well as advanced image processing and computer-aided diagnosis programs, will add to the possibilities of the next generation of multislice CT scanners. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the accuracy of 3-mm-thick reconstructed sections in the diagnosis of bronchiectasis with multislice CT (MSCT). Forty consecutive patients suspected of bronchiectasis (23 females, 17 males; mean age 51 years) underwent MSCT of the entire thorax with a 4×1-mm collimation (120 kV, 0.5 s/rotation, 80 mAs/slice) and a pitch of 1.75. From each data set (mean z-axis coverage: 257 mm; mean duration: 21 s), two series of images were systematically generated: 1-mm (group 1) and 3-mm (group 2)-thick reconstructed scans. Both series of images were obtained at 10-mm intervals and reconstructed with a high-spatial-frequency algorithm. Two observers independently analyzed the presence of bronchiectasis and associated abnormalities in group-1 and group-2 lung images. No significant difference between group 1 and group 2 was found in: (a) the detection of bronchiectasis, identified in 24 patients (60%) in group 1 and in 23 patients (57.5%) in group 2 (p=0.08); (b) the evaluation of the extent of bronchiectasis, identifying focal bronchiectasis in 10 patients (25%) in group 1 and 7 patients (17.5%) in group 2 (p=0.39) and multifocal bronchiectasis in 16 patients (40%) in both groups; (c) the characterisation of bronchiectasis (cylindral bronchiectasis: group 1, n=24, 60%; group 2, n=21, 53%, p=0.08); varicose bronchiectasis: group 1, n=5, 12.5%; group 2, n=6, 15%, p=0.56); and cystic bronchiectasis: group 1, n=2, 5%; group 2, n=2, 5%). Apart from the identification of abnormal bronchial wall thickening (group 2, n=35, 87.5%, vs group 1, n=31, 77.5%, p<0.05), recognition of associated bronchopulmonary anomalies did not differ between the two groups. This study demonstrates a comparable accuracy of the 3- and 1-mm-thick reconstructed scans in the detection and characterization of bronchiectasis. These results suggest the potential usefulness of 3-mm-thick scans generated from 4×2.5-mm acquisitions in the screening of bronchiectasis, which would allow a 20% radiation dose reduction compared with the present investigation. [ABSTRACT FROM AUTHOR]

• Flat propagation zone in fatigue surface differed with Si content. • Microvascular network analyses were used in crack analyses. • Crack propagation behavior was measured according to thickness and length. • Crack configuration feature was analyzed statistically. • Stress simulation and microstructural distribution explained the crack propagation difference. Fatigue crack surfaces for three high pressure die casting hypereutectic Al-Si alloy plates were characterized by synchrotron X-ray tomography and CT technology. Focused on the retained pores, microvascular network analyses offered an innovative method to obtain crack configuration feature and analyze the crack propagation behavior in low ductility hypereutectic alloys which in-situ experiments were hard to achieve. With more Si content, the crack local thickness difference along the crack propagation path was more obvious and laid the foundation for more local tortuous morphology. With less Si content, the crack size was tapered and more branches occurred as a way to elongate the crack length. As rigid phases in the microstructure, primary silicon particles worked as obstacle for the whole crack propagation and their volume content agreed with the overall crack fluctuation. Therefore, the difference of flat propagation surface in three alloys was explained by crack configuration difference and crack deflection based on PSPs obstacle effect. [ABSTRACT FROM AUTHOR]

Purpose: To perform anintra-patient comparison betweena single-pass protocol (SP) and a portal venous phase (PVP) by means ofboth quantitative and qualitative analysis of image quality.Methods: Forty patients (31 M; 9F; aged 20-77 years; BMI 23 ± 4 Kg/m2) underwent both a SP and a PVP using a 64-rows multi-detector CT with a median interval time of 56 days (range5-903). All patients underwent i.v. bolus injection (2.0 cc/sec) of 1.7 cc/Kg of a non ionic iodinated contrast-media (370 mgI/ml) with scan delays of 67 ± 8 and 90 s for the SP and the PVP, respectively. Signal- (SNR) and contrast-to-noise ratios (CNR) were calculated for most visceral organs and for both abdominal aorta (AA) and main portal vein (MPV). For qualitative analysis, reproduction of abdominal viscera and vascular structures was blindly evaluated and inter-observer agreement calculated by the weighted Cohen k-analysis.Results: Attenuation values (H.U.) of AA (232 ± 53vs180 ± 36) and MPV (215 ± 39vs187 ± 42) were significantly (p < 0.001) higher in the SP than in PVP, respectively. At qualitative analysis, reproduction of mostabdominal viscerawas also significantly sharper (p < 0.001) with the SP than the PVPwith inter-observer agreement scores (k)ranging from 0.60 to 0.88 for all but one imaging criteria.Conclusions: As the SP resulted in a significantly higher vascular enhancement and in a sharper reproduction of most abdominal viscera, it may be better suited than a PVP for the CT evaluation of non traumatic acute abdomen. [ABSTRACT FROM AUTHOR]

• An accelerated test chamber was designed to simulate the marine environment. • CT technique was used to assess sea salt attack on sea-sand concrete in marine environment. • Different parts and zones of sea-sand concrete in marine environment were subjected to different types of sea salt attack. • The safety of different parts and zones for different sea-sand concrete with the same mix proportion was compared. The deterioration mechanism of sea-sand concrete was different in different marine areas. An accelerated test chamber was designed to simulate the marine environment. Semi-immersion and drying – wetting cycle test were carried out on seawater and siliceous sea-sand concrete (SSC), coral aggregate seawater concrete (CASC) and tap water and desalted siliceous sea-sand concrete (DTC). Through the analysis of CT characteristics of sea-sand concrete in different parts and zones, the deterioration performance and safety comparison of sea-sand concrete were studied. The results were as follows: the types of sea salt attack to sea-sand concrete could be divided into internal sea salt attack (ISA), external sea salt attack (ESA) and physical sea salt attack (PSA). ESA, ISA and PSA could increase the cross-sectional area of the specimens and reduce the macropores. ISA, ESA and PSA could promote the expansion effect of each other. However, with the passage of time, the surface of the specimen affected by ESA would be damaged to a certain extent, resulting in the reduction of the cross-sectional area, which could be aggravated by ISA. The effect of ESA and PSA on mortar density first increased and then decreased, and ISA could increase the mortar density. ISA, ESA and PSA could reduce the macropores in concrete. With the same mix proportion (W/C = 0.52) of these three kinds of sea-sand concretes, at the bottom and middle part, DTC was the weakest concrete. In Zone 5 at the bottom part, SSC was also relatively weak. In Zone 1 at the top part, SSC was the safest concrete, while CASC was the weakest. In zone 5 at the top part, DTC was the weakest concrete, and CASC was the safest. [ABSTRACT FROM AUTHOR]