Purpose
To investigate a benefit from virtual monoenergetic reconstructions (VMIs) for assessment of arterially hyper-enhancing liver lesions in phantom and patients and to compare hybrid-iterative ...and spectral image reconstructions of conventional images (CI-IR and CI-SR).
Methods
All imaging was performed on a SDCT (Philips Healthcare, Best, The Netherlands). Images of a non-anthropomorphic phantom with a lesion-mimicking insert (containing iodine in water solution) and arterial-phase images from contrast-enhanced patient examinations were evaluated. VMIs (40–200 keV, 10 keV increment), CI-IR, and CI-SR were reconstructed using different strengths of image denoising. ROIs were placed in lesions, liver/matrix, muscle; signal-to-noise, contrast-to-noise, and lesion-to-liver ratios (SNR, CNR, and LLR) were calculated. Qualitatively, 40, 70, and 110 keV and CI images were assessed by two radiologists on five-point Likert scales regarding overall image quality, lesion assessment, and noise.
Results
In phantoms, SNR was increased threefold by VMI
40keV
compared with CI-IR/SR (5.8 ± 1.1 vs. 18.8 ± 2.2,
p
≤ 0.001), while no difference was found between CI-IR and CI-SR (
p
= 1). Denoising was capable of noise reduction by 40%. In total, 20 patients exhibiting 51 liver lesions were assessed. Attenuation was the highest in VMI
40keV
, while image noise was comparable to CI-IR resulting in a threefold increase of CNR/LLR (CI-IR 1.3 ± 0.8/4.4 ± 2.0, VMI
40keV
: 3.8 ± 2.7/14.2 ± 7.5,
p
≤ 0.001). Subjective lesion delineation was the best in VMI
40keV
image (
p
≤ 0.01), which also provided the lowest perceptible noise and the best overall image quality.
Conclusions
VMIs improve assessment of arterially hyper-enhancing liver lesions since they increase lesion contrast while maintaining low image noise throughout the entire keV spectrum. These data suggest that to consider VMI screening after arterially hyper-enhancing liver lesions.
Soil structure dependent properties are normally dynamic due to different processes occurring in the soil. However, in classic hydraulic modelling these interactions are generally ignored and may ...result in higher uncertainty of predicted effects. Such investigations are especially relevant in volcanic ash soils in southern Chile because of their intrinsic properties and the climatic conditions of the region. Therefore, the objective of this study was to describe the effect of the land use change of a Typic Hapludand on some soil structure dependent properties and their variability depending on hydraulic conditions using field, laboratory data and modelling.
Two sites on a volcanic ash soil were selected: a native forest (NF) and a prairie used for permanent pasture for over 50
years (P50). In order to register the natural wetting and drying cycles rainfall, soil moisture and temperature at both sites were determined. With the
in situ water content data and shrinkage parameters derived from shrinkage curves, we calculated the temporal changes in moisture and void ratios. To validate our calculations, the soil water and shrinkage curves were determined repeatedly in undisturbed soil samples collected during the rainy season in July and October. Finally, the effect of land use change on temporal variations in the saturated hydraulic conductivity was measured at different times during 96
h of continuous water flow.
The land use change from NF to P50 exposed the soil to greater mechanical and hydraulic stresses and, consequently, to soil deformation. When considering the soil shrinkage by drying, we assessed that the bimodal character of the water retention curve changed only in macro pore range, when the land use changed from NF to P50 affecting the saturated hydraulic conductivity. The void ratio presented a dynamic behaviour depending on the intensity of natural wetting and drying cycles reflecting also the consequences of these cycles in the water retention and shrinkage curves. The saturated hydraulic conductivity decreased during water infiltration as a function of land use due to a particle release, transport and re-sedimentation which probably affects the pore continuity. Finally, we concluded that the structural properties of the studied Andisol are dynamic, presenting spatial and seasonal variability depending on the land use and soil water content. Therefore, in order to understand processes in soil it is necessary to develop and use hydraulic models that considered this behaviour.
►The land use change of an Andisol exposed the soil, to soil settlement. ►Andisols are prone to deformation as a consequence of soil compaction and drying. ►The structural properties of the studied volcanic ash soil are dynamic.
Purpose:
The purpose of this study is the correction of the lateral scanner artifact, i.e., the effect that, on a large homogeneously exposed EBT3 film, a flatbed scanner measures different optical ...densities at different positions along thex axis, the axis parallel to the elongated light source. At constant dose, the measured optical densitiy profiles along this axis have a parabolic shape with significant dose dependent curvature. Therefore, the effect is shortly called the parabola effect. The objective of the algorithm developed in this study is to correct for the parabola effect. Any optical density measured at given position x is transformed into the equivalent optical density c at the apex of the parabola and then converted into the corresponding dose via the calibration of c versus dose.
Methods:
For the present study EBT3 films and an Epson 10000XL scanner including transparency unit were used for the analysis of the parabola effect. The films were irradiated with 6 MV photons from an Elekta Synergy accelerator in a RW3 slab phantom. In order to quantify the effect, ten film pieces with doses graded from 0 to 20.9 Gy were sequentially scanned at eight positions along thex axis and at six positions along the z axis (the movement direction of the light source) both for the portrait and landscape film orientations. In order to test the effectiveness of the new correction algorithm, the dose profiles of an open square field and an IMRT plan were measured by EBT3 films and compared with ionization chamber and ionization chamber array measurement.
Results:
The parabola effect has been numerically studied over the whole measuring field of the Epson 10000XL scanner for doses up to 20.9 Gy and for both film orientations. The presented algorithm transforms any optical density at positionx into the equivalent optical density that would be measured at the same dose at the apex of the parabola. This correction method has been validated up to doses of 5.2 Gy all over the scanner bed with 2D dose distributions of an open square photon field and an IMRT distribution.
Conclusions:
The algorithm presented in this study quantifies and corrects the parabola effect of EBT3 films scanned in commonly used commercial flatbed scanners at doses up to 5.2 Gy. It is easy to implement, and no additional work steps are necessary in daily routine film dosimetry.
Prolonged breath holding results in hypoxemia and hypercapnia. Compensatory mechanisms help maintain adequate oxygen supply to hypoxia sensitive organs, but burden the cardiovascular system. The aim ...was to investigate human compensatory mechanisms and their effects on the cardiovascular system with regard to cardiac function and morphology, blood flow redistribution, serum biomarkers of the adrenergic system and myocardial injury markers following prolonged apnoea.
Seventeen elite apnoea divers performed maximal breath-hold during cardiovascular magnetic resonance imaging (CMR). Two breath-hold sessions were performed to assess (1) cardiac function, myocardial tissue properties and (2) blood flow. In between CMR sessions, a head MRI was performed for the assessment of signs of silent brain ischemia. Urine and blood samples were analysed prior to and up to 4 h after the first breath-hold.
Mean breath-hold time was 297 ± 52 s. Left ventricular (LV) end-systolic, end-diastolic, and stroke volume increased significantly (p < 0.05). Peripheral oxygen saturation, LV ejection fraction, LV fractional shortening, and heart rate decreased significantly (p < 0.05). Blood distribution was diverted to cerebral regions with no significant changes in the descending aorta. Catecholamine levels, high-sensitivity cardiac troponin, and NT-pro-BNP levels increased significantly, but did not reach pathological levels.
Compensatory effects of prolonged apnoea substantially burden the cardiovascular system. CMR tissue characterisation did not reveal acute myocardial injury, indicating that the resulting cardiovascular stress does not exceed compensatory physiological limits in healthy subjects. However, these compensatory mechanisms could overly tax those limits in subjects with pre-existing cardiac disease. For divers interested in competetive apnoea diving, a comprehensive medical exam with a special focus on the cardiovascular system may be warranted.
This prospective single-centre study was approved by the institutional ethics committee review board. It was retrospectively registered under ClinicalTrials.gov (Trial registration: NCT02280226 . Registered 29 October 2014).
Highlights • Feature Tracking (FT) may be employed for the detection of diastolic dysfunction. • FT regional strain analysis lacks consistent correlation to tagged results. • FT derived strain is not ...as reproducible as tagged derived strain. • FT based rotational analysis is not a robust alternative to tagged analysis.
•Prolonged apnea performed by elite divers leads to relevant hypoxemia.•Compensatory mechanisms burden the heart and the vascular system.•No evidence of structural changes in the mid-term.•Elite ...apnea divers are suitable to investigate acute but not chronic hypoxemic effects in vivo.
Prolonged apnea by breath-hold (BH) divers leads to hypoxemia and compensatory mechanisms of the cardiovascular system (i.e. increase of total peripheral resistance, increase of systolic blood-pressure, left-ventricular enlargement) to maintain oxygen supply to oxygen sensitive organs such as the brain. All these changes may result in structural myocardial or subclinical brain alterations. Therefore, the aim of this study was to investigate mid-term effects of repetitive prolonged apnea using cardiac magnetic resonance imaging (CMR) and magnetic resonance imaging of the brain.
17 elite BH divers (15 males) were investigated at baseline, from whom 9 (7 males) were investigated again at follow-up one year later. CMR included functional imaging and tissue characterization using T1- and T2-mapping as well as late gadolinium enhancement. Results were compared intra-individually and with 50 age matched controls.
Mean BH time were 297 ± 52 s (entire cohort) and 315 ± 56 s (sub-cohort) at initial, and 334 ± 104 s at follow-up examination. Apnea resulted in a progressive increase of the left ventricle and impaired function, whichfully resolved after cessation of apnea. At rest, no dilation of the left ventricle was notable (LV-EDV: 106.7 ± 28.8 ml; LV-EDV/BSA: 52.2 ± 12.7 ml/m2). Compared to controls, the apnea group showed significantly lower volumes (LV-EDV: 106.7 ± 28.8 ml vs. 140.9 ± 36.3 ml, p = .008; LV-EDV/BSA: 52.2 ± 12.7 ml/m2 vs. 73.7 ± 12.8 ml/m2). In contrast, LV-EF showed no significant differences between both groups (61.0 ± 7.0% vs. 60.9 ± 3.6%). T1- and T2-mapping revealed no significant differences, neither intra-individually nor in comparison with age matched controls. (T1 pre-contrast: 974.1 ± 12.9 ms vs. 969.4 ± 29.0 ms, p = .2; T1 post-contrast: 368.9 ± 38.5 ms vs. 966.7 ± 40.5 ms, p = .4; ECV: 29.2 ± 1.5% vs. 29.8 ± 1.6%, p = .3; T2. 52 ± 2 ms vs. 52 ± 3 ms; p = .4). Except for one old embolic lesion no structural changes were found in brain imaging.
Although, prolonged apnea leads to impressive adaptions of the cardiovascular system (i.e. dilation of the left ventricle) and hypertension due to peripheral vasoconstriction no mid-term morphological changes could be observed in both, the myocardium and the brain. BH divers are suitable as a model to investigate acute physiological changes of prolonged apnea and hypoxemia, but not as a model for chronic alterations.
Purpose
The purpose of the study was to determine: (1) the relationship between ankle plantarflexor muscle strength and Achilles tendon (AT) biomechanical properties in older female adults, and (2) ...whether muscle strength asymmetries between the individually dominant and non-dominant legs in the above subject group were accompanied by inter-limb AT size differences.
Methods
The maximal generated AT force, AT stiffness, AT Young’s modulus, and AT cross-sectional area (CSA) along its length were determined for both legs in 30 women (65 ± 7 years) using dynamometry, ultrasonography, and magnetic resonance imaging.
Results
No between-leg differences in triceps surae muscle strength were identified between dominant (2798 ± 566 N) and non-dominant limb (2667 ± 512 N). The AT CSA increased gradually in the proximo-distal direction, with no differences between the legs. There was a significant correlation (
P
< 0.05) of maximal AT force with AT stiffness (
r
= 0.500) and Young’s modulus (
r
= 0.414), but only a tendency with the mean AT CSA. However, region-specific analysis revealed a significant relationship between maximal AT force and the proximal part of the AT, indicating that this region is more likely to display morphological adaptations following an increase in muscle strength in older adults.
Conclusions
These findings demonstrate that maximal force-generation capabilities play a more important role in the variation of AT stiffness and material properties than in tendon CSA, suggesting that exercise-induced increases in muscle strength in older adults may lead to changes in tendon stiffness foremost due to alterations in material rather than in its size.
Summary
Kidney disease is one of the leading causes of death in patients with lupus and other autoimmune diseases affecting the kidney, and is associated with deposition of antibodies as well as ...infiltration of T lymphocytes and macrophages, which are responsible for initiation and/or exacerbation of inflammation and tissue injury. Current treatment options have relatively limited efficacy; therefore, novel targets need to be explored. The co‐inhibitory molecule, B7x, a new member of the B7 family expressed predominantly by non‐lymphoid tissues, has been shown to inhibit the proliferation, activation and functional responses of CD4 and CD8 T cells. In this study, we found that B7x was expressed by intrinsic renal cells, and was up‐regulated upon stimulation with inflammatory triggers. After passive administration of antibodies against glomerular antigens, B7x−/− mice developed severe renal injury accompanied by a robust adaptive immune response and kidney up‐regulation of inflammatory mediators, as well as local infiltration of T cells and macrophages. Furthermore, macrophages in the spleen of B7x−/− mice were polarized to an inflammatory phenotype. Finally, treatment with B7x‐immunoglobulin (Ig) in this nephritis model decreased kidney damage and reduced local inflammation. We propose that B7x can modulate kidney damage in autoimmune diseases including lupus nephritis and anti‐glomerular basement membrane disease. Thus, B7x mimetics may be a novel therapeutic option for treatment of immune‐mediated kidney disease.
Soils under loaded conditions may have different shrinkage behaviour from that of load-free soils. In this study, we applied two kinds of mechanical stress (σ) on repacked homogeneous soil samples: ...transient and constant stresses, simulating the traffic load during tillage and the overburden pressure, respectively. Three transient stresses were applied on the soil surface with 150, 400 and 1400 kPa, while the constant stresses ranged from 1.8, 3.8, 5.5, to 7.3 kPa. We hypothesized that the two stresses play different roles in soil shrinkage behaviour as depicted by void ratio (e) and moisture ratio (θ), as compared with load-free soil. Thus, our aim was to build up the relationship between e, θ and σ. For a swelling soil, total pores can be divided into rigid and non-rigid components according to their swelling and shrinkage capacity relative to soil moisture. The non-rigid pores compacted by the transient stress can be regained in the subsequent wetting at load-free conditions, whereas the compacted rigid pores do not recover. The reduction in rigid pores does not alter the soil pore shrinkage capacity. The shrinkage curves of transiently-loaded soils are therefore parallel to each other with an identical coefficient of linear extensibility (COLE) and the same shrinkage slope, although their structural shrinkage phase narrows with an increase of stress. However, the constant stress compresses non-rigid pores readily through suppressing their swelling capacity during wetting as well as compacting rigid pores. If the change of rigid pores is negligible, the shrinkage curves of constantly-loaded soils converge at the zero shrinkage or the dry-end point with the load-free soil shrinkage. If the reductions of rigid and non-rigid pores are both considered, the soil shrinkage combines the part of parallel shrinkage derived from the reduced rigid pores and the intersected shrinkage resulted from the altered non-rigid pores. On the basis of different shrinkage behaviours resulting from the two mechanical stresses, we propose numerical formulae to illustrate a series of curves for the e-θ-σ relationship. The different changes in rigid and non-rigid pores cause soil water release differently.
Renal Denervation: Results of a Single-Center Cohort Study Luetkens, J. A.; Wilhelm, K.; Düsing, R. ...
RöFo : Fortschritte auf dem Gebiet der Röntgenstrahlen und der bildgebende Verfahren,
01/2015, Letnik:
187, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
Purpose:
To investigate the effect of renal denervation on office-based and 24-h ambulatory blood pressure measurements (ABPM) in a highly selective patient population with drug-resistant ...hypertension.
Materials and Methods:
Patients with drug resistant hypertension eligible for renal denervation were included in the study population. Office blood pressure and ABPM were assessed prior to and after renal denervation. To detect procedure related renal or renal artery damage, magnetic resonance imaging (MRI) and angiography (MRA) were performed pre-interventional, one day post-interventional, and one month after renal denervation.
Results:
Mean follow-up time between renal denervation and blood pressure re-assessment was 9.5 ± 3.9 months. Between August 2011 and March 2013, 17 patients prospectively underwent renal denervation. Pre-interventional mean office blood pressure and ABPM were 177.3 ± 20.3/103.8 ± 20.4 mmHg and 155.2 ± 20.5/93.7 ± 14.5 mmHg, respectively. Post-interventional, office blood pressure was significantly reduced to 144.7 ± 14.9/89.5 ± 12.1 (p < 0.05). ABPM values remained unchanged (147.9 ± 20.3/90.3 ± 15.6, p > 0.05). The number of prescribed antihypertensive drugs was unchanged after renal denervation (4.7 ± 2.0 vs. 4.2 ± 1.2, p = 0.18). No renovascular complications were detected in follow-up MRI.
Conclusion:
After renal denervation, no significant decrease in ABPM was observed. These results may indicate a limited impact of renal denervation for drug resistant hypertension.
Key Points:
• Renal denervation showed no significant effects on 24-h ambulatory blood pressure measurements.
• A significant decrease in office blood pressure measurements may be explained by a potential detection bias.
• Renal artery alterations were not observed on follow-up MRI scans.
Citation Format:
• Luetkens J. A., Wilhelm K., Düsing R. et al. Renal Denervation: Results of a Single-Center Cohort Study. Fortschr Röntgenstr 2015; 187: 36 – 41
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