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The use of X-Ray Fluorescence (XRF) Core Scanning for continuous high-resolution analysis of Sr/Ca in corals is investigated here as a new method for analyzing coral material. Corals are valuable archives for generating high resolution palaeoclimate records of sea surface temperatures of the tropical oceans, but traditional methods of analyzing coral geochemistry involve extensive subsampling and wet chemistry techniques to obtain high precision elemental records. More recent developments of micro-beam techniques have limitations in the length of core that can be scanned at any one time. XRF core scanning provides a fast, non-destructive method of analyzing long sections of coral cores whilst maintaining a high sampling resolution. Here we apply this method to two modern corals, from the Sunda Strait, Indonesia and One Tree Island, Great Barrier Reef Australia. We find that results show that XRF core scanning of corals produce Sr/Ca records that capture the annual cycle, particularly from reef sites with a large sea surface temperature range. Coupled density measurements of the coral skeleton also aid in increasing the utility of XRF measurements obtained from coral material, although difficulties remain in reliably reconstructing interannual temperature variability using XRF Sr/Ca determinations. We recommend that XRF can provide a valuable method of quick and non-destructive screening of coral material, prior to more targeted analysis using traditional destructive geochemical analysis. [ABSTRACT FROM AUTHOR]

Mediterranean sediments are valuable archives of both African monsoon variability and higher-latitude climate processes, and can also be used to provide an environmental context for early human migrations and settlements. However, the long history of Mediterranean palaeoclimate studies largely pre-dates the advent of widespread x-ray fluorescence (XRF) core-scanning, so there are few continuous and high-resolution geochemical records from this key region that extend beyond the last glacial cycle. Here we present XRF core-scanning results for ODP Site 967 (Eastern Mediterranean) that have been fully-calibrated into element concentrations spanning the last 3 million years (My). Comparison with independent geochemical data from conventional XRF highlights disparities for certain element/element ratios, thus suggesting the need for caution when taking ratios of scanning XRF data. Principal component analysis of the calibrated XRF dataset reveals two dominant components: detrital inputs (PC1) and a ‘sapropel’ (≈monsoon run-off) signal (PC2), which we use to establish a new orbitally-tuned chronology. We observe inverse covariation between PC2 and a previously published aeolian dust record from ODP Site 967 (Larrasoaña et al., 2003), and combine these records to produce a composite index of humidity and aridity for the wider North African region over the past 3 My. We propose that by combining run-off and dust signals in a single metric, our index captures the effects of both strengthening/northward migration (increased run-off) and weakening/southward retreat (increased dust) of the North African monsoon. Comparison of the index with published records of Northwest and East African palaeohumidity suggests that it tracks the timing of “Green Sahara Periods” throughout the Plio-Pleistocene, and that at least 30 of these intervals coincided with increased humidity across East Africa. We tentatively suggest that these specific episodes may be termed “pan-African Humid Periods”, as a means to highlight large-scale climate trends and to provide an environmental framework for palaeo-anthropological research. [ABSTRACT FROM AUTHOR]

Background The use of cardiac computed tomography (CT) for quantification of ventricular function is limited by relatively high radiation dose. Objectives The goal of this study was to describe the radiation exposure and image quality of 70 kVp functional cardiac CT in patients with congenital heart disease (CHD). Methods A retrospective review of 70 kVp ECG gated functional CT scans using tube current modulation was performed in CHD patients at a single institution. Quantitative and qualitative (assessed by myocardial segment, 1 – 4; 1 = optimal) image quality was determined. Per segment image quality was compared between thin (1.5 mm) and thick (8 mm) reconstructions and by patient age and size. Scan DLP was used to estimate radiation dose. Results 72 scans were performed during the time of review (7/2013-6/2015). Median patient age was 19.5 years (8.0, 27.1) and BMI was 20.1 (16.6, 24.5) kg/m 2 . Median functional scan DLP was 78.8 (45.5, 98) and unadjusted and adjusted procedural mSv were 1.10 (0.64, 1.37) and 1.13 (0.90, 1.37). Image quality of 1 was achieved in all myocardial segments in >75% of scans. Patients with a weight ≥75 kg were more likely to have a scan achieve optimal image when using thick reconstructions compared to thin (81.3% vs. 43.8%; p = 0.028). Conclusions Imaging of ventricular function with 70 kVp in CHD patients can be done with low radiation doses and provides diagnostic image quality, particularly for patients <75 kg. In larger patients, thicker slice reconstruction improved image quality. [ABSTRACT FROM AUTHOR]

Abstract: Background: Neonates with complex congenital heart disease (CHD) are at risk of adverse events from anesthesia. CT angiography (CTA) performed free breathing and without sedation has not been reported for evaluation of complex CHD in neonates. Objectives: The aim was to evaluate the image quality and risk of free breathing, non-sedated cardiac CTA for definition of CHD in the neonatal period and to determine accuracy compared with interventional findings. Methods: This is a combined retrospective–prospective single institution review of all non-sedated, free breathing cardiac CT angiograms performed in patients <1 month of age with complex CHD. Diagnosis, scan acquisition parameters, image quality (1- to 4-point scale), adverse events, radiation dose estimates, and accuracy compared with operative and interventional catheterization findings were recorded. Results are reported as median and interquartile range. Results: Nineteen non-sedated, free breathing, neonatal cardiac CT angiograms were performed during the time of review. All studies were diagnostic with a mean image quality score of 1.1 ± 0.3. Median total procedural dose-length product was 11 (range, 10–14), CT dose index volume was 0.47 (range, 0.31–0.5). Median unadjusted radiation dose was 0.15 mSv (range, 0.14–0.2 mSv), age- and size-adjusted radiation dose was 0.86 mSv (range, 0.78–1.1 mSv). No adverse events and no discrepancies compared with surgical or catheterization findings were found in the 17 of 19 patients that had subsequent intervention. Conclusions: Cardiac CTA can be performed in the neonatal period free breathing and without sedation. Image quality is excellent, and there is high accuracy compared with surgical and catheterization findings at the time of intervention. [Copyright &y& Elsevier]

Increasing concerns about radiation dose have led CT manufacturers to further develop radiation dose reduction tools in the latest generation of CT scanners. These tools include automated tube current modulation, automated tube potential selection, and iterative reconstruction. This review details the principles underlying each of these 3 dose reduction utilities and their different permutations on each of the major vendors'' equipment. If available on the user''s equipment, all 3 of these tools should be used in conjunction to enable maximum radiation dose savings. [Copyright &y& Elsevier]

Background: High heart rates and radiation sensitivity have limited the use of coronary computed tomography angiography (CTA) in pediatric patients. Objective: A contemporary evaluation of image quality and reduction in radiation exposure with dual-source CT technology has not been reported in a large cohort of pediatric patients undergoing coronary angiography. Methods: Consecutive coronary CTA scans (n = 71) in 70 pediatric patients were retrospectively reviewed. Metoprolol was administered for heart rate control. Scans were divided by acquisition mode into 3 groups: retrospective electrocardiogram (ECG)–triggered spiral, prospective ECG-triggered, and prospective ECG-triggered high-pitch spiral scans. Heart rate, radiation dose, image quality, and diagnostic confidence were compared between groups. Results: Median decrease in heart rate with metoprolol was 24% ± 14%. Median effective age-adjusted radiation dose for the entire group was 0.97 ± 1.20 mSv. Retrospective ECG-triggered scans had a median dose of 1.71 ± 1.4 mSv, prospectively ECG-triggered scans had a median dose of 0.9 ± 1.1 mSv, and prospectively ECG-triggered high-pitch spiral scans had a median effective dose of 0.27 ± 0.4 mSv. The difference between groups was statistically significant (P < 0.05). The contrast-to-noise ratio and the image quality score were similar between groups. Conclusion: Dual-source coronary CTA with a β-blocker protocol uniformly achieves diagnostic coronary scans at a low radiation dose in pediatric patients. Image quality and diagnostic confidence are excellent for all scan modes in a wide spectrum of patients. [ABSTRACT FROM AUTHOR]

Background: Pediatric cardiac patients often undergo repeat diagnostic testing, resulting in relatively high cumulative medical radiation exposure. Low-dose CT scanning techniques used to decrease radiation exposure may result in reduced image quality. Objective: This study evaluates a prototype iterative reconstruction algorithm, sinogram-affirmed iterative reconstruction (SAFIRE), to determine the effect on qualitative and quantitative measures of image quality in pediatric cardiac CT datasets, compared with a standard weighted filtered back projection (wFBP) algorithm. Methods: Seventy-four datasets obtained on a 128-slice dual-source CT system were evaluated for image quality using both the wFBP and the prototype iterative reconstruction algorithm. Contrast, noise, contrast-to-noise ratio, signal-to-noise ratio, and qualitative image quality were compared between groups. Data were analyzed as medians and 25th and 75th percentiles, and groups were compared with the use of the Wilcoxon singed-rank test or k sample equality of medians test. Results: There was a 34% decrease in noise, a 41% increase in contrast-to-noise ratio, and a 56% increase in signal-to-noise ratio in the prototype iterative reconstruction, compared with wFBP. All differences were statistically significant (P < 0.001). Qualitative measures of image noise and noise texture were also improved in the iterative reconstruction group (P < 0.001 for both). Diagnostic confidence was similar between reconstruction techniques. Median scan dose length product was 15.5 mGy · cm. Conclusion: The prototype iterative reconstruction algorithm studied significantly reduces image noise and improves qualitative and quantitative measures of image quality in low-dose pediatric CT datasets, compared with standard wFBP. [ABSTRACT FROM AUTHOR]

Abstract A repeating pattern of multi-centennial-scale Holocene climate events has been widely (globally) documented, and they were termed Rapid Climate Change (RCC) events. Non-seasalt potassium ion (K+) series in Greenland ice cores provide well-constrained timings for the events, and a direct timing relationship has been inferred between these events and the frequency of northerly cold polar/continental air outbreaks over the eastern Mediterranean Sea through gaps in the mountain ranges along the northern margin of the basin. There also appears to be a remarkable timing agreement with major archaeological turnover events in the Aegean/Levantine region. Yet no physically consistent assessment exists for understanding the regional climatic impacts of the events around this critical region. We present a simple 2-dimensional Lagrangian model, which yields a broad suite of physically coherent simulations of the impacts of frequency changes in winter-time northerly air outbreaks over the Aegean/Levantine region. We validate this with existing reconstructions from palaeoclimate proxy data, with emphasis on well-validated sea-surface temperature reconstructions and a highly resolved cave speleothem stable oxygen isotope record from Lebanon. Given that the RCCs were clearly marked by negative sea surface temperature anomalies in the region, we find that the predominant climatic impacts of this winter-time mechanism were "cold and wet," in contrast with intercalated "warmer and more arid" conditions of non-RCC periods. More specifically, the RCCs are found to be periods of highly variable conditions, with an overall tendency toward cold and wet conditions with potential for flash flooding and for episodic snow-cover at low altitudes, at least in the lower-altitude (lower 1–1.5 km) regions of Crete and the Levant. The modelled winter-anomaly process cannot address underlying longer-term, astronomically forced trends, or the relatively warm and arid anomalies in between RCCs. The latter require further study, for example with respect to potential (summer-time?) extension of evaporative subtropical conditions over the region. Finally, our results imply that the "amount effect" observed in Levantine cave δ18O (and precipitation or drip-water δ18O) may not reflect the conventional concept related to temperature-dependent fractionation and Rayleigh distillation. Instead, it appears to arise from a complex and somewhat counter-intuitive mixing, in shifting proportionalities, between advected (external) and evaporated (Mediterranean) moisture. Highlights • New model simulations of frequency changes in winter-time cold air outbreaks over the Aegean-Levantine region. • Predominant impacts of these outbreaks were "cold and wet," in contrast with intercalated "warm and arid" conditions. • Outbreak maxima saw highly variable conditions, with increased potential for flash flooding and snow-cover at low altitudes. • Intercalated warm/arid intervals likely due to a other mode of regional climate variability; e.g., summer subtropical conditions. [ABSTRACT FROM AUTHOR]

Global climate variability during the late Quaternary is commonly investigated within the framework of the ‘bipolar seesaw’ pattern of asynchronous temperature variations in the northern and southern polar latitudes. The terrestrial hydrological response to this pattern in south-eastern Australia is not fully understood, as continuous, high-resolution, well-dated proxy records for the hydrological cycle in the region are sparse. Here we present a well-dated, highly resolved record of moisture balance spanning 30000–10000 calendar years before present (30–10 ka BP), based on x-ray fluorescence and organic carbon isotope (δ 13 C OM ) measurements of a sedimentary sequence from Lake Surprise in south-eastern Australia. The data provide a locally coherent record of the hydrological cycle. Elevated Si (reflecting windblown quartz and clays), and relatively high δ 13 C OM, indicate an extended period of relative aridity between 28 and 18.5 ka BP, interrupted by millennial-scale episodes of decreased Si and δ 13 C OM , suggesting increased moisture balance. This was followed by a rapid deglacial shift to low Si and δ 13 C OM at 18.5 ka BP, indicative of wetter conditions. We find that these changes are coeval with other records from south-eastern Australia and New Zealand, and use a Monte Carlo Empirical Orthogonal Function approach to extract a common trend from three high-resolution records. Our analyses suggest that drivers of the regional hydrological cycle have varied on multi-millennial time scales, in response to major shifts in global atmosphere-ocean dynamics during the last glacial-interglacial transition. Southern Ocean processes were the dominant control on hydroclimate during glacial times, via a strong influence of cold sea surface temperatures on moisture uptake and delivery onshore. Following the last deglaciation (around 18 ka BP), the southward migration of cold Southern Ocean fronts likely resulted in the establishment of conditions more like those of the present day. Millennial-scale variability in records from the region is dominated by a persistent ca. 2300-year periodicity, consistent with other records across the Southern Hemisphere mid-latitudes; however, this pervasive periodicity is not obviously linked to the ‘bipolar seesaw’ and the mechanism remains equivocal. [ABSTRACT FROM AUTHOR]

Abstract: Atmospheric mineral dust aerosols affect Earth’s radiative balance and are an important climate forcing and feedback mechanism. Dust is argued to have played an important role in past natural climate changes through glacial cycles, yet temporal and spatial dust variability remain poorly constrained, with scientific understanding of uncertainties associated with radiative perturbations due to mineral dust classified as “very low”. To advance understanding of the dust cycle, we present a high-resolution dust record from the Red Sea, sourced principally from Arabia, with a precise chronology relative to global sea level/ice volume variability. Our record correlates well with a high-resolution Asian dust record from the Chinese Loess Plateau. Importing our age model from the Red Sea to the Chinese Loess Plateau provides a first detailed millennial-scale age model for the Chinese loess, which has been notoriously difficult to date at this resolution and provides a basis for inter-regional correlation of Chinese dust records. We observe a high baseline of dust emissions from Arabia and China, even through interglacials, with strong superimposed millennial-scale variability. Conversely, the distal EPICA Dome C Antarctic ice core record, which is widely used to calculate the radiative impact of dust variations, appears biased to sharply delineated glacial/interglacial contrasts. Calculations based on this Antarctic dust record will therefore overestimate the radiative contrast of atmospheric dust loadings on glacial/interglacial timescales. Additional differences between Arabian/Asian and circum-Saharan records reveal that climate models could be improved by avoiding ‘global mean’ dust considerations and instead including large-scale regions with different dust source variability. [Copyright &y& Elsevier]

Multidetector computed tomographic angiography defines anatomy in complex congenital heart disease, but radiation exposure and general anesthesia requirements limit its application. The aim of this study was to compare radiation exposure, anesthesia use, and diagnostic accuracy between standard-pitch, single-source computed tomography and high-pitch, dual-source computed tomography for image quality and risk in a clinical pediatric population. Consecutive computed tomographic scans were evaluated in patients aged <2 years with complex congenital heart disease. Two groups were compared on the basis of standard- versus high-pitch scans. High-pitch scans were further divided into variable pitch (2.25 to 3.0) and highest pitch (3.4) groups. Image quality, radiation exposure, anesthesia use, and diagnostic confidence and accuracy were determined. Sixty-one scans were reviewed (29 at standard pitch, 32 at high pitch). Body surface area, scan length, and indications were similar. The median dose-length product for standard-pitch scans was 66 mGy · cm (range 29 to 372) compared to 7 mGy · cm (range 3 to 50) in all high-pitch scans. The median dose-length product was 28 mGy · cm (range 8 to 50) for variable high-pitch scans and 5 mGy · cm (range 3 to 12) for the highest fixed-pitch scans. Diagnostic confidence was similar, although high-pitch scans had higher image noise and lower contrast-to-noise ratios. All high-pitch scans were performed under sedation with free breathing, and all standard-pitch scans required general anesthesia. Diagnostic accuracy was 100% in the 2 groups, with 17 standard-pitch and 16 high-pitch patients undergoing procedural validation. In conclusion, high-pitch, dual-source computed tomography provides excellent diagnostic accuracy and markedly reduces radiation dose, although image quality is mildly reduced. [Copyright &y& Elsevier]

Studies of past glacial cycles yield critical information about climate and sea-level (ice-volume) variability, including the sensitivity of climate to radiative change, and impacts of crustal rebound on sea-level reconstructions for past interglacials. Here we identify significant differences between the last and penultimate glacial maxima (LGM and PGM) in terms of global volume and distribution of land ice, despite similar temperatures and radiative forcing. Our analysis challenges conventional views of relationships between global ice volume, sea level, seawater oxygen isotope values, and deep-sea temperature, and supports the potential presence of large floating Arctic ice shelves during the PGM. The existence of different glacial ‘modes’ calls for focussed research on the complex processes behind ice-age development. We present a glacioisostatic assessment to demonstrate how a different PGM ice-sheet configuration might affect sea-level estimates for the last interglacial. Results suggest that this may alter existing last interglacial sea-level estimates, which often use an LGM-like ice configuration, by several metres (likely upward). [ABSTRACT FROM AUTHOR]

Kawasaki disease (KD) is the leading cause of acquired coronary disease in children and may lead to subsequent myocardial ischemia and infarction. Because coronary computed tomographic angiography (CTA) is the most sensitive noninvasive test in patients with atherosclerosis, the aim of this study was to retrospectively evaluate coronary CTA performed in patients with KD for aneurysm, stenosis, and calcified and noncalcified coronary artery disease (CAD). Clinical histories and prior stress and imaging test results were reviewed. Thirty-two patients underwent coronary CTA for KD, and 385 coronary segments were evaluated. Twenty-three of 32 patients had ≥1 diseased coronary segment. There were 20 aneurysms, 7 lesions, and 75 segments (20%) with nonobstructive CAD (16% noncalcified, 2% calcified, and 2% mixed). All nonobstructive and obstructive CAD was in patients with histories of acute-phase coronary artery dilatation or aneurysm (echocardiographic z score 4 to 44), and were almost always associated with normal stress imaging test results on followup. No lesion or CAD was found in coronary computed tomographic angiographic studies performed in a control group referred for other indications (n = 32,422 segments evaluated). The median coronary computed tomographic angiographic dose-length product was 59 mGy cm (interquartile range 32 to 131), the median unadjusted radiation dose was 0.8 mSv (interquartile range 0.4 to 1.8), and the median age- and size-adjusted radiation dose was 1.3 mSv (interquartile range 0.7 to 2.3). In conclusion, high-risk patients with histories of KD had nonobstructive and obstructive CAD not visualized by other noninvasive imaging tests. In properly selected high-risk patients with KD, coronary CTA may identify a subset at increased risk for future coronary pathology who may benefit from medical therapy. [ABSTRACT FROM AUTHOR]