Fast kVp-Switching Dual Energy CT for PET Attenuation Correction

X-ray CT images are used routinely for attenuation correction in PET/CT systems. However, conventional CT-based attenuation correction (CTAC) can be inaccurate in regions containing iodine contrast agent. Dual-energy (DE) CT has the potential to improve the accuracy of attenuation correction in PET, but conventional DECT can suffer from motion artifacts. Recent X-ray CT systems can collect DE sinograms by rapidly switching the X-ray tube voltage between two levels for alternate projection views, reducing motion artifacts. The goal of this work is to study statistical methods for image reconstruction from both fast kVp-switching DE scans and from conventional dual-rotate DE scans in the context of CTAC for PET.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86003/1/Fessler244.pd

Quantitative Attenuation Correction for PET/CT Using Iterative Reconstruction of Low-Dose Dual-Energy CT

We present the results of using iterative reconstruction of dual-energy CT (DECT) to perform accurate CT-based attenuation correction (CTAC) for PET emission images. Current methods, such as bilinear scaling, introduce quantitative errors in the PET emission image for bone, metallic implants, and contrast agents. DECT has had limited use in the past for quantitative CT imaging due to increased patient dose and high noise levels in the decoupled CT basis-material images. Reconstruction methods that model the acquisition physics impose a significant computational burden due to the large image matrix size (typically 512 × 512). For CTAC, however, three factors make DECT feasible: (1) a smaller matrix is needed for the transmission image, which reduces the noise per pixel, (2) a smaller matrix significantly accelerates an iterative CT reconstruction algorithm, (3) the monoenergetic transmission image at 511 keV is the sum of the two decoupled basis-material images. Initial results using a 128 × 128 matrix size for a test object comprised of air, soft tissue, dense bone, and a mixture of tissue and bone demonstrate a significant reduction of bias using DECT (from 20% to ?0% for the tissue/bone mixture). FBP reconstructed images, however, have significant noise. Noise levels are reduced from ?8% to ?3% by the use of PWLS reconstruction.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/85861/1/Fessler203.pd

Purity of Gaussian states: measurement schemes and time-evolution in noisy channels

We present a systematic study of the purity for Gaussian states of single-mode continuous variable systems. We prove the connection of purity to observable quantities for these states, and show that the joint measurement of two conjugate quadratures is necessary and sufficient to determine the purity at any time. The statistical reliability and the range of applicability of the proposed measurement scheme is tested by means of Monte Carlo simulated experiments. We then consider the dynamics of purity in noisy channels. We derive an evolution equation for the purity of general Gaussian states both in thermal and squeezed thermal baths. We show that purity is maximized at any given time for an initial coherent state evolving in a thermal bath, or for an initial squeezed state evolving in a squeezed thermal bath whose asymptotic squeezing is orthogonal to that of the input state.Comment: 9 Pages, 6 Figures; minor errors correcte

Alzheimer's Disease and Small Vessel Disease Differentially Affect White Matter Microstructure

OBJECTIVE: Alzheimer's disease (AD) and cerebral small vessel disease (cSVD), the two most common causes of dementia, are characterized by white matter (WM) alterations diverging from the physiological changes occurring in healthy aging. Diffusion tensor imaging (DTI) is a valuable tool to quantify WM integrity non-invasively and identify the determinants of such alterations. Here, we investigated main effects and interactions of AD pathology, APOE-ε4, cSVD, and cardiovascular risk on spatial patterns of WM alterations in non-demented older adults.METHODS: Within the prospective European Prevention of Alzheimer's Dementia study, we selected 606 participants (64.9 ± 7.2 years, 376 females) with baseline cerebrospinal fluid samples of amyloid β 1-42 and p-Tau 181 and MRI scans, including DTI scans. Longitudinal scans (mean follow-up time = 1.3 ± 0.5 years) were obtained in a subset (n = 223). WM integrity was assessed by extracting fractional anisotropy and mean diffusivity in relevant tracts. To identify the determinants of WM disruption, we performed a multimodel inference to identify the best linear mixed-effects model for each tract. RESULTS: AD pathology, APOE-ε4, cSVD burden, and cardiovascular risk were all associated with WM integrity within several tracts. While limbic tracts were mainly impacted by AD pathology and APOE-ε4, commissural, associative, and projection tract integrity was more related to cSVD burden and cardiovascular risk. AD pathology and cSVD did not show any significant interaction effect.INTERPRETATION: Our results suggest that AD pathology and cSVD exert independent and spatially different effects on WM microstructure, supporting the role of DTI in disease monitoring and suggesting independent targets for preventive medicine approaches.</p

Novel Textbook Outcomes following emergency laparotomy:Delphi exercise

Background: Textbook outcomes are composite outcome measures that reflect the ideal overall experience for patients. There are many of these in the elective surgery literature but no textbook outcomes have been proposed for patients following emergency laparotomy. The aim was to achieve international consensus amongst experts and patients for the best Textbook Outcomes for non-trauma and trauma emergency laparotomy. Methods: A modified Delphi exercise was undertaken with three planned rounds to achieve consensus regarding the best Textbook Outcomes based on the category, number and importance (Likert scale of 1–5) of individual outcome measures. There were separate questions for non-trauma and trauma. A patient engagement exercise was undertaken after round 2 to inform the final round. Results: A total of 337 participants from 53 countries participated in all three rounds of the exercise. The final Textbook Outcomes were divided into ‘early’ and ‘longer-term’. For non-trauma patients the proposed early Textbook Outcome was ‘Discharged from hospital without serious postoperative complications (Clavien–Dindo ≥ grade III; including intra-abdominal sepsis, organ failure, unplanned re-operation or death). For trauma patients it was ‘Discharged from hospital without unexpected transfusion after haemostasis, and no serious postoperative complications (adapted Clavien–Dindo for trauma ≥ grade III; including intra-abdominal sepsis, organ failure, unplanned re-operation on or death)’. The longer-term Textbook Outcome for both non-trauma and trauma was ‘Achieved the early Textbook Outcome, and restoration of baseline quality of life at 1 year’. Conclusion: Early and longer-term Textbook Outcomes have been agreed by an international consensus of experts for non-trauma and trauma emergency laparotomy. These now require clinical validation with patient data.</p

Investigating Protostellar Accretion-Driven Outflows Across the Mass Spectrum: JWST NIRSpec IFU 3-5~μ\mum Spectral Mapping of Five Young Protostars

Investigating Protostellar Accretion (IPA) is a Cycle 1 JWST program using the NIRSpec+MIRI IFUs to obtain 2.9--28 $\mu$m spectral cubes of five young protostars with luminosities of 0.2 to 10,000 L$_{\odot}$ in their primary accretion phase. This paper introduces the NIRSpec 2.9--5.3 $\mu$m data of the inner 840-9000 au with spatial resolutions from 28-300 au. The spectra show rising continuum emission, deep ice absorption, emission from H$_{2}$, H~I, and [Fe~II], and the CO fundamental series in emission and absorption. Maps of the continuum emission show scattered light cavities for all five protostars. In the cavities, collimated jets are detected in [Fe~II] for the four $< 320$~L$_{\odot}$ protostars, two of which are additionally traced in Br-$\alpha$. Knots of [Fe~II] emission are detected toward the most luminous protostar, and knots of [FeII] emission with dynamical times of $< 30$~yrs are found in the jets of the others. While only one jet is traced in H$_2$, knots of H$_2$ and CO are detected in the jets of four protostars. H$_2$ is seen extending through the cavities showing they are filled by warm molecular gas. Bright H$_2$ emission is seen along the walls of a single cavity, while in three cavities, narrow shells of H$_2$ emission are found, one of which has an [Fe~II] knot at its apex. These data show cavities containing collimated jets traced in atomic/ionic gas surrounded by warm molecular gas in a wide-angle wind and/or gas accelerated by bow shocks in the jets.Comment: 30 pages, 11 figure

PET-BIDS, an extension to the brain imaging data structure for positron emission tomography

The Brain Imaging Data Structure (BIDS) is a standard for organizing and describing neuroimaging datasets, serving not only to facilitate the process of data sharing and aggregation, but also to simplify the application and development of new methods and software for working with neuroimaging data. Here, we present an extension of BIDS to include positron emission tomography (PET) data, also known as PET-BIDS, and share several open-access datasets curated following PET-BIDS along with tools for conversion, validation and analysis of PET-BIDS datasets

Viewing Loved Faces Inhibits Defense Reactions: A Health-Promotion Mechanism?

We have known for decades that social support is associated with positive health outcomes. And yet, the neurophysiological mechanisms underlying this association remain poorly understood. The link between social support and positive health outcomes is likely to depend on the neurophysiological regulatory mechanisms underlying reward and defensive reactions. The present study examines the hypothesis that emotional social support (love) provides safety cues that activate the appetitive reward system and simultaneously inhibit defense reactions. Using the startle probe paradigm, 54 undergraduate students (24 men) viewed black and white photographs of loved (romantic partner, father, mother, and best friend), neutral (unknown), and unpleasant (mutilated) faces. Eye–blink startle, zygomatic major activity, heart rate, and skin conductance responses to the faces, together with subjective ratings of valence, arousal, and dominance, were obtained. Viewing loved faces induced a marked inhibition of the eye-blink startle response accompanied by a pattern of zygomatic, heart rate, skin conductance, and subjective changes indicative of an intense positive emotional response. Effects were similar for men and women, but the startle inhibition and the zygomatic response were larger in female participants. A comparison between the faces of the romantic partner and the parent who shares the partner’s gender further suggests that this effect is not attributable to familiarity or arousal. We conclude that this inhibitory capacity may contribute to the health benefits associated with social support.This research was funded by grant P07-SEJ-02964 from Junta de Andalucía (Spain)

Association of polygenic score for major depression with response to lithium in patients with bipolar disorder

Lithium is a first-line medication for bipolar disorder (BD), but only one in three patients respond optimally to the drug. Since evidence shows a strong clinical and genetic overlap between depression and bipolar disorder, we investigated whether a polygenic susceptibility to major depression is associated with response to lithium treatment in patients with BD. Weighted polygenic scores (PGSs) were computed for major depression (MD) at different GWAS p value thresholds using genetic data obtained from 2586 bipolar patients who received lithium treatment and took part in the Consortium on Lithium Genetics (ConLi+Gen) study. Summary statistics from genome-wide association studies in MD (135,458 cases and 344,901 controls) from the Psychiatric Genomics Consortium (PGC) were used for PGS weighting. Response to lithium treatment was defined by continuous scores and categorical outcome (responders versus non-responders) using measurements on the Alda scale. Associations between PGSs of MD and lithium treatment response were assessed using a linear and binary logistic regression modeling for the continuous and categorical outcomes, respectively. The analysis was performed for the entire cohort, and for European and Asian sub-samples. The PGSs for MD were significantly associated with lithium treatment response in multi-ethnic, European or Asian populations, at various p value thresholds. Bipolar patients with a low polygenic load for MD were more likely to respond well to lithium, compared to those patients with high polygenic load [lowest vs highest PGS quartiles, multi-ethnic sample: OR = 1.54 (95% CI: 1.18–2.01) and European sample: OR = 1.75 (95% CI: 1.30–2.36)]. While our analysis in the Asian sample found equivalent effect size in the same direction: OR = 1.71 (95% CI: 0.61–4.90), this was not statistically significant. Using PGS decile comparison, we found a similar trend of association between a high genetic loading for MD and lower response to lithium. Our findings underscore the genetic contribution to lithium response in BD and support the emerging concept of a lithium-responsive biotype in BD