A mathematical model for velocity-selective arterial spin labeling

PURPOSE

To present a theoretical framework that rigorously defines and analyzes key concepts and quantities for velocity selective arterial spin labeling (VSASL).

THEORY AND METHODS

An expression for the VSASL arterial delivery function is derived based on (1) labeling and saturation profiles as a function of velocity and (2) physiologically plausible approximations of changes in acceleration and velocity across the vascular system. The dependence of labeling efficiency on the amplitude and effective bolus width of the arterial delivery function is defined. Factors that affect the effective bolus width are examined, and timing requirements to minimize quantitation errors are derived.

RESULTS

The model predicts that a flow-dependent negative bias in the effective bolus width can occur when velocity selective inversion (VSI) is used for the labeling module and velocity selective saturation (VSS) is used for the vascular crushing module. The bias can be minimized by choosing a nominal labeling cutoff velocity that is lower than the nominal cutoff velocity of the vascular crushing module.

CONCLUSION

The elements of the model are specified in a general fashion such that future advances can be readily integrated. The model can facilitate further efforts to understand and characterize the performance of VSASL and provide critical theoretical insights that can be used to design future experiments and develop novel VSASL approaches.

Metabolic energetics underlying attractors in neural models

Neural population modeling, including the role of neural attractors, is a promising tool for understanding many aspects of brain function. We propose a modeling framework to connect the abstract variables used in modeling to recent cellular-level estimates of the bioenergetic costs of different aspects of neural activity, measured in ATP consumed per second per neuron. Based on recent work, an empirical reference for brain ATP use for the awake resting brain was estimated as ∼2 × 109 ATP/s-neuron across several mammalian species. The energetics framework was applied to the Wilson-Cowan (WC) model of two interacting populations of neurons, one excitatory (E) and one inhibitory (I). Attractors were considered to exhibit steady-state behavior and limit cycle behavior, both of which end when the excitatory stimulus ends, and sustained activity that persists after the stimulus ends. The energy cost of limit cycles, with oscillations much faster than the average neuronal firing rate of the population, is tracked more closely with the firing rate than the limit cycle frequency. Self-sustained firing driven by recurrent excitation, though, involves higher firing rates and a higher energy cost. As an example of a simple network in which each node is a WC model, a combination of three nodes can serve as a flexible circuit element that turns on with an oscillating output when input passes a threshold and then persists after the input ends (an "on-switch"), with moderate overall ATP use. The proposed framework can serve as a guide for anchoring neural population models to plausible bioenergetics requirements.NEW & NOTEWORTHY This work bridges two approaches for understanding brain function: cellular-level studies of the metabolic energy costs of different aspects of neural activity and neural population modeling, including the role of neural attractors. The proposed modeling framework connects energetic costs, in ATP consumed per second per neuron, to the more abstract variables used in neural population modeling. In particular, this work anchors potential neural attractors to physiologically plausible bioenergetics requirements.

A176 ASSOCIATIONS OF ANTIBIOTICS, HORMONAL THERAPIES, ORAL CONTRACEPTIVES, AND LONG-TERM NSAIDS WITH INFLAMMATORY BOWEL DISEASE: RESULTS FROM THE PROSPECTIVE URBAN RURAL EPIDEMIOLOGY (PURE) STUDY

Background

The pathogenesis of inflammatory bowel disease (IBD) which includes Crohn’s disease (CD) and ulcerative colitis (UC), is believed to involve activation of the intestinal immune system in response to the gut microbiome among genetically susceptible hosts. IBD has been historically regarded as a disease of developed nations, though in the past two decades there has been a reported shift in the epidemiological pattern of disease. High-income nations with known high prevalence of disease are seeing a stabilization of incident cases, while a rapid rise of incident IBD is being observed in developing nations. This suggests that environmental exposures may play a role in mediating the risk of developing IBD. The potential environmental determinants of IBD across various regions is vast, though medications have been increasingly recognized as one broad category of risk factors.

Purpose

Several medications have been considered to contribute to the etiology of IBD. This study assessed the association between medication use and risk of developing IBD using the Prospective Urban Rural Epidemiology (PURE) cohort.

Method

This was a prospective cohort study of 133,137 individuals between the ages of 20-80 from 24 countries. Country-specific validated questionnaires documented baseline and follow-up medication use. Participants were followed prospectively at least every 3 years. The main outcome was development of IBD, including CD and UC. Short-term (baseline but not follow-up use) and long-term use (baseline and subsequent follow-up use) was evaluated. Results are presented as adjusted odds ratios (aOR) with 95% confidence intervals (CI).

Result(s)

During the median follow-up of 11.0 years [interquartile range (IQR) 9.2-12.2], we recorded 571 incident cases of IBD (143 CD and 428 UC). Higher risk of incident IBD was associated with baseline antibiotic use [aOR: 2.81 (95% CI: 1.67-4.73), p=0.0001] and hormonal medication use [aOR: 4.43 (95% CI: 1.78-11.01), p=0.001]. Among females, previous or current oral contraceptive use was also associated with IBD development [aOR: 2.17 (95% CI: 1.70-2.77), p=5.02E-10]. NSAID users were also observed to have increased risk of IBD [aOR: 1.80 (95% CI: 1.23-2.64), p=0.002], which was driven by long-term users [aOR: 5.58 (95% CI: 2.26-13.80), p<0.001]. All significant results were consistent in direction for CD and UC with low heterogeneity.

Conclusion(s)

Antibiotics, hormonal medications, oral contraceptives, and long-term NSAID use were associated with increased odds of incident IBD after adjustment for covariates.

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Salim Yusuf is supported by the Heart & Stroke Foundation/Marion W. Burke Chair in Cardiovascular Disease. The PURE Study is an investigator-initiated study funded by the Population Health Research Institute, the Canadian Institutes of Health Research (CIHR), Heart and Stroke Foundation of Ontario, support from CIHR’s Strategy for Patient Oriented Research (SPOR) through the Ontario SPOR Support Unit, as well as the Ontario Ministry of Health and Long-Term Care and through unrestricted grants from several pharmaceutical companies, with major contributions from AstraZeneca (Canada), Sanofi-Aventis (France and Canada), Boehringer Ingelheim (Germany and Canada), Servier, and GlaxoSmithkline, and additional contributions from Novartis and King Pharma and from various national or local organisations in participating countries; these include: Argentina: Fundacion ECLA; Bangladesh: Independent University, Bangladesh and Mitra and Associates; Brazil: Unilever Health Institute, Brazil; Canada: Public Health Agency of Canada and Champlain Cardiovascular Disease Prevention Network; Chile: Universidad de la Frontera; China: National Center for Cardiovascular Diseases; Colombia: Colciencias, grant number 6566-04-18062; India: Indian Council of Medical Research; Malaysia: Ministry of Science, Technology and Innovation of Malaysia, grant numbers 100 -IRDC/BIOTEK 16/6/21 (13/2007) and 07-05-IFN-BPH 010, Ministry of Higher Education of Malaysia grant number 600 -RMI/LRGS/5/3 (2/2011), Universiti Teknologi MARA, Universiti Kebangsaan Malaysia (UKM-Hejim-Komuniti-15-2010); occupied Palestinian territory: the UN Relief and Works Agency for Palestine Refugees in the Near East, occupied Palestinian territory; International Development Research Centre, Canada; Philippines: Philippine Council for Health Research & Development; Poland: Polish Ministry of Science and Higher Education grant number 290/W-PURE/2008/0, Wroclaw Medical University; Saudi Arabia: the Deanship of Scientific Research at King Saud University, Riyadh, Saudi Arabia (research group number RG -1436-013); South Africa: the North-West University, SANPAD (SA and Netherlands Programme for Alternative Development), National Research Foundation, Medical Research Council of SA, The SA Sugar Association (SASA), Faculty of Community and Health Sciences (UWC); Sweden: grants from the Swedish state under the Agreement concerning research and education of doctors; the Swedish Heart and Lung Foundation; the Swedish Research Council; the Swedish Council for Health, Working Life and Welfare, King Gustaf V’s and Queen Victoria Freemasons Foundation, AFA Insurance, Swedish Council for Working Life and Social Research, Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning, grant from the Swedish State under the Läkar Utbildnings Avtalet agreement, and grant from the Västra Götaland Region; Turkey: Metabolic Syndrome Society, AstraZeneca, Turkey, Sanofi Aventis, Turkey; United Arab Emirates (UAE): Sheikh Hamdan Bin Rashid Al Maktoum Award For Medical Sciences and Dubai Health Authority, Dubai UAE.

Disclosure of Interest

C. Pray: None Declared, N. Narula Grant / Research support from: Neeraj Narula holds a McMaster University Department of Medicine Internal Career Award. Neeraj Narula has received honoraria from Janssen, Abbvie, Takeda, Pfizer, Merck, and Ferring, E. C. Wong: None Declared, J. K. Marshall Grant / Research support from: John K. Marshall has received honoraria from Janssen, AbbVie, Allergan, Bristol-Meyer-Squibb, Ferring, Janssen, Lilly, Lupin, Merck, Pfizer, Pharmascience, Roche, Shire, Takeda and Teva., S. Rangarajan: None Declared, S. Islam: None Declared, A. Bahonar: None Declared, K. F. Alhabib: None Declared, A. Kontsevaya: None Declared, F. Ariffin: None Declared, H. U. Co: None Declared, W. Al Sharief: None Declared, A. Szuba: None Declared, A. Wielgosz: None Declared, M. L. Diaz: None Declared, R. Yusuf: None Declared, L. Kruger: None Declared, B. Soman: None Declared, Y. Li: None Declared, C. Wang: None Declared, L. Yin: None Declared, M. Erkin: None Declared, F. Lanas: None Declared, K. Davletov: None Declared, A. Rosengren: None Declared, P. Lopez-Jaramillo: None Declared, R. Khatib: None Declared, A. Oguz: None Declared, R. Iqbal: None Declared, K. Yeates: None Declared, Á. Avezum: None Declared, W. Reinisch Consultant of: Speaker for Abbott Laboratories, Abbvie, Aesca, Aptalis, Astellas, Centocor, Celltrion, Danone Austria, Elan, Falk Pharma GmbH, Ferring, Immundiagnostik, Mitsubishi Tanabe Pharma Corporation, MSD, Otsuka, PDL, Pharmacosmos, PLS Education, Schering-Plough, Shire, Takeda, Therakos, Vifor, Yakult, Consultant for Abbott Laboratories, Abbvie, Aesca, Algernon, Amgen, AM Pharma, AMT, AOP Orphan, Arena Pharmaceuticals, Astellas, Astra Zeneca, Avaxia, Roland Berger GmBH, Bioclinica, Biogen IDEC, Boehringer-Ingelheim, Bristol-Myers Squibb, Cellerix, Chemocentryx, Celgene, Centocor, Celltrion, Covance, Danone Austria, DSM, Elan, Eli Lilly, Ernest & Young, Falk Pharma GmbH, Ferring, Galapagos, Genentech, Gilead, Grünenthal, ICON, Index Pharma, Inova, Janssen, Johnson & Johnson, Kyowa Hakko Kirin Pharma, Lipid Therapeutics, LivaNova, Mallinckrodt, Medahead, MedImmune, Millenium, Mitsubishi Tanabe Pharma Corporation, MSD, Nash Pharmaceuticals, Nestle, Nippon Kayaku, Novartis, Ocera, Omass, Otsuka, Parexel, PDL, Periconsulting, Pharmacosmos, Philip Morris Institute, Pfizer, Procter & Gamble, Prometheus, Protagonist, Provention, Robarts Clinical Trial, Sandoz, Schering-Plough, Second Genome, Seres Therapeutics, Setpointmedical, Sigmoid, Sublimity, Takeda, Therakos, Theravance, Tigenix, UCB, Vifor, Zealand, Zyngenia, and 4SC, Advisory board member for Abbott Laboratories, Abbvie, Aesca, Amgen, AM Pharma, Astellas, Astra Zeneca, Avaxia, Biogen IDEC, Boehringer-Ingelheim, Bristol-Myers Squibb, Cellerix, Chemocentryx, Celgene, Centocor, Celltrion, Danone Austria, DSM, Elan, Ferring, Galapagos, Genentech, Grünenthal, Inova, Janssen, Johnson & Johnson, Kyowa Hakko Kirin Pharma, Lipid Therapeutics, MedImmune, Millenium, Mitsubishi Tanabe Pharma Corporation, MSD, Nestle, Novartis, Ocera, Otsuka, PDL, Pharmacosmos, Pfizer, Procter & Gamble, Prometheus, Sandoz, Schering-Plough, Second Genome, Setpointmedical, Takeda, Therakos, Tigenix, UCB, Zealand, Zyngenia, and 4SC, P. Moayyedi: None Declared, S. Yusuf: None Declared

Velocity-selective arterial spin labeling perfusion MRI: A review of the state of the art and recommendations for clinical implementation

This review article provides an overview of the current status of velocity-selective arterial spin labeling (VSASL) perfusion MRI and is part of a wider effort arising from the International Society for Magnetic Resonance in Medicine (ISMRM) Perfusion Study Group. Since publication of the 2015 consensus paper on arterial spin labeling (ASL) for cerebral perfusion imaging, important advancements have been made in the field. The ASL community has, therefore, decided to provide an extended perspective on various aspects of technical development and application. Because VSASL has the potential to become a principal ASL method because of its unique advantages over traditional approaches, an in-depth discussion was warranted. VSASL labels blood based on its velocity and creates a magnetic bolus immediately proximal to the microvasculature within the imaging volume. VSASL is, therefore, insensitive to transit delay effects, in contrast to spatially selective pulsed and (pseudo-) continuous ASL approaches. Recent technical developments have improved the robustness and the labeling efficiency of VSASL, making it a potentially more favorable ASL approach in a wide range of applications where transit delay effects are of concern. In this review article, we (1) describe the concepts and theoretical basis of VSASL; (2) describe different variants of VSASL and their implementation; (3) provide recommended parameters and practices for clinical adoption; (4) describe challenges in developing and implementing VSASL; and (5) describe its current applications. As VSASL continues to undergo rapid development, the focus of this review is to summarize the fundamental concepts of VSASL, describe existing VSASL techniques and applications, and provide recommendations to help the clinical community adopt VSASL.

VESPA ASL: VElocity and SPAtially Selective Arterial Spin Labeling

PURPOSE

Spatially selective arterial spin labeling (ASL) perfusion MRI is sensitive to arterial transit times (ATT) that can result in inaccurate perfusion quantification when ATTs are long. Velocity-selective ASL is robust to this effect because blood is labeled within the imaging region, allowing immediate label delivery. However, velocity-selective ASL cannot characterize ATTs, which can provide important clinical information. Here, we introduce a novel pulse sequence, called VESPA ASL, that combines velocity-selective and pseudo-continuous ASL to simultaneously label different pools of arterial blood for robust cerebral blood flow (CBF) and ATT measurement.

METHODS

The VESPA ASL sequence is similar to velocity-selective ASL, but the velocity-selective labeling is made spatially selective, and pseudo-continuous ASL is added to fill the inflow time. The choice of inflow time and other sequence settings were explored. VESPA ASL was compared to multi-delay pseudo-continuous ASL and velocity-selective ASL through simulations and test-retest experiments in healthy volunteers.

RESULTS

VESPA ASL is shown to accurately measure CBF in the presence of long ATTs, and ATTs < TI can also be measured. Measurements were similar to established ASL techniques when ATT was short. When ATT was long, VESPA ASL measured CBF more accurately than multi-delay pseudo-continuous ASL, which tended to underestimate CBF.

CONCLUSION

VESPA ASL is a novel and robust approach to simultaneously measure CBF and ATT and offers important advantages over existing methods. It fills an important clinical need for noninvasive perfusion and transit time imaging in vascular diseases with delayed arterial transit.

Distributed Phase Oscillatory Excitation Efficiently Produces Attractors Using Spike-Timing-Dependent Plasticity

The brain is thought to represent information in the form of activity in distributed groups of neurons known as attractors. We show here that in a randomly connected network of simulated spiking neurons, periodic stimulation of neurons with distributed phase offsets, along with standard spike-timing-dependent plasticity (STDP), efficiently creates distributed attractors. These attractors may have a consistent ordered firing pattern or become irregular, depending on the conditions. We also show that when two such attractors are stimulated in sequence, the same STDP mechanism can create a directed association between them, forming the basis of an associative network. We find that for an STDP time constant of 20 ms, the dependence of the efficiency of attractor creation on the driving frequency has a broad peak centered around 8 Hz. Upon restimulation, the attractors self-oscillate, but with an oscillation frequency that is higher than the driving frequency, ranging from 10 to 100 Hz.

Predictors of the Use of Mineralocorticoid Receptor Antagonists in Patients With Left Ventricular Dysfunction Post-ST-Segment-Elevation Myocardial Infarction

Background

Guidelines recommend mineralocorticoid receptor antagonist (MRA) use in patients with left ventricular ejection fraction ≤40% following a myocardial infarction plus heart failure or diabetes mellitus, based on mortality benefit in the EPHESUS (Eplerenone Post‐Acute Myocardial Infarction Heart Failure Efficacy and Survival Study) trial. The objective of this study was to evaluate the real‐world utilization of MRAs for patients with ST‐segment–elevation myocardial infarction (STEMI) with left ventricular dysfunction.

Methods and Results

The prospective, population‐based, Vancouver Coastal Health Authority STEMI database was linked with local outpatient cardiology records from 2007 to 2018. EPHESUS criteria were used to define post‐STEMI MRA eligibility (left ventricular ejection fraction ≤40% plus clinical heart failure or diabetes mellitus, and no dialysis‐dependent renal dysfunction). The primary outcome was MRA prescription among eligible patients at discharge and the secondary outcome was MRA prescription within 3 months postdischarge. Of 2691 patients with STEMI, 317 (12%) were MRA eligible, and 70 (22%) eligible patients were prescribed an MRA at discharge. Among eligible patients with no MRA at discharge, 12/126 (9.5%) with documented postdischarge follow‐up were prescribed an MRA within 3 months. In multivariable analysis, left ventricular ejection fraction (odds ratio [OR], 1.55 per 5% left ventricular ejection fraction decrease; 95% CI, 1.26–1.90) and calendar year (OR, 1.23 per year, 95% CI, 1.11–1.37) were associated with MRA prescription at discharge. Other prespecified variables were not associated with MRA prescription.

Conclusions

In this contemporary STEMI cohort, only 1 in 4 MRA‐eligible patients were prescribed an MRA within 3 months following hospitalization despite high‐quality evidence for use. Novel decision‐support tools are required to optimize pharmacotherapy decisions during hospitalization and follow‐up to target this gap in post‐STEMI care.

Awake Mouse Imaging: From Two-Photon Microscopy to Blood Oxygen Level-Dependent Functional Magnetic Resonance Imaging

BACKGROUND

Functional magnetic resonance imaging (fMRI) in awake behaving mice is well positioned to bridge the detailed cellular-level view of brain activity, which has become available owing to recent advances in microscopic optical imaging and genetics, to the macroscopic scale of human noninvasive observables. However, though microscopic (e.g., two-photon imaging) studies in behaving mice have become a reality in many laboratories, awake mouse fMRI remains a challenge. Owing to variability in behavior among animals, performing all types of measurements within the same subject is highly desirable and can lead to higher scientific rigor.

METHODS

We demonstrated blood oxygenation level-dependent fMRI in awake mice implanted with long-term cranial windows that allowed optical access for microscopic imaging modalities and optogenetic stimulation. We started with two-photon imaging of single-vessel diameter changes (n = 1). Next, we implemented intrinsic optical imaging of blood oxygenation and flow combined with laser speckle imaging of blood flow obtaining a mesoscopic picture of the hemodynamic response (n = 16). Then we obtained corresponding blood oxygenation level-dependent fMRI data (n = 5). All measurements could be performed in the same mice in response to identical sensory and optogenetic stimuli.

RESULTS

The cranial window did not deteriorate the quality of fMRI and allowed alternation between imaging modalities in each subject.

CONCLUSIONS

This report provides a proof of feasibility for multiscale imaging approaches in awake mice. In the future, this protocol could be extended to include complex cognitive behaviors translatable to humans, such as sensory discrimination or attention.

Rehearsal in Spatial Working Memory: Evidence From Neuroimaging

A variety of biological evidence has identified a frontal-parietal circuit underlying spatial working memory for visual stimuli. But the question remains, how do these neural regions accomplish the goal of maintaining location information on-line? We tested the hypothesis that the active rehearsal of spatial information in working memory is accomplished by means of focal shifts of spatial selective attention to memorized locations. Spatial selective attention has been shown to cause changes in the early visual processing of stimuli that appear in attended locations. Thus, the hypothesis of attention-based rehearsal predicts similar modulations of visual processing at memorized locations. We used functional magnetic resonance imaging to observe posterior visual activations during the performance of a spatial working memory task. In line with the hypothesis, spatial rehearsal led to enhanced activation in the early visual areas contralateral to the memorized locations.

Abstract P1-10-22: Evaluating the incidence of supportive care referrals generated using patient reported data from the Athena health questionnaire system

Background

Patients at risk for or diagnosed with breast cancer have many symptoms and need for supportive care services. As part of the Athena Breast Health Network (a University of California-wide collaboration), the UCSF Breast Care Center (BCC) has incorporated an electronic health questionnaire system (HQS) prior to new patient and follow-up clinic visits, allowing patients to provide information on their personal health and family history, physical and psychological symptoms, and lifestyle. Based on these patient-reported outcomes (PRO), automated referrals for services including genetic counseling, psycho-oncology, social work, fertility preservation, and smoking cessation are generated. Algorithms defining thresholds to trigger these referrals were developed by clinicians and supportive care providers to proactively meet patients' needs.

Objectives

To evaluate the incidence and outcomes of supportive care referrals based on existing algorithms, and identify reasons for non-utilization of the services offered. The ultimate goal for this evaluation is to modify the existing algorithms to better meet patients' needs.

Methods

Patients initiating care at the UCSF BCC are invited by email to complete an HQS that provides information relevant to their clinical care. Patients sign an electronic consent, agreeing to have their PRO stored and accessed for research purposes. Family history, health behaviors, desired services, and responses to National Cancer Institute Patient Reported Outcomes Measurement Information System (PROMIS) items are processed through algorithms, generating referrals based on defined thresholds. A clinician summary report is generated and scanned into the electronic medical record (EMR), identifying services for which the patient has met thresholds. Referrals are sent to the clinician as pended orders through the EMR. Once signed by the care provider (physician or nurse practitioner), the order is routed through the EMR to the appropriate service and the patient is offered a visit or phone consultation when appropriate.

Results

Between 1/1/14 and 12/31/14, 1297 patients initiating care at the UCSF BCC completed an HQS prior to their clinic visit. 1108 patients (85.4%) agreed to have their data used for research. 623 patients (56.2%) were referred to at least one supportive care service. The table below summarizes the percentage of patients who met the defined referral thresholds:

Referrals Made, 2014Referral TypeNumber of ReferralsPercent of Patients Referred (n=1108)Genetic Counseling Services44340.0%Psychological Services25723.2%Social Work13712.4%Smoking Cessation343.1%Fertility Preservation292.6%

Ongoing analyses are underway to determine the percentage of patients who received services, explore barriers to accessing these services, and evaluate patients' preferences regarding provision of services in alternate formats, including webinars, online content, and group sessions.

Conclusions

Effective use of PRO identifies a high percentage of patients in need of supportive care services. Through analysis of utilization of services based on our existing thresholds, we hope to optimize our algorithms to better serve our patients' needs throughout the continuum of cancer care.

Citation Format: Wong EC, Kaplan CP, Shumay DM, Leykin Y, Etzel KA, Stover Fiscalini A, van't Veer LJ, Esserman LJ, Melisko ME. Evaluating the incidence of supportive care referrals generated using patient reported data from the Athena health questionnaire system. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P1-10-22.

Wedge-shaped slice-selective adiabatic inversion pulse for controlling temporal width of bolus in pulsed arterial spin labeling

PURPOSE

In pulsed arterial spin labeling (PASL) methods, arterial blood is labeled by inverting a slab with uniform thickness, resulting in different temporal widths of boluses in vessels with different flow velocities. This limits the temporal resolution and signal-to-noise ratio (SNR) efficiency gains in PASL-based methods intended for high temporal resolution and SNR efficiency, such as turbo-ASL and turbo-QUASAR.

THEORY AND METHODS

A novel wedge-shaped (WS) adiabatic inversion pulse is developed by adding in-plane gradient pulses to a slice-selective (SS) adiabatic inversion pulse to linearly modulate the inversion thicknesses at different locations while maintaining the adiabatic properties of the original pulse. A hyperbolic secant (HS)-based WS inversion pulse was implemented. Its performance was tested in simulations and in phantom and human experiments and compared with an SS HS inversion pulse.

RESULTS

Compared with the SS inversion pulse, the WS inversion pulse was capable of inducing different inversion thicknesses at different locations. It could be adjusted to generate a uniform temporal width of boluses in arteries at locations with different flow velocities.

CONCLUSION

The WS inversion pulse can be used to control the temporal widths of labeled boluses in PASL experiments. This should benefit PASL experiments by maximizing labeling duty cycle and improving temporal resolution and SNR efficiency. Magn Reson Med 76:838-847, 2016. © 2015 Wiley Periodicals, Inc.

Moderate intensity exercise mediates comparable increases in exhaled chloride as albuterol in individuals with cystic fibrosis

RATIONALE

Despite the demonstrated advantageous systemic changes in response to regular exercise for individuals with cystic fibrosis (CF), exercise is still viewed as an elective rather than a vital component of therapy, and it is likely that these benefits extend to and are partially mediated by exercise-induced changes in ion regulation.

OBJECTIVE

We sought to determine if exercise could provide comparable improvements in ion regulation in the CF lung as albuterol, measured using exhaled breath condensate (EBC) collection and nasal potential difference (NPD).

METHODS

Fourteen CF (13-42 yrs.) and sixteen healthy (18-42 yrs.) subjects completed a randomized crossover study of albuterol and submaximal exercise. EBC was collected at baseline, 30- and 60-min post-albuterol administration, and at baseline and during three separate 15 min cycling exercise bouts at low, moderate, and vigorous intensity (25, 50 and 65% of the maximum workload, respectively). NPD was performed at 30- and 80-min post albuterol or following moderate and vigorous intensity exercise.

RESULTS

CF subjects had lower EBC Cl(-), but no difference in EBC Na(+) at baseline when compared to healthy subjects. EBC Cl(-) increased four-fold with moderate exercise which was similar to that seen 60-min post albuterol administration for CF subjects. Neither exercise nor albuterol altered EBC Na(+). The change in NPD voltage with amiloride (ΔAmil) was greater and there was minimal Cl(-) secretion (ΔTCC) seen at baseline in the CF compared to the healthy subjects. ΔAmil was greater with both albuterol and exercise when compared to baseline within both CF and healthy groups, but there was no significant difference in the ΔTCC response with either treatment.

CONCLUSION

Both exercise and albuterol can alter ion regulation increasing Cl(-) secretion to a significant and similar degree in individuals with CF.

Direct imaging of functional networks

In blood-oxygenation-level-dependent functional magnetic resonance imaging (fMRI), current methods typically acquire ∼ 500,000 imaging voxels at each time point, and then use computer algorithms to reduce this data to the coefficients of a few hundred parcels or networks. This suggests that the amount of relevant information present in the fMRI signal is relatively small, and presents an opportunity to greatly improve the speed and signal to noise ratio (SNR) of the fMRI process. In this work, a theoretical framework is presented for calculating the coefficients of functional networks directly from highly undersampled fMRI data. Using predefined functional parcellations or networks and a compact k-space trajectory that samples data at optimal spatial scales, the problem of estimating network coefficients is reformulated to allow for direct least squares estimation, without Fourier encoding. By simulation, this approach is shown to allow for acceleration of the imaging process under ideal circumstances by nearly three orders of magnitude.

Enhanced identification of BOLD-like components with multi-echo simultaneous multi-slice (MESMS) fMRI and multi-echo ICA

The recent introduction of simultaneous multi-slice (SMS) acquisitions has enabled the acquisition of blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) data with significantly higher temporal sampling rates. In a parallel development, the use of multi-echo fMRI acquisitions in conjunction with a multi-echo independent component analysis (ME-ICA) approach has been introduced as a means to automatically distinguish functionally-related BOLD signal components from signal artifacts, with significant gains in sensitivity, statistical power, and specificity. In this work, we examine the gains that can be achieved with a combined approach in which data obtained with a multi-echo simultaneous multi-slice (MESMS) acquisition are analyzed with ME-ICA. We find that ME-ICA identifies significantly more BOLD-like components in the MESMS data as compared to data acquired with a conventional multi-echo single-slice acquisition. We demonstrate that the improved performance of MESMS derives from both an increase in the number of temporal samples and the enhanced ability to filter out high-frequency artifacts.

Recommended implementation of arterial spin-labeled perfusion MRI for clinical applications: A consensus of the ISMRM perfusion study group and the European consortium for ASL in dementia

This review provides a summary statement of recommended implementations of arterial spin labeling (ASL) for clinical applications. It is a consensus of the ISMRM Perfusion Study Group and the European ASL in Dementia consortium, both of whom met to reach this consensus in October 2012 in Amsterdam. Although ASL continues to undergo rapid technical development, we believe that current ASL methods are robust and ready to provide useful clinical information, and that a consensus statement on recommended implementations will help the clinical community to adopt a standardized approach. In this review, we describe the major considerations and trade-offs in implementing an ASL protocol and provide specific recommendations for a standard approach. Our conclusion is that as an optimal default implementation, we recommend pseudo-continuous labeling, background suppression, a segmented three-dimensional readout without vascular crushing gradients, and calculation and presentation of both label/control difference images and cerebral blood flow in absolute units using a simplified model.

Effects of exercise intensity compared to albuterol in individuals with cystic fibrosis

BACKGROUND

Although exercise is a vital component of the therapy prescribed to individuals with cystic fibrosis (CF), it is not a priority due to a finite amount of treatment time and the view that exercise is not as beneficial as pharmacological treatments by many individuals with CF. We sought to compare the therapeutic benefits of exercise and their prescribed bronchodilator albuterol.

METHODS

CF (n = 14) and healthy (n = 16) subjects completed three visits, a baseline screening with VO2 max test and two treatment visits. On the two treatment visits, subjects completed spirometry and diffusing capacity of the lungs for nitric oxide (DLNO) maneuvers either at baseline, 60, and 110 min post-albuterol administration, or at baseline and the midway point of three separate 15 min exercise bouts at low, moderate and vigorous intensity (25, 50 and 65% of the maximum workload, respectively).

RESULTS

With moderate exercise the increase in DLNO was double (39 ± 8 vs 15  ± 6% change) and the level of bronchodilation similar (23% change) when compared to 110 min post-albuterol in individuals with CF. During exercise FVC became reduced (-309 ± 66 mL with moderate exercise) and the increase in FEV1 was attenuated (103 ± 39 vs 236 ± 58 mL, exercise vs. albuterol) when compared with the response to albuterol in individuals with CF. Epinephrine (EPI) release increased 39, 72 and 144% change with low, moderate and vigorous intensity exercise respectively for individuals with CF, but this increase was blunted when compared to healthy subjects.

CONCLUSION

Our results suggest that moderate intensity exercise is the optimal intensity for individuals with CF, as low intensity exercise increases EPI less than 50% and vigorous intensity exercise is over taxing, such that airflow can be restricted. Although the duration of the beneficial effect is uncertain, exercise can promote greater improvements in gas diffusion and comparable bronchodilation when compared to albuterol.

Increased SNR efficiency in velocity selective arterial spin labeling using multiple velocity selective saturation modules (mm-VSASL)

PURPOSE

Velocity-selective arterial spin labeling (VSASL) is theoretically insensitive to transit delay (TD) effects. However, it uses saturation instead of inversion, resulting in compromised signal to noise ratio (SNR). In this study we explore the use of multiple velocity-selective saturation (VSS) modules in VSASL (mm-VSASL) to improve SNR.

METHODS

Theoretical SNR efficiency improvement and optimized parameters were calculated from simulations for mm-VSASL. VSASL with two VSS modules (VSASL-2VSS) was implemented to measure cerebral blood flow in vivo, compared with conventional VSASL (VSASL-1VSS), pulsed ASL (PASL), and pseudo-continuous ASL (PCASL). TDs and bolus durations (BDs) were measured to validate the simulations and to examine the TD sensitivity of these preparations.

RESULTS

Compared with VSASL-1VSS, VSASL-2VSS achieved a significant improvement of SNR (22.1 ± 1.9%, P = 1.7 × 10(-6) ) in vivo, consistent with a 22.7% improvement predicted from simulations. The SNR was comparable to or higher (in gray matter, P = 4.3 × 10(-3) ) than that using PCASL. VSASL was experimentally verified to have minimal TD effects.

CONCLUSION

Utilizing multiple VSS modules can improve the SNR efficiency of VSASL. Mm-VSASL may result in an SNR that is comparable to or even higher than that of PCASL in applications where long postlabeling delays are required.

An optimized design to reduce eddy current sensitivity in velocity-selective arterial spin labeling using symmetric BIR-8 pulses

PURPOSE

Velocity-selective arterial spin labeling (VSASL) tags arterial blood on a velocity-selective (VS) basis and eliminates the tagging/imaging gap and associated transit delay sensitivity observed in other ASL tagging methods. However, the flow-weighting gradient pulses in VS tag preparation can generate eddy currents (ECs), which may erroneously tag the static tissue and create artificial perfusion signal, compromising the accuracy of perfusion quantification.

METHODS

A novel VS preparation design is presented using an eight-segment B1 insensitive rotation with symmetric radio frequency and gradient layouts (sym-BIR-8), combined with delays after gradient pulses to optimally reduce ECs of a wide range of time constants while maintaining B0 and B1 insensitivity. Bloch simulation, phantom, and in vivo experiments were carried out to determine robustness of the new and existing pulse designs to ECs, B0 , and B1 inhomogeneity.

RESULTS

VSASL with reduced EC sensitivity across a wide range of EC time constants was achieved with the proposed sym-BIR-8 design, and the accuracy of cerebral blood flow measurement was improved.

CONCLUSION

The sym-BIR-8 design performed the most robustly among the existing VS tagging designs, and should benefit studies using VS preparation with improved accuracy and reliability.

An introduction to ASL labeling techniques

Arterial spin labeling (ASL) methods allow for quantitative mapping of tissue perfusion in absolute units, without the use of contrast agents. In this technique, the magnetization of arterial blood water is labeled by magnetic inversion or saturation, and the delivery of labeled blood water to tissues is observed. In this review three classes of labeling methods for ASL are described and compared: continuous, pulsed, and velocity-selective. The quantification of perfusion from ASL data is discussed, and methods for the extraction of new types of information using ASL and related techniques, such as mapping of vascular territories or venous oxygenation, are described.

New developments in arterial spin labeling pulse sequences

Since it was introduced over 20 years ago, arterial spin labeling and related methods have steadily evolved over the years, and the field has seen not only improvements in technical specifications, such as signal-to-noise ratio and accuracy, but also the introduction of methods that allow for the collection of new information, such as maps of vascular territories and measurement of venous oxygenation. Some of these recent advances are reviewed here.

The time of maximum post-ischemic hyperperfusion indicates infarct growth following transient experimental ischemia

After recanalization, cerebral blood flow (CBF) can increase above baseline in cerebral ischemia. However, the significance of post-ischemic hyperperfusion for tissue recovery remains unclear. To analyze the course of post-ischemic hyperperfusion and its impact on vascular function, we used magnetic resonance imaging (MRI) with pulsed arterial spin labeling (pASL) and measured CBF quantitatively during and after a 60 minute transient middle cerebral artery occlusion (MCAO) in adult rats. We added a 5% CO₂ - challenge to analyze vasoreactivity in the same animals. Results from MRI were compared to histological correlates of angiogenesis. We found that CBF in the ischemic area recovered within one day and reached values significantly above contralateral thereafter. The extent of hyperperfusion changed over time, which was related to final infarct size: early (day 1) maximal hyperperfusion was associated with smaller lesions, whereas a later (day 4) maximum indicated large lesions. Furthermore, after initial vasoparalysis within the ischemic area, vasoreactivity on day 14 was above baseline in a fraction of animals, along with a higher density of blood vessels in the ischemic border zone. These data provide further evidence that late post-ischemic hyperperfusion is a sequel of ischemic damage in regions that are likely to undergo infarction. However, it is transient and its resolution coincides with re-gaining of vascular structure and function.

Genetic variation of SCNN1A influences lung diffusing capacity in cystic fibrosis

INTRODUCTION

Epithelial Na channels (ENaCs) play a crucial role in ion and fluid regulation in the lung. In cystic fibrosis (CF), Na hyperabsorption results from ENaC overactivity, leading to airway dehydration. Previous work has demonstrated functional genetic variation of SCNN1A (the gene encoding the ENaC α-subunit), manifesting as an alanine (A) to threonine (T) substitution at amino acid 663, with the αT663 variant resulting in a more active channel.

METHODS

We assessed the influence of genetic variation of SCNN1A on the diffusing capacity of the lungs for carbon monoxide (DLCO) and nitric oxide (DLNO), together with alveolar-capillary membrane conductance (DM), pulmonary capillary blood volume, and alveolar volume (VA) at rest and during peak exercise in 18 patients with CF (10 homozygous for αA663 (AA group) and 8 with at least one T663 allele (AT/TT group)). Because of the more active channel, we hypothesized that the AT/TT group would show a greater increase in DLCO, DLNO, and DM with exercise because of exercise-mediated ENaC inhibition and subsequent attenuation of Na hyperabsorption.

RESULTS

The AT/TT group had significantly lower pulmonary function, weight, and body mass index than the AA group. Both groups had similar peak workloads, relative peak oxygen consumptions, and cardiopulmonary responses to exercise. The AT/TT group demonstrated a greater increase in DLNO, DLNO/VA, and DM in response to exercise (% increases: DLNO = 18 ± 11 vs 41 ± 38; DLNO/VA = 14 ± 21 vs 40 ± 37; DM = 15 ± 11 vs 41 ± 38, AA vs AT/TT, respectively). There were no differences between groups in absolute diffusing capacity measures at peak exercise.

CONCLUSION

These results suggest that genetic variation of the α-subunit of ENaC differentially affects the diffusing capacity response to exercise in patients with CF.

Racial/ethnic differences in the prevalence of proteinuric and nonproteinuric diabetic kidney disease

OBJECTIVE

To examine racial/ethnic differences in the prevalence of diabetic kidney disease (DKD), with and without proteinuria, in an outpatient health care organization.

RESEARCH DESIGN AND METHODS

We examined electronic health records for 15,683 persons of non-Hispanic white (NHW), Asian (Asian Indian, Chinese, and Filipino), Hispanic, and non-Hispanic black (NHB) race/ethnicity with type 2 diabetes and no prior history of kidney disease from 2008 to 2010. We directly standardized age- and sex-adjusted prevalence rates of proteinuric DKD (proteinuria with or without low estimated glomerular filtration rate [eGFR]) or nonproteinuric DKD (low eGFR alone). We calculated sex-specific odds ratios of DKD in racial/ethnic minorities (relative to NHWs) after adjustment for traditional DKD risk factors.

RESULTS

Racial/ethnic minorities had higher rates of proteinuric DKD than NHWs (24.8-37.9 vs. 24.8%) and lower rates of nonproteinuric DKD (6.3-9.8 vs. 11.7%). On adjusted analyses, Chinese (odds ratio 1.39 for women and 1.56 for men), Filipinos (1.57 for women and 1.85 for men), Hispanics (1.46 for women and 1.34 for men), and NHBs (1.50 for women) exhibited significantly (P < 0.01) higher odds of proteinuric DKD than NHWs. Conversely, Chinese, Hispanic, and NHB women and Hispanic men had significantly lower odds of nonproteinuric DKD than NHWs.

CONCLUSIONS

We found novel racial/ethnic differences in DKD among patients with type 2 diabetes. Racial/ethnic minorities were more likely to have proteinuric DKD and less likely to have nonproteinuric DKD. Future research should examine diverse DKD-related outcomes by race/ethnicity to inform targeted prevention and treatment efforts and to explore the etiology of these differences.

A novel method of combining blood oxygenation and blood flow sensitive magnetic resonance imaging techniques to measure the cerebral blood flow and oxygen metabolism responses to an unknown neural stimulus

Simultaneous implementation of magnetic resonance imaging methods for Arterial Spin Labeling (ASL) and Blood Oxygenation Level Dependent (BOLD) imaging makes it possible to quantitatively measure the changes in cerebral blood flow (CBF) and cerebral oxygen metabolism (CMRO₂) that occur in response to neural stimuli. To date, however, the range of neural stimuli amenable to quantitative analysis is limited to those that may be presented in a simple block or event related design such that measurements may be repeated and averaged to improve precision. Here we examined the feasibility of using the relationship between cerebral blood flow and the BOLD signal to improve dynamic estimates of blood flow fluctuations as well as to estimate metabolic-hemodynamic coupling under conditions where a stimulus pattern is unknown. We found that by combining the information contained in simultaneously acquired BOLD and ASL signals through a method we term BOLD Constrained Perfusion (BCP) estimation, we could significantly improve the precision of our estimates of the hemodynamic response to a visual stimulus and, under the conditions of a calibrated BOLD experiment, accurately determine the ratio of the oxygen metabolic response to the hemodynamic response. Importantly we were able to accomplish this without utilizing a priori knowledge of the temporal nature of the neural stimulus, suggesting that BOLD Constrained Perfusion estimation may make it feasible to quantitatively study the cerebral metabolic and hemodynamic responses to more natural stimuli that cannot be easily repeated or averaged.

Racial/ethnic differences in control of cardiovascular risk factors among type 2 diabetes patients in an insured, ambulatory care population

AIMS

This paper examines differences in cardiovascular disease risk factor control among racial/ethnic minorities (Asian Indian, Chinese, Filipino, Japanese, Korean, Vietnamese, Hispanic/Latino, Black/African Americans) with type 2 diabetes compared to Non-Hispanic Whites with type 2 diabetes in an insured, outpatient setting.

METHODS

A three-year, cross-sectional sample of 15,826 patients with type 2 diabetes was studied between 2008 and 2010. Goal attainment rates for three cardiovascular disease risk factors (HbA1c, BP, LDL) were estimated. Logistic regression was used to determine the association between patient characteristics and control of risk factors.

RESULTS

Only one fifth (21.1%) of patients achieved simultaneous goal attainment (HbA1c, BP, LDL). After adjustment for patient characteristics and treatment, Black/African American women and men, and Filipino and Hispanic/Latino men were significantly less likely to simultaneously achieve all three goals, compared to Non-Hispanic Whites. Of the three goals, patients were more likely to achieve HbA1c goals (68.7%) than BP (45.7%) or LDL (58.5%) goals. Racial/ethnic differences were more apparent in risk factors that were under better control (i.e. HbA1c).

CONCLUSIONS

Cardiovascular risk factor control in type 2 diabetes is suboptimal, even in an insured population. Special attention may be required for specific racial/ethnic/gender groups.

Venous oxygenation mapping using velocity-selective excitation and arterial nulling

A new MRI technique to map the oxygenation of venous blood is presented. The method uses velocity-selective excitation and arterial nulling pulses, combined with phase sensitive signal detection to isolate the venous blood signal. T₂ of this signal along with a T₂-Y calibration curve yields estimates of venous oxygenation in situ. Results from phantoms and healthy human subjects under normoxic and hypoxic conditions are shown, and venous saturation levels estimated from both sagittal sinus and gray matter-based regions of interest are compared with the related techniques TRUST and QUIXOTIC. In addition, combined with an additional scan without arterial nulling pulses, the oxygen saturation level on arterial side can also be estimated.

Clinically identified postpartum depression in Asian American mothers

OBJECTIVE

To identify the clinical diagnosis rate of postpartum depression (PPD) in Asian American subgroups (Asian Indian, Chinese, Filipino, Japanese, Korean, Vietnamese) compared to non-Hispanic Whites.

DESIGN

Cross-sectional study using electronic health records (EHR).

SETTING

A large, outpatient, multiservice clinic in Northern California.

PARTICIPANTS

A diverse clinical population of non-Hispanic White (N = 4582), Asian Indian (N = 1264), Chinese (N = 1160), Filipino (N = 347), Japanese (N = 124), Korean (N = 183), and Vietnamese (N = 147) mothers.

METHODS

Cases of PPD were identified from EHRs using physician diagnosis codes, medication usage, and age standardized for comparison. The relationship between PPD and other demographic variables (race/ethnicity, maternal age, delivery type, marital status, and infant gender) were examined in a multivariate logistic regression model.

RESULTS

The PPD diagnosis rate for all Asian American mothers in aggregate was significantly lower than the diagnosis rate in non-Hispanic White mothers. Moreover, of the six Asian American subgroups, PPD diagnosis rates for Asian Indian, Chinese, and Filipino mothers were significantly lower than non-Hispanic White mothers. In multivariate analyses, race/ethnicity, age, and cesarean were significant predictors of PPD.

CONCLUSION

In this insured population, PPD diagnosis rates were lower among Asian Americans, with variability in rates across the individual Asian American subgroups. It is unclear whether these lower rates are due to underreporting, underdiagnosis, or underutilization of mental health care in this setting.

Arterial spin labeled CMR detects clinically relevant increase in myocardial blood flow with vasodilation

OBJECTIVES

This study sought to determine whether arterial spin labeled (ASL) cardiac magnetic resonance (CMR) is capable of detecting clinically relevant increases in regional myocardial blood flow (MBF) with vasodilator stress testing in human myocardium.

BACKGROUND

Measurements of regional myocardial perfusion at rest and during vasodilatation are used to determine perfusion reserve, which indicates the presence and distribution of myocardial ischemia. ASL CMR is a perfusion imaging technique that does not require any contrast agents, and is therefore safe for use in patients with end-stage renal disease, and capable of repeated or continuous measurement.

METHODS

Myocardial ASL scans at rest and during adenosine infusion were incorporated into a routine CMR adenosine induced vasodilator stress protocol and was performed in 29 patients. Patients who were suspected of having ischemic heart disease based on first-pass imaging also underwent x-ray angiography. Myocardial ASL was performed using double-gated flow-sensitive alternating inversion recovery tagging and balanced steady-state free precession imaging at 3-T.

RESULTS

Sixteen patients were found to be normal and 13 patients were found to have visible perfusion defect based on first-pass CMR using intravenous gadolinium chelate. In the normal subjects, there was a statistically significant difference between MBF measured by ASL during adenosine infusion (3.67 ± 1.36 ml/g/min), compared to at rest (0.97 ± 0.64 ml/g/min), with p < 0.0001. There was also a statistically significant difference in perfusion reserve (MBF(stress)/MBF(rest)) between normal myocardial segments (3.18 ± 1.54) and the most ischemic segments in the patients with coronary artery disease identified by x-ray angiography (1.44 ± 0.97), with p = 0.0011.

CONCLUSIONS

This study indicates that myocardial ASL is capable of detecting clinically relevant increases in MBF with vasodilatation and has the potential to identify myocardial ischemia.

Local head gradient coils: window(s) of opportunity

At the Medical College of Wisconsin (MCW), prior to the 1991 announcement of the discovery of BOLD fMRI, all of the technical pieces that were needed for efficient BOLD fMRI imaging were assembled for other applications, allowing MCW to jump into the fMRI business just days after the announcement. Central among these pieces was single shot EPI, implemented at MCW using a three axis local head gradient coil. This article describes the development of local gradient coil technology at MCW, and a historical perspective on local head gradient coils in general.

Pseudocontinuous arterial spin labeling with optimized tagging efficiency

The adiabatic inversion of blood in pseudocontinuous arterial spin labeling (PCASL) is highly sensitive to off-resonance effects and gradient imperfections and this sensitivity can lead to tagging efficiency loss and unpredictable variations in cerebral blood flow estimates. This efficiency loss is caused by a phase tracking error between the RF pulses and the flowing spins. This article introduces a new method, referred to as Optimized PCASL (OptPCASL), that minimizes the phase tracking error by applying an additional compensation RF phase term and in-plane gradients to the PCASL pulse train. The optimal RF phase and gradient amplitudes are determined using a prescan procedure, which consists of a series of short scans interleaved with automated postprocessing routines integrated to the scanner console. The prescan procedure is shown to minimize the phase tracking error in a robust and time efficient manner. As an example of its application, the use of OptPCASL for the improved detection of functional activation in the visual cortex is demonstrated and temporal signal-to-noise ratio (SNR), image SNR, and baseline cerebral blood flow measures are compared to those acquired from conventional PCASL.

Accuracy of data entry of patient race/ethnicity/ancestry and preferred spoken language in an ambulatory care setting

OBJECTIVE

To describe data collection methods and to audit staff data entry of patient self-reported race/ethnicity/ancestry and preferred spoken language (R/E/A/L) information.

DATA SOURCE/STUDY SETTING

Large mixed payer outpatient health care organization in Northern California, June 2009.

STUDY DESIGN

Secondary analysis of an audit planned and executed by the Department of Clinical Services.

DATA COLLECTION/EXTRACTION METHODS

We analyzed concordance between patient written responses and staff data entry.

PRINCIPAL FINDINGS

The data entry accuracy rate across questions was high, ranging from 92 to 97 percent. Inaccuracies were due to human error (62 percent), flaws in system design (2 percent), or some combination of both (35 percent).

CONCLUSIONS

This study highlights the high accuracy of patient self-reported R/E/A/L data entry and identifies some areas for improvement in staff training and technical system design to facilitate further progress.

On multiple alternating steady states induced by periodic spin phase perturbation waveforms

Direct measurement of neural currents by means of MRI can potentially open a high temporal resolution (10-100 ms) window applicable for monitoring dynamics of neuronal activity without loss of the high spatial resolution afforded by MRI. Previously, we have shown that the alternating balanced steady state imaging affords high sensitivity to weak periodic currents owing to its amplification of periodic spin phase perturbations. This technique, however, requires precise synchronization of such perturbations to the radiofrequency pulses. Herein, we extend alternating balanced steady state imaging to multiple balanced alternating steady states for estimation of neural current waveforms. Simulations and phantom experiments show that the off-resonance profile of the multiple alternating steady state signal carries information about the frequency content of driving waveforms. In addition, the method is less sensitive than alternating balanced steady state to precise waveform timing relative to radiofrequency pulses. Thus, multiple alternating steady state technique is potentially applicable to MR imaging of the waveforms of periodic neuronal activity.

Type 2 diabetes: identifying high risk Asian American subgroups in a clinical population

AIMS

We compared the prevalence and treatment of type 2 diabetes across Asian American subgroups (Asian Indian, Chinese, Filipino, Japanese, Korean, Vietnamese) and Non-Hispanic Whites (NHWs) in a Northern California healthcare system.

METHODS

A three-year, cross-sectional sample of patient electronic health records was accessed to compare diabetes prevalence in 21,816 Asian and 73,728 NHWs aged 35+ years. Diabetes was classified through ICD-9 codes, abnormal laboratory values, or use of oral anti-diabetic medication. Multivariate adjusted prevalence rates for each Asian subgroup, and adjusted odds ratios (OR) relative to NHWs, were compared.

RESULTS

Age-adjusted prevalence ranged from 5.8% to 18.2% (women) and 8.1 to 25.3% (men). Age-adjusted ORs of Asian subgroups ranged 1.11-3.94 (women) and 1.14-4.56 (men). The odds of diabetes were significantly higher in Asian Indians (women OR 3.44, men OR 3.54) and Filipinos (women OR 3.94, men OR 4.56), compared to NHWs. Results for Asian Indians and Filipinos were similar with age-and-BMI adjustment. Treatment rates across subgroups were 59.7-82.0% (women) and 62.9-79.4% (men).

CONCLUSIONS

Heterogeneity exists in the prevalence of diabetes across Asian subgroups, independent of obesity prevalence. Asian Indian and Filipino subgroups had particularly high prevalence of diabetes when compared to NHWs. Future studies should explore these clinically important differences among Asian subgroups.

Shared medical appointments: promoting weight loss in a clinical setting

INTRODUCTION

Shared medical appointments (SMAs) are 90-minute group appointments for patients with similar medical complaints. SMAs include components of a traditional office visit but provide further emphasis on health education. The effectiveness of SMAs on weight-loss in an outpatient setting has not been studied.

METHODS

Weight-loss SMAs were offered by one physician at the Palo Alto Medical Foundation. Teaching content included Diabetes Prevention Program materials. This analysis includes patients who attended at least one SMA (n = 74) compared with patients in the same physician's practice who had at least one office visit and a body mass index ≥ 25 kg/m(2) (n = 356).

RESULTS

The SMA group had a higher proportion of women than the comparison group (76% vs 64%) and were older (mean, 52.4 years; SD, 13.1 years vs mean, 47.0 years; SD, 13.3 years). SMA patients on average lost 1.0% of their baseline weight. Patients in the comparison group on average gained 0.8% of their baseline weight.

DISCUSSION

SMAs may be a viable option for physicians to promote weight loss in the clinical setting.

Multiphase pseudocontinuous arterial spin labeling (MP-PCASL) for robust quantification of cerebral blood flow

Pseudocontinuous arterial spin labeling (PCASL) has been demonstrated to provide the sensitivity of the continuous arterial spin labeling method while overcoming many of the limitations of that method. Because the specification of the phases in the radiofrequency pulse train in PCASL defines the tag and control conditions of the flowing arterial blood, its tagging efficiency is sensitive to factors, such as off-resonance fields, that induce phase mismatches between the radiofrequency pulses and the flowing spins. As a result, the quantitative estimation of cerebral blood flow with PCASL can exhibit a significant amount of error when these factors are not taken into account. In this paper, the sources of the tagging efficiency loss are characterized and a novel PCASL method that utilizes multiple phase offsets is proposed to reduce the tagging efficiency loss in PCASL. Simulations are performed to evaluate the feasibility and the performance of the proposed method. Quantitative estimates of cerebral blood flow obtained with multiple phase offset PCASL are compared to estimates obtained with conventional PCASL and pulsed arterial spin labeling. Our results show that multiple phase offset PCASL provides robust cerebral blood flow quantification while retaining much of the sensitivity advantage of PCASL.

Population Colorectal Cancer Screening Estimates: Comparing Self-Report to Electronic Health Record Data in California

INTRODUCTION: Population-based surveys are used to assess colorectal cancer (CRC) screening rates, but may be subject to self-report biases. Clinical data from electronic health records (EHR) are another data source for assessing screening rates and self-report bias; however, use of EHR data for population research is relatively new. We sought to compare CRC screening rates from a self-report survey, the 2007 California Health Interview Survey (CHIS), to EHR data from Palo Alto Medical Foundation (PAMF), a multi-specialty healthcare organization serving three counties in California. METHODS: Ever- and up-to-date CRC screening rates were compared between CHIS respondents (N=18,748) and PAMF patients (N=26,283). Both samples were limited to English proficient subjects aged 51-75 with health insurance and a physician visit in the past two years. PAMF rates were age-sex standardized to the CHIS population. Analyses were stratified by racial/ethnic group. RESULTS: EHR data included PAMF internally completed tests (84%), and patient-reported externally completed tests which were either confirmed (7%) or unconfirmed (9%) by a physician. When excluding unconfirmed tests, PAMF screening rates were 6-14 percentage points lower than CHIS rates, for both ever- and up-to-date CRC screening among Non-Hispanic White, Black, Hispanic/Latino, Chinese, Filipino and Japanese subjects. When including unconfirmed tests, differences in screening rates between the two data sets were minimal. CONCLUSION: Comparability of CRC screening rates from survey data and clinic-based EHR data depends on whether or not unconfirmed patient-reported tests in EHR are included. This indicates a need for validated methods of calculating CRC screening rates in EHR data.

Impaired lung diffusing capacity for nitric oxide and alveolar-capillary membrane conductance results in oxygen desaturation during exercise in patients with cystic fibrosis

BACKGROUND

Exercise has been shown to be beneficial for patients with cystic fibrosis (CF), but for some CF patients there is a risk of desaturation, although the predicting factors are not conclusive or reliable. We sought to determine the relationship between the diffusion capacity of the lungs for nitric oxide and carbon monoxide (DLNO and DLCO) and the components of DLCO: alveolar-capillary membrane conductance (D(M)), and pulmonary capillary blood volume (V(C)) on peripheral oxygen saturation (SaO(2)) at rest and during exercise in CF.

METHODS

17 mild/moderate CF patients and 17 healthy subjects were recruited (age=26±7 vs. 23±8 years, ht=169±8 vs. 166±8 cm, wt=65±9 vs. 59±8 kg, BMI=23±3 vs. 22±3 kg/m(2), VO(2PEAK)=101±36 vs. 55±25%pred., FEV(1)=92±22 vs. 68±25%pred., for healthy and CF, respectively, mean±SD, VO(2PEAK) and FEV(1) p<0.001). Subjects performed incremental cycle ergometry to exhaustion with continuous monitoring of SaO(2) and measures of DLNO, DLCO, D(M) and V(C) at each stage.

RESULTS

CF patients had a lower SaO(2) at rest and peak exercise (rest=98±1 vs. 96±1%, peak=97±2 vs. 93±5%, for healthy and CF, respectively, p<0.01). At rest, DLNO, DLCO, D(M) were significantly lower in the CF group (p<0.01). The difference between groups was augmented with exercise (DLNO=117±4 vs. 73±3ml/min/mmHg; DLCO=34±8 vs. 23±8ml/min/mmHg; D(M)=50±1 vs. 34±1, p<0.001, for healthy and CF respectively). Peak SaO(2) was related to resting DLNO in CF patients (r=0.65, p=0.003).

CONCLUSIONS

These results suggest a limitation in exercise-mediated increases in membrane conductance in CF which may contribute to a drop in SaO(2) and that resting DLNO can account for a large portion of the variability in SaO(2).

Asian Americans have greater prevalence of metabolic syndrome despite lower body mass index

Objective

To examine the relationship between body mass index and metabolic syndrome for Asian Americans and non-Hispanic Whites, given that evidence shows racial/ethnic heterogeneity exists in how body mass index predicts metabolic syndrome.

Research Design and Methods

Electronic health records of 43 507 primary care patients aged 35 years and older with self-identified race/ethnicity of interest (Asian Indian, Chinese, Filipino, Japanese, Korean, Vietnamese, or non-Hispanic White) were analyzed in a mixed-payer, outpatient-focused healthcare organization in the San Francisco Bay Area.

Results

Metabolic syndrome prevalence is significantly higher in Asians compared to non-Hispanic Whites for every body mass index category. For women at the mean age of 55 and body mass index of 25 kg/m², the predicted prevalence of metabolic syndrome is 12% for non-Hispanic White women compared to 30% for Asians; similarly for men, the predicted prevalence of metabolic syndrome is 22% for non-Hispanic Whites compared to 43% of Asians. Compared to non-Hispanic White women and men with a body mass index of 25 kg/m², comparable prevalence of metabolic syndrome was seen at body mass index of 19.6 kg/m² for Asian women and 19.9 kg/m² for Asian men. A similar pattern was seen in disaggregated Asian subgroups.

Conclusions

Despite lower body mass index values and lower prevalence of overweight/obesity than non-Hispanic Whites, Asian Americans have higher rates of metabolic syndrome over the range of body mass index. Our results indicate that body mass index ranges for defining overweight/obesity in Asian populations should be lower than for non-Hispanic Whites.