Optimization and comparison of simultaneous and separate acquisition protocols for dual isotope myocardial perfusion SPECT.

Dual-isotope simultaneous-acquisition (DISA) rest-stress myocardial perfusion SPECT (MPS) protocols offer a number of advantages over separate acquisition. However, crosstalk contamination due to scatter in the patient and interactions in the collimator degrade image quality. Compensation can reduce the effects of crosstalk, but does not entirely eliminate image degradations. Optimizing acquisition parameters could further reduce the impact of crosstalk. In this paper we investigate the optimization of the rest Tl-201 energy window width and relative injected activities using the ideal observer (IO), a realistic digital phantom population and Monte Carlo (MC) simulated Tc-99m and Tl-201 projections as a means to improve image quality. We compared performance on a perfusion defect detection task for Tl-201 acquisition energy window widths varying from 4 to 40 keV centered at 72 keV for a camera with a 9% energy resolution. We also investigated 7 different relative injected activities, defined as the ratio of Tc-99m and Tl-201 activities, while keeping the total effective dose constant at 13.5 mSv. For each energy window and relative injected activity, we computed the IO test statistics using a Markov chain Monte Carlo (MCMC) method for an ensemble of 1,620 triplets of fixed and reversible defect-present, and defect-absent noisy images modeling realistic background variations. The volume under the 3-class receiver operating characteristic (ROC) surface (VUS) was estimated and served as the figure of merit. For simultaneous acquisition, the IO suggested that relative Tc-to-Tl injected activity ratios of 2.6-5 and acquisition energy window widths of 16-22% were optimal. For separate acquisition, we observed a broad range of optimal relative injected activities from 2.6 to 12.1 and acquisition energy window of widths 16-22%. A negative correlation between Tl-201 injected activity and the width of the Tl-201 energy window was observed in these ranges. The results also suggested that DISA methods could potentially provide image quality as good as that obtained with separate acquisition protocols. We compared observer performance for the optimized protocols and the current clinical protocol using separate acquisition. The current clinical protocols provided better performance at a cost of injecting the patient with approximately double the injected activity of Tc-99m and Tl-201, resulting in substantially increased radiation dose.

Design of a digital phantom population for myocardial perfusion SPECT imaging research.

Digital phantoms and Monte Carlo (MC) simulations have become important tools for optimizing and evaluating instrumentation, acquisition and processing methods for myocardial perfusion SPECT (MPS). In this work, we designed a new adult digital phantom population and generated corresponding Tc-99m and Tl-201 projections for use in MPS research. The population is based on the three-dimensional XCAT phantom with organ parameters sampled from the Emory PET Torso Model Database. Phantoms included three variations each in body size, heart size, and subcutaneous adipose tissue level, for a total of 27 phantoms of each gender. The SimSET MC code and angular response functions were used to model interactions in the body and the collimator-detector system, respectively. We divided each phantom into seven organs, each simulated separately, allowing use of post-simulation summing to efficiently model uptake variations. Also, we adapted and used a criterion based on the relative Poisson effective count level to determine the required number of simulated photons for each simulated organ. This technique provided a quantitative estimate of the true noise in the simulated projection data, including residual MC simulation noise. Projections were generated in 1 keV wide energy windows from 48-184 keV assuming perfect energy resolution to permit study of the effects of window width, energy resolution, and crosstalk in the context of dual isotope MPS. We have developed a comprehensive method for efficiently simulating realistic projections for a realistic population of phantoms in the context of MPS imaging. The new phantom population and realistic database of simulated projections will be useful in performing mathematical and human observer studies to evaluate various acquisition and processing methods such as optimizing the energy window width, investigating the effect of energy resolution on image quality and evaluating compensation methods for degrading factors such as crosstalk in the context of single and dual isotope MPS.

The importance of establishing a national health security preparedness index.

Natural disasters, infectious disease epidemics, terrorism, and major events like the nuclear incident at Fukushima all pose major potential challenges to public health and security. Events such as the anthrax letters of 2001, Hurricanes Katrina, Irene, and Sandy, severe acute respiratory syndrome (SARS) and West Nile virus outbreaks, and the 2009 H1N1 influenza pandemic have demonstrated that public health, emergency management, and national security efforts are interconnected. These and other events have increased the national resolve and the resources committed to improving the national health security infrastructure. However, as fiscal pressures force federal, state, and local governments to examine spending, there is a growing need to demonstrate both what the investment in public health preparedness has bought and where gaps remain in our nation's health security. To address these needs, the Association of State and Territorial Health Officials (ASTHO), through a cooperative agreement with the Centers for Disease Control and Prevention (CDC) Office of Public Health Preparedness and Response (PHPR), is creating an annual measure of health security and preparedness at the national and state levels: the National Health Security Preparedness Index (NHSPI).

Assessment of medical reserve corps volunteers' emergency response willingness using a threat- and efficacy-based model.

The goal of this study was to investigate the willingness of Medical Reserve Corps (MRC) volunteers to participate in public health emergency-related activities by assessing their attitudes and beliefs. MRC volunteers responded to an online survey organized around the Extended Parallel Process Model (EPPM). Respondents reported agreement with attitude/belief statements representing perceived threat, perceived efficacy, and personal/organizational preparedness in 4 scenarios: a weather-related disaster, a pandemic influenza emergency, a radiological ("dirty bomb") emergency, and an inhalational anthrax bioterrorism emergency. Logistic regression analyses were used to evaluate predictors of volunteer response willingness. In 2 response contexts (if asked and regardless of severity), self-reported willingness to respond was higher among those with a high perceived self-efficacy than among those with low perceived self-efficacy. Analyses of the association between attitude/belief statements and the EPPM profiles indicated that, under all 4 scenarios and with few exceptions, those with a perceived high threat/high efficacy EPPM profile had statistically higher odds of agreement with the attitude/belief statements than those with a perceived low threat/low efficacy EPPM profile. The radiological emergency consistently received the lowest agreement rates for the attitude/belief statements and response willingness across scenarios. The findings suggest that enrollment with an MRC unit is not automatically predictive of willingness to respond in these types of scenarios. While MRC volunteers' self-reported willingness to respond was found to differ across scenarios and among different attitude and belief statements, the identification of self-efficacy as the primary predictor of willingness to respond regardless of severity and if asked highlights the critical role of efficacy in an organized volunteer response context.

Participatory public health systems research: value of community involvement in a study series in mental health emergency preparedness.

BACKGROUND: Concerns have arisen over recent years about the absence of empirically derived evidence on which to base policy and practice in the public health system, in general, and to meet the challenge of public health emergency preparedness, in particular. Related issues include the challenge of disaster-caused, behavioral health surge, and the frequent exclusion of populations from studies that the research is meant to aid. OBJECTIVE: To characterize the contributions of nonacademic collaborators to a series of projects validating a set of interventions to enhance capacity and competency of public mental health preparedness planning and response. SETTING(S): Urban, suburban, and rural communities of the state of Maryland and rural communities of the state of Iowa. PARTICIPANTS: Study partners and participants (both of this project and the studies examined) were representatives of academic health centers (AHCs), local health departments (LHDs), and faith-based organizations (FBOs) and their communities. PROCEDURES: A multiple-project, case study analysis was conducted, that is, four research projects implemented by the authors from 2005 through 2011 to determine the types and impact of contributions made by nonacademic collaborators to those projects. The analysis involved reviewing research records, conceptualizing contributions (and providing examples) for government, faith, and (nonacademic) institutional collaborators. RESULTS: Ten areas were identified where partners made valuable contributions to the study series; these "value-areas" were as follows: 1) leadership and management of the projects; 2) formulation and refinement of research topics, aims, etc; 3) recruitment and retention of participants; 4) design and enhancement of interventions; 5) delivery of interventions; 6) collection, analysis, and interpretation of data; 7) dissemination of findings; 8) ensuring sustainability of faith/government preparedness planning relationships; 9) optimizing scalability and portability of the model; and 10) facilitating translational impact of study findings. CONCLUSIONS: Systems-based partnerships among academic, faith, and government entities offer an especially promising infrastructure for conducting participatory public health systems research in domestic emergency preparedness and response.

Assessment of psychological preparedness and emergency response willingness of local public health department and hospital workers.

This study sought to investigate the relationship between psychologically-related attitudes/beliefs toward public health emergency response among local health department (LHD) and hospital workers and their willingness to respond to a pandemic influenza emergency scenario and a radiological 'dirty' bomb scenario, to inform workforce resilience-building interventions. LHD and hospital workers participated in a survey based on an established threat- and efficacy-oriented behavioral model (the extended parallel process model) that focused on collection of the aforementioned attitudes, beliefs, and self-reported response willingness. Odds ratios associating psychologically-related attitudes and beliefs with self-reported response willingness were computed Perceived levels of psychological preparedness and support were shown to impact response willingness, with more pronounced effects in the radiological 'dirty' bomb scenario. Compared to those who did not perceive themselves to be psychologically prepared, those who did perceive themselves as prepared had higher odds of self-reported response willingness. The relationship of these perceptions and self-reported willingness to respond in all contexts, both scenarios, and both cohorts was influenced by perceived self-efficacy andperceived family preparedness.

Understanding estimated worker absenteeism rates during an influenza pandemic.

OBJECTIVES: Published employee absenteeism estimates during an influenza pandemic range from 10 to 40 percent. The purpose of this study was to estimate daily employee absenteeism through the duration of an influenza pandemic and to determine the relative impact of key variables used to derive the estimates. DESIGN: Using the Centers for Disease Control and Prevention's FluWorkLoss program, the authors estimated the number of absent employees on any given day over the course of a simulated 8-week pandemic wave by using varying attack rates. Employee data from a university with a large academic health system were used. Sensitivity of the program outputs to variation in predictor (inputs) values was assessed. Finally, the authors examined and documented the algorithmic sequence of the program. RESULTS: Using a 35 percent attack rate, a total of 47,270 workdays (or 3.4 percent of all available workdays) would be lost over the course of an 8-week pandemic among a population of 35,026 employees. The highest (peak) daily absenteeism estimate was 5.8 percent (minimum 4.8 percent; maximum 7.4 percent). Sensitivity analysis revealed that varying days missed for nonhospitalized illness had the greatest potential effect on peak absence rate (3.1 to 17.2 percent). Peak absence with 15 and 25 percent attack rates were 2.5 percent and 4.2 percent, respectively. CONCLUSIONS: The impact of an influenza pandemic on employee availability may be less than originally thought, even with a high attack rate. These data are generalizable and are not specific to institutions of higher education or medical centers. Thus, these findings provide realistic and useful estimates for influenza pandemic planning for most organizations.

Characterizing hospital workers' willingness to report to duty in an influenza pandemic through threat- and efficacy-based assessment.

BACKGROUND: Hospital-based providers' willingness to report to work during an influenza pandemic is a critical yet under-studied phenomenon. Witte's Extended Parallel Process Model (EPPM) has been shown to be useful for understanding adaptive behavior of public health workers to an unknown risk, and thus offers a framework for examining scenario-specific willingness to respond among hospital staff. METHODS: We administered an anonymous online EPPM-based survey about attitudes/beliefs toward emergency response, to all 18,612 employees of the Johns Hopkins Hospital from January to March 2009. Surveys were completed by 3426 employees (18.4%), approximately one third of whom were health professionals. RESULTS: Demographic and professional distribution of respondents was similar to all hospital staff. Overall, more than one-in-four (28%) hospital workers indicated they were not willing to respond to an influenza pandemic scenario if asked but not required to do so. Only an additional 10% were willing if required. One-third (32%) of participants reported they would be unwilling to respond in the event of a more severe pandemic influenza scenario. These response rates were consistent across different departments, and were one-third lower among nurses as compared with physicians. Respondents who were hesitant to agree to work additional hours when required were 17 times less likely to respond during a pandemic if asked. Sixty percent of the workers perceived their peers as likely to report to work in such an emergency, and were ten times more likely than others to do so themselves. Hospital employees with a perception of high efficacy had 5.8 times higher declared rates of willingness to respond to an influenza pandemic. CONCLUSIONS: Significant gaps exist in hospital workers' willingness to respond, and the EPPM is a useful framework to assess these gaps. Several attitudinal indicators can help to identify hospital employees unlikely to respond. The findings point to certain hospital-based communication and training strategies to boost employees' response willingness, including promoting pre-event plans for home-based dependents; ensuring adequate supplies of personal protective equipment, vaccines and antiviral drugs for all hospital employees; and establishing a subjective norm of awareness and preparedness.

Healthcare system cost evaluation of antiviral stockpiling for pandemic influenza preparedness.

Healthcare workers need to be protected during a severe influenza outbreak; therefore, we evaluated 4 different antiviral strategies: (1) using antiviral medication for outbreak prophylaxis of all hospital employees; (2) using antiviral medication for postexposure prophylaxis (PEP) or treatment of all hospital employees; (3) using a combination of antiviral medication for outbreak prophylaxis of high-risk clinical staff and postexposure prophylaxis or treatment for all other staff; and (4) using antiviral medication for postexposure prophylaxis or treatment of high-risk clinical staff only. Three different purchasing options were applied to each of the 4 antiviral strategies: (1) just-in-time purchase during a severe influenza outbreak, (2) prepandemic stockpiling, or (3) stockpiling through contracts with pharmaceutical manufacturers to reserve a predetermined antiviral supply. Although outbreak prophylaxis of all hospital employees would offer the maximum protection, the large costs associated with such a purchase make this option unrealistic and impractical. In addition, even though postexposure prophylaxis or treatment of only high-risk clinical staff would incur the least expense, the assumed level of protection if these options were offered only to high-risk clinical staff may not be sufficient to maintain routine hospital operations, since needed non-high-risk staff would not be protected. Considering the potential benefits and drawbacks of stockpiling antiviral medication from a cost perspective, it does not appear feasible for hospitals to stockpile antiviral medication in large quantities prior to a severe influenza outbreak. This article focuses on the financial viability of stockpiling antiviral medication, but the potential impact of other factors on the decision to stockpile was also considered and will be explored in future analyses. While legal hurdles related to prescribing, storing, and dispensing antiviral medication can be addressed, unavailability of a suitable vaccine supply may strongly support a decision to stockpile antiviral medication. Other issues to be addressed include antiviral resistance specifically related to the efficacy of oseltamivir, coupled with a high frequency of secondary bacterial infections; uncertainties about the degree of government assistance; potential government seizures of stockpiled assets; and legal and ethical concerns related to fair access to stockpiled medication. These issues may all be perceived as barriers to the feasibility of stockpiling antiviral medication.

Gauging U.S. Emergency Medical Services workers' willingness to respond to pandemic influenza using a threat- and efficacy-based assessment framework.

BACKGROUND: Emergency Medical Services workers' willingness to report to duty in an influenza pandemic is essential to healthcare system surge amidst a global threat. Application of Witte's Extended Parallel Process Model (EPPM) has shown utility for revealing influences of perceived threat and efficacy on non-EMS public health providers' willingness to respond in an influenza pandemic. We thus propose using an EPPM-informed assessment of EMS workers' perspectives toward fulfilling their influenza pandemic response roles. METHODOLOGY/PRINCIPAL FINDINGS: We administered an EPPM-informed snapshot survey about attitudes and beliefs toward pandemic influenza response, to a nationally representative, stratified random sample of 1,537 U.S. EMS workers from May-June 2009 (overall response rate: 49%). Of the 586 respondents who met inclusion criteria (currently active EMS providers in primarily EMS response roles), 12% indicated they would not voluntarily report to duty in a pandemic influenza emergency if asked, 7% if required. A majority (52%) indicated their unwillingness to report to work if risk of disease transmission to family existed. Confidence in personal safety at work (OR = 3.3) and a high threat/high efficacy ("concerned and confident") EPPM profile (OR = 4.7) distinguished those who were more likely to voluntarily report to duty. Although 96% of EMS workers indicated that they would probably or definitely report to work if they were guaranteed a pandemic influenza vaccine, only 59% had received an influenza immunization in the preceding 12 months. CONCLUSIONS/SIGNIFICANCE: EMS workers' response willingness gaps pose a substantial challenge to prehospital surge capacity in an influenza pandemic. "Concerned and confident" EMS workers are more than four times as likely to fulfill pandemic influenza response expectations. Confidence in workplace safety is a positively influential modifier of their response willingness. These findings can inform insights into interventions for enhancing EMS workers' willingness to respond in the face of a global infectious disease threat.

Assessment of local public health workers' willingness to respond to pandemic influenza through application of the extended parallel process model.

BACKGROUND: Local public health agencies play a central role in response to an influenza pandemic, and understanding the willingness of their employees to report to work is therefore a critically relevant concern for pandemic influenza planning efforts. Witte's Extended Parallel Process Model (EPPM) has been found useful for understanding adaptive behavior in the face of unknown risk, and thus offers a framework for examining scenario-specific willingness to respond among local public health workers. We thus aim to use the EPPM as a lens for examining the influences of perceived threat and efficacy on local public health workers' response willingness to pandemic influenza. METHODOLOGY/PRINCIPAL FINDINGS: We administered an online, EPPM-based survey about attitudes/beliefs toward emergency response (Johns Hopkins approximately Public Health Infrastructure Response Survey Tool), to local public health employees in three states between November 2006-December 2007. A total of 1835 responses were collected for an overall response rate of 83%. With some regional variation, overall 16% of the workers in 2006-7 were not willing to "respond to a pandemic flu emergency regardless of its severity". Local health department employees with a perception of high threat and high efficacy--i.e., those fitting a 'concerned and confident' profile in the EPPM analysis--had the highest declared rates of willingness to respond to an influenza pandemic if required by their agency, which was 31.7 times higher than those fitting a 'low threat/low efficacy' EPPM profile. CONCLUSIONS/SIGNIFICANCE: In the context of pandemic influenza planning, the EPPM provides a useful framework to inform nuanced understanding of baseline levels of--and gaps in--local public health workers' response willingness. Within local health departments, 'concerned and confident' employees are most likely to be willing to respond. This finding may allow public health agencies to design, implement, and evaluate training programs focused on emergency response attitudes in health departments.

Resource allocation on the frontlines of public health preparedness and response: report of a summit on legal and ethical issues.

OBJECTIVES: In the face of all-hazards preparedness challenges, local and state health department personnel have to date lacked a discrete set of legally and ethically informed public health principles to guide the distribution of scarce resources in crisis settings. To help address this gap, we convened a Summit of academic and practice experts to develop a set of principles for legally and ethically sound public health resource triage decision-making in emergencies. METHODS: The invitation-only Summit, held in Washington, D.C., on June 29, 2006, assembled 20 experts from a combination of academic institutions and nonacademic leadership, policy, and practice settings. The Summit featured a tabletop exercise designed to highlight resource scarcity challenges in a public health infectious disease emergency. This exercise served as a springboard for Summit participants' subsequent identification of 10 public health emergency resource allocation principles through an iterative process. RESULTS: The final product of the Summit was a set of 10 principles to guide allocation decisions involving scarce resources in public health emergencies. The principles are grouped into three categories: obligations to community; balancing personal autonomy and community well-being/benefit; and good preparedness practice. CONCLUSIONS: The 10 Summit-derived principles represent an attempt to link law, ethics, and real-world public health emergency resource allocation practices, and can serve as a useful starting framework to guide further systematic approaches and future research on addressing public health resource scarcity in an all-hazards context.

Corporate preparedness for pandemic influenza: a survey of pharmaceutical and biotechnology companies in Montgomery County, Maryland.

OBJECTIVES: We conducted a survey of corporate preparedness for pandemic influenza among biotechnology and pharmaceutical companies in Montgomery County, Maryland, to determine the level of preparedness for this industry and geographic region. METHODS: The survey, based on the HHS Business Pandemic Influenza Planning Checklist, established whether a company had a preparedness plan specific to pandemic influenza, the contents of its plan, or its reasons for a lack of a plan. RESULTS: A total of 50 companies participated in the survey. Of these, 40 did not have any type of preparedness plan, 3 were drafting plans, 6 had general preparedness plans that could be applied to an influenza pandemic, and only 1 company had a preparedness plan specifically designed to address pandemic influenza. CONCLUSIONS: Biotechnology and pharmaceutical companies in this geographic region are currently not well prepared for pandemic influenza. Public health officials should offer more help, possibly in the form of a model small business preparedness plan, and collaboration between companies should be encouraged to foster sharing of preparedness plans.

Comparison of 180 degrees and 360 degrees acquisition for myocardial perfusion SPECT with compensation for attenuation, detector response, and scatter: Monte Carlo and mathematical observer results.

BACKGROUND: The optimal projection data acquisition strategy for myocardial perfusion (MP) single photon emission computed tomography (SPECT) remains controversial. METHODS: We compared MP SPECT using 180 degrees and 360 degrees projection data obtained with the same acquisition time, reconstructed either with filtered back projection (FBP) or the iterative ordered-subsets expectation maximization (OS-EM) algorithm with various combinations of attenuation, detector response, and scatter compensation using mathematical observers and a myocardial defect detection task. We used Monte Carlo-simulated projection data from a population of 3-dimensional nurbs-based cardiac-torso (NCAT) phantoms with ranges of variability in patient anatomy, organ uptake, defect location, defect size, and noise level based on clinical data. Projection data from 180 degrees and 360 degrees acquisitions were generated by assuming the same acquisition time. After iterative or FBP reconstruction, standard postprocessing methods were applied. For each acquisition and reconstruction method, we optimized the number of iterations and cut-off frequency of the Butterworth filter using the Channelized Hotelling Observer methodology. The optimum set of parameters was that which gave the maximum area under the curve. RESULTS: For both acquisition protocols, OS-EM with compensations provided better performance than FBP or OS-EM without compensation. For FBP, the optimized 180 degrees acquisition provided a statistically significant increase in AUC as compared with optimized 360 degrees acquisition. For OS-EM, the AUCs for 180 degrees were slightly larger than for 360 degrees acquisitions when comparing images reconstructed with the same compensations. However, the differences were smaller and not statistically significant. CONCLUSION: With optimized reconstruction and filtering parameters, 180 degrees acquisition provided a statistically significant improvement over 360 degrees acquisition for FBP reconstruction. However, for OS-EM the differences were small and not statistically significant.

Establishing evidence-informed core intervention competencies in psychological first aid for public health personnel.

A full-scale public health response to disasters must attend to both the physical and mental health needs of affected communities. Public health preparedness efforts can be greatly expanded to address the latter set of needs, particularly in light of the high ratio of psychological to physical casualties that often rapidly overwhelms existing mental health response resources in a large-scale emergency. Psychological first aid--the provision of basic psychological care in the short term aftermath of a traumatic event--is a mental health response skill set that public health personnel can readily acquire with proper training. The application of psychological first aid by public health workers can significantly augment front-line community-based mental health responses during the crisis phase of an event. To help achieve this augmented response, we have developed a set of psychological first aid intervention competencies for public health personnel. These competencies, empirically grounded and based on best practice models and consensus statements from leading mental health organizations, represent a necessary step for developing a public health workforce that can better respond to the psychological needs of impacted populations in disasters.