Syndicate content
Recent documents in eScholarship@UMMS
Updated: 2 hours 18 min ago

Hospital-level variation in use of cardiovascular testing for adults with incident heart failure: findings from the cardiovascular research network heart failure study

Fri, 10/17/2014 - 11:48am

OBJECTIVES: This study aimed to characterize the use of cardiovascular testing for patients with incident heart failure (HF) hospitalization who participated in the National Heart, Lung, and Blood Institute sponsored Cardiovascular Research Network (CVRN) Heart Failure study.

BACKGROUND: HF is a common cause of hospitalization, and testing and treatment patterns may differ substantially between providers. Testing choices have important implications for the cost and quality of care.

METHODS: Crude and adjusted cardiovascular testing rates were calculated for each participating hospital. Cox proportional hazards regression models were used to examine hospital testing rates after adjustment for hospital-level patient case mix.

RESULTS: Of the 37,099 patients in the CVRN Heart Failure study, 5,878 patients were hospitalized with incident HF between 2005 and 2008. Of these, evidence of cardiovascular testing was available for 4,650 (79.1%) patients between 14 days before the incident HF admission and ending 6 months after the incident discharge. We compared crude and adjusted cardiovascular testing rates at the hospital level because the majority of testing occurred during the incident HF hospitalization. Of patients who underwent testing, 4,085 (87.9%) had an echocardiogram, 4,345 (93.4%) had a systolic function assessment, and 1,714 (36.9%) had a coronary artery disease assessment. Crude and adjusted testing rates varied markedly across the profiled hospitals, for individual testing modalities (e.g., echocardiography, stress echocardiography, nuclear stress testing, and left heart catheterization) and for specific clinical indications (e.g., systolic function assessment and coronary artery disease assessment).

CONCLUSIONS: For patients with newly diagnosed HF, we did not observe widespread overuse of cardiovascular testing in the 6 months following incident HF hospitalization relative to existing HF guidelines. Variations in testing were greatest for assessment of ischemia, in which testing guidelines are less certain. Elsevier Inc. All rights reserved.

Inaccurate risk perceptions and individualized risk estimates by patients with type 2 diabetes

Fri, 10/17/2014 - 11:48am

BACKGROUND: We evaluated how diabetic patients understand and respond to the presentation of personalized risk information.

METHODS: This was a mixed methods study involving 56 patients with type 2 diabetes and at least 1 additional cardiovascular risk factor. We assessed participants' perceptions of diabetes-related risks; asked them to rank order 6 events (death, heart attack, stroke, blindness, amputation, and kidney failure) by likelihood of occurrence in a specified time frame; presented them with personalized risk estimates; and asked them to re-rank the risks. The final 18 participants were tested to verify understanding before re-ranking risks. Qualitative analysis of interview transcripts identified themes and concepts underlying participants' ways of perceiving and reacting to risk.

RESULTS: While mortality was the most likely outcome for almost all participants, nearly all estimated it to be least likely; only 28% adjusted their mortality rankings to match model predictions. Some did not understand the risk information: only two thirds of those asked could rank risks according to the information presented. Risk perceptions were influenced by factors including "knowing myself," powerful anecdotes, and belief that a "warning shot" would occur before death.

CONCLUSIONS: Personalized risk estimates, particularly about mortality, had limited salience. Some participants could not understand the information, despite presentation in ways suggested by previous research.

Time to standardize and broaden the criteria of acute coronary syndrome symptom presentations in women

Fri, 10/17/2014 - 11:48am

Early recognition of the signs and symptoms of acute coronary syndromes (ACS) is essential to improving patient management and associated outcomes. It is widely reported that women might have a different ACS symptom presentation than men. Multiple review articles have examined sex differences in symptom presentation of ACS and these studies have yielded inconclusive results and/or inconsistent recommendations. This is largely because these studies have included diverse study populations, different methods of assessing the chief complaint and associated coronary symptoms, relatively small sample sizes of women and men, and lack of adequate adjustment for age or other potentially confounding differences between the sexes. There is a substantial overlap of ACS symptoms that are not mutually exclusive according to sex, and are generally found in women and men. However, there are apparent differences in the frequency and distribution of ACS symptoms among women and men. Women, on average, are also more likely to have a greater number of ACS-related symptoms contributing to the perception that women have more atypical symptoms than men. In this review, we address issues surrounding whether women should have a different ACS symptom presentation message than men, and provide general recommendations from a public policy perspective. In the future, our goal should be to standardize ACS symptom presentation and to elucidate the full range of ACS and myocardial infarction symptoms considering the substantial overlap of symptoms among women and men rather than use conventional terms such as "typical" and "atypical" angina. All rights reserved.

Incident comorbidities and all-cause mortality among 5-year survivors of Stage I and II breast cancer diagnosed at age 65 or older: a prospective-matched cohort study

Fri, 10/17/2014 - 11:48am

Five-year breast cancer survivors, diagnosed after 65 years of age, may develop more incident comorbidities than similar populations free of cancer. We investigated whether older breast cancer survivors have a similar comorbidity burden 6-15 years after cancer diagnosis to matched women free of breast cancer at start of follow-up and whether incident comorbidities are associated with all-cause mortality. In this prospective cohort study, 1,361 older 5-year early-stage breast cancer survivors diagnosed between 1990 and 1994 and 1,361 age- and health system-matched women were followed for 10 years. Adjudicated medical record review captured prevalent and incident comorbidities during follow-up or until death as collected from the National Death Index. Older 5-year breast cancer survivors did not acquire incident comorbidities more often than matched women free of breast cancer in the subsequent 10 years [hazard ratio (HR) 1.0, 95 % confidence interval (95 % CI) 0.93, 1.1]. Adjusted for cohort membership, women with incident comorbidities had a higher mortality rate than those without incident comorbidities (HR 4.8, 95 % CI 4.1, 5.6). A breast cancer history continued to be a hazard for mortality 6-15 years after diagnosis (HR 1.3, 95 % CI 1.1, 1.4). We found that older breast cancer survivors who developed comorbidities had an increased all-cause mortality rate even after adjusting for age and prevalent comorbidity burden. Additionally, survivors acquire comorbidities at a rate similar to older women free of breast cancer. These results highlight the association between comorbidity burden and long-term mortality risk among older breast cancer survivors and their need for appropriate oncology and primary care follow-up.

B-type natriuretic peptide and C-reactive protein in the prediction of atrial fibrillation risk: the CHARGE-AF Consortium of community-based cohort studies

Fri, 10/17/2014 - 11:48am

AIMS: B-type natriuretic peptide (BNP) and C-reactive protein (CRP) predict atrial fibrillation (AF) risk. However, their risk stratification abilities in the broad community remain uncertain. We sought to improve risk stratification for AF using biomarker information.

METHODS AND RESULTS: We ascertained AF incidence in 18 556 Whites and African Americans from the Atherosclerosis Risk in Communities Study (ARIC, n=10 675), Cardiovascular Health Study (CHS, n = 5043), and Framingham Heart Study (FHS, n = 2838), followed for 5 years (prediction horizon). We added BNP (ARIC/CHS: N-terminal pro-B-type natriuretic peptide; FHS: BNP), CRP, or both to a previously reported AF risk score, and assessed model calibration and predictive ability [C-statistic, integrated discrimination improvement (IDI), and net reclassification improvement (NRI)]. We replicated models in two independent European cohorts: Age, Gene/Environment Susceptibility Reykjavik Study (AGES), n = 4467; Rotterdam Study (RS), n = 3203. B-type natriuretic peptide and CRP were significantly associated with AF incidence (n = 1186): hazard ratio per 1-SD ln-transformed biomarker 1.66 [95% confidence interval (CI), 1.56-1.76], P < 0.0001 and 1.18 (95% CI, 1.11-1.25), P < 0.0001, respectively. Model calibration was sufficient (BNP, chi(2) = 17.0; CRP, chi(2) = 10.5; BNP and CRP, chi(2) = 13.1). B-type natriuretic peptide improved the C-statistic from 0.765 to 0.790, yielded an IDI of 0.027 (95% CI, 0.022-0.032), a relative IDI of 41.5%, and a continuous NRI of 0.389 (95% CI, 0.322-0.455). The predictive ability of CRP was limited (C-statistic increment 0.003). B-type natriuretic peptide consistently improved prediction in AGES and RS.

CONCLUSION: B-type natriuretic peptide, not CRP, substantially improved AF risk prediction beyond clinical factors in an independently replicated, heterogeneous population. B-type natriuretic peptide may serve as a benchmark to evaluate novel putative AF risk biomarkers. Cardiology 2014. This work is written by (a) US Government employee(s) and is in the public domain in the US.

Health Information-Seeking on Behalf of Others: Characteristics of "Surrogate Seekers"

Fri, 10/17/2014 - 11:48am

Understanding the behaviors of surrogate seekers (those who seek health information for others) may guide efforts to improve health information transmission. We used 2011-2012 data from the Health Information National Trends Survey to describe behaviors of online surrogate seekers. Respondents were asked about use of the Internet for surrogate-seeking over the prior 12 months. Data were weighted to calculate population estimates. Two thirds (66.6 %) reported surrogate-seeking. Compared to those who sought health information online for only themselves, surrogate seekers were more likely to live in households with others (weighted percent 89.4 vs. 82.5 % of self-seekers; p < 0.05); no significant differences in sex, race, income or education were observed. Surrogate seekers were more likely to report activities requiring user-generated content: email communication with healthcare providers; visits to social networking sites to read and share about medical topics and participation in online health support groups. On multivariate analysis, those who had looked online for healthcare providers were more likely to be surrogate seekers (OR 1.67, 95 % CI 1.08-2.59). In addition to seeking health information, surrogate seekers create and pass along communications that may influence medical care decisions. Research is needed to identify ways to facilitate transmission of accurate health information.

Providers' perceptions of communication breakdowns in cancer care

Fri, 10/17/2014 - 11:48am

BACKGROUND: Communication breakdowns in cancer care are common and represent a failure in patient-centered care. While multiple studies have elicited patients' perspectives on these breakdowns, little is known about cancer care providers' attitudes regarding the causes and potential solutions.

OBJECTIVE: To examine providers' (1) perceptions of the nature and causes of communication breakdowns with patients in cancer care and (2) suggestions for managing and preventing breakdowns.

DESIGN: Qualitative study of nine focus groups held at three sites (Massachusetts, Georgia and Washington).

PARTICIPANTS: Fifty-nine providers: 33% primary care physicians, 14% oncologists, 36% nurses, and 17% nurse practitioners, physician assistants, and others.

APPROACH: Directed content analysis of focus group transcripts.

KEY RESULTS: Providers' perceptions of the causes of communication breakdowns fell into three categories: causes related to patients, providers, or healthcare systems. Providers perceived that patients sometimes struggle to understand cancer and health-related information, have unrealistic expectations, experience emotional and psychological distress that interferes with information exchange; and may be reticent to share their confusion or concerns. Providers described their own and colleagues' contributions to these breakdowns as sharing inaccurate, conflicting, or uncoordinated information. Providers also described the difficulty in balancing hope with reality in discussions of prognosis. System issues named by providers included insufficient time with patients, payment systems, and changing protocols that inhibit communication and coordination of care. Potential solutions included greater patient engagement, team coordination, and systems that promote patient feedback.

CONCLUSIONS: Providers described multiple causes for communication breakdowns at the patient, provider, and system level. Multi-level interventions that coordinate care and encourage feedback may help to address or prevent communication breakdowns.

Density-dependent blood stage Plasmodium falciparum suppresses malaria super-infection in a malaria holoendemic population

Wed, 10/15/2014 - 12:16pm

Recent studies of Plasmodium berghei malaria in mice show that high blood-stage parasitemia levels inhibit the development of subsequent liver-stage infections. Whether a similar inhibitory effect on liver-stage Plasmodium falciparum by blood-stage infection occurs in humans is unknown. We have analyzed data from a treatment-time-to-infection cohort of children < 10 years of age residing in a malaria holoendemic area of Kenya where people experience a new blood-stage infection approximately every 2 weeks. We hypothesized that if high parasitemia blocked the liver stage, then high levels of parasitemia should be followed by a "skipped" peak of parasitemia. Statistical analysis of "natural infection" field data and stochastic simulation of infection dynamics show that the data are consistent with high P. falciparum parasitemia inhibiting liver-stage parasite development in humans.

Absence of Putative Artemisinin Resistance Mutations Among Plasmodium falciparum in Sub-Saharan Africa: A Molecular Epidemiologic Study

Wed, 10/15/2014 - 12:15pm

Plasmodium falciparum parasites that are resistant to artemisinins have been detected in Southeast Asia. Resistance is associated with several polymorphisms in the parasite's K13-propeller gene. The molecular epidemiology of these artemisinin resistance genotypes in African parasite populations is unknown. We developed an assay to quantify rare polymorphisms in parasite populations that uses a pooled deep-sequencing approach to score allele frequencies, validated it by evaluating mixtures of laboratory parasite strains, and then used it to screen P. falciparum parasites from >1100 African infections collected since 2002 from 14 sites across sub-Saharan Africa. We found no mutations in African parasite populations that are associated with artemisinin resistance in Southeast Asian parasites. However, we observed 15 coding mutations, including 12 novel mutations, and limited allele sharing between parasite populations, consistent with a large reservoir of naturally occurring K13-propeller variation. Although polymorphisms associated with artemisinin resistance in P. falciparum in Southeast Asia are not prevalent in sub-Saharan Africa, numerous K13-propeller coding polymorphisms circulate in Africa. Although their distributions do not support a widespread selective sweep for an artemisinin-resistant phenotype, the impact of these mutations on artemisinin susceptibility is unknown and will require further characterization. Rapid, scalable molecular surveillance offers a useful adjunct in tracking and containing artemisinin resistance. Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail:

Interleukin-6 and interleukin-10 gene promoter polymorphisms and risk of endemic burkitt lymphoma

Wed, 10/15/2014 - 12:15pm

Overexpression of interleukin-6 (IL-6) and IL-10 in endemic Burkitt lymphoma (eBL) may facilitate tumorigenesis by providing a permissive cytokine milieu. Promoter polymorphisms influence interindividual differences in cytokine production. We hypothesized that children genetically predisposed for elevated cytokine levels may be more susceptible to eBL. Using case-control samples from western Kenya consisting of 117 eBL cases and 88 ethnically matched healthy controls, we tested for the association between eBL risk and IL-10 (rs1800896, rs1800871, and rs1800872) and IL-6 (rs1800795) promoter single nucleotide polymorphisms (SNPs) as well as IL-10 promoter haplotypes. In addition, the association between these variants and Epstein Barr Virus (EBV) load was examined. Results showed that selected IL-10 and IL-6 promoter SNPs and IL-10 promoter haplotypes were not associated with risk eBL or EBV levels in EBV-seropositive children. Findings from this study reveal that common variants within the IL-10 and IL-6 promoters do not independently increase eBL risk in this vulnerable population.

Linda Cabral and Jillian Richard-Daniels on Using Qualitative Data Collection to Better Understand Measure Development and Reporting

Tue, 10/14/2014 - 2:11pm

Blog post to AEA365, a blog sponsored by the American Evaluation Association (AEA) dedicated to highlighting Hot Tips, Cool Tricks, Rad Resources, and Lessons Learned for evaluators. The American Evaluation Association is an international professional association of evaluators devoted to the application and exploration of program evaluation, personnel evaluation, technology, and many other forms of evaluation. Evaluation involves assessing the strengths and weaknesses of programs, policies, personnel, products, and organizations to improve their effectiveness.

Emily Lauer and Courtney Dutra on Person-Centered Evaluation: Aging and Disability Services

Tue, 10/14/2014 - 2:11pm

Blog post to AEA365, a blog sponsored by the American Evaluation Association (AEA) dedicated to highlighting Hot Tips, Cool Tricks, Rad Resources, and Lessons Learned for evaluators. The American Evaluation Association is an international professional association of evaluators devoted to the application and exploration of program evaluation, personnel evaluation, technology, and many other forms of evaluation. Evaluation involves assessing the strengths and weaknesses of programs, policies, personnel, products, and organizations to improve their effectiveness.

Sherry Campanelli and Laura Newhall on Facilitation Not Dictation: How a QI Team Succeeds

Tue, 10/14/2014 - 2:11pm

Blog post to AEA365, a blog sponsored by the American Evaluation Association (AEA) dedicated to highlighting Hot Tips, Cool Tricks, Rad Resources, and Lessons Learned for evaluators. The American Evaluation Association is an international professional association of evaluators devoted to the application and exploration of program evaluation, personnel evaluation, technology, and many other forms of evaluation. Evaluation involves assessing the strengths and weaknesses of programs, policies, personnel, products, and organizations to improve their effectiveness.

A Spider, an Octopus, or an Animal Just Coming into Existence? Designing a Curriculum for Librarians to Support Research Data Management

Tue, 10/14/2014 - 10:00am

The paper explains the approach taken in the UK Jisc-funded RDMRose project to developing a study module/Open Educational Resource about Research Data Management (RDM) for librarians. The resource was developed collaboratively between the University of Sheffield Information School and the libraries at the Universities of Leeds, Sheffield, and York. Curriculum design principles such as an emphasis on exploring the nature of research and on other professional services supporting RDM were based on requirements gathered from focus groups and the literature. The content of the eight half-day sessions is briefly outlined. The paper goes on to explore how the learning materials were evaluated by this first cohort of learners and readjusted to respond to feedback. Future plans for co-producing an RDM related learning resource through a student-centered process and to create a sustainable learning network are discussed.

Digital anthropomorphic phantoms of non-rigid human respiratory and voluntary body motion for investigating motion correction in emission imaging

Sun, 10/12/2014 - 1:20pm

The development of methods for correcting patient motion in emission tomography has been receiving increased attention. Often the performance of these methods is evaluated through simulations using digital anthropomorphic phantoms, such as the commonly used extended cardiac torso (XCAT) phantom, which models both respiratory and cardiac motion based on human studies. However, non-rigid body motion, which is frequently seen in clinical studies, is not present in the standard XCAT phantom. In addition, respiratory motion in the standard phantom is limited to a single generic trend. In this work, to obtain a more realistic representation of motion, we developed a series of individual-specific XCAT phantoms, modeling non-rigid respiratory and non-rigid body motions derived from the magnetic resonance imaging (MRI) acquisitions of volunteers. Acquisitions were performed in the sagittal orientation using the Navigator methodology. Baseline (no motion) acquisitions at end-expiration were obtained at the beginning of each imaging session for each volunteer. For the body motion studies, MRI was again acquired only at end-expiration for five body motion poses (shoulder stretch, shoulder twist, lateral bend, side roll, and axial slide). For the respiratory motion studies, an MRI was acquired during free/regular breathing. The magnetic resonance slices were then retrospectively sorted into 14 amplitude-binned respiratory states, end-expiration, end-inspiration, six intermediary states during inspiration, and six during expiration using the recorded Navigator signal. XCAT phantoms were then generated based on these MRI data by interactive alignment of the organ contours of the XCAT with the MRI slices using a graphical user interface. Thus far we have created five body motion and five respiratory motion XCAT phantoms from the MRI acquisitions of six healthy volunteers (three males and three females). Non-rigid motion exhibited by the volunteers was reflected in both respiratory and body motion phantoms with a varying extent and character for each individual. In addition to these phantoms, we recorded the position of markers placed on the chest of the volunteers for the body motion studies, which could be used as external motion measurement. Using these phantoms and external motion data, investigators will be able to test their motion correction approaches for realistic motion obtained from different individuals. The non-uniform rational B-spline data and the parameter files for these phantoms are freely available for downloading and can be used with the XCAT license.

MRI Investigation of the Linkage Between Respiratory Motion of the Heart and Markers on Patient's Abdomen and Chest: Implications for Respiratory Amplitude Binning List-Mode PET and SPECT Studies

Sun, 10/12/2014 - 1:20pm

Respiratory motion of the heart impacts the diagnostic accuracy of myocardial-perfusion emission-imaging studies. Amplitude binning has come to be the method of choice for binning list-mode based acquisitions for correction of respiratory motion in PET and SPECT. In some subjects respiratory motion exhibits hysteretic behavior similar to damped non-linear cyclic systems. The detection and correction of hysteresis between the signals from surface movement of the patient's body used in binning and the motion of the heart within the chest remains an open area for investigation. This study reports our investigation in nine volunteers of the combined MRI tracking of the internal respiratory motion of the heart using Navigators with stereo-tracking of markers on the volunteer's chest and abdomen by a visual-tracking system (VTS). The respiratory motion signals from the internal organs and the external markers were evaluated for hysteretic behavior analyzing the temporal correspondence of the signals. In general, a strong, positive correlation between the external marker motion (AP direction) and the internal heart motion (SI direction) during respiration was observed. The average +/- standard deviation in the Spearman's ranked correlation coefficient (rho) over the nine volunteer studied was 0.92 +/- 0.1 between the external abdomen marker and the internal heart, and 0.87 +/- 0.2 between the external chest marker and the internal heart. However despite the good correlation on average for the nine volunteers, in three studies a poor correlation was observed due to hysteretic behavior between inspiration and expiration for either the chest marker and the internal motion of the heart, or the abdominal marker and the motion of the heart. In all cases we observed a good correlation of at least either the abdomen or the chest with the heart. Based on this result, we propose the use of marker motion from both the chest and abdomen regions when estimating the internal heart motion to detect and address hysteresis when binning list-mode emission data.

An evaluation of data-driven motion estimation in comparison to the usage of external-surrogates in cardiac SPECT imaging

Sun, 10/12/2014 - 1:20pm

Motion estimation methods in single photon emission computed tomography (SPECT) can be classified into methods which depend on just the emission data (data-driven), or those that use some other source of information such as an external surrogate. The surrogate-based methods estimate the motion exhibited externally which may not correlate exactly with the movement of organs inside the body. The accuracy of data-driven strategies on the other hand is affected by the type and timing of motion occurrence during acquisition, the source distribution, and various degrading factors such as attenuation, scatter, and system spatial resolution. The goal of this paper is to investigate the performance of two data-driven motion estimation schemes based on the rigid-body registration of projections of motion-transformed source distributions to the acquired projection data for cardiac SPECT studies. Comparison is also made of six intensity based registration metrics to an external surrogate-based method. In the data-driven schemes, a partially reconstructed heart is used as the initial source distribution. The partially-reconstructed heart has inaccuracies due to limited angle artifacts resulting from using only a part of the SPECT projections acquired while the patient maintained the same pose. The performance of different cost functions in quantifying consistency with the SPECT projection data in the data-driven schemes was compared for clinically realistic patient motion occurring as discrete pose changes, one or two times during acquisition. The six intensity-based metrics studied were mean-squared difference, mutual information, normalized mutual information (NMI), pattern intensity (PI), normalized cross-correlation and entropy of the difference. Quantitative and qualitative analysis of the performance is reported using Monte-Carlo simulations of a realistic heart phantom including degradation factors such as attenuation, scatter and system spatial resolution. Further the visual appearance of motion-corrected images using data-driven motion estimates was compared to that obtained using the external motion-tracking system in patient studies. Pattern intensity and normalized mutual information cost functions were observed to have the best performance in terms of lowest average position error and stability with degradation of image quality of the partial reconstruction in simulations. In all patients, the visual quality of PI-based estimation was either significantly better or comparable to NMI-based estimation. Best visual quality was obtained with PI-based estimation in one of the five patient studies, and with external-surrogate based correction in three out of five patients. In the remaining patient study there was little motion and all methods yielded similar visual image quality.

Comparison of methods of acquiring attenuation maps for cardiac SPECT in the presence of respiratory motion

Sun, 10/12/2014 - 1:20pm

BACKGROUND: We investigated the effect of the respiratory motion on attenuation-corrected (AC) SPECT images for three different SPECT systems, each using a different approach in obtaining attenuation maps: scanning-line sources (SLS) acquired simultaneous with emission; slow cone-beam CT (CBCT) acquired sequentially to emission; and fast helical CT (HCT) acquired sequentially to emission. METHODS: A torso phantom filled with (99m)Tc was used to model a cardiac perfusion study. Stationary baseline acquisitions were followed by the acquisitions with the phantom moving axially using a computer-controlled motion platform to simulate breathing. In addition, HCT acquisitions were made simulating breath-hold at different extents of misalignment between CT and emission. HCT images were also used to simulate the Average-CT method. Acquisitions were repeated with added breast attachments, and the heart insert in two different orientations. Visual comparison was made of AC maps, AC emission slices and polar maps. Quantitative comparisons were made of global uniformity based on the percent fractional standard deviation (%FSD) of the polar map segment values, and the ratio of the segment values in the Anterior and Inferior walls divided by that of the Lateral and Septal walls (AI/LS ratio). RESULTS: The AC maps for the SLS were inferior to the CT's, and most impacted by added large breast attachment. Motion artifacts seen on CBCT slices were minimized in the derived attenuation maps. AC maps obtained from HCT showed inconsistent organ sizes depending on the direction of respiration at the time of acquisition. Both visually and quantitatively CBCT resulted in the best uniformity (up to 3.4 % lower in %FSD) for all the stationary acquisitions, and for the motion acquisition of the female phantom with large breast attachment (up to 4.0 % lower). For the motion acquisition of the male phantoms, HCT resulted in slightly better uniformity (<0.5 % lower) than CBCT. Breath-hold at end-expiration slightly improved (up to 1.1 %) the uniformity over the HCT acquired during regular breathing. Further improvement was achieved with the Average-CT method. For all the systems, phantom respiratory motion reduced the AI/LS ratio compared to when the phantoms were stationary. CONCLUSIONS: The CBCT approach resulted in the best uniformity of the AC emission images. For the female phantom with larger breast attachment, HCT and SLS were truncated at some projection angles introducing artifacts into the AC emission images. The emission image artifacts observed with HCT could be mitigated by performing breath-hold acquisition at end-expiration or Average-CT type acquisitions.

A method to synchronize signals from multiple patient monitoring devices through a single input channel for inclusion in list-mode acquisitions

Sun, 10/12/2014 - 1:20pm

PURPOSE: This technical note documents a method that the authors developed for combining a signal to synchronize a patient-monitoring device with a second physiological signal for inclusion into list-mode acquisition. Our specific application requires synchronizing an external patient motion-tracking system with a medical imaging system by multiplexing the tracking input with the ECG input. The authors believe that their methodology can be adapted for use in a variety of medical imaging modalities including single photon emission computed tomography (SPECT) and positron emission tomography (PET). METHODS: The authors insert a unique pulse sequence into a single physiological input channel. This sequence is then recorded in the list-mode acquisition along with the R-wave pulse used for ECG gating. The specific form of our pulse sequence allows for recognition of the time point being synchronized even when portions of the pulse sequence are lost due to collisions with R-wave pulses. This was achieved by altering our software used in binning the list-mode data to recognize even a portion of our pulse sequence. Limitations on heart rates at which our pulse sequence could be reliably detected were investigated by simulating the mixing of the two signals as a function of heart rate and time point during the cardiac cycle at which our pulse sequence is mixed with the cardiac signal. RESULTS: The authors have successfully achieved accurate temporal synchronization of our motion-tracking system with acquisition of SPECT projections used in 17 recent clinical research cases. In our simulation analysis the authors determined that synchronization to enable compensation for body and respiratory motion could be achieved for heart rates up to 125 beats-per-minute (bpm). CONCLUSIONS: Synchronization of list-mode acquisition with external patient monitoring devices such as those employed in motion-tracking can reliably be achieved using a simple method that can be implemented using minimal external hardware and software modification through a single input channel, while still recording cardiac gating signals.

Use of MRI to assess the prediction of heart motion with gross body motion in myocardial perfusion imaging by stereotracking of markers on the body surface

Sun, 10/12/2014 - 1:20pm

PURPOSE: The aim of this study is to determine using MRI in volunteers whether the rigid-body-motion (RBM) model can be approximately used to estimate the gross body-motion of the heart from that of external markers on patient's chest. Our target clinical application is to use a visual-tracking-system (VTS) which employs stereoimaging to estimate heart motion during SPECT/CT and PETCT myocardial perfusion imaging. METHODS: To investigate body-motion separate from the respiration the authors had the volunteers hold their breath during the acquisition of a sequence of two sets of EKG-triggered MRI sagittal slices. The first set was acquired pre-motion, and the second postmotion. The motion of the heart within each breath-hold set of slices was estimated by registration to the semiautomatic 3D segmentation of the heart region in a baseline set acquired using the Navigator technique. The motion of the heart between the pre- and postmotion sets was then determined as the difference in the individual motions in comparison to the Navigator sets. An analysis of the combined motion of the individual markers on the chest was used to obtain an estimate of the six-degree-of-freedom RBM from the VTS system. The metric for judging agreement between the motion estimated by MRI and the VTS was the average error. This was defined as the average of the magnitudes of the differences in the vector displacements of all voxels in the heart region. Studies with the Data Spectrum Anthropomorphic Phantom and "No-Motion" studies in which the volunteer did not intentionally move were used to establish a baseline for agreement. With volunteer studies a t-test was employed to determine when statistically significant differences in Average Errors occurred compared to the No-motion studies. RESULTS: For phantom acquisitions, the Average Error when the motion was just translation was 0.1 mm. With complex motions, which included a combination of rotations and translations, the Average Error increased to 3.6 mm. In the volunteers the Average Error averaged over all No-Motion acquisitions was 1.0 mm. For the case of translational motion, which might be expected to be RBM, the Average Error averaged over all volunteer studies increased to 2.6 mm, which was statistically different from the No-Motion studies. For the case of bends and twists of the torso, which would be expected to challenge the RBM model, the Average Error averaged over all such volunteer studies was 4.9 mm and was again statistically different. Investigations of motion of the arm including just bending at the elbow and leg motion resulted in Average Errors which were not statistically different from the No-Motion studies. However, when shoulder movement was included with arm motion the Average Error was near that of torso bends and twists, and statistically different. CONCLUSIONS: Use of the RBM model with VTS predictions of heart motion during reconstruction should decrease the extent of artifacts for the types of patient motion studied. The impact of correction would be less for torso bends and twists, and arm motion which includes the shoulders.