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ABSTRACT: The purpose of this study is to evaluate combined time-resolved and high-spatial resolution contrast-enhanced MR angiography (MRA) for assessment of cavopulmonary connections in adult patients with congenital heart disease.
Twenty-eight adults with various surgical cavopulmonary connections (Glenn shunt and Fontan connection) underwent high-spatial-resolution contrast-enhanced MRA (voxel size, 1.95 mm(3); temporal resolution, 22 seconds) and time-resolved contrast-enhanced MRA (voxel size, 6.5-9.3 mm(3); temporal resolution, < 1.2 seconds). Ten patients had 2D phase contrast flow quantification measurements performed at the same setting. Two readers independently assessed anatomic dimensions of cavopulmonary connections (using high-spatial-resolution contrast-enhanced MRA) and pulmonary artery (PA) perfusion patterns (using time-resolved contrast-enhanced MRA).
High-spatial-resolution contrast-enhanced MRA yielded diagnostic-quality images for morphologic assessment of cavopulmonary connections in 27 of 28 (96%) patients. The anatomic dimensions (cross-sectional area) of the PA and cavopulmonary connections showed a wide variation (right PA, 0.99-5.67 cm(2); left PA, 0.80-5.69 cm(2); Glenn shunt, 0.93-6.94 cm(2); and Fontan connection, 1.25-6.67 cm(2)). The anatomic dimensions could be assessed with excellent interobserver agreement on high-spatial-resolution contrast-enhanced MRA (r = 0.895). Time-resolved contrast-enhanced MRA yielded diagnostic-quality images in all patients and enabled characterization of PA perfusion via the superior vena cava as follows: preferential inflow to the right PA (n = 12), preferential inflow to the left PA (n = 5), and balanced inflow to the right and left PA (n = 11). In those patients who had technically successful flow quantification measurements, phase contrast data confirmed patency of the cavopulmonary connections.
Combined time-resolved contrast-enhanced MRA and high-spatial-resolution contrast-enhanced MRA allowed detailed morphologic and dynamic evaluation of cavopulmonary connections in adult patients with congenital heart disease. A wide variation in anatomic dimensions and perfusion patterns was confidently identified in this patient population.
American Journal of Roentgenology 11/2012; 199(5):W565-74. · 2.78 Impact Factor
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George Bartzokis,
Po H Lu,
Panthea Heydari,
Alexander Couvrette,
Grace J Lee,
Greta Kalashyan,
Frank Freeman,
John W Grinstead,
Pablo Villablanca, J Paul Finn,
Jim Mintz,
Jeffry R Alger,
Lori L Altshuler
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ABSTRACT: BACKGROUND: Postmortem and volumetric imaging data suggest that brain myelination is a dynamic lifelong process that, in vulnerable late-myelinating regions, peaks in middle age. We examined whether known regional differences in axon size and age at myelination influence the timing and rates of development and degeneration/repair trajectories of white matter (WM) microstructure biomarkers. METHODS: Healthy subjects (n = 171) 14-93 years of age were examined with transverse relaxation rate (R(2)) and four diffusion tensor imaging measures (fractional anisotropy [FA] and radial, axial, and mean diffusivity [RD, AxD, MD, respectively]) of frontal lobe, genu, and splenium of the corpus callosum WM (FWM, GWM, and SWM, respectively). RESULTS: Only R(2) reflected known levels of myelin content with high values in late-myelinating FWM and GWM regions and low ones in early-myelinating SWM. In FWM and GWM, all metrics except FA had significant quadratic components that peaked at different ages (R(2) < RD < MD < AxD), with FWM peaking later than GWM. Factor analysis revealed that, although they defined different factors, R(2) and RD were the metrics most closely associated with each other and differed from AxD, which entered into a third factor. CONCLUSIONS: The R(2) and RD trajectories were most dynamic in late-myelinating regions and reflect age-related differences in myelination, whereas AxD reflects axonal size and extra-axonal space. The FA and MD had limited specificity. The data suggest that the healthy adult brain undergoes continual change driven by development and repair processes devoted to creating and maintaining synchronous function among neural networks on which optimal cognition and behavior depend.
Biological psychiatry 09/2012; · 8.93 Impact Factor
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Journal of Cardiovascular Magnetic Resonance 05/2012; 13:1-1. · 3.72 Impact Factor
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Journal of Cardiovascular Magnetic Resonance 05/2012; 12:1-2. · 3.72 Impact Factor
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ABSTRACT: Catheter rupture during CT angiography has prompted policies prohibiting the use of electronic injectors with peripherally inserted central venous catheters (PICCs) not only for CT but also for MRI. Consequently, many institutions mandate hand injection for MR angiography, limiting precision of infusion rates and durations of delivery.
To determine whether electronic injection of gadolinium-based contrast media through a range of small-caliber, single-lumen PICCs would be safe without risk of catheter rupture over the range of clinical protocols and determine whether programmed flow rates and volumes were realized when using PICCs for contrast delivery.
Experiments were performed and recorded using the Medrad Spectris Solaris EP MR Injection System. PICC sizes, contrast media and flow rates were based on common institutional protocols.
No catheters were damaged during any experiments. Mean difference between programmed and delivered volume was 0.07 ± 0.10 mL for all experiments. Reduced flow rates and prolonged injection durations were observed when the injector's pressure-limiting algorithm was triggered, only in protocols outside the clinical range.
PICCs commonly used in children can withstand in vitro power injection of gadolinium-based contrast media at protocols significantly above clinical levels.
Pediatric Radiology 04/2012; 42(9):1064-9. · 1.67 Impact Factor
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Journal of Cardiovascular Magnetic Resonance 02/2012; 14 Suppl 1:P270. · 3.72 Impact Factor
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ABSTRACT: Radiofrequency induced pacemaker lead tip heating is one of the main reasons magnetic resonance imaging (MRI) is contraindicated for patients with pacemakers. The objective of this work was to evaluate the dependence of pacemaker lead tip heating during MRI scanning on the electrical conductivity of the medium surrounding the pacemaker lead tip. The effect of conductivity was measured using hydroxyethyl cellulose, polyacrylic acid, and saline with conductivities ranging from 0 to 3 S/m which spans the range of human tissue conductivity. The maximum lead tip heating observed in polyacrylic acid was 50.4 °C at 0.28 S/m, in hydroxyethyl cellulose the maximum was 36.8 °C at 0.52 S/m, and in saline the maximum was 12.5 °C at 0.51 S/m. The maximum power transfer theorem was used to calculate the relative power deposited in the solution based on the characteristic impedance of the pacemaker lead and test solution impedance. The results demonstrate a strong correlation between the relative power deposited and pacemaker lead tip heating for hydroxyethyl cellulose and saline solutions. Maximum power deposition occurred when the impedance of the solution matched the pacemaker lead impedance. Pacemaker lead tip heating is dependent upon the electrical conductivity of the solution at the lead tip and should be considered when planning in vitro gel or saline experiments.
Magnetic Resonance in Medicine 12/2011; 68(2):606-13. · 2.96 Impact Factor
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Carissa G Fonseca,
Michael Backhaus,
David A Bluemke,
Randall D Britten,
Jae Do Chung,
Brett R Cowan,
Ivo D Dinov, J Paul Finn,
Peter J Hunter,
Alan H Kadish,
Daniel C Lee,
Joao A C Lima,
Pau Medrano-Gracia,
Kalyanam Shivkumar,
Avan Suinesiaputra,
Wenchao Tao,
Alistair A Young
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ABSTRACT: Integrative mathematical and statistical models of cardiac anatomy and physiology can play a vital role in understanding cardiac disease phenotype and planning therapeutic strategies. However, the accuracy and predictive power of such models is dependent upon the breadth and depth of noninvasive imaging datasets. The Cardiac Atlas Project (CAP) has established a large-scale database of cardiac imaging examinations and associated clinical data in order to develop a shareable, web-accessible, structural and functional atlas of the normal and pathological heart for clinical, research and educational purposes. A goal of CAP is to facilitate collaborative statistical analysis of regional heart shape and wall motion and characterize cardiac function among and within population groups.
Three main open-source software components were developed: (i) a database with web-interface; (ii) a modeling client for 3D + time visualization and parametric description of shape and motion; and (iii) open data formats for semantic characterization of models and annotations. The database was implemented using a three-tier architecture utilizing MySQL, JBoss and Dcm4chee, in compliance with the DICOM standard to provide compatibility with existing clinical networks and devices. Parts of Dcm4chee were extended to access image specific attributes as search parameters. To date, approximately 3000 de-identified cardiac imaging examinations are available in the database. All software components developed by the CAP are open source and are freely available under the Mozilla Public License Version 1.1 (http://www.mozilla.org/MPL/MPL-1.1.txt).
http://www.cardiacatlas.org
a.young@auckland.ac.nz
Supplementary data are available at Bioinformatics online.
Bioinformatics 08/2011; 27(16):2288-95. · 5.47 Impact Factor
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Pacing and Clinical Electrophysiology 07/2011; 34(9):1051-3. · 1.35 Impact Factor
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ABSTRACT: Over the last decade, three-dimensional contrast-enhanced magnetic resonance angiography (CE-MRA) has emerged as a widely accepted and powerful technique for diagnostic assessment of almost all vascular territories. Its non-invasive nature and lack of ionizing radiation, its potential to cover a large field of view and the safety of gadolinium-based contrast agents make CE-MRA an appealing alternative to digital subtraction angiography (DSA) or computed tomography angiography (CTA). However, recent reports linking high dose gadolinium-based contrast agents to the development of nephrogenic systemic fibrosis [1-3] have raised concerns over the safety of CE-MRA. As a result, many investigators have focused attention on gadolinium dose reduction strategies [4,5]. This article reviews existing state-of-the-art 3D CE-MRA strategies to reduce contrast dose and summarizes current applications and clinical experience to date. It also highlights evolving techniques, which the authors feel are likely to enhance the future impact of CE-MRA.
European journal of radiology 03/2011; 80(1):2-8. · 2.65 Impact Factor
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George Bartzokis,
Po H Lu,
Kathleen Tingus,
Douglas G Peters,
Chetan P Amar,
Todd A Tishler, J Paul Finn,
Pablo Villablanca,
Lori L Altshuler,
Jim Mintz,
Elizabeth Neely,
James R Connor
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ABSTRACT: Brain iron increases with age and is abnormally elevated early in the disease process in several neurodegenerative disorders that impact memory including Alzheimer's disease (AD). Higher brain iron levels are associated with male gender and presence of highly prevalent allelic variants in genes encoding for iron metabolism proteins (hemochromatosis H63D (HFE H63D) and transferrin C2 (TfC2)). In this study, we examined whether in healthy older individuals memory performance is associated with increased brain iron, and whether gender and gene variant carrier (IRON+) vs noncarrier (IRON-) status (for HFE H63D/TfC2) modify the associations. Tissue iron deposited in ferritin molecules can be measured in vivo with magnetic resonance imaging utilizing the field-dependent relaxation rate increase (FDRI) method. FDRI was assessed in hippocampus, basal ganglia, and white matter, and IRON+ vs IRON- status was determined in a cohort of 63 healthy older individuals. Three cognitive domains were assessed: verbal memory (delayed recall), working memory/attention, and processing speed. Independent of gene status, worse verbal-memory performance was associated with higher hippocampal iron in men (r=-0.50, p=0.003) but not in women. Independent of gender, worse verbal working memory performance was associated with higher basal ganglia iron in IRON- group (r=-0.49, p=0.005) but not in the IRON+ group. Between-group interactions (p=0.006) were noted for both of these associations. No significant associations with white matter or processing speed were observed. The results suggest that in specific subgroups of healthy older individuals, higher accumulations of iron in vulnerable gray matter regions may adversely impact memory functions and could represent a risk factor for accelerated cognitive decline. Combining genetic and MRI biomarkers may provide opportunities to design primary prevention clinical trials that target high-risk groups.
Neuropsychopharmacology: official publication of the American College of Neuropsychopharmacology 03/2011; 36(7):1375-84. · 6.99 Impact Factor
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ABSTRACT: To assess the risk of RF-induced heating in pacemaker-attached and abandoned leads using in vitro temperature measurements at 1.5 Tesla as a function of lead length.
Five custom lead lengths, 20-60 cm, were exposed to a uniform magnitude and phase radiofrequency electric field to examine the effect of lead length on pacemaker lead tip heating for pacemaker-attached and abandoned pacemaker leads.
Abandoned and pacemaker-attached leads show resonant heating behavior and maximum heating occurs at different lead lengths due to the differences in termination conditions. For clinical lead lengths (40-60 cm) abandoned leads exhibited greater lead tip heating compared with pacemaker-attached leads.
Current recommendations for MRI pacemaker safety should highlight the possible increased risk for patients with abandoned leads as compared to pacemaker-attached leads.
Journal of Magnetic Resonance Imaging 02/2011; 33(2):426-31. · 2.70 Impact Factor
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ABSTRACT: Definition of myocardial scars as identified by electroanatomic mapping is integral to catheter ablation of ventricular tachycardia (VT). Myocardial imaging can also identify scars prior to ablation. However, the relationship between imaging and voltage mapping is not well characterized.
The purpose of this study was to verify the anatomic location and heterogeneity of scars as obtained by electroanatomic mapping with contrast-enhanced MRI (CeMRI) and histopathology, and to characterize the distribution of late potentials in a chronic porcine infarct model.
In vivo 3-dimensional cardiac CeMRI was performed in 5 infarcted porcine hearts. High-density electroanatomic mapping was used to generate epicardial and endocardial voltage maps. Scar surface area and position on CeMRI were then correlated with voltage maps. Locations of late potentials were subsequently identified. These were classified according to their duration and fractionation. All hearts underwent histopathological examination after mapping.
The total dense scar surface area and location on CeMRI correlated to the total epicardial and endocardial surface scar on electroanatomic maps. Electroanatomic mapping (average of 1,532 ± 480 points per infarcted heart) showed that fractionated late potentials were more common in dense scars (<0.50 mV) as compared with border zone regions (0.51 to 1.5 mV), and were more commonly observed on the epicardium.
In vivo, CeMRI can identify areas of transmural and nontransmural dense scars. Fractionated late diastolic potentials are more common on the epicardium than the endocardium in dense scar. These findings have implications for catheter ablation of VT and for targeting the delivery of future therapies to scarred regions.
Heart rhythm: the official journal of the Heart Rhythm Society 02/2011; 8(7):1060-7. · 4.56 Impact Factor
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Society of Vascular Surgery. 01/2011;
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ABSTRACT: The Cardiac Atlas Project seeks to establish a standardized database of cardiovascular imaging examinations, together with
derived analyses, for the purposes of statistical characterization of global and regional heart function abnormalities. We
present preliminary results from a subset of cases contributed from the Defibrillators to Reduce Risk by Magnetic Resonance
Imaging Evaluation (DETERMINE) study of patients with myocardial infarction. Finite element models were fitted to the epicardial
and endocardial surfaces throughout the cardiac cycle in 200 patients using a standardized procedure. The control points of
the shape model were used in a principal component analysis of shape and motion. The modes were associated with well-known
clinical indices of adverse remodeling in heart disease, including heart size, sphericity and mitral valve geometry. These
results therefore show promise for the clinical application of a statistical analysis of shape and motion in patients with
myocardial infarction.
KeywordsStatistical Shape Model-Principal Component Analysis-Cardiac Magnetic Resonance Imaging (MRI)-Finite Element Modeling
09/2010: pages 46-53;
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Carissa G. Fonseca,
Michael Backhaus,
Jae Do Chung,
Wenchao Tao,
Pau Medrano-Gracia,
Brett R. Cowan,
Peter J. Hunter, J. Paul Finn,
Kalyanam Shivkumar,
Joao A. C. Lima,
David A. Bluemke,
Alan H. Kadish,
Daniel C. Lee,
Alistair A. Young
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ABSTRACT: The Cardiac Atlas Project (CAP) is a NIH sponsored international collaboration to establish a web-accessible structural and
functional atlas of the normal and pathological heart as a resource for the clinical, research and educational communities.
An initial goal of the atlas is to facilitate statistical analysis of regional heart shape and wall motion characteristics,
and characterization of remodeling, between and within population groups. The two main early contributing studies are the
Multi Ethnic Study of Atherosclerosis (MESA) and the Defibrillators to Reduce Risk by Magnetic Resonance Imaging Evaluation
(DETERMINE) clinical trial. De-identified image and text data from 2864 asymptomatic volunteers from MESA, and 470 myocardial
infarction cases from DETERMINE, are currently available in the CAP database. DICOM images were de-identified using HIPAA
compliant software based on tools provided by the Center for Computational Biology at UCLA. Only those cases with informed
consent and IRB approval compatible with the CAP were included. Researchers requesting permission to access CAP data can apply
through the CAP website (www.cardiacatlas.org). All proposals for data access must be approved by the data contributors, and
applicants must sign a data transfer agreement with each study from which data is requested. Software to visualize cardiac
images and create 3D mathematical models, developed in the CAP, is available open-source from the website.
KeywordsComputational Atlas-Database-Cardiac-Mapping
09/2010: pages 36-45;
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ABSTRACT: The grading of pulmonary regurgitation (PR) severity by two-dimensional (2D) and Doppler echocardiography is not standardized. Cardiovascular magnetic resonance imaging is the clinical gold standard for PR quantification. The purpose of this study was to determine the best 2D and Doppler echocardiographic predictors of severe PR.
Thirty-six patients with tetralogy of Fallot or pulmonary valve stenosis with prior pulmonary valvuloplasty or transannular or subannular patch repair underwent 2D and Doppler echocardiography and cardiovascular magnetic resonance. Two-dimensional and Doppler echocardiographic measurements used to predict severe PR included diastolic flow reversal in the main or branch pulmonary arteries, PR jet width > or = 50% of the pulmonary annulus, PR pressure half-time < 100 ms, and PR index < 0.77.
With the exception of PR index, all indices were significant independent predictors of severe PR. The best univariate predictor of severe PR was branch pulmonary artery diastolic flow reversal.
Two-dimensional and Doppler echocardiography reliably identified severe PR in this cohort.
Journal of the American Society of Echocardiography: official publication of the American Society of Echocardiography 08/2010; 23(8):880-6. · 2.98 Impact Factor
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W Gregory Hundley,
David A Bluemke, J Paul Finn,
Scott D Flamm,
Mark A Fogel,
Matthias G Friedrich,
Vincent B Ho,
Michael Jerosch-Herold,
Christopher M Kramer,
Warren J Manning,
Manesh Patel,
Gerald M Pohost,
Arthur E Stillman,
Richard D White,
Pamela K Woodard
Circulation 06/2010; 121(22):2462-508. · 14.74 Impact Factor
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W Gregory Hundley,
David A Bluemke, J Paul Finn,
Scott D Flamm,
Mark A Fogel,
Matthias G Friedrich,
Vincent B Ho,
Michael Jerosch-Herold,
Christopher M Kramer,
Warren J Manning,
Manesh Patel,
Gerald M Pohost,
Arthur E Stillman,
Richard D White,
Pamela K Woodard
Journal of the American College of Cardiology 06/2010; 55(23):2614-62. · 14.16 Impact Factor
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George Bartzokis,
Po H Lu,
Todd A Tishler,
Douglas G Peters,
Anastasia Kosenko,
Katherine A Barrall, J Paul Finn,
Pablo Villablanca,
Gerhard Laub,
Lori L Altshuler,
Daniel H Geschwind,
Jim Mintz,
Elizabeth Neely,
James R Connor
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ABSTRACT: Prevalent gene variants involved in iron metabolism [hemochromatosis (HFE) H63D and transferrin C2 (TfC2)] have been associated with higher risk and earlier age at onset of Alzheimer's disease (AD), especially in men. Brain iron increases with age, is higher in men, and is abnormally elevated in several neurodegenerative diseases, including AD and Parkinson's disease, where it has been reported to contribute to younger age at onset in men. The effects of the common genetic variants (HFE H63D and/or TfC2) on brain iron were studied across eight brain regions (caudate, putamen, globus pallidus, thalamus, hippocampus, white matter of frontal lobe, genu, and splenium of corpus callosum) in 66 healthy adults (35 men, 31 women) aged 55 to 76. The iron content of ferritin molecules (ferritin iron) in the brain was measured with MRI utilizing the Field Dependent Relaxation Rate Increase (FDRI) method. 47% of the sample carried neither genetic variant (IRON-) and 53% carried one and/or the other (IRON+). IRON+ men had significantly higher FDRI compared to IRON- men (p=0.013). This genotype effect was not observed in women who, as expected, had lower FDRI than men. This is the first published evidence that these highly prevalent genetic variants in iron metabolism genes can influence brain iron levels in men. Clinical phenomena such as differential gender-associated risks of developing neurodegenerative diseases and age at onset may be associated with interactions between iron genes and brain iron accumulation. Clarifying mechanisms of brain iron accumulation may help identify novel interventions for age-related neurodegenerative diseases.
Journal of Alzheimer's disease: JAD 02/2010; 20(1):333-41. · 3.74 Impact Factor
