A hydro-economic model of South Florida water resources system.

South Florida's water infrastructure and ecosystems are under pressure from socio-economic growth. Understanding the region's water resources management tradeoffs is essential for developing effective adaptation strategies to cope with emerging challenges such as climate change and sea level rise, which are expected to affect many other regions in the future. We describe a network-based hydro-economic optimization model of the system to investigate the tradeoffs, incorporating the economic value of water in urban and agricultural sectors and economic damages due to urban flooding while also accounting for water supply to sustain fragile ecosystems such as the Everglades and coastal estuaries.

The characterization of dynamic susceptibility effects.

Understanding and quantifying dynamic susceptibility contrast, which arises from compartmentalized magnetic field perturbers (e.g., deoxyhemoglobin, contrast agents) that affect the water around them, formed the basis of a significant part of the author's fMRI-related research in the early 90's.

Relative cerebral blood volume maps corrected for contrast agent extravasation significantly correlate with glioma tumor grade, whereas uncorrected maps do not.

Background And Purpose: Relative cerebral blood volume (rCBV) estimates for high-grade gliomas computed with dynamic susceptibility contrast MR imaging are artificially lowered by contrast extravasation through a disrupted blood-brain barrier. We hypothesized that rCBV corrected for agent leakage would correlate significantly with histopathologic tumor grade, whereas uncorrected rCBV would not.

Methods: We performed dynamic T2*-weighted perfusion MR imaging on 43 patients with a cerebral glioma after prebolus gadolinium diethylene triamine penta-acetic acid administration to diminish competing extravasation-induced T1 effects.

Mapping complex tissue architecture with diffusion spectrum magnetic resonance imaging.

Methods are presented to map complex fiber architectures in tissues by imaging the 3D spectra of tissue water diffusion with MR. First, theoretical considerations show why and under what conditions diffusion contrast is positive. Using this result, spin displacement spectra that are conventionally phase-encoded can be accurately reconstructed by a Fourier transform of the measured signal's modulus.

Fibrin-targeted contrast agent for improvement of in vivo acute thrombus detection with magnetic resonance imaging.

Objective: Plaque rupture leading to thrombosis and occlusion is a major source of acute coronary syndromes. Methods for accurate detection of thrombosis in veins or arteries may expand our capacity to predict clinical complications and guide therapeutic decisions. We sought to demonstrate the feasibility of in vivo acute thrombus detection using a fibrin-targeted gadolinium based magnetic resonance contrast agent (EP-1242).

MR angiography of aortoiliac occlusive disease: a phase III study of the safety and effectiveness of the blood-pool contrast agent MS-325.

Purpose: To evaluate prospectively the safety and effectiveness of aortoiliac magnetic resonance (MR) angiography enhanced with MS-325 (gadofosveset trisodium) at a dose of 0.03 mmol/kg; effectiveness was defined as accuracy relative to the reference standard, conventional angiography.

Materials And Methods: Study was approved by institutional review boards of participating institutions, and required national approvals were obtained.

Aortoiliac occlusive disease in patients with known or suspected peripheral vascular disease: safety and efficacy of gadofosveset-enhanced MR angiography--multicenter comparative phase III study.

Purpose: To prospectively determine the safety and efficacy of the gadolinium-based blood pool magnetic resonance (MR) imaging contrast agent gadofosveset in patients known to have or suspected of having peripheral vascular disease.

Materials And Methods: Ethical committee approval and patient written informed consent were obtained. This study was compliant with the Health Insurance Portability and Accountability Act.

Molecular magnetic resonance imaging of coronary thrombosis and pulmonary emboli with a novel fibrin-targeted contrast agent.

Background: The differential diagnosis of acute chest pain is challenging, especially in patients with normal ECG findings, and may include coronary thrombosis or pulmonary emboli. The aim of this study was to investigate the novel fibrin-specific contrast agent EP-2104R for molecular targeted MR imaging of coronary thrombosis and pulmonary emboli.

Methods And Results: Fresh clots were engineered ex vivo from human blood and delivered in the lungs and coronary arteries of 7 swine.

In vivo magnetic resonance imaging of coronary thrombosis using a fibrin-binding molecular magnetic resonance contrast agent.

Background: The advent of fibrin-binding molecular magnetic resonance (MR) contrast agents and advances in coronary MRI techniques offers the potential for direct imaging of coronary thrombosis. We tested the feasibility of this approach using a gadolinium (Gd)-based fibrin-binding contrast agent, EP-2104R (EPIX Medical Inc), in a swine model of coronary thrombus and in-stent thrombosis.

Methods And Results: Ex vivo and in vivo sensitivity of coronary MR thrombus imaging was tested by use of intracoronarily delivered Gd-DTPA-labeled fibrinogen thrombi (n=6).

In vivo molecular imaging of acute and subacute thrombosis using a fibrin-binding magnetic resonance imaging contrast agent.

Background: Plaque rupture with subsequent thrombosis is recognized as the underlying pathophysiology of most acute coronary syndromes and stroke. Thus, direct thrombus visualization may be beneficial for both diagnosis and guidance of therapy. We sought to test the feasibility of direct imaging of acute and subacute thrombosis using MRI together with a novel fibrin-binding gadolinium-labeled peptide, EP-1873, in an experimental animal model of plaque rupture and thrombosis.

MR angiography with gadofosveset trisodium for peripheral vascular disease: phase II trial.

Purpose: To evaluate the dose response and safety of gadofosveset trisodium-enhanced magnetic resonance (MR) angiography compared with nonenhanced two-dimensional time-of-flight MR angiography and with x-ray angiography as the standard.

Materials And Methods: In this randomized, 20-center, double-blind study, 238 men and women who had peripheral vascular disease or were suspected of having it received intravenous injection of placebo or gadofosveset (0.005, 0.

Effects of tracer arrival time on flow estimates in MR perfusion-weighted imaging.

A common technique for calculating cerebral blood flow (CBF) and mean transit time (MTT) is to track a bolus of contrast agent using perfusion-weighted MRI (PWI) and to deconvolve the change in concentration with an arterial input function (AIF) using singular value decomposition (SVD). This method has been shown to often overestimate the volume of tissue that infarcts and in cases of severe vasculopathy to produce CBF maps that are inconsistent with clinical presentation. This study examines the effects of tracer arrival time differences between tissue and a user-selected global AIF on flow estimates.

Serial MR imaging with MS-325 for evaluating female sexual arousal response: determination of intrasubject reproducibility.

Purpose: To determine if a similar sexual arousal response in normal, healthy women could be obtained and monitored by serial magnetic resonance (MR) imaging at two separate sessions.

Materials And Methods: Serial imaging of the external genitalia was performed on nine healthy, sexually functional women at two separate MR sessions after administration of the contrast agent, MS-325. Images were obtained every three minutes during a 45-minute study period during each MR session.

Tracer arrival timing-insensitive technique for estimating flow in MR perfusion-weighted imaging using singular value decomposition with a block-circulant deconvolution matrix.

Relative cerebral blood flow (CBF) and tissue mean transit time (MTT) estimates from bolus-tracking MR perfusion-weighted imaging (PWI) have been shown to be sensitive to delay and dispersion when using singular value decomposition (SVD) with a single measured arterial input function. This study proposes a technique that is made time-shift insensitive by the use of a block-circulant matrix for deconvolution with (oSVD) and without (cSVD) minimization of oscillation of the derived residue function. The performances of these methods are compared with standard SVD (sSVD) in both numerical simulations and in clinically acquired data.

Dynamic MR imaging of the sexual arousal response in women.

The purpose of our studies was to evaluate whether MR imaging could be used to noninvasively observe and measure the sexual arousal response in normal women. We tested the feasibility as well as the reproducibility of rapid, dynamic, serial high-resolution MR imaging of the genital structures during presentation of neutral and sexually stimulating video material. Results show that these MRI techniques can visualize significant changes in clitoral volume during the stimulus segment of the video presentation.

Reduction of eddy-current-induced distortion in diffusion MRI using a twice-refocused spin echo.

Image distortion due to field gradient eddy currents can create image artifacts in diffusion-weighted MR images. These images, acquired by measuring the attenuation of NMR signal due to directionally dependent diffusion, have recently been shown to be useful in the diagnosis and assessment of acute stroke and in mapping of tissue structure. This work presents an improvement on the spin-echo (SE) diffusion sequence that displays less distortion and consequently improves image quality.

Female genitalia: dynamic MR imaging with use of MS-325 initial experiences evaluating female sexual response.

Purpose: To determine whether magnetic resonance (MR) imaging with MS-325, a recently developed blood pool contrast agent, can depict sexual arousal response in healthy women.

Materials And Methods: Serial MR imaging of the external genitalia was performed in 12 healthy sexually functional women before and after administration of MS-325. MR images were obtained every 3 minutes during a 45-minute examination.

Motor cortex activation is related to force of squeezing.

Primate studies have demonstrated that motor cortex neurons show increased activity with increased force of movement. In humans, this relationship has received little study during a power grip such as squeezing, and has previously only been evaluated across a narrow range of forces. Functional MRI was performed in eight healthy subjects who alternated between rest and right hand squeezing at one of three force levels.

Iron-induced susceptibility effect at the globus pallidus causes underestimation of flow and volume on dynamic susceptibility contrast-enhanced MR perfusion images.

Background And Purpose: Age-related iron accumulation in extrapyramidal nuclei causes T2 shortening, which may result in decreased signal intensity in these areas on MR images. Because the dynamic susceptibility contrast-enhanced technique uses heavily T2*- or T2-weighted images, the iron-induced susceptibility may have direct impact on perfusion imaging. The purpose of this study was to assess the effect of iron-induced susceptibility on the calculated perfusion parameters.

Magnetic resonance perfusion-weighted imaging of acute cerebral infarction: effect of the calculation methods and underlying vasculopathy.

Background And Purpose: Various calculation methods are available to estimate the transit-time on MR perfusion-weighted imaging (PWI). Each method may affect the results of PWI. Steno-occlusive disease in the parent vessels is another factor that may affect the results of the PWI.

Locally regularized spatiotemporal modeling and model comparison for functional MRI.

In this work we treat fMRI data analysis as a spatiotemporal system identification problem and address issues of model formulation, estimation, and model comparison. We present a new model that includes a physiologically based hemodynamic response and an empirically derived low-frequency noise model. We introduce an estimation method employing spatial regularization that improves the precision of spatially varying noise estimates.

Magnetic resonance angiography at 0.3 T using MS-325.

Preliminary results on MS-325 versus ProHance enhanced magnetic resonance angiography (MRA) at low field strength in a rabbit model are reported. MS-325-enhanced images were acquired in vivo and compared with pre-contrast as well as conventional contrast-enhanced images. Visual image quality observations correlated with measurements of signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR).

A signal estimation approach to functional MRI.

In the last half decade, fast methods of magnetic resonance imaging have led to the possibility, for the first time, of non-invasive dynamic brain imaging. This has led to an explosion of work in the Neurosciences. From a signal processing viewpoint the problems are those of nonlinear spatio-temporal system identification.

Predicting tissue outcome in acute human cerebral ischemia using combined diffusion- and perfusion-weighted MR imaging.

Background And Purpose: Tissue signatures from acute MR imaging of the brain may be able to categorize physiological status and thereby assist clinical decision making. We designed and analyzed statistical algorithms to evaluate the risk of infarction for each voxel of tissue using acute human functional MRI.

Methods: Diffusion-weighted MR images (DWI) and perfusion-weighted MR images (PWI) from acute stroke patients scanned within 12 hours of symptom onset were retrospectively studied and used to develop thresholding and generalized linear model (GLM) algorithms predicting tissue outcome as determined by follow-up MRI.

Comparison of diameter and perimeter methods for tumor volume calculation.

Purpose: Lesion volume is often used as an end point in clinical trials of oncology therapy. We sought to compare the common method of using orthogonal diameters to estimate lesion volume (the diameter method) with a computer-assisted planimetric technique (the perimeter method).

Methods: Radiologists reviewed 825 magnetic resonance imaging studies from 219 patients with glioblastoma multiforme.