An empirical method for reducing variability and complexity of myocardial perfusion quantification by dual bolus cardiac MRI.

Purpose: Myocardial perfusion can be quantified using the "dual bolus" technique, which uses two separate contrast boluses to avoid signal nonlinearity in the blood pool. This technique relies on knowing the precise ratio of contrast concentrations between the two boluses. In this study, we investigated the variability found in these ratios, as well as the error it introduces, and developed a method for correction.

A Comparison of Theory-Based and Experimentally Determined Myocardial Signal Intensity Correction Methods in First-Pass Perfusion Magnetic Resonance Imaging.

Objectives: To evaluate the impact of correcting myocardial signal saturation on the accuracy of absolute myocardial blood flow (MBF) measurements.

Materials And Methods: We performed 15 dual bolus first-pass perfusion studies in 7 dogs during global coronary vasodilation and variable degrees of coronary artery stenosis. We compared microsphere MBF to MBF calculated from uncorrected and corrected MRI signal.

Using dynamic contrast-enhanced magnetic resonance imaging data to constrain a positron emission tomography kinetic model: theory and simulations.

We show how dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) data can constrain a compartmental model for analyzing dynamic positron emission tomography (PET) data. We first develop the theory that enables the use of DCE-MRI data to separate whole tissue time activity curves (TACs) available from dynamic PET data into individual TACs associated with the blood space, the extravascular-extracellular space (EES), and the extravascular-intracellular space (EIS). Then we simulate whole tissue TACs over a range of physiologically relevant kinetic parameter values and show that using appropriate DCE-MRI data can separate the PET TAC into the three components with accuracy that is noise dependent.

A diffusion-compensated model for the analysis of DCE-MRI data: theory, simulations and experimental results.

Accurate quantification of pharmacokinetic parameters in dynamic contrast-enhanced (DCE) MRI may be affected by the passive diffusion of contrast agent (CA) within the tissue. By introducing an additional term into the standard Tofts-Kety (STK) model, we correct for the effects of CA diffusion. We first develop the theory describing a CA diffusion corrected STK model (DTK).

Absolute quantification of myocardial blood flow with constrained estimation of the arterial input function.

Purpose: To evaluate the performance of the constrained alternating minimization with model (CAMM) method for estimating the input function from the myocardial tissue curves.

Materials And Methods: Myocardial perfusion imaging was performed on seven canine models of coronary artery disease in 15 imaging sessions. In each session, stress was induced with intravenous infusion of adenosine and a variable occluder created coronary artery stenosis.

Left atrial flow velocity distribution and flow coherence using four-dimensional FLOW MRI: a pilot study investigating the impact of age and Pre- and Postintervention atrial fibrillation on atrial hemodynamics.

Purpose: To use four-dimensional (4D) flow MRI to characterize and quantify 3D blood flow in the left atria (LA) of patients with a history of atrial fibrillation (AF).

Materials And Methods: The 4D flow MRI was acquired in 19 volunteers (n = 9<30 years, n = 10>50 years) and 10 patients with AF (62 ± 9.6 years; n = 4 in persistent AF, n = 6 postintervention).

Reproducibility of static and dynamic (18)F-FDG, (18)F-FLT, and (18)F-FMISO MicroPET studies in a murine model of HER2+ breast cancer.

Purpose: The objective of this study is to determine the reproducibility of static 2-deoxy-2-[(18)F]fluoro-D-glucose ((18)F-FDG), 3'-deoxy-3'-[(18)F]fluorothymidine ((18)F-FLT), and [(18)F]-fluoromisonidazole ((18)F-FMISO) microPET measurements, as well as kinetic parameters returned from analyses of dynamic (18)F-FLT and (18)F-FMISO data.

Procedures: HER2+ xenografts were established in nude mice. Dynamic data were acquired for 60 min, followed by a repeat injection and second scan 6 h later.

The effect of temporal sampling on quantitative pharmacokinetic and three-time-point analysis of breast DCE-MRI.

The effects of temporal sampling on the previously published three-time-point (3TP) method are compared with those of a Tofts-Kety model using an arterial input function from the alternating minimization with model (AMM) method. Computer simulations are done to estimate the expected error in both the 3TP and Tofts-Kety models as a function of the temporal sampling rate of the data. The error in the 3TP model parameters remained essentially constant with respect to temporal sampling.

The effect of obesity on regadenoson-induced myocardial hyperemia: a quantitative magnetic resonance imaging study.

The A2(A) receptor agonist, regadenoson, is increasingly used as a vasodilator during nuclear myocardial perfusion imaging. Regadenoson is administered as a single, fixed dose. Given the frequency of obesity in patients with symptoms of heart disease, it is important to know whether the fixed dose of regadenoson produces maximal coronary hyperemia in subjects of widely varying body size.

Constrained estimation of the arterial input function for myocardial perfusion cardiovascular magnetic resonance.

Accurate quantification of myocardial perfusion remains challenging due to saturation of the arterial input function at high contrast concentrations. A method for estimating the arterial input function directly from tissue curves in the myocardium that avoids these difficulties is presented. In this constrained alternating minimization with model (CAMM) algorithm, a portion of the left ventricular blood pool signal is also used to constrain the estimation process.

Toward local arterial input functions in dynamic contrast-enhanced MRI.

Purpose: To present a method for estimating the local arterial input function (AIF) within a dynamic contrast-enhanced MRI scan, based on the alternating minimization with model (AMM) method.

Materials And Methods: This method clusters a subset of data into representative curves, which are then input to the AMM algorithm to return a parameterized AIF and pharmacokinetic parameters. Computer simulations are used to investigate the accuracy with which the AMM is able to estimate the true AIF as a function of the input tissue curves.

A model-constrained Monte Carlo method for blind arterial input function estimation in dynamic contrast-enhanced MRI: I. Simulations.

Widespread adoption of quantitative pharmacokinetic modeling methods in conjunction with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) has led to increased recognition of the importance of obtaining accurate patient-specific arterial input function (AIF) measurements. Ideally, DCE-MRI studies use an AIF directly measured in an artery local to the tissue of interest, along with measured tissue concentration curves, to quantitatively determine pharmacokinetic parameters. However, the numerous technical and practical difficulties associated with AIF measurement have made the use of population-averaged AIF data a popular, if sub-optimal, alternative to AIF measurement.

Model-based blind estimation of kinetic parameters in dynamic contrast enhanced (DCE)-MRI.

A method to simultaneously estimate the arterial input function (AIF) and pharmacokinetic model parameters from dynamic contrast-enhanced (DCE)-MRI data was developed. This algorithm uses a parameterized functional form to model the AIF and k-means clustering to classify tissue time-concentration measurements into a set of characteristic curves. An iterative blind estimation algorithm alternately estimated parameters for the input function and the pharmacokinetic model.