MR-based PET attenuation correction using a combined ultrashort echo time/multi-echo Dixon acquisition.

Purpose: To develop a magnetic resonance (MR)-based method for estimation of continuous linear attenuation coefficients (LACs) in positron emission tomography (PET) using a physical compartmental model and ultrashort echo time (UTE)/multi-echo Dixon (mUTE) acquisitions.

Methods: We propose a three-dimensional (3D) mUTE sequence to acquire signals from water, fat, and short T components (e.g.

Free-Breathing Three-Dimensional T Mapping of the Heart Using Subspace-Based Data Acquisition and Image Reconstruction.

Mapping the longitudinal relaxation time constant (T1) of the myocardium using Magnetic Resonance Imaging (MRI) is an emerging technique for quantitative assessment of the morphology and viability of the myocardium. However, three-dimensional (3D) T1 mapping of the heart is challenging due to the high dimensionality of the signal and the presence of cardiac and respiratory motions. We propose a subspace-based method for free-breathing 3D T1 mapping of the heart without respiratory gating.

Quantification of liver fat in the presence of iron overload.

Purpose: To evaluate the accuracy of R2* models (1/T * = R2*) for chemical shift-encoded magnetic resonance imaging (CSE-MRI)-based proton density fat-fraction (PDFF) quantification in patients with fatty liver and iron overload, using MR spectroscopy (MRS) as the reference standard.

Materials And Methods: Two Monte Carlo simulations were implemented to compare the root-mean-squared-error (RMSE) performance of single-R2* and dual-R2* correction in a theoretical liver environment with high iron. Fatty liver was defined as hepatic PDFF >5.

Quantitative susceptibility mapping in the abdomen as an imaging biomarker of hepatic iron overload.

Purpose: The purpose of this work was to develop and demonstrate feasibility and initial clinical validation of quantitative susceptibility mapping (QSM) in the abdomen as an imaging biomarker of hepatic iron overload.

Theory And Methods: In general, QSM is faced with the challenges of background field removal and dipole inversion. Respiratory motion, the presence of fat, and severe iron overload further complicate QSM in the abdomen.

Improving chemical shift encoded water-fat separation using object-based information of the magnetic field inhomogeneity.

Purpose: The purpose of this work was to improve the robustness of existing chemical shift encoded water-fat separation methods by incorporating object-based information of the B0 field inhomogeneity.

Theory: The primary challenge in water-fat separation is the estimation of phase shifts that arise from B0 field inhomogeneity, which is composed of the background field and susceptibility-induced field. The susceptibility-induced field can be estimated if the susceptibility distribution is known or can be approximated.

Quantitative hepatic perfusion modeling using DCE-MRI with sequential breathholds.

Purpose: To develop and demonstrate the feasibility of a new formulation for quantitative perfusion modeling in the liver using interrupted DCE-MRI data acquired during multiple sequential breathholds.

Materials And Methods: A new mathematical formulation to estimate quantitative perfusion parameters using interrupted data was developed. Using this method, we investigated whether a second degree-of-freedom in the tissue residue function (TRF) improves quality-of-fit criteria when applied to a dual-input single-compartment perfusion model.

High-spatial and high-temporal resolution dynamic contrast-enhanced perfusion imaging of the liver with time-resolved three-dimensional radial MRI.

Purpose: Detection, characterization, and monitoring the treatment of hepatocellular carcinomas (HCC) in patients with cirrhosis is challenging because of their variable and rapid arterial enhancement. Multiphase dynamic contrast-enhanced MRI is used clinically for HCC assessment; however, the method suffers from limited temporal resolution and difficulty in coordinating imaging and breath-hold timing within a narrow temporal window of interest. In this article, a volumetric, high-spatial resolution, and high-temporal resolution dynamic contrast-enhanced liver imaging method for improved detection and characterization of HCC is demonstrated.

Comparison of R2* correction methods for accurate fat quantification in fatty liver.

Purpose: To compare the performance of fat fraction quantification using single-R(2)* and dual-R(2)* correction methods in patients with fatty liver, using MR spectroscopy (MRS) as the reference standard.

Materials And Methods: From a group of 97 patients, 32 patients with hepatic fat fraction greater than 5%, as measured by MRS, were identified. In these patients, chemical shift encoded fat-water imaging was performed, covering the entire liver in a single breathhold.

Validation of MRI biomarkers of hepatic steatosis in the presence of iron overload in the ob/ob mouse.

Purpose: To validate the utility and performance of a T 2 correction method for hepatic fat quantification in an animal model of both steatosis and iron overload.

Materials And Methods: Mice with low (n = 6), medium (n = 6), and high (n = 8) levels of steatosis were sedated and imaged using a chemical shift-based fat-water separation method to obtain magnetic resonance imaging (MRI) fat-fraction measurements. Imaging was performed before and after each of two superparamagnetic iron oxide (SPIO) injections to create hepatic iron overload.

Rapid 3D phenotyping of cardiovascular development in mouse embryos by micro-CT with iodine staining.

Background: Microcomputed tomography (micro-CT) has been used extensively in research to generate high-resolution 3D images of calcified tissues in small animals nondestructively. It has been especially useful for the characterization of skeletal mutations but limited in its utility for the analysis of soft tissue such as the cardiovascular system. Visualization of the cardiovascular system has been largely restricted to structures that can be filled with radiopaque intravascular contrast agents in adult animals.

Micro-computed tomography measurements of peripheral lung pathology in chronic obstructive pulmonary disease.

Background: The smaller airways, < 2 mm in diameter, offer little resistance in normal lungs, but become the major site of obstruction in chronic obstructive pulmonary disease (COPD).

Objective: To examine bronchiolar remodeling and alveolar destruction in COPD using micro-computed tomography (micro-CT).

Methods: Micro-CT was used to measure the number and cross-sectional lumen area of terminal bronchioles (TB) and alveolar mean linear intercept (Lm) in 4 lungs removed from patients with very severe (GOLD-4) COPD and 4 unused donor lungs that served as controls.

Notch signaling in vascular smooth muscle cells is required to pattern the cerebral vasculature.

Stroke is the third leading cause of death and a significant contributor of morbidity in the United States. In humans, suboptimal cerebral collateral circulation within the circle of Willis (CW) predisposes to ischemia and stroke risk in the setting of occlusive carotid artery disease. Unique genes or developmental pathways responsible for proper CW formation are unknown.