Quantification of myocardial blood flow and blood flow reserve in the presence of arterial dispersion: A simulation study
Myocardial blood flow (MBF) can be quantified using dynamic T1-weighted MRI of diffusible tracers and a mathematical model of underlying vasculature. Quantification of MBF by means of T1- weighted MRI requires knowledge of the arterial input function (AIF). The AIF can be estimated from the left ventricular (LV) cavity. However, dispersion may occur between the LV and the tissue of interest because of the laminar blood flow profiles, branching of venules, and because of stenosis. To evaluate the influence of dispersion on the results of MBF quantification, a simulation study was performed. The dispersion was described as a convolution of the AIF with an exponential residue function. Synthet…
3 He-MRI-based vs. conventional determination of lung volumes in patients after unilateral lung transplantation: a new approach to regional spirometry
Background: To use 3Helium (3He)-MRI in patients with unilateral lung grafts to assess the contributions of graft and native lung to total ventilated lung volume, and second to compare conventional measurements of intrapulmonary gas volume (spirometry, body plethysmography) with image-based volumetry of ventilated lung parenchyma visualized by hyperpolarized 3He-MRI. Methods: With Ethics Committee approval, five patients with single lung transplantation (SLTX) for idiopathic pulmonary fibrosis (IPF) underwent both conventional pulmonary function testing (PFT) and 3He-MRI of the lung. Intrapulmonary gas volume (GV) during the inspiratory breathhold for 3He-MRI was calculated from measured fu…
Dynamische Bildgebung der Nasenhaupthöhle und der Nasennebenhöhlen im MR mittels polarisiertem 3Helium
sinuses with polarized 3 helium MRI. Purpose: Reduced or blocked ventilation of the paranasal sinuses is probably the most important factor in the development of sinusitis. Recently, the use of optically polarized noble gas isotopes has attracted increasing interest for use in a variety of promising MR applications. The aim of this study was to test the feasibility of imaging and visualization ventilation of the nasal cavity and paranasal sinus in MR by inhalation of hyperpolarized 3 helium. The goal was to evaluate ventilation defects of the paranasal sinuses. Volunteers and Methods: Three volunteers were enrolled in the study. 3 Helium was polarized to 40-50% by direct optical pumping. 30…
MRI in lung transplant recipients using hyperpolarized 3He: comparison with CT.
PURPOSE To elucidate the ability of 3He-MRI to detect ventilation defects in lung transplant recipients, 3He-MRI was compared to CT for concordance. MATERIALS AND METHODS We examined 14 lung recipients using 3He-MRI on a 1.5 T MR scanner. CT served as a reference method. Up to four representative ventilation defects were defined for each lung on 3He-MRI and compared to corresponding areas on CT. RESULTS Altogether, 59 representative ventilation defects were defined on 3He-MRI. Plausible CT correlates were found for 29 ventilation defects; less plausible CT correlates were found for eight defects. In 22 defects (37%) no corresponding CT changes were detected. CT demonstrated correlates for v…
k-Space filtering in 2D gradient-echo breath-hold hyperpolarized3He MRI: Spatial resolution and signal-to-noise ratio considerations
In this work some of the factors that can influence the signal-to-noise ratio (SNR) and spatial resolution in MR images of inhaled hyperpolarized gases are systematically addressed. In particular, the effects of RF depletion of longitudinal polarization and image gradient diffusion dephasing were assessed in terms of their contribution to a k-space filter. By means of theoretical simulations and a novel method of experimental validation using a variable transverse magnetization of the 1H signal, systematic quantitative and qualitative investigations of the effects of k-space filtering intrinsic to imaging of hyperpolarized gas were made. A 2D gradient-echo image is considered for a range of…