Inhaled hyperpolarized helium-3 (/sup 3/He) gas is a new magnetic resonance (MR) contrast agent that is being used to study lung functionality. To evaluate the total lung ventilation from the ...hyperpolarized /sup 3/He MR images, it is necessary to segment the lung cavities. This is difficult to accomplish using only the hyperpolarized /sup 3/He MR images, so traditional proton (/sup 1/H) MR images are frequently obtained concurrent with the hyperpolarized /sup 3/He MR examination. Segmentation of the lung cavities from traditional proton (/sup 1/H) MRI is a necessary first step in the analysis of hyperpolarized /sup 3/He MR images. In this paper, we develop an active contour model that provides a smooth boundary and accurately captures the high curvature features of the lung cavities from the /sup 1/H MR images. This segmentation method is the first parametric active contour model that facilitates straightforward merging of multiple contours. The proposed method of merging computes an external force field that is based on the solution of partial differential equations with boundary condition defined by the initial positions of the evolving contours. A theoretical connection with fluid flow in porous media and the proposed force field is established. Then by using the properties of fluid flow we prove that the proposed method indeed achieves merging and the contours stop at the object boundary as well. Experimental results involving merging in synthetic images are provided. The segmentation technique has been employed in lung /sup 1/H MR imaging for segmenting the total lung air space. This technology plays a key role in computing the functional air space from MR images that use hyperpolarized /sup 3/He gas as a contrast agent.
To quantitatively evaluate hyperpolarized helium 3 ((3)He) diffusion magnetic resonance (MR) images of the lung in patients with emphysema and to determine whether apparent diffusion coefficients ...(ADCs) measured with MR imaging correlate with spirometric indexes.
Hyperpolarized (3)He diffusion MR imaging was performed in 16 healthy volunteers and 11 patients. Coronal diffusion-sensitized MR images were obtained during suspended respiration after inhalation of laser-polarized (3)He gas, and images of the ADC were calculated. Spirometry was performed immediately before imaging. The mean and SD of the ADCs were compared between subject groups and were correlated with spirometric indexes.
ADC images were homogeneous in volunteers, but demonstrated regional variations in patients. The mean and SD of the ADCs for patients were significantly larger (P <.002) than those for volunteers. The mean ADCs for all subjects correlated with the percentage of predicted forced expiratory volume in 1 second, or FEV(1), (r = -0.797, P <.001) and the ratio of FEV(1) to forced vital capacity, or FVC, (r = -0.930, P <.001). ADC images in patients demonstrated a significant increase (P <.001) in the ADCs in the upper regions compared with the lower regions of the lung.
Hyperpolarized (3)He diffusion MR imaging demonstrated potential for use in evaluating the global and regional severity of emphysema.
The purpose of this study is to determine hyperpolarized helium 3 (HHe) magnetic resonance (MR) findings of the lung in patients with cystic fibrosis (CF) compared with healthy subjects and determine ...whether HHe MR can detect changes after bronchodilator therapy or mechanical airway mucus clearance treatment.
Thirty-one subjects, 16 healthy volunteers and 15 patients with CF, underwent HHe lung ventilation MR imaging and spirometry at baseline. Eight patients with CF then were treated with nebulized albuterol, after which a follow-up HHe MR scan was obtained. Subsequently, recombinant human deoxyribonuclease (DNase) treatment and chest physical therapy were performed in these eight subjects, followed by a third HHe MR scan. For each MR study, the number of ventilation defects was scored by a human reader.
Patients with CF had significantly more HHe MR ventilation defects per image than healthy subjects (mean, 8.2 defects in patients with CF vs 1.6 defects in healthy subjects; P < .05). Even the four subjects with CF with a normal forced expiratory volume in 1 second had significantly more ventilation defects than healthy subjects (mean, 6.5 defects in these patients with CF; P = .0002). After treatment with albuterol, there was a small, but statistically significant, decrease in number of ventilation defects (mean, 9.6-8.0 defects; P = .025). After DNase and chest physical therapy, there was a trend toward increasing ventilation defects (mean, 8.3 defects; P = .096), but with a residual net improvement relative to baseline.
In patients with CF, HHe MR ventilation defects correlate with spirometry, change with treatment, and are elevated in number in patients with CF with normal spirometry results. Thus, HHe MR appears to possess many of the characteristics required of a biomarker for pulmonary CF and may be useful in the evaluation of CF pulmonary disease severity or progression.
To develop a rabbit model of an intracranial bifurcation aneurysm to test new endovascular therapies.
An experimental aneurysm model was created in rabbits by means of endovascular balloon occlusion ...of the left common carotid artery, which created an aneurysm at the bifurcation formed by the aortic arch and the brachiocephalic trunk. A total of 18 aneurysms were created. In eight rabbits, the aneurysms were incubated with intraluminal elastase to induce degeneration of the elastic laminae. The animals were followed up with angiography for as long as 3 months. The animals were sacrificed at various times, and histologic evaluation of the aneurysm was performed.
Ten aneurysms created without elastase infusion were all very small or completely closed at 1-3 months. Six aneurysms created with elastase infusion had long-term patency (two were patent at 1 month and four, at 3 months). The elastase aneurysms had a mean width of 3 mm (range, 2-3.5 mm) and a mean length of 5 mm (range, 3-7 mm). Histologic evaluation revealed destruction of the normal elastin layers, which allowed the artery to become aneurysmal.
This aneurysm model re-created the hemodynamic forces and size of human cerebral bifurcation aneurysms and maintained the integrity of the endothelium. The creation of the aneurysms was rapid, reliable, and reproducible.
To characterize the histologic response to platinum coil embolization by using a rabbit aneurysm model.
Saccular aneurysms were created in New Zealand White rabbits by using vessel ligation with ...intraluminal elastase incubation. Aneurysms were subsequently embolized by using platinum coils. Subjects were sacrificed at various intervals up to 12 weeks following coil embolization. The aneurysm cavities and adjacent vessels were embedded in methylmethacrylate, were sectioned, and were stained for histologic examination.
Two weeks following coil implantation, aneurysms were filled predominantly with unorganized thrombus. Six weeks following coil implantation, histologic features included complete filling of the aneurysm lumen with either prominent laminated but unorganized thrombus or areas of unorganized thrombus interspersed among areas of cellular infiltration. At 12 weeks following coil implantation, aneurysms were filled with the loosely packed, disordered cells contained within the extracellular matrix. Fibrosis or smooth muscle cell infiltration was not present in any of the 6- or 12-week samples.
Platinum coils placed into experimental saccular aneurysms in New Zealand White rabbits failed to elicit a fibrotic response. This model can be used for the testing of biologic modifications of platinum coils aimed at increasing intra-aneurysmal fibrosis.
Hyperpolarized (HP) gases are a new class of contrast agents that permit to obtain high temporal and spatial resolution magnetic resonance images (MRI) of the lung airspaces. HP gas MRI has become ...important research tool not only for morphological and functional evaluation of normal pulmonary physiology but also for regional quantification of pathologic changes occurring in several lung diseases. The purpose of this work is to provide an introduction to MRI using HP noble gases, describing both the basic principles of the technique and the new information about lung disease provided by clinical studies with this method. The applications of the technique in normal subjects, smoking related lung disease, asthma, and cystic fibrosis are reviewed.
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