Highly constrained backprojection for improving dynamic 3He MR ventilation imaging in rats.

The highly constrained backprojection algorithm (HYPR) has recently been shown to allow accelerated acquisition in various fields of MRI, including angiography, perfusion and diffusion imaging as well as hyperpolarized gas imaging. Increase in temporal resolution is of particular interest in the case of small animal ventilation imaging due to the high respiration rate. In the present study, the two-dimensional HYPR technique and its iterative version (I-HYPR) were applied to (3)He ventilation imaging in rats.

Validation of simple and robust protocols for high-resolution lung proton MRI in mice.

One fundamental limitation of spatial resolution for in vivo MR lung imaging is related to motion in the thoracic cavity. To overcome this limitation, several methods have been proposed, including scan-synchronous ventilation and the cardiac gating approach. However, with cardiac and ventilation triggered techniques, the use of a predetermined and constant sequence repetition time is not possible, resulting in variable image contrast.

Long-term follow-up of lung biodistribution and effect of instilled SWCNTs using multiscale imaging techniques.

Due to their distinctive properties, single-walled carbon nanotubes (SWCNTs) are being more and more extensively used in nanotechnology, with prospects in nanomedicine. It would therefore appear essential to develop and apply appropriate imaging tools for detecting and evaluating their biological impacts with the prospect of medical applications or in the situation of accidental occupational exposure. It has been shown recently that raw SWCNTs with metallic impurities can be noninvasively detected in the lungs by hyperpolarized (3)helium (HP-(3)He) MRI.

Hyperpolarized 3He MR for sensitive imaging of ventilation function and treatment efficiency in young cystic fibrosis patients with normal lung function.

Purpose: To assess the sensitivity of hyperpolarized helium 3 ((3)He) magnetic resonance (MR) imaging for the detection of peripheral airway obstruction in younger cystic fibrosis (CF) patients showing normal spirometric results (mean forced expiratory volume in 1 second [FEV(1)], 112% +/- 14.5 [standard deviation]) and to observe the immediate effects of a single chest physical therapy (CPT) session, thereby comparing two image quantification techniques.

Materials And Methods: Ten pediatric CF patients (age range, 8-16 years) with normal spirometric results were included in this study after approval from the local research ethics committee.

Free breathing hyperpolarized 3He lung ventilation spiral MR imaging.

Objectives: Current clinical hyperpolarized He lung ventilation MR imaging protocols rely on the patient's ability to control inhalation and exhalation and hold their breath on demand. This is impractical for intensive care unit patients under ventilation or for pediatric populations under the age of 3 to 4 years. To address this problem, we propose a free-breathing protocol for hyperpolarized He lung ventilation spiral imaging.

In vivo imaging of carbon nanotube biodistribution using magnetic resonance imaging.

As novel engineered nanoparticles such as carbon nanotubes (CNTs) are extensively used in nanotechnology due to their superior properties, it becomes critical to fully understand their biodistribution and effect when accidently inhaled. A noninvasive follow-up study would be beneficial to evaluate the biodistribution and effect of nanotube deposition after exposure directly in vivo. Combined helium-3 and proton magnetic resonance resonance (MRI) were used in a rat model to evaluate the biodistribution and biological impact of raw single-wall CNTs (raw-SWCNTs) and superpurified SWCNTs (SP-SWCNTs).

Measurement of nonlinear pO2 decay in mouse lungs using 3He-MRI.

Spatial and temporal variations in oxygen partial pressure (pO(2)) during breath-hold can be exploited to obtain important regional parameters of lung function. In the course of apnea, the oxygen concentration is known to decay exponentially. Therefore, the initial pO(2) (p(0)) can be used to represent local ventilation, and the oxygen depletion time constant can characterize perfusion.

Alveolar oxygen partial pressure and oxygen depletion rate mapping in rats using 3He ventilation imaging.

A hyperpolarized 3He ventilation imaging protocol was implemented to assess alveolar pO2 values and the oxygen depletion rate in rats. The imaging protocol, which is based on spiral k-space sampling, was designed to acquire a high signal-to-noise ratio (SNR) T1-weighted ventilation series of images in a single breath-hold. Simulations were performed to estimate the accuracy and dependence of the pO2 imaging protocol on the image SNR and the RF flip-angle determination.