Regional fractional ventilation mapping in spontaneously breathing mice using hyperpolarized ¹²⁹Xe MRI

Abstract

The feasibility of ventilation imaging with hyperpolarized (HP) (129) Xe MRI has been investigated for quantitative and regional assessment of ventilation in spontaneously breathing mice. The multiple breath ventilation imaging technique was modified to the protocol of spontaneous inhalation of HP (129) Xe delivered continuously from a (129) Xe polarizer. A series of (129) Xe ventilation images was obtained by varying the number of breaths before the (129) Xe lung imaging. The fractional ventilation, r, was successfully evaluated for spontaneously breathing mice. An attempt was made to detect ventilation dysfunction in the emphysematous mouse lung induced by intratracheal administration of porcine pancreatic elastase (PPE). As a result, the distribution of fractional ventilation could be visualized by the r map. Significant dysfunction of ventilation was quantitatively identified in the PPE-treated group. The whole-lung r value of 0.34 ± 0.01 for control mice (N = 4) was significantly reduced, to 0.25 ± 0.07, in PPE-treated mice (N = 4) (p = 0.038). This study is the first application of multiple breath ventilation imaging to spontaneously breathing mice, and shows that this methodology is sensitive to differences in the pulmonary ventilation. This methodology is expected to improve simplicity as well as noninvasiveness when assessing regional ventilation in small rodents.

Molecular hydrogen and catalytic combustion in the production of hyperpolarized83Kr and129Xe MRI contrast agents

“…Reactive H 2 removal may take place in a small flow-through catalytic converter placed downstream from the SEOP cell that would facilitate gas transport through the generated pressure gradient. Kimura, Imai, Fujiwara, and coworkers used a peristaltic pump for continuous hp 129 Xe recompression after continuous flow SEOP at low pressures (6,10,33), a concept that could be further extended by flow-through catalytic buffer gas removal before recompression. Enabling ondemand production of an uninterrupted, continuous flow of hp 129 Xe at high spin polarization and purity, this concept should be of high value for a variety of applications ranging from material science to biomedical MRI.…”

“…Nevertheless, gas dilution is still required to ensure high spin polarization at the high production volumes required for MRI and the dilution therefore reduces MRI signal intensity per unit volume of inhaled gas. An innovative method developed by Kimura, Imai, Fujiwara, and coworkers (6,10,33) produces a constant stream of 70% concentrated hp 129 Xe but the polarization is typically in the P = 10% regime. In this work, 129 Xe and…”

“…Cryogenic separation complicates the operational procedures for clinical and preclinical hp 129 Xe MRI. For a number of applications a repeat noble gas delivery at high polarization and concentration levels is needed (6,(30)(31)(32)(33)(34)(35). Additionally, a very constant level of spin polarization is required for molecular imaging with hp 129 Xe biosensors using the hyperpolarized xenon chemical exchange saturation transfer (HyperCEST) methodology (17,(36)(37)(38).…”

Treatment response of ethyl pyruvate in a mouse model of chronic obstructive pulmonary disease studied by hyperpolarized129Xe MRI

“…The value of n was sequentially incremented from 1 to 10 and then to 12, 15, and 20; thus, 13 129 Xe ventilation images were acquired in total. (In Imai et al , images were acquired after 1 to 10 breaths only; the purpose of the additional acquired images here was to improve the accuracy of the r a estimate.) From the resulting image series, the fractional ventilation of each voxel was evaluated by analyzing the dependency of the 129 Xe MR signal intensity upon the number of breaths (Eqs.…”

“…From the resulting image series, the fractional ventilation of each voxel was evaluated by analyzing the dependency of the 129 Xe MR signal intensity upon the number of breaths (Eqs. [] and [3], Imai et al ). The fractional ventilation, r a , is defined as (Eq.…”