Real-time measurement of alveolar size and population using phase contrast x-ray imaging

Leong, Andrew; Buckley, Genevieve; Paganin, David M.; Hooper, Stuart B.; Wallace, Megan Jane; Kitchen, Marcus John

doi:10.1364/boe.5.004024

Cited by 22 publications

(36 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…One school of thought is that alveolar size changes throughout respiration based on the pressures and air volumes present 51,52 . The other is that alveolar size remains relatively consistent and that lung volume changes are brought about through the opening and closing of alveoli 53–55 . While there is evidence for both possibilities, no conclusive answer has been determined, and real physiology likely incorporates some degree of both.…”

Section: Discussionmentioning

confidence: 99%

“…This is calculated using

l_{g} = \sqrt[3]{D / ((), γg)}

, where γ is the gyromagnetic ratio and g is the background gradient present before data acquisition. Following common convention, 23,51,54 we assume that the alveolar sac is spherical and find an induced magnetic field ( B ind ) based on susceptibility differences (Δ χ ) between the external and internal environment.

B_{ind} = \frac{2 normalΔ χ B_{0}}{3} .

Then, g = B ind / l s , which for the current situation results in g ≈ 0.88 mT/m for 21% O 2 and g ≈ 0.93 mT/m for 50% O 2 , which subsequently gives l g ≈ 50 μm for all cases (Table 2).…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Preclinical hyperpolarized ¹²⁹Xe MRI: ventilation and T₂* mapping in mouse lungs at 7 T using multi‐echo flyback UTE

et al. 2020

View full text Add to dashboard Cite

Fast apparent transverse relaxation (short T 2 *) is a common obstacle when attempting to perform quantitative 1 H MRI of the lungs. While T 2 * times are longer for pulmonary hyperpolarized (HP) gas functional imaging (in particular for gaseous 129 Xe), T 2 * can still lead to quantitative inaccuracies for sequences requiring longer echo times (such as diffusion weighted images) or longer readout duration (such as spiral sequences). This is especially true in preclinical studies, where high magnetic fields lead to shorter relaxation times than are typically seen in human studies. However, the T 2 * of HP 129 Xe in the most common animal model of human disease (mice) has not been reported. Herein, we present a multi-echo radial flyback imaging sequence and use it to measure HP 129 Xe T 2 * at 7 T under a variety of respiratory conditions. This sequence mitigates the impact of T 1 relaxation outside the animal by using multiple gradient-refocused echoes to acquire images at a number of effective echo times for each RF excitation. After validating the sequence using a phantom containing water doped with superparamagnetic iron oxide nanoparticles, we measured the 129 Xe T 2 * in vivo for 10 healthy C57Bl/6 J mice and found T 2 *~5 ms in the lung airspaces. Interestingly, T 2 * was relatively constant over all experimental conditions, and varied significantly with sex, but not age, mass, or the O 2 content of the inhaled gas mixture. These results are discussed in the context of T 2 * relaxation within porous media. K E Y W O R D S129

show abstract

Section: Discussionmentioning

confidence: 99%

“…This is calculated using

l_{g} = \sqrt[3]{D / ((), γg)}

B_{ind} = \frac{2 normalΔ χ B_{0}}{3} .

Then, g = B ind / l s , which for the current situation results in g ≈ 0.88 mT/m for 21% O 2 and g ≈ 0.93 mT/m for 50% O 2 , which subsequently gives l g ≈ 50 μm for all cases (Table 2).…”

Section: Discussionmentioning

confidence: 99%

Preclinical hyperpolarized ¹²⁹Xe MRI: ventilation and T₂* mapping in mouse lungs at 7 T using multi‐echo flyback UTE

et al. 2020

View full text Add to dashboard Cite

show abstract

“…Airway dimensions and numbers. The speckle pattern produced by PC X-ray imaging of the lung was used to measure regional airway dimensions and the number of aerated distal airways, as previously described (18,21). The airway dimension analysis provides a measure of the dominant airway size in 2D projection using power spectral analysis (21).…”

Section: Image Analysismentioning

confidence: 99%

Elevated airway liquid volumes at birth: a potential cause of transient tachypnea of the newborn

McGillick

Lee

Yamaoka

et al. 2017

Journal of Applied Physiology

Self Cite

View full text Add to dashboard Cite

Excessive liquid in airways and/or distal lung tissue may underpin the respiratory morbidity associated with transient tachypnea of the newborn (TTN). However, its effects on lung aeration and respiratory function following birth are unknown. We investigated the effect of elevated airway liquid volumes on newborn respiratory function. Near-term rabbit kittens (30 days gestation; term ~32 days) were delivered, had their lung liquid-drained, and either had no liquid replaced (control; = 7) or 30 ml/kg of liquid re-added to the airways [liquid added (LA); = 7]. Kittens were mechanically ventilated in a plethysmograph. Measures of chest and lung parameters, uniformity of lung aeration, and airway size were analyzed using phase contrast X-ray imaging. The maximum peak inflation pressure required to recruit a tidal volume of 8 ml/kg was significantly greater in LA compared with control kittens (35.0 ± 0.7 vs. 26.8 ± 0.4 cmHO, < 0.001). LA kittens required greater time to achieve lung aeration (106 ± 14 vs. 60 ± 6 inflations, = 0.03) and had expanded chest walls, as evidenced by an increased total chest area (32 ± 9%, < 0.0001), lung height (17 ± 6%, = 0.02), and curvature of the diaphragm (19 ± 8%, = 0.04). LA kittens had lower functional residual capacity during stepwise changes in positive end-expiratory pressures (5, 3, 0, and 5 cmH0). Elevated lung liquid volumes had marked adverse effects on lung structure and function in the immediate neonatal period and reduced the ability of the lung to aerate efficiently. We speculate that elevated airway liquid volumes may underlie the initial morbidity in near-term babies with TTN after birth. Transient tachypnea of the newborn reduces respiratory function in newborns and is thought to result due to elevated airway liquid volumes following birth. However, the effect of elevated airway liquid volumes on neonatal respiratory function is unknown. Using phase contrast X-ray imaging, we show that elevated airway liquid volumes have adverse effects on lung structure and function in the immediate newborn period, which may underlie the pathology of TTN in near-term babies after birth.

show abstract

“…The surface entrance dose was estimated to 2 mGy for a 100 ms x-ray exposure at 25 keV. This estimation relies on measurements of the air kerma with an ion chamber which was placed 7.2 m from the interaction point (a 1.5 cm thick PMMA block was used as a backscattering object), with these values converted to absorbed dose for water (surface entrance dose), which is comparable to radiation doses used in in vivo small animal synchrotron and micro-CT imaging [52,53,54,55]. were then intratracheally intubated using a non-surgical technique [56,5] with a 20 Ga intravenous catheter used as an endotracheal cannula.…”

Section: In Vivo Imaging Setupmentioning

confidence: 99%

Visualizing treatment delivery and deposition in mouse lungs using in vivo x-ray imaging

Gradl

Dierolf

Yang³

et al. 2019

Journal of Controlled Release

View full text Add to dashboard Cite

The complexity of lung diseases makes pre-clinical in vivo respiratory research in mouse lungs of great importance for a better understanding of physiology and therapeutic effects. Synchrotron-based imaging has been successfully applied to lung research studies, however longitudinal studies can be difficult to perform due to limited facility access. Laboratory-based x-ray sources, such as inverse Compton x-ray sources, remove this access limitation and open up new possibilities for pre-clinical small-animal lung research at high spatial and temporal resolution. The in vivo visualization of drug deposition in mouse lungs is of interest, particularly in longitudinal research, because the therapeutic outcome is not only dependent on the delivered dose of the drug, but also on the spatial distribution of the drug. An additional advantage of this approach, when compared to other imaging techniques, is that anatomic and dynamic information is collected simultaneously. Here we report the use of dynamic x-ray phase-contrast imaging to observe pulmonary drug delivery via liquid instillation, and by inhalation of micro-droplets. Different liquid volumes (4 l  , 20 l  , 50 l ) were tested and a range of localized and global distributions were observed with a temporal resolution of up to 1.5 fps. The in vivo imaging results were confirmed by ex vivo x-ray and fluorescence imaging. This ability to visualize pulmonary substance deposition in live small animals has provided a better understanding of the two key methods of delivery; instillation and nebulization.

show abstract

Real-time measurement of alveolar size and population using phase contrast x-ray imaging

Cited by 22 publications

References 35 publications

Preclinical hyperpolarized ¹²⁹Xe MRI: ventilation and T₂* mapping in mouse lungs at 7 T using multi‐echo flyback UTE

Preclinical hyperpolarized ¹²⁹Xe MRI: ventilation and T₂* mapping in mouse lungs at 7 T using multi‐echo flyback UTE

Elevated airway liquid volumes at birth: a potential cause of transient tachypnea of the newborn

Visualizing treatment delivery and deposition in mouse lungs using in vivo x-ray imaging

Contact Info

Product

Resources

About

Real-time measurement of alveolar size and population using phase contrast x-ray imaging

Cited by 22 publications

References 35 publications

Preclinical hyperpolarized 129Xe MRI: ventilation and T2* mapping in mouse lungs at 7 T using multi‐echo flyback UTE

Preclinical hyperpolarized 129Xe MRI: ventilation and T2* mapping in mouse lungs at 7 T using multi‐echo flyback UTE

Elevated airway liquid volumes at birth: a potential cause of transient tachypnea of the newborn

Visualizing treatment delivery and deposition in mouse lungs using in vivo x-ray imaging

Contact Info

Product

Resources

About

Preclinical hyperpolarized ¹²⁹Xe MRI: ventilation and T₂* mapping in mouse lungs at 7 T using multi‐echo flyback UTE

Preclinical hyperpolarized ¹²⁹Xe MRI: ventilation and T₂* mapping in mouse lungs at 7 T using multi‐echo flyback UTE