Single‐breath xenon polarization transfer contrast (SB‐XTC): Implementation and initial results in healthy humans

Abstract

Purpose To implement and characterize a single-breath xenon transfer contrast (SB-XTC) method to assess the fractional diffusive gas transport F in the lung: to study the dependence of F and its uniformity as a function of lung volume; to estimate local alveolar surface area per unit gas volume SA/VGas from multiple diffusion time measurements of F; to evaluate the reproducibility of the measurements and the necessity of B1 correction in cases of centric and sequential encoding. Materials and Methods In SB-XTC three or four gradient echo images separated by inversion/saturation pulses were collected during a breath-hold in eight healthy volunteers, allowing the mapping of F (thus SA/VGas) and correction for other contributions such as T1 relaxation, RF depletion and B1 inhomogeneity from inherently registered data. Results Regional values of F and its distribution were obtained; both the mean value and heterogeneity of F increased with the decrease of lung volume. Higher values of F in the bases of the lungs in supine position were observed at lower volumes in all volunteers. Local SA/VGas (with a mean ± standard deviation of SA/VGas¯=89±30cm-1) was estimated in vivo near functional residual capacity. Calibration of SB-XTC on phantoms highlighted the necessity for B1 corrections when k-space is traversed sequentially; with centric ordering B1 distribution correction is dispensable. Conclusion SB-XTC technique is implemented and validated for in vivo measurements of local SA/VGas.

Mapping of regional lung microstructural parameters using hyperpolarized 129Xe dissolved‐phase MRI in healthy volunteers and patients with chronic obstructive pulmonary disease

“…The latter technique is known as chemical shift saturation recovery (CSSR) spectroscopy and has been shown to be sensitive for structural changes of the lung on a subclinical level . However, because standard implementations of CSSR do not feature any spatial encoding, regional information is usually lacking and there have been efforts to resolve this issue . Certain lung microstructural parameters can also be obtained using gas diffusion MRI and models of acinar microstructure .…”

“…16,17 However, because standard implementations of CSSR do not feature any spatial encoding, regional information is usually lacking and there have been efforts to resolve this issue. 16,[18][19][20][21][22][23][24][25] Certain lung microstructural parameters can also be obtained using gas diffusion MRI and models of acinar microstructure. 26,27 Although there is significant evidence for the validity of these models from comparison to histology, 28 there are some limitations that might affect their accuracy.…”

Experimental validation of the hyperpolarized 129Xe chemical shift saturation recovery technique in healthy volunteers and subjects with interstitial lung disease

“…Direct imaging techniques have been used, wherein the gaseous and dissolved 129 Xe resonances from the lungs are imaged simultaneously to provide information about pulmonary ventilation and perfusion. The xenon polarization transfer contrast (XTC) method , uses the weak signal from dissolved 129 Xe to modulate the higher SNR gaseous 129 Xe images by means of diffusional exchange. The chemical shift saturation recovery (CSSR) spectroscopy method involves monitoring the time‐dependent build‐up of dissolved 129 Xe magnetization in the T/P and RBC compartments following selective saturation.…”

Translational applications of hyperpolarized 3He and 129Xe

“…This opens the door to separate image‐maps of red blood cells and tissue/plasma such as those shown in Fig. , taken from Reference , with the potential for exploration of multiple gas‐exchange biomarkers, including septal wall thickness, alveolar surface area per unit gas volume, capillary transit time, and hematocrit . Indeed, Patz et al .…”