¹⁹F MR imaging of ventilation and diffusion in excised lungs

Abstract

Perfluorinated gases, particularly C 2 F 6 , are potentially suitable alternatives to hyperpolarized noble gases for pulmonary airspace spin density and diffusion MRI. This work focuses mainly on 19 F imaging of C 2 F 6 gas in healthy and emphysematous explanted lungs, avoiding regulatory issues of human in vivo measurements. Three-dimensional gradient echo and spin echo spin density images of human lungs can be made in 10 s with adequate signal-to-noise, demonstrating the feasibility for breathing dynamics to be captured during a succession of short breath holds. As expected, the spin echo images have much smaller susceptibility artifacts than the gradient echo images.

3D 3He diffusion MRI as a local in vivo morphometric tool to evaluate emphysematous rat lungs

“…First, the in situ shape of the lung was not well preserved, so the shapes of the lung sections did not well match those of the 3 He images. Lungs that have been removed from the chest can change significantly from the in situ shape defined by the thoracic cavity (14,30). Second, the lungs were not rigid during sectioning.…”

“…Because early detection of COPD can play a significant role in managing the disease and improving patient outcomes (2,20), a locally specific and sensitive method of detection may prove beneficial. Hyperpolarized (HP) 3 He and 129 Xe gas have been exploited in clinical and preclinical magnetic resonance imaging (MRI) studies to evaluate lung tissue structure (5,6,8,18,22,33), although perfluorinated gases have also been used (14). In several studies, 3 He MRI has been demonstrated to be sensitive to mild or early emphysema (10,28,34,38).…”

Relaxation and diffusion of perfluorocarbon gas mixtures with oxygen for lung MRI

“…Our group has recently shown that diffusion of C 2 F 6 and C 3 F 8 gases is substantially restricted in excised normal human donor lungs such that the measured diffusivity is approximately 50% of the free diffusivity D 0 [22][23][24]. In excised severely emphysematous lungs, the 19 F diffusion is less restricted (approximately 90% of D 0 ), demonstrating that perfluorocarbon (PFC) gas imaging can readily distinguish healthy and emphysematous lung regions.…”

Hyperpolarized 83Kr MRI of lungs

“…However, neither hp 3 He, hp 129 Xe, nor alternative techniques using thermally polarized fluorinated gas species [19,20] can deliver information about lung surface chemistry, which is intimately linked to certain lung diseases. For instance, acute lung injury (ALI), including its most severe form acute respiratory distress syndrome (ARDS) [21], is characterized by changes in the lipid and protein composition of the pulmonary surfactant system.…”

“…The sensitivity hp 83 Kr displays to surface-to-volume ratio within porous materials may also be of diagnostic value. Increased alveolar size due to both natural aging [10] and chronic obstructive pulmonary disease (COPD) progression [20] has been observed using hp 3 He apparent diffusion coefficient (ADC) measurements, while other disorders, such as ALI, are associated with alveolar collapse and thus increased surface-to-volume ratios.…”