Hyperpolarized ¹²⁹Xe gas transfer MRI: the transition from 1.5T to 3T

Abstract

Despite short dissolved-phase T2*, Xe gas transfer MRI is feasible at 3T.

Improved pulmonary 129Xe ventilation imaging via 3D‐spiral UTE MRI

“…Because scan duration is the primary limitation, all scans were acquired with identical undersampling factors: 62.5% partial echo and 62.5% half Fourier factors (39% of k‐space acquired) for 2D‐GRE; 39% of Nyquist radial spokes (equally spaced spokes, maximum undersampling factor, R max = 2.56) for 3D‐radial; and R max value of 2.56 (intertrajectory spacing linearly increasing with k‐space radius up to 2.56 times the Nyquist distance) for FLORET. The FLORET sequence was implemented with a readout duration of approximately 8 ms, similar to the global (spectroscopy‐based lower limit) of xenon gas in the lung at 3 T and with 2 hubs with a maximum cone angle of 45º. The voxel volumes were smaller for FLORET (27 mm 3 ) compared with 3D radial and 2D GRE (86 mm 3 and 79 mm 3 , respectively).…”

In vivo methods and applications of xenon-129 magnetic resonance

“…Therefore, dissolved-phase 129 Xe signal is usually acquired as a free induction decay or echo with very short echo time. In light of the benefit of longer T 2 *( 129 Xe) values [103] , considerable development work for dissolved 129 Xe MRI/MRS in humans has been performed at a field strength of 1.5 T (T 2 *( 129 Xe) ~2.2 ms [104] ), and this has recently been shown to be translatable to 3 T (T 2 *( 129 Xe) ~1.1 ms) [105] . In addition, upon diffusing into the lung parenchyma, 129 Xe rapidly exchanges between the parenchyma and pulmonary capillaries (typical time constant for airspace to capillary transfer <100 ms [106] , [107] ), and within the capillaries, 129 Xe exchanges between plasma and RBCs on a timescale of 12 ms [108] .…”

Dissolved 129Xe lung MRI with four‐echo 3D radial spectroscopic imaging: Quantification of regional gas transfer in idiopathic pulmonary fibrosis

“…The study was also performed at 1.5T, and it might be expected that a lower SNR (due to approximately twice shorter dissolved 129 Xe T * of only ~2 ms for the first three TEs (the fourth TE mainly helps model the gas signal during the reconstruction), the method should be translatable to 3T, similar to what was shown recently for the one-point Dixon method. 35 Alternatively, using twice as many dissolved phase interleaves and acquiring only two of the four-echos per interleave (first and third echoes for first interleave and second and fourth for the second interleave) could be implemented using a shorter optimum ΔTE of 0.35 ms at 3T and keep the same number of radial projection and image resolution by shortening the flip angle and TR.…”