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Imaging the lung parenchyma with magnetic resonance imaging (MRI) is challenging due to cardiac and respiratory motion, the low proton density and short TIn this study, a 2D UTE technique was combined with tiny golden angle (tyGA) ordering. Data were acquired either during breath-holds (BH) or continuously during free-breathing (FB) at a field strength of 3T. Retrospective self-gating (image- and k-space-based) was used to reconstruct respiratory and cardiac multistage images from the FB acquisitions. The reproducibility of functional lung parameters derived from BH and FB acquisitions was assessed for three independent examinations (M1-3). M1 and M2 were acquired within 2 h, whereas M3 was acquired at least 14 d after M1/2. Different respiratory and cardiac phases were reconstructed for three coronal slices. Quantitative analysis including proton fraction (All scans could be performed successfully in all volunteers. Intraclass correlation coefficients (ICC) of inter-measurement and inter-observer variability, and Bland-Altman analysis showed good to very good reproducibility. Larger breathing amplitudes were observed in the BH acquisitions, which also showed lower reproducibility when compared with the FB acquisitions. For the FB approach, the ICC ranged between 0.70 and 0.98 for all measurements, and ranged between 0.86 and 0.97 for the two observers. No bias or significant differences were observed between the three measurements or the two observers in healthy volunteers.The study proves the feasibility of FB 2D tyGA UTE for lung imaging. Functional parameters derived from FB acquisitions are reproducible in healthy volunteers, allowing for further investigation of this technique in patients with various underlying diseases.

BACKGROUND Imaging of the lung by MRI is challenging due to the intrinsic low proton density and rapid T2 * relaxation. MRI methods providing lung parenchyma and function are in demand. PURPOSE To investigate the feasibility of two-dimensional ultrashort echo-time (2D UTE) imaging for lung function assessment. STUDY TYPE Prospective. POPULATION Eleven healthy volunteers. FIELD STRENGTH/SEQUENCE 3T, 2D tiny golden angle UTE (2D-tyUTE). ASSESSMENT The applicability of breath-hold (BH) and self-gated (SG) 2D-tyUTE for quantification of the lung parenchyma signal-to-noise ratio (SNR), proton fraction (fP ), fractional ventilation (FV), and perfusion (f) was investigated. Dependencies on repetition time (BHS/I1/I2 ) and respiratory phase (expiration [EX], inspiration [IN]) were investigated and compared between smokers and nonsmokers. STATISTICAL TESTS Analysis of variance (ANOVA), Kendell's W. RESULTS Significant differences of SNR (EX: 10.98 ± 3.19(BHS ), 14.58 ± 3.89(BHI1 ), 17.59 ± 4.92(BHI2 ), 11.00 ± 5.42(SG); IN: 7.17 ± 2.07(BHS ), 9.51 ± 2.37(BHI1 ), 10.49 ± 2.33(BHI2 ), 10.00 ± 4.14(SG)) (P

The feasibility of 2D tyGA UTE for the assessment of lung (proton) density, fractional ventilation, quantitative perfusion and qualitative contrast‐enhanced perfusion at 11.7 T was successfully investigated in mice. Lung parenchyma T2* was quantified for correct signal decay compensation during density calculation. Inter‐ and intra‐reader and interstudy reproducibility were assessed, showing the accuracy of the investigated approach. Imaging the lung parenchyma with MRI is particularly difficult in small animals due to the high respiratory and heart rates, and ultrashort T2* at high magnetic field strength caused by the high susceptibilities induced by the air–tissue interfaces. In this study, a 2D ultrashort echo‐time (UTE) technique was combined with tiny golden angle (tyGA) ordering. Data were acquired continuously at 11.7 T and retrospective center‐of‐k‐space gating was applied to reconstruct respiratory multistage images. Lung (proton) density (fP), T2*, signal‐to‐noise ratio (SNR), fractional ventilation (FV) and perfusion (f) were quantified, and the application to dynamic contrast agent (CA)‐enhanced (DCE) qualitative perfusion assessment tested. The interobserver and intraobserver and interstudy reproducibility of the quantitative parameters were investigated. High‐quality images of the lung parenchyma could be acquired in all animals. Over all lung regions a mean T2* of 0.20 ± 0.05 ms was observed. FV resulted as 0.31 ± 0.13, and a trend towards lower SNR values during inspiration (EX: SNR = 12.48 ± 6.68, IN: SNR = 11.79 ± 5.86) and a significant (P < 0.001) decrease in lung density (EX: fP = 0.69 ± 0.13, IN: fP = 0.62 ± 0.13) were observed. Quantitative perfusion results as 34.63 ± 9.05 mL/cm3/min (systole) and 32.77 ± 8.55 mL/cm3/min (diastole) on average. The CA dynamics could be assessed and, because of the continuous nature of the data acquisition, reconstructed at different temporal resolutions. Where a good to excellent interobserver reproducibility and an excellent intraobserver reproducibility resulted, the interstudy reproducibility was only fair to good. In conclusion, the combination of tiny golden angles with UTE (2D tyGA UTE) resulted in a reliable imaging technique for lung morphology and function in mice, providing uniform k‐space coverage and thus low‐artefact images of the lung parenchyma after gating., publishedVersion