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Purpose MRI of the lung parenchyma is still challenging due to cardiac and respiratory motion, and the low proton density and short T2*. Clinical feasible MRI methods for functional lung assessment are of great interest. It was the objective of this study to evaluate the potential of combining the ultra-short echo-time stack-of-stars approach with tiny golden angle (tyGASoS) profile ordering for self-gated free-breathing lung imaging. Methods Free-breathing tyGASoS data were acquired in 10 healthy volunteers (3 smoker (S), 7 non-smoker (NS)). Images in different respiratory phases were reconstructed applying an image-based self-gating technique. Resulting image quality and sharpness, and parenchyma visibility were qualitatively scored by three blinded independent reader, and the signal-to-noise ratio (SNR), proton fraction (fP) and fractional ventilation (FV) quantified. Result The imaging protocol was well tolerated by all volunteers. Image quality was sufficient for subsequent quantitative analysis in all cases with good to excellent inter-reader reliability. Between expiration (EX) and inspiration (IN) significant differences (p Conclusion The study proves the feasibility of free-breathing tyGASoS for multiphase lung imaging. Changes in fP may indicate an initial response in the smoker group and as such proves the sensitivity of the proposed technique. A major limitation in FV quantification rises from the large inter-subject variability of breathing patterns and amplitudes, requiring further consideration.

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