Impact of undersampling on preclinical lung T2 mapping with 3D radial UTE MRI at 7 T

• Published in: Journal of magnetic resonance (1997) 2024-08, Vol.365, p.107741, Article 107741
• Main Authors: Stecker, Ian R., Bdaiwi, Abdullah S., Niedbalski, Peter J., Chatterjee, Neelakshi, Hossain, Md M., Cleveland, Zackary I.
• Format: Article
• Language: English
• Subjects: 3D Radial UTE MRI; Lung T2 mapping; Preclinical; Undersampling k-space
• ISSN: 1090-7807; 1096-0856; 1096-0856
• DOI: 10.1016/j.jmr.2024.107741

[Display omitted] •Average parenchymal SNR only slightly decreased by 1.4 even at 90% undersampling.•Parenchymal T2* significantly increased (p > 0.05) at less than 80 % sampling compared to full sampling.•Increased scatter in both SNR and T2* metrics noticeable at around 50% undersampling.•Study provides valuable insights into the acceptable degree of undersampling for preclinical lung images with 3D UTE. Lung diseases are almost invariably heterogeneous and progressive, making it imperative to capture temporally and spatially explicit information to understand the disease initiation and progression. Imaging the lung with MRI—particularly in the preclinical setting—has historically been challenging because of relatively low lung tissue density, rapid cardiac and respiratory motion, and rapid transverse (T2*) relaxation. These limitations can largely be mitigated using ultrashort-echo-time (UTE) sequences, which are intrinsically robust to motion and avoid significant T2* decay. A significant disadvantage of common radial UTE sequences is that they require inefficient, center-out k-space sampling, resulting in long acquisition times relative to conventional Cartesian sequences. Therefore, pulmonary images acquired with radial UTE are often undersampled to reduce acquisition time. However, undersampling reduces image SNR, introduces image artifacts, and degrades true image resolution. The level of undersampling is further increased if offline gating techniques like retrospective gating are employed, because only a portion (∼40–50%) of the data is used in the final image reconstruction. Here, we explore the impact of undersampling on SNR and T2* mapping in mouse lung imaging using simulation and in-vivo data. Increased scatter in both metrics was noticeable at around 50% sampling. Parenchymal apparent SNR only decreased slightly (average decrease ∼ 1.4) with as little as 10% sampling. Apparent T2* remained similar across undersampling levels, but it became significantly increased (p