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Purpose To measure T1 relaxations for the major tissues in whole knee joints on a clinical 3T scanner. Methods The 3D UTE‐Cones actual flip angle imaging (AFI) method was used to map the transmission radiofrequency field (B1) in both short and long T2 tissues, which was then used to correct the 3D UTE‐Cones variable flip angle (VFA) fitting to generate accurate T1 maps. Numerical simulation was carried out to investigate the accuracy of T1 measurement for a range of T2 values, excitation pulse durations, and B1 errors. Then, the 3D UTE‐Cones AFI‐VFA method was applied to healthy volunteers (N = 16) to quantify the T1 of knee tissues including cartilage, meniscus, quadriceps tendon, patellar tendon, anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), marrow, and muscles at 3T. Results Numerical simulation showed that the 3D UTE‐Cones AFI‐VFA technique can provide accurate T1 measurements (error <1%) when the tissue T2 is longer than 1 ms and a 150 μs excitation RF pulse is used and therefore is suitable for most knee joint tissues. The proposed 3D UTE‐Cones AFI‐VFA method showed an average T1 of 1098 ± 67 ms for cartilage, 833 ± 47 ms for meniscus, 800 ± 66 ms for quadriceps tendon, 656 ± 43 ms for patellar tendon, 873 ± 38 ms for ACL, 832 ± 49 ms for PCL, 379 ± 18 ms for marrow, and 1393 ± 46 ms for muscles. Conclusion The 3D UTE‐Cones AFI‐VFA method allows volumetric T1 measurement of the major tissues in whole knee joints on a clinical 3T scanner.

Background: Since December 2019, the cumulative number of coronavirus disease 2019 (COVID-19) deaths worldwide has reached 1,013,100 and continues to increase as of writing. Of these deaths, more than 90% are people aged 60 and older. Therefore, there is a need for an easy-to-use clinically predictive tool for predicting mortality risk in older individuals with COVID-19. Objective: To explore an easy-to-use clinically predictive tool that may be utilized in predicting mortality risk in older patients with COVID-19. Methods: A retrospective analysis of 118 older patients with COVID-19 admitted to the

Purpose: In ultrashort echo time (UTE) imaging, fat suppression can improve short T 2 * contrast but can also reduce short T 2 * signals. The conventional two-point Dixon (2p-Dixon) method does not perform well due to short T 2 * decay. In this study, we propose a new method to suppress fat for high contrast UTE imaging of short T 2 tissues, utilizing a single-point Dixon (1p-Dixon) method. Methods:The proposed method utilizes dual-echo UTE imaging, where UTE is followed by the second TE, chosen flexibly. Fat is estimated by applying a 1p-Dixon method to the non-UTE image after correction of phase errors, which is used to suppress fat in the UTE image. In vivo ankle and knee imaging were performed at 3 T to evaluate the proposed method.Result: It was observed that fat and water signals in tendons were misestimated by the 2p-Dixon method due to signal decay, while the 1p-Dixon method showed reliable fat and water separation not affected by the short T 2 * signal decay. Compared with the conventional chemical shift based fat saturation technique, the 1p-Dixon based approach showed much stronger signal intensities in the Achilles, quadriceps, and patellar tendons, with significantly improved contrast to noise ratios (CNRs) of 11.8 ± 2.2, 16.0 ± 1.6, and 26.8 ± 1.3 with the 1p-Dixon method and 0.6 ± 0.2, 4.6 ± 1.0, and 17.5 ± 1.4 with regular fat saturation, respectively. Conclusion:The proposed 1p-Dixon based fat suppression allows more flexible selection of imaging parameters and more accurate fat and water separation over the conventional 2p-Dixon in UTE imaging. Moreover, the proposed method provides much improved CNR for short T 2 tissues over the conventional fat saturation method.