Browsing by Author "Emir, Uzay E."

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    Fast in vivo 23 Na imaging and T2∗ mapping using accelerated 2D-FID UTE magnetic resonance spectroscopic imaging at 3 T: Proof of concept and reliability study
    (Wiley, 2021) Alhulail, Ahmad A.; Xia, Pingyu; Shen, Xin; Nichols, Miranda; Volety, Srijyotsna; Farley, Nicholas; Thomas, Michael Albert; Nagel, Armin M.; Dydak, Ulrike; Emir, Uzay E.; Radiology and Imaging Sciences, School of Medicine
    Purpose: To implement an accelerated MR-acquisition method allowing to map T2* relaxation and absolute concentration of sodium within skeletal muscles at 3T. Methods: A fast-UTE-2D density-weighted concentric-ring-trajectory 23 Na-MRSI technique was used to acquire 64 time points of FID with a spectral bandwidth of 312.5 Hz with an in-plane resolution of 2.5 × 2.5 mm2 in ~15 min. The fast-relaxing 23 Na signal was localized with a single-shot, inversion-recovery-based, non-echo (SIRENE) outer volume suppression (OVS) method. The sequence was verified using simulation and phantom studies before implementing it in human calf muscles. To evaluate the 2D-SIRENE-MRSI (UTE = 0.55 ms) imaging performance, it was compared to a 3D-MRI (UTE = 0.3 ms) sequence. Both data sets were acquired within 2 same-day sessions to assess repeatability. The T2* values were fitted voxel-by-voxel using a biexponential model for the 2D-MRSI data. Finally, intra-subject coefficients of variation (CV) were estimated. Results: The MRSI-FID data allowed us to map the fast and slow components of T2* in the calf muscles. The spatial distributions of 23 Na concentration for both MRSI and 3D-MRI acquisitions were significantly correlated (P < .001). The test-retest analysis rendered high repeatability for MRSI with a CV of 5%. The mean T2* Fast in muscles was 0.7 ± 0.1 ms (contribution fraction = 37%), whereas T2* Slow was 13.2 ± 0.2 ms (63%). The mean absolute muscle 23 Na concentration calculated from the T2* -corrected data was 28.6 ± 3.3 mM. Conclusion: The proposed MRSI technique is a reliable technique to map sodium's absolute concentration and T2* within a clinically acceptable scan time at 3T.
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    Fat-water separation by fast metabolite cycling magnetic resonance spectroscopic imaging at 3 T: A method to generate separate quantitative distribution maps of musculoskeletal lipid components
    (Wiley, 2020-09) Alhulail, Ahmad A.; Patterson, Debra A.; Xia, Pingyu; Zhou, Xiaopeng; Lin, Chen; Thomas, M. Albert; Dydak, Ulrike; Emir, Uzay E.; Radiology and Imaging Sciences, School of Medicine
    Purpose: To provide a rapid, noninvasive fat-water separation technique that allows producing quantitative maps of particular lipid components. Methods: The calf muscles in 5 healthy adolescents (age 12-16 years; body mass index = 20 ± 3 kg/m2 ) were scanned by two different fat fraction measurement methods. A density-weighted concentric-ring trajectory metabolite-cycling MRSI technique was implemented to collect data with a nominal resolution of 0.25 mL within 3 minutes and 16 seconds. For comparative purposes, the standard Dixon technique was performed. The two techniques were compared using structural similarity analysis. Additionally, the difference in the distribution of each lipid over the adolescent calf muscles was assessed based on the MRSI data. Results: The proposed MRSI technique provided individual fat fraction maps for eight musculoskeletal lipid components identified by LCModel analysis (IMC/L [CH3 ], EMCL [CH3 ], IMC/L [CH2 ]n , EMC/L [CH2 ]n , IMC/L [CH2 -CH], EMC/L [CH2 -CH], IMC/L [-CH=CH-], and EMC/L [-CH=CH-]) with mean structural similarity indices of 0.19, 0.04, 0.03, 0.50, 0.45, 0.04, 0.07, and 0.12, respectively, compared with the maps generated by the used Dixon method. Further analysis of voxels with zero structural similarity demonstrated an increased sensitivity of fat fraction lipid maps from the data acquired using this MRSI technique over the standard Dixon technique. The lipid spatial distribution over calf muscles was consistent with previously published findings in adults. Conclusion: This MRSI technique can be a useful tool when individual lipid fat fraction maps are desired within a clinically acceptable time and with a nominal spatial resolution of 0.25 mL.
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    In Vivo Renal Lipid Quantification by Accelerated Magnetic Resonance Spectroscopic Imaging at 3T: Feasibility and Reliability Study
    (MDPI, 2022-04-23) Alhulail, Ahmad A.; Servati, Mahsa; Ooms, Nathan; Akin, Oguz; Dincer, Alp; Thomas, M. Albert; Dydak, Ulrike; Emir, Uzay E.; Radiology and Imaging Sciences, School of Medicine
    A reliable and practical renal-lipid quantification and imaging method is needed. Here, the feasibility of an accelerated MRSI method to map renal fat fractions (FF) at 3T and its repeatability were investigated. A 2D density-weighted concentric-ring-trajectory MRSI was used for accelerating the acquisition of 48 × 48 voxels (each of 0.25 mL spatial resolution) without respiratory navigation implementations. The data were collected over 512 complex-FID timepoints with a 1250 Hz spectral bandwidth. The MRSI sequence was designed with a metabolite-cycling technique for lipid-water separation. The in vivo repeatability performance of the sequence was assessed by conducting a test-reposition-retest study within healthy subjects. The coefficient of variation (CV) in the estimated FF from the test-retest measurements showed a high degree of repeatability of MRSI-FF (CV = 4.3 ± 2.5%). Additionally, the matching level of the spectral signature within the same anatomical region was also investigated, and their intrasubject repeatability was also high, with a small standard deviation (8.1 ± 6.4%). The MRSI acquisition duration was ~3 min only. The proposed MRSI technique can be a reliable technique to quantify and map renal metabolites within a clinically acceptable scan time at 3T that supports the future application of this technique for the non-invasive characterization of heterogeneous renal diseases and tumors.