Mikko J Nissi1,2,3, Lauri J Lehto2,4, Curtis A Corum2, Djaudat Idiyatullin2, Jutta M Ellermann2, Olli H J Gröhn4, Miika T Nieminen5,6. 1. Department of Applied Physics, University of Eastern Finland, Kuopio, Finland. 2. Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, Minnesota, USA. 3. Department of Orthopaedic Surgery, University of Minnesota, Minneapolis, Minnesota, USA. 4. Department of Neurobiology, A.I. Virtanen Institute for Molecular Medicine, University of Eastern Finland, Kuopio, Finland. 5. Department of Diagnostic Radiology, Oulu University Hospital and University of Oulu, Oulu, Finland. 6. Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland.
Abstract
PURPOSE: To evaluate the feasibility of SWIFT with variable flip angle (VFA) for measurement of T1 relaxation time in Gd-agarose-phantoms and osteochondral specimens, including regions of very short T2 *, and compare with T1 measured using standard methods METHODS: T1 s of agarose phantoms with variable concentration of Gd-DTPA2- and nine pairs of native and trypsin-treated bovine cartilage-bone specimens were measured. For specimens, VFA-SWIFT, inversion recovery (IR) fast spin echo (FSE) and saturation recovery FSE were used. For phantoms, additionally spectroscopic IR was used. Differences and agreement between the methods were assessed using nonparametric Wilcoxon and Kruskal-Wallis tests and intraclass correlation. RESULTS: The different T1 mapping methods agreed well in the phantoms. VFA-SWIFT allowed reliable measurement of T1 in the osteochondral specimens, including regions where FSE-based methods failed. The T1 s measured by VFA-SWIFT were shifted toward shorter values in specimens. However, the measurements correlated significantly (highest correlation VFA-SWIFT versus FSE was r = 0.966). SNR efficiency was generally highest for SWIFT, especially in the subchondral bone. CONCLUSION: Feasibility of measuring T1 relaxation time using VFA-SWIFT in osteochondral specimens and phantoms was demonstrated. A shift toward shorter T1 s was observed for VFA-SWIFT in specimens, reflecting the higher sensitivity of SWIFT to short T2 * spins. Magn Reson Med 74:175-184, 2015.
PURPOSE: To evaluate the feasibility of SWIFT with variable flip angle (VFA) for measurement of T1 relaxation time in Gd-agarose-phantoms and osteochondral specimens, including regions of very short T2 *, and compare with T1 measured using standard methods METHODS: T1 s of agarose phantoms with variable concentration of Gd-DTPA2- and nine pairs of native and trypsin-treated bovinecartilage-bone specimens were measured. For specimens, VFA-SWIFT, inversion recovery (IR) fast spin echo (FSE) and saturation recovery FSE were used. For phantoms, additionally spectroscopic IR was used. Differences and agreement between the methods were assessed using nonparametric Wilcoxon and Kruskal-Wallis tests and intraclass correlation. RESULTS: The different T1 mapping methods agreed well in the phantoms. VFA-SWIFT allowed reliable measurement of T1 in the osteochondral specimens, including regions where FSE-based methods failed. The T1 s measured by VFA-SWIFT were shifted toward shorter values in specimens. However, the measurements correlated significantly (highest correlation VFA-SWIFT versus FSE was r = 0.966). SNR efficiency was generally highest for SWIFT, especially in the subchondral bone. CONCLUSION: Feasibility of measuring T1 relaxation time using VFA-SWIFT in osteochondral specimens and phantoms was demonstrated. A shift toward shorter T1 s was observed for VFA-SWIFT in specimens, reflecting the higher sensitivity of SWIFT to short T2 * spins. Magn Reson Med 74:175-184, 2015.
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