Characterization of perfluorocarbon relaxation times and their influence on the optimization of fluorine-19 MRI at 3 tesla

Abstract

Purpose: To characterize and optimize 19 F MRI for different perfluorocarbons (PFCs) at 3 T and to quantify the loss of acquisition efficiency as a function of different temperature and cellular conditions. Methods: T 1 and T 2 relaxation times of the commonly used PFCs perfluoropolyether (PFPE), perfluoro-15-crown-5-ether (PFCE), and perfluorooctyl bromide (PFOB) were measured in phantoms and in several different conditions (cell types, presence of fixation agent, and temperatures). These relaxation times were used to optimize pulse sequences through numerical simulations. The acquisition efficiency in each cellular condition was then determined as the ratio of the signal after optimization with the reference relaxation times and after optimization with its proper relaxation times. Finally, PFC detection limits were determined. Results:The loss of acquisition efficiency due to parameter settings optimized for the wrong temperature and cellular condition was limited to 13%. The detection limits of all PFCs were lower at 24°C than at 37°C, and varied from 11.8±3.0 mM for PFCE at 24°C to 379.9±51.8 mM for PFOB at 37°C. Conclusion: Optimizing 19F pulse sequences with a known phantom only leads to moderate loss in acquisition efficiency in cellular conditions that might be encountered in in vivo and in vitro experiments.

Fluorinated MRI Contrast Agents and Their Versatile Applications in the Biomedical Field

“…Indeed, its half-life is about 12 days compared to 250 for PFCE but its relative sensitivity does not exceed 37 %. Those results were confirmed by Colotti et al [128] in their comparison study on the three commonly used PFC emulsions: PFPE, PFCE and PFOB. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58…”

A characterization of ABL‐101 as a potential tracer for clinical fluorine‐19 MRI

“…At 3 T, the T2/T1 ratio was not as high as that of PFCE but was very close to those of PFOB and PFPE at 24°C and 37°C. 39 This indicates that the obtained SNR per unit of time and per 19 F atom of the pulse sequences should be at least as good as that for PFOB or PFPE at 3 T. Both the T1 and the T2 relaxation times decreased with increasing magnetic field strength, although the T2 values decreased more strongly, as also seen for other PFCs. 41 Only J-coupled T2 values were measured for the CF2 multiplet at 3 T, since the RF bandwidth could not be decreased to selectively excite the CF and CF2 peaks.…”

“…Colotti et al investigated the difference in relaxation times between various in vitro and ex vivo PFPE samples, and observed a mild influence (≤13%) of the difference in relaxation times on the acquisition efficiency. 30 We expect that ABL-101 would demonstrate similarly mild differences in relaxation times in various in vitro and ex vivo conditions. Furthermore, no in vivo relaxation time were measured in this study, because an unlocalized measurement would result in a mix of many tissue compartments with different conditions, while mapping the relaxation times with acceptable precision would most likely take too long.…”

“…The optimized parameters were defined as those that enabled the maximum signal strength per unit time. 14,30 The simulations were run with and without a longitudinal magnetization restoration (LMR) RF pulse of -90° after the echo train.…”

Optimization of steady‐state free precession MRI for lung ventilation imaging with 19F C3F8 at 1.5T and 3T

“…Also, the optimization of SSFP imaging parameters has been investigated for the imaging constraints of HP gas ventilation MRI with both 3 He and 129 Xe . Sequence optimization for perfluorocarbon emulsions has also been performed previously, but in this instance the T 2 and T 1 relaxation parameters are significantly longer than for gas phase perfluorocarbons.…”