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Abstract
PurposeA shortage of suitable donor livers is driving increased use of higher risk livers for transplantation. However, current biomarkers are not sensitive and specific enough to predict posttransplant liver function. This is limiting the expansion of the donor pool. Therefore, better noninvasive tests are required to determine which livers will function following implantation and hence can be safely transplanted. This study assesses the temperature sensitivity of proton density fat fraction and relaxometry parameters and examines their potential for assessment of liver function ex vivo.MethodsSix ex vivo human livers were scanned during static cold storage following normothermic machine perfusion. Proton density fat fraction, T1, T2, and were measured repeatedly during cooling on ice. Temperature corrections were derived from these measurements for the parameters that showed significant variation with temperature.ResultsStrong linear temperature sensitivities were observed for proton density fat fraction (R2 = 0.61, P < .001) and T1 (R2 = 0.78, P < .001). Temperature correction according to a linear model reduced the coefficient of repeatability in these measurements by 41% and 36%, respectively. No temperature dependence was observed in T2 or measurements. Comparing livers deemed functional and nonfunctional during normothermic machine perfusion by hemodynamic and biochemical criteria, T1 differed significantly: 516 ± 50 ms for functional versus 679 ± 60 ms for non-functional, P = .02.ConclusionTemperature correction is essential for robust measurement of proton density fat fraction and T1 in cold-stored human livers. These parameters may provide a noninvasive measure of viability for transplantation.
Highlights
Liver transplantation is the only definitive treatment for end- stage liver disease
The signal detected by MR methods is intrinsically a function of the net tissue magnetisation, which is described by the Boltzmann distribution, and the tissue relaxation rates, which are predominantly determined by the rate of molecular tumbling
Significant differences were observed in both imaging (ShMOLLI) and spectroscopic (STEAM-IR) T1 measurements between the livers deemed functional by the viability criteria and those deemed nonfunctional (516 ± 52 ms vs. 679 ± 60 ms, P = .02, for shortened MOLLI (ShMOLLI) T1; 636 ± 50 ms vs. 762 ± 25 ms, P = .02, for STEAM-IR T1)
Summary
This study assesses the temperature sensitivity of proton density fat fraction and relaxometry parameters and examines their potential for assessment of liver function ex vivo. Results: Strong linear temperature sensitivities were observed for proton density fat fraction (R2 = 0.61, P < .001) and T1 (R2 = 0.78, P < .001). Conclusion: Temperature correction is essential for robust measurement of proton density fat fraction and T1 in cold-stored human livers. These parameters may provide a noninvasive measure of viability for transplantation. KEYWORDS liver transplantation, MOLLI T1, normothermic machine perfusion, proton density fat fraction, static cold storage, temperature sensitivity
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