Shiguetomi Medina, Juan Manuel4; Ramirez Garcia-Luna, Jose Luis3; Rahbek, Ole4; Stødkilde-Jørgensen, Hans5; Møller-Madsen, Bjarne4
1 Department of Clinical Medicine - The Department of Orthopaedics E, ?AS, Department of Clinical Medicine, Health, Aarhus University2 Department of Clinical Medicine - The MR Research Centre, Department of Clinical Medicine, Health, Aarhus University3 Departamento de Salud Publica, Universidad Autonoma de San Luis Potosi.4 Department of Clinical Medicine - The Department of Orthopaedics E, ?AS, Department of Clinical Medicine, Health, Aarhus University5 Department of Clinical Medicine - The MR Research Centre, Department of Clinical Medicine, Health, Aarhus University
Background Water is present in all human body. Healthy tissues encompass an intricate balance of water inside cells and extracellular matrix. Disease can cause this relation to be altered. It has been published that MR technology is able to measure water content, but no quantitative method has been described. Purpose/Aim of Study Development of a mathematical model to measure the water content in tissue using T1-values obtained from MR. Materials and Methods T-1 values were obtained from 45 samples from tissue-mimicking gelatin with previously known water concentrations. We analyzed the samples in a 1.5 Tesla by calculating absolute T1 values in real maps through inverse angle phase inverse sequence recuperation (11 inversion times, from 200 to 2200 msec) at 37(±0.5) °C. Regions of interest were manually delineated and the mean T1 value was estimated using a T1-map analysis software. The collected data was modeled in a linear regression by fitting the values in the equation Water Content ~ T1-value at 95% confidence level. Findings/Results The model was found to be statistically significant against a null model (p < 0.001). R2 value was 0.973, meaning that 97.3% of the variation in Water Content can be explained by the T1 value. We validated the method with 150 bootstrap repetitions to an R2 corrected index of 0.9715. If T1 Signal Intensity is increased by 1 unit, Water content is increased by 0.019% [95% CI: 0.00018 – 0.00020], p < 0.001. Water content in percentage can be predicted with absolute T1 values in real maps and inverse sequence recuperation by the equation Water Content = (0.476 + T1 Signal Intensity * 0.000193) * 100. Conclusions It is possible to calculate water content in a tissue using absolute T1-values from MR. This technology allows quantification of disease manifestations such as edema. This is an experimental model and it has to be validated for human tissue.