Room: AAPM ePoster Library
Purpose: The purpose of this work was to measure the dependence of T1, T2 and T1rho with temperature in agarose gel phantoms intended as reference standards for relaxation time measurements to follow articular cartilage degeneration.
Methods: Images designed to measure T1, T2 and T1rho were acquired six samples of agarose gel with concentrations of 2%, 3% and 4% w/v. The phantom was imaged using the transmit / receive 15 channel knee coil on a Siemens Prisma, 3T. The temperature of the phantom was varied by wrapping it in a water jacket connected to a temperature-controlled circulation system. Relaxation times were derived from ROI estimates of image intensity and fit to a mono-exponential decay model using non-linear least squares MATLAB code.
Results: were acquired on the phantom at five temperatures ranging from 3 °C to 26 °C. The temperature difference of the phantom from the start to the end of imaging was less than 0.5 °C. Calculated relaxation times were plotted as relaxation time versus temperature. The data were well fit with linear least squares to a first order polynomial. The variation of the relaxation times with temperature were, 24, 20 and 18 ms/°C for T1 and -2.0, -1.4 and -1.2 ms/°C for T1rho measured in agarose gel samples with concentrations of 2%, 3% and 4% respectively.
Conclusions: Our work is consistent with the variation of T1 observed by others. However, our work is the first to measure the temperature dependence of T1rho. Our work is important because of the interest in using T1rho as a measure of tissue changes associated with diseases including, changes in articular cartilage with osteoarthritis. Our results indicate a substantial variation in T1rho, on the order of -1 to -2 ms/°C, can occur due to variations in ambient temperature.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by a grant from the Arthritis Foundation (XL)