Bi-exponential T2 decay in dairy cream phantoms.

MRI phantoms are an important part of any experiment because they provide a reference of known parameters. There are many choices of mono-exponential T2 phantoms, but few choices for bi-exponential T2 phantoms. We have found that dairy cream provides an excellent bi-exponential T2 model with similar relaxation times to those found in white matter. Five cream phantoms of different milk fat percentages (2, 6, 10, 18 and 35 %) were imaged with an optimized Carr-Purcell-Meiboom-Gill sequence. The decay curves for each of the phantoms were fit using Non-Negative Least Squares. We found that the short T2 component fraction relative to the total energy in the distribution correlated linearly (r = 0.9973) with the milk fat percentage. The short T2 time was 38+/-4 ms and the long T2 time was 135+/-4 ms.