Simple methods for the correction of T2 maps of phantoms.

Two simple methodologies for correcting the errors in T2 maps for phantom measurements are presented; they both give accurate MRI maps with a low coefficient of variation (CV). The rate correction method is based on an equation relating the true T2 (T2,t) and that determined experimentally (T2,exp) for homogenous phantoms. The response matrix method is a phenomenological analysis of the difference between T2,exp and T2,t, from which correction factors are computed for a range of T2 values and for every pixel of an image. The factors were obtained from phantoms filled with a homogeneous gelatin gel and having different T2,t values. The CV in homogeneous phantom measurements were reduced from 2.5-4.0% to approximately 0.6-2.0% for T2,t values ranging from 180-600 ms. Examples are shown for the correction of T2 maps of phantoms filled with polymer dosimeter gel irradiated with photon beams from a linear accelerator. The methodologies presented can easily be implemented on a clinical MRI scanner.