Simple methods for the correction of T-2 maps of phantoms

Two simple methodologies for correcting the errors in T-2 maps for phantom measurements are presented; they both give accurate MRI maps with a low coe fficient of variation (CV). The rate correction method is based on an equat ion relating the true T-2 (T-2,(t)) and that determined experimentally (T-2 ,(exp)) for homogenous phantoms. The response matrix method is a phenomenol ogical analysis of the difference between T-2,(exp) and T-2,(t), from which correction factors are computed for a range of T-2 values and for every pi xel of an image. The factors were obtained from phantoms filled with a homo geneous gelatin gel and having different T-2,(t) values. The CV in homogene ous phantom measurements were reduced from 2.5-4.0% to approximately 0.62.0 % for T-2,(t) values ranging from 180-600 ms. Examples are shown for the co rrection of T-2 maps of phantoms filled with polymer dosimeter gel irradiat ed with photon beams from a linear accelerator. The methodologies presented can easily be implemented on a clinical MRI scanner. (C) 2001 Wiley-Liss, Inc.