mri evaluation of rabbit bone marrow after acute irradiation

background: magnetic resonance imaging (mri) is a safe modality and useful in characterizing normal and abnormal bone marrow (bm). mri also presents a more global view of bm than biopsy therefore, it may provide a better understanding of hematologic disorders. the purpose of this study was to monitor radiation-induced alterations of bm in acute phase of irradiation (1-10 day after total body irradiation (tbi)) with conventional mri. materials and methods: twelve new zealand adult male white rabbits (10 for tbi and 2 as controls) were irradiated to 6 gy gamma rays. mri was performed for each rabbit femoral marrow and marginal muscles around femur region (as internal control) using t1- weighted (w) and spir (tr/te 631/15) techniques before and after (24h, 48h, 72h, 5d, 10d) post tbi. results: the results were expressed as mr signal ratio (mean mr signal of femur/mean mr signal of muscle). the bm mr –signal intensity (si) values were subsequently compared to the histologic values of bm cellularity, edema and hemorrhage. values of t1-si of bm for 1 to 5 days after irradiation was smaller than those the values for before irradiation data (p < 0.006). spir-si values of bm in 3, 5 and 10 days were less than values for before irradiation (p < 0.001). since si depends to edema and hemorrhage the high correlation between cellularity and t1-si (r = 0.725, p = 0.018) or spir-si(r = 0.814, p = 0.004) was not found. conclusion: this study indicated that radiation-induced modification of bm-si is tightly linked to the parameters like decline of all hematopoietic cell lines, edema and hemorrhage. it was concluded that mri can distinguish normal from irradiated bm so that radiation-induced alterations in bm could be assessed with mri. iran . j. radiat. res., 2004 2 (3): 117-126