RADIOTHERAPY EFFECTS ON VERTEBRAL BONE-MARROW - EASILY RECOGNIZABLE CHANGES IN T-2 RELAXATION-TIMES

The effect of localized radiotherapy on vertebral bone marrow was demo nstrated in two patients using quantitative MRI studies with pixel-by- pixel measurement of T-2 relaxation times with generation of T-2 image s, Conventional T-1-weighted spin-echo images were obtained as well. I rradiated vertebral bone marrow was found to have longer T-2 relaxatio n times than the neighboring nonirradiated bone marrow. These changes corresponded to the increased signal intensity on T-1-weighted images and to the field of radiotherapy and were noted 2.5 to 32 mo after rad iotherapy, Radiologists should be aware of the increased T-2 relaxatio n times in irradiated bone marrow to correctly assess spinal disorders in irradiated patients, The reported T-2 changes may reflect the abun dance of adipose cells that proliferate in bone marrow after radiother apy, or may indicate an additional histological change, such as bone m arrow necrosis or edema, Conclusive histological proof remains to be o btained.