MR imaging-histopathologic correlation of thermal injuries induced with interstitial Nd:YAG laser irradiation in the...

Magnetic resonance (MR) imaging-histopathologic correlation of thermal injuries induced with interstitial laser irradiation was performed in a chronic model up to 12 weeks after laser exposure. T2-weighted MR images showed irreversible coagulative necrosis as a low-signal-intensity area. A higher-intensity surrounding area, corresponding to edema, was also present in acute lesions on T2-weighted images. Serial studies of the chronic model showed that a substantial portion of the interstitial edema zone progressed to coagulative necrosis up to 7 days after laser irradiation. This necrotic zone decreased in size beyond 2 weeks, presumably through biologic healing. MR imaging and pathologic findings correlated well in the chronic model. MR imaging has the potential to depict acute, irreversible thermal damage even before morphologic change is seen at the standard pathologic examination. Recognizing the dynamics of tissue response to interstitial laser irradiation on MR images is valuable for estimation of true lesion volume.