Gd-DTPA enhanced magnetic resonance imaging (MRI) for the follow-up of laser-induced thermotherapy (LITT) - Trial to determine a useful examination schedule

Purpose: To evaluate gadolinium-DTPA-enhanced MRI for follow-up monitoring of laser-induced thermotherapy (LITT) and to determine of a useful examination schedule. Materials and Methods: LITT of the liver was performed in 55 rabbits using a Nd:YAG laser (4 w power output, 840 s exposure time). Gd-DTPA MRI and histological examinations were performed at different times (0-168 days). Results: Laser-induced lesions underwent regeneration and volume size reduction (69% after 168 days). The correlation coefficient (MR vs macroscopic analysis) for the mean lesion diameter was r=0.96. Histology of lesions comprised the four zones that correlated best with MRI findings. Coagulation necroses immediately after LITT were seen as an area of no enhancement on Gd-DTPA MRI. Circular enhancement was first seen 72-96 hours after LITT, which was due to early mesenchymal proliferation. Conclusions: Gd-DTPA MRI is a good monitoring procedure for LITT. MRI should be performed 24 and 96 hours after LITT.