MR microscopy of formalin fixed paraffin embedded histology specimens

Abstract

Archived formalin-fixed paraffin-embedded (FFPE) tissue collections represent a valuable informational resource for numerous studies. However, there is no NMR signal from FFPE specimens at room temperature. To obtain MR images and enable comparison of magnetic resonance microscopy (MRM) and histology studies we propose to image FFPE tissue at elevated temperature. A FFPE tissue block was imaged at 7 Tesla (T) and 16.4T at 70-80°C using T2 -weighting methods. The only difference from standard MR microscopy (MRM) is elevated temperature at which the embedding medium melts. Using FFPE murine brain tissue, we were able to demonstrate the feasibility of tissue MRM from paraffin embedded specimens. Histology images taken from the specimen after MRM demonstrate that keeping the FFPE specimen in paraffin melt at 70-80°C for dozens of hours does not affect subsequent histology analysis. MRM of FFPE tissue from paraffin melt opens new avenues for analyzing archived histological specimens (biopsies, post mortem, etc.) and for correlating MR images with histology (optical microscopy). In addition, 3D MRM of FFPE specimens could guide histology in search for appropriate regions of interest and subsequently minimize occurrences of false negatives in tissue analysis.