MR characteristics and histological correlation in the young pig

Purpose: To correlate magnetic resonance (MR) signal characteristics of bon e bruises with histological findings. Materials and methods: In 14 tibiae o f young pigs, bone bruises were created in the proximal tibial metaphysis. The signal intensity seen on the MR images were correlated with histologica l findings. The following findings were evaluated: (a) changes of signal in tensity on the tibiae; (b) changes of histology on the tibiae; and (c) chan ges of (a) and (b) on follow-up examinations. Results: We observed three ty pes of injuries on T1-weighted images: focal or diffuse low signal, normal signal and linear low signal intensities. Severe hemorrhagic areas showed l ow signal intensities on all sequences of MR imaging. Fast spin-echo (FSE) T2-weighted images showed a more distinct low signal intensity than T1-weig hted images. FSE short tau inversion recovery (STIR) and FSE fat saturated (FSE-FS) T2-weighted images showed similar signal intensities with FSE T2-w eighted images. FS T1-weighted enhanced images showed low signal intensitie s with variable enhancements. Upon histological examination, hemorrhages an d edemas were prominent at the subcortical areas of the contusion sites. Th e areas of dense, low signal intensities in all imaging sequences showed si gns of severe hemorrhage. The areas of diffuse low signal and enhanced area s showed mixed areas of hemorrhages and edemas. Follow-up MR imaging showed evolution of the processes of hemorrhages and edemas with fatty marrow cha nges. Conclusions: MR imaging can depict changes in the bone marrow resulti ng from direct injury to the bone. MR imaging is a useful tool for evaluati ng the evolution of bone bruises. (C) 2001 Elsevier Science Inc. All rights reserved.