[Observation and control of hepatic specimens with MRI and MRS].
OBJECTIVE
The purpose of this study was to observe the process of fixation in liver specimens non-invasively by means of magnetic resonance. The fixation process of several formaldehyde-containing solutions was monitored with MRI and MRS at two different temperatures.


METHODS
Liver specimens were conserved in aqueous fixative solutions containing formaldehyde concentrations of 0.7, 1.8, 4 and 7.2 % and at different temperatures of 5 degrees C and 20 degrees C. MRI was performed with T1-, T2- and PD-weighted TSE sequences, a 2D FLASH-sequence with and without magnetization transfer, and a FISP 3D-sequence on a clinical 1.5 Tesla MR whole-body unit, and MRS with (1)H-spectroscopic methods (STEAM-sequence) on a 3 Tesla MR whole-body unit.


RESULTS
The diffusion of formaldehyde into the tissue was best identified on PD- and T1-weighted images as a band under the liver surface with increasing thickness, penetrating especially fast during the first three days. Spectroscopic measurements revealed the rising formaldehyde concentration in the inner part of the organs. Temperature had no significant influence on the velocity of immersing, but cooling conditions produced less gas-filled caverns due to reduced undesired decomposition processes.


CONCLUSIONS
The spatial and temporal process of ongoing fixation in the liver can be monitored by MRI. MRS confirms a rising concentration of formaldehyde during ongoing fixation.
Ludescher
B
B
Sektion für Experimentelle Radiologie, Universität Tübingen. burkhard.ludescher@med.uni-tuebingen.de
Machann
J
J
Graf
H
H
Wietek
B
B
Subke
J
J
Claussen
C D
CD
Schick
F
F
D005404:Fixatives; D005557:Formaldehyde; D006652:Histological Techniques; D006801:Humans; D008099:Liver; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D012996:Solutions; D013696:Temperature; D013997:Time Factors
D005404:Fixatives; D012996:Solutions; D005557:Formaldehyde