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Changes in magnetic resonance imaging relaxation time on postmortem magnetic resonance imaging of formalin-fixed
Kiyokadzu Ebata1,2,3, Sakon Noriki4,5, Kunihiro Inai6,5
1Integrated and Advanced Medical Course, Graduate School of Medical Sciences, University of Fukui, 23-3 Matsuoka Shimoaizuki, Eiheiji-cho, Yoshida-gun, Fukui, 910-1193, Japan. ebatakiyokadzu@gmail.com.
Background:
Postmortem magnetic resonance imaging (MRI) has been used to investigate the cause of death, but due to time constraints, it is not widely applied to the heart. Therefore, MRI analysis of the heart after formalin fixation was previously performed. However, the changes in MRI signal values based on the fixation time of formalin were not investigated. The objective was to investigate changes over time in the T1- and T2-values of MRI signals in normal areas of hearts removed during autopsy, hearts subsequently fixed in formalin, and heart specimens sliced for the preparation of pathological specimens.
Methods:
The study subjects were 21 autopsy cases in our hospital between May 26, 2019 and February 16, 2020 whose hearts were removed and scanned by MRI. The male:female ratio was 14:7, and their ages at death ranged from 9 to 92 years (mean age 65.0 ± 19.7 years). Postmortem (PM)-MRI was conducted with a 0.3-Tesla (0.3-T) scanner containing a permanent magnet. A 4-channel QD head coil was used as the receiver coil. Scans were performed immediately after removal, post-formalin fixation, and after slicing; 7 cases were scanned at all three time points.
Results:
The T1- and T2-values were calculated from the MRI signals of each sample organ at each scanning stage. Specimens were sliced from removed organs after formalin fixation, and the changes in T1- and T2-values over time were graphed to obtain an approximate curve. The median T1-values at each measurement time point tended to decrease from immediately after removal. The T2-values showed the same tendency to decrease, but this tendency was more pronounced for the T1-values.
Conclusion:
MRI signal changes in images of heart specimens were investigated. Formalin fixation shortened both T1- and T2-values over time, and approximation formulae were derived to show these decreases over time. The shortening of T1- and T2-values can be understood as commensurate with the reduction in the water content (water molecules) of the formalin-fixed heart.
Insights
Formalin fixation decreases T1- and T2-values in postmortem (PM) MRI of the heart over time. These MRI signal changes correlate with reduced water content in fixed heart specimens.
Area of Science:
- Forensic pathology
- Medical imaging
- Cardiovascular research
Background:
- Postmortem magnetic resonance imaging (MRI) aids in determining cause of death.
- Time constraints limit routine cardiac MRI application.
- Previous studies analyzed formalin-fixed hearts, but fixation time effects on MRI values were unknown.
Purpose of the Study:
- To investigate temporal changes in T1- and T2-values of cardiac MRI signals.
- To assess signal variations in fresh, formalin-fixed, and sliced heart specimens.
Main Methods:
- 21 autopsy cases (ages 9-92) were included.
- Cardiac MRI scans were performed immediately post-excision, after formalin fixation, and post-slicing.
- T1- and T2-values were calculated at each stage for 7 cases.
Main Results:
- T1-values showed a decreasing trend from immediately after removal.
- T2-values also decreased, with a more pronounced reduction observed in T1-values.
- Formalin fixation progressively shortened T1- and T2-values over time.
Conclusions:
- Formalin fixation significantly impacts cardiac MRI signal values.
- T1- and T2-value shortening correlates with decreased water content in fixed hearts.
- Approximation formulae were derived to quantify these time-dependent MRI signal changes.
