Forensic Brain MRI
Claudia Lenz1 and Eva Scheurer1
1University of Basel, Basel, Switzerland

Synopsis

Keywords: Neuro: Brain

Forensic medicine employs scientific disciplines to solve legal queries, with forensic imaging, including MRI, as its newest branch. Postmortem cases are investigated to clarify the cause and manner of death, to reconstruct violent events, to determine the time of death and the presence of diseases. Postmortem MRI faces challenges such as temperature variations, postmortem changes and formalin fixation effects. This talk gives an overview on the advantages and challenges of in situ and ex situ postmortem examinations. It emphasizes methods for adapting MRI techniques for forensic brain MRI, highlighting the current research for forensic purposes and the validation of biomarkers.

Introduction

Forensic medicine is a specialized scientific discipline dedicated to answering questions arising in criminal proceedings and other legal contexts, which can solely be solved by using scientific methods and knowledge from fields such as medicine, biology, chemistry, and physics. The newest subspecialty is forensic imaging including radiological methods, such as MRI. While important forensic questions also concern living persons, such as in criminal and sexual assault or child abuse, this talk will be limited to the investigation of postmortem cases. In postmortem forensic medicine, the main goals of an examination of the brain are to clarify the manner and cause of death, to reconstruct events in cases of trauma, to determine the time of death, and to evaluate the presence of chronic diseases / residual changes at time of death.

Methodological challenges and solutions

Postmortem MRI not only differs fundamentally from clinical examinations of the living, but also strongly depends on the examination situation itself (i.e. in situ or ex situ). Hence, there exist various methodological challenges, which need to be taken into account when performing postmortem MRI:

  • Temperature
After death, the body cools depending on time since death, ambient temperature, the weight and stature, and the clothing of the body causing core temperatures at the start of an MR scan between 4° and 36°C. Temperature has a relevant influence on relaxation times and diffusion parameters [1–7].

  • Postmortem changes
With increasing postmortem interval, several changes occur due to redistribution of water, changes in water content and degradation processes. These changes have an influence on relaxation times, diffusivity, and susceptibility, e.g. by gas formation [8,9].

  • Motion
Obviously, no artefacts due to patient movement or due to physiological motion exist in postmortem examinations. However, the absence of circulation also limits the application of angiography or contrast enhanced examinations.

  • Metallic objects
Particularly in forensic postmortem MRI, care must be taken, as projectiles and other foreign objects might be ferromagnetic. Additionally, in forensic cases usually no information on medical history including the presence of implants is available.

  • Wrapping and positioning of the body (only in situ)
Adequate wrapping of the body is essential not only for hygienic reasons, but also to prevent artefacts from metal parts such as zippers. Correct positioning of the head may be difficult because of the body bag and rigor mortis, as well as severely injured bodies.

  • Effects of formalin fixation (only ex situ)
After extraction of the brain at autopsy, the brain needs to be fixated using formalin in order to prevent degradation of the tissue. After fixation, the brain can be examined as a whole or it can be investigated as smaller tissue samples for validation of imaging biomarkers using histology and other invasive methods.

Conclusion

In order to take optimal profit of postmortem MRI in forensic medicine, the above-mentioned methodological challenges need to be considered. The talk will give an insight into the current state of research in forensic brain MRI, cover advantages and challenges of in situ versus ex situ examinations, effects of temperature and how to correct for it [1–7], effects of formalin fixation [10,11], and opportunities for validating imaging biomarkers using histology and other methods [12,13].

Acknowledgements

Many thanks to all collaborators and colleagues for their support, slides and data, and special thanks to Dr. Celine Berger, Dr. Melanie Bauer, Dominique Neuhaus and Andrea Zirn for their exceptional assistance.

References

[1] T.D. Ruder, G.M. Hatch, L. Siegenthaler, G. Ampanozi, S. Mathier, M.J. Thali, O.M. Weber, The influence of body temperature on image contrast in post mortem MRI, Eur. J. Radiol. 81 (2012) 1366–1370. https://doi.org/10.1016/j.ejrad.2011.02.062.

[2] W.-D. Zech, N. Schwendener, A. Persson, M.J. Warntjes, C. Jackowski, Temperature dependence of postmortem MR quantification for soft tissue discrimination, Eur. Radiol. 25 (2015) 2381–2389. https://doi.org/10.1007/s00330-015-3588-4.

[3] K. Tashiro, S. Shiotani, T. Kobayashi, K. Kaga, H. Saito, S. Someya, K. Miyamoto, H. Hayakawa, Cerebral relaxation times from postmortem MR imaging of adults, Magn. Reson. Med. Sci. MRMS Off. J. Jpn. Soc. Magn. Reson. Med. 14 (2015) 51–56. https://doi.org/10.2463/mrms.2013-0126.

[4] C. Birkl, C. Langkammer, J. Haybaeck, C. Ernst, R. Stollberger, F. Fazekas, S. Ropele, Temperature-induced changes of magnetic resonance relaxation times in the human brain: A postmortem study, Magn. Reson. Med. 71 (2014) 1575–1580. https://doi.org/10.1002/mrm.24799.

[5] C. Berger, C. Birkl, M. Bauer, E. Scheurer, C. Lenz, Technical note: Quantitative optimization of the FLAIR sequence in post mortem magnetic resonance imaging, Forensic Sci. Int. 341 (2022) 111494. https://doi.org/10.1016/j.forsciint.2022.111494.

[6] C. Berger, M. Bauer, H. Wittig, E. Scheurer, C. Lenz, Post mortem brain temperature and its influence on quantitative MRI of the brain, Magn. Reson. Mater. Phys. Biol. Med. 35 (2022) 375–387. https://doi.org/10.1007/s10334-021-00971-8.

[7] C. Berger, M. Bauer, E. Scheurer, C. Lenz, Temperature correction of post mortem quantitative magnetic resonance imaging using real-time forehead temperature acquisitions, Forensic Sci. Int. 348 (2023) 111738. https://doi.org/10.1016/j.forsciint.2023.111738.

[8] J. Tschui, C. Jackowski, N. Schwendener, C. Schyma, W.D. Zech, Post-mortem CT and MR brain imaging of putrefied corpses, Int. J. Legal Med. 130 (2016) 1061–1068. https://doi.org/10.1007/s00414-016-1385-5. [9] T.D. Ruder, M.J. Thali, G.M. Hatch, Essentials of forensic post-mortem MR imaging in adults, Br. J. Radiol. 87 (2014) 20130567. https://doi.org/10.1259/bjr.20130567.

[10] C. Birkl, C. Langkammer, N. Golob-Schwarzl, M. Leoni, J. Haybaeck, W. Goessler, F. Fazekas, S. Ropele, Effects of formalin fixation and temperature on MR relaxation times in the human brain, NMR Biomed. 29 (2016) 458–465. https://doi.org/10.1002/nbm.3477.

[11] R.L.C. Barrett, D. Cash, C. Simmons, E. Kim, T.C. Wood, R. Stones, A.C. Vernon, M. Catani, F. Dell’Acqua, Tissue optimization strategies for high-quality ex vivo diffusion imaging, NMR Biomed. 36 (2023) e4866. https://doi.org/10.1002/nbm.4866.

[12] C. Langkammer, N. Krebs, W. Goessler, E. Scheurer, F. Ebner, K. Yen, F. Fazekas, S. Ropele, Quantitative MR imaging of brain iron: a postmortem validation study, Radiology 257 (2010) 455–462. https://doi.org/10.1148/radiol.10100495.

[13] A. De Barros, G. Arribarat, J. Combis, P. Chaynes, P. Péran, Matching ex vivo MRI With Iron Histology: Pearls and Pitfalls, Front. Neuroanat. 13 (2019) 68. https://doi.org/10.3389/fnana.2019.00068.


Proc. Intl. Soc. Mag. Reson. Med. 32 (2024)