Imaging of the gerbil incudostapedial...
Transcript of Imaging of the gerbil incudostapedial...
Developing an accurate mechanical model of the behaviour of a biological system
requires understanding of both the geometry and the material properties of its
components. Gaining structural information about the incudostapedial joint (ISJ)
will be valuable for developing more realistic models of middle-ear mechanics.
There have been a number of anatomical and modelling studies of human, cat and
gerbil ISJ’s (e.g., Funnell et al., 2005, Karmody et al., 2009, Buytaert et al., 2011, Decraemer et al., 2015,
Soleimani et al., 2018a,b). Simplified geometries have been used for modelling and we
have found that the responses of models of the joint are very sensitive to its
geometry. We are doing a post-mortem study of the anatomy of the joint in gerbils
within three hours after sacrifice, using different imaging modalities: stereoscopic
microscope, X-ray nanoCT, and light-sheet microscope.
Adhesive
ISJ
IMJ• We used different imaging modalities to obtain detailed information about
diverse tissues in the ISJ
• The joint may be damaged after repeated pressurization cycles in post-
mortem animals
Imaging of the gerbil incudostapedial joint
Sajjad Feizollah1, Majid Soleimani1, W. Robert J. Funnell1, 2
1Department of BioMedical Engineering, McGill University, QC, Canada, 2Department of Otolaryngology - Head & Neck Surgery, McGill University, QC, Canada
E-mail: [email protected], [email protected], [email protected]
Stapes
➢ Introduction
• The joint is very small and delicate, which makes
extraction and sample preparation very difficult.
➢ Methods: Pressurization
➢ Methods: Auditory bulla dissection
➢ Results: Examples of different imaging modalities
➢ Methods: Sample preparation and imaging
X-ray nano-CT
Fixation with paraformaldehyde
(PFA) in 10X phosphate-buffered
saline (PBS)
Phosphotungstic acid (PTA) staining
Tissue clearing
Hydrogel stabilization
Decalcification with ethylene
diamine triacetic acid (EDTA)
Refractive index matching
• Different sample preparation
methods are used to image various
tissue types for each sample
• Zeiss Xradia 520 Versa X-ray
nanoCT microscope and Zeiss Z.1
light-sheet microscope are used
• Process starts with preparing the
dissected sample for nanoCT
imaging, followed by tissue
clearing for light-sheet microscopy
This study made use of the facilities of McGill’s Advanced BioImaging Facility (for light-
sheet microscopy) and Integrated Quantitative Biology Initiative (for nanoCT). Support from
the Canadian Institutes of Health Research (CIHR) is gratefully acknowledged.
➢ Acknowledgements
➢ Conclusion
• Input pressures applied to ear canal
(multiple cycles)
• Pressure steps of 500 Pa for duration
of 5 seconds per step
➢ Results: Effect of pressurization
Extract bulla
Remove ear-canal pressure
Immobilize stapes using adhesive
Immobilize malleus and incus using adhesive
Seal and pressurize ear canal
Make hole in bulla for incudomallear joint (IMJ)
Make hole in bulla for ISJ
• We developed a dissection method which
preserves the geometry of the joint under
different static pressures while preparing the
sample for imaging
• Stapes, incus and malleus are attached
to the walls of the bulla using All-
Purpose Instant Krazy Glue.
• Changes of the joint are captured
using a stereoscopic microscope
while ear canal is being pressurized.
Stereo microscope X-ray nanoCT Light-sheet microscope
• X-ray nanoCT of a broken
ISJ
• Light-sheet scan of ISJ gap
• 3-D viewing of broken ISJ using different imaging modalities
• After a few full pressure cycles, a sudden change in the ISJ gap was observed in
three animals at high negative pressures (−2000 Pa and −2500 Pa) in which the
gap length had a very high elongation.
• After the sudden change, behaviour of the joint was significantly altered in
subsequent cycles.
• Continuing the pressurization after the sudden change caused the appearance of an
air bubble in the ISJ gap when changing the pressure from −2000 Pa to −2500 Pa.
Comparison of effects
of geometry and
material properties
−2000 Pa −2500 Pa
➢ References
Funnell, W. R. J., Siah, T. H., McKee, M. D., Daniel, S. J., & Decraemer, W. F. (2005): On the coupling between the incus and the
stapes in the cat. Journal of the Association for Research in Otolaryngology, 6(1), 9-18.
Karmody, C. S., Northrop, C. C., & Levine, S. R. (2009): The incudostapedial articulation: new concepts. Otology &
Neurotology, 30(7), 990-997.
Buytaert, J. A., Salih, W. H., Dierick, M., Jacobs, P., & Dirckx, J. J. (2011): Realistic 3D computer model of the gerbil middle ear,
featuring accurate morphology of bone and soft tissue structures. Journal of the Association for Research in Otolaryngology, 12(6),
681-696.
Decraemer, W. F., Maas, S. A., & Funnell, W. R. J. (2015): Finite-element modelling of the synovial fluid and contact in the
incudostapedial joint. 7th International Symposium on Middle-Ear Mechanics in Research and Otology, Aalborg (Denmark).
Soleimani, M., & Funnell, W. R. J. (2018a). Mechanical behaviour of short membranous liquid-filled cylinders under axial
loadings. International Journal of Mechanical Sciences, 145, 138-144.
Soleimani, M., Funnell, W. R. J., & Decraemer, W. F. (2018b): A new finite-element model of the incudostapedial joint. AIP Conf.
Proc. 1965: 110003
Capsule curvature
Capsule Veronda-Westmann
elastic constant C2
Human ISJ model of Soleimani
et al. (ms. in preparation)
−2000 Pa
1st to 4th cycle
−2000 Pa
4th cycle
Sudden elongation at change of
−1.5 kPa to −2 kPa
Right ear of gerbil 3
−2500 Pa
1st to 3rd cycle
−2500 Pa
3rd cycle
Sudden elongation at change of
−2 kPa to −2.5 kPa
Right ear of gerbil 2