Prototype for automated 3D-grinding preparation of the temporal bone: study on the system precision

Introduction:

The micro-grinding preparation of the temporal bone is an impressive but time-consuming method for visualisation of the cochlear anatomy including the positional relation to a cochlear implant (CI electrode. To date an isotropic image (i.e. equal resolution in all 3 axis) was not feasible. The aim of the study is the implementation of a partly automated preparation system with an isotropic resolution < = 20 µm.

Material and methods:

A prototype of an automated grinding preparation has been realized by use of a CNC-milling machine, a high precision lifter table and a digital microscope. For the purpose of a system validation the repetitive accuracy for x/y-positioning and die abrasion accuracy in the z-axis were determined for 100 iterations each. In addition, the time for 1,000 successive microsections of a cochlear specimen has been measured.

Results:

The proof of feasibility has been provided by the successful implementation of the prototype. The repetitive accuracy in x- and y-direction was 2.3 ± 3.1 µm and in the z-direction 2.84 ± 4.8 µm. The expenditure of time was 47 s per image and the overall duration was about 14 hours for the entire specimen.

Conclusion:

A partly automated system for micro-preparation of epoxy-embedded temporal bone specimen has been implemented. As results the resolution in the z-axis improved significantly while the time consumption of the process decreased dramatically. The next stage of development has the objective of fully automation. The intended purpose of this instrument is a more detailed assessment of intracochlear deterioration by upcoming CI electrode prototypes.

Publication History

Publication Date:
23 April 2019 (online)