Prof. Helge Rask-Andersen explained that he had always believed that micro-CT imaging was the best 3D imaging technique available.

However, Prof. Sumit Agrawal later demonstrated to him the substantial superiority of a new research tool—synchrotron radiation phase contrast imaging—which allows for accurate 3D reconstructions of more anatomical details than ever before. They have collaborated ever since.

In their studies on Prof. Rask-Andersen’s “favorite topic of the human cochlear anatomy,”

 They found that although the first turn of the spiral ganglia corresponds to 80% of the total spiral ganglia length, the second turn contains about 1000 neurons which is 1/3 of the total number of neurons.

They reconstructed the profile of the secondary spiral lamina in 3D and found that Cochleostomy will likely damage this refined anatomical structure.

That is why Prof. Rask-Andersen believes that a “Cochleostomy is not a hearing preservation technique.”

Prof. Agrawal elaborated on the significance of the large number of neurons within the second cochlear turn for pitch mapping of CI users

and demonstrated that, when tracing the dendritic connections between the organ of Corti and the spiral ganglia, they discovered a large portion of low frequency information is processed in the relatively small second turn of the spiral ganglia.

Tracing dendrites also revealed that—below 500 degrees of insertion—there is really no difference between the angle-to-frequency maps of the organ of Corti and the spiral ganglia.

An additional, interesting landmark discovery was that all frequency information below 1kHz is processed beyond the first cochlear turn for both the organ of Corti and the spiral ganglia

Based on synchrotron data and new findings regarding the hook region and helicotrema, they developed a new, individualized pitch mapping formula that seems superior to the approach proposed by Stakhovskaya et al.in 2007.

·         This approach requires the total number of cochlear turns to be an input, and they are working on an automated approach to assess this parameter and thereby avoid inter-observer variability for more reliable, individualized pitch mapping.