Structural analysis of micro-channels in human temporal bone
TL;DR: A structural analysis of the microchannels of the human temporal bone is proposed to corroborate their role as a new separate blood supply for the mucosa of the mastoid air cells and provide new and relevant information about the micro-channels but also their connections to mastoids air cells.
Abstract: Recently, numerous micro-channels have been discovered in the human temporal bone by micro-CT-scanning. Preliminary structure of these channels has suggested they contain a new separate blood supply for the mucosa of the mastoid air cells, which may have important functional implications. This paper proposes a structural analysis of the microchannels to corroborate this role. A local structure tensor is first estimated. The eigenvalues obtained from the estimated local structure tensor were then used to build probability maps representing planar, tubular, and isotropic tensor types. Each tensor type was assigned a respective RGB color and the full structure tensor was rendered along with the original data. Such structural analysis provides new and relevant information about the micro-channels but also their connections to mastoid air cells. Before carrying a future statistical analysis, a more accurate representation of the micro-channels in terms of local structure tensor analysis using adaptive filtering is needed.
Summary (2 min read)
- A recent study using micro-CT scans of human temporal bone specimens has revealed the existence of multiple microchannels carved in the bone surrounding the mastoid air cell system .
- This new potential role may be strengthened further by a detailed structural analysis of the micro-channels, where their similarities with a vascular network are qualitatively investigated together with their communication with the mucosa at the surface of the mastoid air cells.
- Observations based on histological sections have revealed the presence of both arterioles and venules inside.
- Therefore, their structural content also needs to be taken into consideration.
- Local structure tensor analysis based on a second order tensor with six degrees of freedom in 3D may be a more robust representation of the channels .
- One human temporal bone specimen was used in this study.
- The bone specimen was scanned at the Department of Physics and Astronomy, Ghent, Belgium, using the same procedure as in [1, 7].
- This test volume was chosen to represent micro-channels at the level of the ear canal (EC) and in the proximity of mastoid air cell system (MACS) with a large variety of sizes and shapes.
- The data is partially represented on Figure 1a using volume rendering with a default ramp transfer function (TF) .
- Such structures can be represented using a structure tensor by its corresponding eigenvalues and eigenvectors.
- A typical frequency function used as quadrature filter is given below Fk(û) = R(ρ)Dk(û) (4) To pick up energy in all possible orientations, the quadrature filter is built as spherically separable in the Fourier domain with an arbitrary but positive radial bandwidth functionR(ρ), with ρ = ||û||, and a direction function Dk(û).
- It determines in what scale the filter has its sensitivity.
- To assess the resulting p1, p2, and p3 from the estimated structure tensor, the authors used volume rendering through MeVisLab, a free medical image processing and visualization software.
- To visualize this natural transition between the three cases, a lookup table (LUT) was created where each RGBA channel corresponds a specific case, namely the rank 2 tensor was assigned the red color, the rank 3 tensor was assigned the green color, and the rank 1 tensor was assigned the blue color.
4. RESULTS AND DISCUSSION
- Before presenting and discussing the results, it should be noted that the local structure tensor analysis does not inform about the specific tissue type, rather a description of how planar, tubular, or isotropic a local structure is.
- Figure 4 gives a non-exhaustive representation of micro-channels with various different shapes encountered during the analysis.
- Figure 4E reveals a flatten micro-channel with seemingly several rank 2 tensor type structures in the central part, and surrounded by a rank 1 tensor type structure.
- Figure 4H describes a similar hub structure having more connections.
- The same applies to the lower right part of the middle mastoid air cell where two micro-channels clearly connect to a hub structure.
- This study has demonstrated the structural variation of contents inside the micro-channels by a local structure tensor analysis.
- From this analysis, discovery of unreported hub structures may help understand the origin and possible multi-role of this complex network formed by these micro-channels.
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Cites background or methods or result from "Structural analysis of micro-channe..."
...In order to gain further knowledge about these micro-channels, a geometrical analysis has been carried out using a micro-CT scan of a single human temporal bone specimen ....
...each neighbourhood belonging to either a rank 1, rank 2, or a rank 3 tensor, as defined in  and recalled from , can further be investigated from the local structure tensor by p1, p2, and p3, where ∑3 k=1 pk = 1, as...
...8 but with a transfer function defined in ....
...This study therefore proposes an extension of the local structure tensor analysis (), by enhancing the micro-CT data, while reducing the noise level using adaptive filtering ....
...Although the results from the current study are very similar to the results from the anisotropic diffusion scheme, it can be noticed that the tubular structures appear more complete especially when compared to p1, p2, p3 rank tensors mixture from the previous study ....
Cites background or methods from "Structural analysis of micro-channe..."
...The bone specimen was scanned in Ghent at the Department of Physics and Astronomy, Belgium using a procedure used for scanning similar to  and ....
...The steps to estimate the structure tensor from the quadrature filters are already described in ....
...However, the current work is an extension of the work achieved in  and , in which the eigenvalues could easily be used to extract both the surface and curve skeletons....
...(3) As stated in , to obtain rank 1, rank 2 and rank 3 tensors, a set of quadrature filter responses were computed over the whole volume so as to estimate the structure tensor given in Eq....
"Structural analysis of micro-channe..." refers background in this paper
...This resembles to a vascular network and could lead to the use of existing vessel segmentation methods ....
"Structural analysis of micro-channe..." refers methods in this paper
...A better representation of the micro-channels is possible using a trapezoidal transfer function by only selecting the voxels representing the bone surface ....
...The data is partially represented on Figure 1a using volume rendering with a default ramp transfer function (TF) ....
"Structural analysis of micro-channe..." refers methods in this paper
...The bone specimen was scanned at the Department of Physics and Astronomy, Ghent, Belgium, using the same procedure as in [1, 7]....
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Frequently Asked Questions (2)
Q1. What have the authors contributed in "Structural analysis of micro-channels in human temporal bone" ?
This paper proposes a structural analysis of the microchannels to corroborate this role.
Q2. What have the authors stated for future works in "Structural analysis of micro-channels in human temporal bone" ?
Presence of noise within the air cells along with the missing information in some micro-channels suggest the future need of image enhancement using an adaptive filtering technique based on the local structure tensor analysis used in this study. A larger scale study is also considered in the future in order to validate the method proposed in this pre-analysis.