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Automated 3D segmentation of multiple surfaces with a shared hole: segmentation of the neural canal opening in SD-OCT volumes.
Med Image Comput Comput Assist Interv. 2014;17(Pt 1):739-46
Authors: Antony BJ, Miri MS, Abràmoff MD, Kwon YH, Garvin MK
The need to segment multiple interacting surfaces is a common problem in medical imaging and it is often assumed that such surfaces are continuous within the confines of the region of interest. However, in some application areas, the surfaces of interest may contain a shared hole in which the surfaces no longer exist and the exact location of the hole boundary is not known a priori. The boundary of the neural canal opening seen in spectral-domain optical coherence tomography volumes is an example of a "hole" embedded with multiple surrounding surfaces. Segmentation approaches that rely on finding the surfaces alone are prone to failures as deeper structures within the hole can "attract" the surfaces and pull them away from their correct location at the hole boundary. With this application area in mind, we present a graph-theoretic approach for segmenting multiple surfaces with a shared hole. The overall cost function that is optimized consists of both the costs of the surfaces outside the hole and the cost of boundary of the hole itself. The constraints utilized were appropriately adapted in order to ensure the smoothness of the hole boundary in addition to ensuring the smoothness of the non-overlapping surfaces. By using this approach, a significant improvement was observed over a more traditional two-pass approach in which the surfaces are segmented first (assuming the presence of no hole) followed by segmenting the neural canal opening.
PMID: 25333185 [PubMed - in process]
Robust cortical thickness measurement with LOGISMOS-B.
Med Image Comput Comput Assist Interv. 2014;17(Pt 1):722-30
Authors: Oguz I, Sonka M
Cortical thickness (CT) is an important morphometric measure that has implications for psychiatric and neurologic processes. We propose a novel approach for automatically computing CT in an accurate and robust manner using LOGISMOS-B: Layered Optimal Graph Image Segmentation of Multiple Objects and Surfaces for the Brain. LOGISMOS-B is a cortical surface segmentation method based on LOGISMOS graph segmentation and generalized gradient vector flows. We evaluate our method on two different datasets (n = 83 total). The results show that LOGISMOS-B is more accurate than the popular FreeSurfer (FS) method and provides more reliable thickness measurements across a variety of challenging images. LOGISMOS-B accurately recovers known CT patterns, both across cortical lobes and locally, such as between the banks of the central sulcus, in healthy subjects and MS patients. Manual landmarks indicate a signed surface distance of 0.081 +/- 0.447mm for WM and 0.018 +/- 0.498mm for LOGISMOS-B, compared to 0.263 +/- 0.452mm for WM and -0.167 +/- 0.556mm for GM for FS, highlighting the surface placement accuracy of LOGISMOS-B. Finally, a regresion study shows that LOGISMOS-B provides strong correlation with age and plausible annual thinning rates across the cortex, with locally discerning thinning patterns, in agreement with the literature.
PMID: 25333183 [PubMed - in process]
Incidence of bilateral Marcus Gunn jaw-wink.
Ophthal Plast Reconstr Surg. 2014 May-Jun;30(3):e54-5
Authors: Sobel RK, Allen RC
This case report describes the unusual finding of bilateral Marcus Gunn jaw-wink. Only a few bilateral jaw-wink patients have been published as case reports. The authors dispute this notion as portrayed in the literature that a bilateral wink is a rare entity. A thorough review of prior case series on congenital ptosis and jaw-wink demonstrates that bilateral involvement is more common than previously thought. A supplemental video shows the classic action of lateral pterygoid contraction causing ipsilateral eyelid retraction.
PMID: 23880977 [PubMed - indexed for MEDLINE]