Anatomically Constrained Video-CT Registration via the V-IMLOP Algorithm

Functional endoscopic sinus surgery (FESS) is a surgical procedure used to treat acute cases of sinusitis and other sinus diseases. FESS is fast becoming the preferred choice of treatment due to its minimally invasive nature. However, due to the limited field of view of the endoscope, surgeons rely on navigation systems to guide them within the nasal cavity. State of the art navigation systems report registration accuracy of over 1mm, which is large compared to the size of the nasal airways. We present an anatomically constrained video-CT registration algorithm that incorporates multiple video features. Our algorithm is robust in the presence of outliers. We also test our algorithm on simulated and in-vivo data, and test its accuracy against degrading initializations.Comment: 8 pages, 4 figures, MICCA

Structured light techniques for 3D surface reconstruction in robotic tasks

Robotic tasks such as navigation and path planning can be greatly enhanced by a vision system capable of providing depth perception from fast and accurate 3D surface reconstruction. Focused on robotic welding tasks we present a comparative analysis of a novel mathematical formulation for 3D surface reconstruction and discuss image processing requirements for reliable detection of patterns in the image. Models are presented for a parallel and angled configurations of light source and image sensor. It is shown that the parallel arrangement requires 35\% fewer arithmetic operations to compute a point cloud in 3D being thus more appropriate for real-time applications. Experiments show that the technique is appropriate to scan a variety of surfaces and, in particular, the intended metallic parts for robotic welding tasks

Endoscopic navigation in the absence of CT imaging

Clinical examinations that involve endoscopic exploration of the nasal cavity and sinuses often do not have a reference image to provide structural context to the clinician. In this paper, we present a system for navigation during clinical endoscopic exploration in the absence of computed tomography (CT) scans by making use of shape statistics from past CT scans. Using a deformable registration algorithm along with dense reconstructions from video, we show that we are able to achieve submillimeter registrations in in-vivo clinical data and are able to assign confidence to these registrations using confidence criteria established using simulated data.Comment: 8 pages, 3 figures, MICCAI 201

The role of septal perforators and "myocardial bridging effect" in atherosclerotic plaque distribution in the coronary artery disease

The distribution of atherosclerotic plaque burden in the human coronary arteries is not uniform. Plaques are located mostly in the left anterior descending artery (LAD), then in the right coronary artery (RCA), circumflex branch (LCx) and the left main coronary artery (LM) in a decreasing order of frequency. In the LAD and LCx, plaques tend to cluster within the proximal segment, while in the RCA their distribution is more uniform. Several factors have been involved in this phenomenon, particularly flow patterns in the left and right coronary artery. Nevertheless, it does not explain the difference in lesion frequency between the LAD and the LCx as these are both parts of the left coronary artery. Branching points are considered to be the risk points of atherosclerosis. In the LCx, the number of side branches is lower than in the LAD or RCA and there are no septal perforators with intramuscular courses like in the proximal third of the LAD and the posterior descending artery (PDA). We hypothesized that septal branches generate disturbed flow in the LAD and PDA in a similar fashion to the myocardial bridge (myocardial bridging effect). This coronary architecture determines the non-uniform plaque distribution in coronary arteries and LAD predisposition to plaque formation

Znaczenie naprężeń ścinających i rola numerycznej mechaniki płynów w badaniach nad patomechanizmem miażdżycy

Na powierzchni ściany naczyń działają dwie siły biomechaniczne: naprężenie rozciągające i - ważniejsze z punktu widzenia patomechanizmu miażdżycy - naprężenie ścinające. W tętnicach fizjologiczna wartość naprężenia ścinającego zawiera się w przedziale wartości od około 15 dyn/cm2 do 70 dyn/cm2. Takie naprężenia wywierają efekt ochronny na śródbłonek naczyniowy. Mimo że czynniki ryzyka mają charakter ogólnoustrojowy, to blaszki miażdżycowe tworzą się w ściśle określonych miejscach, którymi są ściany boczne bifurkacji, okolice odejścia gałęzi bocznych i krzywizny wewnętrzne naczyń. W miejscach tych śródbłonek jest narażony na działanie małych i oscylacyjnych naprężeń ścinających będących konsekwencją formowania się złożonych przepływów wtórnych. Małe i oscylacyjne naprężenia ścinające, za pośrednictwem zjawiska mechanotransdukcji, prowadzą do dysfunkcji śródbłonka, który przybiera proaterogenny fenotyp. Zjawisko to odgrywa ważną rolę w powstawaniu zmian miażdżycowych. Coraz doskonalsze metody obrazowania, uzyskiwania pomiarów prędkości przepływu krwi umożliwiają zastosowanie numerycznej mechaniki płynów do modelowania rozkładu naprężeń ścinających w tętnicach wieńcowych. W ten sposób obraz 3D zostaje uzupełniony o czwarty wymiar, jakim jest rozkład naprężeń i ciśnień działających na ścianę naczyń (4D). (Folia Cardiologica Excerpta 2012; 7, 2: 95-100

Intelligent frame selection for anatomic reconstruction from endoscopic video

Using endoscopic video, it is possible to perform 3D re-construction of the anatomy using the well known epipolar constraint between matched feature points. Through this constraint, it is possible to recover the translation and rota-tion between camera positions and thus reconstruct the 3D anatomy by triangulation. However, these motion estimates are not stable for small camera motions. In this work, we propose a covariance estimation scheme to select pairs of frames which give rise to stable motion estimates, i.e. min-imal variance with respect to pixel match error. We param-eterize the essential matrix using a minimal 5 parameter representation and estimate motion covariance based upon the estimated feature match variance. The proposed algo-rithm is applied to endoscopic video sequences recorded in porcine sinus passages in order to extract stable motion es-timates. 1

Optical techniques for 3D surface reconstruction in computer-assisted laparoscopic surgery

One of the main challenges for computer-assisted surgery (CAS) is to determine the intra-opera- tive morphology and motion of soft-tissues. This information is prerequisite to the registration of multi-modal patient-specific data for enhancing the surgeon’s navigation capabilites by observ- ing beyond exposed tissue surfaces and for providing intelligent control of robotic-assisted in- struments. In minimally invasive surgery (MIS), optical techniques are an increasingly attractive approach for in vivo 3D reconstruction of the soft-tissue surface geometry. This paper reviews the state-of-the-art methods for optical intra-operative 3D reconstruction in laparoscopic surgery and discusses the technical challenges and future perspectives towards clinical translation. With the recent paradigm shift of surgical practice towards MIS and new developments in 3D opti- cal imaging, this is a timely discussion about technologies that could facilitate complex CAS procedures in dynamic and deformable anatomical regions

K63-linked ubiquitin chains as a specific signal for protein sorting into the multivesicular body pathway

A growing number of yeast and mammalian plasma membrane proteins are reported to be modified with K63-linked ubiquitin (Ub) chains. However, the relative importance of this modification versus monoubiquitylation in endocytosis, Golgi to endosome traffic, and sorting into the multivesicular body (MVB) pathway remains unclear. In this study, we show that K63-linked ubiquitylation of the Gap1 permease is essential for its entry into the MVB pathway. Carboxypeptidase S also requires modification with a K63-Ub chain for correct MVB sorting. In contrast, monoubiquitylation of a single target lysine of Gap1 is a sufficient signal for its internalization from the cell surface, and Golgi to endosome transport of the permease requires neither its ubiquitylation nor the Ub-binding GAT (Gga and Tom1) domain of Gga (Golgi localizing, gamma-ear containing, ARF binding) adapter proteins, the latter being crucial for subsequent MVB sorting of the permease. Our data reveal that K63-linked Ub chains act as a specific signal for MVB sorting, providing further insight into the Ub code of membrane protein trafficking

Targeting of Sna3p to the Endosomal Pathway Depends on Its Interaction with Rsp5p and Multivesicular Body Sorting on Its Ubiquitylation

Rsp5p is an ubiquitin (Ub)-protein ligase of the Nedd4 family that carries WW domains involved in interaction with PPXY-containing proteins. It plays a key role at several stages of intracellular trafficking, such as Ub-mediated internalization of endocytic cargoes and Ub-mediated sorting of membrane proteins to internal vesicles of multivesicular bodies (MVBs), a process that is crucial for their subsequent targeting to the vacuolar lumen. Sna3p is a membrane protein previously described as an Ub-independent MVB cargo, but proteomic studies have since shown it to be an ubiquitylated protein. Sna3p carries a PPXY motif. We observed that this motif mediates its interaction with Rsp5p WW domains. Mutation of either the Sna3p PPXY motif or the Rsp5p WW3 domain or reduction in the amounts of Rsp5 results in the mistargeting of Sna3p to multiple mobile vesicles and prevents its sorting to the endosomal pathway. This sorting defect appears to occur prior to the defect displayed in rsp5 mutants by other MVB cargoes, which are correctly sorted to the endosomal pathway but missorted to the vacuolar membrane instead of the vacuolar lumen. Sna3p is polyubiquitylated on one target lysine, and a mutant Sna3p lacking its target lysine displays defective MVB sorting. Sna3p undergoes Rsp5-dependent polyubiquitylation, with K63-linked Ub chains