Author

Robert Curtin

Date on Master's Thesis/Doctoral Dissertation

8-2014

Document Type

Master's Thesis

Degree Name

M. Eng.

Department

Electrical and Computer Engineering

Committee Chair

Farag, Aly A.

Committee Member

Alphenaar, Bruce

Committee Member

Richards, Chris

Abstract

Colorectal cancer is one of the leading causes of death in the world. Colonoscopy, the traditional procedure for detecting colorectal cancer, is very effective. It does have downsides, however - it is invasive, uncomfortable for the patient, and not available to some patients with certain conditions. Virtual colonoscopy has been developed in order to address these issues. A virtual colonoscopy (VC) is a non-invasive method for performing a colonoscopy by using medical imaging data to create a virtual representation of the colon. Previous virtual colonoscopy methods include fly-through, fly-over, flattening, and the unfolded cube method. Fly-through moves the camera through the inside of the colon, following a centerline from the length of the colon. Fly-over splits the colon into halves longitudinally, and flies a camera over each half. Flattening reduces the 3D colon model to a 2D image. The unfolded cube method flies a set of cameras along the centerline as in flythrough, but where flythrough had one camera looking along the centerline, the unfolded cube method presents views from six cameras. The six camera views are positioned in the pattern of an unfolded cube, which gives rise to the method’s name. This thesis will present a new method called one-sided transparency (OST). This is a method for visualizing virtual objects so that the interior surfaces can be viewed from the outside. OST has numerous improvements over existing VC methods, particularly when combined with fly-over methods. However, this thesis will also demonstrate that OST is not limited to fly-over nor even to VC, as it has applications in multiple fields. For quantitative evaluation, this thesis focused on comparing specific scenarios that OST excels in visualizing. Fly-through navigation has difficulties with polyps between haustral folds, and prior fly-over work had visual artifacts that degraded the quality of the final visualization. These and other specific cases are visualized using OST in order to highlight the power of this new technique. Additionally, the previous FO method had some significant drawbacks that are solved by the application of OST. These problems and their origins will be addressed, along with the way that OST solves them. This thesis will also explore potential applications for OST outside of VC. This will include a more general visualization of tubular objects. It will be shown that OST has the ability to highlight structural issues and deformities such as cracks and bumps. This has potential applications in medical fields outside of VC as well as in structural engineering. This will demonstrate OST’s usefulness as a general technique, even outside the context of VC. Finally, this thesis will present results regarding OST for VC. It will show that OST presents several advantages over previous VC methods. OST allows easier viewing of polyps in difficult locations and offers a more complete view of the colon. OST has a number of advantages over the existing fly-over method, including faster time-to-viewing, less sensitivity to centerline error, and improved accuracy in the separation of halves.

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