Due to the intricate relationship between the pelvic organs and vital structures, such as vessels and nerves, pelvic anatomy is often considered to be complex to comprehend. In oncological pelvic surgery, a trade-off has to be made between complete tumor resection and preserving function by preventing damage to the nerves. Damage to the autonomic nerves causes undesirable post-operative side-effects such as fecal and urinal incontinence, as well as sexual dysfunction in up to 80 percent of the cases. Since these autonomic nerves are not visible in pre-operative MRI scans or during surgery, avoiding nerve damage during such
a surgical procedure becomes challenging. In this work, we present visualization methods to represent context, target, and risk structures for surgical planning. We employ distance-based and occlusion management techniques in an atlas-based surgical planning tool for oncological pelvic surgery. Patient-specific pre-operative MRI scans are registered to an atlas model that includes nerve information. Through several interactive linked views, the spatial relationships and distances between the organs, tumor and risk zones are visualized to improve understanding, while avoiding occlusion. In this way, the surgeon can examine surgically relevant structures and plan the procedure before going into the operating theater, thus raising awareness of the autonomic nerve zone regions and potentially reducing post-operative complications. Furthermore, we present the results of a domain expert evaluation with surgical oncologists that demonstrates the advantages of our approach.@en

This thesis deals with visualizing anatomical data for medical education and surgical planning purposes. To this end, we have developed a detailed virtual atlas, the Virtual Surgical Pelvis (VSP),which unifies surgically relevant knowledge on pelvic anatomy. We provide methods to share the knowledge contained in the VSP for educational purposes, and to visualize the VSP in the context of individual patients for pre-operative planning purposes. Chapter 2 deals with a representation developed to unify spatial and non-spatial anatomical knowledge. Via this representation, it is possible to store, access and visualize these heterogeneous datasets through a shared coordinate system. This allows us to construct the VSP atlas, a process which we describe in detail in Chapter 3, where we also detail the application potential of the VSP. We present several examples of the VSP mapped to clinical pre-operative MRI scans, as examples of how the VSP can be used to enrich clinical data with surgically relevant information that is not available from the scans themselves. To share the VSP for educational purposes, we present an online tool, the Online Anatomical Human (OAH) in Chapter 4. OAH runs directly in the browser and can be used to explore the complex relation between 2D and 3D anatomy. Furthermore, annotations can be added directly on the 3D structures for quizzing purposes, or to enrich the VSP further with annotations performed by experts. The OAH was successfully deployed in aMassiveOpenOnline Course (MOOC), where thousands of studentsworldwide used the application to study pelvic anatomy. While the VSP is based on multiple datasets, it does not include all potential topological anatomical variations in branching structures such as vessels and nerves. Illustrations and text are traditionally used by medical specialists to study these variations, but it is difficult to compare complex variations in such illustrations. Therefore, in Chapter 5 we present an interactive visualization application for anatomical variations, which allows the user to compare and explore variations of branching structures interactively for educational purposes. With methods inspired by graph theory, users can intuitively select groups of variations, based on a similarity measure, and compare local differences. In Chapter 6, we present a state-of-the-art report on multimodal medical visualization. We describe the basics of medical image acquisition, and the clinical workflow for dealing with such data. We discuss suitable rendering and visualization techniques appropriate for rendering multiple modalities. The core contribution of this work is a taxonomy based on the multimodal medical visualization applications so far, the visualization techniques they employ, and the medical domain context. Additionally, we provide an outlook on open problems and potential future research directions. To make the VSP patient-specific and to enrich the VSP with more datasets, registration is needed. Unfortunately, current registration software is often difficult to use for non-medical-imaging-experts. In Chapter 7 we present a new registration application, RegistrationShop, that allows user to register 3D medical image datasets based on 3D visualizations and simple interactive transformation tools. Based on real-time visual feedback via comparative visualization techniques, users can inspect the current registration result and iteratively improve the alignment. Besides basic interactive transformation tools, we propose a novel way of placing corresponding landmark-pairs in 3D volumes. After combining the VSP atlas with patient-specific pre-operative MRI scans, we visualize the results in an interactive application for surgical planning aimed at pelvic oncological procedures, entitled PelVis, which is described in Chapter 8. We present visualization methods to represent context, target, and risk structures for surgical planning of the Total Mesorectal Excision (TME) procedure. We employ distance-based and occlusion management techniques to represent the patient-specific pathology and anatomy. Furthermore, we visualize the confidence in the registration outcome in relation to the distance of the target structure to the risk zones. The research described in this thesis was supported by the Dutch Technology Foundation STW via project 10903: “High-definition Atlas-based surgical planning for Pelvic Surgery”.@en

OBJECTIVE:
Radical hysterectomy with pelvic lymphadenectomy (RHL) is the preferred treatment for early-stage cervical cancer. Although oncological outcome is good with regard to recurrence and survival rates, it is well known that RHL might result in postoperative bladder impairments due to autonomic nerve disruption. The pelvic autonomic network has been extensively studied, but the anatomy of nerve fibers branching off the inferior hypogastric plexus to innervate the bladder is less known. Besides, the pathogenesis of bladder dysfunction after RHL is multifactorial but remains unclear. We studied the 3-dimensional anatomy and neuroanatomical composition of the vesical plexus and describe implications for RHL.
MATERIALS AND METHODS:
Six female adult cadaveric pelvises were macroscopically dissected. Additionally, a series of 10 female fetal pelvises (embryonic age, 10-22 weeks) was studied. Paraffin-embedded blocks were transversely sliced in 8-μm sections. (Immuno) histological analysis was performed with hematoxylin and eosin, azan, and antibodies against S-100 (Schwann cells), tyrosine hydroxylase (postganglionic sympathetic fibers), and vasoactive intestinal peptide (postganglionic parasympathetic fibers). The results were 3-dimensionally visualized.
RESULTS:
The vesical plexus formed a group of nerve fibers branching off the ventral part of the inferior hypogastric plexus to innervate the bladder. In all adult and fetal specimens, the vesical plexus was closely related to the distal ureter and located in both the superficial and deep layers of the vesicouterine ligament. Efferent nerve fibers belonging to the vesical plexus predominantly expressed tyrosine hydroxylase and little vasoactive intestinal peptide.
CONCLUSIONS:
The vesical plexus is located in both layers of the vesicouterine ligament and has a very close relationship with the distal ureter. Complete mobilization of the ureter in RHL might cause bladder dysfunction due to sympathetic and parasympathetic denervation. Hence, the distal ureter should be regarded as a risk zone in which the vesical plexus can be damaged.
@en

Anatomical variations are naturally-occurring deviations from typical human anatomy. While these variations are considered normal and non-pathological, they are still of interest in clinical practice for medical specialists such as radiologists and transplantation surgeons. The complex variations in branching structures, for instance in arteries or nerves, are currently visualized side-by-side in illustrations or expressed using plain text in medical publications. In this work, we present a novel way of visualizing anatomical variations in complex branching structures for educational purposes: VarVis. VarVis consists of several linked views that reveal global and local similarities and differences in the variations. We propose a novel graph representation to provide an overview of the topological changes. Our solution involves a topological similarity measure, which allows the user to select variations at a global level based on their degree of similarity. After a selection is made, local topological differences can be interactively explored using illustrations and topology graphs. We also incorporate additional information regarding the probability of the various cases. Our solution has several advantages over traditional approaches, which we demonstrate in an evaluation.@en

The Online Anatomical Human (OAH) is a web-based viewer for studying anatomy. It is based on real human anatomy and incorporates medical image data in linked 2D and 3D views that students can freely interact with. Our application is the only to support 2D and 3D views based on real medical imaging data. The main goal of this anatomical online resource is to serve as an educational platform available to anyone with access to a modern web browser. Users can annotate regions, add comments, and provide hyperlinks to additional media. By making our work accessible to medical experts, we can ensure an increasing amount of information, leading to an ever-growing gain in educational value. The OAH will be used in an upcoming Massive Open Online Course (MOOC) to teach anatomy of the pelvis and will be made available to students worldwide via the web. @en

Medical visualization papers often deal with data that is interpreted by medical domain experts in a research or clinical context. Since visualizations are by definition designed to be interpreted by a human observer, often an evaluation is performed to confirm the utility of a presented method. The exact type of evaluation required is not always clear, especially to new researchers. With this paper, we hope to clarify the different types of evaluation methods that exist and provide practical guidelines to choose the most suitable evaluation method to increase the value of the work.@en

Background: The surgical anatomy of the pelvis is highly complex. In case of rectal cancer the surgeon is challenged to perform a total mesorectal excision (TME) warranting complete removal of the tumor and preservation of the autonomic nerves. However, incomplete TME specimens and surgical damage to the nerves are still part of clinical reality. A highly-detailed 3D pelvic model would be an excellent tool to increase anatomical knowledge of the surgical anatomy of the pelvis. Visible Human Datasets (VHDs) are often used to create a 3D model, but they lack anatomical detail such as autonomic nerves and fasciae. Immunohistochemistry is an ideal method to study those key surgical structures at microscopic level. Recently, the Unified Anatomical Human (UAH) has been developed. UAH integrates heterogeneous anatomical data and will allow registration of patient-specific diagnostic images. In this study, we describe the development of The Virtual Surgical Pelvis (VSP) and its potential clinical value in anatomical education and surgical simulation.Material and methods: We selected 910 slices from a VHD that comprised the entire pelvis. All surgically relevant anatomical structures were manually segmented using Amira® software and three-dimensionally reconstructed using the UAH. The Online Anatomical Human (OAH), an online web-viewer, was developed as well. Paraffin embedded mega blocks of 1 female cadaveric pelvic exenteration specimen were sliced in transverse sections of 5 μm. A series was stained with Hematoxylin & Eosin and Masson’s Trichome and selected sections were immunohistochemically stained with S100, a pan-neuron marker. The autonomic nerves and fasciae were manually segmented in Amira® software, three-dimensionally reconstructed and integrated using the UAH.Results: Currently, the VSP presents most of the essential surgical anatomy of the pelvis, including the levator ani muscle and pudendal nerve, and can be interactively visualized in the UAH and OAH. Microscopic analysis of the female cadaveric specimen reveals the organization of autonomic nerves and fasciae in relation to pelvic organs.Conclusion: The VSP showing the complex pelvic anatomy is a potentially excellent tool for anatomical education. Registration of the VSP to patient-specific diagnostic images allows visualization of key surgical structures such as autonomic nerves and fasciae in relation to pelvic viscera. This makes surgical simulation a nearby future goal for all pelvic surgeons. No conflict of interest.@en