Patrick Saalfeld

Comparison of gesture and conventional interaction techniques for interventional neuroradiology

PurposeInteraction with radiological image data and volume renderings within a sterile environment is a challenging task. Clinically established methods such as joystick control and task delegation can be time-consuming and error-prone and interrupt the workflow. New touchless input modalities may have the potential to overcome these limitations, but their value compared to established methods is unclear.MethodsWe present a comparative evaluation to analyze the value of two gesture input modalities (Myo Gesture Control Armband and Leap Motion Controller) versus two clinically established methods (task delegation and joystick control). A user study was conducted with ten experienced radiologists by simulating a diagnostic neuroradiological vascular treatment with two frequently used interaction tasks in an experimental operating room. The input modalities were assessed using task completion time, perceived task difficulty, and subjective workload.ResultsOverall, the clinically established method of task delegation performed best under the study conditions. In general, gesture control failed to exceed the clinical input approach. However, the Myo Gesture Control Armband showed a potential for simple image selection task.ConclusionNovel input modalities have the potential to take over single tasks more efficiently than clinically established methods. The results of our user study show the relevance of task characteristics such as task complexity on performance with specific input modalities. Accordingly, future work should consider task characteristics to provide a useful gesture interface for a specific use case instead of an all-in-one solution.

Comparative Evaluation of Feature Line Techniques for Shape Depiction

This paper presents a qualitative evaluation of feature line techniques on various surfaces. We introduce the most commonly used feature lines and compare them. The techniques were analyzed with respect to the degree of realism in comparison with a shaded image with respect to the aesthetic impression they create. First, a pilot study with 20 participants was conducted to make an inquiry about their behavior and the duration. Based on the result of the pilot study, the final evaluation was carried out with 129 participants. We evaluate and interpret the trial results by using the Schulze method and give recommendations for which kind of surface, which feature line technique is most appropriate.

Sketching 2D Vessels and Vascular Diseases with Integrated Blood Flow

In this paper, we present a sketch-based interface, which allows medical doctors to illustrate different vascular diseases and treatment methods as well as fluid behavior. With this sketching interface, we provide the physician with an effective tool to illustrate different medical cases, which is important in the complex field of vascular diseases with respect to patient education. We use techniques from sketch-based interfaces and GPU-based computational fluid dynamics by considering usability aspects. We provide a concept and a prototypical implementation whose usability is tested with quantitative and qualitative methods. Additionally, we interviewed a physician to assess the benefits of the tool with respect to patient education.

The FAUST framework: Free-form annotations on unfolding vascular structures for treatment planning

Abstract For complex interventions, such as stenting of a cerebral aneurysm, treatment planning is mandatory. Sketching can support the physician as it involves an active involvement with complex spatial relations and bears a great potential to improve communication. These sketches are employed as direct annotation on 2D medical image data and print outs, respectively. Annotating 3D planning models is more difficult due to possible occlusions of the complex spatial anatomy of vascular structures. Furthermore, the annotations should adapt accordingly to view changes and deforming structures. Therefore, we developed the FAUST framework, which allows creating 3D annotations by freely sketching in the 3D environment. Additionally to generic annotations, the physician is supported to create the most common treatment options with sketching single strokes only. We allow an interactive unfolding of vascular structures with adapting annotations to still convey their meta information. Our framework is realized on the zSpace, which combines a semi-immersive stereoscopic display and a stylus with ray-based interaction techniques. We conducted a user study with computer scientists, carried out a demo session with a neuroradiologist and assessed the performance. The user study revealed a positive rating of the interaction techniques and a high sense of presence. The neuroradiologist stated that our framework can support treatment planning and leads to a better understanding of anatomical structures. Our performance evaluation showed that our sketching approach is usable in real-time with a large number of annotations. Furthermore, our approach can be adapted to a wider range of applications including medical documentation.

Semi-immersive 3D sketching of vascular structures for medical education

We present a semi-immersive 3D User Interface to sketch complex vascular structures and vessel pathologies by drawing centerlines in 3D. Our framework comprises on-the-fly reconstruction of the corresponding vessel surface and subsequent local surface compression and expansion. Additionally, we allow the enrichment with an illustrative, plausible blood flow visualization. Our framework is designed for medical educators and students to support anatomy and pathology education. Anatomy educators can realize the step-by-step process of creating and explaining complex spatial relationships of interlinked vascular structures and blood flow behavior. Students can view this process and explore the created structures, which helps them in reproducing and memorizing them. To create a surface model based on the sketched centerlines, we employ implicit surfaces. This allows for easy adding, editing, and removing vessel branches and achieve continuous surfaces with smooth transitions at branchings. The blood flow can be interactively added and is realized with a topology-aware particle simulation. We qualitatively evaluated our framework and demonstrate the applicability and usability of our approach.

How to evaluate medical visualizations on the example of 3D aneurysm surfaces

For the evaluation of medical visualizations, a ground truth is often missing. Therefore, the evaluation of medical visualizations is often restricted to qualitative comparisons w.r.t user preferences but neglects more objective measures such as accuracies or task completion times. In this work, we provide a pipeline with statistical tests for the evaluation of the user performance within an experimental setup. We demonstrate the adaption of the pipeline for the specific example of cerebral aneurysm surface visualization. Therefore, we developed three visualization techniques to compare the aneurysm volumes. Then, we present a single-factor, within-subject user study, which allows for the evaluation of these visualization techniques as well as the identification of the most suitable one. The evaluation includes a qualitative as well as a comprehensive quantitative analysis to determine statistically significant differences. As a result, a color-coded map surface view is identified as best suited to depict the aneurysm volume changes. The presentation of the different stages of the evaluation pipeline allows for an easy adaption to other application areas of medical visualization. As a result, we provide orientation to enrich qualitative evaluations by the presented quantitative analyses.

A Sketch-Based Interface for 2D Illustration of Vascular Structures, Diseases, and Treatment Options with Real-Time Blood Flow

We present a sketching interface, which enables physicians to illustrate various vascular structures, diseases, and treatment options with integrated blood flow. This sketch-based interface provides medical doctors with an effective tool to illustrate different medical scenarios and support patient education. This work integrates methods from sketch-based interfaces and GPU-supported computational fluid dynamics. The usability of the prototype was assessed qualitatively and quantitatively. Additionally, we performed a structured interview with a physician to evaluate the benefits with respect to patient education. The results of the evaluation confirmed the usability of the prototype as well as the usefulness to support physicians during the process of patient education.

Illustrative Visualization of Endoscopic Views

This paper deals with the application of illustrative line renderings on endoscopic views. We examine different line drawing concepts and assess the ability to represent interior branches as well as specific anatomic features. Furthermore, we conduct a qualitative evaluation to rate the results of different illustrative visualization methods. We evaluate how well branches are depicted according to a shaded object and which of the technique is rated as the most expressive. We use different anatomical surfaces which were derived from clinical image data. Moreover, we identify the limitations of the illustrative visualization and derive requirements for the application.

A survey of virtual human anatomy education systems

Abstract This survey provides an overview of visualization and interaction techniques developed for anatomy education. Besides individual techniques, the integration into virtual anatomy systems is considered. Web-based systems play a crucial role to enable learning independently at any time and space. We consider the educational background, the underlying data, the model generation as well as the incorporation of textual components, such as labels and explanations. Finally, stereoscopic devices and first immersive VR solutions are discussed. The survey comprises also evaluation studies that analyze the learning effectiveness.

Guidelines for Quantitative Evaluation of Medical Visualizations on the Example of 3D Aneurysm Surface Comparisons

Medical visualizations are highly adapted to a specific medical application scenario. Therefore, many researchers conduct qualitative evaluations with a low number of physicians or medical experts to assess the benefits of their visualization technique. Although this type of research has advantages, it is difficult to reproduce and can be subjectively biased. This makes it problematic to quantify the benefits of a new visualization technique. Quantitative evaluation can objectify research and help bringing new visualization techniques into clinical practice. To support researchers, we present guidelines to quantitatively evaluate medical visualizations, considering specific characteristics and difficulties. We demonstrate the adaptation of these guidelines on the example of comparative aneurysm surface visualizations. We developed three visualization techniques to compare aneurysm volumes. The visualization techniques depict two similar, but not identical aneurysm surface meshes. In a user study with 34 participants and five aneurysm data sets, we assessed objective measures (accuracy and required time) and subjective ratings (suitability and likeability). The provided guidelines and presentation of different stages of the evaluation allow for an easy adaptation to other application areas of medical visualization.