Timothy D. Wilson

Explorable three-dimensional digital model of the female pelvis, pelvic contents, and perineum for anatomical education.

The anatomy of the pelvis is complex, multilayered, and its three‐dimensional organization is conceptually difficult for students to grasp. The aim of this project was to create an explorable and projectable stereoscopic, three‐dimensional (3D) model of the female pelvis and pelvic contents for anatomical education. The model was created using cryosection images obtained from the Visible Human Project, in conjunction with a general‐purpose three‐dimensional segmentation and surface‐rendering program. Anatomical areas of interest were identified and labeled on consecutive images. Each 2D slice was reassembled, forming a three‐dimensional model. The model includes the pelvic girdle, organs of the pelvic cavity, surrounding musculature, the perineum, neurovascular structures, and the peritoneum. Each structure can be controlled separately (e.g. added, subtracted, made transparent) to reveal organization and/or relationships between structures. The model can be manipulated and/or projected stereoscopically to visualize structures and relationships from different angles with excellent spatial perception. Because of its ease of use and versatility, we expect this model may provide a powerful teaching tool for learning in the classroom or in the laboratory. Anat Sci Educ.

A Head in Virtual Reality: Development of A Dynamic Head and Neck Model

Advances in computer and interface technologies have made it possible to create three‐dimensional (3D) computerized models of anatomical structures for visualization, manipulation, and interaction in a virtual 3D environment. In the past few decades, a multitude of digital models have been developed to facilitate complex spatial learning of the human body. However, there is limited empirical evidence to guide the development and integration of effective computer models for teaching and learning. The purpose of this article is to describe the development of a dynamic head and neck model with flexible displays (2D, 3D, and stereoscopic 3D) and interactive control features that can be later used to design and test the efficacy of computer models as a means of improving student learning. The model was created using computer tomography scans of a human cadaver. Anatomical structures captured on the scans were segmented into discreet areas, and then reconstructed in three‐dimensions using specialized software. The final model consists of 70 distinct anatomical structures that can be displayed in 2D, 3D, or stereoscopic 3D. In 3D mode, a mouse can be used to actively and continuously interact with the model by manipulating viewer orientation, altering surface transparency, superimposing 2D scans with 3D reconstructions, removing or adding structures sequentially, and customizing animated scenes to show complex anatomical pathways or relationships. Anat Sci Educ 2: 294–301, 2009.

Vestibular inputs elicit patterned changes in limb blood flow in conscious cats

Previous experiments have demonstrated that the vestibular system contributes to regulating sympathetic nervous system activity, particularly the discharges of vasoconstrictor fibres. In the present study, we examined the physiological significance of vestibulosympathetic responses by comparing blood flow and vascular resistance in the forelimb and hindlimb during head‐up tilt from the prone position before and after the removal of vestibular inputs through a bilateral vestibular neurectomy. Experiments were performed on conscious cats that were trained to remain sedentary on a tilt table during rotations up to 60 deg in amplitude. Blood flow through the femoral and brachial arteries was recorded during whole‐body tilt using perivascular probes; blood pressure was recorded using a telemetry system and vascular resistance was calculated from blood pressure and blood flow measurements. In vestibular‐intact animals, 60 deg head‐up tilt produced ∼20% decrease in femoral blood flow and ∼37% increase in femoral vascular resistance relative to baseline levels before tilt; similar effects were also observed for the brachial artery (∼25% decrease in blood flow and ∼38% increase in resistance). Following the removal of vestibular inputs, brachial blood flow and vascular resistance during head‐up tilt were almost unchanged. In contrast, femoral vascular resistance increased only ∼6% from baseline during 60 deg head‐up rotation delivered in the first week after elimination of vestibular signals and ∼16% in the subsequent 3‐week period (as opposed to the ∼37% increase in resistance that occurred before lesion). These data demonstrate that vestibular inputs associated with postural alterations elicit regionally specific increases in vascular resistance that direct blood flow away from the region of the body where blood pooling may occur. Thus, the data support the hypothesis that vestibular influences on the cardiovascular system serve to protect against the occurrence of orthostatic hypotension.

Virtual Cerebral Ventricular System: An MR-Based Three-Dimensional Computer Model.

The inherent spatial complexity of the human cerebral ventricular system, coupled with its deep position within the brain, poses a problem for conceptualizing its anatomy. Cadaveric dissection, while considered the gold standard of anatomical learning, may be inadequate for learning the anatomy of the cerebral ventricular system; even with intricate dissection, ventricular structures remain difficult to observe. Three‐dimensional (3D) computer reconstruction of the ventricular system offers a solution to this problem. This study aims to create an accurate 3D computer reconstruction of the ventricular system with surrounding structures, including the brain and cerebellum, using commercially available 3D rendering software. Magnetic resonance imaging (MRI) scans of a male cadaver were segmented using both semiautomatic and manual tools. Segmentation involves separating voxels of different grayscale values to highlight specific neural structures. User controls enable adding or removing of structures, altering their opacity, and making cross‐sectional slices through the model to highlight inner structures. Complex physiologic concepts, such as the flow of cerebrospinal fluid, are also shown using the 3D model of the ventricular system through a video animation. The model can be projected stereoscopically, to increase depth perception and to emphasize spatial relationships between anatomical structures. This model is suited for both self‐directed learning and classroom teaching of the 3D anatomical structure and spatial orientation of the ventricles, their connections, and their relation to adjacent neural and skeletal structures. Anat Sci Educ.

Circulating norepinephrine and cerebrovascular control in conscious humans

Background:  Cerebral vasoconstriction without concurrent changes in systemic arterial blood pressure has been observed in both normal individuals and those with idiopathic orthostatic intolerance following several minutes of postural stress when circulating catecholamines are elevated. Therefore, we tested the hypothesis that α‐adrenergic activation with and without elevated circulating norepinephrine (NE) directly affects cerebrovascular tone in healthy individuals.

Three-dimensional Educational Computer Model of the Larynx: Voicing a New Direction

OBJECTIVES To create a 3-dimensional (3D) educational computer model of the larynx, to assess the feasibility of this learning module on a Web-based platform, and to obtain student feedback on the module. DESIGN Male and female adult cadaveric necks were scanned with microcomputed tomographic and magnetic resonance imaging scanners. Key structures were identified on each slice of the computed tomogram and/or magnetic resonance image and analyzed with a segmentation software package. Then, the images were exported into Microsoft Powerpoint. Visual text and audio commentary were added. Real cases of a childs larynx, an adult with a tracheostomy, and a patient with laryngeal carcinoma were included. The computer module was launched on a password-protected, Web-based platform. PARTICIPANTS Fifty-eight first-year medical students (38% male; mean [SD] age, 23 [1.8] years) were invited to evaluate the module and to complete a survey. RESULTS Most students thought that the 3D computer module was effective (60%), clear (66%), and user friendly (72%); most students (81%) thought that it was easier to understand laryngeal anatomy when they could visualize it in 3D; and most students (83%) said that they would like lectures better if they were supplemented with 3D computer modules. CONCLUSION A 3D educational computer model of the larynx has been successfully created and warmly received by medical students.

Application of Stereoscopic Visualization on Surgical Skill Acquisition in Novices

OBJECTIVE The use of stereoscopic imaging can provide additional depth cues that may increase trainee performance on surgical tasks, but it has yet to be evaluated using a validated surgical skill system. This study examines the influence of monoscopic vs stereoscopic visualization in novice trainees performing the McGill Inanimate System for Training and Evaluation of Laparoscopic Skill (MISTELS) tasks, a validated laparoscopic skill-evaluation system, predicting a difference in performance based on visualization modality. DESIGN A total of 31 first- and second-year medical students at the University of Western Ontario were selected, each performed the MISTELS battery of tasks (circle cutting, peg transfer, ligated loop Placement, intracorporeal knot tying, and extracorporeal knot tying) using either monoscopic or stereoscopic visualization displays. Performance was evaluated in accordance with the MISTELS protocol. Participant visual spatial ability and manual dexterity skills were also analyzed and compared with performance. p values less than 0.05 were considered significant. RESULTS For ligated loop placement, extracorporeal knot tying, and intracorporeal knot tying, no significant difference was found between monoscopic and stereoscopic visualization on task performance (p > 0.05). Monoscopic visualization was shown to produce significantly better performance in the peg transfer task alone (p = 0.001). Qualitatively, 57.1% of participants believed their performance was aided by stereoscopic visualization and 68.8% believed that future learners would benefit from its implementation into surgical education. Most participants rated the peg transfer task to be the least difficult task (60%) and rated the intracorporeal knot-tying task to be the most difficult (65.9%). CONCLUSIONS These results suggest that the intrinsic difficulty of the MISTELS tasks may exceed a novice users skill. No benefit with additional 3-dimensional cues in naïve surgical trainees was found. Additional visual cues in stereoscopic visualization may only serve to increase cognitive load and potentially decrease skill acquisition and learning.

Development of a computer-assisted cranial nerve simulation from the visible human dataset

Advancements in technology and personal computing have allowed for the development of novel teaching modalities such as online web‐based modules. These modules are currently being incorporated into medical curricula and, in some paradigms, have been shown to be superior to classroom instruction. We believe that these modules have the potential of significantly enriching anatomy education by helping students better appreciate spatial relationships, especially in areas of the body with greater anatomical complexity. Our objective was to develop an online module designed to teach the anatomy and function of the cranial nerves. A three‐dimensional model of the skull, brainstem, and thalamus were reconstructed using data from the Visible Human Project and Amira®. The paths of the cranial nerves were overlaid onto this 3D reconstruction. Videos depicting these paths were then rendered using a “roller coaster‐styled” camera approach. Interactive elements adding textual information and user control were inserted into the video using Adobe Creative Suite® 4, and finally, the module was exported as an Adobe Flash movie to be viewable on Internet browsers. Fourteen Flash‐based modules were created in total. The primary user interface comprises a website encoded in HTML/CSS and contains links to each of the 14 Flash modules as well as a user tutorial. Anat Sci Educ 4: 92–97, 2011.

Head position modifies cerebrovascular response to orthostatic stress

Previous experiments have shown that the vestibular system participates in cardiovascular control. However, the effects of vestibular activation on cerebrovascular regulation are not known. Therefore, the present experiment tested the hypothesis that specific vestibular activations may be beneficial to cerebral circulation during simulated orthostatic stress. Middle cerebral artery blood flow velocity (CBV; Doppler ultrasound) was measured to examine the effects of head-down neck flexion (HDNF) compared to head-down neck extension (HDNE) with and without lower body negative pressure (LBNP; -40 mmHg) (n=9). The change in CBV (DeltaCBV) during HDNF and HDNE were not different during baseline conditions, however, during LBNP, DeltaCBV was greater in HDNE compared to HDNF (-5.5+/-3.2 cm/s, -11+/-4.6%) vs. (-0.7+/-1.0 cm/s, -1.9+/-1.9%), respectively (P<0.05). Concomitantly, the change in cerebrovascular resistance (DeltaCVR) between rest and LBNP was also greater during HDNE (0.48+/-0.08 mmHg/cm per s, 42.8+/-10.8%) compared with HDNF (0.26+/-0.05 mmHg/cm per s, 22+/-4.1%) (P<0.05). P(ET)CO(2) was greater in HDNE (45+/-2 mmHg) compared to HDNF (42+/-2 mmHg; P<0.05) during LBNP. These results suggest that the vestibular system may affect cerebrovascular tone during simulated postural stress by either constriction or dilation, depending on the vestibular stimulus.

Visuospatial anatomy comprehension: The role of spatial visualization ability and problem-solving strategies

The present study explored the problem‐solving strategies of high‐ and low‐spatial visualization ability learners on a novel spatial anatomy task to determine whether differences in strategies contribute to differences in task performance. The results of this study provide further insights into the processing commonalities and differences among learners beyond the classification of spatial visualization ability alone, and help elucidate what, if anything, high‐ and low‐spatial visualization ability learners do differently while solving spatial anatomy task problems. Forty‐two students completed a standardized measure of spatial visualization ability, a novel spatial anatomy task, and a questionnaire involving personal self‐analysis of the processes and strategies used while performing the spatial anatomy task. Strategy reports revealed that there were different ways students approached answering the spatial anatomy task problems. However, chi‐square test analyses established that differences in problem‐solving strategies did not contribute to differences in task performance. Therefore, underlying spatial visualization ability is the main source of variation in spatial anatomy task performance, irrespective of strategy. In addition to scoring higher and spending less time on the anatomy task, participants with high spatial visualization ability were also more accurate when solving the task problems. Anat Sci Educ 7: 280–288.