Anna Fyrenius

Particle trace visualization of intracardiac flow using time-resolved 3D phase contrast MRI

The flow patterns in the human heart are complex and difficult to visualize using conventional two‐dimensional (2D) modalities, whether they depict a single velocity component (Doppler echocardiography) or all three components in a few slices (2D phase contrast MRI). To avoid these shortcomings, a temporally resolved 3D phase contrast technique was used to derive data describing the intracardiac velocity fields in normal volunteers. The MRI data were corrected for phase shifts caused by eddy currents and concomitant gradient fields, with improvement in the accuracy of subsequent flow visualizations. Pathlines describing the blood pathways through the heart were generated from the temporally resolved velocity data, starting from user‐specified locations and time frames. Flow trajectories were displayed as 3D particle traces, with simultaneous demonstration of morphologic 2D slices. This type of visualization is intuitive and interactive and may extend our understanding of dynamic and previously unrecognized patterns of intracardiac flow. Magn Reson Med 41:793–799, 1999.

Three dimensional flow in the human left atrium

BACKGROUND Abnormal flow patterns in the left atrium in atrial fibrillation or mitral stenosis are associated with an increased risk of thrombosis and systemic embolisation; the characteristics of normal atrial flow that avoid stasis have not been well defined. OBJECTIVES To present a three dimensional particle trace visualisation of normal left atrial flow in vivo, constructed from flow velocities in three dimensional space. METHODS Particle trace visualisation of time resolved three dimensional magnetic resonance imaging velocity measurements was used to provide a display of intracardiac flow without the limitations of angle sensitivity or restriction to imaging planes. Global flow patterns of the left atrium were studied in 11 healthy volunteers. RESULTS In all subjects vortical flow was observed in the atrium during systole and diastolic diastasis (mean (SD) duration of systolic vortex, 280 (77) ms; and of diastolic vortex, 256 (118) ms). The volume incorporated and recirculated within the vortices originated predominantly from the left pulmonary veins. Inflow from the right veins passed along the vortex periphery, constrained between the vortex and the atrial wall. CONCLUSIONS Global left atrial flow in the normal human heart comprises consistent patterns specific to the phase of the cardiac cycle. Separate paths of left and right pulmonary venous inflow and vortex formation may have beneficial effects in avoiding left atrial stasis in the normal subject in sinus rhythm.

Lectures in problem-based learning—Why, when and how? An example of interactive lecturing that stimulates meaningful learning

Even though opinions differ as to whether lecturing is compatible with problem-based learning (PBL) or not, lectures are still a common form of instruction in PBL curricula. This paper discusses the lecture in the framework of theories of learning in general and the medical problem-based learning tradition in particular. An example of how theories of learning can be implemented in the lecture hall is presented. Theories that underpin PBL as an educational philosophy rather than as a method of instruction are reviewed. A lecture form, organized in introductory, in depth and application lectures, that responds to important factors for stimulating deep processing of knowledge and meaningful learning is discussed. Examples of and practical points about how to renew and restructure lectures in a way that counteracts surface approaches to learning, teacher centring and student passivity are presented. We argue that, with proper awareness of possible drawbacks of the large format, lectures can be used as valuable tools for learning also in a PBL curriculum.

Student approaches to achieving understanding—approaches to learning revisited

This article presents a phenomenographic study that investigates students’ approaches to achieving understanding. The results are based on interviews, addressing physiological phenomena, with 16 medical students in a problem‐based curriculum. Four approaches—sifting, building, holding and moving—are outlined. The holding and moving approaches describe variations in deep‐level processing. The moving approach is characterised by an intention to continuously refine understanding in an open‐ended process. The student strives for a change in perspective and deliberately creates actions that are rich in variation and challenge. The holding approach is characterised by an intention to reach a final goal. This is achieved by high degrees of structure and control in the learning act. Understanding is sometimes sealed, ‘held on to’ and can be threatened by new input and other students’ viewpoints. The study also shows how students deal with details when constructing understanding of wholes.

Perspectives on using multimedia scenarios in a PBL medical curriculum

In 1999, the Faculty of Health Sciences at Linköping University, Sweden, started up a process of replacing text-based problem-based learning (PBL) scenarios with web-based multimedia-enhanced scenarios. This article brings together three studies of the results of this process and the experience gained from 10 years of implementation work. Results and conclusions: Adding multimedia to PBL scenarios makes them more realistic and thereby more motivating and stimulating for the student to process. The group process is not disrupted by the introduction of the computer in the group room. It is important to challenge the students by varying the scenarios’ perspective and design in order to get away from cue-seeking behaviors that might jeopardize a deep approach to learning. Scrutinizing all scenarios in a PBL curriculum can be used as a tool for improvement and renewal of the entire curriculum.