Elsevier

Academic Radiology

Volume 15, Issue 3, March 2008, Pages 361-369
Academic Radiology

Computer assisted radiology and surgery
Concepts for Visualization of Multidirectional Phase-contrast MRI of the Heart and Large Thoracic Vessels

Parts of the data were presented at CARS 2006 in Osaka, Japan.
https://doi.org/10.1016/j.acra.2007.11.012Get rights and content

Rationale and Objectives

Multidirectional phase-contrast magnetic resonance imaging allows the acquisition of time-resolved velocity fields (vectors) of cardiac and vascular blood flow. Its unique ability to provide vectorial flow information promises to give new insights into hemodynamic physiology. However, up to now appropriate and standardized procedures and software tools are missing to take advantage of all the information contained in the data. The objective of this work is to present a new versatile software tool and to demonstrate its practical value for the examination of multidirectional blood flow.

Materials and Methods

An exemplary selection of data sets from healthy volunteers, patients with cardiovascular pathologies, and healthy domestic pigs has been acquired using a phase-contrast magnetic resonance imaging sequence based on FLASH (fast low angle shot) that encodes velocity as field of three-dimensional vectors. For data processing, we have developed a software tool that integrates the whole workflow, including noise filtering, interactive visualization, and flow quantification.

Results

Using the software tool visualization of complex flow data is easily generated within 5 minutes; interactive exploration of the data is possible in real-time. Exemplary physiologic and pathologic flow patterns were visualized in an intuitive manner. The visual results suggest valuable diagnostic information; its significance, however, must be further evaluated together with the development of more specific data processing.

Conclusions

Multidirectional phase-contrast magnetic resonance imaging is a valuable tool for assessment of cardiac and vascular hemodynamics. With the development of tools that offer standardized and thus comparable visualizations it may be integrated into the clinical routine in the near future.

Section snippets

Data

A phase-contrast pulse sequence has been used on a clinical 1.5 Tesla MR-System (Magnetom Symphony or Magnetom Avanto, Siemens, Erlangen, Germany). It is based on a spoiled gradient echo pulse sequence (fast low angle shot) and allows the acquisition of a time-resolved field of 3D velocity vectors in a single two-dimensional slice in addition to the morphologic image. This is achieved by encoding the three directions in rapid succession. Sequence parameters were repetition time = 10

Results

We present here some selected examples to demonstrate the features of the software tool and the usefulness of vector velocity imaging.

Generally, the tool allowed easy and fast generation of visualization scenes. Generation time, including loading DICOM files, data conversion, preprocessing, and visualization setup was about 5 minutes. Interactive exploration was possible in real-time on a dual-Xenon 2.8 GHz, 2GB workstation.

As a first case direction coherence maps of two different subjects were

Discussion

Multidirectional pc-MRI has shown to give deeper insights into specific cardiac and vascular flow patterns compared with other imaging techniques. Because of its integration and flexibility, the software proved to be a useful tool. However, the results must be considered carefully.

A prerequisite for valid visualization results is optimal imaging. As with most applications, high spatial and temporal resolution is desirable. Particularly to assess fine irregular flow patterns on a local level,

Acknowledgment

The authors are grateful to Andreas Greiser, PhD (Siemens Medical Solutions, Erlangen, Germany), for providing the phase-contrast flow sequence for the Magnetom Avanto.

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