Computer assisted radiology and surgeryConcepts for Visualization of Multidirectional Phase-contrast MRI of the Heart and Large Thoracic Vessels
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.
References (13)
- et al.
MR flow measurements for assessment of the pulmonary, systemic and bronchosystemic circulation: impact of different ECG gating methods and breathing schema
Eur J Radiol
(2007) - et al.
Measurement of flow with NMR imaging using a gradient pulse and phase difference technique
J Comput Assist Tomogr
(1984) - et al.
Cardiovascular flow measurement with phase-contrast MR imaging: basic facts and implementation
Radiographics
(2002) - et al.
Improved ejection fraction and flow velocity estimates with use of view sharing and uniform repetition time excitation with fast cardiac techniques
Radiology
(1995) - et al.
Complex flow patterns in the great vessels: a review
Int J Card Imaging
(1999) - et al.
4D magnetic resonance velocity mapping of blood flow patterns in the aorta in young vs. elderly normal subjects
J Magn Reson Imaging
(1999)
Cited by (26)
Imaging-Based 4D Aortic Pressure Mapping in Marfan Syndrome Patients: A Matched Case-Control Study
2020, Annals of Thoracic SurgeryCitation Excerpt :Figure 1 (A-E) provides an overview of the methodologic process for relative pressure analysis. Computation and assessment of relative pressures were performed using a dedicated in-house-developed image processing software.15 The pressure computation algorithm has been described in detail and validated previously.11,16
Impact of an Aortic Nitinol Stent Graft on Flow Measurements by Time-resolved Three-dimensional Velocity-encoded MRI
2012, Academic RadiologyCitation Excerpt :The marking system allowed the identification of the same six levels in both acquisitions of 2D through-plane VEC MRI and analysis of stacked-2D-3dir-MRI and 3D-3dir-MRI data sets. Quantitative analysis of the acquired flow data was performed using the dedicated postprocessing software Mediframe (21). A phase offset error correction was applied to 3D VEC MRI data prior to analysis (22).
In vitro validation of flow measurements in an aortic nitinol stent graft by velocity-encoded MRI
2011, European Journal of RadiologyCitation Excerpt :For each flow waveform, setups without and with stent graft were measured after each other before continuing with the next waveform. Quantitative analysis of the acquired flow data was performed with dedicated postprocessing software [20]. A region of interest was placed on the phase image and adjusted for each time step.
Tridirectional phase-contrast magnetic resonance velocity mapping depicts severe hemodynamic alterations in a patient with aortic dissection type Stanford B
2011, Journal of Vascular SurgeryCitation Excerpt :These data were acquired by a 1.5-T clinical MR scanner (Magnetom Avanto; Siemens Medical Solutions, Erlangen, Germany) using the following parameters: spatial resolution, 1.5 × 1.5 × 2.1 mm3; velocity sensitivity, 150 cm/s along all three encoding directions; flip angle, 30°; and echo/repetition time, 4.05/61.20 ms. Retrospective electrocardiographic gating was used to synchronize the measurement with the cardiac motion (30 frames/cardiac cycle were reconstructed). The in-house developed software Mediframe5 was used for postprocessing to visualize and analyze streamlines and vector fields. Streamlines colored by velocity showed an acceleration of blood flow entering the false lumen through the primary entry (Fig 2, A).
Academic Radiology: A Decade of Change
2009, Academic RadiologyHeart applications of 4D flow
2020, Cardiovascular Diagnosis and Therapy