Effects of heart valve prostheses on phase contrast flow measurements in Cardiovascular Magnetic Resonance – a phantom study

Figures

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  Fig. 1. Setting of the MR flow phantom for in-vitro assessment of heart valve prostheses. a. Scheme of the experimental setting showing the closed circuit flow phantom as placed in the scanner. b. Scheme of the acrylic pipe and positioning of the measurement slices (S1-S12). c. Coronal magnitude image of the acrylic pipe, proximal and distal parts of the tube system and positioning of the measurement slices. The arrow demonstrates the direction of flow

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  Fig. 2. Objects investigated in flow phantom. a. Metal-free aortic valve shaped inlay, containing solely plastics. b. Biological aortic valve prosthesis, containing metal-stent. c. Biological aortic valve prosthesis, containing metal-stent. d. Mechanical aortic valve prosthesis, containing carbon

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  Fig. 3. Results of B0 mapping. a. Coronal images of B0 maps, coloured scale in Hertz. b. Corresponding profile plots showing the quantitative magnetic field distortion from B0 in Hertz. c. Corresponding coronal magnitude images. White dashed line top right: Intraluminal positioning of slice for generating profile plots in MATLAB. d. Description of the magnetic field distortions according to quantitative score

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  Fig. 4. Quantitative aberration from B0 magnetic field in all investigated objects. Deviation in Hertz (Hz) derived from B0 maps and profile plots. Corresponding table showing positive and negative maximum of field aberration in Hz over the whole investigated distance. The numbers within the bars indicate the absolute range of deviation in Hz, as it is used for the quantitative score

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  Fig. 5. Flow deviation. Deviation of the assessed flow from reference flow over distance. Dark grey: range of equivalence 15%. Light grey: range of equivalence 20%. Black dashed lines: 95% confidence interval

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  Fig. 6. PC flow measurements in-vitro and in-vivo including a synthetic aortic valve model, two biological and one mechanical aortic valve prosthesis. a. Flow measured in-vitro over the distance to the valve. b. Flow measured in-vivo over the distance to the valve. c In-vivo: Long axis view (Cine-imaging, steady state free precession) showing the left ventricular outflow tract and the position of the aortic prosthesis (white arrow). d In-vivo: cine imaging of the aortic valve location (left) and ascending aorta in the area of the suspected restored flow 26.4 mm distal to the aortic valve (right) for each subject (columns)

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  Fig. 7. Background offset error detection. Measurements without flow. Deviation of estimated flow from reference flow over the entire distance in all investigated objects. S2-12 = positions of image acquisition in flow phantom