Eibofner Frank, Martirosian Petros, Würslin Christian, Graf Hansjörg, Syha Roland, Clasen Stephan
Section on Experimental Radiology, University Hospital Tübingen, Tübingen D-72076, Germany.
Department of Diagnostic and Interventional Radiology, University Hospital Tübingen, Tübingen D-72076, Germany.
Med Phys. 2015 Nov;42(11):6558-63. doi: 10.1118/1.4932629.
In interventional magnetic resonance imaging, instruments can be equipped with conducting wires for visualization by current application. The potential of sequence triggered application of transient direct currents in balanced steady-state free precession (bSSFP) imaging is demonstrated.
A conductor and a modified catheter were examined in water phantoms and in an ex vivo porcine liver. The current was switched by a trigger pulse in the bSSFP sequence in an interval between radiofrequency pulse and signal acquisition. Magnitude and phase images were recorded. Regions with transient field alterations were evaluated by a postprocessing algorithm. A phase mask was computed and overlaid with the magnitude image.
Transient field alterations caused continuous phase shifts, which were separated by the postprocessing algorithm from phase jumps due to persistent field alterations. The overlaid images revealed the position of the conductor. The modified catheter generated visible phase offset in all orientations toward the static magnetic field and could be unambiguously localized in the ex vivo porcine liver.
The application of a sequence triggered, direct current in combination with phase imaging allows conspicuous localization of interventional devices with a bSSFP sequence.
在介入式磁共振成像中，仪器可配备导线，通过施加电流来实现可视化。本文展示了在平衡稳态自由进动（bSSFP）成像中序列触发施加瞬态直流电的潜力。
在水模和离体猪肝中对一根导线和一根改良导管进行了检测。在bSSFP序列中，通过触发脉冲在射频脉冲与信号采集之间的间隔内切换电流。记录幅度图像和相位图像。通过后处理算法评估存在瞬态场改变的区域。计算相位掩码并将其叠加在幅度图像上。
瞬态场改变导致连续的相位偏移，后处理算法将其与由持续场改变引起的相位跳变区分开来。叠加后的图像显示了导线的位置。改良导管在朝向静磁场的所有方向上都产生了可见的相位偏移，并且能够在离体猪肝中明确地定位。
序列触发的直流电与相位成像相结合的应用，能够通过bSSFP序列对介入设备进行显著定位。
