J Korean Soc Magn Reson Med.  2014 Sep;18(3):244-252. 10.13104/jksmrm.2014.18.3.244.

Cardiac Magnetic Resonance Imaging Using Multi-physiological Intelligent Trigger System

• Park J
• Yoon JH
• Yang YJ
• Ahn CB

• KMID: 1999924
• DOI: http://doi.org/10.13104/jksmrm.2014.18.3.244

Abstract

PURPOSE
We proposed a multi-physiological signals based real-time intelligent triggering system(MITS) for Cardiac MRI. Induced noise of the system was analyzed.
MATERIALS AND METHODS
MITS makes cardiac MR imaging sequence synchronize to the cardiac motion using ECG, respiratory signal and second order derivative of SPO2 signal. Abnormal peaks due to arrhythmia or subject's motion are rejected using the average R-R intervals and R-peak values. Induced eddy currents by gradients switching in cardiac MR imaging are analyzed. The induced eddy currents were removed by hardware and software filters.
RESULTS
Cardiac MR images that synchronized to the cardiac and respiratory motion are acquired using MITS successfully without artifacts caused by induced eddy currents of gradient switching or subject's motion or arrhythmia. We showed that the second order derivative of the SPO2 signal can be used as a complement to the ECG signals.
CONCLUSION
The proposed system performs cardiac and respiratory gating with multi-physiological signals in real time. During the cardiac gating, induced noise caused by eddy currents is removed. False triggers due to subject's motion or arrhythmia are rejected. The cardiac MR imaging with free breathing is obtained using MITS.

Keyword

Multi-physiological Intelligent Trigger System (MITS); Cardiac MRI; ECG gating; SPO2 gating Respiratory gating

MeSH Terms

Arrhythmias, Cardiac
Artifacts
Complement System Proteins
Electrocardiography
Magnetic Resonance Imaging*
Noise
Respiration
Complement System Proteins

Figure

• 

  Fig. 1 Block diagram of MITS.

• 

  Fig. 2 Flow chart of the program to generate a trigger signal to spectrometer from multi-physiological signals is shown.

• 

  Fig. 3 Screen for the operation of MITS is shown.

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  Fig. 4 Acquired ECG signals and corresponding spectra: (a) ECG signal without application of the gradient fields. (b) Spin echo imaging with TR of 500ms for single slice imaging (fn = 2 Hz). (c) Spin echo imaging with TR of 1000 ms and the number of slices of 10 (fn = 10 Hz). The eddy-current induced noise peaks (fn) are marked with small rectangles.

• 

  Fig. 5 Acquired ECG signals and corresponding spectra during various gradient echo imaging. (a) Spoiled gradient echo imaging with TR of 500ms and the number of slices of 10 (fn = 20 Hz). (b) Balanced SSFP imaging with TR of 4.71 ms for single slice imaging (fn = 213 Hz). (c) Spiral SSFP imaging with TR of 5ms for single slice imaging (fn = 200 Hz). The eddy-current induced noise peak (fn) is marked with a small rectangle.

• 

  Fig. 6 Comparison of cardiac CINE MR images are shown with free breathing (a), breath-hold (b), and respiratory gating (c). Three cardiac phases are shown in vertical direction. ECG gating was applied for all the cases (a)-(c). Note blurring in the heart wall in (a) in contrast to clear boundaries in (b) and (c).

• 

  Fig. 7 Comparison of cardiac CINE MR images are shown with ECG gating (a) and SPO2 gating (b). Respiratory gating was applied both in (a) and (b). Three cardiac phases are shown in vertical direction.

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