Motion detection improvement of a pencil-beam navigator echo using a gradient reversal technique

详细信息    查看全文

• 作者：Yuji Iwadate^a ; ^{yuji.iwadate@ge.com" class="auth_mail" title="E-mail the corresponding author} ; Kunihiro Miyoshi^b ; Hiroyuki Kabasawa^a
• 关键词：Magnetic resonance imaging ; Pencil beam excitation ; Navigator ; Gradient reversal ; Motion correction
• 刊名：Magnetic Resonance Imaging
• 出版年：2015
• 出版时间：November 2015
• 年：2015
• 卷：33
• 期：9
• 页码：1168-1172
• 全文大小：540 K

文摘

To develop and demonstrate the feasibility of a pencil-beam navigator using a gradient reversal technique for reducing signal contamination from undesired excitation for precise motion detection and correction.

Materials and methods

The navigator echo was obtained using normal and reversed gradient waveforms sequentially in three-dimensional spoiled gradient-recalled echo imaging. These two signals were combined in the complex domain for generating the final navigator data, which were used for detecting the diaphragm motion to nullify the side lobe effects with the smallest radius from the beam center. The navigator signals were compared with and without the proposed technique in phantom and human scans. In addition, navigator-gated imaging was performed in the human scans.

Results

In a phantom experiment, the proposed technique diminished signals from a phantom placed outside the beam’s area. In human scans, the proposed technique reduced undesired signals in the navigator data for all subjects. The resultant images had fewer motion-induced ghosts than the images from the conventional technique for 8 subjects out of 10.

Conclusions

We have demonstrated that the gradient reversal technique reduced undesired signals in a pencil-beam navigator. This technique can be an alternative for free-breathing abdominal scan when the conventional navigator technique cannot detect the patient’s respiratory motion precisely.