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1、胸部和全腹部,门控(Gating),人体许多部位的器官和组织都会或多或少地受呼吸.液体流动.脉搏和心跳的影响，所以在做相应部位检查的时候为了采集相对静止的图像，人们采取了一些措施，一般的方法为增加预饱和脉冲序列，其中目前主要的方法是利用“门控”。 类型主要为：呼吸触发.周围脉搏和心电门控。,什么是门控？,In Magnetic Resonance Imaging It is a device to synchronize MR data collection with the physiological motions of the patient It significantly reduc
2、es motion-related artifacts due to Respiration Flow Cardiac Motion,Overview,Types of Gating Respiratory Triggering PPG Gating Cardiac Gating,Respiratory Triggering,Types of Gating What is it used for? To reduce artifacts caused by respiratory motion or when a patient is unable to perform a breath-ho
3、ld Where is it used? Most used in the abdomen to help produce clear, artifact-free images of the anatomical structures in the abdomen What is needed? Respiratory bellow and respiratory gating hardware How does it do it? By synchronizing data collection of the sequence to the patients respiratory mot
4、ion.,Respiratory Triggering,Types of Gating How does it do it? By synchronizing data collection of the sequence to the patients respiratory motion. Changes in the patients chest circumference are converted to electronic signal and related to the MR Imaging system Proper placement of the bellows is r
5、equired across the trunk of the patient where the breathing is most evident. They should be place taut across the patient. Avoid stretching of the bellows Instruct patient to breath normalthis insures a most accurate waveform Respiratory interval typically ranges from 400 ms - 15000 ms for one respi
6、ratory cycle.,Respiratory Triggering,Respiratory Triggering,Next,Types of Gating Respiratory Triggering PPG Gating Cardiac Gating,PPG What is is used for? To reduce artifacts caused by CSF motion or when CINE imaging with better coverage of diastole is desired Where is it used? Cervical & Thoracic S
7、pine What is needed? Photoplethysmography (PPG) peripheral pulse monitory and hardware How does it work? The patients pulse will trigger data acquisition and synchronize image collection to the patients pulse,Peripheral Pulse Gating,Peripheral Pulse Gating,Dichrotic Notch Occurs at the end of systol
8、e, and the beginning of diastole when the aortic valve closes. The aorta contracts, causing flow into the coronaries and a slight increase in peripheral flow,Next,Types of Gating Respiratory Triggering PPG Gating Cardiac Gating,Cardiac Gating,ECG What is is used for? To reduce artifacts from cardiac
9、 motion, imaging of the heart or any other areas affected by the cardiac cycle Where is it used? In the thorax What is needed? ECG Electrodes, Lead Wires & hardware How does it work? By synchronizing MR Data collection of the sequence with the cardiac cycle of the patient,Cardiac Gating,波形,Cardiac G
10、ating,Diastole The period of ventricular filling beginning near the end of the T wave and ends near the peak of the R wave Systole The period of ventricular contraction starting after the R wave and ends near the end of the T wave,Problem Solving,What to do if gating doesnt work? Check connections o
11、f the the gating hardware Check proper placement on the patient Respiratory Are the bellows stretched to far or not far enough PPG Does the patient have finger nail polish or long finger nails ECG Are the lead wires braided Did you select the proper gating software,Conclusion,Types of Gating Respira
12、tory Triggering PPG Gating Cardiac Gating,胸部,纵隔结构及病变显示：平扫横断位T1W+T2W（加上门控），强化后再扫T1W（压脂）。 另外可视病变部位加扫矢状或冠状位甚至斜位。 层厚38mm不等，注意选择相位编码的方向以及调整FOV的大小，以防折叠伪影的产生。 心脏的扫描主要是观察结构与其功能，所以扫描序列主要为T1W和Cine,强化后进行心肌灌注扫描（包括延迟扫描）和AngioCe成像。位置包括：横断位 长短轴 四腔室和几个进出口及其瓣膜。,T1w图像,T1W&Cine,四腔室,入 出口,流出道,T2w 图像,短轴的扫法,长轴怎么扫？,MRC的临床应
13、用,心脏的常规定位方法,瓣膜及大血管的显示,主动脉瓣,MRA&MRA-DSA,未减影图像,减影后图像,胸主动脉图像,定位像,腹部（上中下）,平扫：T1W+T2W，强化：T1W（压脂）。另外根据临床要求，增加水成像，动态扫描和延迟扫描序列。 胰腺和肾脏(肾上腺）的检查需要作平扫压脂。 水成像要根据患者情况来决定用2D还是3D扫描。 层厚18mm或自定义。 方位：在横断位的基础上增加冠 矢以及斜位。,肝 胆 胰 脾 肾（T2W）,T1W,胆,肠道的显示,盆腔,直肠癌,女性生殖系统,MRI在胎儿检查中的应用,尸检后再做MRI. CT和X-ray检查,乳腺,一般用专用的乳腺线圈，也可以用别的信噪比相似
14、的表面线圈代替（个人观点）。冠状，横断再加上失状位。平扫 ：T1w（SE）+T2W（FSE 压脂）+STIR。强化后扫T1w(压脂）。患者主要采用俯卧位，让乳房自然悬垂，偶尔也采用患侧侧卧位。,Precontrast - Postcontrast and subtraction image showing the lesion,男性盆腔极其生殖系统,中下腹及盆腔的MRA,水成像,输尿管异位开口,四肢及其关节,平扫：T2W（压脂）+T1W+T1W（压脂）。 强化：T1W（压脂），必要时加作血管成像。 层厚：0.58mm。 方位：冠状 矢状必要时加横断位。,上肢及其关节,下肢及其关节,高分辨率MRI图像,
