MRI技术应用：胸部和全腹部

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？•InMagneticResonanceImaging–ItisadevicetosynchronizeMRdatacollectionwiththephysiologicalmotionsofthepatient–Itsignificantlyreducesmotion-relatedartifactsdueto•Respiration•Flow•CardiacMotionOverview•TypesofGating–RespiratoryTriggering–PPGGating–CardiacGatingRespiratoryTriggering•TypesofGating–Whatisitusedfor?•Toreduceartifactscausedbyrespiratorymotionorwhenapatientisunabletoperformabreath-hold–Whereisitused?•Mostusedintheabdomentohelpproduceclear,artifact-freeimagesoftheanatomicalstructuresintheabdomen–Whatisneeded?•Respiratorybellowandrespiratorygatinghardware–Howdoesitdoit?•Bysynchronizingdatacollectionofthesequencetothepatient’srespiratorymotion.RespiratoryTriggering•TypesofGating–Howdoesitdoit?•Bysynchronizingdatacollectionofthesequencetothepatient’srespiratorymotion.–Changesinthepatient’schestcircumferenceareconvertedtoelectronicsignalandrelatedtotheMRImagingsystem–Properplacementofthebellowsisrequired»acrossthetrunkofthepatientwherethebreathingismostevident.Theyshouldbeplacetautacrossthepatient.Avoidstretchingofthebellows»Instructpatienttobreathnormal…thisinsuresamostaccuratewaveform»Respiratoryintervaltypicallyrangesfrom400ms-15000msforonerespiratorycycle.RespiratoryTriggeringRespiratoryTriggeringNext•TypesofGating–RespiratoryTriggering–PPGGating–CardiacGating•PPG–Whatisisusedfor?•ToreduceartifactscausedbyCSFmotionorwhenCINEimagingwithbettercoverageofdiastoleisdesired–Whereisitused?•Cervical&ThoracicSpine–Whatisneeded?•Photoplethysmography(PPG)peripheralpulsemonitoryandhardware–Howdoesitwork?–ThepatientspulsewilltriggerdataacquisitionandsynchronizeimagecollectiontothepatientspulsePeripheralPulseGatingPeripheralPulseGating•DichroticNotch–Occursattheendofsystole,andthebeginningofdiastolewhentheaorticvalvecloses.–Theaortacontracts,causingflowintothecoronariesandaslightincreaseinperipheralflowNext•TypesofGating–RespiratoryTriggering–PPGGating–CardiacGatingCardiacGating•ECG–Whatisisusedfor?•Toreduceartifactsfromcardiacmotion,imagingoftheheartoranyotherareasaffectedbythecardiaccycle–Whereisitused?•Inthethorax–Whatisneeded?•ECGElectrodes,LeadWires&hardware–Howdoesitwork?–BysynchronizingMRDatacollectionofthesequencewiththecardiaccycleofthepatientCardiacGating波形CardiacGating•Diastole–TheperiodofventricularfillingbeginningneartheendoftheTwaveandendsnearthepeakoftheRwave•Systole–TheperiodofventricularcontractionstartingaftertheRwaveandendsneartheendoftheTwaveProblemSolving•Whattodoifgatingdoesn’twork?–Checkconnectionsofthethegatinghardware–Checkproperplacementonthepatient•Respiratory–Arethebellowsstretchedtofarornotfarenough•PPG–Doesthepatienthavefingernailpolishorlongfingernails•ECG–Aretheleadwiresbraided–DidyouselectthepropergatingsoftwareConclusion•TypesofGating–RespiratoryTriggering–PPGGating–CardiacGating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3~8mm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Angio—Ce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1~8mm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-Postcontrastandsubtractionimageshowingthelesion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：0.5~8mm。•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