磁共振持试验课件.ppt

1、磁共振實驗磁共振實驗o核磁共振是指原子核在靜止磁場中，受核磁共振是指原子核在靜止磁場中，受電磁波激發而產生共振現象。電磁波激發而產生共振現象。o磁振造影引用磁場梯度造成磁共振訊號磁振造影引用磁場梯度造成磁共振訊號的改變再經由電腦分析組合成影像，就的改變再經由電腦分析組合成影像，就是一般看到的是一般看到的 MRI 影像。影像。o MRI Time lineo 1946 MR phenomenon-Bloch&Purcell o 1952 Nobel Prize-Bloch&Purcell o 1950-1970 NMR developed as analytical toolo 1972 Com

2、puterized Tomography-Hounsfield o 1973 Back projection MRI-Lauterbur o 1975 Fourier Imaging(phase encording and frequency encording-Ernst o 1977 Echo-planar imaging-Mansfield o 1980 FT MRI demonstrated-Edelstein o 1986 Gradient Echo Imaging NMR Microscope o 1987 MR Angiography-Dumoulin o 1991 Nobel

3、Prize-Ernst o 1992 Functional MRI o 1994 Hyperpolarized 129Xe Imaging o 2003 Nobel Prize-Lauterbur&Mansfield Edward Purcell Purcells the NMR detection shared the 1952 Nobel Prize for physics with Felix Block Felix Block He shared the Nobel prize with Edward Purcell for developing the nuclear magneti

4、c resonance to measure the magnetic field of atomic nuclei Creatine PhosphatePhosphodiesterInorganic phosphate磷酸鹽肌酸磷酸鹽o 羅特柏 曼斯菲爾 因而共摘諾貝爾醫學獎桂冠 o 瑞典卡洛林卡斯學院的諾貝爾委員會宣布，美國化學家羅特堡（Paul C.Lauterbur），以及英國物理學家曼斯菲爾爵士（Sir Peter Mansfield），以致力研究核磁共振掃描（MRI）為醫療檢驗帶來革命，榮獲2003年的諾貝爾醫學獎。民生報/A11版/醫藥新聞 2005/08/20補充資料核磁共振攝

5、影核磁共振攝影(MRI)核磁共振攝影（亦稱磁振造影，magnetic resonance imaging，MRI）是近年來在臨床診斷上相當重要的影像工具。此種使用準確而不必侵入人體的方法為人體內部器官造影，對醫學的診斷、醫療和後續工作都十分重要。o年代年代 大事紀大事紀1895 德國物理學家侖琴發現德國物理學家侖琴發現 X 光光1896 愛迪生製造愛迪生製造 X 光透視機光透視機1898 居里夫婦發現釙及鐳居里夫婦發現釙及鐳1901 侖琴得第一屆諾貝爾物理獎侖琴得第一屆諾貝爾物理獎1903 居里夫婦得第三屆諾貝爾物理獎居里夫婦得第三屆諾貝爾物理獎1934 Irene Curie 及及 Fred

6、eric Joliot(居理夫婦的大女兒及女婿居理夫婦的大女兒及女婿)因製造人工同位素，得諾貝爾物理獎因製造人工同位素，得諾貝爾物理獎1949 美國醫師美國醫師 Howry 建立初步超音波儀器建立初步超音波儀器1952 發現核磁共振現象的發現核磁共振現象的 Bloch 和和 Purcell 獲諾貝爾物理獎獲諾貝爾物理獎1971 首部頭部型首部頭部型 CT 在英國發明在英國發明1972 首部首部 CT 在美國展示在美國展示1977 首部首部 MRI 問世問世1978 台灣引進第一部台灣引進第一部 CT(台北榮總台北榮總)1979 CT 發明人英國的發明人英國的 Hounsfield 及及 Cor

7、mack 得諾貝爾醫學獎得諾貝爾醫學獎1985 FDA 核准核准 MRI 臨床使用臨床使用1989 台灣引進第一部台灣引進第一部 MRI(台中榮總台中榮總)1991 發明核磁共振高解像技術的發明核磁共振高解像技術的 Ernst 獲諾貝爾化學獎獲諾貝爾化學獎1995 PET（正子攝影）由（正子攝影）由 FDA 認可臨床使用認可臨床使用2002 發明核磁共振三度空間解像的發明核磁共振三度空間解像的 Wuthrich 獲諾貝爾化學獎獲諾貝爾化學獎2003 MRI 發明人發明人 Lauterbur 和和 Mansfield 獲諾貝爾醫學獲諾貝爾醫學CT：Computerized Tomography

8、電腦斷層攝影電腦斷層攝影MRI：Magnetic Resonence Imaging 磁振造影磁振造影PET：Positron Emission 正子攝影正子攝影o從從 X 光光 CT MRI PET 追溯影像醫學發展史追溯影像醫學發展史 o特別是對全球頭號健康殺手癌症的偵測，日受重視，索費高達 10 數萬的全身 MRI 檢查，已成國內醫療院所健康檢查最熱門的項目。o肝、胰、脾、肺、腎等病變，及淋巴腺的異常，都可藉由 MRI 偵測出來，MRI 在癌症的診斷率可達 95%，若再配合正子攝影(PET），診斷率可達 98%，特別是攝護腺癌及甲狀腺癌，MRI 的診斷率較 CT 更高；除此外，癌細胞骨轉

9、移時，也可靠 MRI 偵測出來。In the absence of a magnetic field,these are randomly oriented but when a field is applied they line up parallel to the applied field,either spin aligned or spin opposed.The more highly populated state is the lower energy spin state spin aligned situation.In the absence of a magnetic

10、 field,these are randomly oriented but when a field is applied they line up parallel to the applied field,either spin aligned or spin opposed.The more highly populated state is the lower energy spin state spin aligned situation.o The proton can be thought as a small spinning bar of magnet with a mag

11、netic moment and an angular momentum J.=J where is the“gyromagnetic ratio.”o The nuclear angular momentum J is quantized in units of=h/2,J=Io The magnetic energy U of the nucleus in an external magnetic field is U=-B o If the magnetic field is along the z-direction,then the magnetic energy is U=-zBo

12、=-IzBo.In quantum mechanics,Iz=1/2 and-1/2 o The magnetic energy U of the nucleus in an external magnetic field B is U=-B Net magnetization vector M Magnetic moment vectorAs this diagram shows,the energy required for the spin-flip depends on the magnetic field strength at the nucleus.With no applied

13、 field,there is no energy difference between the spin states,but as the field increases so does the separation of energies of the spin states and therefore so does the frequency required to cause the spin-flip,referred to as resonance.The basic arrangement of an NMR spectrometer is shown to the left

14、.The sample is positioned in the magnetic field and excited via pulsations in the radio frequency input circuit.The realigned magnetic fields induce a radio signal in the output circuit which is used to generate the output signal.Fourier analysis of the complex output produces the actual spectrum.Th

15、e pulse is repeated as many times as necessary to allow the signals to be identified from the background noise.Free induction decaySpin-echo (1).A net magnetization is along the z-axis;(2).A 90o rf pulse;(3).The protons become asynchronous with each other during time;(4).A 180 pulse;(5).Allowing tim

16、e to elapse allows the protons to regain the phase coherence in the transverse plane.Evolution of M after the 90o and 180o pulses12345Time Time 180o pulse90o pulseHTS Receiver Coils for Nuclear Magnetic Resonance Imaging One of the objectives of the HTS MRI research is to obtain a better signal to r

17、atio(SNR).With a better SNR,one can have higher resolution in images and shorter scanning time.Wossil et al.,IEEE Trans Appl.Supercon.13,1050(2003):resonant frequency of NMRM:transverse magnetization v :voxel volumeB1:magnetic field produced by the surface coil with unit current f:bandwidth of the r

18、eceiverRC:coil resistance;RS:the resistance induced in the coil by the body induction losses TS:sample temperature;TC:coil temperature k:Boltzmans constant Using HTS coil,one can decrease the value of Rc to enhance the SNR.S N R M v4 kfB1RcTc RsTs4k fSuperconducting Tape CoilBi2Sr2Ca2Cu3Ox (Bi-2223,

19、BSCCO)Critical temperature:110 KCritical current Density:9000 A/cm2 at 77 KTape width:4.10 mm 0.10 mmTape thickness:0.230 mm 0.01 mmMinimum bending radius:30 mmDetailed Configuration of the HTS receiver coils Filling liquid nitrogen Liquid nitrogen transfer lineGradient coilThe set up of the mini-im

20、aging systemImages of kiwi fruit(a)(b)(c)SNR=71.1 with HTS coil at 77 K GEFI,TR=300 ms,TE=6.5 ms,FOV=5x5 cm2,256 256,NEX=4,Coil diameter=7 cm SNR=51.3 with copper coil at 77 KSNR=30 with copper coil at 300 KConclusionsMagnetically labeled Magnetically labeled immunoassayimmunoassaySSMSSMNDENDEBiomagnetismBiomagnetismNMRNMRWhat else can we do in the innovative SQUID research?SQUID&Magnetic FluidsThe End