3/21/20111McBride Brain Institute field trip is Tuesday March 22Meet at MBI at 5:10 pm sharp!Meet here at 5:10 pmComponents of an MRI systemThe Static Magnet The permanent magnet.  Resistive Electromagnet Superconducting ElectromagnetMagnetic Resonance ImagingRF System The Transmitter is made up of an RF synthesizer, power amplifier, and transmitting coil. The receiver consists of a pick-up coil, amplifier, and signal processing system. The Magnet Gradients  Magnet gradients are produced by coils which are not pararllel. Coils are resistive magnets. Produce gradients from 20 mT/m to 100 mT/m.May be the sameSome Nuclei Commonly Used in NMRNuclei Unpaired ProtonsUnpaired NeutronsNet Sping(MHz/T)1H 1 0 ½ 42.582H 1 1 1 6.5431P 1 0 ½ 17.2523Na 1 2 3/2 11.2714N 1 1 1 3.0813C 0 1 ½ 10.7119F 1 0 ½ 40.08Spin in a Magnetic Field The nuclear magnetic moment precesses about the applied magnetic field Possible nuclear spin states High Energy  Low EnergyPhoton AbsorptionTransition from low energy state to high energy state absorbs a photonThe energy needed to make the transition depends on the magnetic moment of the nucleus and the strength of the applied magnetic field3/21/20112Energy Shift=Frequency of Detection= gB0∆E/h =Larmor FreqSome Nuclei Commonly Used in NMRNuclei Unpaired ProtonsUnpaired NeutronsNet Sping(MHz/T)1H1 0 ½42.582H1 1 1 6.5431P1 0 ½ 17.2523Na 1 2 3/2 11.2714N1 1 1 3.0813C0 1 ½ 10.7119F1 0 ½ 40.08= gB0What did the Quantum Mechanic say when asked “What’s New?”A. A. Small WorldB. B. Pussy CatC. C. Isaac NewtonD. D. E over hE. E. The cat may be dead; it’s uncertainr.f. ResonanceWhen a steady magnetic field is applied to a sample of material, the majority of nuclei are in the high energy state.When the sample is saturated with radio waves (photons) at the resonant (Larmor) frequency, the high and low energy populations become equal(T=∞).The radio frequency energy (photons) emitted as the sample returns to its initial state can be measured.At what frequency are the photons emitted when the sample returns to its initial state?A. A. Larmor frequencyB. B. 2 times LarmorC. C. It is a broad spectrum of frequenciesD. D. It is randomE. E. Amor frequencyNobel Prizes related to NMROtto Stern, USA: Nobel Prize in Physics 1943 "for his contribution to the development of molecular ray method and his discovery of the magnetic moment of the proton"Isidor I. Rabi, USA: Nobel Prize in Physics 1944 "for his resonance method for recording the magnetic properties of atomic nuclei"Felix Bloch, USA and Edward M. Purcell, USA: Nobel Prize in Physics 1952 "for their discovery of new methods for nuclear magnetic precision measurements and discoveries in connection therewith"Richard R. Ernst, Switzerland: Nobel Prize in Chemistry 1991 "for his contributions to the development of the methodology of high resolution nuclear magnetic resonance (NMR) spectroscopyKurt Wüthrich, Switzerland: Nobel Prize in Chemistry 2002 "for his development of nuclear magnetic resonance spectroscopy for determining the three-dimensional structure of biological macromolecules in solution"Paul C. Lauterbur, USA and Peter Mansfield, United Kingdom:Nobel Prize in Physiology or Medicine 2003 "for their discoveries concerning magnetic resonance imaging"http://www2.chemistry.msu.edu/facilities/nmr/900Mhz/MCSB_NMR_nobel.html3/21/20113As energy of photons is raised, their wavelength shortens.Therefore, the resolution of an MRI image—A. Decreases as the magnetic field is raisedB. Increases as the magnetic field is raised C. Is not affected by the magnitude of the magnetic fieldPulsed Fast Fourier Transform Spectroscopy A steady magnetic field is applied and a pulse of radio waves containing a range of frequencies is sent through the sample. More efficient-measures response at many frequencies at one time Which picture is Richard Ernst, the Nobel Prize winnerin Chemistry in 1991?ABC. BothFT A Fourier Transform is used to convert the data from time to the frequency domain.Intensity of received radio signalBig Magnets Rule NMR spectroscopy requires very strong magnets (up to 21 Tesla). A stronger magnet results in a larger energy level split =higher energy photons =shorter wavelength.Inside the DewarInside the Magnet3/21/20114Block diagram of imaging systemRF coils in useSurface coils are commonly used for spines, shoulders, TMJ's, and other relatively small body parts. Z-gradient used occasionally as RF coils for pelvis imaging and cervical spine imaging. This coil is commonly used as a transceiver coil for imaging of the head. Paired saddle coils are commonly used for imaging of the knee. By running current in opposite directions in the two halves of the gradient coil, the magnetic field is made stronger near one and weaker near the other.What type of pick-up coil is shown here?A. Surface coilB. Birdcage coilC. Helmholtz coilD. Saddle coilE. Darth Vader