1 / 16

Basics of MRI

Basics of MRI. NMR verses MRI. Spectrum. Projection. Spin Warp MRI. Slice Selection. Excitation Spectrum. RF. +. Selected Slice. Gradient. Slice Selection Rephasing. RF. Gradient. Frequency Encoding. NMR & Sampling. Object. Profile. Gradient. G R. d FOV. Frequency Encoding.

henry
Download Presentation

Basics of MRI

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Basics of MRI

  2. NMR verses MRI Spectrum Projection

  3. Spin Warp MRI

  4. Slice Selection Excitation Spectrum RF + Selected Slice Gradient

  5. Slice Selection Rephasing RF Gradient

  6. Frequency Encoding NMR & Sampling Object Profile Gradient GR dFOV

  7. Frequency Encoding NMR Gradient

  8. Phase Encoding Collect a trace for each value of the phase encoding gradient Just like 2d NMR NMR Gread Gphase npe

  9. Contrast in MRI Image contrast arises from differences in signals! What differences? • Signal is a function of: •  - Proton density • T1 Spin-Lattice relaxtion time • T2 - Spin-Spin relaxation time • T2* - magnetic susceptibility • D - diffusion • flow - blood, CSF etc • function - brain function, cardiac function • etc

  10. Gradient Echo (Spin Warp) - GEMS T2* dependence Spin Echo - SEMS T2 dependence Fast Spin Echo - FSE Echo Planar Imaging - EPI Spiral MRI Many hybrids of above!!! Basic MRI Acquisition Schemes

  11. Gradient Echo • GEMS - Varian seqlib • Other names: • FLASH, GRASS, FFE < 90° (flip angle) Contrasts: dependent on  & TR T1, proton density Sensitivity to Susceptibilitydepends on TE Variants: RF or Gradient Spoiling Turbo FLASH (SnapShot) RF & NMR GSlice GRead GPhase

  12. Refocused Gradient Echo • GEMS - Varian seqlib • Other names: • FAST, Refocused FLASH, GRASS, FFE, FISP < 90° (flip angle) Steady-state preserved by rewinding phase gradient. Contrasts: dependent on  & TR T1, proton density Sensitivity to Susceptibilitydepends on TE RF & NMR GSlice GRead GPhase

  13. Spin Echo • SEMS - Varian seqlib • Contrasts: • T2 thru TE • T1 thru TR • Proton density RF & NMR GSlice GRead GPhase

  14. Fast Spin Echo Fast Spin Echo (FSE) Turbo Spin Echo (TSE) RARE RF & NMR GSlice GRead GPhase

  15. Echo Planar Imaging - EPI • Images in <50-100ms • Gradient Echo & • Spin Echo variants • Disadvantages: • Susceptibility • Nyquist Ghosts RF & NMR GSlice GRead GPhase

  16. Spiral Imaging • Images in <50-100ms • Gradient Echo & • Spin Echo variants • Disadvantages: • Very Complicated Recon • Very Demanding of HW • Advantages: • Motion insensitivity RF & NMR GSlice GRead GRead

More Related