High Field MR of the Spine

Transcription

1 Department of Radiology University of California San Diego 3T for MR Applications Advantages High Field MR of the Spine Increased signal-to-noise Better fat suppression Increased enhancement with gadolinium John R. Hesselink, M.D. Definite measurable benefits for fmri, MRS, MRA, Diffusion tensor, & brain imaging 3T for Spine Imaging Problems 1. Increased SAR (Large FOV met surveys with FSE) 2. Increased chemical shift 3. Decreased T1 contrast 4. Increased susceptibility 5. Dielectric effects 6. More flow artifacts 7. Increased gradient noise (130 db) 8. Increased cost of purchase & maintenance Increased SAR Increased chemical shift 3T for Spine Imaging Problem Solutions Trade-offs 1. Parallel imaging 2. Shaped RF waveforms 3. Flip angle for acquisition rf pulses 4. ETL, TR 5. 3D acquisition 1. Bandwidth 2. FOV, Matrix 3. Fat saturation None, scan time None Minimal Scan time Scan time but SNR SNR but min TE SNR but resolution SAR & may scan time 3T for Spine Imaging 3T for Spine Imaging Problem Solutions Trade-offs Problem Solutions Trade-offs Gray CSF on T1 images Increased Susceptibility Dielectric effects 1. T1 FLAIR Minimal 1. Bandwidth 2. Matrix & FOV & slice thickness 3. Parallel imaging 4. TE for T1WIs 1. 8-channel head coil 2. High electric permittivity pads SNR but min TE SNR but resolution None, scan time Better, SNR Better, SNR & scan time Cumbersome More flow Artifacts Increased gradient noise Increased cost of magnet & maintenance 1. Sat pulses 2. Change phase direction 3. Use gradient-echo 1. Better ear plugs 2. Acoustically shielded bore liners 1. Hire the Terminator as your negotiator SAR & may scan time May scan time SNR Cost Cost??? Proc. Intl. Soc. Mag. Reson. Med. 18 (2010)

2 C-Spine Sequences Cervical Axial Sequences T2 FSE T1 FSE T1 FLAIR T2 FSE T2 3D FRFSE Cervical Axial Sequences Cervical Axial Sequences T2 GRE T2 FSE GRE - MERGE COSMIC FIESTA / 3D CISS Post Gd Sequences Disk Extrusion T1 with Gad & FS

3 Susceptibility Artifact Hardware Post-op Cervical Spine Increase Bandwidth, Frequency SI / RL, Avoid GRE & Fat Suppression - Cervical Spine: Neurofibromatosis 3T Spine Protocols Cervical Spine Sequence TR/TE/ET/NEX FOV Slice Matrix Phase Bandwidth T1W Fat Sat FSE T1W IDEAL-FSE 15 / GE / Courtesy Scott Reeder UW-Madison Sagittal T2 FSE 4000/110/24/4 22 3/ x224 SI 31.2 Sagittal T1 FLAIR 3300/9/8/2/TI / x224 SI 41.7 Sagittal STIR 3200/24/12/3/TI / x224 SI 31.2 Axial T2 FSE 4500/120/21/4 20 3/1 448x224 AP 41.7 Axial T2 FRFSE 2200/100/39/ /0 320x224 AP&RL 41.7 Axial MERGE 450/11/1/2/20deg 20 3/ x192 AP 41.7 Sag T1 FSE Gd 600/11/4/3 24 3/1 384x224 AP 31.2 Axial T1 FSE Gd 700/10/3/3 24 3/1 384x224 AP 31.2 Thoracic Spine Thoracic Spine T2 FSE T1 FSE T1 FLAIR T2 FSE T1 FLAIR T1-Gd-FS -

4 Metastases T1 FLAIR at 3 T Courtesy: Meng Law, Mount Sinai, NY Sagittal T2 & T1 FSE Sagittal Lumbar Spine T2 FSE T1 FSE T2 FSE T1 FSE T1 FLAIR Phase-artifacts & Chemical Shift Phase Frequency Direction Phase AP Phase SI

5 Sagittal T2 FSE Effect of Vacation No SAT Bands, Phase AP, Low Matrix 3T MR-Cat Scan Fusion Axial Lumbar Sequences T2 FSE T1 FSE T1 FLAIR T2 FSE T1 FSE Phase-artifact Reduction Lumbar Disk Protrusion Crossed SAT Bands (Vision) T2 FSE T1 FSE T1 FLAIR

6 Proton-Density Axial No Coil No Signal Series 1 Series 2 T2 FSE T1 FSE PD FSE Post-Gd T1 with FS 1.5T Spine Imaging Post-op Lumbar Spine Post-op Lumbar Spine 1.5T Spine Imaging Post-op Lumbar Spine

7 Post-op Lumbar Spine History: 32 y/o male with back & leg pain Dx: Spinal stenosis Disk Protrusion Disk Extrusion - - Multiple Sclerosis {Page 2} -

8 History: 43 y/o man with back pain for several months {Page 2} 553 CV Dx: Hemangioblastoma History: 36 y/o man with a chronic C6-8 radiculopathy {Page 2} Dx: Spinal dural AVM History: 95 y/o woman with acute bilateral upper extremity weakness 3T Spine Protocols Lumbar Spine Sequence TR/TE/ET/NEX FOV Slice Matrix Phase Bandwidth Sagittal T2 FSE 4000/120/27/ / x224 SI 41.7 Sagittal T1 FLAIR 3000/30/8/2/TI / x224 SI 41.7 Sagittal STIR 3500/24/12/3/TI / x224 SI 31.2 Axial T2 FSE 4500/120/21/4 20 3/1 448x224 AP 41.7 Axial T1 FSE 600/10/4/2 20 3/1 320x224 AP 31.2 Axial PD FSE 3000/11/4/2 20 3/1 448x224 AP 31.2 Sag T1 FSE Gd 517/8/4/ / x224 AP 31.2 Axial T1 FSE Gd 600/10/4/2 20 3/1 320x224 AP 31.2 Dx: Acute cord infarction MRA FSPGR Gd 7.1/2.9/1/35deg / x224 AP-RL ml/sec