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Advanced MSK MRI Protocols at 3.0T

Advanced MSK MRI Advanced MSK MRI Protocols at 3.0TProtocols at 3.0T

Garry E. Gold, M.D. Associate Professor

Department of RadiologyStanford University

Garry E. Gold, M.D. Associate Professor

Department of RadiologyStanford University

OutlineOutline• Why High Field for MSK?• SNR and Relaxation Times• Technical Issues • Example protocols• New applications

•• Why High Field for MSK?Why High Field for MSK?•• SNR and Relaxation TimesSNR and Relaxation Times•• Technical Issues Technical Issues •• Example protocolsExample protocols•• New applicationsNew applications

MSK MR ImagingMSK MR Imaging

• Small structures (10-16 cm)• High resolution (< 0.5 mm)• Limited motion • Excellent contrast required

•• Small structures (10Small structures (10--16 cm)16 cm)•• High resolution (< 0.5 mm)High resolution (< 0.5 mm)•• Limited motion Limited motion •• Excellent contrast required Excellent contrast required

Rapid Knee ProtocolRapid Knee Protocol

SNR ComparisonSNR Comparison

Axial PD: SNR Ratio = 1.77

1.5T 3.0T

SNR ComparisonSNR Comparison

Sagittal PD: SNR Ratio = 1.81

1.5T 3.0T

Chemical Shift ArtifactChemical Shift Artifact

BW + 16 kHz BW + 64 kHz

Chemical Shift and BandwidthChemical Shift and BandwidthGood NewsBad News

Chemical shift doubles at 3.0Tcompared with 1.5T

Doubling the bandwidthcorrects chemical shift

Higher bandwidth:- more slices- shorter echo times- shorter echo spacing- less metal artifact

Doubling the bandwidth: loss of 2 SNR

Vascular ArtifactsVascular ArtifactsSagittal T2 FSE with Fat Sat With flow compensation

and S/I sat bands

Frequency S/I

RF Power DepositionRF Power DepositionT1 SE: 4 min T1 FSE: 2 min

Less RF Power, faster

Body coil transmit (high power) for pelvis and spine may limit some applications

RF Power ConsiderationsRF Power ConsiderationsGood NewsBad News

RF power increases at 3.0T - T1 SE and FSE are high power sequences

Most joints are small involume - limits powerdeposition (T/R coils)

Lowering flip angle of refocusing pulses in FSE can decrease RF power, at the cost of some SNR

Fat Suppression at 3.0TFat Suppression at 3.0TGood NewsBad News

More difficult at 3.0Tdue to field inhomogeneity

Fat sat pulses are shorterat 3.0T (shift of 440 Hz)

Shorter sat pulses:-more slices per TR-faster SPGR imaging

Brachial Plexus: IDEALBrachial Plexus: IDEAL

FatFat--Sat FSESat FSE IDEAL FSEIDEAL FSE

Rapid Knee ProtocolRapid Knee Protocol

• Use: Routine knee imaging• Goal: Keep imaging time to a minimum

while having acceptable quality• Possible to scan a knee in 15 min with

table turn around

•• Use: Routine knee imagingUse: Routine knee imaging•• Goal: Keep imaging time to a minimum Goal: Keep imaging time to a minimum

while having acceptable qualitywhile having acceptable quality•• Possible to scan a knee in 15 min with Possible to scan a knee in 15 min with

table turn aroundtable turn around

Rapid Knee ProtocolRapid Knee Protocol• Axial PD FSE• TR/TE = 5000/35• Fat saturation• 4.0 / 1.0 mm• 320x224, 1 nex• 14 cm FOV• 26 slices• ETL = 8• 32 kHz BW• ARC 1.8

•• Axial PD FSEAxial PD FSE•• TR/TE = 5000/35TR/TE = 5000/35•• Fat saturationFat saturation•• 4.0 / 1.0 mm4.0 / 1.0 mm•• 320x224, 1 nex320x224, 1 nex•• 14 cm FOV14 cm FOV•• 26 slices26 slices•• ETL = 8ETL = 8•• 32 kHz BW32 kHz BW•• ARC 1.8ARC 1.8

Rapid Knee ProtocolRapid Knee Protocol• Coronal T1 FSE• TR/TE = 1000/20• No Fat saturation• 4/1 mm• 384x224, 1 nex• 16 cm FOV• 18 slices• ETL = 4• 32 kHz BW• ARC 1.8

•• Coronal T1 FSECoronal T1 FSE•• TR/TE = 1000/20TR/TE = 1000/20•• No Fat saturationNo Fat saturation•• 4/1 mm4/1 mm•• 384x224, 1 nex384x224, 1 nex•• 16 cm FOV16 cm FOV•• 18 slices18 slices•• ETL = 4ETL = 4•• 32 kHz BW32 kHz BW•• ARC 1.8ARC 1.8

Rapid Knee ProtocolRapid Knee Protocol• Coronal T2 FSE• TR/TE = 4000/54• Fat saturation• 4/1 mm• 320x224, 1 nex• 16 cm FOV• 22 slices• ETL = 8• 32 kHz BW• ARC 1.8

•• Coronal T2 FSECoronal T2 FSE•• TR/TE = 4000/54TR/TE = 4000/54•• Fat saturationFat saturation•• 4/1 mm4/1 mm•• 320x224, 1 nex320x224, 1 nex•• 16 cm FOV16 cm FOV•• 22 slices22 slices•• ETL = 8ETL = 8•• 32 kHz BW32 kHz BW•• ARC 1.8ARC 1.8

Rapid Knee ProtocolRapid Knee Protocol• Sagittal PD FSE• TR/TE = 5000/35• No fat saturation• 3.0/0.5 mm• 384x224, 1 nex• 14 cm FOV• 30 slices• ETL = 8• 32 kHz BW• ARC - none

•• Sagittal PD FSESagittal PD FSE•• TR/TE = 5000/35TR/TE = 5000/35•• No fat saturationNo fat saturation•• 3.0/0.5 mm3.0/0.5 mm•• 384x224, 1 nex384x224, 1 nex•• 14 cm FOV14 cm FOV•• 30 slices30 slices•• ETL = 8ETL = 8•• 32 kHz BW32 kHz BW•• ARC ARC -- nonenone

Rapid Knee ProtocolRapid Knee Protocol• Sagittal T2 FSE• TR/TE = 6400/60• No fat saturation• 3.0/0.5 mm• 320x224, 1 nex• 14 cm FOV• 30 slices• ETL = 10• 32 kHz BW• Flow Comp, SI Sat

•• Sagittal T2 FSESagittal T2 FSE•• TR/TE = 6400/60TR/TE = 6400/60•• No fat saturationNo fat saturation•• 3.0/0.5 mm3.0/0.5 mm•• 320x224, 1 nex320x224, 1 nex•• 14 cm FOV14 cm FOV•• 30 slices30 slices•• ETL = 10ETL = 10•• 32 kHz BW32 kHz BW•• Flow Comp, SI SatFlow Comp, SI Sat

Scan Time ComparisonScan Time ComparisonSequence 1.5T (nex) 3.0T (nex)

Axial PD 3:10 (2) 1:25 (1)

Cor T1 5:10 (2) 1:43 (1)

Cor T2 3:10 (2) 2:24 (1)

Sag PD 4:16 (2) 2:30 (1)

Sag T2 4:48 (3) 2:40 (1)

Total 20:34 10:42

3.0T: Resolution Advantage3.0T: Resolution Advantage

High Resolution Knee ProtocolHigh Resolution Knee Protocol

• Use: High quality knee imaging• Goal: Keep imaging time to about 30-

45 min while having outstanding quality

• Possible to scan a knee in 45 min with table turn around

• 8 channel knee coil

•• Use: High quality knee imagingUse: High quality knee imaging•• Goal: Keep imaging time to about 30Goal: Keep imaging time to about 30--

45 min while having outstanding 45 min while having outstanding qualityquality

•• Possible to scan a knee in 45 min with Possible to scan a knee in 45 min with table turn aroundtable turn around

•• 8 channel knee coil8 channel knee coil

High Resolution Knee ProtocolHigh Resolution Knee Protocol

• Axial PD FSE• TR/TE = 5000/20• Fat saturation• 2.5/0.5mm• 416 x 320• 2 averages• 14 cm FOV• 26 slices• ETL = 8• 32 kHz BW

•• Axial PD FSEAxial PD FSE•• TR/TE = 5000/20TR/TE = 5000/20•• Fat saturationFat saturation•• 2.5/0.5mm2.5/0.5mm•• 416 x 320416 x 320•• 2 averages2 averages•• 14 cm FOV14 cm FOV•• 26 slices26 slices•• ETL = 8ETL = 8•• 32 kHz BW32 kHz BW

• Coronal T1 FSE• TR/TE = 1000/15• No Fat saturation• 2.5/0.5 mm• 416 x 320• 2 averages• 14 cm FOV• 18 slices• ETL = 3• 41 kHz BW

•• Coronal T1 FSECoronal T1 FSE•• TR/TE = 1000/15TR/TE = 1000/15•• No Fat saturationNo Fat saturation•• 2.5/0.5 mm2.5/0.5 mm•• 416 x 320416 x 320•• 2 averages2 averages•• 14 cm FOV14 cm FOV•• 18 slices18 slices•• ETL = 3ETL = 3•• 41 kHz BW41 kHz BW

High Resolution Knee ProtocolHigh Resolution Knee Protocol

• Coronal T2 FSE• TR/TE = 5000/60• Fat saturation• 2.5/0.5 mm• 416 x 320• 2 averages• 14 cm FOV• 22 slices• ETL = 8• 32 kHz BW

•• Coronal T2 FSECoronal T2 FSE•• TR/TE = 5000/60TR/TE = 5000/60•• Fat saturationFat saturation•• 2.5/0.5 mm2.5/0.5 mm•• 416 x 320416 x 320•• 2 averages2 averages•• 14 cm FOV14 cm FOV•• 22 slices22 slices•• ETL = 8ETL = 8•• 32 kHz BW32 kHz BW

High Resolution Knee ProtocolHigh Resolution Knee Protocol

• Sagittal PD FSE• TR/TE = 5000/15• No fat saturation• 2.5/0.5 mm• 512 x 320• 1.5 averages• 16 cm FOV• 30 slices• ETL = 8• 41 kHz BW

•• Sagittal PD FSESagittal PD FSE•• TR/TE = 5000/15TR/TE = 5000/15•• No fat saturationNo fat saturation•• 2.5/0.5 mm2.5/0.5 mm•• 512 x 320512 x 320•• 1.5 averages1.5 averages•• 16 cm FOV16 cm FOV•• 30 slices30 slices•• ETL = 8ETL = 8•• 41 kHz BW41 kHz BW

High Resolution Knee ProtocolHigh Resolution Knee Protocol

• Sagittal T2 FSE• TR/TE = 5000/54• Fat saturation• 2.5/0.5 mm• 384 x 320• 1.5 averages• 16 cm FOV• 30 slices• ETL = 8• 32 kHz BW• Flow Comp, S Sat

•• Sagittal T2 FSESagittal T2 FSE•• TR/TE = 5000/54TR/TE = 5000/54•• Fat saturationFat saturation•• 2.5/0.5 mm2.5/0.5 mm•• 384 x 320384 x 320•• 1.5 averages1.5 averages•• 16 cm FOV16 cm FOV•• 30 slices30 slices•• ETL = 8ETL = 8•• 32 kHz BW32 kHz BW•• Flow Comp, S SatFlow Comp, S Sat

High Resolution Knee ProtocolHigh Resolution Knee Protocol

• Coronal 3D FSE• TR/TE = 3000/35• Fat saturation• 0.6 mm slices• 288 x 288• 1.5 averages• 17 cm FOV• 200 slices• ETL = 60• 62 kHz BW• Reformat at 2 mm slices

•• Coronal 3D FSECoronal 3D FSE•• TR/TE = 3000/35TR/TE = 3000/35•• Fat saturationFat saturation•• 0.6 mm slices0.6 mm slices•• 288 x 288288 x 288•• 1.5 averages1.5 averages•• 17 cm FOV17 cm FOV•• 200 slices200 slices•• ETL = 60ETL = 60•• 62 kHz BW62 kHz BW•• Reformat at 2 mm slicesReformat at 2 mm slices

High Resolution Knee ProtocolHigh Resolution Knee Protocol

High Resolution Scan Time ComparisonHigh Resolution Scan Time ComparisonSequence 1.5T (slice, mm) 3.0T (slice, mm)

Axial PD 3:10 (4) 6:00 (2.5)

Cor T1 5:10 (4) 3:30 (2.5)

Cor T2 3:10 (4) 6:00 (2.5)

Sag PD 4:16 (3) 5:00 (2.5)

Sag T2 4:48 (3.5) 5:00 (2.5)

Cor 3D FSE xx 5:00 (0.6)5:00 (0.6)

Total 20:34 30:30

Ankle at 3.0TAnkle at 3.0T

2.5 mm thick slices, 8-channel ankle coil

512x320, BW 41 kHz, ETL = 3 416x224, BW 31 kHz, ETL = 8

T1 FSE T2 FSE Fat Sat

Elbow at 3.0TElbow at 3.0T

2.5 mm thick slices, 8-channel knee coil

512x320, BW 41 kHz, ETL = 3 416x224, BW 31 kHz, ETL = 8

T1 FSE T2 FSE Fat Sat

Dedicated 3T Wrist CoilDedicated 3T Wrist Coil2 mm slices, 200 micron in-plane resolution

Use: MDCT Repetitive strain injuries

T2 IdealCor T2 FS

Adductor Strain3T

Shoulder at 3.0TShoulder at 3.0T

2 mm thick slices

3.0T uTE Cones 3.0T uTE Cones TE = 0.1 ms Log subtraction

uTE Imaging: 3D Cones

TE = 4.6 ms

Take-Home PointsTake-Home Points• Use dedicated RF coils• Increased T1:

• Decrease averages• Increase TR• Decrease slice thickness

• Keep BW > +/-32 kHz on sequences without fat saturation

• Consider T1 FSE (short ETL) to reduce SAR

•• Use dedicated RF coilsUse dedicated RF coils•• Increased T1:Increased T1:

•• Decrease averagesDecrease averages•• Increase TRIncrease TR•• Decrease slice thicknessDecrease slice thickness

•• Keep BW > +/Keep BW > +/--32 kHz on sequences 32 kHz on sequences without fat saturationwithout fat saturation

•• Consider T1 FSE (short ETL) to Consider T1 FSE (short ETL) to reduce SARreduce SAR