Rapid MR Imaging of Articular Cartilage with Steady-State Free Precession and Multipoint Fat-Water Separation
Scott B. Reeder1,
Norbert J. Pelc1,
Marcus T. Alley1 and
Garry E. Gold1,2
1 Department of Radiology, Stanford University Medical Center, 300 Pasteur Ave.,
Rm. H1306, Stanford, CA 94304.
2 Department of Radiology, Veterans Affairs Palo Alto Health Care System, 3801
Miranda Ave., Palo Alto, CA 94304.
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Fig. 1A. —Sagittal steady-state free precession (SSFP) images of right
knee of healthy 32-year-old man obtained with two different TR values. SSFP
image was obtained with parameters of TR/TE, 6.1/ 1.16.
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Fig. 1B. —Sagittal steady-state free precession (SSFP) images of right
knee of healthy 32-year-old man obtained with two different TR values. In SSFP
image obtained with 6.6/1.16, marked signal dropout is seen throughout bone
marrow, resulting from local field inhomogeneities that disrupt SSFP coherence
at longer TR.
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Fig. 2A. —Sagittal images of right knee of healthy 32-year-old man
obtained through lateral femoral condyle. Image is derived from average of
magnitude of four steady-state free precession (SSFP) source images acquired
at four TE settings—1.16, 2.08, 3.00, and 3.92—and TR of 6.14.
Resulting images display excellent fat separation and visualization of
cartilage, and synovial fluid appears extremely bright.
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Fig. 2B. —Sagittal images of right knee of healthy 32-year-old man
obtained through lateral femoral condyle. Both B (water image) and
C (fat image) were calculated using equation 3 (in Appendix 1) from
four source SSFP images and estimates of the off-resonance map calculated with
the modified local orientation filter. Arrows (B) indicate joint
fluid.
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Fig. 2C. —Sagittal images of right knee of healthy 32-year-old man
obtained through lateral femoral condyle. Both B (water image) and
C (fat image) were calculated using equation 3 (in Appendix 1) from
four source SSFP images and estimates of the off-resonance map calculated with
the modified local orientation filter. Arrows (B) indicate joint
fluid.
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Fig. 2D. —Sagittal images of right knee of healthy 32-year-old man
obtained through lateral femoral condyle. Fat-saturated spoiled gradient-echo
image obtained through same slice as A—C shows excellent
visualization of articular cartilage, although fat-saturation is not uniform
and synovial fluid has intermediate to low signal intensity, making it
difficult to see.
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Fig. 3A. —Axial images obtained through patellofemoral joint of left
knee of 39-year-old man volunteer with known cartilage abnormalities.
Steady-state free precession water image shows bright synovial fluid
(arrows) intercalated between femoral and patellar cartilage. Long T2
results in high signal intensity of fluid.
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Fig. 3B. —Axial images obtained through patellofemoral joint of left
knee of 39-year-old man volunteer with known cartilage abnormalities. In
fat-saturated spoiled gradient-echo MR image corresponding to A, joint
fluid displays low to intermediate signal intensity resulting from long T1.
Note chemical shift at fat—water interfaces (arrows)
perpendicular to readout (anterior—posterior) direction.
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Fig. 4A. —Sagittal images obtained through lateral femoral condyle in
left knee of 39-year-old man with titanium fixation screw (arrow) in
anterior cruciate ligament. Both steady-state free precession (SSFP) and
spoiled gradient-echo show comparable signal deficits in vicinity of fixation
hardware. Image derived from average of magnitude of four source SSFP images
acquired at four TE settings—1.16, 2.08, 3.00, and 3.92 msec.
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Fig. 4B. —Sagittal images obtained through lateral femoral condyle in
left knee of 39-year-old man with titanium fixation screw (arrow) in
anterior cruciate ligament. Both steady-state free precession (SSFP) and
spoiled gradient-echo show comparable signal deficits in vicinity of fixation
hardware. Both B (water image) and C (fat image) were calculated
using equation 3 in Appendix 1 from four source SSFP images and estimates of
off-resonance map calculated with the modified local orientation filter.
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Fig. 4C. —Sagittal images obtained through lateral femoral condyle in
left knee of 39-year-old man with titanium fixation screw (arrow) in
anterior cruciate ligament. Both steady-state free precession (SSFP) and
spoiled gradient-echo show comparable signal deficits in vicinity of fixation
hardware. Both B (water image) and C (fat image) were calculated
using equation 3 in Appendix 1 from four source SSFP images and estimates of
off-resonance map calculated with the modified local orientation filter.
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Copyright © 2003 by the American Roentgen Ray Society.
