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DOI: 10.1148/radiol.2381042183
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Articular Cartilage of the Knee: Evaluation with Fluctuating Equilibrium MR Imaging—Initial Experience in Healthy Volunteers1

Garry E. Gold, MD, Brian A. Hargreaves, PhD, Shreyas S. Vasanawala, MD, PhD, Joshua D. Webb, MS, Ann S. Shimakawa, MS, Jean H. Brittain, PhD and Christopher F. Beaulieu, MD, PhD

1 From the Departments of Radiology (G.E.G., S.S.V., C.F.B.), Electrical Engineering (B.A.H.), and Mechanical Engineering (J.D.W.), Stanford University, 300 Pasteur Dr, SO-68B, Stanford, CA 94305-5105; and GE Applied Sciences West Laboratory, Menlo Park, Calif (A.S.S., J.H.B.). Received December 23, 2004; revision requested February 23, 2005; revision received March 21; final version accepted April 15. Supported by NIH grant EB002524-01 and the Whitaker Foundation. Address correspondence to G.E.G. (e-mail: gold{at}stanford.edu).


Figure 1
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  		Figure 1: Bar graph shows cartilage SNR efficiency values for fluctuating equilibrium (FEMR), 2D fast SE, and 3D SPGR MR imaging sequences. SNR efficiency is SNR divided by the square root of the imaging time. The cartilage SNR efficiency was significantly higher for the fluctuating equilibrium sequence (* = P < .01) than for both the 3D SPGR and the 2D fast SE sequences. The cartilage SNR efficiency for the 3D SPGR sequence was significantly higher than that for the 2D fast SE sequence (** = P < .01). Error bars indicate standard deviations.

 

Figure 2
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  		Figure 2: Bar graph shows cartilage-fluid CNR efficiency values for fluctuating equilibrium (FEMR), 2D fast SE, and 3D SPGR MR imaging sequences. The cartilage-fluid CNR efficiency was significantly higher for the fluctuating equilibrium sequence than for either the 3D SPGR or the 2D fast SE sequence (* = P < .01). The cartilage-fluid CNR efficiency for the 2D fast SE sequence was significantly higher than that for the 3D SPGR sequence (** = P < .01). Error bars indicate standard deviations.

 

Figure 3
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  		Figure 3a: (a) Sagittal fluctuating equilibrium MR water image (6.6/1.8; flip angle, 25°) and (b) lipid image (6.6/1.8; flip angle, 25°) in healthy 29-year-old female volunteer. The signal intensity of fluid (arrow) is high compared with the signal intensity of the articular cartilage.

 

Figure 3
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  		Figure 3b: (a) Sagittal fluctuating equilibrium MR water image (6.6/1.8; flip angle, 25°) and (b) lipid image (6.6/1.8; flip angle, 25°) in healthy 29-year-old female volunteer. The signal intensity of fluid (arrow) is high compared with the signal intensity of the articular cartilage.

 

Figure 4
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  		Figure 4a: (a) Sagittal 3D SPGR (40/7; flip angle, 40°), (b) 2D fast SE (5000/41; echo train length, eight), (c) fluctuating equilibrium MR water (6.6/1.8; flip angle, 25°), and (d) fluctuating equilibrium MR lipid (6.6/1.8; flip angle, 25°) images in healthy 26-year-old female volunteer. An area of poor fat and water separation (solid arrow), as well as a banding artifact (dashed arrow), is seen near the patella on c.

 

Figure 4
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  		Figure 4b: (a) Sagittal 3D SPGR (40/7; flip angle, 40°), (b) 2D fast SE (5000/41; echo train length, eight), (c) fluctuating equilibrium MR water (6.6/1.8; flip angle, 25°), and (d) fluctuating equilibrium MR lipid (6.6/1.8; flip angle, 25°) images in healthy 26-year-old female volunteer. An area of poor fat and water separation (solid arrow), as well as a banding artifact (dashed arrow), is seen near the patella on c.

 

Figure 4
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  		Figure 4c: (a) Sagittal 3D SPGR (40/7; flip angle, 40°), (b) 2D fast SE (5000/41; echo train length, eight), (c) fluctuating equilibrium MR water (6.6/1.8; flip angle, 25°), and (d) fluctuating equilibrium MR lipid (6.6/1.8; flip angle, 25°) images in healthy 26-year-old female volunteer. An area of poor fat and water separation (solid arrow), as well as a banding artifact (dashed arrow), is seen near the patella on c.

 

Figure 4
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  		Figure 4d: (a) Sagittal 3D SPGR (40/7; flip angle, 40°), (b) 2D fast SE (5000/41; echo train length, eight), (c) fluctuating equilibrium MR water (6.6/1.8; flip angle, 25°), and (d) fluctuating equilibrium MR lipid (6.6/1.8; flip angle, 25°) images in healthy 26-year-old female volunteer. An area of poor fat and water separation (solid arrow), as well as a banding artifact (dashed arrow), is seen near the patella on c.

 

Figure 5
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  		Figure 5a: Bar graphs show comparison of cartilage volume measurements between fluctuating equilibrium (FEMR) and 3D SPGR MR imaging sequences. (a) Graph shows comparison between fluctuating equilibrium and 3D SPGR measurements and actual measured cartilage volume in the phantom. Error bars indicate standard deviations. (b) Graph shows comparison of cartilage volume as measured with each sequence in the femurs of 10 healthy volunteers. There were no significant differences between cartilage volumes measured with the fluctuating equilibrium sequence and those measured with the 3D SPGR sequence in the femur, tibia, and patella (P > .5, paired t test).

 

Figure 5
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  		Figure 5b: Bar graphs show comparison of cartilage volume measurements between fluctuating equilibrium (FEMR) and 3D SPGR MR imaging sequences. (a) Graph shows comparison between fluctuating equilibrium and 3D SPGR measurements and actual measured cartilage volume in the phantom. Error bars indicate standard deviations. (b) Graph shows comparison of cartilage volume as measured with each sequence in the femurs of 10 healthy volunteers. There were no significant differences between cartilage volumes measured with the fluctuating equilibrium sequence and those measured with the 3D SPGR sequence in the femur, tibia, and patella (P > .5, paired t test).

 

Figure 6
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  		Figure 6a: Example of cartilage segmentation performed by using fluctuating equilibrium MR imaging in healthy 32-year-old male volunteer. Cartilage surfaces on the femur (red), patella (yellow), and tibia (blue) are all well seen.

 

Figure 6
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  		Figure 6b: Example of cartilage segmentation performed by using fluctuating equilibrium MR imaging in healthy 32-year-old male volunteer. Cartilage surfaces on the femur (red), patella (yellow), and tibia (blue) are all well seen.

 




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