Usefulness of thin-slice 3D MR imaging using 3D FSE sequence with variable flip-angle refocusing RF pulses for assessing the popliteomeniscal fascicles of the lateral meniscus in knee MR imaging at 3T
Masayuki Odashima1, Tsutomu Inaoka1, Hideyasu Kudo1, Tomoya Nakatsuka1, Rumiko Ishikawa1, Shusuke Kasuya1, Noriko Kitamura1, Hiroyuki Nakazawa1, Koichi Nakagawa2, and Hitoshi Terada1

1Radiology, Toho University Sakura Medical Center, Sakura, Japan, 2Orthopedic Surgery, Toho University Sakura Medical Center, Sakura, Japan

Synopsis

Thin-slice 3D MR imaging of the knee joint using 3D FSE sequence with variable flip-angle refocusing RF pulses may improve the visualization of the three popliteomeniscal fascicles of the lateral meniscus in comparison with conventional 2D MR imaging of the knee joint.

Purpose

Currently, instability of the meniscus has been a topic in the field of knee disorders. Particularly in instability of the lateral meniscus, the popliteomeniscal fascicles (PMFs) that are three small structures connecting the posterior horn of the lateral meniscus to the capsule of the knee joint may be thought to contribute to stability of the lateral meniscus. It is, however, quite difficult to detect the PMFs by conventional 2D MR imaging of the knee joint using 2D sequences because of their small size and complicated angulation. Recently, it has been reported that thin-slice 3D MR imaging using 3D FSE sequence with variable flip-angle refocusing RF pulses is very useful for detecting intraarticular abnormalities of the knee joint. Therefore, the purpose of this study was to assess the usefulness of thin-slice 3D MR imaging of the knee joint using 3D FSE sequence with variable flip-angle refocusing RF pulses for detecting the three PMFs of the lateral meniscus.

Materials and methods

29 knees in 29 patients (19 males and 10 females; mean age, 49years) with no symptom in the lateral compartment of the knee and no abnormality in the lateral meniscus on knee MR images were included. All MR images of the knee joint were obtained by a 3T MR scanner (Magnetom Skyra, Siemens Healthcare) and a 15-channel knee coil. Conventional 2D MR images including sagittal T2-weighted images, sagittal T1-weighted images, sagittal T2*-weighted images, and coronal fat-suppressed PD-weighted images with 3-4mm thicknesses were obtained. In addition, coronal fat-suppressed PD-weighted images with 0.6 mm thicknesses were obtained by using 3D FSE sequence with variable flip-angle refocusing RF pulses (SPACE) and multiplanar-reformatted (MPR) images of 1mm thickness were generated (thin-slice 3D MR images). The presence or absence of the three PMFs (posterosuperior, posteroinferior, and anteroinferior PMFs) were assessed by two radiologists. The percentages of the presence of the PMFs of the lateral meniscus were calculated on conventional 2D MR images and thin-slice 3D MR images. Regarding the anteroinferior PMF, MPR images were used to measure the angle of the posterior surface of the bilateral femoral condyles and anteroinferior PMF.

Results

Posterosuperior, posteroinferior, and anteroinferior PMFs were found in 16/29(55%), 12/29(41%), and 4/29(14%) on conventional 2D MR images and in 23/29(79%), 17/29(59%), and 28/29(97%) on thin-slice 3D MR images, respectively. In particular, the anteroinferior PMF was almost always found on thin-slice 3D MR images (P<0.05). The average angle of the posterior surface of the bilateral femoral condyles and anteroinferior PMF was 42 degree.

Discussion

Previous study using oblique sagittal 2D PD-weighted images (3mm) of knee MRI at 1.5T reported that anteroinferior and posterosuperior PMFs were found in 65-94% and 50-88%, respectively. Another study using 10 cadavaric knees obtained by 1.5T MRI reported that anteroinferior, posterosuperior, and posteroinferior PMFs were found in 100%, 40%, and 100%, respectively. In our study, the results from thin-slice 3D MR imaging are similar to those in the previous study using cadaveric knees. Interestingly, the anteroinferior PMF was almost always found by thin-slice 3D MR imaging.

Conclusion

Thin-slice 3D MR imaging of the knee joint using 3D FSE sequence with variable flip-angle refocusing RF pulses may improve the visualization of the three PMFs of the lateral meniscus in comparison with conventional 2D MR imaging of the knee joint.

Acknowledgements

No acknowledgement found.

References

1) Suganuma J, Mochizuki R, Inoue Y, et al. Magnetic resonance imaging and arthroscopic findings of the popliteomeniscal fascicles with and without recurrent subluxation of the lateral meniscus. Arthroscopy. 2012;28(4):507-516. 2) Kudo H, Inaoka T, Kitamura N, et al. Clinical value of routine use of thin-section 3D MRI using 3D FSE sequences with a variable flip angle technique for internal derangements of the knee joint at 3T. Magn Reson Imaging. 2013;31(8):1309-1317. 3) Sakai H, Sasho T, Wada Y, et al. MRI of the popliteomeniscal fasciculi. AJR Am J Roetgenol. 2006;186(2):460-466. 4) Peduto AJ, Nguyen A, Trudel lDJ,et al. Popliteomeniscal fascicles: anatomic considerations using MR arthrography in cadavers. AJR Am J Roentgenol. 2008;190(2):4420448.

Figures

conventional 2D MR imaging versus thin-slice 3D MR imaging of the three popliteomeniscal fascicles (PMFs)

Posterosuperior, posteroinferior, and anteroinferior PMFs were found in 16/29(55%), 12/29(41%), and 4/29(14%) on conventional 2D MR images and in 23/29(79%), 17/29(59%), and 28/29(97%) on thin-slice 3D MR images, respectively. In particular, the anteroinferior PMF was almost always found on thin-slice 3D MR images (P<0.05).



Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)
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