Patients
Our study was approved by our institutional review board.
Informed consent was obtained from each patient.
We recruited 25 patients (11 men,
14 women; mean age,
45±16 years) with suspected acetabular labral injury.
MR imaging
All images were obtained on a 3T MR unit (Philips INGENIA 3.0T; gradient strength = 40 mT/m,
slew rate = 150 T/m/s) using ds Anterior and ds Posterior coil.
We optimized the 3D FS multi-echo GRE sequence (TR 32 ms,
TE 2.3/5.6/8.9/12.2/15.5 ms (5 echoes),
flip angle 7°,
FOV 350x280 mm (RFOV 80%),
matrix 352x282,
pixel size 1x1x1 (ZIP 0.5x0.5x0.5) mm,
number of acquisitions 1,
BW 538 Hz/pixel,
SPIR (CHESS) +,
scan time 5 m 30 s) and radial 2D T2*WI sequence (TR 400 ms,
TE 18.4 ms,
flip angle 30°,
FOV 160x160 mm,
matrix 320x320,
slice thickness 4 mm,
pixel size 0.5x0.5 mm,
number of acquisitions 2,
BW 517 Hz/pixel,
slice numbers 12,
scan time 5 m 25 s).
Radial T2*WI through the center of the acetabulum perpendicular to the plane across the entire acetabular rim of the right hip joints of 15 patients and the left hip joints of 10 patients and axial 3D FS multi-echo GRE imaging of their both hips were acquired.
Radial reformation methods of FS multi-echo GRE for evaluating acetabular labral injuries and FAI
We performed type-1 radial reformation through the center of the acetabulum perpendicular to the plane across the entire acetabular rim at 15° slice intervals for evaluating acetabular labral injury (Fig.
1a) and type-2 radial reformation perpendicular to the central axis of the femoral head and neck at 15° slice intervals for evaluating FAI (Fig.
1b).
The diagnostic accuracy of acetabular labral injury using type-1 radial reformation
The range of acetabular labral injury of each patient was evaluated by the consensus decision of two experienced radiologists.
Two weeks after interpreting radial 2D T2*WI,
the same radiologists evaluated labral injury on type-1 radial reformation of 3D FS multi-echo GRE imaging.
Diagnostic accuracy using the type-1 radial reformation was assessed in comparison with radial 2D T2*WI.
The locations of acetabular labral injury were classified as eight zones (anterior,
anterosuperior,
superior,
posterosuperior,
posterior,
inferoposterior,
and inferior zones).
The evaluation of FAI using type-2 radial reformation
The degree of FAI morphology was estimated using type-2 radial reformation of 3D FS multi-echo GRE imaging.
FAI was diagnosed based on previously published methods (Fig.
2a,b).
An α angle over 55° was considered indicative of cam-type FAI [4,
5].
Pincer-type FAI was diagnosed based on over-coverage of the acetabulum.
Acetabular depth < 0 was defined as pincer-type FAI [6].