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Keywords:
Musculoskeletal joint, Extremities, MR, Imaging sequences, Comparative studies
Authors:
R. V. D. van der Heijden, P. P. Vissers, E. Bron, S. Klein, J. Verhaar, G. P. Krestin, S. M. A. Bierma-Zeinstra, M. van Middelkoop, E. Oei; Rotterdam/NL
DOI:
10.1594/ecr2015/C-0754
Methods and materials
Patients diagnosed with PFP and healthy control subjects aged 14-40 years were included in a cross-sectional case-control study.
Measures included a questionnaire,
physical examination and MRI.
MRI was performed on a 3T MRI scanner (Discovery MR750,
GE Healthcare,
Milwaukee,
USA),
using a dedicated 8-channel knee coil.
The image protocol consisted of high resolution 3D SPGR sequence and 3D fast spin-echo T1ρ and T2 mapping sequences.
Images in the T1ρ mapping protocol were acquired with spin lock times (TSLs) of 1,
16,
32,
64 and 125 milliseconds.
The total duration of the T1ρ protocol was approximately 10 minutes.
T2 mapping MR images were acquired with multiple echo times of 3,
13,
27,
40 and 68 milliseconds,
with total scan time of 6 minutes.
The regions of interests (ROI) consisted of the whole patellar cartilage and the whole trochlear cartilage.
The ROIs were drawn by a trained investigator for each participant on the high-resolution SPGR images (Fig. 1) with Matlab (R2011a,
The MathWorks,
Natick,
MA,
USA).
In house-developed software (Software for Post-processing and Registration of Cartilage of the Knee: SPARCK) [10] was used for image registration,
to correct for patient motion during acquisition of the MRI images,
and to calculate T1ρ and T2 relaxation times (Fig. 2).
T1ρ relaxation time is sensitive for the concentration of GAGs,
a high T1ρ relaxation time suggests decreased concentration of GAGs in cartilage [6].
An increased T2 relaxation time is the result of an decreased interaction between the water – and macromolecules,
caused by a loss of collagen content in the cartilage [6].
Differences in T1ρ and T2 relaxation times for trochlear and patellar cartilage were compared between patients and control subjects by linear regression analyses,
adjusted for potential confounders.