Susanne Eijgenraam^{1}, Akshay Chaudhari^{2}, Max Reijman^{3}, Edwin Oei^{1}, Brian Hargreaves^{2}, and Garry Gold^{2}

In
this study, we investigated quantitative and semi-quantitative MR imaging biomarkers
of knee OA, obtained with a **5-minute DESS sequence**, in increasing stages of **knee
OA**. 54
patients were included: 20 patients with no knee
OA, 18 patients with mild knee OA and 16 patients with moderate
knee OA. All patients were
scanned using DESS and a routine clinical knee MRI protocol. Simultaneous
quantitative T2 and morphological assessment of cartilage and meniscus with a
5-minute DESS-sequence showed consistent outcomes with increasing stages of
degeneration, making this sequence a useful tool for OA research.

54 patients were
included and divided in three groups, based on their radiographic degree of
knee OA according to Kellgren-Lawrence (KL): 20 patients with no knee OA (KL
grade 0), 18 patients with mild knee OA (KL 2) and 16 patients with moderate
knee OA (KL 3). All patients were
scanned using DESS (Fig. 1) and a routine clinical knee MRI protocol. DESS echo
signals were acquired separately to enable T2 fitting7 and sequence parameters are shown in Table 1. MOAKS was
performed by a researcher experienced in musculoskeletal MRI using only the
DESS images (with multi-planar reformatting). Mean T2 values of cartilage (femur
and tibia, medial and lateral) and meniscus (medial and lateral) were
calculated on single slices (Fig 2), using in-house developed post-processing
software (Matlab R2011b;
The Math-Works, Natick, MA, USA). The T2 values were calculated using the
following analytical expression (where a is the flip angle), assuming a T1 of 1200 ms. for cartilage and a T1 of
1000 ms. for meniscus^{6,7}:

$$\frac{S-}{S+}=e^{-\frac{2(\mathrm{TR}-\mathrm{TE})}{T_2}} \sin^2{\left(\frac{\alpha}{2}\right)}\left(\frac{1+e^{-\frac{\mathrm{TR}}{T_1} }}{1-\cos{\alpha} e^{-\frac{\mathrm{TR}}{T_1}}}\right)$$

Statistical testing between KL-groups was performed with one-way ANOVA tests, using an alpha of 0.05. Correlation between T2 values and MOAKS was assessed using a linear regression model.

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2. Zarins ZA, Bolbos RI, Pialat JB, et al.: Cartilage and meniscus assessment using T1rho and T2 measurements in healthy subjects and patients with osteoarthritis. Osteoarthr Cartil 2010; 18:1408–1416.

3. Rauscher I, Stahl R, Cheng J, et al.: Meniscal measurements of T1rho and T2 at MR imaging in healthy subjects and patients with osteoarthritis. Radiology 2008; 249:591–600.

4. Baum T, Joseph GB, Karampinos DC, Jungmann PM, Link TM, Bauer JS: Cartilage and meniscal T2 relaxation time as non-invasive biomarker for knee osteoarthritis and cartilage repair procedures. Osteoarthr Cartil 2013; 21:1474–84.

5. Peterfy CG, Schneider E, Nevitt M: The osteoarthritis initiative: report on the design rationale for the magnetic resonance imaging protocol for the knee. Osteoarthr Cartil 2008; 16:1433–1441.

6. Chaudhari, Akshay S., Black, Marianne S. Eijgenraam, Susanne, Wirth, Wolfgang, Maschek, Susanne, Sveinsson, Bragi, Eckstein, Felix, Oei, Edwin H. G., Gold, Garry E., Hargreaves, Brian A. 5-Minute Knee MRI for Simultaneous Morphometry and T2 Relaxometry of Cartilage and Meniscus and for Semi-Quantitative Radiological Assessment using Double-Echo in Steady-State at 3T. J Magn Reson Imaging 2017; (Early View)

7. Sveinsson B, Chaudhari A, Gold G, Hargreaves B: A simple analytic method for estimating T2 in the knee from DESS. Magn Reson Imaging 2017; 38:63–70.

Table 1. DESS
sequence parameters. Abbreviations: RO = readout, PE = phase encodes.

Table 2. Mean
T2-values of cartilage and menisci, obtained with DESS sequence. Abbreviations:
SD = standard deviation, OA = osteoarthritis, KL = Kellgren-Lawrence. *MOAKS sub-scores cartilage defects (size and
full-thickness).

Figure 1. Example
image obtained with DESS sequence (A) with coronal (B) and axial (C)
reconstruction.

Figure 2. Manual
segmentation of the medial meniscus, posterior horn using DESS sequence.