Two year longitudinal change and test-retest-precision of knee cartilage morphology in a pilot study for the osteoarthritis initiative

Abstract

Objective: Fast low angle shot (FLASH) and double echo steady state (DESS) magnetic resonance imaging (MRI) acquisitions were recently cross-calibrated for quantification of cartilage morphology at 3T. In this pilot study for the osteoarthritis (OA) initiative we compare their test-retest-precision and sensitivity to longitudinal change.

Method: Nine participants with mild to moderate clinical OA were imaged twice each at baseline, year 1 (Y1) and year 2 (Y2). Coronal 1.5mm FLASH and sagittal 0.7mm DESS sequences were acquired; 1.5mm coronal multiplanar reformats (MPR) were obtained from the DESS. Patellar, femoral and tibial cartilage plates were quantified in a paired fashion, with blinding to time point.

Results: In the weight-bearing femorotibial joint, average precision errors across plates were 1.8% for FLASH, 2.6% for DESS, and 3.0% for MPR-DESS. Volume loss at Y1 was not significant; at Y2 the average change across the femorotibial cartilage plates was -1.7% for FLASH, -2.8% for DESS, and -0.3% for MPR-DESS. Volume change in the lateral tibia (-5.5%; P<0.03), and in the medial (-2.9%; P<0.04) and lateral femorotibial compartments (-3.8%; P<0.03) were significant for DESS.

Conclusions: FLASH, DESS and MPR-DESS all displayed adequate test-retest precision. Although the comparison between protocols is limited by the small number of participants and by the relatively small longitudinal change in cartilage morphology in this pilot study, the data suggest that significant change can be detected with MRI in a small sample of OA subjects over 2 years.

Figure 1

MR images showing a baseline (left column) and year 2 acquisitions (right column) in one of the patients studied. The images highlight the challenge in delineating the articular surfaces of the tibial and femoral cartilages in the femoro-tibial contact areas: A) coronal double oblique FLASH with water excitation (1.5mm slice thickness), B) sagittal DESS with water excitation (0.7mm slice thickness through the medial femorotibial compartment), C) coronal double oblique multiplanar reconstruction of the sagittal DESS (1.5mm slice thickness). MT = medial tibia, LT = lateral tibia, cMF = central (weight-bearing) portion of the medial femoral condyle; pMF = posterior portion of the medial femoral condyle; cLF = central (weight-bearing) portion of the lateral femoral condyle; pMF = posterior portion of the medial femoral condyle