Detection of knee synovitis using non-contrast-enhanced qDESS compared with contrast-enhanced MRI.

BACKGROUND: To assess diagnostic accuracy of quantitative double-echo in steady-state (qDESS) MRI for detecting synovitis in knee osteoarthritis (OA). METHODS: Patients with different degrees of radiographic knee OA were included prospectively. All underwent MRI with both qDESS and contrast-enhanced T1-weighted magnetic resonance imaging (CE-MRI). A linear combination of the two qDESS images can be used to create an image that displays contrast between synovium and the synovial fluid. Synovitis on both qDESS and CE-MRI was assessed semi-quantitatively, using a whole-knee synovitis sum score, indicating no/equivocal, mild, moderate, and severe synovitis. The correlation between sum scores of qDESS and CE-MRI (reference standard) was determined using Spearman's rank correlation coefficient and intraclass correlation coefficient for absolute agreement. Receiver operating characteristic analysis was performed to assess the diagnostic performance of qDESS for detecting different degrees of synovitis, with CE-MRI as reference standard. RESULTS: In the 31 patients included, very strong correlation was found between synovitis sum scores on qDESS and CE-MRI (ρ = 0.96, p < 0.001), with high absolute agreement (0.84 (95%CI 0.14-0.95)). Mean sum score (SD) values on qDESS 5.16 (3.75) were lower than on CE-MRI 7.13 (4.66), indicating systematically underestimated synovitis severity on qDESS. For detecting mild synovitis or higher, high sensitivity and specificity were found for qDESS (1.00 (95%CI 0.80-1.00) and 0.909 (0.571-1.00), respectively). For detecting moderate synovitis or higher, sensitivity and specificity were good (0.727 (95%CI 0.393-0.927) and 1.00 (0.800-1.00), respectively). CONCLUSION: qDESS MRI is able to, however with an underestimation, detect synovitis in patients with knee OA.

Quantitative volume and dynamic contrast-enhanced MRI derived perfusion of the infrapatellar fat pad in patellofemoral pain.

BACKGROUND: Patellofemoral pain (PFP) is a common knee condition and possible precursor of knee osteoarthritis (OA). Inflammation, leading to an increased perfusion, or increased volume of the infrapatellar fat pad (IPFP) may induce knee pain. The aim of the study was to compare quantitative dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) parameters, as imaging biomarkers of inflammation, and volume of the IPFP between patients with PFP and controls and between patients with and without IPFP edema or joint effusion. METHODS: Patients with PFP and healthy controls were included and underwent non-fat suppressed 3D fast-spoiled gradient-echo (FSPGR) and DCE-MRI. Image registration was applied to correct for motion. The IPFP was delineated on FSPGR using Horos software. Volume was calculated and quantitative perfusion parameters were extracted by fitting extended Tofts' pharmacokinetic model. Differences in volume and DCE-MRI parameters between patients and controls were tested by linear regression analyses. IPFP edema and effusion were analyzed identically. RESULTS: Forty-three controls and 35 PFP patients were included. Mean IPFP volume was 26.04 (4.18) mL in control subjects and 27.52 (5.37) mL in patients. Median Ktrans was 0.017 (0.016) min-1 in control subjects and 0.016 (0.020) min-1 in patients. None of the differences in volume and perfusion parameters were statistically significant. Knees with effusion showed a higher perfusion of the IPFP compared to knees without effusion in patients only. CONCLUSIONS: The IPFP has been implicated as source of knee pain, but higher DCE-MR blood perfusion, an imaging biomarker of inflammation, and larger volume are not associated with PFP. Patient's knees with effusion showed a higher perfusion, pointing towards inflammation.

Diagnostic accuracy of grayscale, power Doppler and contrast-enhanced ultrasound compared with contrast-enhanced MRI in the visualization of synovitis in knee osteoarthritis.

PURPOSE: To assess the diagnostic accuracy of grayscale (GSUS), power Doppler (PDUS) and contrast-enhanced ultrasound (CEUS) for detecting synovitis in knee osteoarthritis (OA). METHOD: Patients with different degrees of radiographic knee OA were included prospectively. All underwent GSUS, PDUS, CEUS, and contrast-enhanced magnetic resonance imaging (CE-MRI), on which synovitis was assessed semi-quantitatively. Correlations of synovitis severity on ultrasound based techniques with CE-MRI were determined. Receiver operating characteristic (ROC) analysis was performed to assess diagnostic performance of GSUS, PDUS, and CEUS, for detecting synovitis, using CE-MRI as reference-standard. RESULTS: In the 31 patients included, synovitis scoring on GSUS and CEUS was significantly correlated (ρ = 0.608, p < 0.001 and ρ = 0.391, p = 0.033) with CE-MRI. For detecting mild synovitis, the area under the curve (AUC) was 0.781 (95 %CI 0.609-0.953) for GSUS, 0.788 (0.622-0.954) for PDUS, and 0.653 (0.452-0.853) for CEUS. Sensitivity and specificity were 0.667 (0.431-0.845) and 0.700 (0.354-0.919) for GSUS, 0.905 (0.682-0.983) and 0.500 (0.201-0.799) for PDUS, and 0.550 (0.320-0.762) and 0.700 (0.354-0.919) for CEUS, respectively. The AUC of GSUS increased to 0.862 (0.735-0.989), 0.823 (0.666-0.979), and 0.885 (0.767-1.000), when combined with PDUS, CEUS, or both, respectively. For detecting moderate synovitis, the AUC of GSUS was higher (0.882 (0.750-1.000)) and no added value of PDUS and CEUS was observed. CONCLUSIONS: GSUS has limited overall accuracy for detecting synovitis in knee OA. When GSUS is combined with PDUS or CEUS, overall diagnostic performance improves for detecting mild synovitis, but not for moderate synovitis.

Tissue-Specific T2 * Biomarkers in Patellar Tendinopathy by Subregional Quantification Using 3D Ultrashort Echo Time MRI.

BACKGROUND: Quantitative MRI of patellar tendinopathy (PT) can be challenging due to spatial variation of T2 * relaxation times. PURPOSE: 1) To compare T2 * quantification using a standard approach with analysis in specific tissue compartments of the patellar tendon. 2) To evaluate test-retest reliability of different methods for fitting ultrashort echo time (UTE)-relaxometry data. STUDY TYPE: Prospective. SUBJECTS: Sixty-five athletes with PT. FIELD STRENGTH/SEQUENCE: 3D UTE scans covering the patellar tendon were acquired using a 3.0T scanner and a 16-channel surface coil. ASSESSMENT: Voxelwise median T2 * was quantified with monoexponential, fractional-order, and biexponential fitting. We applied two methods for T2 * analysis: first, a standard approach by analyzing all voxels covering the proximal patellar tendon. Second, within subregions of the patellar tendon, by using thresholds on biexponential fitting parameter percentage short T2 * (0-30% for mostly long T2 *, 30-60% for mixed T2 *, and 60-100% for mostly short T2 *). STATISTICAL TESTS: Average test-retest reliability was assessed in three athletes using coefficients-of-variation (CV) and coefficients-of-repeatability (CR). RESULTS: With standard image analysis, we found a median [interquartile range, IQR] monoexponential T2 * of 6.43 msec [4.32-8.55] and fractional order T2 * 4.39 msec [3.06-5.78]. The percentage of short T2 * components was 52.9% [35.5-69.6]. Subregional monoexponential T2 * was 13.78 msec [12.11-16.46], 7.65 msec [6.49-8.61], and 3.05 msec [2.52-3.60] and fractional order T2 * 11.82 msec [10.09-14.44], 5.14 msec [4.25-5.96], and 2.19 msec [1.82-2.64] for 0-30%, 30-60%, and 60-100% short T2 *, respectively. Biexponential component short T2 * was 1.693 msec [1.417-2.003] for tissue with mostly short T2 * and long T2 * of 15.79 msec [13.47-18.61] for mostly long T2 *. The average CR (CV) was 2 msec (15%), 2 msec (19%) and 10% (22%) for monoexponential, fractional order and percentage short T2 *, respectively. DATA CONCLUSION: Patellar tendinopathy is characterized by regional variability in binding states of water. Quantitative multicompartment T2 * analysis in PT can be facilitated using a voxel selection method based on using biexponential fitting parameters. LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY STAGE: 1 J. Magn. Reson. Imaging 2020;52:420-430.

Quantitative DCE-MRI demonstrates increased blood perfusion in Hoffa's fat pad signal abnormalities in knee osteoarthritis, but not in patellofemoral pain.

OBJECTIVE: Infrapatellar fat pad (IPFP) fat-suppressed T2 (T2FS) hyperintense regions on MRI are an important imaging feature of knee osteoarthritis (OA) and are thought to represent inflammation. These regions are also common in non-OA subjects, and may not always be linked to inflammation. Our aim was to evaluate quantitative blood perfusion parameters, as surrogate measure of inflammation, within T2FS-hyperintense regions in patients with OA, with patellofemoral pain (PFP) (supposed OA precursor), and control subjects. METHODS: Twenty-two knee OA patients, 35 PFP patients and 43 healthy controls were included and underwent MRI, comprising T2 and DCE-MRI sequences. T2FS-hyperintense IPFP regions were delineated and a reference region was drawn in adjacent IPFP tissue with normal signal intensity. After fitting the extended Tofts pharmacokinetic model, quantitative DCE-MRI perfusion parameters were compared between the two regions within subjects in each subgroup, using a paired Wilcoxon signed-rank test. RESULTS: T2FS-hyperintense IPFP regions were present in 16 of 22 (73%) OA patients, 13 of 35 (37%) PFP patients, and 14 of 43 (33%) controls. DCE-MRI perfusion parameters were significantly different between regions with and without a T2FS-hyperintense signal in OA patients, demonstrating higher Ktrans compared to normal IFPF tissue (0.039 min-1 versus 0.025 min-1, p = 0.017) and higher Ve (0.157 versus 0.119, p = 0.010). For PFP patients and controls no significant differences were found. CONCLUSIONS: IPFP T2FS-hyperintense regions are associated with higher perfusion in knee OA patients in contrast to identically appearing regions in PFP patients and controls, pointing towards an inflammatory pathogenesis in OA only. KEY POINTS: • Morphologically identical appearing T2FS-hyperintense infrapatellar fat pad regions show different perfusion in healthy subjects, subjects with patellofemoral pain, and subjects with knee osteoarthritis. • Elevated DCE-MRI perfusion parameters within T2FS-hyperintense infrapatellar fat pad regions in patients with osteoarthritis suggest an inflammatory pathogenesis in osteoarthritis, but not in patellofemoral pain and healthy subjects.

Quantitative subchondral bone perfusion imaging in knee osteoarthritis using dynamic contrast enhanced MRI.

OBJECTIVE: Subchondral bone changes, characterized by increased bone turnover and vascularity, are believed to stimulate progression and pain in knee osteoarthritis (OA). The objective of this study was to evaluate the bone perfusion in knee OA using quantitative dynamic contrast enhanced MRI (DCE-MRI). DESIGN: Unicompartmental knee OA patients were included and underwent 3 Tesla DCE-MRI and T2-weighted MRI. Quantitative DCE-MRI analysis of Ktrans and Kep, representing perfusion parameters, was performed to evaluate differences between the most and least affected knee compartment. First, DCE-MRI parameter differences between epimetaphyseal and subchondral bone in both femur and tibia were assessed. Second, DCE-MRI parameters in subchondral bone marrow lesions (BMLs) were compared to surrounding subchondral bone without BMLs. RESULTS: Twenty-three patients were analyzed. Median Ktrans and Kep in epimetaphyseal bone were significantly higher (p < 0.05) in the most affected (Ktrans: 0.014; Kep: 0.054 min-1) compared to least affected (Ktrans: 0.010; Kep: 0.016 min-1) compartment. For subchondral bone, DCE-MRI parameters were significantly higher (p < 0.05) in the most affected (Ktrans: 0.019; Kep: 0.091 min-1) compared to least affected (Ktrans: 0.014; Kep: 0.058 min-1) compartment as well. Subchondral BMLs detected on fat-saturated T2-weighted images were present in all patients. Median Ktrans (0.091 vs 0.000 min-1) and Kep (0.258 vs 0.000 min-1) were significantly higher within subchondral BMLs compared to surrounding subchondral bone without BMLs (p < 0.001). CONCLUSIONS: Increased perfusion parameters in epimetaphyseal bone, subchondral bone and BMLs are observed in unicompartmental knee OA. BMLs likely account for most of the effect of the higher bone perfusion in knee OA.