| Osteoarthritis(OA) is a progressive chronic degenerative disease. A valid diagnosis and monitoring tool for knee OA in early prediction, early diagnosis, accurate assessment and evaluation is required. Early investigators tended to regard OA as an isolated disease of articular cartilage. But more recent studies have shown that entire synovial joint organ is affected by OA. OA can be viewed as the clinical and pathologic outcome of a range of disorders that results in structural and functional failure of the synovial joint organ with loss and erosion of articular cartilage; subchondral bone alteration; meniscal degeneration; a synovial inflammatory response; and osteophytes. The onset and progression of knee OA is associated with articular cartilage degeneration. All three components in extracellular matrix act together to provide the mechanical support necessary for smooth functioning of articular cartilage. An imbalance in these molecular compositions results in cartilage abnormalities that lead to its molecular compositional degeneration and followed by biomechanical changes of cartilage, cartilage erosion, rupture, ulcers, while resulting in subchondral bone sclerosis, cyst, osteophytes and synovitis eventually. MRI is a noninvasive modality with high resolution, multi-parameter, multi-planar characteristics. It has become a key imaging tool for early diagnosis and accurate assessment of OA research thanks to semi-quantitative, morphological and physiological quantitative imaging. MR whole-organ semi-quantitative scoring is a valuable method for performing multifeature assessment of the knee, with high sensitivity, specificity, and reliability. Quantitative compositional MRI allows visualization of the biochemical properties of aritcular cartilage. It is sensitive to early, pre-morphologic changes that cannot be visualized on conventional MRI. Although MR whole-organ semi-quantitative scoring has been used often in the west countries, but still rare in China. T2 mapping and T1ρ imaging are two quantitative compositional MRI techniques which need no special equipment, no introduction of contrast agents, and with short time V consuming but high resolution images. The aim of this stuy is to evaluate the application of MRI whole-organ semi-quantitative assessment and T2 mapping, T1ρ quantitative imaging of articular cartilage in the knee OA. There are two sections:Section I: Conventional MR images were independently analyzed using a whole-organ MRI scoring method(WORMS) that incorporated 14 features: articular cartilage integrity, subarticular bone marrow abnormality, subarticular cysts, subarticular bone attrition, marginal osteophytes, medial and lateral meniscal integrity, anterior and posterior cruciate ligament integrity, medial and lateral collateral ligament integrity, synovitis/effusion, intraarticular loose bodies, and periarticular cysts/bursitis in the different compartments and subregions of the knee joints. All patients showed the presence of articular cartilage lesions and osteophytes and 81% of patients with subarticular bone marrow abnormality, 77% with subarticular cysts, 63% with subarticular bone attrition, 12% with ligament tear, 54% with meniscus injury, 92% with synovitis/ effusion, 19% with articular loose bodies, 40% with periarticular cysts/bursitis. There is a good positive correlation between Kellgren-Lawrence grade and WORMS score, score of articular cartilage(P<0.05). There is a positive correlation between articular cartilage lesions with subarticular bone marrow abnormality, subarticular cysts, subarticular bone attrition, marginal osteophytes, meniscal integrity, ligaments injury, intraarticular loose bodies, and periarticular cysts/bursitis(P<0.05).Section II: In this study, we investigated the changes in T2 and T1ρ relaxation times in normal, OA patients and early degenerative cartilage. There were three groups in our study: the normal control group, OA group, overweight/obese group. The average T2 and T1ρ values were measured in central(c) and posterior(p) region of medial(MF) and lateral(LF) condyles in each group, respectively. The results showed the signal of cartilage on T2 mapping and T1ρ imaging became inhomogeneous in OA patients and overweight/obese group. There was an increase in both T2 and T1ρ values in cartilage in OA patients and overweight/obese group compared to normal controls. T2 and T1ρ values in OA group were higher than the overweight and obesity group, while there was statistically significant of T2 value changes in MFc, MFp and T1ρ value changes in LFc, LFp, MFc(P <0.05). There was moderate positive correlation between T2 and T1ρ value(r=0.691, P<0.05). There was a weakly positive correlation between BMI and T2, T1ρ value(r=0.313 and 0.465, respectively), while a statistically significant betweent BMI and T1ρ value(P<0.05).The results of this study showed MRI whole-organ semi-quantitative assessment offers an opportunity to evaluate all components of a joint simultaneously and therefore to provide a whole organ assessment of the status of every structural damage in patients with OA. In vivo T2 mapping and T1ρ techniques have demonstrated feasibility in detecting early cartilage degeneration. Quantitative cartilage imaging may enhance our ability to detect early matrix changes associated with cartilage injuries. These two MR assessment methods could help detect early stages of OA, decide early intervention targets and treatment, increase the sensitivity for monitoring disease progression and treatment response. |
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