Study And Application Of MR Relaxation Time Mapping In Articular Cartilage

Articular cartilage is a connective tissue that covers the osseous surfaces of joint, with the ability to absorb mechanical stress and reduce friction for preserving joint integrity. Bing an avascular, alymphatic, and aneural tissue, it has an extremely poor regenerative capacity, and subsequent degeneration of injured cartilage and other articular tissues often lead to osteoarthritis and a diminished quality of life. With advantages of excellent soft-tissue contrast, multi-plane and invasive technique, magnetic resonance imaging(MRI) has become the most important modality for morphologic assessment of articular cartilage. Over recent years, developments of various physiological MRI techniques allow evaluation of biochemical composition and ultrastructure in cartilage, such as relaxation time mapping and so on. Several methods have been applied to quantify cartilage defects using T2mapping, T1mapping and T2star(T2*) mapping techniques. The purpose of this feasibility study was to obtain additional information for cartilage evaluation by using T2and T2*mapping, and to compare and correlate both methodologies. Firstly, we performed statistical analysis of T2and T2*variance in matched knee regions before and after exercise, to explore the feasibility and value of MR T2and T2*mapping in evaluating cartilage matrix changes of the knee joint. Secondly, we compared T2and T2*values of cartilage in knee injury with those of control cartilage, to assess the diagnostic value of MR T2and T2*mapping in detection of early articular cartilage injury of knee.Part I A preliminary research of T2and T2star relaxation times mapping for assessment of articular cartilage in the kneeObjective:To explore the feasibility and value of magnetic resonance(MR) T2and T2star(T2*) mapping in evaluating cartilage matrix changes of the knee joint after exercise.Methods:MR T2and T2*maps of articular cartilage were obtained in twenty young healthy volunteers before and immediately after exercise by using a3.0-T MR scaner. Lateral femoral condyle and medial femoral condyle compartments were partitioned into anterior and posterior nonweight-bearing (ant-nwb and post-nwb) zones and weight-bearing (wb) zones in all subjects. Cartilage T2and T2*values of femoral condyle and tibia were quantified in full-thickness, superficial and deep layers of seven defined subcompartments. Statistical analysis of T2and T2*variance and correlation in matched regions was performed.Results:There was a statistically significant decrease of T2values in the full-thickness cartilage of lateral femoral condyle(wb) and medial femoral condyle(post-nwb), as well as in the superficial layers of lateral femoral condyle(wb and post-nwb) and medial femoral condyle(wb and post-nwb), and in the deep layers of medial femoral condyle(post-nwb) afer exercise. Significant decrease of T2*values were also be shown in the full-thickness cartilage of lateral femoral condyle(wb and ant-nwb), medial femoral condyle(post-nwb) and medial tibia, as well as in the superficial layers of lateral femoral condyle(wb and ant-nwb), medial femoral condyle(wb and post-nwb), lateral tibia and medial tibia, and in the deep layers of medial tibia. T2and T2*values of superficial layers in seven defined subcompartments were significantly elevated compared with those of deep layers. The correlation between T2and T2*was significant, particularly in the superficial layers.Conclusion:T2and T2*mapping can help assess the microstructural composition of articular cartilage, and show great promise in clinical application. Part II A study of T2and T2star relaxation times mapping in early articular cartilage injury of kneeObjective:To assess the diagnostic value of magnetic resonance(MR) T2and T2star(T2*) mapping in quantitative analysis of early articular cartilage injury of knee.Methods:MR T2and T2*maps of articular cartilage were obtained in nineteen patients with knee injury by using a3.0-T MR scaner. Twenty age-matched healthy subjects were studied as controls. Lateral femoral condyle and medial femoral condyle compartments were partitioned into anterior and posterior nonweight-bearing (ant-nwb and post-nwb) zones and weight-bearing (wb) zones in all subjects. Cartilage T2and T2*values of femoral condyle and tibia were quantified in full-thickness, superficial and deep layers of seven defined subcompartments. Statistical analysis of T2and T2*variance and correlation in matched regions was performed.Results:There was a statistically significant increase of T2and T2*values in most regions of interest(ROI) for patients compared with those for controls, particularly in the superficial layers. No difference was found in the deep layers between two groups. T2and T2*values of superficial layers in seven defined subcompartments demonstrated significant difference within patient group. A statistically significant correlation of T2and T2*values was apparent in twelve ROIs.Conclusion:T2and T2*mapping can evaluate biochemical compositions in early articular cartilage injury of knee, and may offer important information for early diagnosis and treatment.