The Diagnostic Value Of MR T2-mapping In Early Articular Cartilage Injury Of Knee

ObjectiveTo measure T2 relaxation time of knee articular cartilage in patients with varying degrees of knee osteoarthritis (OA) compared with healthy subjects of the same age group, and to evaluate the diagnostic value of the T2-mapping imaging in early knee articular cartilage injury.Materials and MethodsTo collect the patients of knee osteoarthritis(OA) diagnosed by the clinician of Shandong Provincial Hospital in the period of October,2008 to February,2010. According to the evaluation standard of Kellgren-Lawrence, two radiological experts graded to X-ray of the knee joints of patients:grade 1: suspicious or mild hyperosteogeny; grade 2:assured hyperosteogeny,but not obvious narrower joint space; grade 3:moderate hyperosteogeny and(or) obvious narrower joint space; grade 4:severe hyperosteogeny,and obvious narrower joint space and(or) subchondral osteosclerosis.All the patients were grouped according to the grade standard, grade 1～2 for mild OA group and grade 3-4 for severe OA group. To choose 32 cases of mild OA patients (19 men and 13 women, the age ranged from 35 to 46 years,average 42.3 years); 15 cases of severe OA patients (8 men and 7 women, the age ranged from 36 to 47 years,average 43.2 years).20 cases for normal group (11 men and 9 women, the age ranged from 35 to 47 years, average 40.8 years). The normal volunteers did not have past medical history of bothered knee joint,trauma,infection,surgery or chronic disease with long -term drug treatment.All the subjects including the normal groud and case group of varying degrees of OA, were grouped into 3 groups according to the body mass index (BMI):normal group,overweight group and fat group(35 cases of normal group,18 cases of overweight group and 14 cases of fat group). All of the subjects were not sport athletes or manual workers, and didn't have heavy exercise for three hours before MRI scanning.The patients of OA and 20 healthy volunteers were firstly carried on scanning of routine sagittal T2WI/PDWI,coronal T1WI and FS-T2WI with a 3.0T MR imaging spectrometer with the coil of knee joint, then T2-mapping imaging was carried on sagittal scaning with 8-echo fast spin echo(FSE), Quantitative T2-mapping of knee articular cartilage was evaluated with the 3.0T MR imaging spectrometer in 20 healthy subjects,32 patients of mild OA and 15 patients of severe OA,T2 value in four compartments of knee cartilage (condylus medialis and condylus lateralis femoris,condylus medialis and condylus lateralis tibiae) were measured respectively in T2-mapping imaging. All the dates of T2-mapping imaging were processed by GE ADW 4.3 workstation,and statistical differences were analyzed with SPSS 15.0 statistics software.Results1,The routine MRI images and T2-mapping images of 20 cases of normal volunteers and 47 cases of OA patients were acquisited successfully, and all the images met the diagnosis and data analysis;2,T2-mapping imaging of normal knee articular cartilage displayed integrated and successive cartilage,the color gradation showed orange red, and the signal was uniform, the range of T2 value of cartilage was between 34.2～41.8ms,and the average T2 value was (37.85±3.28)ms; T2-mapping imaging of mild OA group showed that continuity of cartilage was tolerable, but parts of the cartilage were seen mixed heterogeneous signal of speckle or irregular green color gradation,the range of T2 value of cartilage was between 40.5～54.8ms, and the average T2 value was (48.16±5.12) ms;T2-mapping imaging of severe OA group showed the joint space became narrow, the cartilage became thin and discontinuous obviously,and the color gradation showed heterogeneous mixed signal,the range of T2 value of cartilage was between 45.6～58.2ms, and the average T2 value was (51.62±5.44) ms;3,The mild OA group and severe OA group showed obvious increases in T2 value compared to the control group, and there was a significant difference in T2 value between case group and control group (P<0.05); 4,There was no obvious significant difference between the mild OA group and severe OA group (P>0.05);5,According to the BMI standard,the average T2 relaxation of normal group, overweight group and fat group were (39.34±5.21) ms,(44.41±4.52) ms and (48.81±6.55) ms. The significant differences were found between normal group and overweight group or fat group (P< 0.05 among the three groups).Conclusions1,The average T2 relaxation of normal group, mild OA group and severe OA group were (37.85±3.28) ms, (48.16±5.12) ms and (51.62±5.44) ms;2,The significant difference was found between the normal group and mild OA group or the severe OA group, no significant difference was found between mild OA group and severe OA group. The changes of T2 value provided an important means for the diagnosis of OA. T2-mapping imaging was one of the physiological imaging technique of MRI in articular cartilage, and it could indicate component abnormality by quantificationally analyzing ingredient changes of microstructure in early cartilage injury without morphological change, so T2-mapping imaging has a high clinical value in early diagnosis and tracking of early articular cartilage injury;3,There were significant differences of T2 value of different BMI, and that high BMI(overweight,fat) may be considered a potential factor of OA,so we may delay the patients' condition of OA through controlling the body's weight.