| Part 1:Reproducibility and Accuracy of Quantitative Knee Cartilage Volume measurements using semi-automated software by MRI at 3.0TObjective:To evaluate the reproducibility and accuracy of semi-automated software OsiriX in the assessment of knee cartilage volume at 3.0T MR.Methods:The right knees of thirty healthy subjects and thirty patients with osteoarthritis were scanned twice with 3.0T MR using 3D-FLASH sequence with selective water excitation. Cartilage volume of the patellar compartment was determined with a validated open-source software OsiriX and manual segmentation separately by 3 observers using the MRI data sets. After calculating the cartilage volumes, the segmentation processing times, the reproducibility and volume results were compared between two segmentations.Results:①Compared with the manual segmentation, a time saving of at least 50% for cartilage volume measurement was achieved with OsiriX software segmentation.②In the normal group,the interobserver reproducibility error was 4.9% and 9.8% with OsiriX software segmentation and manual segmentation, respectively; the intraobserver reproducibility error of high experienced observer were 0.8% and 1.3%, the interindividual reproducibility error range were 0.1%～1.1% and 0.5%～1.6%. The reproducibility error of OsiriX software segmentaion proved to be significantly smaller than manual segmentation (P<0.05).③In the OA group,the interobserver reproducibility error was 6.2% and 11.3% with OsiriX software segmentation and manual segmentation, respectively; the intraobserver reproducibility error of high experienced observer were 1.5% and 2.7%, the interindividual reproducibility error range were 0.7%～2.0% and 1.2%～3.7%. The reproducibility error of OsiriX software segmentaion proved to be significantly smaller than manual segmentation (P< 0.05).④In the normal group,systematic pairwise difference between results obtained with OsiriX software measurement and manual measurement was-3.8% and absolute pairwise difference was (4.7±2.7)%. There was no statistical difference between the volume results measured by two techniques (t=0.92, P=0.36).⑤In the OA group, systematic pairwise difference between results obtained with OsiriX software measurement and manual measurement was-5.4% and absolute pairwise difference was(6.3±4.0)%. There was no statistical difference between the volume results measured by two techniques (t=0.74, P=0.47).Conclusion:Compared to manual segmentation, cartilage volume measurement with OsiriX semi-automated segmentation is faster and has higher inter- and intraobserver reproducibility with relatively fixed standard. This technique may therefore be used for clinical and multi-center trials of large sample.Part 2:Quantitative Measurement of the Knee joint Cartilage Volume in normal adult at 3.0T MRIObjective:To provide the normal reference value of cartilage volumes in the knee joints of healthy adults,study the percentage of the patellar, femoral, and tibial cartilages and analyze the correlation of the volumes with age,sex,body height and weight.Methods:We examed the knee joints of 140 healthy volunteers who had no past history of joint disease or trauma or operation.The studied population was divided by age into 7 groups. Each knee was examed twice using a sagittal 3D-MEDIC sequence with water excitation. The cartilage volumes and the three-dimensional reconstruction was determined by a semiautomatic software OsiriX.Results:The mean total volume of the knee joint cartilage was (18.16±4.36)cm3, the femoral cartilage volume occupied the highest percentage of the total knee joint volume, then the patellar and lateral tibial cartilage, the lowest one was the medial tibial cartilage. The mean percentage of each compartments was (58.1±3.3)%, (18.7±2.0)%, (13.3±1.8)% and (10.0±1.9)%,respectively. The medial tibial cartilage volume showed the highest Coefficient Variations(CV%) of the percentage(CV%=19%). Males displayed higher cartilage volumes than females.The mean total volume of cartilage in males was (21.62±3.63)cm3, in female was(14.70±2.83) cm3. There was no significant correlation of the total cartilage volume with age(r=-0.19), the same to each compartment of the joint cartilage. The total cartilage volume was positively correlated with body height (r=0.48,P<0.001) and weight(r=0.30,P<0.001).Conclusion:The mean total volume of the knee joint cartilage in normal adult is (18.16±4.36)cm3, each compartment occupies a relatively variable percentage of the total knee joint volume. The cartilage volume in males is higher than in females. There is no significant correlation of the knee joint cartilage volume with age. The cartilage volume is positively correlated with body height and weight.Therefore,the estimation of cartilage volume changes with cartilage lesion should consider the factors of sex, body height and weight.Part 3:Quantitative Measurement of Knee Cartilage volume in Osteoarthritis at 3.0 T MRIObjective:The knee cartilage volumes of various degrees of OA patients was determined by using a sagittal 3D-MEDIC sequence with water excitation at 3.0T MRI, and the clinical value of knee cartilage volume measurement at 3.0 MRI in OA are also evaluated after being compared with those in the normal group. Methods:58 male subjects having the symptoms of knee pain and function impairment in their knees were included, and all the cases had no history of trauma and operation.According to the OA index made by WOMAC and K-L radiological diagnosis standard, the cases with OA in the knee could be further classified into gentle, medium and serious groups.20 normal male subjects were selected for contrast. All of the knees were scanned by a sagittal 3D-MEDIC sequence with water excitation. The knee cartilage volumes was determined by a semiautomatic software OsiriX and the measurements were adjusted for height and weight.The volume measurements of OA groups were compared with normal group.Results:Comparing articular cartilage volume between in the OA cases of various degrees and in the healthy volunteers, in the gentle OA group, there was no statistical difference of knee cartilage volume with that in the normal volunteers, while that in medium and serious OA groups was significant different from that in the normal group.Conclusion:By comparing of articular cartilage volume between in the OA cases and in the healthy volunteers, we observed that the articular cartilage volume of each compartment of the knee joint attenuated gradually, following with the aggregated OA disease, especially in the serious group. The cartilage volume measurement at 3.0T MRI could offer quantitative evidence for OA cartilage defects.
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