| With the improvement of living standards and health concepts,long-distance running has become a popular entertainment activity,and the holding of marathon events in China has increased year by year.According to statistics,1100 marathons and related sports events were held all over the country in 2017,and the number of events increased 50 times between 2011 and 2017.Because of the lack of professional running knowledge and systematic guidance,runners are prone to injury during running,among which the probability of injury of knee joint is the highest.The number of medical imaging of marathons in foreign countries is not many,which was almost blank in China.This study aimed to observe the change of knee cartilage T2 value before and after marathon,and evaluated whether the runner would have knee cartilage injury after marathon.We can only obtain some two-dimensional information in conventional MR imaging,and quantitative values such as T2 and T2* values from manually sketched,while 3D reconstructed images overcome the shortcomings of conventional 2D images.In this study,we used knee cartilage automatic segmentation software to obtain cartilage quantitative values and cartilage volume values.After manual modification,we verified the clinical application value of this software.Part 1 Evaluation of short-term and mid-term cartilage changes in kneejoint before and after marathon using T2 mapping imagingObjective: To assess the short?term and mid?term changes of knee cartilage in non?professional long?distance runners before and after marathon using T2 mapping imaging.Methods: Twenty?four knee joints of 12 healthy volunteers(5 males and 7 females)who participated in the marathon were examined by 3.0T MRI one week before the race,within 12 hours after the race and two months after the race,respectively.The age ranged from 21.0 to 37.0 years.Athletes run more than three times a week,and each time was about 30 minutes.The volunteers received three times MR scanning.The MRI normal scan sequence sagittal FS-PDWI sequence and sagittal T2 mapping sequence are included.Conventional images were used to evaluate the basic conditions of ligaments,cartilage,bone articular surface and soft tissue of knee joint.From T2 mapping we can obtain T2 value of 6 cartilage subregions of knee joint.The articular cartilage was divided into six subregions: medial femoral condyle(MFC),lateral femoral condyle(LFC),medial tibial plateau(MTP),lateral tibial plateau(LTP),Patella and Trochlea.The cartilage is divided into superficial zone(SZ)and deep zone(DZ)according to 1/2 of thickness.Sketch the ROI on the T2 mapping sequence.Paired t?test was used to compare the T2 values of cartilage before and after the marathon.The comparison between the superficial and deep T2 values of cartilage was performed by independent sample t test.Result: Twenty-four knee joints were included in 12 h before and after the race,and twenty knee joints were followed up 2 months after the race.1.Routine MRI examination of knee jointBefore and after the race,there was no obvious abnormality in the morphology and signal of knee cartilage.One of the athletes had bone marrow edema in the distal femur and proximal tibia of both sides before the race.Within 12 h after the race the range of bone marrow edema was reduced and the signal decreased.Bone marrow edema almost disappeared at 2 months follow-up.2.Change of T2 value of articular cartilageT2 mapping imaging showed that the T2 value of the superficial articular cartilage was higher than that of deep articular cartilage in pre?competition,within 12 hours after competition and 2 months follow?up,respectively(t=11.095,10.385 and 10.102,P<0.01).The T2 value of superficial articular cartilage decreased after the competition compared with that of pre ?competition(t=2.18,P<0.05),while the T2 value of deep articular cartilage showed no significant difference compared with that of pre?competition(t=1.832,P>0.05).Except for the MTP?DZ,the T2 value of the remaining cartilage subregions showed a trend of decrease within 12 hours after the competition.There were significant differences in the subregion of MFC?DZ(t=2.110,P<0.05).At the follow?up of 2 months,cartilage T2 values of the MTP?SZ,LTP?SZ,LTP?DZ,MFC?DZ,Patella?SZ,Patella?DZ,Trochlea?SZ,Trochlea?DZ subregions showed a trend of recovery,and there was no significant difference compared with pre?competition(P>0.05).The T2 values of the LFC?SZ and LFC?DZ were lower than those before the race,with statistical significance(t=2.378,3.147,P<0.05).Conclusion:1.Marathon may not cause significant changes in knee cartilage morphology in non-professional athletes.2.The occurrence of bone marrow edema in non-professional marathon athletes may be related to individual physique and exercise intensity.It may be reversible lesions.3.A decrease in the T2 value of knee cartilage after marathon is due to the change in the direction of collagen fibers and water content in the cartilage under pressure.From current trends,most cartilage T2 value presents a reversible change.4.The biochemical components of cartilage can be quantitatively analyzed by measuring the T2 value of cartilage,which can provide imaging basis for early diagnosis of cartilage injury from the molecular level and provide assistance for clinical decision.Part 2 Validation of clinical efficacy of auto-segmentation software forquantification of knee cartilageObjective: From the auto-segmentation software(Siemens Chondral Health,Version 2.1,Siemens Healthcare,Erlangen,Germany),we can obtain the volume and T2* value of knee cartilage,compared with the result of manual segmentation,to verify the accuracy and clinical value of software results.Methods: A total of 32 images were recruited in this study.All the volunteers underwent right knee MRI examinations.Conventional MRI images are used to observe the basic condition of the knee joint.The morphological image was obtained using a 3D high-resolution Double-Echo in Steady-State(DESS)sequence with selective water excitation,and the biochemical image was obtained using a 2D T2 star mapping sequence.A senior-level radiologist evaluated the extent of cartilage degeneration and hydrarthrosis,blinded with the clinical information of volunteers.Cartilage score criteria were obtained using the Whole-Organ Magnetic Resonance Imaging Score(WORMS).The error rate of cartilage volume and T2 star value derived from automatic and manual cartilage segmentation were compared.Result: A total of 32 images were included.the control group(n=14)and the effusion group(n=18)were divided into worms0 groups(n=21)and worms1-2groups(n=11)according to the morphology and signal of cartilage.Between different scoring groups of articular cartilage and joint effusion,the change rate of cartilage volume and T2* value in different cartilage subregions was compared.We used nonparametric rank sum test because of the small sample size,P<0.05 representative differences were statistically significant.1.The time required to complete data processingThe average time for automatic segmentation software to complete a case of cartilage segmentation was 6 minutes 14 seconds,and the average time for manual modification was 27 minutes 23 seconds.2.The volume of cartilageThe cartilage volume in manual cartilage segmentation group is less than automatic cartilage segmentation group(P<0.05).The change rate of cartilage volume in each subregion is less than 6.45%.With regard to the overall cartilage of the knee joint,the result of automatic segmentation was 17.03 ml,the modified total volume of cartilage was 16.87 ml,and the difference was statistically significant(P<0.05).3.The T2* value of cartilageIn all the manual cartilage segmentation subregions,the T2 star value is lower than automatic cartilage segmentation group(P<0.05).With respect to the overall cartilage of the knee joint,the T2* result of automatic segmentation was 21.81 ms,the modified result was 21.25 ms,the difference was statistically significant(P<0.05).4.Number of layers modifiedThe average number of modified layers in 21 cartilage subregions were calculated.The average number of modified layers is 0,2.9,6.8,0.3,7.9,9.2,0,0.3,0.7,2.6,5.3,0.1,8.7,10.3,3.8,0,0.6,0.3,1.2,4.9,6.2 in FMP,FMC,FMA,FTM,FTC,FTL,FLP,FLC,FLA,PLI,PLC,PLS,PMI,PMC,PMS,TLP,TLC,TLA,TMP,TMC,TMA,respectively.The more error-prone subregions of the distal femoral cartilage are TC and TL.The more error-prone subregions of patellar cartilage are MI and MC.The more error-prone subregion of the cartilage in the proximal tibia is MC and MS.The femoral condyle and patella had the highest error rates(3.4% and 4.6%)when the cartilage score was 0 in the control group.The femoral condyle and patella had the highest error rates(4.0% and 6.8%,respectively)when the cartilage score was 2 in the hydrarthrosis group.Conclusion:1.The time of software automatic segmentation is greatly reduced compared with manual segmentation time.2.Automatic cartilage segmentation software has a low error rate,less than 7%.We can modify it at a specific location,it can more accurately evaluate the cartilage thickness,volume and biochemical composition parameters.3.The software can provide more quantitative information of cartilage morphology and biochemical indexes in a relatively small time range,which greatly reduces the workload of labor. |
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