[Application of ultra-short echo time-T* component analysis technology in monitoring morphological and biochemical changes of achilles tendon in amateur marathon athletes].

To explore the value of ultra-short echo time (UTE)-T* component analysis techniques in dynamic monitoring the morphological and biochemical changes in amateur marathon athletes' achilles tendon before and after the marathon. Twenty-nine amateur marathon runners were recruited between October 2020 and March 2021 in Zhuhai City, Guangdong Province, including 25 males and 4 females, aged from 24 to 50 (40±6) years old. All volunteers underwent bilateral achilles tendon MRI examination 1 week before the marathon, 48 hours after the race, and 1 month after the race. The shape and signal of the achilles tendon were evaluated by routine T1-weighted, proton density weighted with fat saturation sequence and different echo time (TE) UTE sequence, and the changes of achilles tendon after running was quantitatively analyzed by UTE-T2* sequence. The values of single-component analysis (T*), short T* components (T*), and long T* components (T*) and Fraction values were obtained using UTE-T* sequence. The value of the whole achilles tendon was measured on the sagittal images of achilles tendon, and the Achilles tendon was equally divided into three subregions [muscle-tendon junction (MTJ), middle (MID), and insertion (INS)]. The region of interest was delineated by two radiologists independently. The intra-group correlation coefficient (ICC) was used to evaluate the consistency of the data measured by two radiologists. Nonparametric Friedman test was used to compare the differences of T*, T*, T* and Fraction values in different time points and different subregions. Wilcoxon rank-sum test was used to compare the difference between 48 h post-race and pre-race T* values (ΔT*) of different distance, different running posture, different pace and different amount of training, in which ΔT* equals the T* value of 48 h post-race minus the T* value of pre-race. On the sequence of short TE (TE≤0.6 ms), achilles tendinopathy can manifest as scattered punctate hypointensity in areas of high signal intensity. The two radiologists showed a good consistency in measuring the T*, T*, T* and Fraction values of the achilles tendon, and the ICC values ​​were 0.96, 0.94, 0.83 and 0.94, respectively. The Ts values was significantly higher in the whole Achilles tendon, MTJ and MID segment at 48 h post-exercise compared to pre-exercise, and decreased after 1 month of exercise, [0.49 (0.45, 0.59) vs 0.54 (0.49, 0.59) vs 0.53 (0.49, 0.57), 0.48 (0.44, 0.54) vs 0.53 (0.47, 0.58) vs 0.50 (0.46, 0.57), 0.48 (0.43, 0.58) vs 0.54 (0.47, 0.59) vs 0.52 (0.46, 0.57); respectively, all <0.05]. The changes in T*, T* and Fraction values are not statistically significant (all >0.05). In different running gestures, the ΔT of achilles tendon who using the postures of front-middle feet is higher than that using the postures of back feet (0.03(-0.05, 0.07) vs -0.03(-0.17, 0.11), =0.001). The Bi-component analysis of UTE-T* technology is superior to single component analysis in monitoring the dynamic changes of achilles tendon before and after exercise, and T* is a more sensitive sequence to evaluate the subtle changes in the chemical composition of achilles tendon.