| Objective:To evaluate the application value of ultrasound gel pad in shear wave elastography(SWE)of testes by comparing the measurement of shear wave velocity(SWV)of normal rabbit testes using ultrasound gel pad or thick ultrasound transmission gel.To investigate the changes of testicular hardness in different courses after testicular torsion by continuous follow-up observation of twisted testes combined with histopathological results after establishing the acute testicular torsion model.Methods and results:Part Ⅰ To evaluate the application value of ultrasound gel pad in testes by shear wave elastographyMethods: Thirty healthy,adult male New Zealand white rabbits were studied,and the bilateral testes were observed by conventional ultrasound(including gray-scale ultrasonography and color Doppler flow imaging)and SWE using ultrasound gel pad and thick ultrasound transmission gel respectively.Ten successive SWV measurements were obtained in the central zone of the largest standard transverse axis view of testicular parenchyma,and the mean,standard deviation and interquartile range/median were calculated and recorded.Results: Ten successive SWV measurements in the central zone of the largest standard transverse axis view of normal testicular parenchyma were obtained by using ultrasound gel pad,and the mean and standard deviation were significantly smaller than those in the thick ultrasound transmission gel(1.67±0.16 versus 2.46±0.20m/s,0.09±0.03 versus 0.22±0.08m/s;P<0.001,P<0.001,respectively).Whether using ultrasound gel pad or thick ultrasound transmission gel,ten successive SWV measurements in the central zone of the largest standard transverse axis view of normal testicular parenchyma were obtained,and all the measured values were consistent with the interquartile range/median ≤30%(all 60/60,100%).With the interquartile range/median as the standard,the number of cases being in conformity the standard in the ultrasound gel pad was significantly larger than that in the thick ultrasound transmission gel(48/60,80.0% versus 14/60,23.3%;P < 0.001).Repeatedly successive SWV measurements in the central zone of the largest standard transverse axis view of normal testicular parenchyma were obtained by using ultrasound gel pad,and no significant difference was reported in the mean of 1,3,5 and 10 SWV value(1.71±0.20 versus 1.69±0.19 versus 1.68±0.17 versus 1.67±0.16m/s;P=0.598).Three successive SWV measurements in the central zone of the largest standard transverse axis view of normal testicular parenchyma were obtained by using ultrasound gel pad,and the mean value of left testes was comparable with that of right testes(1.66±0.21 versus 1.72±0.16m/s;P=0.108).Three successive SWV measurements in the central zone of the largest standard transverse axis view of normal testicular parenchyma were obtained by two ultrasound physician using ultrasound gel pad,and it demonstrated good consistency [ICC=0.823;95% confidence interval:(0.712,0.892);P<0.001].Part Ⅱ Experimental study on evaluation of testicular torsion by shear wave elastographyMethods: Sixty-one healthy,adult male New Zealand white rabbits were studied.Sixty healthy,adult male New Zealand white rabbits meeting the inclusion criteria were randomly divided into three groups including complete torsion group(n=20),incomplete torsion group(n=20)and sham group(n=20).After establishing the rabbit model of complete or incomplete acute testicular torsion,the bilateral testes were observed by conventional ultrasound(including gray-scale ultrasonography and color Doppler flow imaging)and SWE before and immediately after torsion,1h,2h,3h,6h,8h,12 h,1d,2d,3d,4d,5d,6d and 7d.Results: In the complete torsion group,the echo of torsion testes of the rabbits was decreased and uneven started from 1 day after torsion.There were some small tubular structures in the testicular parenchyma,and the surrounding tissues were swollen and thickened.With the increase of torsion time,SWE showed that the blue area in the central zone of the largest standard transverse axis view of testicular parenchyma gradually decreased and the hardness gradually increased,and the SWV value began to increase significantly 1 day after torsion.From 1 day after torsion,the peripheral zone of torsion testes showed a red ring,which was a “stiff ring sign”.In the incomplete torsion group,some experimental rabbits(66.7%)did not progress to complete torsion within 7 days after torsion.SWE showed that the central zone of testes was always blue(soft),and its SWV value had no change,showing a steady trend.And its peripheral zone began to harden 1 day after torsion,and its SWV value increased slightly.In addition,some experimental rabbits(33.3%)progressed to complete torsion at different time points within 1 day after torsion.With the increase of torsion time,the testicular parenchyma gradually became harder,and the SWV value in the central zone increased significantly after 1 day postoperative,and the peripheral zone formed a "stiff ring sign".In the sham group,SWE showed that the central zone of testes was always stable and uniform blue(soft),while the peripheral zone was annular and uniform green(harder),and the SWV values of central zone and peripheral zone had no change.Conclusion:1.The SWE imaging of normal testes with ultrasound gel pad can obviously improve the image quality,and the measured value is more stable and reproducible.During the follow-up in the same study,the same ultrasound gel pad in common should be always used to make the measured values comparable.2.Different degrees of torsion have different hardness changes in the central and peripheral zones of testes.The hardness of torsional testes is not synchronized with the course of disease.3.“Stiff ring sign” is an ultrasonic elastography sign of testicular torsion,which has important clinical value in differential diagnosis of testicular torsion.4.The change of testicular hardness after torsion could reflect the degree of testicular congestion,ischemic,necrosis and spermatogenic function damage after torsion,which is helpful to the choice of clinical diagnosis and treatment. |
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