STRAIN ELASTOGRAPHY IN DOGS: APPROACH TO SOME CLINICAL APPLICATIONS

Strain elastography is useful in differentiating benign from malignant lesions in human medicine. The aim of this study was to assess the repeatability and reproducibility of elastography in the evaluation of canine splenic lesions, mammary lesions and superficial nodules and to verify if they can be differentiated in benign or malignant. Twenty-four dogs presenting a single splenic hypoechoic lesion, underwent B-mode ultrasonographic and elastographic evaluation. The Strain Ratio (SR) and Hardness Value (HV) were calculated for all the lesions. The SR and HV of benign lesions were statistically different from those of malignant lesions (p<0,05). Malignant lesions tended to have a SR >1,5 (p=0,0003; Se 75%, Sp 100%, PLR 0, NLR 0.25, PPV 100%, NPV 88.24%) and an HV > 70% (p=0,001; Se 100%, Sp 75%, PLR 4, NLR 0, PPV 66,67%, NPV 100%). The correlation between SR >1,5 and malignancy was statistically significant (OR, 80,6; p=0,0067) as the one between HV >70% and malignancy (OR, 47,22; p=0,013). This technique was repeatable and reproducible (CV 0,08 ± 0,05 and K=1 for the SR; CV 0,09 ± 0,06 and K=0,67 for the HV). Strain elastography can differentiate malignant from benign canine hypoechoic splenic lesions less then 4 cm width. Twenty-one dogs presenting mammary, underwent B-mode ultrasonographic and elastographic evaluation. Each mammary lesion was then classified according to the Tsukuba score, the presence /absence of infiltration on the elastogram and to the elastogram/Bmode ratio. The Pearson’s chi-square test was used to assess the presence of a statistically significant difference between the benign or malignant tumors according to the Tsukuba score results. The Fisher’s exact test was used to assess the presence of statistically significant difference between the benign or malignant tumors according to the elastogram/B-mode ratio. Values of p ≤0,05 were considered significant. The K of Cohen was used to verify the agreement between the elastosonographic assessment of infiltration and the histological confirmation of tumors invasion. The Pearson’s chi-square test did not reported significant differences between groups (p=0,278) even considering the assessment of the elastosonographic infiltration. The K of Cohen presented a value of 0,384 corresponding to a poor agreement. The assessment of the elastogram/B-mode ratio was not possible. Finally the Strain Elastography was as an applicable technique in evaluating mammary neoplasms in our sample, demonstrating their elastographic patterns; but it was clinically not useful in differentiating benign from malignant lesions. Sixty nodular skin lesions from 36 canine patients were evaluated using B-mode ultrasonographic and elastographic evaluation. Each lesion was classified using 2 score systems by a software and then subjectively by three operators. The K of Cohen was used to verify the agreement between the elastosonographic assessment of the three operators. The Student t-test was used to assess whether there was a statistically significant difference between benign/malignant considering the hardness value calculated using the software. The Pearson chi-square test was used to assess the existence of statistically significant differences between benign and malignant lesions considering the two score proposed above. Values of p < 0,05 were considered significant. The result obtained in the Student's t test and Pearson’s chi square test allow us to say that there is a statistically significant difference between benign and malignant lesions evaluated by HV and score system respectively (p<0,05). Considering the inter-observer agreement we can see that among all three operators there is a very good correlation in score evaluation. From the average values calculated for the weighed K, we can see that there is a better agreement among operators than between observer and the objective score. The results obtained in this study are encouraging about the possibility of applying the elastosonography the nodular lesions of the skin. We have seen that this technique is able to differentiate benign and malignant lesions due to the change of elasticity of the tissues involved by malignant pathological processes. the very good agreement between operators and the good agreement between operators and objective score demonstrate the feasibility of this technique.