Value Of Us-Elastography In The Diagnosis Of Thyroid Nodules

Object: The primary objective of this study was to compare quantitativeUS elastography to conventional ultrasound for differentiating benign andmalignant thyroid lesions.Methods: The study included48consecutive patients with a singlethyroid nodule (33females, and15males, range22–77, mean age44.6±11.5yr).Thyroid nodules less than2cm, the exclusion criteria were cystic nodulesand nodules with coarse calcifications. All patients were euthyroid. Thepredictive value of US elastography was calculated based on the histologicalresults obtained after thyroidectomy.Thyroid US and US elastography were performed using a real-timeinstrument (Philiph IU22machine with a linear transducer with frequency of5-12MHz). The patient is placed in the supine position with a pillowunderneath the shoulders to extend the neck slightly, allowing the head to reston the examination couch. All study participants were required to hold theirbreath and avoid swallowing during the course of scanning to keep the imagestable. Each patient was examined by conventional ultrasound and real-timeUS Elastography. A careful evaluation of the following US parameters wasperformed on all thyroid nodules: location, size, speculsted margins,echogenicity (hyperechoic, isoechoic, or hypoechoic with respect to normalthyroid parenchyma, presence or absence of the halo sign); spotmicrocalcifications (presence of hyperechoic spots less than2mm, withoutacoustic shadowing)，an anteroposterior/transverse diameter(A/T) of1cm; andcolor-flow Doppler pattern that was defined as absence of blood flow(type I),perinodular and absent or slight intranodular blood flow (typeII), and markedintranodular and absent or slight perinodular blood flow(type III), RI.US elastographic measurement was performed during the USexamination, using the same real-time instrument and the same probe. All study participants were required to hold their breath and avoid swallowingduring the course of scanning to keep the image stable. The probe was placedon the neck with light pressure, and a box was highlighted by the operator thatincluded the nodule to be evaluated. The principle of US elastography is toacquire two ultrasonic images(before and after tissue compression by theprobe) and track tissue displacement by assessing the propagation of theimaging beam. Once the imaging plane was identified, ultrasonic images wereacquired for about5seconds. Using EQ for quantitative analysis. Traced arearatio=the area of the nodule in UE／the area of the nodule in US. Strainratio=strain ratio of surrounding normal tissues／strain ratio of the nodule.The US elastographic image was matched with an elasticity color scale. Theelasticity score:1Elasticity in the whole nodule.2Elasticity in a large part ofthe nodule.3Elasticity only at the peripheral part of the nodule.4Noelasticity in the nodule.5No elasticity in the nodule and in the posteriorshadowing.Statistical analysis was conducted using SPSS13.0. The sensitivity、specificity and accuracy of the method for the diagnosis of malignancy.Results obtained indifferent groups of subjects were compared using the χ2test,For all tests, a p-value <0.05was considered to indicate a statisticallysignificant difference.Results:1Pathological findingsOf48cases,16had a final diagnosis of malignancy on histology:13papillary thyroid carcinomas;2follicular carcinomas; and1medullarycarcinoma.32were benign at histology:18follicular adenomas;14hyperplastic nodules.2Conventional ultrasound25cases had diagnosis of malignancy on conventional ultrasound, of25cases,13were malignancy at histology;12were benign at histology.23caseshad diagnosis of benign on conventional ultrasound,of23cases,3weremalignancy at histology;20were benign at histology. The sensitivity, specificity and accuracy of conventional ultrasound in the diagnosis of thyroidnodules were81.3%,62.5%,69.8%.3US elastogrhphy3.1On US elastography: score1was found in21cases, all benign lesions;score2was found in5cases, all benign; score3was found in8cases,2carcinoma and6benign; score4was found in8cases, all carcinomas; andscore5was found in6cases, all carcinomas. Thus, with a final diagnosis ofcarcinoma had a score of4-5, with a sensitivity of87.5%, a specificity of100%, accuracy of95.8%. US elastography5-point scoring system was highersensitivity, specificity and accuracy compared with conventional ultrasound（P＜0.05）.3.2On the basis of traced area ratio diagnosis, using1.5as the cutoff point.19cases had diagnosis of malignancy on traced area ratio (the ratio of tracedarea＞1.5), of19cases,10were malignancy at histology;9were benign athistology.29cases had diagnosis of benign on traced area ratio, of29cases,6were malignancy at histology;23were benign at histology. Thus, using1.5asthe cutoff point, with the sensitivity, specificity, accuracy were62.5%,71.9%,68.8%. The results of US elastography traced area ratio measurement methodand conventional US measurement method were no difference（P＞0.05）.3.3On the basis of strain ratio diagnosis, using3.79as the cutoff point.15cases had diagnosis of malignancy on strain ratio(the strain ratio≥3.79), all of15cases were malignancy at histology.33cases had diagnosis of benign onstrain ratio, of33cases,1was malignancy at histology;32were benign athistology. Thus, using3.79as the cutoff point, with the sensitivity,specificity,accuracy were93.8%,100%,97.9%. The UE strain ratio diagnosis was highersensitivity，specificity and accuracy compared with conventional ultrasound（P＜0.05）.3.4Strain ratio was the most predictive of malignancy (sensitivity93.8%specificity100%accuracy97.9%; P＜0.0125)Conclusions:In conclusion, the stain ratio assessment method can semiquantitatively evaluate the stiffness of solid thyroid lesions using the surrounding thyroidtissue as a reference. It is simple and convenient for clinical use. With3.79asthe cutoff point, we could accurately identify malignant and benign lesions.Therefore, the sonoelastographic strain index can be used as a supplementarymeasure for differentiating benign and malignant thyroid lesions. But Largerprospective studies are needed to confirm these results and establish thediagnostic accuracy of this new technique.