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Thứ Sáu, 27 tháng 4, 2012

JUM May 2011


Figure 9. Problems that can be encountered with shear wave elastography include no signal within the lesion, which can occur because the push pulse does not start a shear wave in the mass because of the lesion depth. A, Invasive ductal carcinoma that does not have a shear wave signal (no color with the lesion) because the shear wave did not form.  B, Simple cyst. Shear waves cannot propagate in simple cysts and therefore are not color coded on the shear wave elastogram. If the cyst is complicated, the shear wave may propagate and will be color coded blue (low kPa value). Precompression can markedly affect the kPa value of a lesion. With increased precompression, all lesions become stiffer and therefore code with a higher kPa value.  C, In shear wave elastography, when precompression is applied, one may see areas with high kPa values in the near field.
D, Cyst with varying degrees of precompression. Note that the cyst has higher kPa values with increasing precompression and with marked precompression has a kPa value indicating malignancy. Precompression must be avoided with both elasticity imaging and shear wave elastography to obtain accurate results.


Abstract

Objectives—This study aimed to evaluate the diagnostic value of acoustic radiation force impulse (ARFI) elasticity imaging for differentiating between benign and malignant thyroid lesions.

Methods—Hospitalized patients needing thyroid surgery were evaluated. After routine thyroid sonography, the patients underwent ARFI elasticity imaging. Virtual Touch tissue imaging (VTI) and Virtual Touch tissue quantification (VTQ; Siemens Medical Solutions, Mountain View, CA) were used to qualitatively and quantitatively analyze the elasticity and hardness of nodules. For statistical analysis, the Student t test, analysis of variance, and the χ2 test were used to compare the elastic parameters.

Results—Of the 98 thyroid nodules observed in 72 hospitalized patients, 56 were nodular goiters, 16 thyroid adenomas, 4 thyroiditis, and 22 thyroid malignancies, with mean VTQ values ± SD of 2.034 ± 0.484, 1.835 ± 0.364, 2.293 ± 0.787, and 3.941 ± 1.393 m/s, respectively. The elastic parameters of malignant nodules were significantly higher than those of benign nodules (P < .001) and the surrounding thyroid parenchyma (P < .001). There was no significant difference between the VTQ value of benign nodules and that of the surrounding normal thyroid parenchyma (P > .05). For differentiating between benign and malignant nodules, the sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accordance rate were 86.36%, 93.42%, 79.17%, 95.95%, and 91.84% based on the standard VTQ value (2.555m/s). In total, 77.6% (59 of 76) of the benign nodules showed softer and equal images in the VTI mode, and 77.3% (17 of 22) of the malignant nodules showed stiffer images (P < .001).

Conclusions—Acoustic radiation force impulse imaging has high sensitivity and specificity in evaluating benign and malignant thyroid nodules and therefore had good diagnostic value in clinical applications.

See ARFI IMAGING of THYROID NODULES at MEDIC CENTER

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