Ultraschall Med 2016; 37 - PS4_07
DOI: 10.1055/s-0036-1587852

Two-Dimensional Us Elastography for focal lesions in liver phantoms: influencing factors for stiffness measurement of small lesions

WK Jeong 1, JA Hwang 1, JE Lee 1, JB Kim 1
  • 1Samsung Medical Center, Radiology, Seoul, Korea, Republic of

Purpose: To determine accuracy and influencing factors of stiffness value of focal lesions in the phantoms using 2-D USE.

Materials and methods: Using two customized phantoms with different elasticity (4 ± 1 kilopascal [kPa], mimicking normal liver; 15 ± 2 kPa, mimicking liver cirrhosis [LC]) which have 9 spherical hypoechoic inclusions with same elasticity (23 ± 3 kPa), different size (20 mm, 15 mm and 10 mm in a raw) and different depth (3 cm, 5 cm and 7 cm). Mean stiffness and standard deviation (SD) in ROI were acquired, and the shape of inclusion was also assessed with a qualitative 5-graded scoring system about target visualization on color map. As possible influencing factors, the type of background phantom, depth of inclusions, size of inclusions, and observers were considered. We compared by Kruskal-Wallis test, and performed multiple regression tests to detect significant influencing factors about 2-D USE.

Results: Measured mean stiffness value was significantly higher in LC phantom (10.50 kPa in normal, 13.81 kPa in LC; p = 0.013), inclusions in 7 cm of depth (10.94 kPa in 3 cm, 11.20 kPa in 5 cm and 15.59 kPa in 7 cm; p = 0.001). In multiple regression analysis in mean stiffness, there was significant difference of mean stiffness in type of phantom, depth and size of inclusions. Mean SD in ROI was also significantly larger in 7 cm of depth (0.86 kPa in 3 cm, 1.23 kPa in 5 cm and 3.94 kPa in 7 cm; p = 0.001). In multiple regression analysis for SD in ROI, there were significant differences in type of phantom and depth of inclusions. Morphologic score was significantly different only in aspect of the size of inclusion bodies (p < 0.001). Background stiffness was not different according to depth or observers (p = 0.491 and 0.522, respectively).

Conclusion: 2-D USE for focal lesion evaluation could be influenced by different background stiffness, deep position of the lesion, and small size of lesion.