Sung Kyoung Moon, Presenter: Nothing to Disclose

Jeong Yeon Cho MD, Abstract Co-Author: Nothing to Disclose

Seung Hyup Kim, Abstract Co-Author: Nothing to Disclose

To estimate the usefulness of Acoustic Radiation Force Impulse (ARFI) elastography imaging in the ultrasonographic differential diagnosis of small renal cell carcinoma (RCC) from angiomyolipoma (AML).

We prospectively performed ultrasonographic exams for 18 small renal tumors (<5cm) using a US machine with ARFI imaging application (Siemens ACUSON S2000™). We got virtual touch imaging (VTI) and shear wave velocity (SWV) in all tumors and adjacent renal cortex. We measured gray scales of tumors and renal cortex in VTIs on PACS and calculated the relative gray scales of tumors to renal cortex (T/KG). We categorized tumors into AML and RCC according to the conventional US findings. Tumors were finally diagnosed by surgery (9 RCCs and one AML), biopsy (one AML), and CT and MRI findings (7 AMLs). The association of ARFI imaging with the final diagnosis was statistically analyzed by using One-way ANOVA test and ROC. We assessed the accuracy of conventional US and VTI in the differential diagnosis of small RCC and AML.

Tumors were finally diagnosed as 9 RCCs and 9 AMLs. Their mean sizes were 2.48cm and 2.27cm, respectively (p>0.05). Two RCCs and 5 AMLs were not suitable for measuring SWVs due to small size. SWVs of two groups were not significantly different (2.39m/sec in RCCs and 2.32m/sec in AMLs, p>0.05). T/KG of RCCs on VTI was significantly smaller than that of AMLs (0.823 and 1.448, p=0.015). In differentiation of RCC and AML, T/KG showed sensitivity 77.8% and specificity 77.8% with cut-off value 0.961 (AUC 0.840). The accuracy of conventional US alone was 88.9% (16/18, 8 RCCs and 8 AMLs) in the differential diagnosis of RCC and AML. The accuracy of conventional US combined with VTI was 100%. VTI had the added value on conventional US in the diagnosis of two misdiagnosed cases with a chromophobe RCC and a non-fatty AML.

Although ARFI imaging alone showed limited value, adding it to conventional US might be helpful in the differential diagnosis of small RCCs from AMLs. Further studies with large population are necessary to prove its usefulness and clinical implication in the differential diagnosis of renal tumors.

ARFI imaging might be the ancillary tool in the differential diagnosis of renal tumors, especially non-fatty AMLs from RCCs.

Moon, S, Cho, J, Kim, S, Usefulness of Acoustic Radiation Force Impulse (ARFI) Elastography in the Differential Diagnosis of Small Renal Cell Carcinoma from Angiomyolipoma: Preliminary Study.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9006761.html