DIFFERENTIATION OF RENAL-CELL CARCINOMAS FROM ANGIOMYOLIPOMAS BY ULTRASONIC FREQUENCY-DEPENDENT ATTENUATION

Purpose: We determined the usefulness of ultrasonic frequency dependen t attenuation in differentiating hyperechoic renal cell carcinoma from angiomyolipoma.Materials and Methods: Frequency dependent attenuation values were determined in 29 renal cell carcinomas and 13 angiomyolip omas. Results: Frequency dependent attenuation values were significant ly lower in renal cell carcinomas than in angiomyolipomas (0.42 versus 0.76 dB./cm./MHz.). Two of the renal cell carcinomas were as hyperech oic as the angiomyolipomas but they were clearly differentiated by the low frequency dependent attenuation. Two other renal cell carcinomas exhibited high values because of the abundance of fibrous tissue. Howe ver, they were readily diagnosed by the typical low echoic B-mode imag es. Frequency dependent attenuation did not differ between histologica l types of renal cell carcinoma. One angiomyolipoma that was poor in f at and rich in muscle components had an exceptionally low frequency de pendent attenuation. Therefore, frequency dependent attenuation values can be regarded as an inversion of computerized tomography numbers. C onclusions: Frequency dependent attenuation measurement is a promising diagnostic aid in differentiating hyperechoic renal cell carcinomas f rom angiomyolipomas.