Spoke-wheel sign of focal nodular hyperplasia revealed by superb micro-vascular ultrasound imaging

A 40-year-old man came to the hospital for follow-up of right hepatic tumor known for 3 years. His medical history is unremarkable. He received physical check-up 3 years ago and a 3.8 cm isoechoic hepatic tumor was found during the ultrasound examination. The previous abdominal computed tomography revealed a well-defined tumor with central scarring tumor in the right liver (Figure 1a). The tumor showed hyperdensity during heptic arterial phase and isodensity during delayed phase. A diagnosis of focal nodular hyperplasia was made. During this ultrasound examination, the tumor was well-defined with slightly hyperechoic pattern and no interval change in size. On color Doppler, a signal from central feeding was detected. When switching to the superb micro-vascular imaging (SMI) mode of the recently developed ultrasound system (Toshiba’s Aplio 500 ultrasound system), a ‘spoke-wheel sign’ can be clearly visualized with a central feeding vessel and multiple small vessels radiating to the peripheral of the tumor (Figure 1b). The patient was advised for yearly ultrasound follow-up.