Arrival time parametric imaging using Sonazoid-enhanced ultrasonography is useful for the detection of spoke-wheel patterns of focal nodular hyperplasia smaller than 3 cm

Abstract

It is considered difficult to make a definitive diagnosis of focal nodular hyperplasia (FNH) of <3 cm when using conventional diagnostic imaging modalities. Typical FNH imaging findings are: i) central scar formation, ii) nutrient vessels extending radially from the center and iii) the presence of Kupffer cells. In a clinical setting, identification of a spoke-wheel pattern formed by nutrient vessels extending radially is a key feature in the diagnosis of FNH. In this study, we investigated the detection rate of spoke-wheel patterns of FNH <3 cm using arrival time parametric imaging (At-PI) technology with Sonazoid-enhanced ultrasonography (US). Five patients with FNH <3 cm who had undergone Sonazoid-enhanced US at the Toho University Omori Medical Center between February 2008 and March 2009 were included in the study. The mean tumor diameter was 20.2±7.2 mm. Lesions were enhanced with 0.5 ml Sonazoid US contrast agent and a video of the procedure was saved and used for At-PI analysis of contrast agent dynamics in FNH. Three ultrasonographic specialists examined the images and made a diagnosis of FNH based on the findings of spoke-wheel patterns. Similarly, micro-flow imaging (MFI) was performed to evaluate the contrast agent dynamics in FNH. Using MFI, FNH was diagnosed in 3 of the 5 cases by the three specialists, whereas At-PI enabled the identification of spoke-wheel patterns in all 5 cases. At-PI using Sonazoid-enhanced US is superior for detecting spoke-wheel patterns of FNH <3 cm.

Keywords: Sonazoid; arrival time parametric imaging; contrast-enhanced ultrasonography; focal nodular hyperplasia; micro-flow imaging; spoke-wheel pattern.

Figure 1

Color scales used in arrival time parametric imaging (At-PI). (A) Parametric-color scale 1 (red, 0–0.5 sec; yellow, >0.5 sec) was used to evaluate lesions contrasted within 2 sec. (B) Parametric-color scale 2 was used for lesions requiring ≥2 sec for contrast enhancement. The scale was generated with red (0–1 sec), cyan (0–2 sec) and yellow (>2 sec).

Figure 2

Ultrasound (US) imaging of focal nodular hyperplasia (FNH) in 5 cases. Left, micro-flow imaging (MFI) and right, arrival time parametric imaging (At-PI). In (A) case 1 and (B) case 2, a spoke-wheel pattern was visible in At-PI but not in MFI. In (C-E) cases 3, 4 and 5, respectively, a spoke-wheel pattern was visible in MFI and At-PI. Arrowheads indicate the tumor.