Acoustic Radiation Force Impulse (ARFI) Elastography of Focal Splenic Lesions: Feasibility and Diagnostic Potential

SIMPLE SUMMARY: Nontraumatic focal splenic lesions (FSL) are rare, and the need for tissue diagnosis must be weighed against the risk of complication after a splenic biopsy. The aim of this retrospective study was to explore the diagnostic potential of acoustic radiation force impulse elastography (ARFI) as a noninvasive method for benign and malignant FSL. Therefore, 34 patients were examined by B-mode ultrasound, contrast-enhanced ultrasound and ARFI. Diagnostic confirmation of FSL was based on histological examination or clinical evaluation with follow-up. Although the lesions’ stiffness was significantly lower than that of the normal splenic parenchyma, regardless of the FSL etiology, the differentiation between benign and malignant FSLs was not possible. ABSTRACT: Purpose: Nontraumatic focal splenic lesions (FSL) are rare, and the need for tissue diagnosis must be weighed against the very high risk of bleeding after a splenic biopsy. The aim of this study was to explore the feasibility and diagnostic potential of acoustic radiation force impulse (ARFI) elastography as a noninvasive method for different benign and malignant FSLs. No human studies on the elastographic characteristics of FSL exist. Methods: This was a retrospective analysis of 34 patients with FSLs, who underwent abdominal B-mode ultrasound (B-US), contrast-enhanced ultrasound (CEUS), and standardized ARFI examinations between October 2021 and December 2022 at our university hospital. The inclusion criteria were: (i) FSL size ≥ 1 cm; (ii) 10 valid ARFI measurements of the FSL, as well as of the normal splenic parenchyma (NSP) as an in vivo reference; and (iii) diagnostic confirmation of FSL etiology based on histological examination (8/34; 23.5%) or clinical evaluation, which included a clinical and sonographic follow-up (FU), CEUS morphology, and/or morphology on cross-sectional imaging (26/34; 76.5%). CEUS was performed on all patients and the FSLs were classified according to the current guidelines; cross-sectional imaging was available for 29/34 (85.3%). The mean FU duration was 25.8 ± 30.5 months. The mean ARFI velocity (MAV) of the FSL (MAV(L)), the NSP (MAV(P)), and the ratio of the MAV(L) to the MAV(P) (MAV(L/P)) were calculated and compared. Results: Of the 34 FSLs, 13 (38.2%) were malignant (mFSL) and 21 (61.8%) were benign (bFSL). The MAV(L) of all 34 FSLs (2.74 ± 0.71 m/s) was lower than the MAV(P) (3.20 ± 0.59 m/s), p = 0.009, with a mean MAV(L/P) ratio of 0.90 ± 0.34. No significant differences in the MAV(L) were observed between the mFSL (2.66 ± 0.67 m/s) and bFSL (2.79 ± 0.75 m/s). There were also no significant differences between the MAV(P) in patients with mFSL (3.24 ± 0.68 m/s) as compared to that in the patients with bFSL (3.18 ± 0.55 m/s). Likewise, the MAV (L/P) ratio did not differ between the mFSL (0.90 ± 0.41 m/s) and bFSL (0.90 ± 0.30 m/s) groups. Conclusion: ARFI elastography is feasible in evaluating the stiffness of FSLs. The lesions’ stiffness was lower than that of the NSP, regardless of the FSL etiology. However, differentiation between benign and malignant FSL with the help of this elastographic method does not appear possible. Larger prospective studies are needed to validate these findings.