Characterization of Renal Tumours with Pulse Inversion Harmonic Imaging by Intermittent High Mechanical Index Technique: Initial Results

Our objective was to evaluate whether contrast-specific ultrasound (US) technique pulse inversion harmonic imaging (PIHI) with Levovist could reveal differential morphological features in solid and cystic renal masses. Twenty-six renal masses in 26 patients were evaluated by PIHI after Levovist injection with intermittent high mechanical index stimulation, performed every 10-15 s during arterial and delayed phase. Helical CT (HCT; n=6) or histological findings on surgical/bioptic specimen ( n=20) were considered as the reference procedures for definitive diagnosis. Eleven solid renal cell carcinomas (RCCs), 1 embryonal matanephric adenoma (EMA), 7 angiomyolipomas (AMLs), 4 cystic RCCs and 3 complex inflammatory cysts were identified. Solid RCCs revealed a much higher ( p<0.05) contrast enhancement than AMLs with typical pattern on conventional US ( n=6). The EMA and AML with atypical pattern on conventional US ( n=1) revealed intense contrast enhancement during arterial phase, progressively decreasing during delayed phase. Cystic RCCs and complex inflammatory cysts revealed intense contrast enhancement on the peripheral thick wall during arterial phase decreasing on delayed phase. The PIHI has been shown to differentiate solid RCC from typical AML by contrast enhancement assessment after Levovist injection, but differential diagnosis both in solid and in cystic renal masses still remains difficult.