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Contrast-enhanced ultrasonography of the kidney: a quantitative analysis of real-time perfusion imaging of the normal cortex and tumors

      Objective: The aim of this study was to evaluate quantitatively the efficacy of real-time contrast-enhanced sonography of normal cortex and renal masses using a FSO69 (Optison®, Mallinckrodt, USA) comparing harmonic (HI) and pulse inversion imaging (PII).
      Methods: 24 patients with a renal mass were studied at baseline and after 2 bolus injections of Optison® (1, 2, 3, and 4 ml, randomized dose) using HI and PII (HDI 5000, C5-2 probe, Philips ATL, Bothell, USA) at low mechanical index. The cortical and solid mass enhancement was calculated in HDI Lab software for each modality as the difference between the signal intensity of a ROI located upon the normal cortex and the mass before and after injection. Final diagnosis was obtained by CT, MRI, and/or surgery (adenocarcinomas = 16, complex cysts = 5, hamartomas = 3).
      Results: Cortical enhancement correlated with the dose (r = 0.98) for each modality and was consistently greater at mechanical index lower than 0.4. Normal and atypical cyst detection and renal mass delineation improved. Necrosis pattern was comparable to CT and MR. Contrast enhancement of normal cortex and solid renal masses as well as contrast ratio between renal mass and adjacent cortex was greater for PII compared to HI. Peak enhancement in PII was: 9.6 dB ± 4.0 dB for cancers, 5.8 ± 3.5 dB for hamartomas, and 0.8 ± 0.5 dB for complex renal cysts.
      Conclusions: Following FSO69 injection, PII appeared more effective than HI. PII of renal masses improved the detection and the characterization of renal masses, particularly for small tumors and complex cysts.