Abstract
Purpose: Evaluation of post-surgery tissue perfusion of free flaps of the lower leg with contrast enhanced harmonic imaging (CHI), laser-induced indocyanine green (ICG) fluorescence angiography and magnetic resonance imaging (MRI).
Materials and methods: 10 patients with free flaps of the lower limb were evaluated with CHI, ICG-fluorescence angiography and perfusion weighted MRI. Perfusion weighted MRI was performed after intravenous bolus injection of 25 ml Gd-DTPA. The ICG fluorescence was detected by a near-infrared-laser device (λem = 780 nm). Ultrasound was carried out by an experienced examiner with a linear probe after intravenous bolus injection of 2.4 ml SonoVue®. For MRI time intensity curves as well as color-coded blood volume maps of the whole free flap were qualitatively evaluated. For CHI and ICG time intensity curves in selected regions of interest were analyzed. A score from 1–5 (1 = low, 5 = excellent) was used for analysis of perfusion images by three independent readers.
Results: In 3 cases (radialis, parascapular and lateral thigh flap) CHI, MRI and ICG perfusion imaging showed an excellent (score 4–5) contrast enhancement of the cutaneous and subcutaneous part of the free flaps. In 2 cases of osteocutaneous flaps perfusion in central and distal parts of the free flaps was reduced (score 2). Correlation between CHI, MRI and ICG was 0.69–0.83 for the distal parts of the free flaps and 0.74–0.87 for the center of the flaps (Spearman test). Perfusion in the center of the free flaps was significantly different for MRI and ICG and also for MRI and CHI (p<0.05, Wilcoxon test).
Conclusion: These first results introduce CHI and MRI perfusion imaging as a promising post-surgery monitoring in patients with free flaps.