title: Quantitative Assessment of Free Flap Viability with CEUS Using an Integrated Perfusion Software.
abstract: OBJECTIVE
  New treatment strategies in oncology and trauma surgery lead to an increasing demand for soft tissue reconstruction with free tissue transfer. In previous studies, CEUS was proven to detect early flap failure. The aim of this study was to detect and quantify vascular disturbances after free flap transplantation using a fast integrated perfusion software tool.
  
  
  METHODS
  From 2011 to 2013, 33 patients were examined by one experienced radiologist using CEUS after a bolus injection of 1-2.4 ml of SonoVue(®). Flap perfusion was analysed qualitatively regarding contrast defects or delayed wash-in. Additionally, an integrated semi-quantitative analysis using time-intensity curve analysis (TIC) was performed. TIC analysis of the transplant was conducted on a centimetre-by-centimetre basis up to a penetration depth of 4 cm. The 2 perfusion parameters "Time to PEAK" and "Area under the Curve" were compared in patients without complications vs. patients with minor complications or complete flap loss to figure out significant differences. TtoPk is given in seconds (s) and Area is given in relative units (rU) Results: A regular postoperative process was observed in 26 (79%) patients. In contrast, 5 (15%) patients with partial superficial flap necrosis, 1 patient (3%) with complete flap loss and 1 patient (3%) with haematoma were observed. TtoPk revealed no significant differences, whereas Area revealed significantly lower perfusion values in the corresponding areas in patients with complications. The critical threshold for sufficient flap perfusion was set below 150 rU.
  
  
  CONCLUSIONS
  In conclusion, CEUS is a mobile and cost-effective opportunity to quantify tissue perfusion and can even be used almost without any restrictions in multi-morbid patients with renal and hepatic failure.
authors.affiliation: Center of Plastic-, Hand- and Reconstructive Surgery, University hospital, Regensburg, German.
authors.forename: S
authors.initials: S
authors.lastname: Geis
authors.affiliation: Center of Plastic-, Hand- and Reconstructive Surgery, University hospital, Regensburg, German.
authors.forename: S
authors.initials: S
authors.lastname: Klein
authors.affiliation: Center of Plastic-, Hand- and Reconstructive Surgery, University hospital, Regensburg, German.
authors.forename: L
authors.initials: L
authors.lastname: Prantl
authors.affiliation: Center of Plastic-, Hand- and Reconstructive Surgery, University hospital, Regensburg, German.
authors.forename: J
authors.initials: J
authors.lastname: Dolderer
authors.affiliation: Center of Plastic-, Hand- and Reconstructive Surgery, University hospital, Regensburg, German.
authors.forename: P
authors.initials: P
authors.lastname: Lamby
authors.affiliation: Interdisciplinary ultrasound department, University hospital, Regensburg, Germany.
authors.forename: E-M
authors.initials: EM
authors.lastname: Jung
mesh_terms: D005260:Female; D058752:Free Tissue Flaps / Q000098:blood supply* / Q000473:pathology / Q000601:surgery*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008833:Microcirculation / Q000502:physiology; D008875:Middle Aged; D009336:Necrosis; D010743:Phospholipids; D011183:Postoperative Complications / Q000000981:diagnostic imaging / Q000473:pathology; D012984:Software; D013459:Sulfur Hexafluoride; D014022:Tissue Survival / Q000502:physiology*; D018615:Ultrasonography, Doppler, Color / Q000379:methods*
chemical_list: D010743:Phospholipids; C420843:contrast agent BR1; D013459:Sulfur Hexafluoride