Assessment of bone microcirculation by contrast-enhanced ultrasound (CEUS) and [18F]-positron emission tomography/computed tomography in free osseous and osseocutaneus flaps for mandibular reconstruction: Preliminary results

Abstract

Purpose: Postsurgical evaluation of bone microcirculation in osseous and osseocutaneus free flaps by contrast enhanced ultrasound (CEUS) with time intensity curve (TIC) analysis and [¹⁸F]-positron emission tomography/computed tomography (Fluoride-PET/CT). Patients and Methods: 10 patients with osseous or osseocutaneus microvascular flaps were evaluated with CEUS. Ultrasound was carried out by an experienced examiner with a high resolution linear probe (6–9 MHz, LOGIQ E9, GE) after intravenous bolus injection of 2.4 ml SonoVue^® (BRACCO, Germany). Time intensity curves (TIC) in selected regions of interest (ROI) were analyzed and compared with the evaluation of [¹⁸F]-positron emission tomography/computed tomography and the clinical course for at least 2 month. Results: 9/10 patients showed evidence for soft tissue and osseous microcirculation of the transplants in CEUS correlating with the clinical course. The soft tissue parts of the transplant showed a mean value of 84% (range 51–98%) and the bone parts a mean value of 39% (range 11–75%) for the Area under the curve (AuC) compared with the AuC for the anastomotic vessel region. Mean values for time to peak (TTP) were 27,1 sec (range 8.7–52.0 sec) for the anastomotic vessels, 29.3 sec (range 7.9–62.0 sec) for the soft tissue of and 32.0 sec (range 7.4–69.0 sec) for the transplant bone. In 1/10 patients flap failure occurred, after denudation the bone was left as an avascular transplant. AuC showed a mean value of 0.5 % for the bone region compared with the vessel region. Fluoride-PET/CT assessed bone vitality in 7 patients as “good” in 1 patient as “uncertain” and in 1 patient as “poor”. CEUS assessment was corresponding with Fluoride-PET/CT in 4 patients, clinical assessment in 6 patients. Conclusion: Fluoride-PET/CT is a valuable tool to make an indirect statement about the perfusion of the transplanted bone and was used as control in this study. CEUS is a new and promising method for the evaluation of microcirculation of buried free microvascular bone grafts and the osseous part of osseocutaneous flaps and may be used for a steady monitoring in the first postoperative days.