Osteocutaneous free flaps: a critical analysis of quantitative evaluation of bone microcirculation with contrast-enhanced high resolution ultrasound (hrCEUS) and TIC analysis

PURPOSE

Osteocutaneous free flaps (OFF) are widely used to reconstruct large bone defects in trauma and cancer surgery. Currently no monitoring method is available to detect blood circulation around and inside the bone after transplantation. Therefore we used for the first time contrast-enhanced high-resolution ultrasound (hrCEUS) to gain evidence for the microcirculation of the transplanted bone.

MATERIALS AND METHODS

15 patients transplanted with OFF because of large bone defects at different sites were examined postoperatively with hrCEUS with a high resolution linear probe (6-9 MHz, LOGIQ E9/GE) and a bolus injection of 2.4 ml of contrast agent (SonoVue®, Bracco, Italy). Operation and examination were performed by either an experienced plastic surgeon or an experienced ultrasound examiner. Microcirculation of the periost and bone was analyzed in different regions of interest (ROIs) and quantitative microcirculation analysis was performed using time intension curve analysis (TIC). We further analyzed clinical outcome of the patients in respect to revision-surgery, necrosis of the OFF and flap survival as well as viability on standard x-rays 2 months after surgery.

RESULTS

The most representative parameter by TIC analysis of hrCEUS were the area under the curve (AUC) and the time to peak (Ttop). The AUC of the periost and central part of the bone showed a high correlation (Pearson's r = 0.831). Mean AUC for the periost was 163.92 dB ± 49.44 and for the central part of the bone 70.42 dB ± 25.33. The Ttop of the periosteal ROI was 33.04 sec. ± 6.71 and the bone ROI 41.01 sec. ± 9.24. There was a high correlation of the Ttop of the periost and bone (Pearson's r = 0.937). One revision had to be performed due to haematoma and microcirculation defect of the distal part of the transplanted bone graft which was detected early by hrCEUS and the distal part of the avital bone could be removed timely.

CONCLUSION

For the first time we could show that hrCEUS is a reliable method to evaluate the viability of OFF. The AUC and Ttop seem to be a valuable parameter to detect the microcirculation around and inside the bone transplant.

Image fusion of contrast enhanced ultrasound (CEUS) with computed tomography (CT) or magnetic resonance imaging (MRI) using volume navigation for detection, characterization and planning of therapeutic interventions of liver tumors

AIM

To evaluate, whether image fusion of contrast enhanced ultrasound (CEUS) with CT or MRI affects the diagnosis and characterization of liver lesions or the therapeutic strategy of surgical or interventional procedures compared to the preliminary diagnosis.

MATERIAL AND METHODS

In a retrospective study the image fusion scans of CEUS with contrast enhanced CT or MRI of 100 patients (71 male, mean age 59 years, 0.3-85 years) with benign or malignant liver lesions were evaluated. Fundamental B-scan, color Doppler imaging and CEUS were performed in all patients by an experienced examiner using a multifrequency convex transducer (1-5 MHz, LOGIQ 9/GE) and volume navigation (Vnav). After a bolus injections of up to 2.4 ml SonoVue® (BRACCO, Italy) digital raw data was stored as cine-loops up to 5 min. In 74 patients, CEUS was fused with a pre-existing ceCT, in 26 patients a ceMRI was used.

RESULTS

In all 100 patients (100%) the image quality in all modalities (ceCT, ceMRI and CEUS) was excellent or with only minor diagnostic limitations. Regarding the number of lesions revealed in image fusion of CEUS/ceCT/ceMRI and the preceding diagnostic method, concordant results were found in 84 patients. In 12 patients, additional lesions were found using fusion imaging causing subsequently a change of the therapeutical strategy. In 15 out of 21 patients with either concordant or discordant results regarding the number of lesions, image fusion allowed a definite diagnosis due to a continuous documentation of the microcirculation of the tumor and its contrast enhancement. A significant coherency (p < 0.05) among image fusion with either ceCT or ceMRI and CEUS and a subsequent change of therapeutic strategy was found.

CONCLUSION

Image fusion with volume navigation (VNav) of CEUS with ceCT or ceMRI frequently allows a definite localization and diagnosis of hepatic lesions in patients with primary hepatic carcinoma or metastatic diseases. This might cause a change of the therapeutic strategy in many patients with hepatic lesions.

Contrast-enhanced ultrasound improves real-time imaging of ablation region during radiofrequency ablation: preliminary results

PURPOSE

To assess the added value of depicting tumour microvascularisation, using dynamic contrast enhanced (CEUS), during radiofrequency ablation, as a means of achieving a complete ablation (CA) of malignant liver lesions.

MATERIAL AND METHODS

18 consecutive patients (2 female, 16 male, age range 52-79 years, mean 64.1 ± 9.9 years) with 22 histologically confirmed hepatic malignancies (HCC: n = 10, liver metastases: n = 12) underwent RFA. Before RFA treatment, conventional US, CEUS and contrast enhanced CT (ceCT) of the liver were performed. During the CT-guided RFA procedure, CEUS was performed to asses the ablation defect. In case of partial ablation a subsequent ablation was performed with a corrected electrode position and evaluated again using CEUS. This procedure was repeated until a CA was achieved. The number of ablations per patient was recorded. Secondary efficacy parameters assessed were lesion detectability in the different imaging modalities and contrast phases.

RESULTS

Overall intraprocedural CEUS led to a change in therapeutic management in 59% of cases, resulting in 17 additional ablation cycles. Lesion detectability during CT Fluoroscopy was the sole statistical significant predictor of incomplete ablations (p = 0.008). The mean number of ablations for detectable lesions was 1.27 vs. 2.27 ablations for not detectable lesions (p = 0.002). The combined CT and CEUS RFA procedure led to a CA for all treated lesions in follow up 3 month post intervention.

CONCLUSION

CEUS does allow a reliable and immediate assessment of therapeutic efficacy of percutaneous RFA procedures of malignant liver lesions, through the continuous dynamic evaluation of tumour microcirculation.

Evaluation of the microcirculation of hepatocellular carcinomas using contrast-enhanced ultrasound with intraarterial and intravenous contrast application during transarterial chemoembolization with drug-eluting beads (DEB-TACE): preliminary data

PURPOSE

The objective was the evaluation of microcirculation in hepatocellular carcinomas (HCC) in vivo by dynamic contrast-enhanced ultrasound (CEUS) after intravenous (i.v.) and intraarterial (i.a.) application of contrast agent during transarterial chemoembolization (TACE) using drug-eluting beads (DEB).

PATIENTS AND METHODS

Eleven patients with HCC underwent CEUS directly before and immediately after DEB-TACE. The sonographic contrast agent was injected through the microcatheter intraarterially and intravenously. The grade of hypervascularization was evaluated before Bead application. The percentage of devascularization after Bead application was calculated and quantitative devascularization was carried out using time intensity curves (TIC). These results were compared to postinterventional angiography after Bead application and postprocedural computed tomography.

RESULTS

The hypervascularization of HCC was marginal improved after i.a. contrast application compared to i.v. application (p = 0.163). The reduction of vascularization after Bead application correlated significant between i.a. and i.v. contrast application (p = 0.007) and decreased significant using TIC analysis (p = 0.003). Postinterventional angiography related with CEUS after i.a. sonographic contrast agent application. Extrahepatic tumor-feeding arteries were detected by a mismatch between i.a. and i.v. CEUS in one case.

CONCLUSION

Quantification of the reduction of microvascularization using TIC analysis may be a valuable periinterventional tool during DEB-TACE. Intraprocedural CEUS with i.a. and i.v. ultrasound contrast agent injection may help finding extrahepatic tumor-feeding arteries.

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

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.

Post-operative monitoring of tissue transfers: advantages using contrast enhanced ultrasound (CEUS) and contrast enhanced MRI (ceMRI) with dynamic perfusion analysis?

BACKGROUND

The immediate evaluation of microvascular tissue flaps with respect to microcirculation after transplantation is crucial for optimal monitoring and outcome. The purpose of our investigation was to evaluate the clinical value of contrast-enhanced ultrasound (CEUS) and contrast-enhanced MRI (ceMRI) for monitoring the integrity of tissue flaps in plastic surgery.

METHODS

To this end, we investigated 10 patients (47 ± 16 a) between postoperative day 7 and 14 who underwent flap surgery in order to cover tissue defects in various body regions. For CEUS we utilized the GE LOGIQ E9 equipped with a linear transducer (6-9 MHz). After application of 2.4 ml SonoVue, the tissue perfusion was detected in Low MI-Technique (MI < 0.2). The perfusion curves were quantitatively analyzed using digital video sequences (QONTRAST, Bracco, Italy) regarding peak % and relative blood flow (RBF). Furthermore, we investigated all tissue flaps using contrast-enhanced MRI (Magnetom Symphony TIM, Siemens) with a 3D-VIBE sequence and a time resolution of 7s. Thus, the transplants were completely captured in all cases. As perfusion parameters, the positive enhancement integral (PEI) as well as the maximum intensity projection time (MIP-time) were collected. For comparison of both applications, all parameters were displayed in color-coded resolution and analyzed by three independent readers. Depending on the flap thickness, 1-3 regions of interest (ROI) were investigated. Each ROI measured 1 × 3 cm.

RESULTS

The subcutaneous ROI-1 showed a significantly lower rating regarding RBF in the ceMRI compared to CEUS (Mann-Whitney Rank-Sum test, p < 0.05). ROI-2 and -3 did not show any significant differences between the two applications. The frequency distribution showed good accordance in both modalities. Both imaging techniques detected 1 partial flap necrosis within the random area of cutaneous and subcutaneous layers, 1 hematoma as well as 1 insufficient perfusion over all tissue layers. After subsequent reoperation, graft loss could be prevented.

CONCLUSION

At present, both technologies provide an optimal assessment of perfusion in cutaneous, subcutaneous and muscle tissue layers, whereby the detection of fatty tissue perfusion is currently more easily detected using CEUS compared to ceMRI.

Comparison of time-intensity-curve- (TIC-) analysis of contrast-enhanced ultrasound (CEUS) and dynamic contrast-enhanced (DCE) MRI for postoperative control of microcirculation in free flaps - first results and critical comments

Postoperative monitoring of transplanted free flaps is an essential tool to reveal possible complications. The aim of this study was to compare the value of time-intensity-curve- (TIC-) analysis based on grey scale data of contrast-enhanced ultrasound (CEUS) and dynamic contrast-enhanced (DCE-) magnetic resonance imaging (MRI). Postoperative imaging was performed in 11 patients following free flap transplantation and TIC analysis was obtained in identical regions of interest (ROI) of CEUS and DCE MRI data. Microcirculation was assessed in superficial (0-1 cm), middle (1-2 cm), and deep (2-3 cm) ROIs in one or two different positions within the flap resulting in a total of 46 ROIs evaluated (in very thin flaps only superficial and middle ROIs were assessed). For both imaging methods, mean signal increase was found to be significantly higher in ROIs of normally perfused flaps (n = 40) compared to ROIs with compromised microcirculation (n = 6). Although TIC analysis allows quantification of microcirculation in different regions of the flap, in this preliminary study no distinct threshold could be defined to differentiate flaps with normal and compromised microcirculation.

[Contrast-enhanced sonography. Therapy control of radiofrequency ablation and transarterial chemoembolization of hepatocellular carcinoma]

Due to the imaging of dynamic perfusion, hepatocellular carcinoma can be detected with a sensitivity of >90% using contrast-enhanced sonography. The characterization of liver tumors with contrast-enhanced sonography is comparable to the diagnostic accuracy of contrast-enhanced computed tomography. The dynamic detection of microvascularization with contrast-enhanced sonography allows the differentiation between vascularized tumors and non-vascularized necrotic lesions before, during and after transarterial chemoembolization or percutaneous radiofrequency ablation. Image fusion with volume navigation can be useful in the followup control.

[Plain abdominal radiograph - is there any additional clinical value based on the supine projection?]

BACKGROUND

To assess the diagnostic value of an additionally acquired plain abdominal radiograph in supine position.

MATERIALS AND METHODS

Two experienced radiologists evaluated retrospectively 2148 consecutive patients having plain abdominal radiographs acquired in a tertiary care center. There were 1385 patients having an erect view and 763 patients with a left lateral decubitus view. All patients had a second examination in supine position. First the radiographs in erect or decubitus view were evaluated regarding the presence and details of pathological changes. After 4 weeks all radiographs including the supine view were evaluated again. Next to pathological changes the additional value of the supine projection was assessed. The results were compared and the additional diagnostic value using the supine view was noted.

RESULTS

We evaluated 2148 patients having a plain abdominal radiograph (1325 men, 823 women, mean 58.9 years, range 15-96 years). The average age within the group acquired with left decubitus view was 61.1 years, while patients having an erect view had a mean age of 57.0 years. For the first evaluation we found pathological changes in 10.5% (decubitus view: 13.1%, erect view 9.5%; p = 0.01). The most frequent diagnosis was ileus (7.7%) followed by abdominal free air (2.4%). The results were confirmed during the second reading in 99.2%. In 3.5% (decubitus view 5.8%, erect view 2.2%) more anatomical structures were depicted considering the supine projection and the decubitus/erect projections. The anatomical information was in no case relevant for the diagnosis.

CONCLUSION

Having the information of an supine view additionally to an decubitus/erect view increases the depiction of anatomical structures up to 5.8%. Nevertheless there was no additional diagnostic relevant information based on the supine view.

Characterization of microvascularization of liver tumor lesions with high resolution linear ultrasound and contrast enhanced ultrasound (CEUS) during surgery: First results

AIM

Evaluation of high resolution linear ultrasound and intra-operative linear contrast enhanced ultrasound (CEUS) and its benefit for the detection and characterization of tumor lesions.

MATERIAL AND METHODS

Twenty patients were investigated preoperatively regarding tumor detection using CT (n = 8) or MRI (n = 12) and image fusion (VNav) (n = 3). All patients had surgery for their hepatic tumor (hepatocellular carcinoma (HCC), cholangiocellular carcinoma (CCC), metastasis, and adenoma). Ultrasound was performed intra-operatively first with B-scan using a convex probe. Than multifrequency linear transmitters (6-9 MHz, 6-15 MHz, LOGIQ E9, GE) were applied for B-scan, coulor coded Doppler sonography (CCDS) and Power Doppler followed by dynamic CEUS with Contrast Harmonic Imaging (CHI) after bolus injection of a maximum of 15 mL SonoVue®.

RESULTS

In 9 cases with the use of intra-operative CEUS additional tumor lesions (diameter 4-15 mm) could be detected and were histologically confirmed after surgical resection (7 cases) or intra-operative biopsy (2 cases). Using intraoperative CEUS 64 tumor lesions could be detected compared to 51 tumor lesions detected by preoperative CT or MRI (p < 0.05). Using the 6-15 MHz multifrequency linear transducer with CHI, arterial perfusion of adenomas, neuroendocrine metastases and HCC lesions was detectable. In 3 cases a resection was not achievable. Two of these cases were treated with radio frequency ablation (RFA). The other case had no curable option due to multifocal tumor manifestation.

CONCLUSION

The intra-operative use of high-resolution linear transducer techniques with CEUS offers new diagnostic perspectives for an effective liver surgery.

Image fusion with volume navigation of contrast enhanced ultrasound (CEUS) with computed tomography (CT) or magnetic resonance imaging (MRI) for post-interventional follow-up after transcatheter arterial chemoembolization (TACE) of hepatocellular carcinomas (HCC): Preliminary results

AIM

The assessment of the immediate post-interventional microcirculation and perfusion following transcatheter arterial chemoembolization (TACE) with new real time imaging fusion technique (VNav) of computed tomography (CT) or magnetic resonance imaging (MRI) with contrast enhanced ultrasound (CEUS) compared to follow-up.

MATERIAL

Following TACE an image fusion of CEUS with CT or MRI of the liver was performed in 20 patients (18 men, 2 women; age 29-75 years) with confirmed hepatocelluar carcinoma (HCC) to evaluate the post-interventional tumor vascularization and perfusion of HCC tumor lesions. Image fusion with CEUS performed immediately was compared with the result at the end of TACE (DSA), with post TACE CT (non-enhanced CT within 24 hours) and with follow up CT (enhanced CT after 6 weeks) after embolization. Ultrasound was performed using a 1-5 MHz multifrequency SonoVue transducer (LOGIQ 9/GE) after a bolus injection of 2-4ml SonoVue® with contrast harmonic imaging (CHI). Thirteen examinations were fused with a contrast enhanced CT, 7 with a MRI performed before TACE.

RESULTS

The post-interventional volume navigation image fusion of CT or MRI with CEUS showed differences regarding the residual tumor perfusion compared to other modalities. The correlation (Spearman-test) between the perfusion result at the end of TACE, non-enhanced CT after TACE and image fusion with CEUS was 0.42 and 0.50. The difference between the result at the end of TACE and the fusion with CEUS was significant (p < 0.05, Wilcoxon-test). The correlation between fusion of CEUS with CT/MRI and follow-up CT (after 6 weeks) was 0.64, the difference was not significant (p > 0.05). The differences between native CT within 24 hours after TACE and follow up CT after 6 weeks or fusion of CEUS and CT/MRI were significant (p < 0.05). The inter-observer variability was 0.61 at the end of TACE, 0.58 at non-enhanced CT (within 24 hours), 0.87 at fusion CEUS with CT/MRI and 0.74 at follow up CT after 6 weeks (Cohens Kappa test).

CONCLUSION

Image fusion with volume navigation (VNav) of CEUS with CT or MRI allows an accurate localisation of foci in patients with HCC. This exact mapping permits an easier control and evaluation of the results after TACE. The fusion of CEUS and CT or MRI allows a better evaluation of the microcirculation and the residual tumor perfusion at an earlier point of time than usual modalities of therapy control like non-enhanced CT. This might lead to a more differentiated monitoring of therapy.