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.

Ultrasound-arterioportography (US-AP): A new technical approach to perform detection of liver lesions

PURPOSE

To show the feasibility of a combination of the advantages of modern contrast enhanced ultrasound (CEUS) with the technique of arterioportography to achieve the highest sensitivity of all different modalities.

MATERIAL AND METHODS

Ten patients (9 m, 1 f, age 52-73 years) with suspected hepatocellular carcinoma (HCC) in liver cirrhosis (8 ethyl toxic, 2 hepatitis) were included before transarterial chemo-embolization (TACE). In all patients during a 6-week period a double enhanced MRI (Gd-DTPA and SPIO) was performed. Before TACE a bolus <2 mL ultrasound contrast agent (SonoVue®, Bracco, Milan, Italy) was injected over a selectively placed catheter in the superior mesenteric artery (SMA) and ultrasound of the liver (2.5-4 MHz, LOGIQ 9; GE Healthcare) was performed in arterioportographic phase (US-AP). Two independent readers evaluate number, size and localisation of detected lesion in MRI and US-AP. Additional diagnostic quality of both modalities was determined using a 4-point scale (1: excellent-4: not diagnostic). Differences were analysed for significance using a t-test. Interobserver variability was calculated (κ-value).

RESULT

In all 10 patients (100 %) US-AP was feasible. Diagnostic quality was in all cases between 1-2 for both modalities and readers (MRI standard deviation (SD) -0.51, Sono-AP SD -0.421). US-AP detected with 33.5 vs. 24.5 lesions, significant more lesions than double enhanced MRI (p < 0.022). The interobserver variability was κ -0.965 for MRI and κ -0.898 for US-AP.

CONCLUSION

US-AP for detection of liver lesions is feasible. Using this technique significantly more lesions in patients with hepatocellular carcinoma could be detected in comparison to MRI with liver-specific contrast agent.

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.

MR-arterioportography: A new technical approach for detection of liver lesions

AIM: To evaluate the benefit and effectiveness of MR-arterioportography (MR-AP) to achieve the highest sensitivity for detection and evaluation of hepatocellular carcinoma (HCC).

METHODS: Twenty liver cirrhosis patients with suspected HCC were included before transarterial chemoembolization. In all patients double-enhanced Magnetic resonance imaging (MRI) was performed. A bolus of 10 mL Magnevist^® was injected through a selectively placed catheter in the superior mesenteric artery and MRI of the liver was performed in arterioportographic phase. Two independent readers evaluated number, size and localization of detected lesions. Diagnostic quality was determined using a 4-point scale. Differences were analyzed for significance using a t-test. Interobserver variability was calculated.

RESULTS: In all 20 patients (100%), MR-AP was feasible. Diagnostic quality was, in all cases, between 1 and 2 for both modalities and readers. MR-AP detected significantly more lesions than double-enhanced MRI (102.5 vs 61, respectively, P < 0.0024). The inter-observer variability was 0.881 for MRI and 0.903 for MR-AP.

CONCLUSION: Our study confirmed that the MR-AP as an additional modality for detection of HCC is beneficial, as significantly more lesions were detected compared to MRI with liver-specific contrast.

Comparison between preoperative quantitative assessment of bowel wall vascularization by contrast-enhanced ultrasound and operative macroscopic findings and results of histopathological scoring in Crohn's disease

PURPOSE

Patients with Crohn's disease (CD) often undergo several radiological imaging studies, which - with the exception of MRI and US - subject patients to ionizing radiation. Thus, efforts have been made to identify the inflammation activity using ultrasound techniques. The aim of our study was to describe the perfusion pattern of the inflamed bowel wall in CD using contrast-enhanced ultrasound (CEUS) and specific quantification software for perfusion assessment. Moreover, we compared these findings with the operative macroscopic findings as well as with the transparietal histopathological findings of surgical specimens applying an advanced histopathological scoring system.

MATERIALS AND METHODS

We prospectively performed CEUS in 20 consecutive patients with proven CD and planned bowel surgery due to CD within the next 15 days. We then applied the quantification software Qontrast to obtain contrast-enhanced sonographic perfusion maps. The surgeon defined the clinical behavior of CD according to the Vienna classification. The resected segments were then assessed by a pathologist using an advanced scoring system. We compared the results of CEUS, macroscopic findings and histopathological scoring.

RESULTS

We found a strong negative correlation (r = - 0.677, p < 0.01) between the histopathological score and the time-to-peak (TTP). Moreover, we detected a strong correlation between TTP and single parameters of the histopathological scoring system.

CONCLUSION

Ultrasound as a widely available radiation-free imaging method would be preferable for assessing inflammatory activity of CD, particularly since the ultrasound findings correlate significantly with a histopathological scoring system.

Comparison between a clinical activity index (Harvey-Bradshaw-Index), laboratory inflammation markers and quantitative assessment of bowel wall vascularization by contrast-enhanced ultrasound in Crohn's disease

PURPOSE

Due to its character as a remitting inflammatory disease, patients suffering from Crohn's disease (CD) often undergo several imaging studies subjecting the mostly young patients to ionizing. Contrast enhanced ultrasound for capillary microvascular assessment might be a new diagnostic tool for identifying the activity of inflammation by ultrasound techniques.

MATERIALS AND METHODS

We prospectively evaluated 45 patients with proven Crohn's disease performing contrast enhanced ultrasound (CEUS) and laboratory assessment including C-reactive protein (CRP), leucocytes and hematocrit as well as calculating the Harvey-Bradshaw Index (HBI). Thereafter, we applied the quantification software Qontrast(®) to obtain contrast-enhanced sonographic perfusion maps.

RESULTS

Analysis of the 41 finally included patients revealed a correlation of CRP to HBI and TTP[s], respectively. Moreover, an association was found for HBI and TTP[s] and for HBI and TTP[s]/Peak [%]. Analysis of 34 patients with a Peak [%] ≥ 25 showed a close association of HBI and CRP. Besides, in these patients CRP correlated to TTP[s] and to TTP[s]/Peak [%]. We found a strong negative correlation between HBI and TTP[s] (r = -0.645, p<0.01), thus, the higher the clinical activity the shorter the time-to-peak.

CONCLUSION

Quantitative evaluation with CEUS, particularly the calculation of TTP[s] in patients with a Peak [%] ≥ 25, provides a simple method to assess the inflammatory activity in CD.

Comparison of high-resolution ultrasound and MR-enterography in patients with inflammatory bowel disease

AIM: To compare the results of high-resolution ultrasound (HR-US) and magnetic resonance enterography (MRE) examinations in patients with inflammatory bowel disease (IBD).

METHODS: The reports of 250 consecutive cases with known IBD, who had an MRE and HR-US examination, were retrospectively analyzed. Using a patient-based approach we evaluated morphological disease features such as affected bowel wall, stenosis, abscess and fistula. The comparison between the two modalities was based on the hypothesis, that any pathological change described in any imaging modality was a true finding, as no further standard of reference was available for complete assessment.

RESULTS: Two hundred and fifty examinations representing 207 different patients were evaluated. Both modalities assessed similar bowel wall changes in 65% of the examinations, with more US findings in 11% and more MRE findings in 15%. When the reports were analyzed with regard to “bowel wall inflammation”, US reported more findings in 2%, while MRE reported more findings in 53%. Stenoses were assessed to be identical in 8%, while US found more in 3% and MRE in 29% (P < 0.01). For abscess detection, US showed more findings in 2% (n = 4) while MRE detected more in 6% (n = 16). US detected more fistulas in 1% (n = 2), while MRE detected more in 13% (n = 32) (P < 0.001). The most common reason for no detected pathology by US was a difficult to assess anatomical region (lesser pelvis, n = 72).

CONCLUSION: US can miss clinically relevant pathological changes in patients with IBD mostly due to difficulty in assessing certain anatomical regions.

Detection and characterization of endoleaks following endovascular treatment of abdominal aortic aneurysms using contrast harmonic imaging (CHI) with quantitative perfusion analysis (TIC) compared to CT angiography (CTA)

PURPOSE

To show the feasibility of the detection of endoleaks following endovascular treatment of aortic aneurysms using contrast harmonic imaging (CHI) in comparison to computed tomography angiography (CTA).

MATERIALS AND METHODS

51 patients with suspected endoleaks, who underwent previous endovascular treatment for abdominal aortic aneurysm, were examined using CTA and vascular ultrasound. Biphasic CTA in all cases and digital subtraction angiography (DSA) in 8 patients were evaluated by two radiologists in consensus and served as the standard of reference. Ultrasound was performed by an experienced examiner with a multi-frequency linear transducer (2 - 4 MHz) using CHI following bolus injection of 2.4 ml of SonoVue® IV (maximum 5 ml). All images were evaluated by two observers in consensus regarding the reperfusion of the abdominal aneurysm using time intensity curve (TIC) analysis.

RESULTS

In 30 of 51 patients, endoleaks were detected concordantly in CHI and CTA. In 20 of 51 patients, no endoleak was found in CHI and CTA/DSA. In one patient, a type II endoleak could initially only be detected in CHI and was later confirmed in follow-up examinations by CTA (sens. 99%, spec. 93%, NPV 99 %, PPV 95%). TIC analysis allowed evaluation of the perfusion dynamics of endoleaks in all patients. Significant differences were found (p < 0.05, Mann Whitney U Test) regarding the perfusion within the aneurysm when an endoleak was present (10.39 ± 4.29 dB) or not present (6.42 ± 2.86 dB).

CONCLUSION

CHI with perfusion analysis allows definite detection of endoleaks, especially if contraindications for CTA are present. CHI presents an alternative for follow-up monitoring.