OS08.4.A Retrospective analysis of in vivo 1H-magnetic resonance spectroscopy based on a machine learning approach enables reliable prediction of IDH mutation in patients with glioma

BACKGROUND

Mutation of isocitrate dehydrogenase (IDH) is not only an important landmark in the development of low-grade gliomas, but also has prognostic significance and is a potential therapeutic target. There is a high need to determinate IDH mutation status at diagnosis and during the course of therapy in a non-invasive and reliable manner. We established a machine learning approach based on a support vector machine to detect IDH mutation status in in vivo standard 1H-magnetic resonance spectroscopy (1H-MRS) at 3T with an accuracy of 88.2%, a sensitivity of 95.5% (95% CI, 77.2–99.9%), and a specificity of 75% (95% CI, 42.85–94.5%) in a prospective monocentric clinical trial. Here, the same method is applied in a retrospective cohort at 1.5T and tested for transferability.

MATERIAL AND METHODS

Validation cohort. The validation cohort comprised 100 patients with glioma for which standard in vivo 1H-MRS spectra had been acquired between 2002 and 2007. Standard single voxel spectroscopy had been measured at 1.5T using a PRESS sequence with a TR of 1500ms and a TE of 30ms. One sample had to be excluded due to non-malignant histology and for 15 samples the IDH mutation status was not available. Therefore, the validation cohort comprised 84 samples, of which 35 were bearing an IDH mutation in immunohistochemistry (sequencing for confirmation is outstanding). Machine learning. To transfer our method to an independent validation cohort our previously established machine learning approach was first trained on all samples of the 3T group. The trained algorithm was then applied to the data of the validation cohort. Here, among other factors the different field strengths, with which the spectra were acquired (3T vs. 1.5T) had to be considered.

RESULTS

27 samples of the validation cohort had to be excluded due to poor spectra quality. Our approach correctly detected IDH mutation status in 47 of 62 patients (75.8%), although the technical conditions were significantly different from our published prospective cohort. 17 of 30 patients bearing an IDH mutation were correctly identified, while 30 of 32 wild type patients were determined successfully.

CONCLUSION

Our approach to detect IDH mutation status has promising application in an unselected retrospective cohort, demonstrating transferability across different technical conditions. Further investigations to improve our technique and an advanced neuropathological processing of the samples are planned.

Changes of Right Ventricular Function After Transcatheter Aortic Valve Replacement and Association With Outcomes

BACKGROUND

Baseline right ventricular (RV) dysfunction represents a predictor for poor outcome in patients undergoing transcatheter aortic valve replacement (TAVR). However, RV function may improve after TAVR, which could have important implications on outcomes. The aim of the present study was to assess changes in RV function after TAVR and its prognostic value regarding clinical outcome.

METHODS AND RESULTS

Patients undergoing TAVR at our institution were consecutively enrolled and categorized into 4 groups according to changes in RV function during echocardiographic follow-up at 6 months. A total of 188 patients were included. Of those showing normal function at baseline, 87% (130/149) had preserved RV function at follow-up (group 1), whereas 13% (19/149) developed new RV dysfunction (group 2). Of those with RV dysfunction at baseline (39 patients), RV function normalized in 46% (18/39) (group 3) and remained impaired in 54% (21/39) (group 4). The Kaplan-Meier estimated survival at 3 years was highest in patients in group 1 (83%), intermediate in group 2 (65%) and 3 (69%), whereas group 4 had the worst survival (37%; P < .001). Furthermore, new or persistent RV dysfunction was identified to be independently associated with mortality during follow-up (hazard ratio 2.55; interquartile range 1.03-6.47, P = .004).

CONCLUSIONS

Patients with preserved RV function have a high 3-year survival. Normalization of RV function showed improved survival compared with patients with persistent RV dysfunction, who had a dismal prognosis despite TAVR.

Impact of sinus rhythm versus atrial fibrillation on left ventricular remodeling after transcatheter aortic valve replacement

AIMS

Atrial fibrillation (AF) is associated with increased mortality after transcatheter aortic valve replacement (TAVR). Cerebrovascular complications and bleeding events associated with anticoagulation therapy are discussed to be possible causes for this increased mortality. The present study sought to assess whether AF is associated with impaired left ventricular (LV) reverse remodeling representing another possible mechanism for poor outcome.

METHODS

All patients who underwent TAVR in our institution and had 1-year echocardiography follow-up were included. LV mass index (LVMI) at baseline and follow-up as well as LVMI change at 1 year were assessed with respect to the presence of AF (either at baseline or during hospitalization after TAVR) and sinus rhythm (SR).

RESULTS

A total of 213 patients (n = 95 in AF; n = 118 in SR) were enrolled in the present study. Patients with AF had higher LVMI at 1 year compared to those with SR (173 ± 61 g/m² vs. 154 ± 55 g/m²; p = 0.02) and they showed lower relative LVMI change at 1 year (- 2 ± 28% vs. - 9 ± 29%; p = 0.04). In linear regression analysis, AF was independently associated with relative LVMI change (regression coefficient ß 0.076 [95% CI 0.001-0.150]; p = 0.04). With respect to clinical outcome depending on AF and LVMI regression, the Kaplan-Meier estimated event-free of death or cardiac rehospitalization at 3 years was lowest among patients with AF and no LVMI regression.

CONCLUSIONS

The present study identified a significant association of AF with changes in LVMI after TAVR, which was also shown to be associated with clinical outcome.

Dose-Dependent Effect of Renin-Angiotensin System Blockade Following Transcatheter Aortic Valve Replacement

BACKGROUND

There is growing body of evidence from retrospective studies that renin-angiotensin system (RAS) blockade is associated with improved outcome after transcatheter aortic valve replacement (TAVR). However, it remains unknown whether the effect of RAS blockade is dose dependent. The current study sought to assess the dose-dependent effect of RAS blockade on survival and left-ventricular (LV) remodelling after TAVR.

METHODS

Patients who were enrolled into our observational TAVR study at our institution were retrospectively assessed according to different doses of RAS blockade: group 1 (no RAS blockade), group 2 (25% of maximum daily dose), group 3 (50% of maximum daily dose), and group 4 (full daily dose).

RESULTS

A total of 323 patients between January 2015 and September 2019 were included. Patients with higher doses of RAS blockade showed a trend toward higher overall survival at 3-year follow-up (56% with no RAS blockade vs 66% with the 25% dose vs 79% with the 50% dose vs 78% with the full dose; P = 0.063). After adjustment for baseline characteristics, the difference in survival was significant (P = 0.042). Besides New York Heart Association class and left-ventricular ejection fraction (LVEF), RAS blockade dose was identified as independent predictor for all-cause mortality (hazard ratio [HR] 0.72; 95% confidence interval [CI], 0.54-0.97; P = 0.03). With respect to LV remodelling, a significantly larger reduction of LV mass index was observed during the follow-up with higher doses of RAS blockade.

CONCLUSIONS

The current study showed that the impact of RAS blockade treatment on clinical outcome and LV remodelling after TAVR is dose dependent.

P5574Prognostic impact of left atrial function following transcatheter mitral valve repair

Background

Left atrial (LA) function predicts clinical outcome in a variety of cardiovascular diseases. However, limited data is available in the setting of mitral regurgitation (MR).

Purpose

The aim of the present study was to assess potential changes in LA ejection fraction (LA-EF) and its prognostic value in patients following transcatheter mitral valve repair using the mitraclip.

Methods

A total of 88 consecutive patients undergoing mitraclip implantation with complete echocardiography at baseline and follow-up between 3 and 6 months post-procedure were enrolled.

Results

LA-EF improved in 58% of the population. Change in LA-EF was associated with residual MR, residual transmitral gradient and left ventricular ejection fraction (LV-EF) changes. Compared to their counterparts, patients with residual MR ≥ grade 2 (−6% [−9 to 1%] vs. 4% [−5 to 15%]; p=0.05) and with residual transmitral gradient ≥5 mmHg (−2% [−9 to 9%] vs. 5% [−4 to 16%]; p=0.03) showed a decline in LA-EF, respectively. Furthermore, LA-EF significantly correlated with changes in LV-EF (r=0.40; p=0.001). With regards to clinical outcome, heart failure symptoms as assessed by NYHA class were more severe in patients with worsened LA-EF at follow-up. Finally, LA-EF change was identified as independent predictor of all-cause mortality (HR 0.94 [0.90–0.98]; p=0.008).

Kaplan-Meier estimates for survival

Conclusion

The present analysis showed changes in LA function in patients undergoing mitraclip implantation to be associated with important measures including residual MR, elevated transmitral gradient and LV function. Importantly, LA function alterations represent a strong predictor for all-cause mortality.

Influence of hepatic fibrosis and inflammation: Correlation between histopathological changes and Gd-EOB-DTPA-enhanced MR imaging

Objective

To evaluate the influence of an active inflammatory process in the liver on Gd-EOB-DTPA-enhanced MR imaging in patients with different degrees of fibrosis/cirrhosis.

Material and methods

Overall, a number of 91 patients (61 men and 30 women; mean age 58 years) were included in this retrospective study. The inclusion criteria for this study were Gd-EOB-DTPA-enhanced MRI of the liver and histopathological evaluation of fibrotic and inflammatory changes. T1-weighted VIBE sequences of the liver with fat suppression were evaluated to determine the relative signal change (RE) between native and hepatobiliary phase (20min). In simple and multiple linear regression analyses, the influence of liver fibrosis/cirrhosis (Ishak score) and the histopathological degree of hepatitis (Modified Hepatic Activity Index, mHAI) on RE were evaluated.

Results

RE decreased significantly with increasing liver fibrosis/cirrhosis (p < 0.001) and inflammation (mHAI, p = 0.004). In particular, a correlation between RE and periportal or periseptal boundary zone hepatitis (moth feeding necrosis, mHAI A, p = 0.001) and portal inflammation (mHAI D, p < 0.001) was observed. In multiple linear regression analysis, both the degree of inflammation and the degree of fibrosis were significant predictors for RE (p < 0.01).

Conclusion

The results of this study suggest that the MR-based hepatic enhancement index RE is not only influenced by the degree of fibrosis, but also by the degree of inflammation.

Prognostic Impact of Left Atrial Function Following Transcatheter Mitral Valve Repair

Background

Left atrial (LA) function predicts clinical outcome in a variety of cardiovascular diseases. However, limited data are available in the setting of mitral regurgitation. The aim of the present study was to assess potential changes in LA ejection fraction (LAEF) and its prognostic value in patients following transcatheter mitral valve repair using the MitraClip.

Methods and Results

A total of 88 consecutive patients undergoing MitraClip implantation with complete echocardiography at baseline and follow‐up between 3 and 6 months postprocedure were enrolled. LAEF improved in 58% of the population. Change in LAEF was associated with residual mitral regurgitation, residual transmitral gradient and left ventricular ejection fraction changes. Compared with their counterparts, patients with residual mitral regurgitation ≥grade 2 (change in LAEF, −6% [Interquartile [IQR], −9–1%] versus 4% [IQR, −5–15%]; P=0.05) and with residual transmitral gradient ≥5 mm Hg (change in LAEF, −2% [IQR, −9–9%] versus 5% [IQR, −4–16%]; P=0.03) showed a decline in LAEF, respectively. Furthermore, LAEF significantly correlated with changes in left ventricular ejection fraction (r=0.40; P=0.001). With regards to clinical outcome, heart failure symptoms as assessed by New York Heart Association class were more severe in patients with worsened LAEF at follow‐up. Finally, LAEF change was identified as an independent predictor of all‐cause mortality (hazard ratio, 0.94; 95% CI, 0.90–0.98 [P=0.008]).

Conclusions

The present analysis showed that changes in LA function in patients undergoing MitraClip implantation are associated with important measures including residual mitral regurgitation, elevated transmitral gradient, and left ventricular function. Importantly, LA function alterations represent a strong predictor for all‐cause mortality.

Reverse Cardiac Remodeling After Transcatheter Treatment of Severe Tricuspid Regurgitation Using the Edge-to-Edge MitraClip Technique

OBJECTIVES

In recent years, transcatheter treatment techniques for tricuspid regurgitation (TR) have rapidly evolved. Cardiac remodeling analysis beyond clinical outcome assessment following transcatheter tricuspid repair is still lacking. The aim of the present case series was to analyze cardiac remodeling after tricuspid valve repair using the edge-to-edge MitraClip technique.

METHODS

Echocardiographic analysis was performed prior to MitraClip implantation and at 3-month and 6-month follow-up exams.

RESULTS

Six consecutive patients undergoing MitraClip implantation between April 2017 and March 2018 at our institution were enrolled. During follow-up, TR reduction was durable in all patients, without recurrence of severe TR. Compared to baseline, right ventricular function improved in 5 out of 6 patients. Reduction in right ventricular area was observed in the majority of patients and reduction in right atrial volume was observed in all subjects. Patients also experienced beneficial left cardiac remodeling.

CONCLUSION

The present series indicates that transcatheter treatment of severe TR using the edge-to-edge MitraClip technique can lead to reverse cardiac remodeling, which is not commonly seen in surgically treated patients.

BLADE Sequences in Transverse T2-weighted MR Imaging of the Cervical Spine. Cut-off for Artefacts?

PURPOSE

The BLADE (PROPELLER) technique reduces artefacts in imaging of the cervical spine in sagittal orientation, but till now failed to do so in axial orientation, because here it increased through plane CSF-flow artefacts, which spoiled the benefit of BLADE artefact reduction "in plane". The aim of this study was to compare a BLADE sequence with optimised measurement parameters in axial orientation to T2-TSE.

MATERIALS AND METHODS

Both sequences were compared in 58 patients with 31 discal, 16 bony and 11 spinal cord lesions. Image sharpness, reliability of spinal cord depiction, CSF flow artefacts and lesion detection were evaluated by 3 independent observers. Additionally the observers were asked which sequence they would prefer for diagnostic workup. Statistical evaluations were performed using sign and χ2 test.

RESULTS

BLADE was significantly superior concerning image sharpness, spinal cord depiction and overall lesion detection. BLADE was rated better for most pathologies, for bony lesions the differences compared with TSE were statistically significant. Regarding CSF-flow artefacts both sequences showed no difference. All readers preferred BLADE in side by side reading.

CONCLUSION

An optimised axial T2 BLADE sequence decreases the problems of increased through plane CSF-flow artefacts in this orientation. By reducing various other artefacts it yields better image quality and has the potential to reduce the number of non-diagnostic examinations especially in uncooperative patients.

KEY POINTS

T2 BLADE/PROPELLER sequences proofed to reduce artefacts in sagittal spine imaging. BLADE/PROPELLER improve image quality, but can aggravate CSF flow artefacts in axial orientation. Optimised parameter setting for axial T2 BLADE reduces "through-plane" CSF artefacts aggravation. Optimised axial T2 BLADE reduces non-diagnostic examinations especially in uncooperative patients.

Multivariable analysis of clinical influence factors on liver enhancement of Gd-EOB-DTPA-enhanced 3T MRI

PURPOSE

The purpose of this study was to identify clinical factors influencing Gd-EOB-DTPA liver uptake in patients with healthy liver parenchyma.

MATERIALS AND METHODS

A total of 124 patients underwent contrast-enhanced MRI with a hepatocyte-specific contrast agent at 3 T. T1-weighted volume interpolated breath-hold examination (VIBE) sequences with fat suppression were acquired before and 20 minutes after contrast injection. The relative enhancement (RE) between plain and contrast-enhanced signal intensity was calculated. Simple and multiple linear regression analyses were performed to evaluate clinical factors influencing the relative enhancement. Patients were subdivided into three groups according to their relative liver enhancement (HRE, RE ≥ 100 %; MRE, 100 % > RE > 50 %; NRE, RE ≤ 50 %) and were analyzed according to the relevant risk factors.

RESULTS

Simple regression analyses revealed patient age, transaminases (AST, ALT, GGT), liver, spleen and delta-liver volume (the difference between the volumetrically measured liver volume and the estimated liver volume based on body weight) as significant factors influencing relative enhancement. In the multiple analysis the transaminase AST, spleen and delta liver volume remained significant factors influencing relative enhancement. Delta liver volume showed a significant difference between all analyzed groups.

CONCLUSION

Liver enhancement in the hepatobiliary phase depends on a variety of factors. Body weight-adapted administration of Gd-EOB-DTPA may lead to inadequate liver enhancement after 20 minutes especially when the actual liver volume differs from the expected volume.

KEY POINTS

• Differences between actual and expected liver volume can cause inadequate liver enhancement after 20 min. • A liver volume-adapted dose of Gd-EOB-DTPA may help to improve liver enhancement.

[Detection of intrinsic ligament and TFCC lesions of the wrist. Direct versus indirect MRI arthrography]

BACKGROUND

The purpose of this study was to validate the diagnostic value of direct magnetic resonance imaging (dMRI) arthrography and indirect MRI (iMRI) arthrography concerning intrinsic ligament injuries and tears of the triangular fibrocartilage complex (TFCC).

PATIENTS AND METHODS

A randomized prospective trial was conducted with patients who presented with wrist pain potentially due to carpal lesions and 10 patients aged 19-60 years (3 female and 7 male) were included. Between the clinical examination and the diagnostic and therapeutic arthroscopy, dMRI and iMRI arthrography were performed for the diagnostics of injuries of the intrinsic ligaments or the TFCC. The results of dMRI and iMRI arthrography were evaluated by two radiologists blinded to the injuries of the patients and a consensus was reached. The results were compared with the findings obtained by arthroscopy.

RESULTS

In the arthroscopy five lesions of the scapholunate ligament (SL), one of the lunotriquetral ligament (LT) and seven of the TFCC were identified. The sensitivity of iMRI and dMRI for carpal ligament lesions (SL and LT) was low (50 %) whereas the specificity was high (93 %). For injuries of the TFCC the sensitivity (up to 100 %) and the specificity (100 %) were both excellent. The area under the curve (AUC) in the receiver operating characteristics (ROC) analysis was high for TFCC lesions in both dMRI and iMRI arthrography.

CONCLUSION

Indirect MRI arthrography is a suitable method for detection of injuries of the TFCC and intrinsic ligaments of the wrist with good sensitivity and specificity. Despite the low number of patients the results of this study showed that there were no essential differences between dMRI and iMRI arthrography with respect to the diagnostic value for carpal injuries of the wrist.

Assessing liver function by liver enhancement during the hepatobiliary phase with Gd-EOB-DTPA-enhanced MRI at 3 Tesla

OBJECTIVES

The purpose of this study was to evaluate the usefulness of Gd-EOB-DTPA-enhanced 3-T MRI to determine the hepatic functional reserve expressed by the model for end-stage liver disease (MELD) score.

METHODS

A total of 121 patients with normal liver function (NLF; MELD score ≤ 10) and 29 patients with impaired liver function (ILF; MELD score > 10) underwent contrast-enhanced MRI with a hepatocyte-specific contrast agent at 3T. T1-weighted volume interpolated breath-hold examination (VIBE) sequences with fat suppression were acquired before and 20 min after contrast injection. Relative enhancement (RE) between plain signal intensity and contrast-enhanced signal intensity was calculated and was used to determine Gd-EOB-DTPA uptake into the liver parenchyma for patients with different MELD scores.

RESULTS

RE differed significantly (p ≤ 0.001) between patients with NLF (87.2 ± 29.5 %) and patients with ILF (45.4 ± 26.5 %). The optimal cut-off value for RE to differentiate NLF from ILF was 47.7 % (AUC 0.87). This cut-off value showed a sensitivity of 82.8 % and a specificity of 92.7 % for the differentiation of the analysed groups.

CONCLUSION

Gd-EOB-DTPA uptake in hepatocytes is strongly affected by liver function. Gd-EOB-DTPA-enhanced MRI and assessment of RE during the hepatobiliary phase (HBP) may serve as a useful image-based test in liver imaging for determining regional and global liver function.

KEY POINTS

Hepatic uptake of Gd-EOB-DTPA is strongly affected by liver function. Relative enhancement during HBP in GD-EOB-DTPA MRI correlates with the MELD score. Assessment of relative enhancement may help improve treatment in routine clinical practice.

BLADE sequences in sagittal T2-weighted MR imaging of the cervical spine and spinal cord--lesion detection and clinical value

PURPOSE

Using the BLADE (PROPELLER) technique for T2-weighted MR imaging of the cervical spine has proven to be a reliable tool for reducing artifacts typically for this region. The aim of this study was to evaluate whether the application of BLADE sequences has an impact on the detection of small or low contrast spinal cord and epidural lesions.

MATERIALS AND METHODS

A standard TSE and a BLADE sequence were compared in 33 patients with 46 spinal cord and epidural lesions for T2-weighted sagittal imaging of the cervical spine. Image sharpness, visualization of the dura, reliability of spinal cord depiction as well as lesion contrast were evaluated by two independent readers. Additionally two experienced neuroradiologists selected in consensus the sequence they would prefer for diagnostic purposes. Statistical evaluations were performed using the sign and the χ2 test.

RESULTS

BLADE was significantly superior to TSE regarding image sharpness, visualization of the dura and reliability of spinal cord depiction. Regarding lesion contrast there was a positive trend towards the BLADE sequence. In 17 of 46 lesions, BLADE was judged superior to TSE, while TSE was favored in 10 lesions. In consensus reading both neuroradiologists preferred BLADE for overall image quality in 27 of 33 patients and for lesion contrast in 10 and TSE in 14 of the 33 patients, but 3 TSE sequences were rated as non-diagnostic regarding this criterion.

CONCLUSION

For the detection of even small and low-contrast spinal cord lesions, BLADE is at least equivalent to TSE, yielding better overall image quality and fewer non-diagnostic images.

Impact of liver cirrhosis on liver enhancement at Gd-EOB-DTPA enhanced MRI at 3 Tesla

PURPOSE

The purpose of this study was to assess differences in enhancement effects of liver parenchyma between normal and cirrhotic livers on dynamic, Gd-EOB-DTPA enhanced MRI at 3T.

MATERIALS AND METHODS

93 patients with normal (n=54) and cirrhotic liver (n=39; Child-Pugh class A, n=18; B, n=16; C, n=5) underwent contrast-enhanced MRI with liver specific contrast media at 3T. T1-weighted volume interpolated breath hold examination (VIBE) sequences with fat suppression were acquired before contrast injection, in the arterial phase (AP), in the late arterial phase (LAP), in the portal venous phase (PVP), and in the hepatobiliary phase (HBP) after 20 min. The relative enhancement (RE) of the signal intensity of the liver parenchyma was calculated for all phases.

RESULTS

Mean RE was significantly different among all evaluated groups in the hepatobiliary phase and with increasing severity of liver cirrhosis, a decreasing, but still significant reduction of RE could be shown. Phase depending changes of RE for each group were observed. In case of non-cirrhotic liver or Child-Pugh Score A cirrhosis mean RE showed a significant increase between AP, LAP, PVP and HBP. For Child-Pugh B+C cirrhosis RE increased until PVP, however, there was no change in case of B cirrhosis (p=0.501) and significantly reduced in case of C cirrhosis (p=0.043) during HBP.

CONCLUSION

RE of liver parenchyma is negatively affected by increased severity of liver cirrhosis, therefore diagnostic value of HBP could be limited in case of Child Pugh B+C cirrhosis.

Acute-onset migrainous aura mimicking acute stroke: MR perfusion imaging features

BACKGROUND AND PURPOSE

In a very limited number of cases, acute migrainous aura may mimic acute brain infarction. The aim of this study was to recognize patterns of MR perfusion abnormalities in this presentation.

MATERIALS AND METHODS

One thousand eight hundred fifty MR imaging studies performed for the suspicion of acute brain infarction were analyzed retrospectively to detect patients with acute migrainous aura not from stroke. All patients were examined clinically by 2 neurologists and underwent a standard stroke MR imaging protocol, including PWI. Two radiologists reviewed the perfusion maps visually and quantitatively for the presence, distribution, and grade of perfusion abnormalities.

RESULTS

Among 1850 MR imaging studies, 20 (1.08%) patients were found to have acute migrainous aura. Hypoperfusion was found in 14/20 patients (70%) with delayed rMTT and TTP, decreased rCBF, and minimal decrease in rCBV. In contrast to the typical pattern in stroke, perfusion abnormalities were not limited to a single vascular territory but extended to >1. Bilateral hypoperfusion was seen in 3/14 cases. In 11/14 cases, hypoperfusion with a posterior predominance was found. TTP and rMTT were the best maps to depict perfusion changes at visual assessment, but also rCBF maps demonstrated significant hypoperfusion in quantitative analysis. In all patients, clinical and imaging follow-up findings were negative for stroke.

CONCLUSIONS

Acute migrainous aura is rare but important in the differential diagnosis among patients with the suspicion of acute brain infarction. Atypical stroke perfusion abnormalities can be seen in these patients.

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.

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.

Transmural penetration of intravenously applied microbubbles during contrast-enhanced ultrasound as a new diagnostic feature in patients with GVHD of the bowel

GVHD is a common complication in patients after allo-SCT. Early detection is important because early therapy may improve the outcome. We evaluated contrast-enhanced ultrasound (CEUS) in patients with GVHD to assess typical imaging features. CEUS was performed in nine patients with histologically proven GVHD. As a control four healthy volunteers and six patients with Crohn's disease (CD) were examined. We employed a high-resolution multi-frequency transducer (6-9 MHz) with contrast harmonic imaging. After the injection of 2.4 mL SonoVue (Bracco, Milan, Italy) intravenously data were acquired and stored digitally. Regions of interest were manually placed over the surrounding mesenteric fat, bowel wall and bowel lumen. Maximum signal increase of each compartment was calculated. Patients with CD and GVHD showed significant contrast uptake in the bowel wall. In contrast to CD patients and healthy volunteers, patients with GVHD showed transmural penetration of microbubbles into the bowel lumen. We assume that the damaged gut mucosal barrier in GVHD enables the microbubbles to penetrate through the bowel wall into the bowel lumen. The penetration of microbubbles into the bowel lumen may serve as a novel diagnostic feature for GVHD if confirmed in controlled clinical trials.