Role of contrast-enhanced ultrasound (CEUS) in evaluation of thermal ablation zone

Use superb microvascular imaging to diagnose and predict metastatic cervical lymph nodes in patients with papillary thyroid carcinoma

PURPOSE

Papillary thyroid carcinoma (PTC) with metastatic lymph nodes (LNs) is closely associated with disease recurrence. This study accessed the value of superb microvascular imaging (SMI) in the diagnosis and prediction of metastatic cervical LNs in patients with PTC.

METHODS

A total of 183 cervical LNs (103 metastatic and 80 reactive) from 116 patients with PTC were analysed. Metastatic cervical LNs were confirmed by pathology or/and cytology; reactive cervical LNs were confirmed by pathology or clinical features. The characteristic of conventional ultrasound (US) was extracted using univariate and multivariate analyses. The diagnostic performance of US and SMI were compared using the area under the receiver operating curve (AUC) with corresponding sensitivity and specificity. A nomogram was developed to predict metastatic LNs in patients with PTC, based on multivariate analyses.

RESULTS

L/S < 2, ill-defined border, absence of hilum, isoechoic or hyperechoic, heterogeneous internal echo, peripheral or mixed vascular pattern on color Doppler flow imaging (CDFI) and SMI, and a larger SMI vascular index appeared more frequently in metastatic LNs in the training datasets than in reactive LNs (P < 0.05). The diagnostic sensitivity, specificity and accuracy of SMI vs US are 94.4% and 87.3%, 79.3% and 69.3%, and 87.6% and 79.1%, respectively; SMI combined with US exhibited a higher AUC [0.926 (0.877-0.975)] than US only [0.829 (0.759-0.900)]. L/S < 2, peripheral or mixed vascular type on CDFI, and peripheral or mixed vascular types on SMI were independent predictors of metastatic LNs with PTC. The nomogram based on these three parameters exhibited excellent discrimination, with an AUC of 0.926.

CONCLUSION

SMI was superior to US in diagnosing metastatic LNs in PTC. US combined with SMI significantly improved the diagnostic accuracy of metastatic cervical LNs with PTC. SMI is efficacious for differentiating and predicting metastatic cervical LNs.

Deep learning model based on contrast-enhanced ultrasound for predicting early recurrence after thermal ablation of colorectal cancer liver metastasis

OBJECTIVES

To develop and validate a deep learning (DL) model based on quantitative analysis of contrast-enhanced ultrasound (CEUS) images that predicts early recurrence (ER) after thermal ablation (TA) of colorectal cancer liver metastasis (CRLM).

METHODS

Between January 2010 and May 2019, a total of 207 consecutive patients with CRLM with 13,248 slice images at three dynamic phases who received CEUS within 2 weeks before TA were retrospectively enrolled in two centres (153 for the training cohort (TC), 32 for the internal test cohort (ITC), and 22 for the external test cohort (ETC)). Clinical and CEUS data were used to develop and validate the clinical model, DL model, and DL combining with clinical (DL-C) model to predict ER after TA. The performance of these models was compared by the receiver operating characteristic curve (ROC) with the DeLong test.

RESULTS

After a median follow-up of 56 months, 49% (99/207) of patients experienced ER. Three key clinical features (preoperative chemotherapy (PC), lymph node metastasis of the primary colorectal cancer (LMPCC), and T stage) were used to develop the clinical model. The DL model yielded better performance than the clinical model in the ETC (AUC: 0.67 for the clinical model, 0.76 for the DL model). The DL-C model significantly outperformed the clinical model and DL model (AUC: 0.78 for the DL-C model in the ETC; both, p < 0.001).

CONCLUSIONS

The model based on CEUS can achieve satisfactory prediction and assist physicians during the therapeutic decision-making process in clinical practice.

KEY POINTS

• This is an exploratory study in which ablation-related contrast-enhanced ultrasound (CEUS) data from consecutive patients with colorectal cancer liver metastasis (CRLM) were collected simultaneously at multiple institutions. • The deep learning combining with clinical (DL-C) model provided desirable performance for the prediction of early recurrence (ER) after thermal ablation (TA). • The DL-C model based on CEUS provides guidance for TA indication selection and making therapeutic decisions.

Contrast-enhanced ultrasound for abdominal image-guided procedures

INTRODUCTION

Since FDA approval for contrast-enhanced ultrasound (CEUS), clinical applications have increased to include diagnostic imaging of hepatic, renal, and other abdominal lesions. The modality has also demonstrated utility in certain image-guided procedures. Intravascular ultrasound contrast agents use microbubbles to improve visibility of solid tumors. Lesions not well seen on grayscale or Doppler ultrasound may become amenable to CEUS-guided biopsy or ablation.

MATERIALS AND METHODS

This pictorial essay provides eleven examples to illustrate the current use of CEUS in a variety of abdominal image-guided procedures. Hepatic, renal, peritoneal, and soft tissue cases are presented.

CONCLUSION

CEUS can improve visualization and targeting in abdominal image-guided procedures, without nephrotoxicity or radiation exposure.

An alternative second performance of contrast-enhanced ultrasound for large focal liver lesion is necessary for sufficient characterization

Focal liver lesions (FFLs) evaluated using contrast-enhanced ultrasound (CEUS) and contrast-enhanced computed tomography (CECT) may have the same or similar findings or substantial discrepant findings. Such phenomenon can be found in two performances of CEUS that the second performance of CEUS conducted shortly following the initial performance of CEUS. Discrepancy of two performances of CEUS for FFLs occurring in the same patient at a short internal has not been well addressed, which raises challenge for CEUS for the evaluation of FFLs. In this case study, such phenomenon is illustrated and implication is obtained.

Microvascular Flow Imaging: A State-of-the-Art Review of Clinical Use and Promise

Vascular imaging with color and power Doppler is a useful tool in the assessment of various disease processes. Assessment of blood flow, from infarction and ischemia to hyperemia, in organs, neoplasms, and vessels, is used in nearly every US investigation. Recent developments in this area are sensitive to small-vessel low velocity flow without use of intravenous contrast agents, known as microvascular flow imaging (MVFI). MVFI is more sensitive in detection of small vessels than color, power, and spectral Doppler, reducing the need for follow-up contrast-enhanced US (CEUS), CT, and MRI, except when arterial and venous wash-in and washout characteristics would be helpful in diagnosis. Varying clinical applications of MVFI are reviewed in adult and pediatric populations, including its technical underpinnings. MVFI shows promise in assessment of several conditions including benign and malignant lesions in the liver and kidney, acute pathologic abnormalities in the gallbladder and testes, and superficial lymph nodes. Future potential of MVFI in different conditions (eg, endovascular repair) is discussed. Finally, clinical cases in which MVFI correlated and potentially obviated additional CEUS, CT, or MRI are shown.

Loco-regional treatment of hepatocellular carcinoma: Role of contrast-enhanced ultrasonography

Hepatocellular carcinoma (HCC) is one of the few cancers for which locoregional treatments (LRTs) are included in international guidelines and are considered as a valid alternative to conventional surgery. According to Barcelona Clinic Liver Cancer classification, percutaneous treatments such as percutaneous ethanol injection, radiofrequency ablation and microwave ablation are the therapy of choice among curative treatments in patients categorized as very early and early stage, while transcatheter arterial chemoembolization is considered the better option for intermediate stage HCC. A precise assessment of treatment efficacy and surveillance is essential to optimize survival rate, whereas residual tumor requires additional treatment. Imaging modalities play a key role in this task. Currently, contrast-enhanced computed tomography/magnetic resonance imaging are considered the standard imaging modalities for this purpose. Contrast enhanced ultrasound (CEUS), using second generation contrast agents, plays an increasingly important role in detecting residual disease after LRTs. CEUS is a straightforward to perform, repeatable and cost-effective imaging modality for patients with renal failure or iodine allergies. Due to the ability to focus on single regions, CEUS can also provide high temporal resolution. Moreover, several studies have reported the same or better diagnostic accuracy as contrast-enhanced computed tomography for assessing tumor vascularity 1 mo after LRTs, and recently three-dimensional (3D)-CEUS has been reported as a promising technique to improve the evaluation of tumor response to therapy. Furthermore, CEUS could be used early after procedures in monitoring HCC treatments, but nowadays this indication is still debated, and data from literature are conflicting, especially after transcatheter arterial chemoembolization procedure.

Endoscopic Ultrasound-Guided Laser Ablation Using a Diffusing Applicator for Locally Advanced Pancreatic Cancer Treatment

Simple Summary

Pancreatic cancer (PC) is one of the most lethal cancers; caused by family history, obesity, diabetes, and smoking, it has a 2–9% five-year survival rate. However, patients diagnosed by endoscopic ultrasound (EUS) already have an advanced stage of PC, indicating the difficulty of surgical resection. Recently, laser ablative treatment with a diffusing applicator has been proven to be feasible for treating advanced PC. Despite the potential application for treating PC, further evaluation of acute and chronic tissue responses are essential to determine the efficacy and safety of diffusing applicator under EUS guidance. In this study, EUS-guided diffusing applicator-assisted laser ablation was evaluated to quantify the extent of the tissue response after the delivery of various energy levels.

Abstract

Endoscopic ultrasound (EUS)-guided cylindrical interstitial laser ablation (CILA) procedures can be used to treat unresectable pancreatic cancer (PC). The aim of this study was to investigate the acute responses of pancreatic tissue after EUS-guided CILA in vivo in porcine models. Eight pigs were tested to compare the effects of different energy levels on pancreatic tissue ablation. A 1064 nm laser system was used to deliver 5 W through a diffusing applicator. The EUS-guided CILA was performed under four different energies: 200, 400, 600, and 800 J. Three days after the experiments, histological analysis was performed. The CILA consistently generated circular coagulated necrosis (CN) in the cross-sectioned pancreatic tissue. The ablation diameter was linearly dependent on the total energy delivery. The area of the CN initially increased with total energy delivery but became saturated at 600 J. The width of the degenerative parenchyma (DP) in the native tissue beyond the CN region increased with the total energy up to 600 J, and then decreased afterward. EUS-guided CILA can be a feasible approach for treating PC. Further animal studies will investigate the chronic responses of the pancreatic tissue to examine the efficacy and safety of the proposed method for clinical translation.

Contrast enhancement for ultrasound-guided interventions: when to use it and what to expect?

The use of contrast-enhanced ultrasonography (CEUS) has recently become synonymous with high-standard ultrasonography (US). From expanding the reach of US diagnostics to improving the precision of various invasive procedures, CEUS is rapidly becoming a standard in numerous niches. However, proficiency in CEUS comes with a cost, both from a learning curve and material standpoint, and as every growing field, lacks firm evidence and standardization. Therefore, in the current paper, we aim to provide an evidence-based review of available methods and to discuss the advantages and pitfalls of CEUS in interventional procedures, trying to provide strong evidence whenever available, or at least an educated expert opinion if data are lacking.

Real-time arteriography-directed percutaneous microwave ablation for small or poorly characterized hepatic lesions using hybrid Angio-CT

PURPOSE

To report the utility of real-time arteriography-directed percutaneous MWA (rad-pMWA) in a hybrid angiography-computed tomography (Angio-CT) suite to treat small or inconspicuous hepatic tumors on non-contrast CT.

METHOD

This single-center retrospective cohort included 15 consecutive patients who underwent rad-pMWA (6 HCC, 4 mCRC, 4 NET, and 1 cholangiocarcinoma). The median longest axial diameter of treated tumors was 1.7 (range: 1.4-6.0) cm. Technical success, contrast use, procedure-related complication, and initial treatment response were recorded.

RESULTS

Technical success was achieved in 15/15 (100%) as shown by no residual enhancement on catheter-directed CT-angiography at the conclusion of the procedure. Average contrast volume use was 63.1 (SD: 29.1) ml. No major arterial access-related complication or residual tumor was noted. Complete ablation rate was 14/14 (100%) at initial 6-8-week follow-up. Local disease progression occurred in one patient during follow-up.

CONCLUSION

Rad-pMWA using Angio-CT is safe and effective for improving tumor visibility and operator convenience. Tumors can be localized with low contrast dosage and ablated with high efficacy with immediate real-time evaluation of the ablation cavity.

A Review of Clinical Applications for Super-resolution Ultrasound Localization Microscopy

Microvascular structure and hemodynamics are important indicators for the diagnosis and assessment of many diseases and pathologies. The structural and functional imaging of tissue microvasculature in vivo is a clinically significant objective for the development of many imaging modalities. Contrast-enhanced ultrasound (CEUS) is a popular clinical tool for characterizing tissue microvasculature, due to the moderate cost, wide accessibility, and absence of ionizing radiation of ultrasound. However, in practice, it remains challenging to demonstrate microvasculature using CEUS, due to the resolution limit of conventional ultrasound imaging. In addition, the quantification of tissue perfusion by CEUS remains hindered by high operator-dependency and poor reproducibility. Inspired by super-resolution optical microscopy, super-resolution ultrasound localization microscopy (ULM) was recently developed. ULM uses the same ultrasound contrast agent (i.e. microbubbles) in CEUS. However, different from CEUS, ULM uses the location of the microbubbles to construct images, instead of using the backscattering intensity of microbubbles. Hence, ULM overcomes the classic compromise between imaging resolution and penetration, allowing for the visualization of capillary-scale microvasculature deep within tissues. To date, many in vivo ULM results have been reported, including both animal (kidney, brain, spinal cord, xenografted tumor, and ear) and human studies (prostate, tibialis anterior muscle, and breast cancer tumors). Furthermore, a variety of useful biomarkers have been derived from using ULM for different preclinical and clinical applications. Due to the high spatial resolution and accurate blood flow speed estimation (approximately 1 mm/s to several cm/s), ULM presents as an enticing alternative to CEUS for characterizing tissue microvasculature in vivo. This review summarizes the principles and present applications of CEUS and ULM, and discusses areas where ULM can potentially provide a better alternative to CEUS in clinical practice and areas where ULM may not be a better alternative. The objective of the study is to provide clinicians with an up-to-date review of ULM technology, and a practical guide for implementing ULM in clinical research and practice.

Role of Sonazoid-based contrast-enhanced ultrasonography in the microwave ablation of primary hyperparathyroidism

OBJECTIVES

This study aimed to determine the performance of Sonazoid-based contrast-enhanced ultrasound (CEUS) in the microwave ablation (MWA) of primary hyperparathyroidism (pHPT).

METHODS

Forty patients with pHPT were enrolled and treated with percutaneous ultrasound (US)-guided MWA assisted by CEUS. All patients underwent immediate CEUS examinations following MWA. On post-ablation day 1, patients who did not display a decrease in intact parathyroid hormone (iPTH) levels to the norm were examined by CEUS to evaluate an incomplete ablation. We compared the serum iPTH and calcium levels and the nodule volumes before and after MWA. The complications were evaluated during and after treatment.

RESULTS

Immediately following MWA, CEUS demonstrated complete ablation with all 44 parathyroid nodules. On post-ablation day 1, five nodules in five patients displayed annular enhancement around the ablation zone on CEUS. The average maximum diameters of the nodules and the ablation zone were 1.09 ± 0.28 cm and 1.36 ± 0.23 cm, respectively. An ablation zone larger than the primary lesion (p < 0.05) generated a higher rate of complete ablation. Compared with pre-MWA, serum iPTH and calcium levels were significantly improved. Treatment success was achieved in 38 patients (95%). Hoarseness was a major complication in six patients (15%); however, it improved spontaneously within 1-4 months. We observed two recurrences (2/40, 5%) at 9 months and 11 months following MWA, respectively.

CONCLUSION

US-guided percutaneous MWA assisted by CEUS for pHPT is an effective and safe therapy. CEUS can avoid operative failure and improve the cure rate.

Imaging appearance of residual HCC following incomplete trans-arterial chemoembolization on contrast-enhanced imaging

PURPOSE

The aim of this study was to describe changes in contrast agent kinetics in HCC following incomplete trans-arterial chemoembolization (TACE) on contrast-enhanced ultrasound (CEUS) and MRI/CT.

METHODS

Patients with residual HCC proven by biopsy, retreatment angiography, or 4-8 month MRI demonstrating tumor progression were identified. Pre-treatment and 4-6-week follow-up CE-MRI/CT and CEUS exams were collected for blinded reads by two experienced readers for each modality to evaluate arterial phase hyper-enhancement (APHE) and washout within the residual HCC. A third reader provided tie-breaking decisions for any disagreements.

RESULTS

Contrast-enhanced imaging data were collected from 29 patients with residual HCC post-TACE. On CEUS, 84.2% of patients with baseline APHE demonstrated APHE post-TACE (p = 0.25). On CE-MRI/CT, 57.1% of patients with baseline APHE later demonstrated APHE (p = 0.004). As for washout, on CEUS 33.3% of patients with baseline washout retained washout post-TACE (p = 0.01), while on CE-MRI/CT only 18.8% of patients with baseline washout later demonstrated washout (p < 0.001). Among CEUS readers, reader agreement was 100% for baseline APHE, 66.7% for baseline washout (K = 0.35), 84.2% for post-TACE APHE (K = 0.35), and 57.9% for post-TACE washout (K = - 0.09). On CE-MRI/CT, reader agreement was 65.5% for baseline APHE (K = 0.19), 55.2% for baseline washout (K = 0.12), 48.3% for post-TACE APHE (K = - 0.07), and 58.6% for post-TACE washout (K = 0.04).

CONCLUSION

Common diagnostic features of treatment-naïve HCC like APHE and washout can be substantially altered by TACE and should be considered when diagnosing residual disease on contrast-enhanced imaging.

Contrast-enhanced ultrasound is a reliable and reproducible assessment of necrotic ablated volume after radiofrequency ablation for benign thyroid nodules: a retrospective study

PURPOSE

To investigate the intra- and inter-observer reliability and agreement of contrast-enhanced ultrasound (CEUS) in measuring ablated volume (Va) after radiofrequency ablation (RFA) for benign thyroid nodules.

MATERIALS

This retrospective study evaluated 65 patients with 74 benign thyroid nodules who underwent RFA. Patients were followed up at 1, 3, 6, and 12 months and every 12 months thereafter. Two independent observers measured the Va using CEUS during the same follow-up visit. The intra- and inter-observer reliability was assessed using intraclass correlation coefficient (ICC) with 95% confidence interval. The Bland-Altman analysis was used to evaluate the inter-observer agreement, which was expressed as a mean difference with 95% limit of agreement (LOA).

RESULTS

No significant difference was found in Va measurements by the two observers with a mean follow-up time of 41.17 ± 16.80 months (all p > 0.05). The intra- and inter-observer reliability were both excellent (ICC >0.90) at each follow-up period. The 95% LOA became wider over the follow-up period. The smallest 95% LOA was found at 1 month with a LOA from 0.8117 to 1.122, and the largest 95% LOA was from 0.5694 to 1.343 at 36 months.

CONCLUSIONS

CEUS could provide a reliable and reproducible assessment of Va after RFA for benign thyroid nodules. In clinical post-ablation follow-up, the irregular morphology of ablated area and the variation by different observers could not affect the assessment of Va by CEUS.

Can the Entire Ablative Hyperechoic Zone be Regarded as a Necrotic Lesion After Radiofrequency Ablation of the Liver?

Developments in image fusion technology made it possible to visualize the ablative margin on ultrasound (US). The purpose of the present study was to assess the ablative area of radiofrequency ablation for hepatocellular carcinoma and compare it with the ablative hyperechoic zone with a non-enhanced area on contrast-enhanced US/contrast-enhanced computed tomography (CEUS/CECT) in the same cross-section. This retrospective study included 25 patients with 27 hepatocellular carcinomas. The long and short dimensions of the ablative hyperechoic zone were measured using B-mode US, and those of the non-enhanced area were assessed with CEUS/CECT on the same cross-section measured with B-mode US, using image fusion techniques. The technical effectiveness of ablation with an adequate ablative margin in a single session was determined in all patients. The long and short dimensions of the ablative hyperechoic zone ranged between 15.0 and 40.7 mm (mean: 27.3 ± 6.9 mm) and between 14.0 and 33.0 mm (mean: 23.3 ± 5.8 mm), respectively. R values for the long and short dimensions were 0.99 and 0.98, respectively, between B-mode US and CEUS, and 0.96 and 0.92, respectively, between B-mode US and CECT. The ablative hyperechoic zone may be regarded as a necrotic lesion after radiofrequency ablation.

Additional Diagnostic Value of Fusion Imaging of CEUS and First CEUS of Invisible Hepatic Lesions ≤2 cm

OBJECTIVE

To explore the clinical value of image fusion of contrast-enhanced ultrasonography (CEUS) and contrast-enhanced computed tomography (CECT) in the diagnosis of invisible lesions with a size ≤2 cm on conventional ultrasound imaging, and compare it with the clinical value of "first CEUS" .

METHODS

A total of 132 patients with 147 lesions with abnormal blood supply with a size ≤2 cm on CECT were included in this study. "first CEUS" was performed for these lesions. Then "fusion CEUS," that is, CEUS administered after fusion of US and CECT images, was carried out. The detection rates of the "first CEUS" and "fusion CEUS" were compared. How "fusion CEUS" corrects the misdiagnosis of liver lesions on CECT was analyzed.

RESULTS

One hundred nine lesions considered as HCC and 38 lesions considered as benign lesions on CECT were included. The detection rates for the lesions of "first CEUS" and "fusion CEUS" were 71.4% and 96.6%, respectively (P < 0.001). Among the 147 lesions, 68 were with a diameter ≤ 1 cm. The detection rate of "first CEUS" and "fusion CEUS" were 55.9% and 95.6%, respectively (P < 0.001) for the lesions with a size ≤1 cm. "Fusion CEUS" and "first CEUS" corrected the misdiagnosis in 2 lesions on CECT.

CONCLUSION

The "first CEUS" and "fusion CEUS" can improve the lesion conspicuity. Compared with "first CEUS," "fusion CEUS" has a higher diagnostic ability and hence can detect most of the invisible lesions on the former.

Contrast enhanced ultrasound (CEUS) with parametric imaging after irreversible electroporation (IRE) of the prostate to assess the success of prostate cancer treatment

AIM

The aim of this study was to assess the success of irreversible electroporation (IRE) in prostate cancer and to differentiate between reactive changes and tumor.

MATERIAL AND METHODS

This is a retrospective pilot study of 50 patients after irreversible electroporation (IRE) in prostate cancer between 50-79 years (mean age 65 years). Each patient received a transabdominal sonography using a 1-6 MHz convex matrix probe. Contrast-enhanced ultrasound (CEUS) was performed after i.v. bolus injection of 2.0 ml sulphur hexafluoride microbubbles. DICOM loops were continuously stored up to one minute. Parametric images were calculated by integrated perfusion analysis software. A comparison was drawn to a follow-up MRI six months after ablation.

RESULTS

While 13 patients showed local recurrence, 37 patients were successfully treated, meaning no local recurrence within six months after ablation. 18 patients showed signs of prostatitis after IRE. Tumorous changes were visually characterized by dynamic early nodular hypervascularization with fast and high wash-in. Correspondingly, nodular red and yellow shades were seen in parametric imaging. All patients with remaining tumor were correctly identified with CEUS and parametric imaging. After IRE there is a relevant decrease in tumor microcirculation in all patients, as seen in more purple shades of the prostate. The sensitivity for detecting residual tumor with CEUS compared to MRI was 76%, the specificity was 81%. The corresponding positive predictive value (PPV) was 73% and the negative predictive value (NPV) was 83%.

CONCLUSION

CEUS and parametric imaging enable a critical analysis of post-ablation defects after IRE for prostate cancer even with a transabdominal approach. Remaining tumor can be detected with the help of pseudo-colors.

Clinical Applications of Superb Microvascular Imaging in the Superficial Tissues and Organs: A Systematic Review

Superb microvascular imaging (SMI) is an innovative Doppler technique for vascular examination. It uses an intelligent algorithm that efficiently separates low-speed flow signals from motion artifacts so that it can assess microvessels and the vessel distribution in detail. This article reviews the clinical applications of SMI in the disorders of superficial tissues and organs including thyroid nodules, breast tumors and lymph node diseases etc. More information of diseases that are closely associated with angiogenesis can be shown by SMI than other noninvasive examinations. Although some limitations exist, this safe and convenient technique is becoming acceptable and would play a more important role in disease diagnosis and therapeutic responses evaluation.

Contrast-enhanced US for the Interventional Radiologist: Current and Emerging Applications

US is a powerful and nearly ubiquitous tool in the practice of interventional radiology. Use of contrast-enhanced US (CEUS) has gained traction in diagnostic imaging given the recent approval by the U.S. Food and Drug Administration (FDA) of microbubble contrast agents for use in the liver, such as sulfur hexafluoride lipid-type A microspheres. Adoption of CEUS by interventional radiologists can enhance not only procedure guidance but also preprocedure patient evaluation and assessment of treatment response across a wide spectrum of oncologic, vascular, and nonvascular procedures. In addition, the unique physical properties of microbubble contrast agents make them amenable as therapeutic vehicles in themselves, which can lay a foundation for future therapeutic innovations in the field in drug delivery, thrombolysis, and vascular flow augmentation. The purpose of this article is to provide an introduction to and overview of CEUS aimed at the interventional radiologist, highlighting its role before, during, and after frequently practiced oncologic and vascular interventions such as biopsy, ablation, transarterial chemoembolization, detection and control of hemorrhage, evaluation of transjugular intrahepatic portosystemic shunts (TIPS), detection of aortic endograft endoleak, thrombus detection and evaluation, evaluation of vascular malformations, lymphangiography, and percutaneous drain placement. Basic physical principles of CEUS, injection and scanning protocols, and logistics for practice implementation are also discussed. Early adoption of CEUS by the interventional radiology community will ensure rapid innovation of the field and development of future novel procedures. Online supplemental material is available for this article. ^©RSNA, 2020.

Microwave Ablation of Visible Benign Thyroid Nodules with Different Internal Characteristics: A Comparative Study with Follow-up Results

PURPOSE

To investigate the effects of microwave ablation (MWA) on visible benign thyroid nodules (BTN) with different internal characteristics.

MATERIALS & METHODS

A total of 51 cases with 53 visible BTN were treated by ultrasound-guided percutaneous MWA. The 53 nodules were classified into three categories according to the internal characteristics, which were simple solid, mainly solid and mainly cystic nodules. Ultrasound examinations were performed to evaluate the volume shrinkage rations during follow-up. The thyroid functions and the cervical cosmetic scores were evaluated. The complications were observed during and after ablation.

RESULTS

A total of 53 symptomatic BTN were treated by MWA completely. The average volume of the nodules was 11.68 ± 10.16 ml, the volume reduction rates (VRR) at 1st, 3rd, 6th, 12th, and 18th months after ablation were 0.29 ± 0.27, 0.46 ± 0.25, 0.67 ± 0.19, 0.83 ± 0.10, and 0.92 ± 0.10, respectively. The VRR was significantly different among the three categories of lesions (p < 0.05). The symptoms of all patients were improved. Thyroid function indicators were fluctuated in normal range. There were no serious complications during and after the procedure.

CONCLUSION

MWA of visible BTN is safe and effective, and the short-time ablation effect is significantly different due to the internal characteristics of the nodule.

SN, Kulkarni SS, Shetty NS, Gupta A, Gupta S. Indian Society of Vascular and Interventional Radiology Expert Consensus Statements for Ablation in Hepatocellular Carcinoma: Part II

Locoregional therapies play an important role in the management of hepatocellular carcinoma (HCC). Percutaneous ablation is one of the most commonly employed nonsurgical methods for treating very early and early HCC. For small HCC, ablation is potentially curative and competes with surgical resection. The widespread availability and the spectrum of ablative techniques mandate uniform approach among interventional radiologists. Thus, it is desirable to have a consensus regarding various aspects of the liver ablation. This article represents a consensus document of the experts from the Indian Society of Vascular and Interventional Radiology involved in the care of patients with HCC. The statements are presented in two parts.

Alteration of contrast enhanced ultrasound (CEUS) of hepatocellular carcinoma in patients with cirrhosis and transjugular intrahepatic portosystemic shunt (TIPS)

Transjugular intrahepatic portosystemic shunt (TIPS) can treat portal hypertensive complications and modifies hepatic hemodynamics. Modification of liver perfusion can alter contrast enhancement dynamics of liver nodules. This study investigated the diagnostic performance of contrast-enhanced ultrasound (CEUS) to diagnose hepatocellular carcinoma (HCC) in cirrhosis with TIPS. In this prospective monocentric observational study, CEUS was used to characterize focal liver lesions in patients at risk for HCC with and without TIPS. Times of arterial phase hyperenhancement (APHE) und washout were quantified. Perfusion-index (PI) and resistance-index (RI) of hepatic artery and portal venous flow parameters were measured via doppler ultrasonography. Diagnostic gold standard was MRI/CT or histology. This study included 49 liver lesions [23 TIPS (11 HCC), 26 no TIPS (15 HCC)]. 26 were diagnosed as HCC by gold standard. Sensitivity and specificity of CEUS to diagnose HCC with and without TIPS were 93.3% and 100% vs. 90.9% and 93.3%, respectively. APHE appeared significantly earlier in patients with TIPS compared to patients without TIPS. TIPS significantly accentuates APHE of HCC in CEUS. CEUS has good diagnostic performance for diagnosis of HCC in patients with TIPS.

Benefits of contrast-enhanced ultrasonography for interventional procedures

For evaluating unclear tumorous lesions, contrast-enhanced ultrasonography (CEUS) is an important imaging modality in addition to contrast-enhanced computed tomography and magnetic resonance imaging, and may provide valuable insights into the microvascularization of tumors in dynamic examinations. In interventional procedures, CEUS can make a valuable contribution in pre-, peri-, and post-interventional settings, reduce radiation exposure and, under certain circumstances, decrease the number of interventions needed for patients.

Non-enhanced ultrasound is not a satisfactory modality for measuring necrotic ablated volume after radiofrequency ablation of benign thyroid nodules: a comparison with contrast-enhanced ultrasound

OBJECTIVE

To investigate the intra- and inter-observer reliability and agreement between gray-scale and Doppler ultrasound (US) and contrast-enhanced ultrasound (CEUS) in measuring ablated volume (Va) after radiofrequency ablation (RFA) for benign thyroid nodules.

METHODS

A total of 173 patients with 190 benign thyroid nodules who underwent RFA were included in this study. After RFA, the total volume of ablated nodule was divided into Va and the incompletely treated vital volume. Patients were followed up at 1, 3, 6, 12 months, and every 12 months thereafter. Two independent observers measured Va using US and CEUS during the same follow-up visit. The intra- and inter-observer reliability of the two measurement modalities was assessed using intraclass correlation coefficient (ICC) with 95% confidence interval. The Bland-Altman analysis was used to evaluate agreement, which was expressed as a mean difference with 95% limits of agreement (LOA).

RESULTS

The mean follow-up time was 23.17 ± 12.70 months. Va measured by US was significantly larger than by CEUS (p < 0.001). The intra- and inter-observer reliability decreased over the follow-up period and became moderate in both subgroups at 12 months (all ICC < 0.75). The mean difference and LOA became larger and wider during the follow-up. The best agreement was found in nodules < 10 ml at 1 month with a mean difference of 1.166 and LOA between 0.413 and 3.294.

CONCLUSIONS

The intra- and inter-observer reliability and agreement of US and CEUS in measuring Va were unsatisfactory. CEUS should be considered when Va was needed for further evaluation or in the case of nodules with suspected regrowth.

KEY POINTS

• Va measured by gray-scale and Doppler US was significantly larger than that by CEUS. • Va measured by gray-scale and Doppler US lacked intra- and inter-observer reliability and agreement with CEUS. • CEUS should be preceded to gray-scale and Doppler US for the measurement of Va.

Early Identification of Residual Tumors following Microwave Ablation Using Contrast-Enhanced Ultrasonography in a Rabbit VX2 Liver Cancer Model

Objective

It is difficult to evaluate the ablation effect immediately after thermal ablation of liver cancer by clinical imaging methods, due to the immediate formation of an annular inflammatory reaction band (IRB). This study is aimed at exploring the early identification indicators of the IRB and residual tumor postmicrowave ablation (MVA) using contrast-enhanced ultrasonography (CEUS).

Methods

MVA was used to inactivate part of the tumor nodules in rabbit VX2 liver cancer models, leading to the coexistence of the IRB with residual tumors. Quantitative analysis of the perfusion parameters of the tumor and ablation zone was performed using CEUS, followed by liver biopsy and VEGFR-2 immunohistochemical staining.

Results

All rabbits successfully tolerated VX2 tumor inoculation and MVA operation. No statistically significant difference existed between the IRB vs. residual tumors, the IRB vs. junctional areas, and residual tumors postablation vs. VX2 tumors before ablation in regional blood volume, blood velocity, and blood flow estimated by parameters A, k, and A^∗k of CEUS quantitative analysis. There was a statistically significant difference between the IRB and normal liver parenchyma in regional blood velocity and blood flow (p = 0.005 and p = 0.023, respectively). Normal liver parenchyma showed nonspecific VEGFR-2 staining, while VX2 tumor before ablation and residual tumor after ablation both showed positive VEGFR-2 staining; the necrosis zone showed negative staining by VEGFR-2 immunohistochemical staining.

Conclusion

MVA had no significant effect on the residual tumor hemodynamics. The blood flow in the IRB increased significantly as compared to normal liver parenchyma, resembling tumor hemodynamic patterns. CEUS can detect residual tumors immediately postablation only when they protrude from the annular-shaped IRB. In addition, VEGFR-2 targeted CEUS may have a great potential for detecting residual tumor after thermal ablation of hepatocellular carcinoma.

Evaluation of liver tumour response by imaging

The goal of assessing tumour response on imaging is to identify patients who are likely to benefit - or not - from anticancer treatment, especially in relation to survival. The World Health Organization was the first to develop assessment criteria. This early score, which assessed tumour burden by standardising lesion size measurements, laid the groundwork for many of the criteria that followed. This was then improved by the Response Evaluation Criteria in Solid Tumours (RECIST) which was quickly adopted by the oncology community. At the same time, many interventional oncology treatments were developed to target specific features of liver tumours that result in significant changes in tumours but have little effect on tumour size. New criteria focusing on the viable part of tumours were therefore designed to provide more appropriate feedback to guide patient management. Targeted therapy has resulted in a breakthrough that challenges conventional response criteria due to the non-linear relationship between response and tumour size, requiring the development of methods that emphasize the appearance of tumours. More recently, research into functional and quantitative imaging has created new opportunities in liver imaging. These results have suggested that certain parameters could serve as early predictors of response or could predict later tumour response at baseline. These approaches have now been extended by machine learning and deep learning. This clinical review focuses on the progress made in the evaluation of liver tumours on imaging, discussing the rationale for this approach, addressing challenges and controversies in the field, and suggesting possible future developments.

The Role of Contrast-Enhanced Ultrasound in the Diagnosis and Pathologic Response Prediction in Breast Cancer: A Meta-analysis and Systematic Review

PURPOSE

To determine the overall performance of contrast-enhanced ultrasound (CEUS) in differentiating between benign and malignant breast lesions and in predicting the pathologic response to neoadjuvant chemotherapy (NAC) in patients with breast cancer (BC).

MATERIALS AND METHODS

Articles published up to April 2019 were systematically searched in Medline, Web of Science, and China National Knowledge Infrastructure. The sensitivities and specificities across studies, the calculations of positive and negative likelihood ratios (LR⁺ and LR^-), diagnostic odds ratio (OR), and constructed summary receiver operating characteristic curves were determined. Methodologic quality was assessed using the QUADAS (Quality Assessment of Diagnostic Accuracy Studies) tool. Subgroup analyses and metaregression were performed on prespecified study-level characteristics.

RESULTS

Fifty-one studies involving 4875 patients with 5246 breast lesions and 10 studies involving 462 patients with BC receiving NAC were included. Methodologic quality was relatively high, and no publication bias was detected. The overall sensitivity, specificity, diagnostic OR, LR⁺, and LR^- for CEUS were 0.88 (95% confidence interval [CI], 0.86-0.89), 0.82 (95% CI, 0.80-0.83), 30.55 (95% CI, 21.40-43.62), 4.29 (95% CI, 3.51-5.25), and 0.16 (95% CI, 0.13-0.21), respectively, showing statistical heterogeneity. Multivariable metaregression analysis showed contrast mode to be the most significant source of heterogeneity. The overall sensitivity, specificity, LR⁺, LR, and diagnostic OR of CEUS imaging in predicting the overall pathologic response to NAC in patients with BC were 0.89 (95% CI, 0.83-0.93), 0.83 (95% CI, 0.78-0.88), 4.49 (95% CI, 3.04-6.62), 0.16 (95% CI, 0.10-0.24,), and 32.21 (95% CI, 16.74-62.01), respectively, showing mild heterogeneity.

CONCLUSION

Our data confirmed the excellent performance of breast CEUS in differentiating between benign and malignant breast lesions as well as pathologic response prediction in patients with BC receiving NAC.

The Application Comparison of Contrast-Enhanced Ultrasound and Contrast-Enhanced Computed Tomography in Radiofrequency Ablation Treatment for Hepatocellular Carcinoma

Objective: To compare the application value of contrast-enhanced ultrasound (CEUS) and contrast-enhanced computed tomography (CECT) in radiofrequency ablation (RFA) for treatment of hepatocellular carcinoma (HCC). Methods: A total of 112 patients with primary HCC were enrolled for the treatment of RFA and they were randomly equally divided into the CEUS group and CECT group. The gender, age, and number and maximum diameter of tumors between the two groups were compared. The median duration of follow-up was 27.0 months and the clinical outcomes were compared. Results: The average examination time period before ablation, of guiding needle insertion and of ablation in the CEUS group were significantly shorter than those in the CECT group (p < 0.05). The complete ablation rate of the CEUS group was significantly higher than that of the CECT group (86.36% vs. 73.17%, χ² = 4.618, p = 0.032). There was no comparative difference in the incidence of complications (including fever, infection, pain, and liver injury) between the two groups (p > 0.05). The relapse rate of the CEUS group was lower and the survival rate was higher than that in the CECT group (p < 0.05). Conclusions: Compared with the CECT, the RFA for treatment of HCC guided by the CEUS shorten the time of examination and treatment. The immediate postoperative assessment can improve the overall complete ablation rate, reduce the relapse rate, and increase the survival rate, which provides insights for the clinical application.

Application of Contrast-Enhanced Ultrasound in the Diagnosis of Ductal Carcinoma In Situ: Analysis of 127 Cases

OBJECTIVES

To explore the characteristics of breast ductal carcinoma in situ (DCIS) on real-time grayscale contrast-enhanced ultrasound (CEUS) imaging and the diagnostic value of CEUS in DCIS.

METHODS

A total of 127 histopathologically confirmed DCIS lesions and 124 fibroadenomas (FAs; controls) were subjected to conventional ultrasound and CEUS. Next, the CEUS findings of DCIS and FA lesions, including morphologic features and quantitative parameters, were analyzed.

RESULTS

Binary logistic regression was used to identify the independent risk factors from DCIS and FA lesions detected by CEUS. Contrast-enhanced ultrasound revealed significant differences between DCIS and FA. The wash-in time, enhancement mode, enhancement intensity, blood perfusion defects, peripheral high enhancement, enhancement scope, intratumoral vessels and their courses and dilatation degree, and penetrating vessels on CEUS were identified as features correlated with DCIS (P < .05). Moreover, a multivariate logistic regression analysis was developed, and the area under receiver operating characteristic curve of each index was generated, including the wash-in time, enhancement intensity, blood perfusion defects, enhancement scope, penetrating vessels, arrival time, and peak intensity (P < .05; area under the curve, >0.6).

CONCLUSIONS

The contrast-enhancement patterns and DCIS parameters appeared different from FA lesions, thus suggesting that CEUS can be very useful in distinguishing DCIS from FA lesions.

Clinical Applications of Superb Microvascular Imaging in the Liver, Breast, Thyroid, Skeletal Muscle, and Carotid Plaques

This article reviews the clinical applications of Superb Microvascular Imaging (SMI; Canon Medical Systems, Otawara, Japan) in the liver, breast, thyroid, skeletal muscle, and carotid plaques. Diseases that are closely associated with angiogenesis can be diagnosed by SMI in a relatively early phase, and using SMI can prevent adverse reactions associated with the contrast agents used in contrast-enhanced ultrasound. Super Microvascular Imaging also shows particular value in grading disease activities and monitoring therapeutic responses. Although SMI has some limitations, such as a lack of clinical standards, it can add information to conventional ultrasound examinations and may become a noninvasive alternative to invasive diagnostic procedures for many clinical conditions.

Contrast-enhanced US in Local Ablative Therapy and Secondary Surveillance for Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) has a high incidence of recurrence following therapy. Therefore, secondary surveillance (scheduled follow-up imaging after treatment) is an important part of disease management. The recent approval in the United States for use of a microbubble-based contrast agent for US liver imaging promotes the increased use of contrast-enhanced US (CEUS) in patients with HCC. Although the criteria for the diagnosis of HCC at CEUS are well described, there is a paucity of published literature describing the role of CEUS in ablative therapy and secondary surveillance. In the setting of ablative therapy, CEUS can have vital roles, including patient selection, intraprocedural guidance, and immediate postprocedural assessment. Although CEUS is not widely used, the authors found that it can be used to accurately detect residual or recurrent tumor, characterize the geographic pattern of recurrence (intrazonal, extrazonal, segmental, or remote), and assess for tumor in vein. In addition, similar to primary surveillance, secondary surveillance includes assessment of the entire liver for evaluation of new nodules. Arterial phase hyperenhancement is the reference standard characteristic of disease recurrence at secondary surveillance with CEUS. ^©RSNA, 2019 See discussion on this article by Rodgers.

Intraprocedural computed tomography/magnetic resonance-contrast-enhanced ultrasound fusion imaging improved thermal ablation effect of hepatocellular carcinoma: Comparison with conventional ultrasound

AIM

To retrospectively compare the treatment effect of intraprocedural computed tomography/magnetic resonance-contrast-enhanced ultrasound (CT/MR-CEUS) fusion imaging (FI) with that of conventional ultrasound (US) in the guidance and assessment of thermal ablation of hepatocellular carcinoma (HCC).

METHODS

The FI group (112 patients with 129 HCC) was treated between April 2010 and December 2012, whereas the US group (83 patients with 90 HCC) was treated between January 2008 and March 2010. Either CT/MR-CEUS FI or US was used to guide puncture, provide immediate assessment, and guide supplementary ablation. Technical efficacy, cumulative local tumor progression rate (LTP), recurrence-free survival (RFS), and overall survival (OS) were evaluated and compared during follow-up. Technical success rate of CT/MR-CEUS FI was also recorded.

RESULTS

Technical efficacy was significantly higher in the FI group than in the US group (100% vs. 86.7%, P < 0.001). The 1-, 2-, 3-, 4-, 5-, and 6-year cumulative LTP rates in the FI group were significantly lower than in the US group (3.8%, 4.9%, 6.0%, 6.0%, 7.2%, and 7.2% vs. 16.9%, 20.1%, 25%, 25%, 25%, and 25%, respectively; P < 0.001); RFS and OS were significantly higher in the FI group than in the US group (P = 0.027 and P = 0.049, respectively). The technical success rate of FI was 85.3%.

CONCLUSIONS

Intraprocedural CT/MR-CEUS FI improved the treatment effect of thermal ablation of HCC by immediately assessing treatment response and guiding supplementary ablation relative to those resulting from the use of conventional US.

Clinical application of ultrasound-guided percutaneous microwave ablation for benign breast lesions: a prospective study

BACKGROUND

Background: Benign breast lesions are the most common diseases in adult women, which have been treated with minimally invasive therapies in recent years. Little is known about the feasibility of Microwave ablation (MWA) for benign breast lesion treatment. The primary aim of this prospective study was to evaluate the safety and efficiency of MWA as a potential therapeutic option for benign breast lesions in a single-center cohort study.

METHODS

Women with possibly benign breast lesions based on an ultrasound (US) assessment who were scheduled to undergo MWA between November 2014 to July 2018 were included in the study. The patients underwent conventional US to measure the size of the lesion, Doppler US to assess the vascularity of the lesion, elastography to evaluate the stiffness of the mass, core needle biopsy of suspicious lesions, contrast-enhanced US to help determine the treatment plan and eventually MWA of the lesion. Lesions were followed at one, three, six, twelve and eighteen months after treatment to with the same imaging modalities.

RESULTS

A total of 314 women aged 17 to 69 years old (mean = 36.9 ± 9.9 years) with 725 benign breast lesions (mean of maximum diameter = 10.86 ± 5.40 mm) were included. The frequency of palpable mass, pain and nipple discharge significantly decreased after treatment. Complete ablation rate was 97.8%, immediately after ablation, which increased to 100% after supplementary ablation of the 15 cases with incomplete ablation. Blood flow classification and lesion's volume also showed a significant decrease, while both volume reduction ratio and disappearance rate significantly increased following treatment. The elasticity score of the lesions showed fluctuations across different follow-up intervals. None of the patients experienced major complications and the 1% who had mild symptoms were successfully treated.

CONCLUSION

MWA treatment is shown to be safe and efficient and has the potential to be considered as an alternative first line treatment for benign breast lesions.

Quantitative evaluation of blood perfusion in hepatocellular carcinoma after transcatheter arterial chemoembolization by contrast-enhanced ultrasound

AIM

To evaluate the blood perfusion status of residual hepatocellular carcinoma (HCC) tumors after transcatheter arterial chemoembolization (TACE) by contrast-enhanced ultrasound (CEUS) as well as the application value of CEUS.

METHODS

A total of 45 HCC patients with a total of 57 tumors who underwent TACE at our hospital were selected. CEUS was performed one day before treatment and one month after treatment. The blood perfusion parameters of residual tumors before and after TACE were compared.

RESULTS

The sensitivity, accuracy, and specificity of CEUS in the diagnosis of residual HCC lesions were 95.45%, 94.74%, and 92.31%, respectively. The enhanced intensity (56.87% ± 4.15%) of residual HCC tumors after TACE decreased significantly compared with that (75.09% ± 6.42%) before TACE (P < 0.05). The peak time (25.26 s ± 3.83 s) of HCC residual tumors after TACE was significantly longer than that (21.02 s ± 3.70 s) before TACE (P < 0.05). The area under the curve (581.29 ± 86.43) for residual HCC tumors decreased significantly compared with that (1017.83 ± 111.76) before TACE (P < 0.05).

CONCLUSION

CEUS can directly reflect the residual state of HCC after TACE and quantitatively evaluate the blood perfusion change of residual tumors, which can provide hemodynamic information for further clinical treatment.

Unenhanced magnetic resonance imaging immediately after radiofrequency ablation of liver malignancy: preliminary results

PURPOSE

To assess the accuracy of unenhanced magnetic resonance imaging (MRI) immediately after the percutaneous ultrasound-guided radiofrequency ablation (RFA) of liver malignancy in predicting treatment efficacy at CT follow-up.

MATERIALS AND METHODS

Percutaneous ablation was prospectively performed in 23 liver malignancies (20 hepatocarcinomas and 3 metastases). After the procedure in the same day all patients were studied with unenhanced MRI. The best sequence to detect the coagulative necrosis was visually established. Pre-RFA CT and post-RFA MRI were registered with non-rigid transformation algorithm. Manual segmentation of lesions and ablated areas in pre-RFA CT, post-RFA MRI, and follow-up CT were obtained. Sensitivity, specificity, positive predictive value (PPV), negative predicitve value (NPV), and accuracy of MRI in predicting the correct centering and the complete treatment of the lesion were calculated in respect to the 1-month follow-up CT.

RESULTS

Fat-saturated T1-weighted (fs T1-w) was the sequence in which the best conspicuity of the ablated area was depicted. Coagulative necrosis was hyperintense in fs T1-w sequence in 17/23 (74%). In respect to follow-up CT, MRI predicted the correct centering of the lesions in 19/20 lesions with sensitivity, specificity, PPV, NPV, and accuracy of 100%, 75%, 95%, 100%, and 100%, respectively. MRI predicted the complete treatment of the lesions in 17/17 lesions with sensitivity, specificity, PPV, NPV, and accuracy of 100%.

CONCLUSION

MRI with the single fs T1-w sequence was highly accurate in predicting the treatment efficacy of percutaneous ablation of liver malignancies in comparison to follow-up CT control. Unnecessary CT in case of incomplete treatment can be therefore easily avoided.

Use of Ultrasound Contrast Agents in Relation to Percutaneous Interventional Procedures: A Systematic Review and Pictorial Essay

The aim of this article is to provide an inventory of the use of contrast-enhanced ultrasound (CEUS) in relation to percutaneous interventional procedures. The article is structured into a systematic literature review followed by a clinical part relating to percutaneous CEUS-guided procedures. A literature search identified 3109 records. After abstract screening, 55 articles were analyzed and supplemented with pictorial material to explain the techniques. In conclusion, the best-evidenced indications for CEUS-guided interventions are biopsy and ablation of inconspicuous or B-mode-invisible tumors, intraprocedural ablation control and follow-up, as well as percutaneous transhepatic cholangiography and drainage procedures.

Monitoring after radiofrequency ablation of liver tumors: contrast-enhanced ultrasound (CEUS) vs. contrast-enhanced computer tomography (CECT), two days after procedure

AIM

Our research evaluated the ability of contrast-enhanced ultrasound (CEUS) and contrast enhanced computer tomography (CECT), performed 48 h after radiofrequency ablation (RFA), to detect residual tumor tissue. As recently published studies have evaluated periprocedural CEUS performed within 24 h after procedure and their results were not satisfactory, it seems that postponing the control test by one day could increase the sensitivity of both methods.

PATIENTS AND METHODS

We evaluated 33 patients with 37 lesions, who met the criteria for our study. The criteria were 1) the treated lesion is sonographically viewable and 2) the patient underwent both CEUS and CECT control 48 h after treatment and additional follow-up 3 months later by CECT. Presence of residual tumor tissue and the size of necrosis were recorded and compared to the results of 3-months CECT.

RESULTS

Nine residues were present in our group. CEUS and CECT showed similar sensitivity (66.7% and 77.8%, respectively) and identical specificity (both 96.4%) for detection of residual tumor tissue. CEUS significantly underestimated the size of necrosis in comparison to CECT (on average by 2.4 mm, P=0.0005). Over the 3-months follow-up period the size of necrosis decreased in all patients (on average by 7.2 mm, P<0.0001).

CONCLUSION

The quality of tumor residue detection in 48-h CEUS was comparable to that of 48-h CECT. This finding suggests the CEUS being a feasible substitute for CECT. Both methods show reasonable sensitivity; therefore this timing seems to be appropriate for the first post-treatment control while also allowing for early retreatment if residual tumor tissue is found.

Contrast-enhanced ultrasound (CEUS) in abdominal intervention

The introduction of ultrasound contrast agents has rendered contrast-enhanced ultrasound (CEUS) a valuable complementary technique to address clinically significant problems. This pictorial review describes the use of CEUS guidance in abdominal intervention and illustrates such application for a range of clinical indications. Clinical application of CEUS discussed include commonly performed abdominal interventional procedures, such as biopsy, drainage, nephrostomy, biliary intervention, abdominal tumor ablation and its subsequent monitoring, and imaging of vascular complications following abdominal intervention. The purpose of this article is to further familiarize readers with the application of CEUS, particularly its specific strength over alternative imaging modalities, in abdominal intervention.

A Comparative Study of Ablation Boundary Sharpness After Percutaneous Radiofrequency, Cryo-, Microwave, and Irreversible Electroporation Ablation in Normal Swine Liver and Kidneys

PURPOSE

To compare ablation boundary sharpness after percutaneous radiofrequency ablation (RFA), cryoablation (CA), microwave ablation (MWA) and irreversible electroporation (IRE) ablation in normal swine liver and kidney.

MATERIALS AND METHODS

Percutaneous CT-guided RFA (n = 5), CA (n = 5), MWA (n = 5) and IRE (n = 5) were performed in the liver and kidney of four Yorkshire pigs. Parameters were chosen to produce ablations 2-3 cm in diameter with a single ablation probe. Contrast-enhanced CT imaging was performed 24 h after ablation, and animals were killed. Treated organs were removed and processed for histologic analysis with hematoxylin and eosin, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL). Three readers independently analyzed CT, H&E and TUNEL stained images of the ablation boundary to delineate regions of (1) viable cells, (2) complete necrosis or (3) mixture of viable and necrotic cells which was defined as the transition zone (TZ). The width of TZ was compared across the techniques and organs.

RESULTS

Ablations appeared as non-contrast-enhancing regions on CT with sharp transition to enhancing normal tissue. On TUNEL stained slides, the mean width (μm) of the TZ after MWA was 319 ± 157 in liver and 267 ± 95 in kidney, which was significantly lower than RFA (811 ± 477 and 938 ± 429); CA (452 ± 222 and 700 ± 563); and IRE (1319 ± 682 and 1570 ± 962) (all p < 0.01). No significant differences were observed between the organs.

CONCLUSION

Under similar conditions, the width of the TZ at the ablation boundary varies significantly between different ablation techniques.

Percutaneous irreversible electroporation for breast tissue and breast cancer: safety, feasibility, skin effects and radiologic-pathologic correlation in an animal study

Background

To study the safety, feasibility and skin effects of irreversible electroporation (IRE) for breast tissue and breast cancer in animal models.

Methods

Eight pigs were used in this study. IRE was performed on the left breasts of the pigs with different skin–electrode distances, and the right breasts were used as controls. The electrodes were placed 1–8 mm away from the skin, with an electrode spacing of 1.5–2 cm. Imaging and pathological examinations were performed at specific time points for follow-up evaluation. Vital signs, skin damage, breast tissue changes and ablation efficacy were also closely observed. Eight rabbit models with or without VX2 breast tumor implantations were used to further assess the damage caused by and the repair of thin skin after IRE treatment for breast cancer. Contrast-enhanced ultrasound and elastosonography were used to investigate ablation efficacy and safety.

Results

During IRE, the color of the pig breast skin reversibly changed. When the skin–electrode distance was 3 mm, the breast skin clearly changed, becoming white in the center and purple in the surrounding region during IRE. One small purulent skin lesion was detected several days after IRE. When the skin–electrode distance was 5–8 mm, the breast skin became red during IRE. However, the skin architecture was normal when evaluated using gross pathology and hematoxylin-eosin staining. When the skin–electrode distance was 1 mm, skin atrophy and yellow glabrescence occurred in the rabbit breasts after IRE. When the skin–electrode distance was ≥5 mm, there was no skin damage in the rabbit model regardless of breast cancer implantation. After IRE, complete ablation of the targeted breast tissue or cancer was confirmed, and apoptosis was detected in the target tissue and outermost epidermal layer. In the ablated breasts of the surviving animals, complete mammary regeneration with normal skin and hair was observed. Furthermore, no massive fibrosis or mass formation were detected on ultrasound or through hematoxylin–eosin staining.

Conclusions

After IRE, the skin architecture was well preserved when the skin–electrode distance was ≥5 mm. Moreover, breast regeneration occurred without mass formation or obvious fibrosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-0993-7) contains supplementary material, which is available to authorized users.