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

FI-CEUS: a solution to improve the diagnostic accuracy in MRI LI-RADS-indeterminate (LR-3/4) FLLs at risk for HCC

Objective

To evaluate the diagnostic accuracy of fusion imaging contrast-enhanced ultrasound (FI-CEUS) of magnetic resonance imaging (MRI) LI-RADS-indeterminate (LR-3/4) and conventional ultrasound undetected focal liver lesions (FLLs) in patients at risk for hepatocellular carcinoma (HCC).

Methods

Between February 2020 and July 2021, 71 FLLs in 63 patients were registered for diagnostic performance evaluation respectively for ultrasound-guided thermal ablation evaluation in this retrospective study. Diagnostic performance regarding FLLs was compared between FI-CEUS and contrast-enhanced MRI (CE-MRI).

Results

For diagnostic performance evaluation, among 71 lesions in 63 patients, the diagnostic efficacy of FI-CEUS with LI-RADS was significantly higher than that of CE-MRI (P < 0.05) in both overall and hierarchical comparison (except for the group with lesion diameter ≥2 cm). For malignant lesions, the proportion of arterial phase hyperenhancement (APHE) and washout on FI-CEUS was higher than that on CE-MRI (P < 0.05).

Conclusion

FI-CEUS has a high value in the precise qualitative diagnosis of small FLLs (<2 cm) of MRI LI-RADS-indeterminate diagnosis (LR-3/4) that are undetected by conventional ultrasound in patients at risk for HCC and can be a good supplementary CE-MRI diagnostic method for thermal ablation evaluation.

Qualitative Assessment of Contrast-Enhanced Ultrasound in Differentiating Clear Cell Renal Cell Carcinoma and Oncocytoma

BACKGROUND

We aimed to assess whether clear cell renal cell carcinoma (ccRCC) can be differentiated from renal oncocytoma (RO) on a contrast-enhanced ultrasound (CEUS).

METHODS

Between January 2021 and October 2022, we retrospectively queried and analyzed our prospectively maintained dataset. Renal mass features were scrutinized with conventional ultrasound imaging (CUS) and CEUS. All lesions were confirmed by histopathologic diagnoses after nephron-sparing surgery (NSS). A multivariable analysis was performed to identify the potential predictors of ccRCC. The area under the curve (AUC) was depicted in order to assess the diagnostic accuracy of the multivariable model.

RESULTS

A total of 126 renal masses, including 103 (81.7%) ccRCC and 23 (18.3%) RO, matched our inclusion criteria. Among these two groups, we found significant differences in terms of enhancement (homogeneous vs. heterogeneous) (p < 0.001), wash-in (fast vs. synchronous/slow) (p = 0.004), wash-out (fast vs. synchronous/slow) (p = 0.001), and rim-like enhancement (p < 0.001). On the multivariate logistic regression, heterogeneous enhancement (OR: 19.37; p = <0.001) and rim-like enhancement (OR: 3.73; p = 0.049) were independent predictors of ccRCC. Finally, these two variables had an AUC of 82.5% and 75.3%, respectively.

CONCLUSIONS

Diagnostic imaging for presurgical planning is crucial in the choice of either conservative or radical management. CEUS, with its unique features, revealed its usefulness in differentiating ccRCC from RO.

Ultrasound-New Techniques Are Extending the Applications

BACKGROUND

Sonography is often the first imaging procedure to be used in diagnostic investigation of the abdomen. The aim of this article is to provide a new interdisciplinary overview of recent groundbreaking advances in this modality.

METHODS

A selective survey of the literature in PubMed was conducted. The literature search was carried out in 2021-2022 and included publications over the period 2004-2022.

RESULTS

The novel sonographic software techniques can be divided into algorithms that deal with conventional B-scan optimization and new programs that extend the scope of sonographic examination. The latter include elastography, contrast-enhanced sonography, and image fusion in combination with other cross-sectional imaging modalities. Elastography can be used to assess the presence of steatosis, fibrosis, or cirrhosis in patients with liver disease. One study reported diagnostic accuracy of 84-87% for the diagnosis of significant fibrosis (F2), 89-91% for the diagnosis of severe fibrosis (F3), and 92-93% for the diagnosis of liver cirrhosis (F4). Contrast-enhanced sonography is used for evaluation of tumors and trauma. A prospective multicenter study found sensitivity of 95.8% for the characterization of malignant lesions and specificity of 83.1% for benign lesions. Image fusion has the potential to improve the diagnostic assessment of parenchymatous organs, vascular conditions, and the prostate.

CONCLUSION

With continuous improvement of the B-scan and the development of high-frequency probes and novel investigation techniques, sonography has become established as an increasingly autonomous examination procedure.

Image Fusion Involving Real-Time Transabdominal or Endoscopic Ultrasound for Gastrointestinal Malignancies: Review of Current and Future Applications

Image fusion of CT, MRI, and PET with endoscopic ultrasound and transabdominal ultrasound can be promising for GI malignancies as it has the potential to allow for a more precise lesion characterization with higher accuracy in tumor detection, staging, and interventional/image guidance. We conducted a literature review to identify the current possibilities of real-time image fusion involving US with a focus on clinical applications in the management of GI malignancies. Liver applications have been the most extensively investigated, either in experimental or commercially available systems. Real-time US fusion imaging of the liver is gaining more acceptance as it enables further diagnosis and interventional therapy of focal liver lesions that are difficult to visualize using conventional B-mode ultrasound. Clinical studies on EUS guided image fusion, to date, are limited. EUS-CT image fusion allowed for easier navigation and profiling of the target tumor and/or surrounding anatomical structure. Image fusion techniques encompassing multiple imaging modalities appear to be feasible and have been observed to increase visualization accuracy during interventional and diagnostic applications.

Ultrasound fusion biopsy

BACKGROUND

Ultrasound (US)-guided biopsy is widely used for the diagnostic confirmation of focal lesions. For sampling of prostate tissue, magnetic resonance imaging (MRI)/US fusion-guided biopsy has already been implemented in routine clinical practice and has shown a superior detection rate of significant prostate cancer in risk assessment compared with standard systematic biopsy. Newer three-dimensional software tools with volumetric mapping of the prostate and biopsy core channels provide a better overview of systematic biopsy and thus contribute to more accurate treatment planning. Automatic fusion is a time-saver and can reduce potential examiner errors through greater standardization of the fusion process itself.

METHODICAL INNOVATIONS

In abdominal pathologies, US fusion biopsy can improve the rate of successful tissue sampling by using fused imaging to target lesions that are barely visible or difficult to delineate on B‑mode US scans. In addition, solid portions within larger tumors with enhancement on contrast-enhanced US can be targeted selectively, thereby avoiding sampling of necrotic areas and improving the quality of tissue cores for histopathological work-up.

CONCLUSION

Especially in complex situations, use of US fusion not only saves time but also improves sampling accuracy, which in turn reduces the rate of insufficient tissue specimens that necessitate repeat biopsy.

Dynamic Contrast-Enhanced Ultrasound Radiomics for Hepatocellular Carcinoma Recurrence Prediction After Thermal Ablation

PURPOSE

To develop a radiomics model based on dynamic contrast-enhanced ultrasound (CEUS) to predict early and late recurrence in patients with a single HCC lesion ≤ 5 cm in diameter after thermal ablation.

PROCEDURES

We enrolled patients who underwent thermal ablation for HCC in our hospital from April 2004 to April 2017. Radiomics based on two branch convolution recurrent network was utilized to analyze preoperative dynamic CEUS image of HCC lesions to establish CEUS model, in comparison to the conventional ultrasound (US), clinical, and combined models. Clinical follow-up of HCC recurrence after ablation were taken as reference standard to evaluate the predicted performance of CEUS model and other models.

RESULTS

We finally analyzed 318 patients (training cohort: test cohort = 255:63). The combined model showed better performance for early recurrence than CUES (in training cohort, AUC, 0.89 vs. 0.84, P < 0.001; in test cohort, AUC, 0.84 vs. 0.83, P = 0.272), US (P < 0.001), or clinical model (P < 0.001). For late recurrence prediction, the combined model showed the best performance than the CEUS (C-index, in training cohort, 0.77 vs. 0.76, P = 0.009; in test cohort, 0.77 vs. 0.68, P < 0.001), US (P < 0.001), or clinical model (P < 0.001).

CONCLUSIONS

The CEUS model based on dynamic CEUS radiomics performed well in predicting early HCC recurrence after ablation. The combined model combining CEUS, US radiomics, and clinical factors could stratify the high risk of late recurrence.

Contrast-enhanced ultrasound of benign and malignant liver lesions in children

Contrast-enhanced ultrasound (CEUS) is increasingly being used in children. One of the most common referrals for CEUS performance is characterization of indeterminate focal liver lesions and follow-up of known liver lesions. In this setting, CEUS is performed with intravenous administration of ultrasound contrast agents (UCAs). When injected into a vein, UCA microbubbles remain confined within the vascular network until they dissipate. Therefore, visualization of UCA within the tissues and lesions corresponds to true blood flow. CEUS enables continuous, real-time observation of the enhancement pattern of a focal liver lesion, allowing in most cases for a definite diagnosis and obviating the need for further cross-sectional imaging or other interventional procedures. The recent approval of Lumason (Bracco Diagnostics, Monroe Township, NJ) for pediatric liver CEUS applications has spurred the widespread use of CEUS. In this review article we describe the role of CEUS in pediatric liver applications, focusing on the examination technique and interpretation of main imaging findings of the most commonly encountered benign and malignant focal liver lesions. We also compare the diagnostic performance of CEUS with other imaging modalities for accurate characterization of focal liver lesions.

The use of image fusion in prenatal medicine

Fusion imaging (FI), the simultaneous display of the same anatomical region using two imaging modalities, has been used in other areas of medicine for both diagnosis and guiding interventions. Examples include positron emission tomography-computed tomography (PET-CT) imaging in oncology and ultrasound-magnetic resonance imaging (US-MRI) fusion in biopsies of the prostate gland. The underlying principle is to take advantage of the complementary information in each modality to improve accuracy, be it diagnostic accuracy or targeting accuracy in biopsies. For example, PET-CT overlays the metabolic activity of lesions on the superb spatial and anatomical detail of CT. While the historical mainstay of fetal imaging has been ultrasound, advances in ultrafast MR imaging together with advances in fetal MRI over the past two decades, have resulted in the opportunity to explore fusion imaging in fetal medicine. We present an overview of the principles of US-MRI fusion imaging in prenatal medicine, report our local experience, and review the literature in this emerging area. We share our perspective on how FI can improve diagnostic confidence, be used as an educational tool, and potentially enhance guidance in certain fetal procedures.

[Contrast-enhanced ultrasound (CEUS) and image fusion for procedures of liver interventions]

CLINICAL/METHODICAL ISSUE

Contrast-enhanced ultrasound (CEUS) is becoming increasingly important for the detection and characterization of malignant liver lesions and allows percutaneous treatment when surgery is not possible. Contrast-enhanced ultrasound image fusion with computed tomography (CT) and magnetic resonance imaging (MRI) opens up further options for the targeted investigation of a modified tumor treatment.

METHODICAL INNOVATIONS

Ultrasound image fusion offers the potential for real-time imaging and can be combined with other cross-sectional imaging techniques as well as CEUS.

PERFORMANCE

With the implementation of ultrasound contrast agents and image fusion, ultrasound has been improved in the detection and characterization of liver lesions in comparison to other cross-sectional imaging techniques. In addition, this method can also be used for intervention procedures. The success rate of fusion-guided biopsies or CEUS-guided tumor ablation lies between 80 and 100% in the literature.

ACHIEVEMENTS

Ultrasound-guided image fusion using CT or MRI data, in combination with CEUS, can facilitate diagnosis and therapy follow-up after liver interventions.

PRACTICAL RECOMMENDATIONS

In addition to the primary applications of image fusion in the diagnosis and treatment of liver lesions, further useful indications can be integrated into daily work. These include, for example, intraoperative and vascular applications as well applications in other organ systems.

Comparison of Adrenal Tumor Size in Ultrasound Examinations with and without the Use of a Contrast Agent

Background and objectives: Patients diagnosed with incidentally found adrenal tumors (incidentaloma) that do not meet the criteria for surgical treatment require follow-ups with repeated imaging. The aim of this study is to compare the accuracy of the measurements of the adrenal tumor size in ultrasound (US) with and without contrast in comparison to computed tomography (CT) or magnetic resonance (MRI). Further, this study attempts to answer the question of whether contrast-enhanced ultrasound (CEUS) can improve imaging accuracy and replace CT/MRI in the monitoring of patients with adrenal tumors. Materials and Methods: The retrospective analysis included 79 adult patients with adrenal incidentalomas not exceeding a dimension of 6 cm who underwent a CT or MRI scan, US, and CEUS with the use of SonoVue in two-dimensional (2D) and three-dimensional (3D) projections and Doppler techniques. Tumor vascularization in CEUS was classified as follows: peripheral, peripheral-central, central, or poor. Results: Of 79 adrenal tumors, 48.1% showed peripheral, 29.1% showed poor, 21.5% showed peripheral-central, and only 1.3% showed central vascularization. The median volume of tumors detected with CEUS (69.9 cm³) was significantly higher than with US (44.5 cm³) and CT or MRI (57.1 cm³). The relative error of the adrenal volume with CEUS compared with CT or MRI was significantly higher than with standard US, regardless of the type of tumor vascularization. Conclusions: CEUS does not improve the accuracy of adrenal tumor size assessment regardless of the type of vascularization.

Guided Punctures with Ultrasound Volume Navigation in Percutaneous Transforaminal Endoscopic Discectomy: A Technical Note

OBJECTIVE

Ultrasound volume navigation (UVN) has been widely used for accurate guidance and decreased radiation exposure. However, few studies have focused on the clinical significance of UVN in guiding percutaneous puncture in percutaneous transforaminal endoscopic discectomy (PTED). We evaluated UVN to guide percutaneous puncture in PTED.

METHODS

We retrospectively reviewed the medical records of 12 patients (8 men and 4 women), who had undergone PTED with the help of UVN or fluoroscopic guidance for lumbar disc herniation from November 2017 to December 2017.

RESULTS

The age of these 12 patients range was 26-71 years, and the body mass index range was 18.19-26.91 kg/m². Of the 12 patients, 6 were in UVN group and 6 were in fluoroscopy group. The mean number of punctures was 1.00 in UVN group and 3.83 in fluoroscopy group. The mean exposure time was 3.60 and 13.80 seconds in UVN and fluoroscopy groups, respectively. The mean operation time was 48.17 minutes and 61.33 minutes in UVN and fluoroscopy groups, respectively. A positive relationship was found between operation time and exposure time (P < 0.05). All patients achieved excellent or good clinical outcomes. The Oswestry Disability Index and visual analog scales for leg pain and back pain all showed significant improvement after the procedure (P < 0.05). None of patients experienced a complication.

CONCLUSIONS

UVN decreased the number of puncture attempts, radiation exposure, and operation time compared with fluoroscopic guidance in PTED. Therefore, UVN is a feasible and efficient method for guiding percutaneous puncture in PTED.

Integration of Contrast-enhanced US into a Multimodality Approach to Imaging of Nodules in a Cirrhotic Liver: How I Do It

Accurate characterization of cirrhotic nodules and early diagnosis of hepatocellular carcinoma (HCC) are of vital importance. Currently, computed tomography (CT) and magnetic resonance (MR) imaging are standard modalities for the investigation of new nodules found at surveillance ultrasonography (US). This article describes the successful integration of contrast material-enhanced US into a multimodality approach for diagnosis of HCC and its benefits in this population. The application of contrast-enhanced US immediately following surveillance US allows for prompt dynamic contrast-enhanced evaluation, removing the need for further imaging of benign lesions. Contrast-enhanced US also provides dynamic real-time assessment of tumor vascularity so that contrast enhancement can be identified regardless of its timing or duration, allowing for detection of arterial hypervascularity and portal venous washout. The purely intravascular nature of US contrast agents is valuable as the rapid washout of nonhepatocyte malignancies is highly contributory to their differentiation from HCC. The authors believe contrast-enhanced US provides complementary information to CT and MR imaging in the characterization of nodules in high-risk patients. ^© RSNA, 2017 Online supplemental material is available for this article.

MRI and contrast enhanced ultrasound (CEUS) image fusion of renal lesions

Ultrasound is a common and established imaging method for the initial characterization of renal lesions. The widespread used Bosniak classification (I-IV) classifies renal lesions in five individual groups using contrast-enhanced computer tomography (CE-CT), magnetic resonance imaging (MRI) and/or contrast-enhanced ultrasound (CEUS) imaging criteria. For complex pathologies, CEUS/MRI image fusion is a novel imaging technique for the differentiation of benign and malignant renal lesions. Compared to CE-CT and MRI alone, ultrasound image fusion offers the additional possibility of being a real-time imaging technique that can be used together with other cross-sectional imaging techniques.This article describes the newest possibilities of image fusion with CEUS and MRI in detection and characterization of unclear renal lesions.

Enhancing the role of paediatric ultrasound with microbubbles: a review of intravenous applications

Contrast-enhanced ultrasound (CEUS) represents a complementary technique to greyscale and colour Doppler ultrasonography which allows for real-time visualization and characterization of tissue perfusion. Its inherent advantages in the child makes ultrasonography an ideal imaging modality; repeatability and good tolerance along with the avoidance of CT, a source of ionizing radiation, renders ultrasonography imaging desirable. Although currently paediatric CEUS is principally used in an "off-label" manner, ultrasonography contrast agents have received regulatory approval for assessment of paediatric focal liver lesions (FLL) in the USA. The safety of ultrasound contrast-agents is well documented in adults, as safe as or even surpassing the safety profile of CT and MR contrast agents. Except for the established intracavitary use of CEUS in voiding urosonography, i.v. paediatric applications have been introduced with promising results in the abdominal trauma initial diagnosis and follow-up, characterization and differential diagnosis of FLL and characterization of lung, pleura, renal and splenic pathology. CEUS has also been used to detect complications after paediatric transplantation, evaluate inflammatory bowel disease activity and assess tumour response to antiangiogenic therapy. The purpose of this review was to present these novel i.v. paediatric applications of CEUS and discuss their value.

[Possibilities of sonographic image fusion: Current developments]

CLINICAL/METHODICAL ISSUE

For diagnostic and interventional procedures ultrasound (US) image fusion can be used as a complementary imaging technique.

METHODICAL INNOVATIONS

Image fusion has the advantage of real time imaging and can be combined with other cross-sectional imaging techniques.

PERFORMANCE

With the introduction of US contrast agents sonography and image fusion have gained more importance in the detection and characterization of liver lesions.

ACHIEVEMENTS

Fusion of US images with computed tomography (CT) or magnetic resonance imaging (MRI) facilitates the diagnostics and postinterventional therapy control.

PRACTICAL RECOMMENDATIONS

In addition to the primary application of image fusion in the diagnosis and treatment of liver lesions, there are more useful indications for contrast-enhanced US (CEUS) in routine clinical diagnostic procedures, such as intraoperative US (IOUS), vascular imaging and diagnostics of other organs, such as the kidneys and prostate gland.

Evaluation of the diagnostic accuracy of CEUS in children with benign and malignant liver lesions and portal vein anomalies

OBJECTIVE

Comparison of the diagnostic findings of MRI, CT and CEUS in children with benign and malignant and portal venous anomalies of the liver.

MATERIALS/METHODS

Retrospective analysis of the diagnostic findings of CEUS, MRI and CT scans in 56 children (age 0-17 years) with a total of 60 benign and malignant liver lesions and anomalies of the portal vein/perfusion. All patients underwent CEUS using sulphur hexafluoride microbubbles and a multi-frequency probe (1-5 MHz, 6-9 MHz). Cine-loops were stored up to 3 minutes. MRI was performed in 38 lesions. CT was performed in 8 lesions.

RESULTS

Out of the 56 patients 49 liver lesions (48 benign, 1 malignant), 9 anomalies of the portal vein/perfusion and 2 of the biliary system were detected. 16/49 lesions were analyzed histopathologically. Using CEUS, the characterization of the lesions was possible in 45 out of 49 cases. In 32 cases, CEUS provided the exact diagnosis. Only two benign lesions were falsely categorized as malignant.Findings of MRI and CEUS were concordant in 84% of cases (n = 32/38). CEUS considered 1 benign lesion to be malignant. 2 lesions were not detectable and in 3 lesions no definite diagnosis was established using MRI.Findings of CT and CEUS were concordant in 5 of 8 cases. In 21 lesions CEUS as the only imaging modality was found to be sufficient for diagnostics.

CONCLUSION

Despite the restricted indications for using CEUS in children, it offers a high diagnostic detection rate (93%) for characterization of liver lesions and portal vein anomalies.

The fluoro-less and contrast-less peripheral endovascular intervention: Halfway there

INTRODUCTION

Percutaneous endovascular revascularization requires the use of fluoroscopic guidance and radiopaque contrast. We present a successful intervention without the use of iodinated contrast.

CASE

A 92-year-old man with dry gangrene involving the second and fourth left toes had acute on chronic kidney injury. Arterial duplex showed severe stenosis in bilateral superficial femoral arteries (SFAs). Fluoroscopic and ultrasound guidance and intravascular imaging were used to avoid iodinated contrast. After right to left femoral crossover, the entire left SFA was imaged with ultrasound. The lesion was delineated with radiopaque measuring tapes then wired. Near-infrared spectroscopy and intravascular ultrasound (NIRS-IVUS) imaging were performed. Points of interest were correlated with corresponding radiopaque markings on the ruler. Stenting and post-dilation resulted in complete stent expansion and no evidence of dissection by IVUS. The total procedure time was 113min and the total radiation dose 813mGy. The day after the procedure, there was a palpable dorsalis pedis pulse. He was discharged to inpatient rehabilitation on dual antiplatelet therapy.

DISCUSSION

Contrast and radiation continue to limit the feasibility of endovascular angiography and intervention. Carbon dioxide (CO2) digital subtraction angiography is an alternative for these patients but has several disadvantages. Previously proposed projects demonstrated the real potential of performing endovascular peripheral intervention without fluoroscopy or contrast.

CONCLUSION

This case is a clear demonstration of a successful use of a combination of fluoroscopy, ultrasonography and intravascular imaging to achieve a successful endovascular intervention to treat critical limb ischemia, without the use of iodinated contrast.

White Paper on P4 Concepts for Pediatric Imaging

Over the past decade, innovations in the field of pediatric imaging have been based largely on single-center and retrospective studies, which provided limited advances for the benefit of pediatric patients. To identify opportunities for potential "quantum-leap" progress in the field of pediatric imaging, the ACR-Pediatric Imaging Research (PIR) Committee has identified high-impact research directions related to the P4 concept of predictive, preventive, personalized, and participatory diagnosis and intervention. Input from 237 members of the Society for Pediatric Radiology was clustered around 10 priority areas, which are discussed in this article. Needs within each priority area have been analyzed in detail by ACR-PIR experts on these topics. By facilitating work in these priority areas, we hope to revolutionize the care of children by shifting our efforts from unilateral reaction to clinical symptoms, to interactive maintenance of child health.

Application of imaging fusion combining contrast-enhanced ultrasound and magnetic resonance imaging in detection of hepatic cellular carcinomas undetectable by conventional ultrasound

BACKGROUND AND AIM

The aim of this study is to explore the value of volume navigation image fusion-assisted contrast-enhanced ultrasound (CEUS) in detection for radiofrequency ablation guidance of hepatocellular carcinomas (HCCs), which were undetectable on conventional ultrasound.

METHODS

From May 2012 to May 2014, 41 patients with 49 HCCs were included in this study. All lesions were detected by dynamic magnetic resonance imaging (MRI) and planned for radiofrequency ablation but were undetectable on conventional ultrasound. After a bolus injection of 2.4 ml SonoVue® (Bracco, Italy), LOGIQ E9 ultrasound system with volume navigation system (version R1.0.5, GE Healthcare, Milwaukee, WI, USA) was used to fuse CEUS and MRI images. The fusion time, fusion success rate, lesion enhancement pattern, and detection rate were analyzed.

RESULTS

Image fusions were conducted successfully in 49 HCCs, the technical success rate was 100%. The average fusion time was (9.2 ± 2.1) min (6-12 min). The mean diameter of HCCs was 25.2 ± 5.3 mm (mean ± SD), and mean depth was 41.8 ± 17.2 mm. The detection rate of HCCs using CEUS/MRI imaging fusion (95.9%, 47/49) was significantly higher than CEUS (42.9%, 21/49) (P < 0.05). For small HCCs (diameter, 1-2 cm), the detection rate using imaging fusion (96.9%, 32/33) was also significantly higher than CEUS (18.2%, 6/33) (P < 0.01). All HCCs displayed a rapid wash-in pattern in the arterial phase of CEUS.

CONCLUSIONS

Imaging fusion combining CEUS and MRI is a promising technique to improve the detection, precise localization, and accurate diagnosis of undetectable HCCs on conventional ultrasound, especially small and atypical HCCs.

Off-Label Use of Ultrasound Contrast Agents for Intravenous Applications in Children: Analysis of the Existing Literature

OBJECTIVES

The purpose of this study was to collect and analyze the published data related to intravenous (IV) use of ultrasound (US) contrast agents in children.

METHODS

We searched the literature to collect all of the published studies reporting the IV administration of a second-generation US contrast agent in children.

RESULTS

We analyzed 9 case series and 5 case reports, as well as 5 individual cases, of pediatric contrast-enhanced US use reported in a study group that also included adults. We found that 502 children underwent contrast-enhanced US examinations (mean age, 9.7 years; range, 1 day-18 years). Most patients (89%) were injected with the sulfur hexafluoride contrast agent SonoVue (Bracco SpA, Milan, Italy). The mean dose used was 1.5 mL (range, 0.1-9.6 mL). Only 10 patients (2%) had adverse reactions related to the contrast agent administration: 1 life-threatening anaphylactic shock and 9 mild transitory adverse effects. We additionally found 38 papers in which the study groups included at least 1 child; thus, we obtained a total of 540 reported cases of off-label use of IV US contrast agents in children. The most frequent target organ was the liver, and most indications were related to space-occupying lesion characterization and abdominal evaluations after blunt trauma. Some studies also evaluated the diagnostic performance of contrast-enhanced US in different clinical scenarios and found very good accuracy. Concordance between contrast-enhanced US imaging and the respective reference-standard imaging methods ranged between 83% and 100% in different studies.

CONCLUSIONS

Our results support the idea that the IV use of US contrast agents in children is safe, feasible, diagnostically robust, and effective.

Predictive value of quantitative contrast-enhanced ultrasound in hepatocellular carcinoma recurrence after ablation

AIM: To investigate the relationship between contrast-enhanced ultrasound (CEUS), basic fibroblast growth factor (bFGF), endothelin-1 (ET-1), and hepatocellular carcinoma (HCC) recurrence after ablation.

METHODS: A total of 51 HCC patients (38 males and 13 females) who received radiofrequency ablation in our hospital from June 2012 to July 2014 were enrolled in this study. The patients were divided into two groups: recurrence group and non-recurrence group. Routine abdominal examination was first performed in the horizontal position. Then the patients underwent CEUS and immunohistochemical staining before receiving radiofrequency ablation. All patients were followed-up every three months for one year. The results of CEUS and serum tumor marker levels were evaluated and combined together to estimate HCC recurrence and metastasis. Patients were divided into two groups: recurrence group and non-recurrence group. Quantitative parameters of CEUS and tumor expression levels of bFGF and ET-1 were compared between the two groups, respectively. Binary logistic regression analysis was used to analyze the relationship between CEUS quantitative parameters, expression levels of ET-1 and bFGF, and HCC recurrence after ablation.

RESULTS: Based on the quantitative parameters of CEUS before patients received radiofrequency ablation, the levels of tumor rise time (tRT), tumor time to peak (tTTP), tumor peak intensity (tPI) and tumor-parenchymal peak intensity (t-pPI) in the recurrence group were significantly lower than those in the non-recurrence group (16.6 ± 6.1 vs 23.2 ± 7.0, P = 0.000; 41.2 ± 10.2 vs 59.6 ± 14.2, P = 0.000; 23.8 ± 6.7 vs 31.4 ± 6.4, P = 0.000; 7.1 ± 3.4 vs 14.6 ± 7.4, P = 0.000; respectively). The expression levels of bFGF in the recurrence group were significantly higher than those in the non-recurrence group (P < 0.05). Levels of tTTP showed a significant inverse correlation with the level of bFGF in tumors (r = -0.312, P = 0.037). The Binary logistic regression analysis results revealed that the levels of tRT, tTTP, tPI and the level of bFGF were associated with HCC recurrence after radiofrequency ablation (P < 0.05).

CONCLUSION: CEUS is a noninvasive and effective method for evaluating the angiogenesis of HCC, and predicting its recurrence and prognosis.

Fusion imaging for evaluation of deep infiltrating endometriosis: feasibility and preliminary results

OBJECTIVE

Magnetic resonance imaging (MRI) and ultrasound scanning complement each other in screening for and diagnosis of endometriosis. Fusion imaging, also known as real-time virtual sonography, is a new technique that uses magnetic navigation and computer software for the synchronized display of real-time ultrasound and multiplanar reconstructed MR images. Our aim was to evaluate the feasibility and ability of fusion imaging to assess the main anatomical sites of deep infiltrating endometriosis (DIE) in patients with suspected active endometriosis.

METHODS

This prospective study was conducted over a 1-month period in patients referred to a trained radiologist for an ultrasound-based evaluation for endometriosis. Patients with a prior pelvic MRI examination within the past year were offered fusion imaging, in addition to the standard evaluation. All MRI examinations were performed on a 1.5-T MRI machine equipped with a body phased-array coil. The MRI protocol included acquisition of at least two fast spin-echo T2-weighted orthogonal planes. The Digital Imaging Communications in Medicine dataset acquired at the time of the MRI examination was loaded into the fusion system and displayed together with the ultrasound image on the same monitor. The sets of images were then synchronized manually using one plane and one anatomical reference point. The ability of this combined image to identify and assess the main anatomical sites of pelvic endometriosis (uterosacral ligaments, posterior vaginal fornix, rectum, ureters and bladder) was evaluated and compared with that of standard B-mode ultrasound and MRI.

RESULTS

Over the study period, 100 patients were referred for ultrasound examination because of endometriosis. Among them were 20 patients (median age, 35 (range, 27-49) years) who had undergone MRI examination within the past year, with a median (range) time interval between MRI and ultrasound examination of 171 (1-350) days. All 20 patients consented to undergo additional evaluation by fusion imaging. However, in three (15%) cases, fusion imaging was not technically possible because of changes since the initial MRI examination resulting from either interval surgery (n = 2; 10%) or pregnancy (n = 1; 5%). Data acquisition, matching and fusion imaging were performed in under 10 min in each of the other 17 cases. The overall ability of each technique to identify and assess the main anatomical landmarks of endometriosis was as follows: uterosacral ligaments: ultrasound, 88% (30/34); MRI, 100% (34/34); fusion imaging, 100% (34/34); posterior vaginal fornix: ultrasound, 88% (30/34); MRI, 100% (34/34); fusion imaging, 100% (34/34); rectum: ultrasound, 100% (17/17); MRI, 82.3% (14/17); fusion imaging, 100% (17/17); ureters: ultrasound, 0%; MRI, 100% (34/34); fusion imaging, 100% (34/34); and bladder: ultrasound, 100%; MRI, 100%; fusion imaging, 100%.

CONCLUSION

Fusion imaging is feasible for the assessment of endometriotic lesions. Because it combines information from both ultrasound and MRI techniques, fusion imaging allows better identification of the main anatomical sites of DIE and has the potential to improve the performance of ultrasound and MRI examination.

Viable hepatocellular carcinoma around retained iodized oil after transarterial chemoembolization: radiofrequency ablation of viable tumor plus retained iodized oil versus viable tumor alone

OBJECTIVE

The objective of our study was to compare the effectiveness of radiofrequency ablation (RFA) for viable hepatocellular carcinoma (HCC) including areas of retained oil after transarterial chemoembolization (TACE) versus RFA treatment of viable HCC alone for ablation coverage.

MATERIALS AND METHODS

Eighty-five patients with 88 viable HCCs underwent RFA of residual viable HCCs around retained iodized oil after TACE. RFA of both viable HCC and retained iodized oil was performed on 47 viable tumors (group A), and RFA of viable HCC only was used to treat the remaining 41 viable tumors (group B).

RESULTS

After initial RFA, the endpoint of ablation was successfully achieved for 45 of 47 tumors in group A and for all 41 tumors in group B. Two residual viable tumors in group A were successfully treated by additional RFA. Major complications occurred after initial RFA treatment of one tumor each in group A (pleural effusion) and group B (collateral damage). During follow-up (mean, 37.1 months; range, 5-116.5 months), local tumor progression of treated lesions was found in 28% in group A and 59% in group B. The respective 1-, 3-, 5-, and 7-year local tumor progression rates were significantly lower in group A (15%, 32%, 32%, and 32%) than in group B (43%, 71%, 81%, and 81%) (p = 0.001).

CONCLUSION

In treatment of viable tumors after TACE in patients with HCC, RFA of both viable tumor and retained iodized oil may reduce rates of local tumor progression compared with RFA of viable tumor only.

Real-time image fusion for successful percutaneous radiofrequency ablation of hepatocellular carcinoma

Percutaneous radiofrequency ablation (RFA) is an established nonsurgical curative treatment for hepatocellular carcinoma (HCC). Because of its efficiency and safety, sonography is the most commonly used imaging modality when performing RFA. However, the presence of HCC nodules that are inconspicuous when using conventional sonography is a major drawback of RFA and limits its feasibility as a treatment for HCC. However, a new technology has been developed that synthesizes high-resolution multiplanar reconstruction images using 3-dimensional data and is combined with a position-tracking system using magnetic navigation. With this technology, real-time sonograms can be fused with corresponding computed tomographic, magnetic resonance imaging, or even sonographic volume data; this process is known as real-time image fusion. In this article, we describe this novel imaging method as a useful tool for successful RFA treatment of HCC.

Development of a hybrid magnetic resonance and ultrasound imaging system

A system which allows magnetic resonance (MR) and ultrasound (US) image data to be acquired simultaneously has been developed. B-mode and Doppler US were performed inside the bore of a clinical 1.5 T MRI scanner using a clinical 1-4 MHz US transducer with an 8-metre cable. Susceptibility artefacts and RF noise were introduced into MR images by the US imaging system. RF noise was minimised by using aluminium foil to shield the transducer. A study of MR and B-mode US image signal-to-noise ratio (SNR) as a function of transducer-phantom separation was performed using a gel phantom. This revealed that a 4 cm separation between the phantom surface and the transducer was sufficient to minimise the effect of the susceptibility artefact in MR images. MR-US imaging was demonstrated in vivo with the aid of a 2 mm VeroWhite 3D-printed spherical target placed over the thigh muscle of a rat. The target allowed single-point registration of MR and US images in the axial plane to be performed. The system was subsequently demonstrated as a tool for the targeting and visualisation of high intensity focused ultrasound exposure in the rat thigh muscle.

Real-time ultrasound and freehand-SPECT. Experiences with sentinel lymph node mapping

Aim of this work is to report first experiences of the feasibility and applicability of a hybrid freehandSPECT/ultrasound (fh-SPECT/US) imaging concept, with regard to SLN imaging, in patients with breast cancer and malignant melanoma.

PATIENTS, METHODS

18 patients with breast cancer or malignant melanoma received standard SLN scintigraphy. Following this, fh-SPECT using declipse®SPECT (SurgicEye, Munich, Germany) was performed, a handheld-gamma camera-based method to visualize activity distribution within a region of interest as a cross-sectional data set. These data were transferred to an ultrasound device and sensor-navigated ultrasound was performed combining fh-SPECT data with ultrasound images, displaying superimposed images. Quality of fh-SPECT and co-registration accuracy was assigned to one of four categories and occurrence of artefacts was assessed.

RESULTS

In 4/18 examinations, there was a no deviation regarding co-registration of both data sets. For 9/18 patients, there was a deviation of <1 cm (mean 0.7±0.3 cm, range 0.3-1.0 cm). For 3/18 patients, a deviation >1 cm was present (mean 1.7±0.3 cm, range 1.5-2.0 cm). In 2/18 examinations no lymph node was found in the region of highest activity. Fh-SPECT reconstruction artifacts occurred in 6/18 examinations.

CONCLUSION

The fusion imaging concept combining SLN information with ultrasound images presented here proves to be feasible and technically successful. However, significant technical limitations were shown in fh-SPECT quality and fusion precision. Subject to technical optimisation of SPECT quality and co-registration, a meaningful contribution to the preoperative planning of lymph node therapy is imaginable. Thus, fundamentally a preoperative histological examination by fh-SPECT/US-guided biopsy is possible.

Hybrid integration of real-time US and freehand SPECT: proof of concept in patients with thyroid diseases

PURPOSE

To report an initial experience regarding the feasibility and applicability of quasi-integrated freehand single photon emission computed tomography (SPECT)/ultrasonography (US) fusion imaging in patients with thyroid disease.

MATERIALS AND METHODS

Local ethics committee approval was obtained, and 34 patients were examined after giving written informed consent. After intravenous application of 75 MBq of technetium 99m pertechnetate, freehand three-dimensional SPECT was performed. Data were reconstructed and transferred to a US system. The combination of two independent positioning systems enabled real-time fusion of metabolic and morphologic information during US examination. Quality of automatic coregistration was evaluated visually, and deviation was determined by measuring the distance between the center of tracer distribution and the center of the US correlate.

RESULTS

All examinations were technically successful. For 18 of 34 examinations, the automatic coregistration and image fusion exhibited very good agreement, with no deviation. Only minor limitations in fusion offset occurred in 16 patients (mean offset ± standard deviation, 0.67 cm ± 0.3; range, 0.2-1.0 cm). SPECT artifacts occurred even in situations of clear thyroid findings (eg, unifocal autonomy).

CONCLUSION

The freehand SPECT/US fusion concept proved feasible and applicable; however, technical improvements are necessary.

MRI and ultrasound fusion imaging for prenatal diagnosis

OBJECTIVE

A combination of magnetic resonance imaging (MRI) images with real time high-resolution ultrasound known as fusion imaging may improve prenatal examination. This study was undertaken to evaluate the feasibility of using fusion of MRI and ultrasound (US) in prenatal imaging.

STUDY DESIGN

This study was conducted in a tertiary referral center. All patients referred for prenatal MRI were offered to undergo fusion of MRI and US examination. All cases underwent 1.5 Tesla MRI protocol including at least 3 T2-weighted planes. The Digital Imaging and Communications in Medicine volume dataset was then loaded into the US system for manual registration of the live US image and fusion imaging examination.

RESULTS

Over the study period, 24 patients underwent fusion imaging at a median gestational age of 31 (range, 24-35) weeks. Data registration, matching and then volume navigation was feasible in all cases. Fusion imaging allowed superimposing MRI and US images therefore providing with real time imaging capabilities and high tissue contrast. It also allowed adding a real time Doppler signal on MRI images. Significant fetal movement required repeat-registration in 15 (60%) cases. The average duration of the overall additional scan with fusion imaging was 10 ± 5 minutes.

CONCLUSION

The combination of fetal real time MRI and US image fusion and navigation is feasible. Multimodality fusion imaging may enable easier and more extensive prenatal diagnosis.

Real-time image fusion involving diagnostic ultrasound

OBJECTIVE

The aim of our article is to give an overview of the current and future possibilities of real-time image fusion involving ultrasound. We present a review of the existing English-language peer-reviewed literature assessing this technique, which covers technical solutions (for ultrasound and endoscopic ultrasound), image fusion in several anatomic regions, and electromagnetic needle tracking.

CONCLUSION

The recent progress of real-time ultrasound in image fusion may provide several new possibilities, including diagnosis, treatment, and follow-up of oncologic patients.