Quantitative assessment of solid renal masses by contrast-enhanced ultrasound with time-intensity curves: how we do it

Contrast-Enhanced Ultrasound in the Diagnosis of Solid Renal Lesions

The availability of imaging methods has enabled increased detection of kidney lesions, which are a common clinical problem. It is estimated that more than half of patients over the age of 50 have at least one undetermined mass in the kidney. The appropriate characterization and diagnosis of lesions imaged in the kidney allows for proper therapeutic management. Previously, contrast-enhanced computed tomography (CT) and contrast-enhanced magnetic resonance imaging (MRI) have been used in their extended diagnosis. However, the limitations of these techniques, such as radiation exposure, renal toxicity, and allergies to contrast agents, must be considered. Contrast-enhanced ultrasound (CEUS) is increasingly being used as an examination to resolve interpretive doubts that arise with other diagnostic methods. Indeed, it can be considered both as a problem-solving technique for diagnosing and distinguishing lesions and as a technique used for observation in preservative treatment. Evaluation of the enhancement curve over time on CEUS examination can help to differentiate malignant renal cell carcinoma (RCC) subtypes that should be resected from benign lesions, such as oncocytoma or angiomyolipoma (AML), in which surgery can be avoided. It allows for distinguishing between benign and malignant tumors, renal and pseudotumors, and solid and cystic tumors. Therefore, with recent advances in ultrasound technology, CEUS has emerged as a fast, reliable, and cost-effective imaging tool in the preoperative evaluation and diagnosis of solid renal masses.

The Role of Endoscopic Ultrasound and Ancillary Techniques in the Diagnosis of Autoimmune Pancreatitis: A Comprehensive Review

Autoimmune pancreatitis (AIP) is a unique form of chronic pancreatitis with a multifactorial pathogenesis. Historically, it has been classified as type 1 and type 2, according to its clinical and histological features. The diagnosis of AIP is challenging and relies on a combination of clinical, histopathologic, serologic, and imaging characteristics. In the available guidelines, the imaging hallmarks of AIP are based on cross-sectional imaging and cholangiopancreatography retrograde endoscopic findings. Endoscopic ultrasound (EUS) is generally used for pancreatic tissue acquisition to rule out pancreatic cancer and diagnose AIP with limited accuracy. Several papers reported the reliability of EUS for providing informative morphologic features of AIP. Nowadays, the improvement in the resolution of EUS conventional images and the development of new ancillary technologies have further increased the diagnostic yield of EUS: contrast-enhanced EUS and EUS elastography are non-invasive and real-time techniques that strongly support the diagnosis and management of pancreatic diseases. In this review article, we will present the role of conventional EUS and ancillary diagnostic techniques in the diagnosis of AIP to support clinicians and endosonographers in managing this condition.

Associations between contrast-enhanced ultrasound features and WHO/ISUP grade of clear cell renal cell carcinoma: a retrospective study

BACKGROUND

Clear cell renal cell carcinoma (CCRCC) comprises 70%-80% of RCCs. The World Health Organization/International Society of Urology Pathology (WHO/ISUP) classification is the most important prognostic factor for CCRCC. By evaluating the variations of tumor microvascular density, contrast-enhanced ultrasound (CEUS) can noninvasively predict the WHO/ISUP grade of CCRCC, and provide the appropriate treatment plan before clinical operation.

METHODS

In this study, we used CEUS features to analyze 116 CCRCC cases and assess the value of correlation between each indicator and CCRCC WHO/ISUP grading.

RESULTS

When compared to high-grade (WHO/ISUP grade III/IV) tumors, low-grade (WHO/ISUP grade I/II) tumors had reduced relative peak intensity (ΔPI) (P = 0.021), relative area under the curve (ΔAUC) (P = 0.019). However, the frequency of incomplete pseudocapsule (P = 0.021) was significantly higher in high-grade tumors. A cut-off value of mean diameter > 5.5 cm, ΔPI > 304 × 10-3, ΔAUC > 350 × 10-3 allowed identification of high-grade tumors with an area under the curve (AUC) of 74.6%, 71.7%, 70.7%, respectively (95% confidence interval).

CONCLUSIONS

The features of CEUS are effective for differentiating high-grade tumors from low-grade tumors, thus CEUS can be considered an acceptable method for the preoperative assessment of tumor grade.

Radiologist's Disease: Imaging for Renal Cancer

There is a clear benefit of imaging-based differentiation of small indeterminate masses to its subtypes of clear cell renal cell carcinoma (RCC), chromophobe RCC, papillary RCC, fat poor angiomyolipoma and oncocytoma because it helps determine the next step options for the patients. The work thus far in radiology has explored different parameters in computed tomography, MRI, and contrast-enhanced ultrasound with the discovery of many reliable imaging features that suggest certain tissue subtypes. Likert score-based risk stratification systems can help determine management, and new techniques such as perfusion, radiogenomics, single-photon emission tomography, and artificial intelligence can add to the imaging-based evaluation of indeterminate renal masses.

The Changing Role of Renal Mass Biopsy

The incidence and prevalence of small renal masses (SRMs) continues to rise and with increased detection comes increases in surgical management, although the probability of an SRM being benign is upward of 30%. An extirpative treatment first diagnose-later strategy persists and clinical tools for risk stratification such as renal mass biopsy remain severely underutilized. The overtreatment of SRMs has multiple detrimental effects including surgical complications, psychosocial stress, financial loss, and reduced renal function leading to downstream effects such as the need for dialysis and cardiovascular disease.

Contrast Enhanced EUS for Predicting Solid Pancreatic Neuroendocrine Tumor Grade and Aggressiveness

Pancreatic neuroendocrine tumor (PNET) behavior assessment is a daily challenge for physicians. Modern PNET management varies from a watch-and-wait strategy to surgery depending on tumor aggressiveness. Therefore, the aggressiveness definition plays a pivotal role in the PNET work-up. The aggressiveness of PNETs is mainly based on the dimensions and histological grading, with sometimes a lack of specificity and sensibility. In the last twenty years, EUS has become a cornerstone in the diagnostic phase of PNET management for its high diagnostic yield and the possibility of obtaining a histological specimen. The number of EUS applications in the PNET work-up has been rapidly increasing with new and powerful possibilities. The application of contrast has led to an important step in PNET detection; in recent years, it has been gaining interesting applications in aggressiveness assessment. In this review, we underline the latest experiences and opportunities in the behavior assessment of PNETs using contact-enhanced EUS and contested enhanced harmonic EUS with a particular focus on the future application and possibility that these techniques could provide.

The Value of Contrast-Enhanced Ultrasound in Diagnosing Small Renal Cell Carcinoma Subtypes and Angiomyolipoma

OBJECTIVES

To retrospectively explore the value of contrast-enhanced ultrasound (CEUS) in differentiating small renal cell carcinomas (RCCs) from angiomyolipomas (AMLs), and distinguishing between clear cell RCC (ccRCC), papillary RCC (pRCC), and chromophobe RCC (chRCC).

METHODS

A total of 151 patients with small renal masses (110 ccRCCs, 12 pRCCs, 9 chRCCs, and 20 AMLs) were enrolled between August 2016 and October 2019.

RESULTS

There were significant differences in terms of enhancement intensity (EI), enhancement homogeneity, perilesional rim-like enhancement (PRE), wash in, and wash out (WO) between RCC and AML (P = .000, .011, .000, .001, .000, respectively). Although there was no significant difference in EI between pRCC and chRCC (P = .272), EI of ccRCC was higher than that of pRCC (P = .000) and chRCC (P = .010). Multivariate regression analysis showed PRE and fast WO were related to RCC (OR = 18.189, 15.141, respectively). Although there were no significant differences in the sensitivity and area under the curve (AUC) between PRE and fast WO (95.0% vs. 95.0%, P = 1.000 and .880 vs. 0.799, P = .123, respectively), the specificity of PRE in predicting RCC was higher than that of fast WO (80.92% vs. 64.89%, P = .011). The sensitivity, specificity, and AUC of the two characteristics combination for differentiating RCC from AML were 95.0%, 90.8%, and 0.920, respectively, and that of EI for differentiating between ccRCC, pRCC, and chRCC were 81.0%, 78.2%, and 0.796, respectively.

CONCLUSIONS

CEUS has value in differentiating small RCCs from AMLs and distinguishing ccRCC, a subtype associated with a greater likelihood of malignant behavior from pRCC and chRCC.

Associations between tumor grade, contrast-enhanced ultrasound features, and microvascular density in patients with clear cell renal cell carcinoma: a retrospective study

BACKGROUND

Clear cell renal cell carcinoma (ccRCC) comprises 70% of all renal cell carcinomas (RCCs). Currently, the most important prognostic factor for this type of carcinoma is the World Health Organization/International Society of Urological Pathology (WHO/ISUP) grade. However, nonsurgical methods are rarely used to determine a tumor's WHO/ISUP grade, thus limiting the development of nonsurgical therapies. Due to variations in microvascular density (MVD) at different stages of tumor growth, contrast-enhanced ultrasound (CEUS) features may provide a noninvasive method for evaluating the WHO/ISUP grade of ccRCC.

METHODS

In this study, we analyzed confirmed cases of ccRCC using CEUS features. We also used CD34 and CD31 antibodies to determine MVD. The heterogeneity of CD34 and CD31 expressions were used to determine different degrees of angiogenesis.

RESULTS

When compared to WHO/ISUP grade I/II (G1/G2) tumors, grade III/IV (G3/G4) tumors had reduced peak intensity (PI) (P=0.006), time to peak (TTP) (P<0.001), and relative enhancement percentage index (∆PI%) (P<0.001). However, the frequency of incomplete pseudocapsule (P=0.049) and slow wash-in (P=0.001) was significantly higher in G3/G4 tumors. A cut-off value of ∆PI% <33.15% (P<0.001) allowed identification of G3/G4 tumors with an area under the curve (AUC) of 0.80 [95% confidence interval (CI): 0.70 to 0.91) and a sensitivity of 80%. The mean CD34+ MVD (P<0.001) and CD31+ MVD (P<0.001) were significantly lower in G3/G4 tumors. A positive correlation was revealed between ∆PI% and MVD. There was a statistically significant difference in the density of undifferentiated vessels between the slow wash-in and fast wash-in cases (P<0.001).

CONCLUSIONS

The features of CEUS are effective for differentiating G3/G4 tumors from G1/G2. There was a positive correlation detected between ∆PI% and MVD, and the density of undifferentiated vessels showed a significant difference between slow wash-in and fast wash-in cases. These findings indicate that CEUS can enable the sonographic visualization of tumor angiogenesis and thus be considered an acceptable method for the nonsurgical assessment of tumor microvascular distribution and grade.

Predictive value of contrast-enhanced ultrasound combined with conventional ultrasound in solid renal parenchymal lesions

OBJECTIVE

This study aimed to develop a model to predict the risk of malignancy in solid renal parenchymal lesions based on the imaging features of combined conventional and contrast-enhanced ultrasound (CEUS).

METHODS

A retrospective review was performed among patients with focal solid renal parenchymal lesions on ultrasound images. Ultrasound features were characterized by two experienced radiologists independently. A multiple logistic regression analysis was performed to determine the most relevant features and to estimate the risk of malignancy. Scoring and counting methods were developed based on the most relevant features. The diagnostic performance was evaluated by the sensitivity, specificity, positive predictive value, negative predictive value and area under the receiver operating characteristic curve (AUC).

RESULTS

A total of 519 renal lesions were included in this study. The conventional ultrasound features of diameter, echogenicity, hypoechoic rim and the CEUS feature of heterogeneity were identified as the most relevant features for prediction of malignancy. The sensitivity and specificity for the logistic regression model, the scoring method and the counting method were 95.3 and 93.4%, 93.8 and 87.8%, 88.8 and 93.9%, respectively. The logistic model had the best performance for diagnosing malignant renal lesions with AUC of 0.978, compared with the scoring method and the counting method with AUCs of 0.958 and 0.965.

CONCLUSION

The combination of contrast-enhanced ultrasound with conventional ultrasound improved the diagnostic performance of solid renal lesions based on the logistic regression model.

ADVANCES IN KNOWLEDGE

In this study, we revealed that the combination of CEUS and conventional ultrasound provided higher accuracy for diagnosing malignant renal tumors.

Chromophobe Renal Cell Carcinoma with Radiologic-Pathologic Correlation

Renal cell carcinoma (RCC) is a heterogeneous group of neoplasms derived from the renal tubular epithelial cells. Chromophobe RCC (chRCC) is the third most common subtype of RCC, accounting for 5% of cases. chRCC may be detected as an incidental finding or less commonly may manifest with clinical symptoms. The mainstay of therapy for chRCC is surgical resection. chRCC has a better prognosis compared with the more common clear cell RCC. At gross pathologic analysis, chRCC is a solid well-defined mass with lobulated borders. Histologic findings vary by subtype but include large pale polygonal cells with abundant transparent cytoplasm, crinkled "raisinoid" nuclei with perinuclear halos, and prominent cell membranes. Pathologic analysis reveals only moderate vascularity. The most common imaging pattern is a predominantly solid renal mass with circumscribed margins and enhancement less than that of the renal cortex. The authors discuss chRCC with emphasis on correlative pathologic findings and illustrate the multimodality imaging appearances of chRCC by using cases from the Radiologic Pathology Archives of the American Institute for Radiologic Pathology. ^©RSNA, 2021.

Controversies in the diagnosis of renal cell carcinoma with tumor thrombus

Diagnosis and treatment of renal cell carcinoma with venous tumor thrombosis remains a challenge today, requiring multidisciplinary teams, mainly in tumor thrombus levels III-IV. Our objective is to present the various diagnostic techniques used and its controversies. A review of the most relevant related articles between January 2000 and August 2020 has been carried out in PubMed, EMBASE and Scielo. Continuous technological development has allowed progress in its detection, in the approximation of the histological subtype, and in the determination of tumor thrombus level. Regardless of the imaging technique used for its diagnosis (CT, MRI, TEE, ultrasound with contrast), the time elapsed until treatment is vitally important to reduce the risk of complications, some of them fatal, such as pulmonary thromboembolism.

The added value of contrast-enhanced ultrasound in evaluation of indeterminate small solid renal masses and risk stratification of cystic renal lesions

OBJECTIVES

To investigate accuracy of contrast-enhanced ultrasound (CEUS) to characterize indeterminate small solid renal masses (sSRMs), excluding lipid-rich AMLs, and cystic renal masses (CRMs) according to the proposed Bosniak Classification 2019 MATERIALS AND METHODS: CEUS of pathology-proven CRMs and sSRMs (without definite enhancement or macroscopic fat on CT/MRI), and CRMs with ≥18 months follow-up were retrospectively reviewed. Two radiologists blindly categorized CRMs according to new Bosniak Classification on CT/MRI. On CEUS, two other radiologists evaluated arterial-phase enhancement of sSRMs relative to renal cortex and categorized CRMs following new Bosniak Classification. Fisher's exact/chi-squared test was used to compare categorical variables, and Cohen κ statistics for inter-observer agreement RESULTS: A total of 237 patients had 241 lesions: 161 pathology-proven sSRMs (122 malignant and 39 benign), 29 pathology-proven CRMs, 51 CRMs with adequate follow-up. Arterial-phase enhancement < renal cortex predicted malignancy with specificity of 97.4% (38/39) (CI 85.6-99.9%), and positive predictive value (PPV) of 98.2% (54/55) (CI 90.4-99.9%). Inter-observer kappa was 0.95. In pathology-proven CRMS, sensitivity of CEUS vs CT/MRI was 100% (15/15) (CI 79.6-100%) vs 60% (9/15) (CI 35.8-80.1%) (p value = .002) and negative predictive value (NPV) 100% (2/2) (CI 17.8-100%) vs 25% (2/8 ) (CI 4.4-59.1%) (p value < 0.0001), with similar specificity (50%) and PPV- 88.2% (15/17) (CI 65.7-97.9%) vs 81.8% (9/11) (CI 52.3-96.8%) ( p value = 0.586). Bosniak Classification inter-observer kappa was 0.92 for CEUS vs 0.68 for CT/MRI (p value = 0.009).

CONCLUSION

In our cohort, CEUS had high specificity and PPV to diagnose RCC in sSRMs excluding lipid-rich AML. CEUS had significantly higher sensitivity/NPV to diagnose malignancy in CRMs as compared to CT/MRI.

KEY POINTS

• Once lipid-rich AML is excluded by the other modalities, sSRM arterial phase hypo-enhancement relative to renal cortex on CEUS yielded high specificity (97.4%) and PPV (98.2%) to diagnose RCC. • When applying the proposed Bosniak Classification 2019, CEUS showed higher sensitivity compared to CT/MRI (100% vs 60%), p value=.0024, in the stratification of cystic renal masses to diagnose malignancy. • CEUS may reduce the number of CT/MRI Bosniak IIF lesions by assigning them to either II or III/IV categories.

A comparative study of contrast-enhanced ultrasound and contrast-enhanced CT for the detection and characterization of renal masses

This study aims to compare the value of contrast-enhanced ultrasound (CEUS) and contrast-enhanced CT (CECT) in the differential diagnosis of benign and malignant renal masses. Included in this retrospective study were 143 renal masses in 141 patients using histopathological findings as the gold standard. A comparison was made of the two modalities in image characteristics for their accuracy in the differential diagnosis of renal masses. CEUS and CECT were both used for 39 masses in 37 patients, with 31 (79.5%) being malignant and 8 (20.5%) benign. The differences between the benign and malignant groups in perfusion intensity, perfusion uniformity and entry and exit of the contrast agent were not statistically significant (P > 0.05). However, CEUS could better display the circular perfusion of renal cell carcinoma than CECT (P < 0.05). CECT alone detected 109 masses in 107 patients, with 93 (85.3%) being malignant and 16 (14.7%) benign. CEUS detected 73 masses in 71 patients, with 56 (76.7%) being malignant and 17 (23.3%) benign. No statistically significant differences were observed between CEUS and CECT in the diagnosis of renal cell carcinoma (92.8% vs. 90.3%), with a specificity of 52.9% vs. 31.2%, an accuracy of 83.5% vs. 81.6%, and a positive predictive value of 86.7% vs. 88.4% or a negative predictive value of 69.2% vs. 35.7% (P > 0.05 for all). These results suggested both CEUS and CECT are highly valuable in the differential diagnosis of renal masses, and CEUS can be used as an important supplement for CECT in diagnosis of renal cancer.

Contrast-Enhanced Ultrasound for the Evaluation of Renal Transplants

Contrast-enhanced ultrasound has emerged as a useful imaging modality for the evaluation of the transplant kidney. Advantages over traditional imaging modalities such as computed tomography and magnetic resonance imaging include the ability to visualize a lesion's enhancement pattern in real time, the lack of nephrotoxicity, and relatively low cost. Potential uses of contrast-enhanced ultrasound include characterization of solid and cystic transplant renal masses, assessment for pyelonephritis and identification of its complications, and evaluation of transplant complications in immediate and delayed settings. Contrast-enhanced ultrasound will likely play an increasing role for evaluating the transplant kidney, as an accurate diagnosis based on imaging can direct treatment and prevent unnecessary interventions.

Image Interpretation: Practical Triage of Benign from Malignant Renal Masses

Indeterminate renal masses remain a diagnostic challenge for lesions not initially characterized as angiomyolipoma or Bosniak I/II cysts. Differential for indeterminate renal masses include oncocytoma, fat-poor angiomyolipoma, and clear cell, papillary, and chromophobe renal cell carcinoma. Qualitative and quantitative techniques using data derived from multiphase contrast-enhanced imaging have provided methods for specific differentiation and subtyping of indeterminate renal masses, with emerging applications such as radiocytogenetics. Early and accurate characterization of indeterminate renal masses by multiphase contrast-enhanced imaging will optimize triage of these lesions into surgical, ablative, and active surveillance treatment plans.

Use of Contrast Ultrasound for Renal Mass Evaluation

An introduction to the expanding modality of contrast-enhanced ultrasound is provided, along with basics on contrast agents and technique. The contrast ultrasound findings of multiple renal tumors are reviewed with examples, including clear cell renal cell carcinoma, papillary renal cell carcinoma, chromophobe renal cell carcinoma, other rare renal cell carcinoma subtypes, oncocytoma, upper tract urothelial carcinoma, lymphoma, and angiomyolipoma, followed also by brief discussions of renal infections and pseudolesions.

Qualitative and Quantitative Contrast-enhanced Endoscopic Ultrasound Improves Evaluation of Focal Pancreatic Lesions

BACKGROUND & AIMS

Endoscopic ultrasound (EUS) is a sensitive method to evaluate the pancreas but its diagnostic capability for several diseases is limited. We compared the diagnostic yield of unenhanced EUS with that of contrast-enhanced EUS for focal pancreas lesions and identified and tested quantitative parameters of contrast enhancement.

METHODS

We performed a prospective tandem-controlled trial in which 101 patients with focal pancreas lesions (48 with masses, 28 with cysts, and 25 with pancreatitis) underwent conventional EUS followed by contrast EUS using intravenous perflutren microspheres. The diagnosis at each stage was scored and compared with a standard (findings from surgical pathology analysis, cytologic, and/or 6-month clinical follow-up evaluations). Quantitative parameters were generated by time-intensity curve analysis. Solid lesions were divided into derivation and testing cohorts for a crossover validation analysis of the quantitative parameters. The primary outcome was diagnostic yield of unenhanced vs contrast EUS in analysis of focal pancreas lesions.

RESULTS

Contrast increased the diagnostic yield of EUS from 64% (65/101 lesions accurately assessed) to 91% (92/101 lesions accurately assessed); the odds ratio [OR] was 7.8 (95% CI, 2.7-30.2) for accurate analysis of lesions by contrast-enhanced EUS relative to unenhanced EUS. The contrast increased accuracy of analysis of pancreas masses (OR, 6.0; 95% CI, 1.8-31.8), improving assessment of neuroendocrine and other (non-carcinoma) tumors. Contrast increased the diagnostic yield for pancreas cysts to 96% (27/28) compared with 71.4% (20/28) for unenhanced EUS (P = .02), due to improved differentiation of mural nodules vs debris. Time-intensity curve analysis revealed distinct patterns of relative peak enhancement (rPE) and in-slope (rIS) for different lesions following contrast injection: for adenocarcinomas, values were low rPE and low rIS; for neuroendocrine masses, values were high rPE and normal IS; and for chronic pancreatitis foci, values were normal rPE and low rIS. In the validation cohort, these parameters correctly characterized 91% of lesions and improved yield relative to unenhanced EUS (OR, 10; 95% CI, 1.4-34.0).

CONCLUSIONS

Contrast-enhanced EUS improves the accuracy of analysis of focal pancreas lesions, compared with unenhanced EUS. Integration of practical quantitative parameters, specifically relative peak enhancement and in-slope, might increase the diagnostic accuracy of contrast EUS. ClinicalTrials.gov no: 02863770.

The independent indicators for differentiating renal cell carcinoma from renal angiomyolipoma by contrast-enhanced ultrasound

Background

The value of contrast-enhanced ultrasound (CEUS) in differentiating between renal cell carcinoma (RCC) and angiomyolipoma (AML) was analyzed. The purpose of this study was to identify the independent indicators of CEUS for predicting RCC.

Methods

A total of 172 renal tumors (150 RCCs, 22 AMLs) in 165 patients underwent conventional ultrasound (CUS) and CEUS examinations before radical or partial nephrectomy, and the features on CUS and CEUS were analyzed.

Results

There were significant differences in echogenicity, blood flow signals in color Doppler flow imaging (CDFI), peak intensity, homogeneity of enhancement, wash in, wash out, and perilesional rim-like enhancement between RCC and AML (P < 0.05 for all). Multivariate analysis indicated that perilesional rim-like enhancement (P = 0.035, odds ratio [OR] = 9.907, 95% confidence interval [CI]: 1.169–83.971) and fast wash out (P = 0.001, OR = 9.755, 95%[CI]: 2.497–38.115) were independent indicators for predicting RCC. The area under the receiver operating characteristic (ROC) curve (AUC) for perilesional rim-like enhancement was 0.838 (95% CI: 0.774–0.890) with 76.7% sensitivity and 90.9% specificity, while the AUC of fast wash out was 0.833 (95% CI:0.768–0.885) with 74.7% sensitivity and 81.8% specificity.

Conclusions

This study indicated that CEUS has value in differentiating RCC and AML. Present perilesional rim-like enhancement and fast wash out may be important indicators for predicting RCC.

Clinical application of dynamic contrast enhanced ultrasound in monitoring the treatment response of chemoradiotherapy of pancreatic ductal adenocarcinoma

OBJECTIVES

To investigate the value of dynamic contrast enhanced ultrasound (D-CEUS) in monitoring the chemoradiotherapy (CRT) therapeutic response of local advanced pancreatic ductal adenocarcinoma (LAPC).

PATIENTS AND METHODS

From October 2017 to December 2018, 11 patients diagnosed as LAPC were included (7 men, 4 women; mean age: 61.1±8.6 years). The algorithm of CRT was as following: the radiotherapy dose was 50.4 Gy/28Fx with S-1 40 mg bid orally taken in radiotherapy day. Conventional ultrasound scan and CEUS were performed before and 4 weeks after CRT. All ultrasound examinations were performed by an ACUSON Oxana 2 ultrasound equipment (Siemens Medical Solutions, Germany) with a C 6-1 convex array transducer (1-6 MHz). Time intensity curves (TICs) were generated in the region of interests (ROIs) both in LAPC lesions and in its surrounding pancreas parenchyma by SonoLiver software (TOMTEC Imaging Systems). Quantitative perfusion parameters including maximum intensity (MI), rise time (RT), mean transit time (mTT) and time to peak (TTP) were analyzed and compared before and after CRT.

RESULTS

No significant difference could be found by conventional B mode ultrasound scan after CRT. TICs of CEUS showed lower ascending and descending slopes rate after CRT. Among all perfusion quantitative parameters, MI decreased significantly after CRT (42.1±18.8% vs 27.8±17.2%, P < 0.05).

CONCLUSIONS

Depending on its unique advantages as non-radiation, effective and convenient, D-CEUS analysis and quantitative parameters, particularly MI, has potential application value in following up of the CRT treatment response in LAPC patients.

Contrast-Enhanced Ultrasound in Renal Imaging and Intervention

PURPOSE OF REVIEW

In recent years, there has been renewed interest in the use of contrast-enhanced ultrasound (CEUS) in abdominal imaging and intervention. The goal of this article is to review the practical applications of CEUS in the kidney, including renal mass characterization, treatment monitoring during and after percutaneous ablation, and biopsy guidance.

RECENT FINDINGS

Current evidence suggests that CEUS allows accurate differentiation of solid and cystic renal masses and is an acceptable alternative to either computed tomography (CT) or magnetic resonance imaging (MRI) for characterization of indeterminate renal masses. CEUS is sensitive and specific for diagnosing residual or recurrent renal cell carcinoma (RCC) following percutaneous ablation. Furthermore, given its excellent spatial and temporal resolution, CEUS is well suited to demonstrate tumoral microvascularity associated with malignant renal masses and is an effective complement to conventional grayscale ultrasound (US) for percutaneous biopsy guidance. Currently underutilized, CEUS is an important problem-solving tool in renal imaging and intervention whose role will continue to expand in coming years.

Contrast-enhanced harmonic endoscopic ultrasound using time-intensity curve analysis predicts pathological grade of pancreatic neuroendocrine neoplasm

PURPOSE

Histological grading is important for the treatment algorithm in pancreatic neuroendocrine neoplasms (PNEN). The present study examined the efficacy of contrast-enhanced harmonic endoscopic ultrasound (CH-EUS) and time-intensity curve (TIC) analysis of PNEN diagnosis and grading.

METHODS

TIC analysis was performed in 30 patients using data obtained from CH-EUS, and a histopathological diagnosis was made via EUS-guided fine-needle aspiration or surgical resection. The TIC parameters were analyzed by dividing them into G1/G2 and G3/NEC groups. Then, patients were classified into non-aggressive and aggressive groups and evaluated.

RESULTS

Twenty-six patients were classified as G1/G2, and four as G3/NEC. From the TIC analysis, five parameters were obtained (I: echo intensity change, II: time for peak enhancement, III: speed of contrast, IV: decrease rate for enhancement, and V: enhancement ratio for node/pancreatic parenchyma). Three of these parameters (I, IV, and V) showed high diagnostic performance. Using the cutoff value obtained from the receiver-operating characteristic (ROC) analysis, the correct diagnostic rates of parameters I, IV, and V were 96.7%, 100%, and 100%, respectively, between G1/G2 and G3/NEC. A total of 21 patients were classified into the non-aggressive group, and nine into the aggressive group. Using the cutoff value obtained from the ROC analysis, the accurate diagnostic rates of I, IV, and V were 86.7%, 86.7%, and 88.5%, respectively, between the non-aggressive and aggressive groups.

CONCLUSION

CH-EUS and TIC analysis showed high diagnostic accuracy for grade diagnosis of PNEN. Quantitative perfusion analysis is useful to predict PNEN grade diagnosis preoperatively.

Echographic and physical characterization of albumin-stabilized nanobubbles

There has been increasing interest in using nanobubbles (NBs) for ultrasound mediated drug delivery as well as for ultrasound imaging. Albumin NBs are especially attractive for its potential of becoming a versatile platform for drug carriers and molecular targeted therapy agents. However, physical characterization of NBs is generally considered to be difficult due to various technical issues, such as concentration limitations, nanoparticle contamination, etc. In the present study, we measured the size distribution, concentration and weight density of albumin stabilized NBs by means of multiple nanoscale measurement modalities. Laser nanoparticle tracking analysis, multicolor flow cytometry, resonance mass evaluation showed consistent measurement results of the NBs with low mass weight density and diameter size ranging from 100 nm to 400 nm. Furthermore, the NB solution showed excellent images by high frequency ultrasound (30–50 MHz) in flow model acoustic phantoms. The NBs also induced acute cell disruption by low intensity ultrasound (0.8 W/cm²) irradiation. We successfully fabricated and characterized albumin stabilized NBs which could serve as an effective platform for future theranositic agents.

Advanced ultrasound applications in the assessment of renal transplants: contrast-enhanced ultrasound, elastography, and B-flow

Ultrasound is routinely used as the first imaging exam for evaluation of renal transplants and can identify most major surgical complications and evaluate vascularity with color Doppler. Ultrasound is limited, however, in the detection of parenchymal disease processes and Doppler evaluation is also prone to technical errors. Multiple new ultrasound applications have been developed and are under ongoing investigation which could add additional diagnostic capability to the routine ultrasound exam with minimal additional time, cost, and patient risk. Contrast-enhanced ultrasound (CEUS) can be used off-label in the transplant kidney, and can assist in detection of infection, trauma, and vascular complications. CEUS also can demonstrate perfusion of the transplant assessed quantitatively with generation of time-intensity curves. Future directions of CEUS include monitoring treatment response and microbubble targeted medication delivery. Elastography is an ultrasound application that can detect changes in tissue elasticity, which is useful to diagnose diffuse parenchymal disease, such as fibrosis, otherwise unrecognizable with ultrasound. Elastography has been successfully applied in other organs including the liver, thyroid, and breast; however, it is still under development for use in the transplant kidney. Unique properties of the transplant kidney including its heterogeneity, anatomic location, and other technical factors present challenges in the development of reference standard measurements. Lastly, B-flow imaging is a flow application derived from B-mode. This application can show the true lumen size of a vessel which is useful to depict vascular anatomy and bypasses some of the pitfalls of color Doppler such as demonstration of slow flow.

Two in One: Epithelioid angiomyolipoma within a classic kidney angiomyolipoma - a case report

Background

Epithelioid angiomyolipoma is defined as potentially malignant mesenchymal neoplasm, characterized by proliferating epithelioid cells, whereas classic angiomyolipoma, composed of fat, smooth muscle cells and dysmorphic vessels, is defined as a potentially benign. The usual or classic angiomyolipoma is often found incidentally on imaging studies, relatively easily identified due to the presence of fat, in contrast to the epithelioid angiomyolipoma that can pose diagnostic challenges.

Case presentation

We report a 51-year-old female patient in which an ultrasonography examination showed a solid mass close to the right renal pelvis with hypoechoic and hyperechoic areas. A differential diagnosis of atypical sinus lipomatosis, lipoma and a transitional cell carcinoma was postulated whereas in a subsequent computed tomography a classic angiomyolipoma was postulated. A re-examination by contrast enhanced ultrasound revealed a striking perfusion difference of the hypoechoic and hyperechoic areas. The hypoechoic area showed homogenous and prolonged enhancement whereas the hypoechoic area displayed a marked slower contrast material flooding and a relatively rapid wash out. The histological analysis from the biopsy of the hyperechoic area showed a classic angiomyolipoma, whereas the sample of the hypoechoic central portion revealed an epithelioid angiomyolipoma. A nephrectomy was performed because of the malignant potential of the epithelioid variant of the angiomyolipoma.

Conclusions

A solid kidney mass with two sharply defined parts, one-part compatible with a classical angiomyolipoma and the other being suspected of carcinoma, is rare, but also illustrative and instructive. The combination of different imaging modalities in the work up of a solid renal mass facilitated to discriminate benign from malignant areas.

Contrast-enhanced ultrasound for characterizing renal masses

On cross-sectional imaging studies performed for other indications, incidental discovery of renal lesions is not uncommon. In daily use, grey-scale ultrasonography (US) and conventional Doppler modes are often the modality of choice for the initial assessment. While simple cysts are fully characterized with US, other lesions require further characterization, which is traditionally obtained by multiphase imaging, such as contrast-enhanced CT and MRI. Contrast-enhanced ultrasound (CEUS) has become a powerful additional tool for imaging renal lesions. With its lack of nephrotoxicity, the absence of ionizing radiation, and the ability to evaluate the enhancement pattern of renal lesions quickly and in real- time, CEUS has unique advantages over traditional modes. Established applications are differentiation between solid tumours, pseudolesions, and complex cysts; characterization of complex cysts with different malignant potential, and evaluation of tumor ablation. Microbubble contrast agents are safe. Adverse reactions are rare. This article provides an overview of the current clinical applications of CEUS in characterizing renal masses, discussing advantages and limitations. The aim is to provide the framework for sonologists to make informed decisions regarding this emerging imaging test in appropriate circumstances.

Applications of contrast-enhanced ultrasound in the kidney

Incidental discovery of renal lesions on cross-sectional imaging studies performed for other indications is not uncommon. With the increased reliance on medical imaging, the number of incidentally detected renal lesions has also grown over time. While simple cysts account for the majority of these lesions, the presence of complex features within a cystic lesion, such as septations and solid components, can present a confusing picture. Solid lesions, too, can be indeterminate, and distinguishing between benign solid masses (like lipid-poor angiomyolipomas and oncocytomas) and renal cell carcinoma affects patient management and can prevent unnecessary interventions. Indeterminate renal lesions are traditionally further characterized by multiphase imaging, such as contrast-enhanced computed tomography and magnetic resonance imaging. Contrast-enhanced ultrasound (CEUS) is a new, relatively inexpensive technique that has become increasingly employed in the diagnostic workup of indeterminate renal lesions. With its lack of nephrotoxicity, the absence of ionizing radiation, and the ability to evaluate the enhancement pattern of renal lesions quickly and in real-time, CEUS has unique advantages over traditional imaging modalities. This article provides an overview of the current clinical applications of CEUS in characterizing renal lesions, both cystic and solid. Additional applications of CEUS in the kidney, including its roles in renal transplant evaluation and guidance for percutaneous biopsy, will also be briefly discussed.

A Pilot Clinical Study in Characterization of Malignant Renal-cell Carcinoma Subtype with Contrast-enhanced Ultrasound

Malignant renal cell carcinoma (RCC) is a diverse set of diseases, which are independently difficult to characterize using conventional MRI and CT protocols due to low temporal resolution to study perfusion characteristics. Because different disease subtypes have different prognoses and involve varying treatment regimens, the ability to determine RCC subtype non-invasively is a clinical need. Contrast-enhanced ultrasound (CEUS) has been assessed as a tool to characterize kidney lesions based on qualitative and quantitative assessment of perfusion patterns, and we hypothesize that this technique might help differentiate disease subtypes. Twelve patients with RCC confirmed pathologically were imaged using contrast-enhanced ultrasound. Time intensity curves were generated and analyzed quantitatively using 10 characteristic metrics. Results showed that peak intensity ( p = 0.001) and time-to-80% on wash-out ( p = 0.004) provided significant differences between clear cell, papillary, and chromophobe RCC subtypes. These results suggest that CEUS may be a feasible test for characterizing RCC subtypes.

The radiologist's role in the management of papillary renal cell carcinoma

Papillary carcinoma is the second most common renal cell carcinoma. It has a better prognosis than the more frequent clear cell carcinoma, although this does not hold true for advanced cases, because no specific treatment exists. It presents as a circumscribed peripheral tumor (small and homogeneously solid or larger and cystic/hemorrhagic) or as an infiltrating lesion that invades the veins, which has a worse prognosis. Due to their low vascular density, papillary renal cell carcinomas enhance less than other renal tumors, and this facilitates their characterization. On computed tomography, they might not enhance conclusively, and in these cases they are impossible to distinguish from hyperattenuating cysts. Contrast-enhanced ultrasonography and magnetic resonance imaging are more sensitive for detecting vascularization. Other characteristics include a specific vascular pattern, hypointensity on T2-weighted images, restricted water diffusion, and increased signal intensity in opposed phase images. We discuss the genetic, histologic, clinical, and radiological aspects of these tumors in which radiologists play a fundamental role in management.

Ultrasonography of the Kidney: A Pictorial Review

Ultrasonography of the kidneys is essential in the diagnosis and management of kidney-related diseases. The kidneys are easily examined, and most pathological changes in the kidneys are distinguishable with ultrasound. In this pictorial review, the most common findings in renal ultrasound are highlighted.