Comparison of the Diagnostic Performance of Contrast-enhanced Ultrasound with That of Contrast-enhanced Computed Tomography and Contrast-enhanced Magnetic Resonance Imaging in the Evaluation of Renal Masses: A Systematic Review and Meta-analysis

Contrast-enhanced ultrasound of renal masses in the pre-transplant setting: literature review with case highlights

With the rising incidence of chronic kidney disease worldwide, an increasing number of patients are expected to require renal transplantation, which remains the definitive treatment of end stage renal disease. Medical imaging, primarily ultrasonography and contrast-enhanced CT and/or MRI, plays a large role in pre-transplantation assessment, especially in the characterization of lesions within the native kidneys. However, patients with CKD/ESRD often have relative contraindications to CT- and MR-contrast agents, limiting their utilization within this patient population. Contrast-enhanced ultrasound (CEUS), which combines the high temporal and spatial resolution of ultrasonography with intravascular microbubble contrast agents, provides a promising alternative. This review aims to familiarize the reader with the literature regarding the use of CEUS in the evaluation of cystic and solid renal lesions and provide case examples of its use at our institution in the pre-transplant setting.

Contrast-enhanced ultrasound (CEUS) as a follow-up method after the focal treatment of renal tumors: systematic review and meta-analysis

CONTEXT

Contrast-enhanced ultrasound (CEUS) is a cost-effective radiation-free diagnostic method that can be used for renal tumor postoperative visualization after ablative treatment.

OBJECTIVE

To assess CEUS diagnostic accuracy comparing with CT and MRI as a follow-up method in short-term and long-term postoperative periods after renal tumor ablation.

MATERIALS AND METHODS

A systematic review and meta-analysis were performed in Scopus and Medline databases using the query "(kidney OR rena* OR RCC) AND (ablation OR RFA OR MWA OR cryo*) AND CEUS". The endpoint of the study was the evaluation of the overall accuracy of CEUS.

RESULTS

Twelve trials were included in the review. With CT or MRI as a reference, for a short-term group (< 6 weeks after ablation) pooled sensitivity was 90.2%, I2 = 0%; pooled specificity was 99.3%, I2 = 0%; pooled NPV was 98.6%, I2 = 0%; pooled PPV was 94.6%, I2 = 0%; the AUC on the SROC curve was 0.971. For the long-term group (> 6 weeks after ablation), pooled sensitivity was 95.3%, I2 = 0%; pooled specificity was 97.6%, I2 = 0%; PPV was 74.2%, I2 = 4%; NPV was 99.4%, I2 = 5%; AUC = 0.93.

CONCLUSION

CEUS has high sensitivity and specificity in ruling out the presence of local recurrence after renal tumor ablation with a higher risk of false-positive results within follow-up > 6 weeks compared with that for CT or MRI. Further studies with a unified protocol and morphological control of local renal tumor recurrence after ablation are needed.

Ultrasound Contrast Agents: Current Role in Adults and Children for Various Indications

Intravenous contrast-enhanced ultrasound (CEUS) is a rapidly evolving imaging technique that uses a microbubble contrast agent to enhance ultrasonographic images by augmenting characterization of blood vessels and organ perfusion. CEUS is considered as a useful problem-solving tool and as an indicated first-line imaging modality in select settings. CEUS technique has an inherent advantage over its predecessor B-mode and Doppler imaging. This article reviews different approved and off-label use of CEUS in the pediatric and adult population and also discusses Food and Drug Administration-approved contrast agents in the United States, their reported side effects, and ongoing efforts in the field.

Qualitative and quantitative analysis of solid renal tumors by high-frame-rate contrast-enhanced ultrasound

OBJECTIVE

To analyze the characteristics of high-frame-rate contrast-enhanced ultrasound (H-CEUS) in solid renal tumors using qualitative and quantitative methods.

METHODS

Seventy-five patients who underwent preoperative conventional ultrasound (US), conventional contrast-enhanced ultrasound (C-CEUS), and H-CEUS examination of renal tumors were retrospectively analyzed, with a total of 89 renal masses. The masses were divided into the benign (30 masses) and malignant groups (59 masses) based on the results of enhanced computer tomography and pathology. The location, diameter, shape, border, calcification, and color doppler blood flow imaging (CDFI) of the lesions were observed by US, and the characteristics of the C-CEUS and H-CEUS images were qualitatively and quantitatively analyzed. The χ² test or Fisher's exact probability method was used to compare the US image characteristics between the benign and malignant groups, and the image characteristics of C-CEUS and H-CEUS between the benign and malignant groups. Moreover, the nonparametric Mann-Whitney test was used to compare the differences in C-CEUS and H-CEUS time-intensity curve (TIC) parameters.

RESULTS

Significant differences in gender, surgical approach, echogenicity, and CDFI were observed between the malignant and benign groups (p = 0.003, < 0.001, < 0.001, = 0003). Qualitative analysis also revealed significant differences in the mode of wash-out and fill-in direction between C-CEUS and H-CEUS in the malignant group (p = 0.041, 0.002). In addition, the homogeneity of enhancement showed significant differences between the two contrast models in the benign group (p = 0.009). Quantitative analysis indicated that the TIC parameters peak intensity (PI), deceleration time (DT) /2, area under the curve (AUC), and mean transition time (MTT) were significantly lower in the H-CEUS model compared to the C-CEUS model in both the benign and malignant groups. (all p < 0.001). In contrast, ascending slope of rise curve (AS) was significantly higher in the H-CEUS model compared to the C-CEUS model in the malignant group (p = 0.048).

CONCLUSIONS

In renal tumors, H-CEUS shows clearer internal enhancement of the mass and the changes in the wash-out period. The quantitative TIC parameters PI, DT/2, AUC, and MTT were lower in H-CEUS compared to C-CEUS. Both the quantitative and qualitative analyses indicated that H-CEUS better displays the characteristics of solid renal masses compared with C-CEUS.

Frequency of benign tumors after partial nephrectomy and the association between malignant tumor findings and preoperative clinical parameters

BACKGROUND

Partial nephrectomy (PN) has become the dominant treatment modality for cT1 renal tumor lesions. Tumors suspected of malignant potential are indicated for surgery, but some are histologically classified as benign lesions after surgery. This study aims to analyze the number of benign findings after PN according to definitive histology and to evaluate whether there is an association between malignant tumor findings and individual factors.

METHODS

The retrospective study included 555 patients who underwent open or robotic-assisted PN for a tumor in our clinic from January 2013 to December 2020. The cohort was divided into groups according to definitive tumor histology (malignant tumors vs. benign lesions). The association of factors (age, sex, tumor size, R.E.N.A.L.) with the malignant potential of the tumor was further evaluated.

RESULTS

In total, 462 tumors were malignant (83%) and 93 benign (17%). Of the malignant tumors, 66% were clear-cell RCC (renal cell carcinoma), 12% papillary RCC, and 6% chromophobe RCC. The most common benign tumor was oncocytoma in 10% of patients, angiomyolipoma in 2%, and papillary adenoma in 1%. In univariate analysis, there was a higher risk of malignant tumor in males (OR 2.13, 95% CI 1.36-3.36, p = 0.001), a higher risk of malignancy in tumors larger than 20 mm (OR 2.32, 95% CI 1.43-3.74, p < 0.001), and a higher risk of malignancy in tumors evaluated by R.E.N.A.L. as tumors of intermediate or high complexity (OR 2.8, 95% CI 1.76-4.47, p < 0.001). In contrast, there was no association between older age and the risk of malignant renal tumor (p = 0.878).

CONCLUSIONS

In this group, 17% of tumors had benign histology. Male sex, tumor size greater than 20 mm, and intermediate or high R.E.N.A.L. complexity were statistically significant predictors of malignant tumor findings.

Evaluation of contrast-enhanced ultrasound for predicting tumor grade in small (≤4 cm) clear cell renal cell carcinoma: Qualitative and quantitative analysis

OBJECTIVE

The study aimed to evaluate the utility of qualitative and quantitative analysis employing contrast-enhanced ultrasound (CEUS) in predicting the WHO/ISUP grade of small (≤4 cm) clear cell renal cell carcinoma (ccRCCs).

METHODS

Patients with small ccRCCs, confirmed by histological examination, underwent preoperative CEUS and were classified into low- (grade I/II) and high-grade (grade III/IV) groups. Qualitative and quantitative assessments of CEUS were conducted and compared between the two groups. Diagnostic performance was assessed using receiver operating characteristic curves.

RESULTS

A total of 72 patients were diagnosed with small ccRCCs, comprising 23 individuals in the high-grade group and 49 in the low-grade group. The low-grade group exhibited a significantly greater percentage of hyper-enhancement compared to the high-grade group (79.6% VS 39.1%, P < 0.05). The low-grade group showed significantly higher relative index values for peak enhancement, wash-in area under the curve, wash-in rate, wash-in perfusion index, and wash-out rate compared to the high-grade group (all P < 0.05). The AUC values for qualitative and quantitative parameters in predicting the WHO/ISUP grade of small ccRCCs ranged from 0.676 to 0.756.

CONCLUSIONS

Both qualitative and quantitative CEUS analysis could help to distinguish the high- from low-grade small ccRCCs.

Ultrasound findings and clinical characteristics in differentiating renal urothelial carcinoma from endophytic clear cell renal cell carcinoma

OBJECTIVE

This study aimed to evaluate the clinical characteristics and features of conventional ultrasound (CUS) and contrast-enhanced ultrasound (CEUS) in differentiating between renal urothelial carcinomas (RUC) and endophytic clear cell renal cell carcinomas (EccRCC).

METHODS

A total of 72 RUCs and 120 EccRCCs confirmed by pathology were assessed retrospectively. Both CUS and CEUS were performed within 4 weeks before the surgery. Logistic regression analyses were used to select statistically significant variables of clinical, CUS, and CEUS features for the differentiation of RUC and EccRCC. Sensitivity (SEN), specificity (SPE), and the area under the receiver-operating characteristic curve (AUC) were assessed for diagnostic performance. Inter- and intra-observer agreements of CUS and CEUS features were evaluated using the intra-class correlation coefficient(ICC).

RESULTS

Multiple logistic regression analysis demonstrated that clinical (age >50 years old and hematuria), CUS (size <4.0 cm, hypo-echogenicity, irregular shape, hydronephrosis) and CEUS (absence of non-enhancement area, iso- /hypo-enhancement in cortical phase and absence of rim-like enhancement) features were independent factors for RUC diagnosis. When combining clinical characters with CUS and CEUS features into an integrated diagnostic criterion, the AUC reached 0.917 (95% CI 0.873-0.961), with a sensitivity of 95.8% and specificity of 87.5%. ICC ranged from 0.756 to 0.907 for inter-observer agreement and 0.791 to 0.934 for intra-observer agreement for CUS and CEUSfeatures.

CONCLUSIONS

The combination of clinical features of age and hematuria with imaging features of CUS and CEUS can be useful for the differentiation between RUC and EccRCC.

Imaging modalities for characterising T1 renal tumours: A systematic review and meta-analysis of diagnostic accuracy

Objectives

International guidelines recommend resection of suspected localised renal cell carcinoma (RCC), with surgical series showing benign pathology in 30%. Non-invasive diagnostic tests to differentiate benign from malignant tumours are an unmet need. Our objective was to determine diagnostic accuracy of imaging modalities for detecting cancer in T1 renal tumours.

Methods

A systematic review was performed for reports of diagnostic accuracy of any imaging test compared to a reference standard of histopathology for T1 renal masses, from inception until January 2023. Twenty-seven publications (including 2277 tumours in 2044 participants) were included in the systematic review, and nine in the meta-analysis.

Results

Forest plots of sensitivity and specificity were produced for CT (seven records, 1118 participants), contrast-enhanced ultrasound (seven records, 197 participants), [99mTc]Tc-sestamibi SPECT/CT (five records, 263 participants), MRI (three records, 220 participants), [18F]FDG PET (four records, 43 participants), [68Ga]Ga-PSMA-11 PET (one record, 27 participants) and [111In]In-girentuximab SPECT/CT (one record, eight participants). Meta-analysis returned summary estimates of sensitivity and specificity for [99mTc]Tc-sestamibi SPECT/CT of 88.6% (95% CI 82.7%-92.6%) and 77.0% (95% CI 63.0%-86.9%) and for [18F]FDG PET 53.5% (95% CI 1.6%-98.8%) and 62.5% (95% CI 14.0%-94.5%), respectively. A comparison hierarchical summary receiver operating characteristic (HSROC) model did not converge. Meta-analysis was not performed for other imaging due to different thresholds for test positivity.

Conclusion

The optimal imaging strategy for T1 renal masses is not clear. [99mTc]Tc-sestamibi SPECT/CT is an emerging tool, but further studies are required to inform its role in clinical practice. The field would benefit from standardisation of diagnostic thresholds for CT, MRI and contrast-enhanced ultrasound to facilitate future meta-analyses.

Comparing Sonazoid contrast-enhanced ultrasound to contrast-enhanced CT and MRI for differentially diagnosing renal lesions: a prospective multicenter study

PURPOSE

To evaluate the diagnostic performance of contrast-enhanced (CE) ultrasound using Sonazoid (SNZ-CEUS) by comparing with contrast-enhanced computed tomography (CE-CT) and contrast-enhanced magnetic resonance imaging (CE-MRI) for differentiating benign and malignant renal masses.

MATERIALS AND METHODS

306 consecutive patients (from 7 centers) with renal masses (40 benign tumors, 266 malignant tumors) diagnosed by both SNZ-CEUS, CE-CT or CE-MRI were enrolled between September 2020 and February 2021. The examinations were performed within 7 days, but the sequence was not fixed. Histologic results were available for 301 of 306 (98.37%) lesions and 5 lesions were considered benign after at least 2 year follow-up without change in size and image characteristics. The diagnostic performances were evaluated by sensitivity, specificity, positive predictive value, negative predictive value, and compared by McNemar's test.

RESULTS

In the head-to-head comparison, SNZ-CEUS and CE-MRI had comparable sensitivity (95.60 vs. 94.51%, P = 0.997), specificity (65.22 vs. 73.91%, P = 0.752), positive predictive value (91.58 vs. 93.48%) and negative predictive value (78.95 vs. 77.27%); SNZ-CEUS and CE-CT showed similar sensitivity (97.31 vs. 96.24%, P = 0.724); however, SNZ-CEUS had relatively lower than specificity than CE-CT (59.09 vs. 68.18%, P = 0.683). For nodules > 4 cm, CE-MRI demonstrated higher specificity than SNZ-CEUS (90.91 vs. 72.73%, P = 0.617) without compromise the sensitivity.

CONCLUSIONS

SNZ-CEUS, CE-CT, and CE-MRI demonstrate desirable and comparable sensitivity for the differentiation of renal mass. However, the specificity of all three imaging modalities is not satisfactory. SNZ-CEUS may be a suitable alternative modality for patients with renal dysfunction and those allergic to gadolinium or iodine-based agents.

Development and validation of a clinical and ultrasound features-based nomogram for preoperative differentiation of renal urothelial carcinoma and central renal cell carcinoma

PURPOSE

This study aimed to develop and validate an ultrasound (US)-based nomogram for the preoperative differentiation of renal urothelial carcinoma (rUC) from central renal cell carcinoma (c-RCC).

METHODS

Clinical data and US images of 655 patients with 655 histologically confirmed malignant renal tumors (521 c-RCCs and 134 rUCs) were collected and divided into training (n = 455) and validation (n = 200) cohorts according to examination dates. Conventional US and contrast-enhanced US (CEUS) tumor features were analyzed to determine those that could discriminate rUC from c-RCC. Least absolute shrinkage and selection operator regression was applied to screen clinical and US features for the differentiation of rUC from c-RCC. Using multivariate logistic regression analysis, a diagnostic model of rUC was constructed and visualized as a nomogram. The diagnostic model's performance was assessed in the training and validation cohorts by calculating the area under the receiver operating characteristic curve (AUC) and calibration plot. Decision curve analysis (DCA) was used to assess the clinical usefulness of the US-based nomogram.

RESULTS

Seven features of both clinical features and ultrasound imaging were selected to build the diagnostic model. The nomogram achieved favorable discrimination in the training (AUC = 0.996, 95% CI: 0.993-0.999) and validation (AUC = 0.995, 95% CI: 0.974, 1.000) cohorts, and good calibration (Brier scores: 0.019 and 0.016, respectively). DCA demonstrated the clinical usefulness of the US-based nomogram.

CONCLUSION

A noninvasive clinical and US-based nomogram combining conventional US and CEUS features possesses good predictive value for differentiating rUC from c-RCC.

The Diagnostic Value of CEUS in Assessing Non-Ossified Thyroid Cartilage Invasion in Patients with Laryngeal Squamous Cell Carcinoma

Background: Accurate assessment of thyroid cartilage invasion in squamous cell carcinoma (SCC) of the larynx remains a challenge in clinical practice. The aim of this study was to assess the diagnostic performance of contrast-enhanced ultrasound (CEUS), contrast-enhanced computed tomography (CECT), and magnetic resonance imaging (MRI) in the detection of non-ossified thyroid cartilage invasion in patients with SCC. Methods: CEUS, CECT, and MRI scans of 27 male patients with histologically proven SCC were evaluated and compared. A total of 31 cases were assessed via CEUS and CECT. The MR images of five patients and six cases were excluded (one patient had two suspected sites), leaving twenty-five cases for analysis via MRI. Results: CEUS showed the highest accuracy and specificity compared with CECT and MRI (87.1% vs. 64.5% and 76.0% as well as 84.0% vs. 64.0% and 72.7%, respectively). The sensitivity and negative predictive value of CEUS and MRI were the same (100%). CEUS yielded four false-positive findings. However, there were no statistically significant differences among the imaging modalities (p > 0.05). Conclusions: CEUS showed better diagnostic performance than CECT and MRI. Therefore, CEUS has the potential to accurately assess non-ossified thyroid cartilage invasion and guide appropriate treatment decisions, hopefully leading to improved patient outcomes.

Role of Contrast-Enhanced Ultrasound With the Enhancement Pattern and Qualitative Analysis for Differentiating Hypovascular Solid Renal Lesions

OBJECTIVE

The aim of the work described here was to explore the clinical value of contrast-enhanced ultrasound (CEUS) with the enhancement pattern and qualitative analysis in distinguishing different types of hypovascular solid renal lesions.

METHODS

A total of 140 patients with 140 renal tumors (all diagnosed by pathology), which manifested hypo-enhancement on CEUS, were included in this study. We compared conventional ultrasound (US) and CEUS features in five common hypovascular renal tumors, including renal angiomyolipoma (RAML), clear cell renal cell carcinoma (ccRCC), renal pelvic urothelial carcinoma (RPUC), papillary renal cell carcinoma (pRCC) and chromophobe renal cell carcinoma (chRCC). The diagnostic value of conventional US and qualitative parameters of CEUS for differentiating hypovascular solid renal lesions were evaluated.

RESULTS

The mean age of patients with a benign renal lesion was younger than that of patients with a malignant renal lesion (p < 0.05). Echogenicity and qualitative parameters such as wash-out, perfusion defects and perilesional rim-like enhancement (PRE) in the two groups differed significantly (all p values <0.05). Benign renal lesions exhibited mainly slow wash-out, whereas malignant renal lesions exhibited predominantly fast wash-out on CEUS (p < 0.05). There were significant differences in echogenicity, such as between RAML and ccRCC, between RAML and RPUC and between RAML and pRCC (all p values <0.05). The rates of appearance of perfusion defect in ccRCC (48%, 13/27) and pRCC (53%, 10/19) were significantly higher than the rate in RAML (14%, 6/43) (p < 0.05). The rates of appearance of PRE in ccRCC (15%, 4/27), pRCC (26%, 5/19) and chRCC (24%,4/17) were significantly higher than the rate in RAML (9%, 4/43) (p < 0.05).

CONCLUSION

CEUS with the enhancement pattern and qualitative analysis may be helpful in distinguishing malignant from benign hypovascular renal lesions.

Role of Contrast-Enhanced Ultrasound in Evaluation of Cystic Renal Mass

OBJECTIVES

Contrast-enhanced ultrasound (CEUS) allows excellent delineation of perfusion in septa and nodules without exposure to ionizing radiation or nephrotoxic contrast media. The aim of our study was to evaluate the role of CEUS for the assessment of cystic renal masses and compare its diagnostic performance with that of CECT.

METHODS

Exactly 40 patients diagnosed to have cystic renal masses on CECT scan were prospectively evaluated with CEUS and were assigned a Bosniak class. Based on results of final histopathology and clinical follow-up, internal validity of both CEUS and CECT was evaluated, including agreement between these two modalities.

RESULTS

Out of the 40 patients (mean size 3.1 ± 2.5 cm), 23 patients had benign lesions and 17 patients had malignant lesions. For CEUS, the sensitivity and negative predictive value was 100%, the specificity and positive predictive value was 73.9%. For CECT, the sensitivity and negative predictive value were 88.2 and 83.3%, respectively, whereas the specificity and positive predictive value was 87 and 90.9%, respectively. Both imaging modalities had similar accuracy with fair to good agreement with the final diagnosis (Κ = 0.71 and 0.75 for CEUS and CECT, respectively). Concordance between CEUS and CECT was seen in 29 patients (72.5%) with fair agreement between the two modalities (K = 0.66).

CONCLUSION

CEUS has comparable accuracy with CECT and could be used as screening modality to rule out the presence of complex cystic renal masses without exposure of nephrotoxic contrast media and ionizing radiation.

Deep learning techniques for imaging diagnosis of renal cell carcinoma: current and emerging trends

This study summarizes the latest achievements, challenges, and future research directions in deep learning technologies for the diagnosis of renal cell carcinoma (RCC). This is the first review of deep learning in RCC applications. This review aims to show that deep learning technologies hold great promise in the field of RCC diagnosis, and we look forward to more research results to meet us for the mutual benefit of renal cell carcinoma patients. Medical imaging plays an important role in the early detection of renal cell carcinoma (RCC), as well as in the monitoring and evaluation of RCC during treatment. The most commonly used technologies such as contrast enhanced computed tomography (CECT), ultrasound and magnetic resonance imaging (MRI) are now digitalized, allowing deep learning to be applied to them. Deep learning is one of the fastest growing fields in the direction of medical imaging, with rapidly emerging applications that have changed the traditional medical treatment paradigm. With the help of deep learning-based medical imaging tools, clinicians can diagnose and evaluate renal tumors more accurately and quickly. This paper describes the application of deep learning-based imaging techniques in RCC assessment and provides a comprehensive review.

Diagnostic performance of multiparametric magnetic resonance imaging in the differentiation of clear cell renal cell cancer

PURPOSE

This study aimed to evaluate the diagnostic performance of multiparametric magnetic resonance imaging (mpMRI) in the differentiation of renal cell carcinoma (RCC) subtypes.

METHODS

This is a retrospective diagnostic performance study, in which the diagnostic performances of mpMRI features were evaluated to differentiate clear cell RCC (ccRCC) from non-clear cell RCC (non-ccRCC). Adult patients who were evaluated using a 3-Tesla dynamic contrast-enhanced mpMRI before undergoing partial or radical nephrectomy for possible malignant renal tumors were included in the study. Signal intensity change percentages (SICP) between contrast-enhanced phases and pre-administration period for both the tumor and normal renal cortex, and tumor-to-cortex enhancement index (TCEI); tumor apparent diffusion coefficient (ADC) values; tumor-to-cortex ADC ratio; and a scale which was developed according to the tumor signal intensities on the axial fat-suppressed T2-weighted Half-Fourier Acquisition Single-shot Turbo spin Echo (HASTE) images were used in ROC analysis to estimate the presence of ccRCC in the patients. The reference test positivity was the histopathologic examination of the surgical specimens.

RESULTS

Ninety-eight tumors from 91 patients were included in the study, and 59 of them were ccRCC, 29 were pRCC, and 10 were chRCC. The mpMRI features that had the three highest sensitivity rates were excretory phase SICP, T2-weighted HASTE scale score, and corticomedullary phase TCEI (93.2%, 91.5%, and 86.4%, respectively). However, those with the three highest specificity rates were nephrographic phase TCEI, excretory phase TCEI, and tumor ADC value (94.9%, 94.9%, and 89.7%, respectively).

CONCLUSION

Several parameters on mpMRI showed an acceptable performance to differentiate ccRCC from non-ccRCC.

CNN-based automatic segmentations and radiomics feature reliability on contrast-enhanced ultrasound images for renal tumors

Objective

To investigate the feasibility and efficiency of automatic segmentation of contrast-enhanced ultrasound (CEUS) images in renal tumors by convolutional neural network (CNN) based models and their further application in radiomic analysis.

Materials and methods

From 94 pathologically confirmed renal tumor cases, 3355 CEUS images were extracted and randomly divided into training set (3020 images) and test set (335 images). According to the histological subtypes of renal cell carcinoma, the test set was further split into clear cell renal cell carcinoma (ccRCC) set (225 images), renal angiomyolipoma (AML) set (77 images) and set of other subtypes (33 images). Manual segmentation was the gold standard and serves as ground truth. Seven CNN-based models including DeepLabV3+, UNet, UNet++, UNet3+, SegNet, MultilResUNet and Attention UNet were used for automatic segmentation. Python 3.7.0 and Pyradiomics package 3.0.1 were used for radiomic feature extraction. Performance of all approaches was evaluated by the metrics of mean intersection over union (mIOU), dice similarity coefficient (DSC), precision, and recall. Reliability and reproducibility of radiomics features were evaluated by the Pearson coefficient and the intraclass correlation coefficient (ICC).

Results

All seven CNN-based models achieved good performance with the mIOU, DSC, precision and recall ranging between 81.97%-93.04%, 78.67%-92.70%, 93.92%-97.56%, and 85.29%-95.17%, respectively. The average Pearson coefficients ranged from 0.81 to 0.95, and the average ICCs ranged from 0.77 to 0.92. The UNet++ model showed the best performance with the mIOU, DSC, precision and recall of 93.04%, 92.70%, 97.43% and 95.17%, respectively. For ccRCC, AML and other subtypes, the reliability and reproducibility of radiomic analysis derived from automatically segmented CEUS images were excellent, with the average Pearson coefficients of 0.95, 0.96 and 0.96, and the average ICCs for different subtypes were 0.91, 0.93 and 0.94, respectively.

Conclusion

This retrospective single-center study showed that the CNN-based models had good performance on automatic segmentation of CEUS images for renal tumors, especially the UNet++ model. The radiomics features extracted from automatically segmented CEUS images were feasible and reliable, and further validation by multi-center research is necessary.

Second-Generation Differential Tissue Harmonic Imaging Improves the Visualization of Renal Lesions

OBJECTIVES

To compare to three nonlinear imaging techniques to conventional, grayscale ultrasound imaging of renal lesions.

METHODS

Twenty adults with a known renal lesion and a body mass index >25 kg/m² were enrolled in this prospective, institutional review board approved study. Each subject was imaged with an Aplio 500 scanner (Canon Medical Systems, Tokyo, Japan) using grayscale ultrasound, tissue harmonic imaging (THI) and two dual-frequency, differential tissue harmonic imaging modes (DTHI and DTHI-II, respectively). In total 184 images were scored by three independent and blinded observers for detail resolution, image quality, margin delineation, and depth penetration. Quantitative contrast-to-noise ratios (CNRs) were also calculated.

RESULTS

Readers and CNR values showed that nonlinear imaging was superior to grayscale ultrasound (P < .0014). DTHI-II outperformed DTHI, THI, and grayscale ultrasound with respect to detail resolution, image quality, and margin delineation (P < .012). The depth penetration of DTHI and DTHI-II was similar (P = .16), but superior to grayscale ultrasound and THI (P < .001). Two observers saw improvements in detail resolution with DTHI-II over DTHI (P < .05), while image quality and margin delineation were considered similar by two readers (P > .07) and improved with DTHI-II by one (P < .017).

CONCLUSIONS

DTHI-II improves the imaging of renal lesions compared to DTHI, THI, and grayscale ultrasound, albeit based on a limited sample size.

Human Urinary Volatilome Analysis in Renal Cancer by Electronic Nose

Currently, in clinical practice there are still no useful markers available that are able to diagnose renal cancer in the early stages in the context of population screening. This translates into very high costs for healthcare systems around the world. Analysing urine using an electronic nose (EN) provides volatile organic compounds that can be easily used in the diagnosis of urological diseases. Although no convincing results have been published, some previous studies suggest that dogs trained to sniff urine can recognize different types of tumours (bladder, lung, breast cancer) with different success rates. We therefore hypothesized that urinary volatilome profiling may be able to distinguish patients with renal cancer from healthy controls. A total of 252 individuals, 110 renal patients and 142 healthy controls, were enrolled in this pilot monocentric study. For each participant, we collected, stabilized (at 37 °C) and analysed urine samples using a commercially available electronic nose (Cyranose 320^®). Principal component (PCA) analyses, discriminant analysis (CDA) and ROC curves were performed to provide a complete statistical analysis of the sensor responses. The best discriminating principal component groups were identified with univariable ANOVA analysis. The study correctly identified 79/110 patients and 127/142 healthy controls, respectively (specificity 89.4%, sensitivity 71.8%, positive predictive value 84.04%, negative predictive value 80.37%). In order to test the study efficacy, the Cross Validated Accuracy was calculated (CVA 81.7%, p < 0.001). At ROC analysis, the area under the curve was 0.85. The results suggest that urine volatilome profiling by e-Nose seems a promising, accurate and non-invasive diagnostic tool in discriminating patients from controls. The low costs and ease of execution make this test useful in clinical practice.

Diagnostic Value of Qualitative and Quantitative Contrast-Enhanced Ultrasound for Pathological Subtypes of Small Solid Renal Masses

OBJECTIVES

To assess the diagnostic value of qualitative and quantitative contrast-enhanced ultrasound (CEUS) for pathological subtypes of small solid renal masses (sSRMs).

METHODS

Patients with sSRMs confirmed by surgical pathology from January 2019 to November 2021 were retrospectively identified. All patients were divided into 3 groups: clear cell renal cell carcinoma (ccRCC) group, none-ccRCC group (renal cell carcinoma other than ccRCC), and angiomyolipoma (AML) group. The mass position, size, echogenicity and blood flow signals were compared. The speed of wash-in, wash-out, the degree of peak enhancement and the homogeneity at peak enhancement, the presence of pseudocapsule sign in CEUS imaging were qualitatively evaluated. Peak enhancement, wash-in area under the curve (WiAUC), rise time, time to peak, wash-in rate (WiR), wash-in perfusion index (WiPI) and tumor-to-cortex enhancement ratio of the above parameters in CEUS imaging were quantitatively evaluated.

RESULTS

Of 105 patients, 105 sSRMs (66 ccRCC, 18 none-ccRCC, 21 AML) were enrolled in this study. No significant differences were found on location, size and echogenicity among 3 groups (all P > .05). The proportion of fast-washout and hypo-enhancement were highest in none-ccRCC group. Heterogeneous enhancement was detected in 87.88% in ccRCC group which is significantly higher than other 2 groups. Hundred percent of the AML showed no pseudocapsule sign, which is the highest among the 3 groups. Peak enhancement, WiAUC, WiR, WiPI of ccRCC group were the highest among the 3 groups.

CONCLUSIONS

Qualitative and quantitative CEUS not only has the diagnostic value in distinguishing AML from malignant sSRMs, but also helps to differentiate the pathological subtypes of sSRMs.

Utility of Fluorine18 Fluoro-2-deoxy-D-glucose Positron Emission Tomography/Computed Tomography in Metabolic Characterization of Solid Renal Mass Lesion and Localization of Extra Renal Lesions in the Body - A Prospective Study from the Tertiary Care Center in South India

Purpose of the Study

Renal mass lesions in majority of the cases are due to malignant etiology and about one-third of them are reported with metastatic lesions at the time of presentation. Thus proper investigational workup is needed for staging and thereby treatment planning. The current fluorine18 fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (F18-FDG PET/CT) study was designed to characterize renal mass lesions metabolically and identifying other metabolically active lesions in the body suggesting metastatic disease.

Materials and Methods

A total of 24 patients (males - 18 and females - 6) with a mean age of 53.8 ± 12.3 years were recruited in this study for dual time-point PET/CT scan. All patients with renal mass lesions underwent contrast-enhanced CT prior to PET/CT. Metabolic parameters such as maximum standardized uptake value (max.SUV) with a cut off ≥2.5 and retention index (RI) of ≥10% were used to label the lesion as malignant and remaining less than cutoff as benign. The final diagnosis of lesion on imaging was confirmed with a histopathological examination (HPE).

Results

Using max.SUV cut off value, 17/24 renal mass lesions were characterized as malignant and remaining 7/24 renal lesions of benign etiology. PET/CT showed sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 80%, 75%, 94.1%, 42.8%, and 79.1%, respectively, by considering HPE as a gold standard. Nine patients were diagnosed with distant site involvement suggestive of metastases.

Conclusion

F18-FDG PET/CT can efficiently characterize solid renal mass lesion as benign and malignant using metabolic parameters such as max.SUV and RI. In addition, whole-body survey identified distant site involvement in 25% of the patients, thus contributing change in management.

Contrast-enhanced ultrasound (CEUS) of benign and malignant renal tumors: Distinguishing CEUS features differ with tumor size

BACKGROUND

Contrast-enhanced ultrasound (CEUS) is now a guideline-recommended strategy for diagnosing renal lesions. Tumor size is related to the risk of the treatment and prognosis in renal tumors. Thus, we aim to analyze the CEUS features of solid renal tumors in relation to tumor size.

METHODS

The CEUS appearance of 156 pathologically diagnosed solid renal tumors were retrospectively analyzed. Three groups were stratified according to the tumor size (≤2 cm [group I], 2.1-4 cm [group II] and 4.1-7 cm [group III]). For each group, the features of wash-in type, enhancement degree, enhancement homogeneity, and the presence of a pseudocapsule sign were compared between benign and malignant tumors.

RESULTS

All 156 included lesions were detected by CEUS. The proportion of benign tumors in three size groups was 37.1%, 19.4%, and 20.4%, respectively. The proportion of malignant tumors was highest (80.6%) in group II, followed by group III (79.6%) and group I (62.9%). In group I, malignant and benign tumors differed significantly in the presence of a pseudocapsule sign (p = 0.015) and homogeneity (p = 0.007). In group II, the degree of enhancement differed (p = 0.02) between tumor types. In group III, the two tumor types differed in both the wash-in pattern (p = 0.015) and enhancement degree (p = 0.024). The weighted and Cohen's kappa values for the concordance between inter-observer agreement ranged from 0.31 (95% CI: 0.36-0.57) to 0.90 (95% CI: 0.77-1.00).

CONCLUSIONS

CEUS features of malignant and benign renal tumors change along with the tumor size. The use of CEUS features in the diagnosis of benign and malignant tumors requires consideration of tumor size.

Contrast-Enhanced Ultrasound as a Problem-Solving Modality: Tips and Tricks

ABSTRACT

Contrast-enhanced ultrasound (CEUS) continues to be an ever-growing tool in radiation-free imaging. While it has been widely used in cardiac imaging, CEUS has only recently become an Food and Drug Administration-approved and viable modality for evaluation of abdominal structures. Ultrasound contrast agents are nontoxic, microbubble-based vascular agents and can be used to reliably assess enhancement patterns of various lesions in real time. In particular, it's non nephrotoxic nature makes CEUS a particularly important tool in renal failure patients requiring serial follow-up. This review provides a comprehensive discussion on the utility of CEUS agents, imaging techniques, comparison with traditional cross-sectional imaging modalities, and its application in diagnosing kidney and liver lesions. This pictorial review is illustrated with cases of renal and hepatic lesions that the practicing radiologist should become familiar with as CEUS becomes increasingly popular.

Contrast-enhanced US of the Liver and Kidney: A Problem-solving Modality

Contrast-enhanced US (CEUS) has an important role as a supplement to CT or MRI in clinical practice. The main established utilizations are in the liver and the kidney. The primary advantages of CEUS compared with contrast-enhanced CT or MRI relate to its superior contrast resolution, real-time continuous scanning, pure intravascular nature, portability, and safety-especially in patients with renal impairment or CT or MRI contrast agent allergy. This article focuses on the use of CEUS in the liver and kidney.

Expanding the Role of Ultrasound for the Characterization of Renal Masses

The incidental detection of renal masses has been steadily rising. As a significant proportion of renal masses that are surgically treated are benign or indolent in nature, there is a clear need for better presurgical characterization of renal masses to minimize unnecessary harm. Ultrasound is a widely available and relatively inexpensive real-time imaging technique, and novel ultrasound-based applications can potentially aid in the non-invasive characterization of renal masses. Evidence acquisition: We performed a narrative review on novel ultrasound-based techniques that can aid in the non-invasive characterization of renal masses. Evidence synthesis: Contrast-enhanced ultrasound (CEUS) adds significant diagnostic value, particularly for cystic renal masses, by improving the characterization of fine septations and small nodules, with a sensitivity and specificity comparable to magnetic resonance imaging (MRI). Additionally, the performance of CEUS for the classification of benign versus malignant renal masses is comparable to that of computed tomography (CT) and MRI, although the imaging features of different tumor subtypes overlap significantly. Ultrasound molecular imaging with targeted contrast agents is being investigated in preclinical research as an addition to CEUS. Elastography for the assessment of tissue stiffness and micro-Doppler imaging for the improved detection of intratumoral blood flow without the need for contrast are both being investigated for the characterization of renal masses, though few studies have been conducted and validation is lacking. Conclusions: Several novel ultrasound-based techniques have been investigated for the non-invasive characterization of renal masses. CEUS has several advantages over traditional grayscale ultrasound, including the improved characterization of cystic renal masses and the potential to differentiate benign from malignant renal masses to some extent. Ultrasound molecular imaging offers promise for serial disease monitoring and the longitudinal assessment of treatment response, though this remains in the preclinical stages of development. While elastography and emerging micro-Doppler techniques have shown some encouraging applications, they are currently not ready for widespread clinical use.

Role of contrast-enhanced ultrasound in assessing indeterminate renal lesions and Bosniak ≥2F complex renal cysts found incidentally on CT or MRI

OBJECTIVE

To investigate the impact of contrast-enhanced ultrasound (CEUS) in reclassifying incidental renal findings categorized as indeterminate lesions (IL) or Bosniak ≥ 2F complex renal cysts (CRC) on CT or MRI.

METHODS

We retrospectively included 44 subjects who underwent CEUS between 2016 and 2019 to assess 48 IL (n = 12) and CRC (n = 36) incidentally found on CT or MRI. CEUS was performed by one radiologist with 10 year of experience with a sulfur hexafluoride-filled microbubble contrast agent. The same radiologist, blinded to clinical information and previous CT/MRIs, retrospectively reviewed CEUS images/videos, categorizing renal findings with Bosniak-derived imaging categories ranging from 0 (indeterminate) to 5 (solid lesion). CEUS-related reclassification rate was calculated (proportion of IL reclassified with an imaging category >0, or CRC reclassified below or above imaging category >2F). Using histological examination or a ≥ 24 months follow-up as the standard of reference, we also estimated per-lesion sensitivity/specificity for malignancy.

RESULTS

CEUS reclassified 24/48 findings (50.0%; 95% C.I. 35.2-64.7), including 12/12 IL (100%; 95% CI 73.5-100) and 12/36 CRC (33.3%; 95% C.I. 18.5-50.9), mostly above category >2F (66.7%). CEUS and CT/MRI showed 96.0% (95%CI 79.7-99.9) vs 44.0% (95%CI 24.4-65.1) sensitivity, and 82.6% (95%CI 61.2-95.1) vs 60.9% (95%CI 38.5-80.3%) specificity.

CONCLUSION

CEUS provided substantial and accurate reclassification of CT/MRI incidental findings.

ADVANCES IN KNOWLEDGE

Previous studies included Bosniak 2 incidental findings, thus possibly underestimating CEUS-induced reclassification rates. Using a more meaningful cut-off (Bosniak ≥2F), problem-solving CEUS was effective as well, with higher reclassification rates for CRC than in literature.

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.

Contrast-enhanced ultrasound (CEUS) imaging for active surveillance of small renal masses

PURPOSE

To assess the safety and efficacy of contrast-enhanced ultrasound (CEUS) imaging for monitoring small (< 4 cm) renal masses (SRM) in patients undergoing active surveillance (AS).

METHODS

We retrospectively selected all consecutive patients with SRMs who underwent AS for at least 6 months at our Institution between January 2014 and December 2018. CEUS imaging was performed by two experienced genitourinary radiologists at established time points. The accuracy of CEUS for monitoring SRM size was compared with that of CT scan. For solid SRMs, four enhancement patterns (EP) were recorded. Radiological progression was defined as SRM growth rate ≥ 5 mm/year.

RESULTS

Overall, 158/1049 (15.1%) patients with SRMs underwent AS. At a median follow-up of 25 months (IQR 13-39), no patient died due to renal cell carcinoma (RCC). No patients experienced CEUS-related adverse events. There was a large variability in the pattern of growth of SRMs (overall median growth rate: 0.40 mm/year), with 9.5% of SRMs showing radiological progression. The median SRM size was comparable between CEUS and CT scan examinations at all time points. The vast majority (92.7%) of SRMs did not show a change in their EP over time; and there was no association between the SRM's EP and radiological progression or SRM size. Overall, 43 (27.2%) patients underwent delayed intervention (DI); median SRM size, and median growth rate were significantly higher in these patients as compared to those continuing AS.

CONCLUSION

In experienced hands, CEUS is a safe and effective strategy for active monitoring of SRMs in well-selected patients undergoing AS.

Routine or enhanced imaging to differentiate between type 1 and type 2 papillary renal cell carcinoma

AIM

To investigate imaging features and differentiating qualities of type 1 and type 2 papillary renal cell carcinoma (pRCC) by different imaging techniques.

MATERIALS AND METHODS

From 2007 to 2019, 107 patients with type 1 pRCC (T1-pRCC) and 147 with type 2 pRCC (T2-pRCC) were included in this retrospective study. All patients underwent conventional ultrasound (US); some also underwent contrast-enhanced ultrasound (CEUS), contrast-enhanced computed tomography (CECT), or contrast-enhanced magnetic resonance imaging (CE-MRI). Tumour Fuhrman grade or World Health Organization (WHO)/International Society of Urological Pathology (ISUP) grade (after June 2016) and invasive ranges were recorded. The two types of pRCC were analysed and compared for imaging features including tumour position, size, margin, echo type, and colour Doppler flow imaging (CDFI) using US as well as enhanced features from CEUS, CECT, or CE-MRI.

RESULTS

T2-pRCC showed a higher Fuhrman grade (p<0.001) and greater propensity to invade extrarenal tissue (p<0.001) than T1-pRCC. On US imaging, T2-pRCC was more likely to be a cystic-solid lesion (p<0.001), and colour flow with a higher resistance index (RI; p=0.014) was more easily detected (p=0.001) in T2-pRCC than in T1-pRCC. Within contrast-enhanced examinations, more T2-pRCC lesions had blurred tumour borders (p=0.003), hypervascular characteristics (p=0.003), and heterogeneous enhancement (p<0.001) than those of T1-pRCC.

CONCLUSIONS

T2-pRCC manifests more aggressively than T1-pRCC. T2-pRCC has a higher proportion of hypervascular and heterogeneous enhancement than T1-RCC.

Contrast enhanced ultrasonography (CEUS) to detect abdominal microcirculatory disorders in severe cases of COVID-19 infection: First experience

In the hands of experienced examiners, the contrast enhanced sonography (CEUS) offers the possibility to analyze dynamic microcirculatory disturbances in real time dynamically without any risk for kidneys and thyroid gland even in severe progressing disease bedside. Based on severe COVID-19 infections, first experiences with abdominal CEUS examinations are presented. In the stage of an imminent organ failure with significantly reduced kidney and liver function, CEUS can be used to show a narrowing of the organ-supplying arteries, as well as a delayed capillary filling of vessels near the capsule, a regional reduced parenchymal perfusion or an inflammatory hyperemia with capillary hypercirculation. It is possible to quickly rule out organ infarction and to dynamically record the mesenteric arterial and venous blood flow.