Real-time elastography for distinguishing angiomyolipoma from renal cell carcinoma: preliminary observations

Predictors of Benignity for Small Endophytic Echogenic Renal Masses

OBJECTIVES

To evaluate for distinguishing demographic and sonographic features of small (<3 cm) endophytic angiomyolipomas (AMLs) that differentiate them from endophytic renal cell carcinomas (RCCs).

METHODS

This is a Health Insurance Portablitiy and Accountablity Act (HIPAA)-compliant retrospective review of the demographics and ultrasound features of endophytic renal AMLs compared to a group of endophytic RCCs. AMLs were confirmed by identifying macroscopic fat on computed tomography (CT) or magnetic resonance imaging (MRI), while RCCs were pathologically proven. Statistical analysis was used to compare findings in the 2 groups.

RESULTS

There were a total of 66 patients with 66 AMLs, and 28 patients with 28 RCCs. Of the AMLs, 57 of 66 were in females, while 10 of the 28 RCC cases were in females (P < .0001). The mean AML long and short diameters were 11.0 × 9.3 mm and were statistically significantly smaller (P < .0001) than the diameters of the RCCs (23.4 × 22.1 mm). Likewise, the ratio of the long axis to the short axis measurement was statistically significantly different between the 2 groups (P < .0001). Of the studied sonographic features, statistically different features between AMLs and RCCs included an oval versus a round shape (P < .001), respectively, and the presence versus absence of an echogenic margin, respectively. Location of the mass, mass homogeneity, mass lobulation, and presence of cystic components were not distinguishing features using P < .01 levels.

CONCLUSION

For an endophytic echogenic mass in a female patient, a small size with an oval shape and an echogenic margin is statistically more likely to be an AML than an RCC, which may be helpful with management decisions.

The role of strain wave elastography in the evaluation of renal fibrosis in patients with kidney diseases

BACKGROUND

A renal biopsy represents the gold standard in the diagnosis, prognosis and management of patients with chronic kidney disease and glomerulonephritis. Strain wave elastography (SE) is a developing technique to assess tissue elasticity. The aim of this study was to correlate between the strain index value of renal parenchyma and degree of renal fibrosis detected with renal biopsy.

METHOD

For 68 patients who were referred for a kidney biopsy, SE test was performed. The Banff scoring system was utilized to classify the IFTA grading of kidney fibrosis that assigns a severity level of mild, moderate, or severe. Receiver operating characteristic curve (ROC) was utilized to correlate between the severity of renal fibrosis and the grade of renal elasticity determined by SE.

RESULTS

In total, 38 males and 30 females, the echogenicity, qualitative and semiquantitative elastography showed significant positive correlation with serum creatinine, percentage of fibrosis, G score and tubular atrophy and significant negative correlation with eGFR. ROC curve of SE for diagnosis of interstitial fibrosis shown that echogenicity has sensitivity 100.0%, specificity 62.5%, positive predictive value (PPV) 75.0%, negative predictive value (NPV) 100.0% with area under curve (AUC) 0.906, while qualitative elastography has sensitivity 77.8%, specificity 75.0%, PPV 77.8%, NPV 75.0%, AUC 0.833, semi quantitative elastography has sensitivity 83.3%, specificity 93.8%, PPV 93.8%, NPV 83.3% with AUC 0.915.

CONCLUSION

SE approach is simple to use, and can differentiate between varying stages of renal fibrosis. However, further research is required before it can be frequently used in clinical practice.

Application value of strain elastography in testicular injury assessment after torsion

Aim

To evaluate the capability of strain elastography (SE) in assessing the degree of testicular injury after torsion.

Material and methods

In total, 50 rabbits were divided into four groups according to different degrees of testicular torsion (TT) at 0°, 180°, 360°, and 720°. For each animal, according to the tissue stiffness distribution, an SE score and strain ratio (SR) were obtained. With the histopathological results as the reference, the correlation coefficients of the apoptotic index and SE score or SR were calculated, and the receiver operating characteristic (ROC) curves were created to assess the capability of SE in assessing the degree of testicular injury.

Results

A significant positive correlation was found between the apoptotic index and SE score, as well as the SR, with corresponding correlation coefficients of 0.70 (<0.001) and 0.68 (P = 0.001), respectively. The areas under the ROC curves (AUCs) of the SE score and SR for identifying ischemia/hypoxia injury were found to be 0.81 (95% CI, 0.71-0.93) and 0.73 (95% CI, 0.60-0.86), respectively. For identifying irreversible damage, the AUCs were 0.69 (95% CI, 0.56-0.83) and 0.71 (95% CI, 0.59-0.84) for the SE score and SR, respectively.

Conclusions

SE scores exhibited good diagnostic capability for detecting ischemia/hypoxia injury after TT. In early identification of severe injury/necrosis following TT, SE demonstrated some value but was not ideal.

Comparing the effect of FUAS and myomectomy on the elasticity of myometrium around targeted uterine fibroid

BACKGROUND

Focused ultrasound ablation surgery (FUAS) has been widely employed to treat patients with uterine fibroid (UF). This study aimed to estimate myometrial stiffness changes in patients who received FUAS for UFs or myomectomy (ME) and compare the recovery of surrounding myometrium between FUAS and ME groups. Our results may provide more evidence for guiding the proper conception timing in patients with UF.

METHODS

This study enrolled 173 patients from May 2022 to August 2023. Shear wave elastography (SWE) was used to dynamically monitor myometrial elasticity changes in patients before and after surgery. Moreover, our study monitored and analyzed the stiffness changes in the targeted fibroid after FUAS, as well as in the myometrium around after FUAS or ME.

RESULTS

The stiffness of the myometrium around the resected fibroid was significantly higher than at the preoperative level until 6 months. Conversely, the stiffness of the surrounding myometrium was only temporarily increased 1 day after FUAS. The comparison between FUAS and ME groups regarding the stiffness of the surrounding myometrium showed that nonsignificant differences were detected between the two groups before the treatment. The stiffness of the surrounding myometrium in the ME group was statistically significantly higher than that of the FUAS group 1 day as well as 1, 3, and 6 months after the treatment, respectively.

CONCLUSION

The FUAS had less impact on the surrounding myometrium than the ME, which may be more conducive to the recovery of myometrial elasticity in patients with UF.

Are There Ultrasound Features to Distinguish Small (<3 cm) Peripheral Renal Angiomyolipomas From Renal Cell Carcinomas?

BACKGROUND

Small echogenic renal masses are usually angiomyolipomas (AMLs), but some renal cell carcinomas (RCCs) can be echogenic and confused with an AML.

OBJECTIVES

This is a study to evaluate any distinguishing demographic and sonographic features of small (<3 cm) peripheral AMLs versus peripheral RCCs.

METHODS

This is a HIPAA-compliant retrospective review of the demographics and ultrasound features of peripheral renal AMLs compared with a group of peripheral RCCs. All AMLs had confirmation of macroscopic fat as noted on thin-cut CT or fat-saturation MRI sequence images. All RCCs were pathologically proven. Statistical analysis was used to compare findings in the two groups.

RESULTS

There were a total of 52 patients with 56 AMLs, compared with 42 patients with 42 RCCs. There were 42 females in the AML group versus 10 females in the RCC group (P < .0001). The AML diameters (15.7 mm × 12.0 mm) were statistically significantly smaller (Plargest  = .0085, Psmallest  < .001) than the diameters of the RCCs (19.9 mm × 18.5 mm). Ultrasound features found to be statistically different between the two groups were the ratio of the largest dimension to the smallest dimension (P < .001), a lobulated versus smooth margin of the AML (26 vs 30) compared with the RCC group (3 vs 39) (P = .0012), and an "unusual" versus a round shape (P < .001) of the AML group (45 vs 11) compared with the RCC group (9 vs 33). In the multivariable model, the patient sex, margin, and mass shape were predictive of AML, with an area under the receiver operating characteristic curve of 0.92.

CONCLUSION

For a small (<3 cm) peripheral echogenic mass in a female patient, a lobulated lesion with an unusual shape is highly predictive of being an AML.

Characterization of uterine involution using B-mode ultrasonography, color Doppler and elastography (acoustic radiation force impulse) for assessing postpartum in Santa Inês ewes

The aim of this study was to investigate uterine involution using ultrasonography techniques during postpartum. Postpartum ultrasonography evaluation (B-mode, color Doppler and Acoustic Radiation Force Impulse elastography) of the uterus was performed by transabdominal approach at immediate after birth and sequentially every 48 hours, during 30 days. The uterine echotexture did not present significant variations (P >0.05) being homogeneous in most evaluations; echogenicity of the uterus increased along the evaluation period (P =0.0452). Progressive and remarkable decrease of the total uterine diameter (UD) were observed (P <0.0001), especially during the first days postpartum. The thickness of uterine wall gradually decreased, as well the endometrial, myometrium and lumen diameters (P <0.0001). Uterine blood flow was assessed by Doppler and decreased during postpartum period, being significantly lower (P=0.0225) on the 30^th day of postpartum. Uterine parenchyma presented as homogeneous dark areas (not deformable) on qualitative ultrasound elastography and the means shear velocity values of the uterine wall on quantitative elastography did not differ. This is the first study that evaluate the stiffness of uterine wall in healthy ewes, providing baseline data about quantitative and qualitative stiffness of the normal uterus, and it may be a useful tool for early diagnosis of uterine alterations during the postpartum period, using the reference parameter established for the assessment of uterine integrity during postpartum period.

Diagnostic performance of the "drooping" sign in CT diagnosis of exophytic renal angiomyolipoma

OBJECTIVE

To evaluate the prevalence of angular interface and the "drooping" sign in exophytic renal angiomyolipomas (AMLs) and the diagnostic performance in differentiating exophytic lipid-poor AMLs from other solid renal masses.

METHODS

This IRB-approved, two-center study included 185 patients with 188 exophytic solid renal masses < 4 cm with histopathology and pre-operative CT within 30 days of surgical resection or biopsy. Images were reviewed for the presence of angular interface and the "drooping" sign qualitatively by three readers blinded to the final diagnosis, with majority rules applied. Both features were assessed quantitatively by cohort creators (who are not readers) independently. Free-marginal kappa was used to assess inter-reader agreement and agreement between two methods assessing each feature. Fisher's exact test, Mann-Whitney test, and multivariable logistic regression with two-tailed p < 0.05 were used to determine statistical significance. Diagnostic performance was assessed.

RESULTS

Ninety-four patients had 96 AMLs, and 91 patients had 92 non-AMLs. Seventy-four (77%) of AMLs were lipid-poor based on quantitative assessment on CT. The presence of angular interface and the "drooping" sign by both qualitative and quantitative assessment were statistically significantly associated with AMLs (39% (qualitative) and 45% (quantitative) vs 15% (qualitative) and 13% (quantitative), and 48% (qualitative) and 43% (quantitative) vs 4% (qualitative) and 1% (quantitative), respectively, all p < 0.001) in univariable analysis. In multivariable analysis, only the "drooping" sign in either qualitative or quantitative assessment was a statistically significant predictor of AMLs (both p < 0.001). Inter-reader agreement for the "drooping" sign was moderate (k = 0.55) and for angular interface was fair (k = 0.33). Agreement between the two methods of assessing the "drooping" sign was substantial (k = 0.84) and of assessing the angular interface was moderate (k = 0.59). The "drooping" sign both qualitatively and quantitatively, alone or in combination of angular interface, had very high specificity (96-100%) and positive predictive value (PPV) (89-100%), moderate negative predictive value (62-68%), but limited sensitivity (23-49%) for lipid-poor AMLs.

CONCLUSION

The "drooping" sign by both qualitative and quantitative assessment is highly specific for lipid-rich and lipid-poor AMLs. This feature alone or in combination with angular interface can aid in CT diagnosis of lipid-poor AMLs with very high specificity and PPV.

Shear wave elastography in the characterization of renal cell carcinoma and angiomyolipoma

BACKGROUND

Detection and characterization of renal lesions are common in daily clinical practice.

PURPOSE

To investigate the effectiveness of shear wave elastography (SWE), a novel radiological examination technique, in the characterization of renal masses.

MATERIAL AND METHODS

The study included a total of 68 patients (33 men, 35 women; mean age = 57.71 ± 12.08 years; age range = 19-83 years) who underwent SWE. SWE measurements were obtained at depths of 2-8 cm from the probe surface in two different positions from an analysis window of approximately 0.5 × 1.0 cm on ultrasound. The cutoff SWE was calculated for the differentiation of renal cell carcinoma (RCC) and angiomyolipoma (AML) by receiver operating characteristic (ROC) analysis. When the result was statistically significant, the sensitivity, specificity, accuracy, and positive and negative predictive values of the test were calculated.

RESULTS

Mass-to-parenchyma SWE ratios of RCCs were significantly higher than those of AMLs (P = 0.003). In ROC curve analysis, the SWE cutoff was 1.215 m/s to differentiate RCCs from AMLs. The area under the ROC curve was calculated as 0.74 (95% CI = 0.610-0.871, sensitivity = 70.7%, specificity = 70.6%, positive predictive value = 87.8%, negative predictive value = 44.4%).

CONCLUSION

The SWE technique is increasingly used and may be useful in distinguishing RCC and AML lesions, and especially clear cell and non-clear cell RCCs.

Elastography in the Urological Practice: Urinary and Male Genital Tract, Prostate Excluded—Review

The aim of this article is to review the utility of elastography in the day-to-day clinical practice of the urologist. An electronic database search was performed on PubMed and Cochrane Library with a date range between January 2000 and December 2021. The search yielded 94 articles that passed the inclusion and exclusion criteria. The articles were reviewed and discussed by organ, pathology and according to the physical principle underlying the elastographic method. Elastography was used in the study of normal organs, tumoral masses, chronic upper and lower urinary tract obstructive diseases, dysfunctions of the lower urinary tract and the male reproductive system, and as a pre- and post-treatment monitoring tool. Elastography has numerous applications in urology, but due to a lack of standardization in the methodology and equipment, further studies are required.

Role of shear wave elastography in predicting the metabolic and androgenic alterations in patients with polycystic ovary syndrome

AIM

To evaluate the variation in tissue stiffness caused by the changes in ovarian volume and stroma in polycystic ovary syndrome (PCOS) using a novel method of ultrasonography, that is shear wave elastography (SWE). The current study also aimed to evaluate the potential applications of this method in predicting the metabolic and androgenic alterations in patients with PCOS.

METHODS

The present study included 33 patients with PCOS. The blood samples for the metabolic and androgenic parameters and SWE values pertaining to the patients were obtained on the same day during the early follicular phase. The predictive ability of SWE to reflect the metabolic and androgenic abnormalities was evaluated using the receiver operating characteristic curve (ROC) analysis.

RESULTS

The mean SWE value pertaining to the group with higher total testosterone levels was significantly lower, compared to the group with normal testosterone levels (p = 0.041). The ROC analysis revealed that the predictive potential of SWE was statistically significant in regard to the serum testosterone levels alone (area under the curve [AUC] = 0.755, 95% confidence interval [CI]: 0.573-0.938, p = 0.041). There was no significant relationship between the SWE values and metabolic parameters.

CONCLUSIONS

Based on the results of the present study, decreased SWE values appear to be associated with increased serum testosterone levels. However, the present study did not observe any significant relationship between the SWE values and metabolic parameters. SWE can be used as a practical and non-invasive method to predict the serum testosterone levels during the follow-up evaluations of the patients with PCOS.

Circularity Index on Contrast-Enhanced Computed Tomography Helps Distinguish Fat-Poor Angiomyolipoma from Renal Cell Carcinoma: Retrospective Analyses of Histologically Proven 257 Small Renal Tumors Less Than 4 cm

OBJECTIVE

To evaluate circularity as a quantitative shape factor of small renal tumor on computed tomography (CT) in differentiating fat-poor angiomyolipoma (AML) from renal cell carcinoma (RCC).

MATERIALS AND METHODS

In 257 consecutive patients, 257 pathologically confirmed renal tumors (either AML or RCC less than 4 cm), which did not include visible fat on unenhanced CT, were retrospectively evaluated. A radiologist drew the tumor margin to measure the perimeter and area in all the contrast-enhanced axial CT images. In each image, a quantitative shape factor, circularity, was calculated using the following equation: 4 × π × (area ÷ perimeter²). The median circularity (circularity index) was adopted as a representative value in each tumor. The circularity index was compared between fat-poor AML and RCC, and the receiver operating characteristic (ROC) curve analysis was performed. Univariable and multivariable binary logistic regression analysis was performed to determine the independent predictor of fat-poor AML.

RESULTS

Of the 257 tumors, 26 were AMLs and 231 were RCCs (184 clear cell RCCs, 25 papillary RCCs, and 22 chromophobe RCCs). The mean circularity index of AML was significantly lower than that of RCC (0.86 ± 0.04 vs. 0.93 ± 0.02, p < 0.001). The mean circularity index was not different between the subtypes of RCCs (0.93 ± 0.02, 0.92 ± 0.02, and 0.92 ± 0.02 for clear cell, papillary, and chromophobe RCCs, respectively, p = 0.210). The area under the ROC curve of circularity index was 0.924 for differentiating fat-poor AML from RCC. The sensitivity and specificity were 88.5% and 90.9%, respectively (cut-off, 0.90). Lower circularity index (≤ 0.9) was an independent predictor (odds ratio, 41.0; p < 0.001) for predicting fat-poor AML on multivariable logistic regression analysis.

CONCLUSION

Circularity is a useful quantitative shape factor of small renal tumor for differentiating fat-poor AML from RCC.

The effect of maternal vitamin D levels on placental shear wave elastography findings in the first trimester

The aim of this study was to investigate the effect of maternal serum Vitamin D levels on the elasticity of placenta. Seventy-four spontaneously conceived singleton pregnancies in their first trimester were enrolled into this study. Fifty-one of them had Vitamin D deficiency (<20 ng/mL), while 23 pregnancies had Vitamin D levels ≥20 ng/mL. The placental elasticity was measured by the transabdominal Point Shear Wave Elastography (pSWE) method. In each case, the mean of 10 consecutive measurements was accepted as the mean placental elasticity value. The mean pSWE values did not significantly differ between the Vitamin D deficient group and the control group (p > .05). Placental elasticity was not found to be different in the pregnancies with Vitamin D deficiency during the first trimester.IMPACT STATEMENTWhat is already known on this subject? The pSWE technique provides opportunity to determine the elasticity of any interested tissue. Placental elasticity has been found to be changed in inflammatory and fibrotic conditions such as in preeclampsia, intrauterine growth restriction or diabetes. On the other hand, Vitamin D deficiency is linked with several comorbidities such as autoimmune disorders, cancer and cardiovascular disorders. Vitamin D also plays a role in placental angiogenesis in the first trimester. Maternal Vitamin D levels are shown to be related with adverse pregnancy outcomes.What do the results of this study add? To the best of our knowledge, this study is the first assessing the association between Vitamin D levels and placental elasticity. Placental elasticity was not found to be changed by Vitamin D deficiency.What are the implications of these findings for clinical practice and/or further research? Our pilot study revealed that Vitamin D deficiency does not have any impact on placental elasticity in the first trimester. However, longitudinal studies concerning placental elasticity in subsequent trimesters are needed to support our findings.

Differential diagnosis of <3 cm renal tumors by ultrasonography: a rapid, quantitative, elastography self-corrected contrast-enhanced ultrasound imaging mode beyond screening

OBJECTIVES

To assess the combined diagnostic strategy of contrast-enhanced ultrasound (CEUS) and acoustic radiation force impulse (ARFI) in the precise differential diagnosis of clear cell renal cell carcinoma (CCRCC) and urothelium carcinoma of the renal pelvis (UCRP) with other small renal tumors (SRTs) ＜3 cm in size.

METHODS

The elastography self-corrected CEUS (ESC) mode was established to perform the quantitative differential diagnosis of SRTs (<3 cm). The kidney shear wave velocity (SWV) value recorded by ARFI showed substantial variability in patients with CCRCC (high elasticity value) and UCRP (low elasticity value) compared with other renal masses, thus providing critical self-correction information for the ultrasound differential diagnosis of SRTs.

RESULTS

In this work, the ESC observations and the corresponding ESC criteria show a remarkable 94.6% accuracy in reference to the gold standards, thus allowing the quantitative, early triple distinction of CCRCC with UCRP and other SRTs in patients with suspicious SRTs.

CONCLUSIONS

This ARFI self-corrected CEUS diagnostic strategy is far beyond a screening method and may have the potential to identify a window of therapeutic opportunity in which emerging therapies might be applied to patients with CCRCC and UCRP, reducing overtreatment and medical costs.

ADVANCES IN KNOWLEDGE

In our study, a new rapid and non-invasive elastography self-corrected CEUS (ESC) ultrasound imaging mode was developed, which was useful in the triple distinction of CCRCC, UCRP, and other SRTs with 94.6% accuracy. ESC is a promising method in the differential diagnosis of SRTs with accuracy and practicability far beyond a single screening model.

Assessment of the optic nerve using strain and shear-wave elastography in patients with pseudotumour cerebri

AIM

To evaluate the optic nerve using strain elastography (SE) and shear-wave elastography (SWE) in idiopathic intracranial hypertension (IIH) patients in comparison to participants in the control group.

MATERIALS AND METHODS

Eighty eyes were evaluated in 40 cases consisting of 20 IIH patients and 20 participants in the control group. This study was conducted using SE and SWE in addition optic nerve sonography measurements of participants in the IIH patient group and the control group. SE patterns were categorised using three main types and two subtypes. Quantitative measurements of optic nerve stiffness with SWE were expressed in kilopascals.

RESULTS

In the IIH patient group, type 2 and type 1 elasticity patterns were primarily observed, followed by type 3 patterns. In the control group, type 3 elasticity patterns were most often observed, while type 2 elasticity patterns were seen less frequently. Statistically significance differences in the types of elasticity strain patterns were observed between the groups (p<0.01). Quantitative analysis was also performed, and the SWE moduli were obtained for the control group (10.1±0.28 kPa) and the IIH patient group (26.97±1 kPa). A statistically significant difference in the SWE modulus was found between the groups (p<0.01).

CONCLUSION

Biomechanical changes may have occurred in the optic nerve secondary to increased intracranial pressure in IIH patients. Strain and shear elastography may have potential as assistive diagnostic techniques for the detection and follow-up of these changes.

Intra-rater reliability and smallest detectable change of compression sonoelastography in quantifying the material properties of the musculoskeletal system

Musculoskeletal conditions can change tissue elasticity. Knowledge of musculoskeletal elasticity could therefore aid clinical diagnosis and management. Sonoelastography is an ultrasound-based system that examines the material properties of tissues, and it may be useful in musculoskeletal practice. Therefore, it is important to establish its clinimetric properties. This study aimed to explore the intra-rater reliability and the smallest detectable changes of sonoelastography in examining musculoskeletal structures. A quantitative reliability design was used to examine 22 healthy participants using a compression sonoelastography system that produces color-coded images. The deltoid, biceps brachii, brachioradialis, rectus femoris, gastrocnemius medius muscles, and Achilles tendon were examined twice at 1-hr intervals to assess the intra-rater reliability. The sonoelastography images were analyzed using the strain index, strain ratio, and color pixels. The intra-rater reliability and the smallest detectable changes of each outcome variable were determined. The intra-class correlation coefficient was used to quantify the repeatability of the measurements, and the smallest detectable changes were calculated to determine clinically important differences above the error of measurement. The intra-rater reliability for the strain index, strain ratio, and color pixel analysis ranged from moderate to excellent (intra-class correlation coefficients: .734-.950, .776-.921, and .754-.990, respectively), with color pixel analysis demonstrating the highest reliability. The smallest detectable changes were determined for all structures, including the Achilles tendon (0.11 for the higher boundary of the strain index, 1.80 for the strain ratio, and 2.90% for red pixels, representing soft tissues). Color pixel analysis may be more reliable for sonoelastography interpretation compared with the strain index and strain ratio. The calculated smallest detectable changes could be used to identify clinically important differences.

Placental elasticity assessment by point shear wave elastography in pregnancies with intrauterine growth restriction

Background Placental elasticity varies in different diseases. Our objective was to evaluate placental elasticity using point shear wave elastography (pSWE) in pregnancies with intrauterine growth restriction (IUGR). Methods A total of 66 pregnant women with IUGR and 81 healthy pregnant women were enrolled. Placental elasticity was measured using the transabdominal pSWE method. Ten measurements were made, and the mean was accepted as the mean placental elasticity value in each case. The results for IUGR pregnancies and controls were compared. Results The mean pSWE values were significantly higher in pregnancies with IUGR, which means that women with IUGR have stiffer placentas (P < 0.001). Furthermore, the pSWE values were significantly and positively correlated with Doppler indices and adverse perinatal outcomes. Conclusion The pregnancies with IUGR had stiffer placentas than the healthy controls. The utilization of pSWE for placental elasticity may be useful in the diagnosis and management of IUGR as a supplement to the existing ultrasonography methods.

Diagnostic Performance of Ultrasound Shear Wave Elastography in Solid Small (≤4 cm) Renal Parenchymal Masses

The aim of the study was to analyze the diagnostic performance of shear wave elastography (SWE) in differentiating between malignant and benign solid renal parenchymal masses ≤4 cm, compared with conventional ultrasound. A total of 20 healthy volunteers and 117 patients had been included in this study. Conventional ultrasound and SWE were performed in all volunteers and patients. The elasticity of healthy cortex and the elastic parameters of tumors such as mean elasticity (E_mean), minimum elasticity (E_min), maximum elasticity (E_max), standard deviation and elasticity ratio of the lesion to surrounding cortex (E_ratio) were measured on SWE images. Diagnostic performance of SWE was compared with that of conventional ultrasound. The cortical elasticity values of healthy right and left kidneys were 4.7 ± 1.7 and 4.5 ± 1.5 kPa, respectively. Of the 117 renal tumors, 68 were renal cell carcinomas (RCCs) and 49 were benign. E_mean, E_min and E_ratio were significantly lower in RCCs compared with benign lesions: E_mean 7.2 ± 2.5 kPa versus 10.0 ± 2.4 kPa, E_min 2.5 ± 2.4 kPa versus 5.6 ± 2.3 kPa, E_ratio 1.6 ± 0.5 versus 2.2 ± 0.6 (all p values < 0.001). The cutoff values of 9.15 kPa for E_mean, 3.55 kPa for E_min and 1.99 for E_ratio had the highest areas under the receiver operating characteristics curve (0.801 for E_mean, 0.832 for E_min and 0.806 for E_ratio). Combining E_mean, E_min and E_ratio with conventional ultrasound improved the specificity for predicting RCCs to 87.8%, but the sensitivity was not increased.

Point Shear Wave Elastography Using Machine Learning to Differentiate Renal Cell Carcinoma and Angiomyolipoma

The question of whether ultrasound point shear wave elastography can differentiate renal cell carcinoma (RCC) from angiomyolipoma (AML) is controversial. This study prospectively enrolled 51 patients with 52 renal tumors (42 RCCs, 10 AMLs). We obtained 10 measurements of shear wave velocity (SWV) in the renal tumor, cortex and medulla. Median SWV was first used to classify RCC versus AML. Next, the prediction accuracy of 4 machine learning algorithms-logistic regression, naïve Bayes, quadratic discriminant analysis and support vector machines (SVMs)-was evaluated, using statistical inputs from the tumor, cortex and combined statistical inputs from tumor, cortex and medulla. After leave-one-out cross validation, models were evaluated using the area under the receiver operating characteristic (ROC) curve (AUC). Tumor median SWV performed poorly (AUC = 0.62; p = 0.23). Except logistic regression, all machine learning algorithms reached statistical significance using combined statistical inputs (AUC = 0.78-0.98; p < 7.1 × 10-3). SVMs demonstrated 94% accuracy (AUC = 0.98; p = 3.13 × 10-6) and clearly outperformed median SWV in differentiating RCC from AML (p = 2.8 × 10-4).

Characterization of Small Renal Tumors With Magnetic Resonance Elastography: A Feasibility Study

OBJECTIVES

The aim of this study was to explore the feasibility of magnetic resonance elastography (MRE) for characterizing indeterminate small renal tumors (SRTs) as part of a multiparametric magnetic resonance (MR) imaging protocol.

MATERIALS AND METHODS

After institutional review board approval and informed consent were obtained, 21 prospective adults (15 men; median age, 55 years; age range, 25-72 years) with SRT were enrolled. Tumors (2-5 cm Ø) were imaged using 3-directional, gradient echo MRE. Viscoelastic parametric maps (shear wave velocity [c] and attenuation [α]) were analyzed by 2 independent radiologists. Interobserver agreement (Bland-Altman statistics and intraclass correlation coefficients) was assessed. Anatomical T2-weighted, dynamic contrast-enhanced (DCE) and diffusion sequences completed the acquisition protocol. Imaging parameters were compared between groups (Mann-Whitney U test).

RESULTS

Quality of MRE was good in 18 cases (mean nonlinearity <50%), including 1 papillary renal cell carcinoma and 1 metanephric adenoma. A cohort of 5 oncocytomas and 11 clear-cell renal cell carcinomas (ccRCCs) was analyzed for statistical differences. The MRE viscoelastic parameters were the strongest imaging discriminators: oncocytomas displayed significantly lower shear velocity c (median, 0.77 m/s; interquartile range [IQR], 0.76-0.79) (P = 0.007) and higher shear attenuation α (median, 0.087 mm; IQR, 0.082-0.087) (P = 0.008) than ccRCC (medians, 0.92 m/s and 0.066 mm; IQR, 0.84-0.97 and 0.054-0.074, respectively). T2 signal intensity ratio (tumor/renal cortex) was lower in oncocytomas (P = 0.02). The DCE and diffusion MR parameters overlapped substantially (P ≥ 0.1). Oncocytomas displayed a consistent MRE viscoelastic profile, corresponding to data point clustering in a bidimensional scatter plot. Values for MRE intraclass correlation coefficient were 0.982 for c and 0.984 for α, indicating excellent interobserver agreement.

CONCLUSIONS

Magnetic resonance elastography is feasible for SRT characterization; MRE viscoelastic parameters were stronger discriminators between oncocytoma and ccRCC than anatomical, DCE and diffusion MR imaging parameters.

Morphologic analysis with computed tomography may help differentiate fat-poor angiomyolipoma from renal cell carcinoma: a retrospective study with 602 patients

PURPOSE

To assess whether morphologic analysis using computed tomography (CT) could differentiate between fat-poor angiomyolipoma (fpAML) and renal cell carcinoma (RCC).

METHODS

A total of 602 patients with a histologically confirmed fpAML (n = 49) or RCC (n = 553) were evaluated. All renal lesions were less than 4 cm in size and had no gross fat on contrast-enhanced CT. For morphologic analysis, overflowing beer sign and angular interface were evaluated. Overflowing beer sign was defined as contact length between bulging-out portion of a mass and the adjacent renal capsule of 3 mm or greater. Angular interface was defined as the angle of parenchymal portion of a mass of 90° or less. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were assessed. Multivariate analysis was conducted to determine which variable is predictive of fpAML.

RESULTS

Sensitivity, specificity, PPV, NPV, and accuracy were 61.2% (30/49), 97.1% (537/553), 65.2% (30/46), 96.6% (537/556), and 94.2% (567/602) with overflowing beer sign, while they were 55.1% (27/49), 81.9% (453/553), 21.3% (27/127), 95.4% (453/475), and 79.7% (480/602) with angular interface for fpAML, respectively. Both CT variables were predictive of fpAML (overflowing beer sign, odds ratio = 132.881, p < 0.001; angular interface, odds ratio = 5.766, p = 0.010). The multivariate model with CT variables showed good performance for predicting fpAML (AUC, 0.871 with angular interface, 0.943 with overflowing beer sign, and 0.949 with both).

CONCLUSION

Morphologic analysis with contrast-enhanced CT may be useful for differentiating fpAML from RCC. Overflowing beer sign has the potential as an imaging biomarker for fpAML.

Evaluation of the diagnostic efficacy of strain elastography in infertile population with normal and abnormal semen parameters

OBJECTIVE

The aim of the present study was to investigate the diagnostic value of strain elastography (SE) of testicular tissues in infertile population. We also evaluated the correlation between SE results with semen parameters and hormone profiles of the patients.

MATERIAL AND METHODS

A total of 61 patients and 122 testes were evaluated. Patients who were evaluated in an andrology outpatient clinic with the diagnosis of infertility and referred to radiology department for investigation of reproductive organs between June 2015 and January 2016 were included. Patients were divided into two groups according to semen analyses results as normal (Group 1) and abnormal (Group 2). Hormone profiles, semen analyses, B-mode, coloured Doppler ultrasonography and sonoelastography examinations were performed for each patient. Measurements of testicular volumes, resistive indices (RI) in intraparenchymal arteries, strain, strain ratio (SR) and presence of varicocele were recorded.

RESULTS

Mean age of participants was 33.7±6.3 years. Mean testicular volumes (Group 1, 19.41±4.8 mL, and Group 2, 17.64±3.62 mL) were significantly different between groups (p=0.023). Mean SRs were also different between Groups 1 and 2 (0.12±0.08 vs. 0.22±0.18, p<0.001). Testicular volumes were directly proportional with SRs in Group 1. Strain values had inverse relationship with sperm concentration and total motile sperm counts in Group 2 (p=0.01). SRs were found to be positively correlated with RI and sperm morphology in Group 2 (p<0.05). Although FSH values showed significant difference among groups, any correlation between FSH and elastographic parameters could not be displayed.

CONCLUSION

Strain elastography results were found to be significantly different in patients with abnormal sperm counts. This technique may provide promising results, however, further large scale studies may help to clarify the value of this imaging modality in the assessment of male infertility.

Evaluation of Optic Nerve with Strain and Shear Wave Elastography in Patients with Behçet's Disease and Healthy Subjects

The objective of this study was to investigate the elasticity characteristics of the optic nerve using strain and shear wave elastography in patients with Behçet's disease and to compare the results with those of healthy volunteers. Forty-six optic nerves from patients with Behçet's disease and 54 optic nerves from healthy volunteers were investigated prospectively in this study using strain and shear wave elastography. There was a statistically significant difference in terms of elasticity patterns between patients and healthy volunteers (p < 0.001). Elastographic images of healthy volunteers revealed most optic nerves to be type 3 (51.8%); however, type 2 (40.7%) and type 1 (7.5%) were also observed. Elastographic examination of Behçet's disease patients revealed type 2 in 52.2%, type 1 in 43.5% and type 3 in 4.3% of patients. Statistically significant differences were observed between patients and healthy volunteers in the analysis of shear wave elastography values (p < 0.001). Receiver operating characteristic curve analysis was perfect (0.933) (95% CI = 0.885-0.980), and a cutoff value of 16.5 kPa shear had very high sensitivity and specificity for the patient group. Strain and shear wave elastography findings for the optic nerves of patients with Behçet's disease were significantly different from those for healthy volunteers.

Ultrasound Elastography: Review of Techniques and Clinical Applications

Elastography-based imaging techniques have received substantial attention in recent years for non-invasive assessment of tissue mechanical properties. These techniques take advantage of changed soft tissue elasticity in various pathologies to yield qualitative and quantitative information that can be used for diagnostic purposes. Measurements are acquired in specialized imaging modes that can detect tissue stiffness in response to an applied mechanical force (compression or shear wave). Ultrasound-based methods are of particular interest due to its many inherent advantages, such as wide availability including at the bedside and relatively low cost. Several ultrasound elastography techniques using different excitation methods have been developed. In general, these can be classified into strain imaging methods that use internal or external compression stimuli, and shear wave imaging that use ultrasound-generated traveling shear wave stimuli. While ultrasound elastography has shown promising results for non-invasive assessment of liver fibrosis, new applications in breast, thyroid, prostate, kidney and lymph node imaging are emerging. Here, we review the basic principles, foundation physics, and limitations of ultrasound elastography and summarize its current clinical use and ongoing developments in various clinical applications.

Contribution of real-time elastography in diagnosis of polycystic ovary syndrome

PURPOSE

We aimed to assess the feasibility and reproducibility of real-time elastography (RTE) for displaying the effects of morphological changes in the ovary in polycystic ovary syndrome (PCOS).

METHODS

Forty-eight patients diagnosed with PCOS and 48 healthy women were enrolled in the study. Ultrasonography and RTE were performed on the 3rd day of the menstrual cycle. Evaluations were performed independently by two radiologists. Ovarian volume, number of follicles, elasticity pattern, and strain ratio were measured. Elasticity patterns were assessed as hard (type 1; blue or blue-green), moderate (type 2; green or green-yellow) or soft (type 3; red or orange-red).

RESULTS

Both radiologists determined the elasticity pattern as mostly type 1 in the PCOS group and type 3 in the control group (P < 0.01). The mean strain ratios obtained by the first and second radiologist were 6.1±1.8 (2.7-10.1) and 6.0±1.5 (3.0-9.0) in PCOS and 3.3±1.2 (1.7-7.2) and 3.2±0.9 (1.7-6.8) in the control group, respectively (P < 0.001). Interobserver agreement was moderate for the elasticity pattern (κ=0.48) and good for the strain ratio (intraclass correlation coefficient, 0.77). A strain ratio of 3.8 was determined as the optimized cutoff point by receiver operating curve analysis. Strain ratio was correlated with the ovarian volume and the number of detected follicles (P < 0.001).

CONCLUSION

Elasticity pattern and strain ratio can help identify morphological changes that make PCOS ovaries stiffer than normal ovaries.

Role of Strain Elastography in the Evaluation of Testicular Torsion: An Experimental Study

OBJECTIVES

To evaluate the utility of real-time strain elastography in experimentally induced testicular torsion at different degrees and torsion hours.

METHODS

Thirty-one Wistar albino rats were divided into 4 torsion groups by twisting left testes (group I, sham operated; group II, 360°; group III, 720°; and group IV, 1080°). Elastography was applied at the 8th and 24th hours of torsion. Elasticity patterns (pattern 1, soft testis; pattern 2, moderately soft testis; pattern 3, predominantly hard testis; and pattern 4, almost entirely hard testis) and strain ratios were recorded. Histopathologic evaluation was done at the 24th hour. Interobserver agreement was analyzed.

RESULTS

Changes in elastographic patterns and strain ratios among groups II, III, and IV were statistically significant at both hours as determined by both radiologists (P < .01). Elastographic patterns changed from 2 to 3 in groups II and III to 4 in group III between the 8th and 24th hours (P < .05), but in group IV, patterns were reversed, and pattern 1 was observed at both hours. Pathologically severe necrosis (grade 4) was seen in left testes in group IV. In the other groups, pathologic grading in the left testes was as follows: mostly grade 1 in groups I and II and mostly grade 2 in group III. Elastography showed that right testes were affected in group IV, with significant differences in elastographic patterns and strain ratios (P < .01). Interobserver agreement for elastographic patterns in right testes was substantial at the 8th hour (κ = 0.72) and otherwise excellent (κ = 0.81-0.85). Concordance of strain ratios between observers was excellent for right and left testes at the 8th and 24th hours (intraclass correlation coefficients, 0.990 at the 8th hour and 0.987 at the 24th hour).

CONCLUSIONS

Our results show that real-time strain elastography can be a complementary method in the evaluation of testicular tissue in testicular torsion and can guide surgeons in their surgical approach.

Comparison of placental elasticity in normal and pre-eclamptic pregnant women by acoustic radiation force impulse elastosonography

AIM

The aim of this research was to study and compare placental elasticity with acoustic radiation force impulse (ARFI) elastography in pre-eclamptic and normal pregnancies.

METHODS

A total of 107 singleton pregnancies in the third trimester (38 healthy control subjects, 34 patients with gestational hypertension, and 35 pre-eclampsia patients) were included in the study. ARFI elastography was used to determine the placental elasticity in the three predetermined regions of the placenta (the fetal edge, maternal edge, and central part of the placenta). The obstetrical data regarding grayscale and Doppler ultrasonography and perinatal outcomes were reviewed. A mean placental shear wave velocity cut-off value that predicts the presence of pre-eclampsia was determined.

RESULTS

The shear wave elasticity values in the pre-eclampsia group in all three regions were significantly higher than in the gestational hypertension and healthy control groups (P = 0.001). The most significant difference was found in the peripheral edge of the placenta from the fetal surface in the pre-eclampsia group (P = 0.001).

CONCLUSION

The stiffness of the placenta determined by the ARFI technique is significantly higher in pre-eclampsia patients. ARFI elastography of the placenta might be used as a non-invasive and easy method in the diagnosis and evaluation of pre-eclampsia as a supplement to the already existing methods.

Diagnostic value of strain elastography for differentiation between renal cell carcinoma and transitional cell carcinoma of kidney

PURPOSE

The objective of our study was to prospectively evaluate the diagnostic performance of strain elastography for differentiation between renal cell carcinomas (RCCs) and transitional cell carcinomas (TCCs) of kidney.

METHODS

A total of 99 consecutive patients who were referred to our hospital because of a newly diagnosed solid renal mass suspicious for malignancy on radiological screenings were evaluated with sonography, including strain elastography. Strain elastography was used to compare the stiffness of the renal masses and renal cortex. The ratio of strain in a renal mass and nearby renal cortex was defined as the strain index value. Mean strain index values for RCCs and TCCs were compared, and mean strain index values between histological subtypes of RCC were also compared.

RESULTS

Although TCCs were smaller than RCCs (p < 0.001), there were no significant differences in gender distribution and mean age of the patients, and mean probe-tumor distance between RCC and TCC. The mean strain index value ±SD for TCC (5.18 ± 1.12) was significantly higher than the value for RCC (4.04 ± 0.72; p < 0.001). Mean strain index value for papillary cell carcinomas (4.09 ± 0.45) was slightly higher than that for clear cell carcinomas (3.85 ± 0.78): however, the difference was not statistically significant (p = 0.51).

CONCLUSIONS

Strain elastography can be used as a valuable imaging technique for preoperative differentiation between RCC and TCC of kidney.

Renal Cell Carcinomas: Sonographic Appearance Depending on Size and Histologic Type

OBJECTIVES

Prior studies have demonstrated that approximately 10% of malignant renal cell carcinomas are as echogenic as angiomyolipomas on sonography. However, a recent presentation suggested that small (<1-cm) echogenic renal masses are always angiomyolipomas or other benign entities. We therefore examined our own cases of renal cell carcinoma, with corresponding sonography, to confirm that some renal cell carcinomas may also be detected as hyperechoic masses on sonography.

METHODS

Institutional Review Board approval and Health Insurance Portability and Accountability Act compliance were maintained for this retrospective review of 91 pathologically proven cases of renal cell carcinoma, with corresponding sonography. Tumors were first differentiated by histologic cell type (clear cell, papillary, and chromophobe). Tumors were then stratified according to 2 size group parameters, falling into those that were 3 cm or larger and those that were smaller than 3 cm in diameter, with the less than 3-cm group further subdivided into 2 cm or smaller and greater than 2 cm. Tumor echogenicity was graded on a 5-point scale with respect to the renal parenchyma.

RESULTS

Forty-six tumors (51%) were 3 cm in diameter or smaller, and most were found to be either isoechoic (35%) or mildly hyperechoic (26%) to the surrounding renal parenchyma. Of tumors smaller than 2 cm, most were either mildly hyperechoic (29%) or as hyperechoic as renal sinus fat (very hyperechoic; 29%). Tumors larger than 3 cm were found most often to be either isoechoic (49%) or mildly hyperechoic (33%), with only 4% found to be very hyperechoic.

CONCLUSIONS

The sonographic appearances of renal cell carcinomas include a small population that are very hyperechoic on sonography and thus could potentially be misdiagnosed as angiomyolipomas.

Renal Cell Carcinoma Metastasis to Ipsilateral Parotid and Submandibular Glands: Report of a Case with Sonoelastographic Findings

Background

Renal cell carcinoma (RCC) – also known as hypernephroma or grawitz tumor – accounts for 3% of the adulthood malignancies. Approximately 30–40% of the patients have metastasis at the time of the diagnosis and most common sites for metastasis are lung, regional lymph nodes, bone and liver. A total of 8–14% of the patients with RCC has head and neck metastasis. However, metastasis to major salivary glands is rarely seen. In this paper, we aimed to report a RCC case with metastasis to parotid and submandibular glands that has the same sonographic and sonoelastographic findings with the primary tumor.

Case Report

66-year old woman with RCC history was referred to our radiology department for neck ultrasound (US) with painful swelling in the right parotid gland region. A well-defined, 37×21 mm sized hypoechoic heterogeneous solid mass was detected in the superficial-deep lobe of the right parotid gland. The mass was prominently hypervascular in color Doppler ultrasonography scan. Coincidentally, a 13×13 mm hypoechoic lobulated solid mass was detected in the right submandibular gland with similar sonographic findings.

Real-time sonoelastography (SEL) was performed to the masses and both of them were blue-green colored that indicates hard tissue. An US and SEL evaluation was also performed to the renal mass (RCC) of the patient. The primary mass was also similar in sonographic and SEL appearance as salivary gland masses. In the patient history, she revealed chemotherapy-radiotherapy treatment 1.5 years ago due to inoperable mass in the mid-lower pole of the left kidney diagnosed as clear cell RCC with vascular invasion, liver, lung and brain metastasis. Because of known primary tumor, the masses in the salivary glands were suspected to be metastatic and a tru-cut biopsy was performed. Pathological result was reported as clear cell RCC metastasis.

Conclusions

The etiology of RCC is still unknown and metastatic involvement can be seen at unexpected tissue and organs. Metastatic disease should be considered when a salivary gland mass detected in patients with RCC history. SEL examination would be helpful in differentiation of the origin of the metastatic lesion with known SEL features.

Clinical application of sonoelastography in thyroid, prostate, kidney, pancreas, and deep venous thrombosis

This article reviews the clinical applications of current ultrasound elastography methods in non-hepatic conditions including thyroid nodules, prostate cancer, chronic kidney disease, solid renal lesions, pancreatic lesions, and deep vein thrombosis. Pathophysiology alters tissue mechanical properties via ultrastructural changes including fibrosis, increased cellularity, bleeding, and necrosis, creating a target biomarker, which can be imaged qualitatively or quantitatively with US elastography. US elastography methods can add information to conventional US methods and improve the diagnostic performance of conventional US in a range of disease processes.

Elastography: history, principles, and technique comparison

Elastography is a relatively new imaging technology that creates images of tissue stiffness. It can be thought of an extension of the ancient technique of palpation but it gives better spatial localization information and is less subjective. Two main types of elastography are currently in use, strain elastography where the tissue displacement in response to gentle pressure is used to compute and image tissue strain, and shear wave elastography where the speed of shear waves traversing tissue is measured and used to create an image of tissue stiffness. Each method has advantages and disadvantages but generally strain imaging is excellent for focal lesions and shear wave imaging, being more quantitative, is best for diffuse organ diseases. Strain imaging requires additional training in acquisition technique to obtain high quality images. Pitfalls to avoid and tips for good images are provided. Improvements in strain imaging are focused on better quality indicators and better methods for quantification. Improvements in shear wave imaging will be higher frame rates, greater accuracy in focal lesions, and making results more comparable between different ultrasound systems. Both methods will continue to improve and will provide ever more powerful new tools for diagnosis of diffuse and focal diseases.

Interventional treatment of renal angiomyolipoma: immediate results and clinical and radiological follow-up of 4.5 years

BACKGROUND

Renal angiomyolipoma is rare, but many of these patients may have an acute debut with severe bleeding. These patients need urgent treatment with interventional embolization as an attractive option.

PURPOSE

To investigate the technical and clinical effect of this treatment and to evaluate long-term clinical outcomes with clinical control and radiological imaging.

MATERIAL AND METHODS

Eight patients with angiomyolipoma were treated with embolization. Five patients were treated acutely. Five patients were followed-up for mean 4.5 years with clinical and radiological examinations.

RESULTS

The renal angiomyolipoma decreased significantly from mean 7.2 cm to 2.9 cm after embolization (p = 0.04). Cortical infarctions of about one-third of the circumference of the embolized kidneys could be detected on follow-up examinations, but all patients had normal total kidney function. The bleeding was primarily stopped in all patients, however, in one patient bleeding from a lumbar artery was supplementary embolized within 24 h. In another case the interventional procedure ended up in embolization of the whole kidney as it was impossible to embolize all the feeding arteries selectively. One patient had a nephrectomy one month after embolization because of infection and re-bleeding and one patient after 2.5 years because of tumor size >4 cm. The technical success was 7/8 (88%) and clinical success was 6/8 patients (75%).

CONCLUSION

Selective embolization of renal angiomyolipoma is a minimally invasive and safe procedure with few complications. It is a nephron sparing alternative to renal resection. The reduction in tumor size after embolization is significant and long-lasting.

Real-Time Elastography in the Follow-Up of Fibromatosis Colli

Fibromatosis colli is a rare disease related to congenital muscular torticollis that responds well to therapy if diagnosed and treated early. Gray-scale ultrasonography is used for diagnosis and follow-up, but with limitations. A novel technique, real-time elastography, might prove helpful for evaluating the response to therapy. A case is presented of fibromatosis colli diagnosed with sonography and real-time elastography in the first month of life. The baby was treated with physiotherapy for 3 months, and therapy was ended on the basis of real-time elastographic findings. Real-time elastography has been shown to be useful in the diagnosis and follow-up to physiotherapy for fibromatosis colli.

Utility of semiquantitative strain elastography for differentiation between benign and malignant solid renal masses

OBJECTIVES

The aim of this study was to determine the role of semiquantitative strain elastography for differentiation of benign and malignant solid renal masses.

METHODS

Seventy-one patients with solid renal masses were prospectively examined with ultrasound elastography after grayscale sonography. Strain elastography was used to compare the stiffness of the renal masses and renal parenchyma. The ratio of strain in a renal mass and nearby renal parenchyma was defined as the strain index value. Mean strain index values for benign masses (n = 29; 24 angiomyolipomas and 5 oncocytomas) and malignant masses (n = 42; 34 renal cell carcinomas, 4 transitional cell carcinomas, 3 metastases, and 1 lymphoma) and mean strain index values for angiomyolipomas and renal cell carcinomas were compared.

RESULTS

There were no significant differences in the mean age of the patients, mean diameter of the masses, and mean probe-mass distance between benign and malignant groups. The mean strain index value ± SD for malignant masses (4.05 ± 2.17) was significantly higher than the value for benign masses (1.43 ± 0.94; P < .05). The mean strain index value for renal cell carcinomas (4.30 ± 2.27) was significantly higher than the value for angiomyolipomas (1.28 ± 1.01; P < .0001).

CONCLUSIONS

Strain elastography may be a useful imaging technique for differentiation between benign and malignant solid renal masses.

Strain elastography in the characterization of renal cell carcinoma and angiomyolipoma

INTRODUCTION

We evaluate the diagnostic performance of strain elastography to differentiate renal cell carcinoma (RCC) from angiomyolipoma (AML).

METHODS

Strain elastography was performed in 65 patients (mean age 55.5 years; range: 32-81) who had renal lesions (24 AMLs and 41 RCCs) prospectively. Lesions were classified according to lesion size and histological subtypes. The strain ratios of the RCCs and AMLs were evaluated by a radiologist. The area under the curve and the cut-off point were used to assess diagnostic performance. Sensitivity, specificity, and positive and negative predictive values were obtained.

RESULTS

In assessing the mean strain ratio, we divided the groups in 3 according to size: (1) <20-mm lesions; (2) 20- to 40-mm lesions; and (3) >40-mm lesions; the respective mean strain ratios were: 1.5 ± 0.5 (range: 0.06-5.92), 2.8 ± 0.4 (range: 0.17-9.92), 2.7 ± 0.3 (range: 0.08-6.15). When RCCs and AMLs were compared, there was a statistically significant difference in the strain ratio among the 3 groups divided per lesion size (p < 0.01). For the strain ratio, the mean ± standard deviation was 1.1 ± 0.1 for AMLs and 3.4 ± 0.3 for RCCs (p < 0.01). When lesion subtypes were compared, there was a statistically significant difference in the strain ratio between the AML and clear cell RCC (p < 0.01).

CONCLUSIONS

For assessing renal lesions, strain elastography and strain ratio values may be useful in differentiating RCCs from AMLs.

Imaging findings of common benign renal tumors in the era of small renal masses: differential diagnosis from small renal cell carcinoma: current status and future perspectives

The prevalence of small renal masses (SRM) has risen, paralleling the increased usage of cross-sectional imaging. A large proportion of these SRMs are not malignant, and do not require invasive treatment such as nephrectomy. Therefore, differentation between early renal cell carcinoma (RCC) and benign SRM is critical to achieve proper management. This article reviews the radiological features of benign SRMs, with focus on two of the most common benign entities, angiomyolipoma and oncocytoma, in terms of their common imaging findings and differential features from RCC. Furthermore, the role of percutaneous biopsy is discussed as imaging is yet imperfect, therefore necessitating biopsy in certain circumstances to confirm the benignity of SRMs.

The role of quantitative measurement by acoustic radiation force impulse imaging in differentiating benign renal lesions from malignant renal tumours

PURPOSE

The purpose of this preliminary study was to prospectively evaluate the diagnostic performance of acoustic radiation force impulse (ARFI) imaging for differentiating benign lesions from malignant renal tumours.

MATERIALS AND METHODS

Sixty patients with renal lesions were enrolled in the study; mean patient age was 49.52 ± 20.46 years (range 1-83 years) and patients included 30 men and 30 women. Lesions were categorised as benign (n = 19), malignant (n = 36) and infectious (n = 5) in origin. The shear wave velocities (SWVs) of the tumours and the intact parenchyma were determined by ARFI quantification, and the differences in the SWVs were compared among groups. The final diagnoses were determined via pathologic (n = 33), clinical (n = 13) and imaging findings (n = 14). The SWV values of the renal tumours were analysed according to the final diagnoses.

RESULTS

The mean SWV value of the normal renal parenchyma was significantly different from that of all other lesions (p < 0.01). There was a significant difference between the SWV values of benign renal lesions including haematomas and the malignant renal lesions (p = 0.033). However, the SWV values of the infectious lesions and leiomyoma corresponded well with the malignant lesions. A Receiver operating characteristic (ROC) analysis demonstrated a cut-off value of 2.34 m/s between benign and malignant lesions, while sensitivity and specificity were determined to be 88 and 54 %, respectively.

CONCLUSION

ARFI elastography with ARFI quantification may be useful for differentiating benign renal lesions from malignant renal tumours.