Acoustic Radiation Force Impulse Quantification Research Articles

Measurement of Elasticity of Epifascial Tissues in Arm Lymphoedema Using Acoustic Radiation Force Impulse Quantification (ARFI-Q): our experience

Measurement of Elasticity of Epifascial Tissues in Arm Lymphoedema Using Acoustic Radiation Force Impulse Quantification (ARFI-Q): our experience

Ultrasound-based quantitative tools in predicting renal involvement in asymptomatic primary hyperparathyroidism

PurposeAsymptomatic primary hyperparathyroidism (aPHPT) has been recognized as a condition that can lead to renal complications. Timely identification of prognostic indicators for renal impairment holds the potential to facilitate proactive monitoring and treatment strategies in these patients. This study aims to investigate the utility of acoustic radiation force impulse (ARFI) imaging and renal resistive index (RRI), in identifying renal parenchymal and vascular changes in patients with aPHPT.MethodsForty-two patients with aPHPT and 42 controls matched for age, sex, and body mass index were included in the study. The presence of renovascular changes was evaluated by RRI measurement with Doppler ultrasonography, and the presence of renal parenchymal involvement was evaluated by ARFI quantification, given as shear wave velocity (SWV).ResultsIn aPHPT patients, both the mean RRI and mean SWV values exhibited substantial elevation compared to the control group (P < 0.001 for both). Significant associations were observed between SWV values and serum calcium, parathyroid hormone (PTH), and adenoma size within the patient group (P < 0.001, P < 0.001, P = 0.016, respectively). Similarly, the mean RRI demonstrated positive correlations with serum calcium and PTH levels in the patient group (P< 0.001, P = 0.011, respectively). Multivariate linear regression analysis underscored the connection between mean RRI and mean SWV values with serum calcium levels within the patient group. In addition, serum PTH levels affected mean SWV positively and significantly.ConclusionThe use of ARFI imaging and RRI measurements appears to hold potential in identifying renal involvement in patients with aPHPT.

Role of Acoustic Radiation Force Impulse Elastography in the Characterization of Focal Solid Hepatic Lesions.

Objective:The purpose of the study is to investigate the usefulness of acoustic radiation force impulse (ARFI) elastography in the characterization of focal solid liver lesions as benign, malignant, or metastatic using ARFI two-dimensional (2D) imaging and ARFI quantification (shear wave velocities [SWVs]).Materials and Methods:Sixty lesions were included in this study. The lesions were classified into three groups: Group I included benign lesions (n = 25), Group II included malignant lesions (n = 27), and Group III included metastatic lesions (n = 8). ARFI elastography was performed in all these patients using a Siemens ACUSON S 2000™ ultrasound machine. Stiffness and size of the lesions were assessed on ARFI 2D images in correlation with B-mode ultrasound images. SWVs were obtained in these lesions for the quantification of stiffness.Results:In ARFI 2D images, malignant lesions were predominantly stiffer and larger, while benign lesions were softer and similar in size (P < 0.05). The mean SWVs in benign, malignant, and metastatic lesions were 1.30 ± 0.35 m/s, 2.93 ± 0.75 m/s, and 2.77 ± 0.90 m/s, respectively. The area under receiver operating characteristic curve of SWV for differentiating benign from malignant lesions was 0.877, suggesting fair accuracy (95% confidence interval: 0.777–0.976); with a cutoff value of 2 m/s, showing sensitivity: 92%; specificity: 96%; positive predictive value: 96%; negative predictive value: 93% (P < 0.05). Statistically significant difference exists in SWV of benign and malignant or metastatic lesions.Conclusion:ARFI elastography with 2D imaging and quantification might be useful in the characterization of benign and malignant liver lesions.

Acoustic Radiation Force Impulse Quantification in the Evaluation of Thyroid Elasticity in Pediatric Patients With Hashimoto Thyroiditis

To evaluate the parenchymal elasticity of the thyroid gland with acoustic radiation force impulse imaging in pediatric patients with Hashimoto thyroiditis and to compare it with healthy volunteers. Twenty-six patients with Hashimoto thyroiditis and 26 healthy volunteers between 6 and 17 years were included. The shear wave velocity (SWV) values of both thyroid lobes in both groups were evaluated. The age and sex characteristics of the controls and patients with Hashimoto thyroiditis were similar. The SWV of the thyroid gland in patients with Hashimoto thyroiditis (mean ± SD, 1.67 ± 0.63 m/s) was significantly higher than that in the control group (1.30 ± 0.13 m/s; P < .001). There was no significant difference between the thyroid lobes in both groups. A receiver operating characteristic curve analyses showed an optimal cutoff value of 1.41 m/s, with 73.1% sensitivity, 80.8% specificity, a 79.2 % positive predictive value, and a 75.0% negative predictive value (area under the curve, 0.806; P < .001). In patients with Hashimoto thyroiditis, there was a positive correlation between the SWV values versus anti-thyroperoxidase (Pearson r = 0.46; P = .038). There were no correlations between age, body mass index, thyroid function test results, and anti-thyroglobulin values and versus SWV values. Also, no significant differences were seen between the groups for gland size, gland vascularity, and l-thyroxine treatment. Acoustic radiation force impulse elastography showed a significant difference in the stiffness of the thyroid gland between children with Hashimoto thyroiditis and the healthy group. Using acoustic radiation force impulse elastography immediately after a standard ultrasound evaluation may predict chronic autoimmune thyroiditis.

Diagnostic Value of Acoustic Radiation Force Impulse Quantification in the Differentiation of Benign and Malignant Thyroid Nodules.

The objective of this study was to evaluate the role of ultrasound elastography using acoustic radiation force impulse (ARFI) quantification in characterizing and differentiating malignant versus benign thyroid nodules. A total of 40 thyroid nodules were evaluated with conventional sonography and ultrasound elastography using ARFI quantification. The final diagnosis was obtained from histologic findings. A total of 14 malignant and 26 benign nodules were diagnosed on the basis of histologic examination. Majority of the malignant thyroid nodules demonstrated presence of intranodular vascular flow, hypoechoic echotexture, absent halo, irregular margins and microcalcifications. However, a considerable overlap was noted in the sonographic features of malignant and benign thyroid nodules. On ARFI quantification, the mean shear wave speed (SWS) values ( M ± SD) of malignant and benign thyroid nodules were 3.131 ± 0.921 m/s and 1.691 ± 0.513 m/s, respectively. A significant difference was observed between the mean SWS values of malignant thyroid nodules and benign thyroid nodules ( p < 0.0001). Applying a cutoff value of 2.53 m/s, the sensitivity, specificity, and the area under the receiver operating characteristic curve for the differentiation were 85.71%, 96.15%, and 0.922, respectively. ARFI quantification is a promising elastography technique that provides quantitative information about tissue stiffness. It provides additional information and complements sonography as an effective diagnostic tool in characterizing and differentiating benign from malignant thyroid nodules.

Acoustic Radiation Force Impulse Quantification in the Evaluation of Renal Parenchyma Elasticity in Pediatric Patients With Chronic Kidney Disease: Preliminary Results.

To evaluate renal parenchymal elasticity with acoustic radiation force impulse imaging in pediatric patients with chronic kidney disease (CKD) and compare with healthy volunteers. Thirty-eight healthy volunteers and 30 pediatric CKD patients were enrolled in this prospective study. The shear wave velocity (SW) values of both kidneys in CKD patients and healthy volunteers were evaluated. The mean SW in healthy volunteers was 2.21 ± 0.34 m/s, whereas the same value was 1.81 ± 0.49, 1.72 ± 0.63, 1.66 ± 0.29, 1.48 ± 0.37, and 1.23 ± 0.27 for stages 1, 2, 3, 4, and 5 in CKD patients, respectively. The SW was significantly lower for each stage in the CKD patients compared with healthy volunteers. Acoustic radiation force impulse could not predict the different stages of CKD, with the exception of stage 5. The cut-off value for predicting CKD was 1.81 m/s; at this threshold, sensitivity was 76.5% and specificity was 92.1% (area under the curve = 0.870 [95% confidence interval: 0.750-0.990]; P < .001). Interobserver agreement expressed as intraclass coefficient correlation was 0.65 (95% confidence interval: 0.34 to 0.83; P < .001). Acoustic radiation force impulse may be a potentially useful tool in detecting CKD in pediatric patients.

A preliminary study of skin ultrasound in diffuse cutaneous systemic sclerosis: Does skin echogenicity matter?

ObjectiveTo evaluate the usefulness of skin ultrasound and acoustic radiation force impulse (ARFI) quantification in diffuse cutaneous systemic sclerosis (dcSSc).Patients and methods28 patients with dcSSc, and 15 age gender matched normal controls were recruited. Skin echogenicity, thickness, and ARFI quantification were measured by ultrasound at 17 sites corresponding to the modified Rodnan skin score (mRSS) in each participant. Compared with controls, skin echogenicity of dcSSc patients was classified into isoechoic, hypoechoic, and hyperechoic. The skin thickness, ARFI quantification and mRSS were compared between isoechoic, hypoechoic, hyperechoic and controls.ResultsIn patients with dcSSc, the skin thickness increased as the echogenicity changed on the order of isoechoic, hypoechoic and hyperechoic. ARFI quantification was significantly higher in hyperechoic than isoechoic (p<0.001). The mRSS were significantly higher in hyperechoic and/or hypoechoic than isoechoic. For isoechoic patients and healthy controls, the skin echogenicity or thickness was no significant different, however, the ARFI quantification was significantly higher in isoechoic than controls.ConclusionSkin ultrasound is feasible for assessing the skin involvement in dcSSc. Skin echogenicity correlates with skin thickness, stiffness, and mRSS. ARFI quantification may be more sensitive to detect skin changes, compared with skin echogenicity and thickness.

Comparison between acoustic radiation force impulse quantification data and perfusion-CT parameters in hepatocellular carcinoma

ObjectiveTo find out, if ultrasound elastography of hepatocellular carcinoma (HCC) can predict patterns of tumor perfusion in volume perfusion computed tomography (VPCT). Material and methods25 consecutive patients (mean age, 68.9; range, 51–85 years) with liver cirrhosis suspected of HCC underwent VPCT and acoustic radiation force impulse (ARFI) elastography the same day. Quantitative elasticity values were registered, while blood flow (BF), blood volume (BV) and hepatic perfusion index (HPI) of the HCC lesions were calculated. Additionally, we identified histologic WHO grading, lesion size and localization. The Siemens Acuson S 3000 HELX-System with Virtual Touch™-Software and Siemens Somatom Definition Flash with Syngo® software were used. ResultsA total of 43 HCC lesions were assessed. Mean shear wave velocity was 2.6m/s (range, 1.1–4.3m/s). There was no significant linear correlation between the elasticity values and BF (p=0.751), BV (p=0.426) and HPI (p=0.437). However, elasticity values were higher, the larger the tumor was (p=0.008). Shear wave velocity declined with increasing distance of the HCC to the skin surface (p=0.028) and depending on liver segment. In addition, elasticity values were higher in less differentiated HCCs. This trend was not statistically significant (p=0.842). ConclusionTissue elasticity in HCC does not correlate with the degree of tumor vascularization, but calculated values are influenced both by the tumor size and localization inside the liver.

Anisotropic Properties of Breast Tissue Measured by Acoustic Radiation Force Impulse Quantification

The goal of our study was to investigate the anisotropy of normal breast glandular and fatty tissue with acoustic radiation force impulse (ARFI) quantification. A total of 137 breasts in 137 women were enrolled. These breasts were divided into the duct-apparent group and the duct-inapparent group, divided into the ligament-apparent group and the ligament-inapparent group. Shear wave velocity (SWV) in the radial (SWVr) and anti-radial (SWVa-r) directions was measured. The elastic anisotropy of glandular tissue and fatty tissue was evaluated as the ratio between SWVr and SWVa-r. The SWV ratio was 1.30 ± 0.45 for glandular tissue and 1.27 ± 0.53 for fatty tissue in the total group. In glandular tissue, the SWV ratio of the duct-apparent group was higher than that of the duct-inapparent group (p = 0.011). In both glandular and fatty tissue, the SWV ratio was higher in the ligament-apparent group than in the ligament-inapparent group (p < 0.05 for both). SWVr was higher than SWVa-r in both glandular tissue and fatty tissue in all groups (p < 0.05 for all) except in breast fatty tissue in the ligament-inapparent group (p = 0.913). It is concluded that both breast glandular tissue and fatty tissue exhibited anisotropy of elastic behavior. To improve the diagnostic power of elastography in breast lesions, the elastic anisotropy of glandular tissue and fatty tissue should be taken into account in calculating strain ratio or elasticity ratio.

Applications of acoustic radiation force impulse quantification in chronic kidney disease: a review.

Acoustic radiation force impulse (ARFI) imaging is an emerging technique with great promise in the field of elastography. Previous studies have validated ARFI quantification as a method of estimating fibrosis in chronic liver disease. Similarly, fibrosis is the principal process underlying the progression of chronic kidney disease, which is the major cause of renal failure. However, the quantification of tissue stiffness using ARFI imaging is more complex in the kidney than in the liver. Moreover, not all previous studies are comparable because they employed different procedures. Therefore, subsequent studies are warranted, both in animal models and in clinical patients, in order to better understand the histopathological mechanisms associated with renal elasticity and to further improve this imaging method by developing a standardized guidelines for its implementation.

SAT-436 - Liver Stiffness Measured by Acoustic Radiation Force Impulse Quantification in Primary Sclerosing Cholangitis: A Comparison with Transient Elastography Performed by Fibroscan® and Other Non-Invasive Tests

SAT-436 - Liver Stiffness Measured by Acoustic Radiation Force Impulse Quantification in Primary Sclerosing Cholangitis: A Comparison with Transient Elastography Performed by Fibroscan® and Other Non-Invasive Tests

The effect of applied transducer force on acoustic radiation force impulse quantification within the left lobe of the liver.

Introduction: Acoustic Radiation Force Impulse (ARFI) Quantification measures shear wave velocities (SWVs) within the liver. It is a reliable method for predicting the severity of liver fibrosis and has the potential to assess fibrosis in any part of the liver, but previous research has found ARFI quantification in the right lobe more accurate than in the left lobe. A lack of standardised applied transducer force when performing ARFI quantification in the left lobe of the liver may account for some of this inaccuracy. The research hypothesis of this present study predicted that an increase in applied transducer force would result in an increase in SWVs measured. Methods: ARFI quantification within the left lobe of the liver was performed within a group of healthy volunteers (n = 28). During each examination, each participant was subjected to ARFI quantification at six different levels of transducer force applied to the epigastric abdominal wall. Results: A repeated measures ANOVA test showed that ARFI quantification was significantly affected by applied transducer force (p = 0.002). Significant pairwise comparisons using Bonferroni correction for multiple comparisons showed that with an increase in applied transducer force, there was a decrease in SWVs. Conclusion: Applied transducer force has a significant effect on SWVs within the left lobe of the liver and it may explain some of the less accurate and less reliable results in previous studies where transducer force was not taken into consideration. Future studies in the left lobe of the liver should take this into account and control for applied transducer force.

A preliminary study of acoustic radiation force impulse quantification for the assessment of skin in diffuse cutaneous systemic sclerosis.

To investigate skin elasticity using acoustic radiation force impulse (ARFI) quantification in systemic sclerosis (SSc), and compare the modified Rodnan skin score (mRSS) with measured shear wave velocity (SWV) and thickness of the skin. Fifteen patients with diffuse cutaneous SSc (dcSSc) and 15 age-matched and sex-matched healthy controls were evaluated. The SWV and thickness of skin were measured at 17 sites corresponding to those assessed in the mRSS in each participant. The SWV measurements of skin were compared between patients with dcSSc and healthy controls. The correlations between the mRSS and the skin SWV and thickness were explored using Spearman's correlation. The SWV values were higher in patients with dcSSc compared with healthy controls at right hand dorsum, right forearm, left hand dorsum, left forearm, right foot dorsum, and left foot dorsum (p < 0.05). In patients with dcSSc, the SWV values of uninvolved skin were higher than those of controls (p < 0.001), and the SWV values increased with increasing skin scores except for skin score 3 (p < 0.05). The sum of the SWV values correlated with total clinical skin score (r = 0.841, p < 0.001), and the sum of the skin thickness correlated with total clinical skin score (r = 0.740, p = 0.002). ARFI quantification is feasible and reliable for assessing the skin involvement in dcSSc. ARFI quantification could identify early skin change that may precede palpable skin involvement, and may be a valuable adjunct to skin evaluation in patients with SSc.

Acoustic radiation force impulse quantification of spleen elasticity for assessing liver fibrosis.

The purpose of this study is to assess the correlation between liver fibrosis and spleen stiffness measured by ARFI in patients with chronic viral hepatitis (B or C) and to explore the possible complementary role of spleen and liver ARFI in grading liver fibrosis. 84 subjects (51 patients, 33 healthy volunteers) were enrolled. ARFI of the spleen and the liver was performed. Patients subsequently underwent liver biopsy for grading liver fibrosis according to Knodell scoring system. Multivariate logistic regression and decision tree analysis were adopted to test the relationship between spleen and liver stiffness (independent variables) and liver fibrosis (F1< vs. ≥F3). Leave-One-Out Cross-Validation was used for validating the predictive classification models. Area under the ROC curve (AUROCC) was used as accuracy metric. Spleen ARFI was able to discriminate early (F1) from severe (≥F3) liver fibrosis with an optimal cut-off of 3.05 m/s: AUROCC 0.807, cross-validated AUROCC 0.614. Liver ARFI was superior to spleen ARFI, using a cut-off of 2.11 m/s: AUROCC 0.879, cross-validated AUROCC 0.672. Neither spleen nor liver ARFI was able to differentiate healthy volunteers from F1 patients. Odds ratios derived from logistic regression were 23.1 and 9.9 for liver and spleen ARFI, respectively; resulting AUROCC was 0.905 (cross-validated 0.848). A decision tree considering the sequential use of liver and spleen ARFI with cut-off of 2.14 and 3.39 m/s, respectively, resulted in AUROCC of 0.903 (cross-validated 0.7). Spleen ARFI has the potential to discriminate early from severe liver fibrosis. Spleen and liver ARFI, when combined, show a better discriminative power than liver ARFI alone.

ASSESSING THE ROLE OF ACOUSTIC RADIATION FORCE IMPULSE IMAGING TO PREDICT THE STAGING OF LIVER FIBROSIS IN PATIENTS WITH NONALCOHOLIC STEATOHEPATITIS

Background/Objectives: Acoustic radiation force impulse (ARFI) is a novel non-invasive technology for the assessment of stages of liver fibrosis in chronic hepatic disease. Some studies previously reported that ARFI is a promising method for assessing liver fibrosis in patients with NAFLD/NASH. This study aimed to validate the diagnostic usefulness of ARFI for prediction of staging of liver fibrosis in patients with NASH. Patients and Methods: The study was carried out on 51 patients with NASH. All of patients underwent a liver biopsy for histological assessment of liver fibrosis and ARFI elastography. Cut-off values were determined using receiver-operating characteristic (ROC) curves. Results: Histological liver fibrosis was evaluated by Metavir scoring; F0: 8 cases, F1: 29 cases, F2: 10 cases and F3: 4 cases. ARFI quantification correlated significantly with the fibrosis stage (Spearman rho: 0.44, p &lt;0.05). The areas under the ROC curves (AUROC) were 0.75 (95% confidence intervals: 0.60-0.90) for ≥F2 and 0.78 (0.53-0.99) for F3. The cut-off values of the shear wave velocity (SWV) were as follows: ≥1.29 m/s for ≥F2 (sensitivity 64.3%, specificity 83.8%, PPV 60% and NPV 86.1%), ≥ 1.38 m/s for F3 (sensitivity 75%, specificity 89.4%, PPV 57.5%, NPV 97.7%). Conclusions: Increasing ARFI velocities correlate with high degree of liver fibrosis. ARFI has quite good accuracy and high specificity, NPV for prediction of significant and advanced fibrosis in patients with NASH. The method should be employed routinely in the workup of patients with NASH to exclude the presence of significant and advanced liver fibrosis. Key words: liver fibrosis, liver stiffness, non-alcoholic fatty liver disease (NAFLD), nonalcoholic steatohepatitis (NASH), acoustic radiation force impulse imaging (ARFI).

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

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

SAT0213 Is Acoustic Radiation Force Impulse (ARFI) Quantification A Useful Noninvasive Method for Assessing Salivary Glands?

BackgroundThe ARFI method is a new tool to evaluate the stiffness of soft tissues which is is wellknown for evaluating the stiffness of liver parenchyma. No studies have been done...

Assessment of renal tissue elasticity by acoustic radiation force impulse quantification with histopathological correlation: preliminary experience in chronic kidney disease

Chronic kidney disease (CKD), a progressive and irreversible pathological syndrome, is the major cause of renal failure. Renal fibrosis is the principal process underlying the progression of CKD. Acoustic radiation force impulse (ARFI) quantification is a promising noninvasive method for assessing tissue stiffness. We evaluated whether the technique could reveal renal tissue fibrosis in CKD patients. ARFI assessments were performed in 45 patients with CKD referred for renal biopsies to measure cortical shear wave velocity (SWV). During measurement, a standardized method was employed, which aimed to minimize the potential impact of variation of transducer force, sampling error of non-cortical tissue and structural anisotropy of the kidney. Then SWV was compared to patients' CKD stage and pathological fibrosis indicators. ARFI could not predict the different stages of CKD. Spearman correlation analysis showed that SWV did not correlate with any pathological indicators of fibrosis. ARFI assesses tissue stiffness of CKD kidneys by measuring cortical SWV. However, SWV did not show significant correlations with CKD stage and fibrosis indicators despite using standardized measurement methods. We therefore suggest that it would be necessary to evaluate the effect of pathological complexity and tissue perfusion of the kidney on stiffness assessment in future studies. • Acoustic radiation force impulse (ARFI) can quantify tissue elasticity of CKD kidney. • Despite standardized measurement, ARFI-estimated elasticity did not correlate with renal fibrosis. • Effects of pathological complexity and tissue perfusion on renal stiffness warrant further study.

Tissue Elasticity Quantification by Acoustic Radiation Force Impulse for the Assessment of Renal Allograft Function

Acoustic radiation force impulse (ARFI) quantification, a novel ultrasound-based elastography method, has been used to measure liver fibrosis. However, few studies have been performed on the use of ARFI quantification in kidney examinations. We evaluated renal allograft stiffness using ARFI quantification in patients with stable renal function (n = 52) and those with biopsy-proven allograft dysfunction (n = 50). ARFI quantification, given as shear wave velocity (SWV), was performed. The resistance index (RI) was calculated by pulsed-wave Doppler ultrasound, and clinical and laboratory data were collected. Morphologic changes in transplanted kidneys were diagnosed by an independent pathologist. Mean SWV was more significantly negatively correlated with estimated glomerular filtration rate (eGFR) (r = –0.657, p < 0.0001) than was RI (r = –0.429, p = 0.0004) in transplanted kidneys. Receiver operating characteristic curve analysis revealed that the sensitivity and specificity of quantitative ultrasound in the diagnosis of renal allograft dysfunction were 72.0% and 86.5% (cutoff value = 2.625), respectively. The latter values were better than those of RI, which were 62.0% and 69.2% (cutoff value = 0.625), respectively. The coefficient of variation for repeat SWV measurements of the middle part of transplanted kidney was 8.64%, and inter-observer agreement on SWV was good (Bland-Altman method, ICC = 0.890). In conclusion, tissue elasticity quantification by ARFI is more accurate than the RI in diagnosing renal allograft function.

Virtual Analysis of Pancreatic Cystic Lesion Fluid Content by Ultrasound Acoustic Radiation Force Impulse Quantification

The purpose of this study was to prospectively evaluate the application of acoustic radiation force impulse (ARFI) imaging implemented with Virtual Touch tissue quantification (Siemens AG, Erlangen, Germany) in the study of pancreatic cystic lesions by using different analysis methods compared with the final diagnosis (pathologic or by magnetic resonance imaging and endoscopic sonographic findings). Thirty-eight patients with pancreatic cystic focal lesions (diameter >3 cm and located at a depth of 5.5 cm) were included in the study and underwent conventional sonography. For every patient, 5 measurements in the Virtual Touch tissue quantification region of interest were obtained. To distinguish mucinous (potentially malignant) from serous (mainly benign) cystic lesions, the result XXXX/0 was considered to mean simple liquids (comparable to water), and the accuracy of Virtual Touch tissue quantification in differentiating pancreatic cystic lesions was calculated. To consider a lesion as containing complex fluids (potentially mucinous), two different reading methods were applied: (1) at least 2 numerical values when obtaining 5 measurements; and (2) the prevalence of numerical values irrespective of the number of measurements. The sensitivity, specificity, positive and negative predictive values, and accuracy were calculated for the differential diagnosis between mucinous and nonmucinous cystic lesions. By the first reading method, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy in the group of cystic lesions were 68.8%, 77.3%, 68.8%, 77.3%, and 73.7%, respectively; by the second method, the values were 37.5%, 100%, 100%, 68.8%, and 73.3%. Acoustic radiation force impulse imaging with Virtual Touch tissue quantification can have a role in the noninvasive characterization of pancreatic cystic lesions during conventional sonographic examinations.