Acoustic Radiation Force Impulse Quantification Research Articles

Acoustic Radiation Force Impulse Elastography for Focal Hepatic Tumors: Usefulness for Differentiating Hemangiomas from Malignant Tumors

ObjectiveThe purpose of this study is to investigate whether acoustic radiation force impulse (ARFI) elastography with ARFI quantification and ARFI 2-dimensional (2D) imaging is useful for differentiating hepatic hemangiomas from malignant hepatic tumors.Materials and MethodsOne-hundred-and-one tumors in 74 patients were included in this study: 28 hemangiomas, 26 hepatocellular carcinomas (HCCs), three cholangiocarcinomas (CCCs), 20 colon cancer metastases and 24 other metastases. B-mode ultrasound, ARFI 2D imaging, and ARFI quantification were performed in all tumors. Shear wave velocities (SWVs) of the tumors and the adjacent liver and their SWV differences were compared among the tumor groups. The ARFI 2D images were compared with B-mode images regarding the stiffness, conspicuity and size of the tumors.ResultsThe mean SWV of the hemangiomas was significantly lower than the malignant hepatic tumor groups: hemangiomas, 1.80 ± 0.57 m/sec; HCCs, 2.66 ± 0.94 m/sec; CCCs, 3.27 ± 0.64 m/sec; colon cancer metastases, 3.70 ± 0.61 m/sec; and other metastases, 2.82 ± 0.96 m/sec (p < 0.05). The area under the receiver operating characteristics curve of SWV for differentiating hemangiomas from malignant tumors was 0.86, with a sensitivity of 96.4% and a specificity of 65.8% at a cut-off value of 2.73 m/sec (p < 0.05). In the ARFI 2D images, the malignant tumors except HCCs were stiffer and more conspicuous as compared with the hemangiomas (p < 0.05).ConclusionARFI elastography with ARFI quantification and ARFI 2D imaging may be useful for differentiating hepatic hemangiomas from malignant hepatic tumors.

Acoustic radiation force impulse quantification: repeatability of measurements in selected liver segments and influence of age, body mass index and liver capsule-to-box distance

To assess the inter- and intra-observer variability of acoustic radiation force impulse (ARFI) quantification in liver segments with influence of age, body mass index (BMI) and liver capsule-to-box (CB) distance. 10 healthy volunteers were examined twice, by three experienced operators, separated by a 1-week interval. 10 readings were obtained, from segments 3, 5/6 and 7/8. Age, BMI and the CB distance were noted. The Cronbach α statistic for analysis of reliability was performed for the inter- and intra-observer studies. Multivariate linear regression models determined significance of the other parameters. 1800 velocity measurements were recorded. Mean values±standard deviation: segment 3, 1.31±0.19 m s(-1); segment 5/6, 1.12±0.22 m s(-1); segment 7/8, 1.12±0.17 m s(-1). For both the inter- and intra-observer study, the Cronbach α statistic was ≥0.7 (reliable) when taken from segments 5/6 and 7/8 but <0.7 (unreliable) for segment 3. BMI and age showed significant (p<0.0001) but contrasting correlation (segment 5/6: BMI r=0.02, age r=-0.02; segment 7/8: BMI r=-0.01, age r=0.01) with ARFI velocities when analysed for the segments deemed reliable. A weak negative correlation between ARFI velocities and liver CB distance was demonstrated for both assessed segments (segment 5/6, r=-0.08; segment 7/8, r=-0.06; p<0.001). With trained operators, ARFI is a reliable and reproducible method of liver stiffness quantification in segments 5/6 and 7/8 but acquisition of measurements from segment 3 should be avoided. Values obtained deeper to the liver capsule allow more reliable liver stiffness quantification.

Tissue elasticity estimated by acoustic radiation force impulse quantification depends on the applied transducer force: an experimental study in kidney transplant patients

Acoustic radiation force impulse (ARFI) quantification estimates tissue elasticity by measuring shear-wave velocity (SWV) and has been applied to various organs. We evaluated the impact of variations in the transducer force applied to the skin on the SWV ultrasound measurements in kidney transplant cortex and ARFI's ability to detect fibrosis in kidney transplants. SWV measurements were performed in the cortex of 31 patients with kidney allografts referred for surveillance biopsies. A mechanical device held the transducer and applied forces were equal to a compression weight of 22, 275, 490, 975, 2,040 and 2,990g. SWV group means were significantly different by repeat measures ANOVA [F(2.85,85.91) = 84.75, P < 0.0005 for 22, 275, 490, 975 and 2,040g compression weight] and also by pairwise comparisons. Biopsy specimens were sufficient for histological evaluation in 29 of 31 patients. Twelve had grade 0, 11 grade 1, five grade 2 and one grade 3 fibrosis. One-way ANOVA showed no difference in SWV performed with any of the applied transducer forces between grafts with various degrees of fibrosis. SWV measurements in kidney transplants are dependent on the applied transducer force and do not differ in grafts with different grades of fibrosis. • Acoustic radiation force impulses (ARFI) can quantify tissue elasticity during ultrasound examinations. • Elasticity estimated by ARFI in kidney transplants depends on applied transducer force. • ARFI quantification cannot detect renal allograft fibrosis. • ARFI elasticity estimates may in general vary with applied transducer force.

Evaluation of Parotid Gland Lesions with Standard Ultrasound, Color Duplex Sonography, Sonoelastography, and Acoustic Radiation Force Impulse Imaging – a Pilot Study

To evaluate the impact of standard ultrasound (US), color duplex sonography (CDS), sonoelastography (SE), and acoustic radiation force impulse (ARFI) imaging in the differentiation of parotid gland lesions. From September 2010 to February 2011, 33 parotid gland lesions of 32 patients were included in this study. Patients underwent high-resolution B-mode US (THI, 9 - 14 MHz), CDS, SE, and ARFI quantification. Then parotidectomy was performed and samples were analyzed by (immuno-) histology. Data was extracted via unpaired t-test and expressed in p-values. There were 12 Wathin's tumors (WT), 11 pleomorphic adenomas (PA), 3 other benign tumors, 3 ductal dilatations, 2 neuroendocrine carcinomas, 1 non-Hodgkin lymphoma, and 1 malignant melanoma metastasis. In B-mode US, acoustic enhancement showed statistical significance between PA and WT (p < 0.005), and CDS determined different vascularization patterns (p < 0.0005). While SE did not visualize any significant difference between PA and WT, ARFI quantification determined different mean values for both entities (p < 0.003). B-mode US, CDS, and ARFI quantification distinguish PA from WT. The predictive value of the modern techniques for the differentiation of benign and malignant parotid lesions has to be assessed in a larger series.

Assessment of renal allograft fibrosis by acoustic radiation force impulse quantification - a pilot study

Chronic allograft nephropathy characterized by interstitial fibrosis and tubular atrophy is a major cause of renal transplant failure. Acoustic radiation force impulse (ARFI) quantification is a promising noninvasive method for assessing tissue stiffness. We evaluated if the method could reveal renal transplant fibrosis. In a prospective study, 30 adult renal transplant recipients were included. ARFI quantification, given as shear wave velocity (SWV), of the renal cortex was performed by two observers. SWV was compared to grade of fibrosis (0-3) in biopsies. The median SWV was 2.8 m/s (range: 1.6-3.6), 2.6 m/s (range: 1.8-3.5) and 2.5 m/s (range: 1.6-3) for grade 0 (n = 12), 1 (n = 10) and grades 2/3 (n = 8) fibrosis respectively. SWV did not differ significantly in transplants without and with fibrosis (grade 0 vs. grade 1, P = 0.53 and grade 0 vs. grades 2/3, P = 0.11). The mean intraobserver coefficient of variation was 22% for observer 1 and 24% for observer 2. Interobserver agreement, expressed as intraclass correlation coefficient was 0.31 (95% CI: -0.03 to 0.60). This study does not support the use of ARFI quantification to assess low-grade fibrosis in renal transplants. ARFI quantification in its present stage of development has also high intra- and interobserver variation in renal transplants.

Measurement of Liver Elasticity with Acoustic Radiation Force Impulse (ARFI) Technology: An Alternative Noninvasive Method for Staging Liver Fibrosis in Viral Hepatitis

The acoustic radiation force impulse (ARFI) technology is a novel ultrasound method that provides information about the local elasticity of tissue in real-time. ARFI is integrated in a conventional ultrasound system. The aim of this exploratory study was to evaluate this new technique in the assessment of liver fibrosis in a cohort with chronic viral hepatitis B and C and to ascertain the most reliable hepatic segment for measurements. 57 patients (27 female, 30 male, mean age 54 years) with chronic viral hepatitis B and C underwent ARFI imaging and consecutively liver biopsy. The results were compared to the histological fibrosis degree (F), which served as the reference. 20 healthy volunteers received ARFI quantification of different segments of the liver. The best ARFI assessments with the lowest rate of invalid measurements were carried out by an intercostal approach to segment VII/VIII of the liver. The ARFI velocities of the healthy group had a mean of 1.09 m/s (range 0.79 - 1.32 m/s), the means of the patient group ranged from 0.83 to 4.19 m/s. ARFI quantification correlated significantly with the histological fibrosis stage (p < 0.001). The area under the receiver operating characteristic (ROC) curves for the accuracy of ARFI imaging was 85 %, 92 % and 87 % for the diagnosis of moderate fibrosis (>or= F2), severe fibrosis (>or= F3) and cirrhosis ( = F 4), respectively. This study underscores the usefulness of ARFI as a quick method for assessing liver fibrosis or cirrhosis in patients with HBV or HCV. ARFI measurements of the liver should be performed via an intercostal access. Increasing ARFI velocities correlate with higher degree of hepatic fibrosis.

Evaluation of Acoustic Radiation Force Impulse (ARFI) imaging and contrast-enhanced ultrasound in renal tumors of unknown etiology in comparison to histological findings

It was the aim of our study to combine the findings of contrast-enhanced ultrasound and ARFI-imaging in the evaluation of renal masses in comparison to the histological findings. Fifteen patients with unclear kidney lesions were analyzed. We used a high-end ultrasound machine (Siemens ACUSON S2000, Siemens Healthcare, Erlangen, Germany) with a multifrequency curved array 4 MHz or linear 9 MHz transducer. Contrast-enhanced ultrasound (bolus injection 1.6-2.4 ml SonoVue was carried out. We obtained fifteen ARFI measurements from each patient with at least five values for quantification. The ARFI-ROI (region of interest) was placed in the ventral margin of the kidney tumor and the whole ROI was covered by the tumor. The "reference-ROI" was placed in the ventral kidney parenchyma of the patient at a distance of at least two centimeters from the tumor. All renal tumors were surgically resected. In cases of complex renal cysts or anatomic variations mimicking renal tumors ("pseudo-tumors"), constant results of ultrasound examinations and additional MRI or multiphase CT over 6 months were required. Fifteen patients were included in the study and were examined using the diagnostic ultrasound tools of our study The kidney tumors of our patients had diameters ranging from 1.5 to 8 cm and were located at depths ranging from 2 to 5.5 cm. ARFI imaging was also performed in all patients. A field up to a depth of 10 cm could be visualized for diagnostic use. Performing ARFI quantification using Siemens Virtual Touch Tissue Quantification we obtained minimum and maximum tissue shear velocities ranging from 1.6 to 3.42 m/s. The reference tissue ROIs showed values from 1.31 to 4.4 m/s. 12 cases were accepted for surgical resection. The visualization of lesions with Virtual Touch Tissue Imaging confirmed the measurements of ARFI quantification and were able to depict the different areas of stiffness in the kidney tissue. No infiltration of kidney veins or vena cava was detected by contrast-enhanced ultrasound. Of the 12 cases two "complicated" renal cysts were examined, and both showed Bosniak-III findings. ARFI imaging improves visualization of unclear renal masses in comparison to fundamental B-scan and adds new information about the tissue stiffness in a less time-consuming and more reproducible way. CEUS with SonoVue allows an early evaluation of renal masses or complex cysts.