Agarose as a Tissue Mimic for the Porcine Heart, Kidney, and Liver: Measurements and a Springpot Model.

Agarose gels are often used as a tissue mimic. The goal of this work was to determine the appropriate agarose concentrations that result in mechanical properties that match three different porcine organs. Strain tests were carried out with an amplitude varying from 0.01% to 10% at a frequency of 1 Hz on a range of agarose concentrations and porcine organs. Frequency sweep tests were performed from 0.1 Hz to a maximum of 9.5 Hz at a shear strain amplitude of 0.1% for agarose and porcine organs. In agarose samples, the effect of pre-compression of the samples up to 10% axial strain was considered during frequency sweep tests. The experimental measurements from agarose samples were fit to a fractional order viscoelastic (springpot) model. The model was then used to predict stress relaxation in response to a step strain of 0.1%. The prediction was compared to experimental relaxation data, and the results agreed within 12%. The agarose concentrations (by mass) that gave the best fit were 0.25% for the liver, 0.3% for the kidney, and 0.4% for the heart. At a frequency of 0.1 Hz and a shear strain of 0.1%, the agarose concentrations that best matched the shear storage modulus of the porcine organs were 0.4% agarose for the heart, 0.3% agarose for the kidney, and 0.25% agarose for the liver.

Compound Acoustic Radiation Force Impulse Imaging of Bovine Eye by Using Phase-Inverted Ultrasound Transducer.

In general, it is difficult to visualize internal ocular structure and detect a lesion such as a cataract or glaucoma using the current ultrasound brightness-mode (B-mode) imaging. This is because the internal structure of the eye is rich in moisture, resulting in a lack of contrast between tissues in the B-mode image, and the penetration depth is low due to the attenuation of the ultrasound wave. In this study, the entire internal ocular structure of a bovine eye was visualized in an ex vivo environment using the compound acoustic radiation force impulse (CARFI) imaging scheme based on the phase-inverted ultrasound transducer (PIUT). In the proposed method, the aperture of the PIUT is divided into four sections, and the PIUT is driven by the out-of-phase input signal capable of generating split-focusing at the same time. Subsequently, the compound imaging technique was employed to increase signal-to-noise ratio (SNR) and to reduce displacement error. The experimental results demonstrated that the proposed technique could provide an acoustic radiation force impulse (ARFI) image of the bovine eye with a broader depth-of-field (DOF) and about 80% increased SNR compared to the conventional ARFI image obtained using the in-phase input signal. Therefore, the proposed technique can be one of the useful techniques capable of providing the image of the entire ocular structure to diagnose various eye diseases.

Shear wave elastography of tibial nerve in patients with diabetic peripheral neuropathy-A cross-sectional study.

OBJECTIVE: To explore the role of shear wave elastography of the tibial nerve as a potential ultrasonographic method for the diagnosis of tibial neuropathy in patients with type 2 diabetes. MATERIALS AND METHODS: This cross-sectional study included 50 subjects each in case (patients with diabetic tibial neuropathy diagnosed on the basis of clinical features and nerve conduction study) and control groups (non-diabetic non-neuropathic healthy volunteers). The exclusion criteria included the presence of type 1 diabetes, a known history of neuropathy from other causes except for type 2 diabetes, or a history of leg or ankle fracture. Cross-sectional area and shear wave velocity values of the tibial nerve were measured in both groups. Demographic details and body mass index were obtained in both groups and additionally, the duration of type 2 diabetes and HbA1c values in the case group were also noted. Wilcoxon Mann-Whitney U test was used to compare these variables in study groups. ROC curve analysis provided additional findings. RESULTS: Tibial nerve stiffness was significantly higher in the case group (p-value < 0.001). The study groups did not significantly differ in the Cross-sectional area of the tibial nerve (p-value 0.57). The case group exhibited a higher frequency of loss of the fascicular pattern of the tibial nerve (40% vs 18%, p-value 0.027). Duration of diabetes mellitus and HbA1c values did not significantly affect Shear wave velocity values in the case group. At the cut-off value of Shear wave velocity of 3.13 m/s, sensitivity and specificity to diagnose diabetic peripheral neuropathy were 94% and 88% respectively. CONCLUSION: Increased nerve stiffness is seen in patients with diabetic peripheral neuropathy. Shear wave elastography might prove as a novel noninvasive technology for screening/early diagnosis of diabetic peripheral neuropathy.

Prediction of acute rejection in renal allografts using shear-wave dispersion slope.

OBJECTIVES: To evaluate the role of shear-wave dispersion slope for predicting renal allograft dysfunction. METHODS: We retrospectively reviewed 128 kidney transplant recipients (median age, 55 years [interquartile range, 43-62 years]; male, 68) who underwent biopsy for allograft evaluation from November 2022 to February 2023. Cortex and renal sinus fat stiffness and shear-wave dispersion slope were obtained at shear-wave elastography (SWE). Cortex-to-sinus stiffness ratio (SR) and dispersion slope ratio (DSR)-related clinical and pathologic factors were evaluated using multivariable linear regression analysis. We conducted univariate and multivariate analyses for multiparametric ultrasound (US) parameters for identifying acute rejection and calculated the area under the receiver operating curve (AUC) values. RESULTS: Of 128 patients, 31 (24.2%) demonstrated acute rejection. The SR value did not differ between patient groups (1.21 vs. 1.20, p = 0.47). Patients with acute rejection demonstrated a higher DSR than those without rejection (1.4 vs. 1.21, p < 0.01). Interstitial fibrosis and tubular atrophy grade (IFTA; coefficient, 0.11/grade; p = 0.04) and renal transplant and biopsy interval (coefficient, 0.00007/day; p = 0.03) were SR determinant factors, whereas only IFTA grade (coefficient, 0.10/grade; p = 0.01) for DSR. Multivariate analysis revealed mean resistive index (odds ratio [OR] 1.08, 95% confidence interval [CI] 1.02-1.14, p = 0.01) and DSR value (OR 16.0, 95% CI 3.0-85.8, p = 0.001) as independent factors for predicting acute rejection. An AUC of 0.74 for detecting acute rejection was achieved by combining the resistive index and DSR value. CONCLUSION: Shear-wave dispersion slope obtained at SWE may help identify renal allograft dysfunction. CLINICAL RELEVANCE STATEMENT: Acute rejection in renal allografts is a major cause of allograft failure, but noninvasive diagnosis is a challenge. Shear-wave dispersion slope can identify acute rejection non-invasively. KEY POINTS: • The interstitial fibrosis and tubular atrophy grade was a determinant factor for stiffness ratio and shear-wave dispersion slope ratio between cortex and renal sinus fat. • Shear-wave dispersion slope ratio between cortex and renal sinus fat could identify acute rejection in renal allografts. • A shear-wave dispersion slope has a potential to reduce unnecessary renal biopsy for evaluating renal allografts.

Predictive value of acoustic radiation force impulse imaging in breast cancer after neoadjuvant chemotherapy.

To investigate the predictive value of acoustic radiation force impulse imaging for neoadjuvant chemotherapy in breast cancer. Seventy-eight breast cancer patients treated in our hospital from March 2019 to March 2022 were recruited. They received neoadjuvant chemotherapy and were examined by conventional ultrasound and acoustic radiation force impulse imaging before chemotherapy and after two cycles of chemotherapy. The lesion diameter, intralesional blood flow pulsatility index (PI), resistance index (RI), shear wave velocity (SWV), and change rate (Δlesion diameter, ΔPI, ΔRI, ΔSWV) were compared between the two groups before and after chemotherapy. The receiver operating characteristic curve was drawn to evaluate the predictive power of related parameters on the efficacy of neoadjuvant chemotherapy in breast cancer. After two cycles of neoadjuvant chemotherapy, according to the Miller-Payne grading, 57 cases (73.08%) with significant neoadjuvant chemotherapy response were classified as the response group, and 21 cases (26.92%) with non-significant response were classified as the non-response group. Before and after chemotherapy, the difference in lesion diameter, PI, RI, SWV, and change rate (Δlesion diameter, ΔPI, ΔRI, and ΔSWV) was statistically significant between the two groups (P < 0.05). The area under the curve of ΔSWV in predicting the efficacy of neoadjuvant chemotherapy 0.876 (95%CI 0.781 ~ 0.939) was significantly higher than that of Δlesion diameter 0.652 (95%CI 0.535 ~ 0.756), that of ΔPI 0.712 (95%CI 0.599 ~ 0.809), and that of ΔRI 0.678 (95%CI 0.563 ~ 0.780) (P < 0.05). The change rate of tissue stiffness has a relatively high predictive value for the effect of neoadjuvant chemotherapy in breast cancer.

Magnetic Resonance Acoustic Radiation Force Imaging (MR-ARFI) for the monitoring of High Intensity Focused Ultrasound (HIFU) ablation in anisotropic tissue.

OBJECTIVE: We introduce a non-invasive MR-Acoustic Radiation Force Imaging (ARFI)-based elastography method that provides both the local shear modulus and temperature maps for the monitoring of High Intensity Focused Ultrasound (HIFU) therapy. MATERIALS AND METHODS: To take tissue anisotropy into account, the local shear modulus µ is determined in selected radial directions around the focal spot by fitting the phase profiles to a linear viscoelastic model, including tissue-specific mechanical relaxation time τ. MR-ARFI was evaluated on a calibrated phantom, then applied to the monitoring of HIFU in a gel phantom, ex vivo and in vivo porcine muscle tissue, in parallel with MR-thermometry. RESULTS: As expected, the shear modulus polar maps reflected the isotropy of phantoms and the anisotropy of muscle. In the HIFU monitoring experiments, both the shear modulus polar map and the thermometry map were updated with every pair of MR-ARFI phase images acquired with opposite MR-ARFI-encoding. The shear modulus was found to decrease (phantom and ex vivo) or increase (in vivo) during heating, before remaining steady during the cooling phase. The mechanical relaxation time, estimated pre- and post-HIFU, was found to vary in muscle tissue. DISCUSSION: MR-ARFI allowed for monitoring of viscoelasticity changes around the HIFU focal spot even in anisotropic muscle tissue.

Fontan Hepatopathy-Managing Unknowns.

BACKGROUND AND AIMS: How to best monitor Fontan-associated liver disease (FALD) remains unclear. We describe results from a prospective liver care pathway in adults (n=84) with a Fontan circulation. METHODS: Routine assessment of the liver, by acoustic radiation force frequency and ultrasound was undertaken. Results, including liver biochemistry, systemic ventricular function (echocardiography), functional class, medication use and clinical endpoints (varices, hepatocellular carcinoma, heart transplantation and death) were collated. RESULTS: Most individuals returned a cirrhotic range acoustic radiation force impulse imaging (ARFI) result. ARFI values were greater in the proportion of individuals with hepatic nodularity (p=0.024). Univariate analysis demonstrated moderate correlation with platelet number (Spearmans rho= -0.376, p=0.049). Patients with clinical endpoints had lower platelets (p=0.012) but only a trend to hepatic nodularity (p=0.057). Clinical endpoints were more common in those with ventricular dysfunction (p=0.011). Multivariate analysis revealed that age at Fontan and being on angiotensin converting enzyme inhibitors (ACEI) predicted ARFI score (ß=0.06 [95% CI 0.01-0.09], p=0.007 and ß=0.53 [95% CI 0.17-0.89], p=0.005, respectively). However, these associations were not significant once adjusted for Fontan type, age at ARFI, systemic ventricle morphology, ventricle function, or Model for End-stage Liver Disease (MELD-XI) excluding international normalised ratio (INR) (p>0.05 for all). CONCLUSIONS: Ideal FALD monitoring remains unclear. ARFI has utility as a binary non-invasive indicator of cirrhosis, highlighting individuals who may need more frequent ongoing monitoring for hepatocellular carcinoma. However, no definite advantage to serial ARFI, once cirrhotic range ARFI results are present, has been identified.

Utilizing shear wave elastography for the evaluation of optical nerve involvement in Behçet's disease.

In this study, we investigated the elasticity of the optic nerve using shear wave elastography (SWE) in patients with Behçet's Disease (BD) and compare findings with a healthy control group. Optic nerve measurements of 40 eyes in the BD group and 38 eyes in the control group were performed by SWE (SWE-right and SWE-left). The mean age of the individuals in the BD group was higher than controls (p = 0.022). The SWE measurement results in the right eye were significantly higher in the BD group (p = 0.005), while SWE-left values were similar in the two groups (p = 0.206). There was a moderate positive correlation between age and SWE-right (r = 0.347, p = 0.031), there was no correlation between SWE-left and age (p = 0.756). It was found that SWE-right had significant value in distinguishing between BD and healthy controls (sensitivity: 75%, specificity: 78.9%; p = 0.005); whereas, SWE-left did not (p = 0.206). In the multiple logistic regression analysis, after adjusting for age and sex, the performance of SWE-right to distinguish BD patients from controls was found to remain significant (OR: 15.045, 95% CI: 2.33-97.120, p = 0.004). Due to the fact that only SWE-right values appear to have significant discriminatory performance for BD, it is feasible to suggest that the frequency and severity of BD involvement are associated with SWE-related changes in the optic nerve. This finding indicates the need for more comprehensive studies evaluating optic nerve SWE values in this context.

Evaluation of Acoustic Radiation Force Impulse Imaging in Differentiating Benign and Malignant Cervical Lymphadenopathy.

Background: The aim of this study was to assess the diagnostic role of acoustic radiation force impulse imaging (ARFI) in differentiating benign and malignant cervical nodes. Methods: This was a diagnostic accuracy cross-sectional study. All patients who underwent ultrasound-guided fine-needle aspiration cytology (FNAC) of cervical nodes were included. Patients without FNAC/biopsy and patients in whom cervical nodes were cystic or completely necrotic were excluded. FNAC was used as reference investigation to predict the diagnostic accuracy. In all cases, FNAC was carried out after the B-mode, color Doppler and the ARFI imaging. In patients with multiple cervical lymph nodes, the most suspicious node based on grayscale findings was chosen for ARFI. ARFI included Virtual Touch imaging (VTI), area ratio (AR), and shear wave velocity (SWV) for each node, and the results were compared with FNAC/biopsy. Results: The final analysis included 166 patients. Dark VTI elastograms had sensitivity and specificity of 86.2% and 72.1%, respectively, in identifying malignant nodes. Sensitivity and specificity of AR were 71.3% and 82.3%, respectively, for a cutoff of 1.155. Median SWV of benign and malignant nodes was 1.9 [95% confidence interval (CI), 1.56-2.55] m/s and 6.7 (95% CI, 2.87-9.10) m/s, respectively. SWV >2.68 m/s helped in identifying malignant nodes with 81% specificity, 81.6% sensitivity, and 81.3% accuracy. ARFI was found to be inaccurate in tuberculous and lymphomatous nodes. Conclusion: Malignant nodes had significantly darker elastograms, higher AR and SWV compared to benign nodes, and SWV was the most accurate parameter. ARFI accurately identifies malignant nodes, hence could potentially avoid unwarranted biopsy.

Evaluation of change in tumor stiffness measured by acoustic radiation force impulse imaging for early prediction of response to neoadjuvant chemotherapy in breast cancer.

OBJECTIVES: In this study, the role of change in tumor stiffness between pre- and post-two cycles of neoadjuvant chemotherapy (NACT) measured by Acoustic Radiation Force Impulse (ARFI) imaging for predicting the response to NACT in breast cancer was analyzed. METHODS: Fifty-two adult women with biopsy-proven locally advanced breast cancer and early-stage breast cancer who received NACT followed by either modified radical mastectomy or breast conservation surgery were included in the study. Tumor stiffness represented by shear wave velocity (SWV) in meter per second by ARFI imaging was measured before and after two cycles of NACT. Participants were categorized into responders and nonresponders based on pathological response assessment from the postoperative specimen. The association of change in tumor stiffness between pre- and post-two cycles of NACT with final pathological response status was assessed. RESULTS: The mean change in SWV before and after completion of two cycles of NACT was 0.42 ± 0.16 and 0.17 ± 0.11 m/s in responders and nonresponders, respectively, and this difference was proven to be statistically significant (p < 0.001) suggesting that tumors that exhibit a larger reduction in tumor stiffness, respond better. An SWV reduction cut-off of 0.295 m/s between baseline and post-two cycles of NACT was also arrived at, which can discriminate between responders and nonresponders with a sensitivity and specificity of 88% and 83%, respectively. CONCLUSION: Difference in tumor stiffness measured by ARFI imaging before and after two cycles of chemotherapy can be used as a reliable early predictor of response to chemotherapy in breast cancer.

Diagnostic value of shear wave velocity in polycystic ovarian syndrome.

Aim: In polycystic ovarian syndrome, the ovaries become stiffer due to chronic anovulation. We aimed to compare tissue elasticity in terms of shear wave velocities measured using acoustic radiation force impulse imaging technique between the ovaries of polycystic ovarian syndrome women and non-polycystic ovarian syndrome women. Material and methods: The study was designed as a retrospective data analysis of women who underwent transvaginal ultrasound and acoustic radiation force impulse imaging in a university hospital between July 2014 and March 2015, for various reasons. There were 32 polycystic ovarian syndrome patients and 32 patients without a diagnosis of polycystic ovarian syndrome. Age, body mass index, fasting glucose levels, cycle day 3 follicle stimulating hormone, luteinizing hormone, thyroid stimulating hormone, prolactin, antimullerian hormone levels, and menstrual patterns with clinical hyperandrogenism were evaluated. On the menstrual cycle days 2-4, by performing a transvaginal ultrasound scan, the ovarian volumes and antral follicle counts in both ovaries were recorded for each woman. The ultrasound system was converted into the elastography mode, and acoustic radiation force impulse imaging was performed. Shear wave velocity (m/sec) was measured at least 5 times for each ovary, and the mean value was calculated for each polycystic ovarian syndrome and non-polycystic ovarian syndrome woman. Results: Age, body mass index, fasting glucose levels, cycle day 3 follicle stimulating hormone, luteinizing hormone, thyroid stimulating hormone, and prolactin levels were similar between the groups (p >0,05). Antimullerian hormone levels, antral follicle counts, and mean ovarian volumes were statistically different between the groups (p <0,05). Mean shear wave velocity values for both ovaries were 2.12 ± 0.82 (0.78-4.9) m/sec in the polycystic ovarian syndrome group, and 1.18 ± 0.41 (0.77-2.0) m/sec in the non-polycystic ovarian syndrome group, which was statistically significantly different (p = 0.016). Conclusion: In our study, we found significantly higher shear wave velocity levels in polycystic ovarian syndrome women than non-polycystic ovarian syndrome women, which indicates an impact of the condition on shear wave velocity. The increased acoustic frequencies cause a decreased response in time to transition, and motion becomes out of phase; in other words, scattered waves are faster in stiffer ovaries. Our results are thus compatible with the pathophysiology of the disease. Shear wave velocity is a beneficial tool for evaluating ovarian elasticity in polycystic ovarian syndrome patients in whom the levels are found to be significantly higher than non-polycystic ovarian syndrome women. In light of these findings, shear wave velocity is expected to be slower than polycystic ovarian syndrome levels in ovulatory women.

A nomogram for predicting the risk of neck node metastasis in oral cavity carcinoma using acoustic radiation force impulse imaging (ARFI).

BACKGROUND: The study was conducted to assess the accuracy power of Acoustic radiation force impulse imaging (ARFI) and generate a nomogram using ultrasound and ARFI to predict malignant cervical lymph nodes in head and neck squamous cell carcinoma. MATERIAL AND METHODS: 374 cervical lymph nodes from 67 patients were evaluated. The B-mode ultrasonography and the elastography findings were compared with the final histopathological diagnosis. Radiological variables were used to construct nomogram and clinical utility of the nomogram was cross-validated. RESULTS: In univariate analysis, status of the hilum, Long Axis Diameter, Short axis diameter, colour virtual touch imaging grade (VTI) and shear wave velocity were significant in predicting metastasis in the cervical lymph nodes. In multivariable analysis, it was found that predominance of red over yellow area on colour VTI was significantly associated with lymph node metastasis. A multiple logistic regression performed to ascertain the effects of on the likelihood that patients had lymph node metastasis on histopathology was statistically significant, χ2(10) = 44.96, p < 0.001. The model was able to correctly classify 93.28% of cases and the concordance index (c-index) was estimated to be 0.8773. A nomogram was thus established to predict metastasis in cervical lymph nodes. CONCLUSIONS: ARFI increases the diagnostic accuracy of conventional USG in predicting metastatic lymph nodes in HNSCC. Adding the constructed nomogram to the conventional diagnostic pathway can provide an alternative option to frozen section and FNAC.

Prostate Cancer Detection Using 3-D Shear Wave Elasticity Imaging.

Transrectal ultrasound (TRUS) B-mode imaging provides insufficient sensitivity and specificity for prostate cancer (PCa) targeting when used for biopsy guidance. Shear wave elasticity imaging (SWEI) is an elasticity imaging technique that has been commercially implemented and is sensitive and specific for PCa. We have developed a SWEI system capable of 3-D data acquisition using a dense acoustic radiation force (ARF) push approach that leads to enhanced shear wave signal-to-noise ratio compared with that of the commercially available SWEI systems and facilitates screening of the entire gland before biopsy. Additionally, we imaged and assessed 36 patients undergoing radical prostatectomy using 3-D SWEI and determined a shear wave speed threshold separating PCa from healthy prostate tissue with sensitivities and specificities akin to those for multiparametric magnetic resonance imaging fusion biopsy. The approach measured the mean shear wave speed in each prostate region to be 4.8 m/s (Young's modulus E = 69.1 kPa) in the peripheral zone, 5.3 m/s (E = 84.3 kPa) in the central gland and 6.0 m/s (E = 108.0 kPa) for PCa with statistically significant (p < 0.0001) differences among all regions. Three-dimensional SWEI receiver operating characteristic analyses identified a threshold of 5.6 m/s (E = 94.1 kPa) to separate PCa from healthy tissue with a sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and area under the curve (AUC) of 81%, 82%, 69%, 89% and 0.84, respectively. Additionally, a shear wave speed ratio was assessed to normalize for tissue compression and patient variability, which yielded a threshold of 1.11 to separate PCa from healthy prostate tissue and was accompanied by a substantial increase in specificity, PPV and AUC, where the sensitivity, specificity, PPV, NPV and AUC were 75%, 90%, 79%, 88% and 0.90, respectively. This work illustrates the feasibility of using 3-D SWEI data to detect and localize PCa and demonstrates the benefits of normalizing for applied compression during data acquisition for use in biopsy targeting studies.

Quantitative Evaluation of Neonatal Brain Elasticity Using Shear Wave Elastography.

OBJECTIVES: To demonstrate the feasibility of 2-dimensional brain ultrasound shear wave elastography (SWE) and to define the average elasticity values of the gray and white matter in term neonates. METHODS: This work was a prospective observational single-center study including 55 healthy term neonates consecutively recruited in the maternity ward between the second and third postnatal days. All were successfully evaluated with a cerebral SWE examination performed with a multifrequency 4-9-MHz transducer. Bilateral sagittal planes of the thalamus and corona radiata were used to measure stiffness using a quantitative SWE method. Several elastograms with 5 to 15 nonoverlapping areas were obtained from the 2 different anatomic locations. The 5 most central measurements were averaged as representative values. RESULTS: The 55 neonates ranged from 37 to 40 weeks' gestation. The estimated mean velocity values of the thalamus (1.17 m/s; 95% confidence interval, 1.13, 1.22 m/s) and corona radiata (1.60 m/s; 95% confidence interval, 1.57, 1.64 m/s) were statistically different (P < .001). There was no significant influence of laterality, gestational age, cephalic perimeter, sex, length, or type of delivery on the stiffness measurements. CONCLUSIONS: Brain ultrasound SWE is feasible and allows measurements of neonatal brain elasticity. The elasticity of the thalamus and corona radiata at the frontal white matter in healthy term neonates is different. The knowledge of normal SWE ranges in term neonates allows comparative studies under pathologic conditions.

The non-invasive assessment of hepatic fibrosis.

Hepatic disease accounts for approximately 2 million deaths/year worldwide. Liver fibrosis, as the last stage of numerous chronic liver diseases, is one of the most relevant prognostic factors. The liver biopsy with the histopathological examination is considered to be the "gold standard" for the identification and staging of the hepatic fibrosis. However, liver biopsy is known as an invasive investigation that has multiple limitations. Research studies conducted in the last few years focused on identifying non-invasive type methods for the evaluation of hepatic fibrosis; usually, there are 2 categories of such investigations: serologic tests and imaging techniques. This narrative review presents the non-invasive investigation methods used in the liver fibrosis evaluation. New molecular perspectives on fibrogenesis and fibrosis regression, as well as the appearance of therapeutic antifibrotic agents, justify the necessity of non-invasive tools to detect and grade liver fibrosis.

Clinical Utility of Qualitative Elastography Using Acoustic Radiation Force Impulse for Differentiating Benign from Malignant Salivary Gland Tumors.

The goal of the work described here was to evaluate the utility of acoustic radiation force impulse (ARFI) imaging, a novel elastography technique, for differentiating benign from malignant salivary gland tumors. With the use of conventional strain elastography (SE) and ARFI imaging with a four-pattern scoring system, 185 tumors were examined (163 benign/22 malignant). When a score of ≥3 was used to define malignancy, the sensitivity, specificity and accuracy were higher for ARFI imaging (77.3%, 63.8% and 65.4%, respectively) than for conventional SE (54.5%, 56.4% and 56.2%, respectively). ARFI imaging findings revealed that most (92%) Warthin tumors, but only 24% of pleomorphic adenomas, were benign (score: 1 or 2). Attenuation of acoustic push pulses made it difficult to determine the stiffness of malignant tumors in the deep parotid lobes. Thus, ARFI imaging is a useful tool for screening Warthin tumors and exhibits high sensitivity for malignant tumors of salivary glands, other than deep parotid lobe tumors.

Spleen stiffness measurement by shear wave elastography using acoustic radiation force impulse in predicting the etiology of splenomegaly.

PURPOSE: To measure spleen stiffness by shear wave elastography (SWE) using acoustic radiation force impulse (ARFI) in patients with splenomegaly and to evaluate utility of elastography technique in identifying etiology of splenomegaly. METHODS: Sixty-one treatment-naïve patients with splenomegaly were enrolled. The control group consisted of 20 healthy subjects without history of any disease including diabetes and hypertension, alcohol consumption, or biochemical or ultrasonographic findings indicating hepatic and renal diseases. B-mode ultrasonography and elastographic examinations were performed by a radiologist blinded to the participants. Spleen stiffness was measured by SWE using ARFI. Shear wave velocity (SWV) values were given in m/s. RESULTS: Splenomegaly patients were assigned into three groups according to their etiologies as hepatoportal (n = 21), myeloproliferative (n = 23), and infectious (n = 17). Splenomegaly groups and control group were comparable regarding age and sex. Spleen size was higher in the splenomegaly groups than in the controls. Median SWV was significantly higher in the hepatoportal (3.85 m/s) and myeloproliferative (3.42 m/s) groups than in the infectious (2.66 m/s) and control (2.22 m/s) groups. The correlation between SWV and spleen size was not significant in any of the groups. The cut-off value was 3.42 (sensitivity 80.9%, specificity 56.5%) in distinguishing hepatoportal from myeloproliferative etiology; 3.02 (sensitivity 100%, specificity 100%) in distinguishing hepatoportal from infectious etiology; and 2.84 (sensitivity 91.3%, specificity 88.2%) in distinguishing myeloproliferative from infectious etiology. CONCLUSION: Spleen stiffness measured by elastographic techniques in splenomegaly patients was higher than that in healthy subjects. SWV appeared to be beneficial in predicting the etiology of splenomegaly.

Utility of Ultrasound Elastography to Differentiate Benign from Malignant Cervical Lymph Nodes.

BACKGROUND: The purpose of this study was to evaluate the usefulness of strain elastography and acoustic radiation force impulse (ARFI) imaging in the differentiation of benign and malignant cervical lymph nodes (LNs). MATERIALS AND METHODS: In this prospective study, 50 enlarged cervical LNs (33 benign and 17 malignant) were examined by B-mode ultrasound (US), color Doppler, and strain elastography. Elastographic patterns (1-5) were categorized based on distribution of hard area within LN. The shear wave velocity (SWV) of LNs was evaluated by ARFI imaging. Diagnostic performance of sonoelastographic parameters was compared taking histopathology of LN as a reference standard. Optimal cutoff value of the mean SWV values for predicting malignancy was determined using receiver operating characteristic curve analysis. RESULTS: Among US parameters, borders of LN had the highest diagnostic accuracy (80%), while echogenicity had the least (48%). Majority of benign LNs (n = 31) had elastography patterns 1 and 2, while majority of malignant LNs (n = 16) had patterns 3-5 (P = 0.000). The sensitivity, specificity, and accuracy of elastography were 94.1%, 93.9%, and 94%, respectively. The mean SWV of benign LNs (1.670 ± 0.367 m/s) differed significantly from malignant LNs (2.965 ± 0.826 m/s; P = 0.000). A cutoff value of 2.05 m/s predicted malignancy with 88.2% sensitivity and 84.8% specificity and gave an area under the curve of 0.949 (95% confidence interval: 0.70-1.20). CONCLUSION: Elastography has high diagnostic accuracy in differentiating benign and malignant cervical LNs and can be potentially useful in selecting the LN with high probability of malignancy, on which fine-needle aspiration cytology/biopsy can be performed.

Multiparametric Ultrasound for Targeting Prostate Cancer: Combining ARFI, SWEI, QUS and B-Mode.

Diagnosing prostate cancer through standard transrectal ultrasound (TRUS)-guided biopsy is challenging because of the sensitivity and specificity limitations of B-mode imaging. We used a linear support vector machine (SVM) to combine standard TRUS imaging data with acoustic radiation force impulse (ARFI) imaging data, shear wave elasticity imaging (SWEI) data and quantitative ultrasound (QUS) midband fit data to enhance lesion contrast into a synthesized multiparametric ultrasound volume. This SVM was trained and validated using a subset of 20 patients and tested on a second subset of 10 patients. Multiparametric US led to a statistically significant improvements in contrast, contrast-to-noise ratio (CNR) and generalized CNR (gCNR) when compared with standard TRUS B-mode and SWEI; in contrast and CNR when compared with MF; and in CNR when compared with ARFI. ARFI, MF and SWEI also outperformed TRUS B-mode in contrast, with MF outperforming B-mode in CNR and gCNR as well. ARFI, although only yielding statistically significant differences in contrast compared with TRUS B-mode, captured critical qualitative features for lesion identification. Multiparametric US enhanced lesion visibility metrics and is a promising technique for targeted TRUS-guided prostate biopsy in the future.

Value of conventional ultrasound, ultrasound elasticity imaging, and acoustic radiation force impulse elastography for prediction of malignancy in breast lesions.

OBJECTIVE: To evaluate the efficacies of conventional ultrasound (US), US elasticity imaging (EI), and acoustic radiation force impulse (ARFI) elastography in breast malignancy diagnosis. METHODS: We included 315 women (mean age, 44 years; range, 18-81 years) with 336 pathologically proven breast lesions in this retrospective study. All lesions underwent conventional US, EI, and ARFI (including virtual touch tissue imaging [VTI], virtual touch tissue quantification [VTQ], and virtual touch tissue imaging and quantification [VTIQ]) elastography. Multivariate logistic regression analysis was performed to assess 12 independent variables for malignancy prediction. Diagnostic performance was evaluated with receiver operating characteristic (ROC) curve analysis. RESULTS: Irregular lesion shape was the strongest independent predictor for breast malignancy, followed by poorly defined margins, taller than wide dimensions, posterior echo attention, VTIQ, and VTI boundaries (P < 0.05). Area under the ROC curve (AUC) for VTIQ was higher than other significant independent variables. With the best cut-off value of 3.74 m/s, the AUC, sensitivity, and specificity were 0.93 (95% CI: 0.90, 0.96), 90.1%, and 91.1%, respectively. CONCLUSIONS: ARFI elastography is a promising method in breast malignancy prediction, with good diagnostic performance. For patients requiring surgery, the combination of various methods can provide better diagnostic results and may help to reduce unnecessary biopsy or surgery.