Prostate cancer: three-dimensional sonoelastography for in vitro detection

Free-hand ultrasound strain elastography in evaluation of soft tissue tumors

OBJECTIVE

The purpose of this study is to evaluate elastography in a wide spectrum of soft tissue superficial lesions by correlating the elastographic characteristics of these lesions with the elastographic score (ES) system established by Asteria.

METHODS

Forty patients with different superficial lesions of the soft tissues were studied, including lipomas, schwannomas, neuromas, epidermal inclusion cysts, "in transit" melanoma metastasis, arterio-venous malformation, and giant-cell tumor. An ultrasound examination was performed combined with color-Doppler and elastographic module. The B-mode criteria were echogenicity, margins, and structural homogeneity of the lesion. The color-Doppler criterion was irregular and mainly intra-nodular vascularization. ES 1-4 was attributed, in relation with the increasing tissue stiffness, according to the classification of Asteria adapted for soft tissues. Subsequently, we added to each single B-mode and color-Doppler criterion the ES 3 and 4, thus crossing two parameters of malignancy. All the presumptive diagnoses formulated were confirmed with the clinical data or with the histopathological result.

RESULTS

The hypoechoic appearance had the best diagnostic performance. Sensitivity was 87%, specificity 71%, positive predictive value (PPV) 80%, negative predictive value (NPV) 80%, and diagnostic accuracy 80%. There was a good correlation with the clinical and biopsy data, the irregularity of margins the worst performance, the inhomogeneity an intermediate. Color-Doppler had sensitivity 74%, specificity 82%, PPV 85%, NPV 70% and diagnostic accuracy 77.5%. Elastography had sensitivity 87%, specificity 94%, PPV 95%, NPV 84%, and diagnostic accuracy 90%. The combination hypoechoic appearance + ES3/ES4 showed sensitivity 83%, specificity 100%, PPV 100%, NPV 81%,and diagnostic accuracy of 90%. The combination of irregularity of margins + ES3/ES4 showed sensitivity 43%, specificity 100%, PPV 100%, NPV 59%, and diagnostic accuracy of 67.5%. The combination of inhomogeneity of the lesion + ES3/ES4 showed sensitivity 65%, specificity 94%, PPV 94%, NPV 68%, and diagnostic accuracy of 78%. The combination of the color-Doppler with the ES3/ES4 showed sensitivity 69.5%, specificity 100%, PPV 100%, NPV 71%, and diagnostic accuracy of 82.5%.In the combined evaluation, there was a significant increase in specificity, allowing healthy subjects to be categorized as correctly negative, with a reduction in false positives which also translates into an increase in PPV.

CONCLUSIONS

Elastography alone is not sufficient for a correct diagnostic classification and must be considered as an additional parameter in the study of soft-tissue lesions. Although there was a good agreement between B-mode malignancy criteria and ES3/ES4, there is no significant improvement in sensitivity. Ultrasound assessment, especially of superficial lesions, cannot be separated from an integrated approach that foresees the additional and routine use of the elastographic examination.

High frequency ultrasound vibrational shear wave elastography for preclinical research

Preclinical evaluation of novel therapies using models of cancer is an important tool in cancer research, where imaging can provide non-invasive tools to characterise the internal structure and function of tumours. The short propagation paths when imaging tumours and organs in small animals allow the use of high frequencies for both ultrasound and shear waves, providing the opportunity for high-resolution shear wave elastography and hence its use for studying the heterogeneity of tissue elasticity, where heterogeneity may be a predictor of tissue response. Here we demonstrate vibrational shear wave elastography (VSWE) using a mechanical actuator to produce high frequency (up to 1000 Hz) shear waves in preclinical tumours, an alternative to the majority of preclinical ultrasound SWE studies where an acoustic radiation force impulse is required to create a relatively low-frequency broad-band shear-wave pulse. We implement VSWE with a high frequency (17.8 MHz) probe running a focused line-by-line ultrasound imaging sequence which as expected was found to offer improved detection of 1000 Hz shear waves over an ultrafast planar wave imaging sequence in a homogenous tissue-mimicking phantom. We test the VSWE in anex vivotumour xenograft, demonstrating the ability to detect shear waves up to 10 mm from the contactor position at 1000 Hz. By reducing the kernel size used for shear wave speed estimation to 1 mm we are able to produce shear wave speed images with spatial resolution of this order. Finally, we present VSWE data from xenograft tumoursin vivo, demonstrating the feasibility of the technique in mice under isoflurane sedation. Mean shear wave speeds in the tumours are in good agreements with those reported by previous authors. Characterising the frequency dependence of shear wave speed demonstrates the potential to quantify the viscoelastic properties of tumoursin vivo.

Effectiveness of Quantitative Shear Wave Elastography for the Prediction of Axillary Lymph Node Metastasis

Objective

Invasive breast cancer can be metastasized through axillary lymph nodes (LNs). This study was to evaluate the effectiveness of quantitative shear wave elastography (SWE) to predict axillary LN metastasis, which also provides prognostic implication of SWE as a histopathologic element of invasive breast cancer.

Methods

72 prospectively enrolled patients received B-mode ultrasound (BUS) and SWE, and the elasticity index (EI) of SWE at the stiffest part of lymph nodes (LNs) was measured. EI of SWE was closely associated with pathologic results and the histopathologic elements. The receiver operating characteristics (ROC) curve was drawn to evaluate the optimal cut-off value for the assessment of disease severity.

Results

A significantly longer short-axis diameter and a larger maximal cortex were observed in malignant LNs than that in healthy LNs. The absence of the hilum was associated with metastatic LNs. The EI of SWE varied markedly between the benign and malignant LNs. The combination of E_{max and} BUS showed higher area under the curve (AUC) than BUS alone to predict metastatic LNs (0.7762 vs. 0.7230). EI of SWE in malignant lymph nodes those with extranodal extension are higher than those without extranodal extension.

Conclusions

Quantitative SWE provides a viable alternative for the assessment of axillary LN and shows great potential to predict pathological prognostic elements of metastatic axillary LNs in invasive breast cancer. Joint use of SWE and BUS allows examination of the predictive outcome of BUS for axillary lymph node metastasis in invasive breast cancer.

Evaluation of Optic Nerve Head Biomechanical Properties in Pseudoexfoliation Glaucoma with Real-time Elastography

PURPOSE

To investigate the biomechanical properties of the optic nerve head in patients with Pseudoexfoliation (PEX) glaucoma using Real-time Elastography (RTE) and to compare these results with those of Primary Open Angle Glaucoma (POAG) patients and healthy subjects.

METHODS

Twenty eyes of 20 PEX glaucoma patients (PEX group), 20 eyes of 20 POAG patients (POAG group), and 20 eyes of 20 healthy subjects (control group) were enrolled in this prospective study. The strain Ratios of Orbital Fat to Optic Nerve head (ROFON) and lateral rectus muscle to optic nerve head (RLRON) were determined. Comparisons were performed using Chi-square, Kruskal Wallis, Mann-Whitney U, and One-way ANOVA tests.

RESULTS

The strain ratios of orbital fat to optic nerve head were 2.34, 6.85 and 1.76 in PEX glaucoma, POAG, and control groups, respectively (p<0.001). The strain ratios of the lateral rectus muscle to the optic nerve head were 0.51, 0.82, and 0.55 in PEX glaucoma, POAG, and control groups, respectively (p=0.256).

CONCLUSION

The strain ratios of orbital fat to optic nerve head were different in PEX glaucoma patients than in POAG and control groups. RTE can provide biomechanical assessment of the optic nerve head in a non-invasive, quick, easily accessible, and user-friendly manner.

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.

Real-time ultrasound elastographic evaluation of extraocular muscle involvement in Graves' ophthalmopathy

Purpose: To evaluate the affected extraocular muscles (EOMs) of patients with Graves' ophthalmopathy (GO) using real-time ultrasound elastography (UE) and to compare these results with those of healthy subjects.Methods: This prospective, comparative case series included 70 eyes of 35 patients with moderate-to-severe GO with type 2 orbitopathy (myogenic variant) according to their computed tomography (CT) scans. Forty-six eyes of 23 healthy subjects were evaluated as the control group. The strain ratio of orbital fat to medial rectus was calculated as the ratio of the medial rectus to orbital fat tissue, and the strain ratio of orbital fat to lateral rectus was calculated as the ratio of lateral rectus to orbital fat tissue.Results: The strain ratio of orbital fat to medial rectus was 3.03 ± 1.25 (range: 1.05-5.07) in the GO group, and 0.54 ± 0.20 (range: 0.14-1.08) in the control group (p = .0001). The strain ratio of orbital fat to lateral rectus was 0.97 ± 0.29 (range: 0.56-1.55) in the GO group, and 0.63 ± 0.23 (range: 0.18-1.09) in the control group (p = .0001).Conclusion: By using real-time UE, we found the medial and the lateral recti of GO patients to be stiffer compared to those of healthy subjects.

The Preciseness in Diagnosing Thyroid Malignant Nodules Using Shear-Wave Elastography

Our study aimed to identify more accurate results about the diagnostic role of shear-wave elastography (SWE) for thyroid malignant nodules through a meta-analysis.

Potential articles were searched in PubMed, Embase, and the Cochrane Library databases. Overall sensitivity and specificity with 95% confidence intervals (CIs) was used to represent the diagnostic accuracy of SWE. Summary receiver operating characteristic (ROC) curve was constructed to illustrate the results. In addition, χ² and I² tests were performed to assess heterogeneity. A value of p≤0.05 indicated significant heterogeneity. All the analysis was conducted in Meta-DiSc version 1.4 software.

Twenty studies were included in the analysis. There were a total of 2,907 patients and 3,397 thyroid nodules included in the meta-analysis. Overall sensitivity and specificity were 0.68 (95% CI: 0.66–0.70) and 0.85 (95% CI: 0.84–0.87), respectively. The results showed the area under curve (AUC) was 0.9041, suggesting high accuracy of SWE for differentiating benign and malignant thyroid nodules.

SWE showed high accuracy in identifying thyroid malignant nodules, suggesting it could serve as a diagnostic biomarker in thyroid nodules.

Real-Time Ultrasound Elastographic Features of Primary Open Angle Glaucoma

OBJECTIVE

To investigate the significance of ultrasound elastography for evaluating the optic nerve in patients with primary open angle glaucoma (POAG).

METHODS

This prospective, comparative case series included 40 eyes of 40 patients. Twenty eyes with POAG comprised the POAG group, and 20 eyes of 20 patients without glaucoma who admitted to general eye clinic for near vision glasses comprised the control group. All real-time sonographicelastographic examinations were performed by the same physician. The ratio of orbital fat to optic nerve head (ROFON) and lateral rectus to optic nerve head (RLRON) were determined. Statistical analyses were performed using Student t test, Kolmogorov-Smirnov test, and χ test.

RESULTS

The mean ages of the patients in the study and the control groups were 65.10 ± 7.88 years (range, 48-80 years), and 69.15 ± 7.92 years (range, 55-89 years), respectively (P = 0.113). Mean ROFONs were 1.85 and 6.42 (P < 0.05), and mean RLRONs were 0.65 and 1.07 (P < 0.05) in the control and POAG groups, respectively.

CONCLUSIONS

Real-time elastography showed increased ROFON and RLRON in POAG patients. This can help to understand optic nerve head biomechanics and clarify glaucoma damage in early glaucoma cases.

Identifying Clinically Significant Prostate Cancers using 3-D In Vivo Acoustic Radiation Force Impulse Imaging with Whole-Mount Histology Validation

Overly aggressive prostate cancer (PCa) treatment adversely affects patients and places an unnecessary burden on our health care system. The inability to identify and grade clinically significant PCa lesions is a factor contributing to excessively aggressive PCa treatment, such as radical prostatectomy, instead of more focal, prostate-sparing procedures such as cryotherapy and high-dose radiation therapy. We have performed 3-D in vivo B-mode and acoustic radiation force impulse (ARFI) imaging using a mechanically rotated, side-fire endorectal imaging array to identify regions suspicious for PCa in 29 patients being treated with radical prostatectomies for biopsy-confirmed PCa. Whole-mount histopathology analyses were performed to identify regions of clinically significant/insignificant PCa lesions, atrophy and benign prostatic hyperplasia. Regions of suspicion for PCa were reader-identified in ARFI images based on boundary delineation, contrast, texture and location. These regions of suspicion were compared with histopathology identified lesions using a nearest-neighbor regional localization approach. Of all clinically significant lesions identified on histopathology, 71.4% were also identified using ARFI imaging, including 79.3% of posterior and 33.3% of anterior lesions. Among the ARFI-identified lesions, 79.3% corresponded to clinically significant PCa lesions, with these lesions having higher indices of suspicion than clinically insignificant PCa. ARFI imaging had greater sensitivity for posterior versus anterior lesions because of greater displacement signal-to-noise ratio and finer spatial sampling. Atrophy and benign prostatic hyperplasia can cause appreciable prostate anatomy distortion and heterogeneity that confounds ARFI PCa lesion identification; however, in general, ARFI regions of suspicion did not coincide with these benign pathologies.

Shear Wave Elastography in Head and Neck Lymph Node Assessment: Image Quality and Diagnostic Impact Compared with B-Mode and Doppler Ultrasonography

The aim of this study was to assess the diagnostic performance of shear wave elastography (SWE) in comparison to B-mode and Doppler ultrasonography in differentiating benign from malignant head and neck lymph nodes (HNLNs). Sixty-two HNLNs from 56 patients were prospectively examined using B-mode, Doppler and SWE. The standard of reference was histopathology or cytology and follow-up. Qualitative malignant criteria (hilum infiltration, cortical hypo-echogenicity, irregular margins, abnormal vessels) were assessed on a five-point scale. Four quantitative parameters were obtained: long axis length, short axis length, short axis/long axis ratio, resistive index and maximum shear elasticity modulus (μmax). Diagnostic performance was analyzed with special emphasis on the sub-centimeter HNLN subgroup. Thirty HNLNs were malignant (48%). μmax intra-observer reproducibility was 0.899 (0.728 in sub-centimeter subgroup). Malignant HNLNs were stiffer (μmax = 72.4 ± 59.0 kPa) compared with benign nodes (μmax = 23.3 ± 25.3 kPa) (p < 0.001). Among the quantitative criteria, μmax had the highest diagnostic accuracy (area under the curve = 0.903 ± 0.042), especially in the sub-centimeter subgroup (area under the curve = 0.929 ± 0.045; p < 0.001) in which the area under the curve was significantly higher compared with the other quantitative criteria (p < 0.05). The additional use of SWE combined with B-mode tended to improve diagnostic accuracy (p > 0.05). SWE is a promising reproducible quantitative tool with which to predict malignant HNLNs, especially sub-centimeter nodes.

Shear wave elastography in evaluation of cervical lymph node metastasis of papillary thyroid carcinoma: elasticity index as a prognostic implication

PURPOSE

The aim of this study was to evaluate the usefulness of shear wave elastography (SWE) for predicting cervical lymph node (LN) metastasis and the prognostic implication of SWE as histopathologic factors of papillary thyroid carcinoma (PTC).

METHODS

Eighty-four LNs of 66 patients with PTC underwent B-mode ultrasonography (BUS) and SWE before ultrasound-guided fine-needle aspiration biopsy or preoperative evaluation. SWE elasticity indices (EI) of mean (Emean), minimum (Emin), maximum (Emax) and the ratio of Emean in LNs and surrounding muscle (Emean-m) were measured at the stiffest portion of LNs (kPa). SWE EI were correlated with the pathologic diagnosis and the histopathologic findings, including number and size of metastatic LNs, the ratio of the number of metastatic LN/dissected LN, and the presence of extranodal extension. Diagnostic performances of SWE EI and BUS for predicting LN metastasis were assessed using receiver operating curve analysis.

RESULTS

All SWE EI were significantly higher in metastatic LNs than in benign LNs (p < 0.005). Combined Emean [area under the curve (AUC) 0.811] or Emin (AUC 0.812) with BUS showed significantly higher AUC than BUS (0.738) for predicting metastatic LNs (p = 0.041 and 0.033, respectively). The number of positive LNs/dissected LNs and the largest LN size were significantly correlated with SWE EI (p < 0.05 and p < 0.005, respectively). Metastatic LNs with extranodal extension showed significantly higher SWE EI (p < 0.005) than those without extranodal extension.

CONCLUSIONS

Combined use of SWE and BUS was adjunctive to the diagnostic performance of BUS for the prediction of LN metastasis of PTC, and quantitative SWE could predict pathologic prognostic factors of LN metastasis of PTC.

Sonoelastography: musculoskeletal applications

All participants for image samplings provided written informed consent. Conventional B-mode ultrasonography (US) has been widely utilized for musculoskeletal problems as a first-line approach because of the advantages of real-time access and the relatively low cost. The biomechanical properties of soft tissues reflect to some degree the pathophysiology of the musculoskeletal disorder. Sonoelastography is an in situ method that can be used to assess the mechanical properties of soft tissue qualitatively and quantitatively through US imaging techniques. Sonoelastography has demonstrated feasibility in the diagnosis of cancers of the breast and liver, and in some preliminary work, in several musculoskeletal disorders. The main types of sonoelastography are compression elastography, shear-wave elastography, and transient elastography. In this article, the current knowledge of sonoelastographic techniques and their use in musculoskeletal imaging will be reviewed.

Application of real-time ultrasound elastography for discrimination of low- and high-grade serous ovarian carcinoma

OBJECTIVES

The purpose of this study was to evaluate real-time qualitative ultrasound elastography as an adjunct to conventional sonography for discrimination of low- and high-grade serous ovarian carcinoma.

METHODS

Eighty-six patients suspected of having serous ovarian cancer on the basis of clinical and biochemical evaluations underwent transvaginal and transabdominal sonography and then elastography and later underwent surgery.

RESULTS

Histopathologic analysis revealed 64 serous ovarian carcinomas (74.4%): 39 (60.9%) high grade and 25 (39.1%) low grade. The mean elasticity score ± SD was statistically significantly higher for low-grade lesions (3.40 ± 0.76) than high-grade lesions (2.08 ± 0.58; P < .001). There was a trend for high-grade lesions to be less stiff than low-grade lesions due to rapidly developing necrosis; conversely, low-grade lesions developed relatively slowly so that their solid areas were stiffer and less elastic. The median elasticity score for low-grade lesions (based on a 4-point scale used to grade cervical lymph nodes) was 4 (stiffest), and the score for high-grade lesions was 2. When the score of 4 was used for diagnosis of low-grade carcinoma, elastography had 56.0% sensitivity, 100% specificity, a 100% positive predictive value, a 78.0% negative predictive value, and 82.8% accuracy. When the score of 2 was used for the diagnosis of high-grade carcinoma, elastography had 66.7% sensitivity, 84.0% specificity, an 86.7% positive predictive value, a 61.8% negative predictive value, and 73.4% accuracy.

CONCLUSIONS

Our results suggest that ultrasound elastography could be helpful for discrimination of low- and high-grade serous ovarian carcinoma. Low-grade lesions are stiffer and not as elastic as high-grade lesions.

Early results of real-time qualitative sonoelastography in the evaluation of parotid gland masses: a study with histopathological correlation

BACKGROUND

Sonoelastography has been used to differentiate malignant from benign lesions in numerous types of tissues including breast, prostate, liver, blood vessels, thyroid, musculoskeletal structures, and salivary glands.

PURPOSE

To evaluate the efficacy and application of real-time qualitative sonoelastography in the differentiation of benign and malignant focal parotid gland lesions.

MATERIAL AND METHODS

A total of 75 patients (36 boys/men, 39 girls/women; age range, 10-83 years) with 81 lesions were evaluated prospectively by sonoelastography performed and interpreted by two expert radiologists. The results of these experts classification and scoring of lesions according to relative stiffness of the mass were compared with each other and with histopathological findings. The interpretation of sonoelastography scores of 1-4 were as follows: 1, soft; 2, mostly soft; 3, mostly stiff; and 4, stiff.

RESULTS

The kappa statistic of 0.508 (P < 0.001) indicated moderate agreement between the two radiologists. The sonoelastography scores correctly diagnosed 30 of 49 benign tumors (sensitivity, 61.2%) and 19 of 32 malignant tumors (specificity, 59.4%). The area under the receiver-operating characteristic curve was 0.603. The diagnostic value of sonoelastography for evaluating pleomorphic adenomas, Warthin tumors, adenoid cystic carcinoma, and high-grade tumors was low, whereas the diagnostic rates for low-grade tumors such as mucoepidermoid carcinoma, acinic cell carcinoma, and metastases of basal cell carcinoma were better with sonoelastography.

CONCLUSION

Although sonoelastography seems to be promising in the differentiating of low-grade malignancies, the primary role of radiology is currently limited to determination of localization, size, and morphology of parotid tumors.

Value of ultrasound elastography in assessment of enlarged cervical lymph nodes

BACKGROUND

To investigate the value of ultrasound elastography (UE) in the differentiation between benign and malignant enlarged cervical lymph nodes (LNs).

METHODS

B-mode ultrasound, power Doppler imaging and UE were examined to determine LN characteristics. Two kinds of methods, 4 scores of elastographic classification and a strain ratio (SR) were used to evaluate the ultrasound elastograms.

RESULTS

The cutoff point of SR had high utility in differential diagnosis of benign and malignant of cervical lymph nodes, with good sensitivity, specificity and accuracy.

CONCLUSION

UE is an important aid in differential diagnosis of benign and malignant cervical LNs.

Is sonoelastography a helpful method for evaluation of parotid tumors?

Sonoelastography is a novel technique, useful in a noninvasive assessment of lesions in multiple organs. The aim of the study was to examine whether the combination of conventional ultrasonography (US) with sonoelastography might improve the reliability of parotid tumor evaluation. Fourty-three consecutive patients with parotid tumors were surgically treated at a single tertiary center at the Department of Otolaryngology, Head and Neck Surgery. The sample included 27 women and 16 men, aged 15–80 (the mean age = 54 years). The reference group constituted of 54 healthy volunteers. High resolution grayscale ultrasonography (US) was performed preoperatively using a 15 MHz linear array transducer. Elastograms (ES) were scored by the conventional Ueno 5-point scale from ES1 (blue-soft) to ES5 (the entire lesion and surrounding area shaded red-stiff). In addition, detailed stiffness values in kPa were collected. The group consisted of 33 patients with benign and 10 patients with malignant tumors. The mean stiffness value was 146.6 kPa in 10 malignant tumors (mostly ES4) and 88.7 kPa in 33 benign tumors (mostly ES2 and ES3). The differences in tissue stiffness between normal parotid parenchyma in the reference group and the mean value for all tumors in the examined group were statistically significant (p < 0.001), and so was the case with the differences between the benign and malignant tumors (p < 0.001). Low stiffness scores (ES1,2) were found in 2 malignant and 15 benign tumors while high scores (ES3,4) were found in 8 malignancies and 18 benign tumors. Sonoelastography overlapping elasticity to the grayscale images supports additional informations. Preferential selection of the lesions characterized by high stiffness (ES4) improves the differential diagnosis of parotid tumors but the large degree of uncertainty of this method should also be pointed out.

A pilot study evaluating real-time shear wave ultrasound elastography of miscellaneous non-nodal neck masses in a routine head and neck ultrasound clinic

A pilot study was performed to evaluate shear wave ultrasound elastography (SWE) for miscellaneous non-nodal/salivary/thyroid neck lesions. Forty-six lesions undergoing conventional sonography also underwent SWE. Elastic moduli from the stiffest areas in lesions were correlated with diagnosis. Forty lesions were benign (9 lipomas, 8 lymphatic/venous vascular malformations, 7 thyroglossal duct cysts, 4 branchial cleft cysts, 4 abscesses/phlegmons, 3 neurogenic tumors and 1 each of paraganglioma, sebaceous cyst, pseudotumor, hypertrophic scar, ranula) and 6 were malignant (1 malignant fibrous histiocytoma, 2 primary squamous cell carcinomas and 3 intramuscular metastases [2 squamous cell carcinomas, 1 malignant melanoma]).Median stiffness of malignant lesions (226.4 kPa, range 55.6 to 300.0) was higher than benign lesions (28.3 kPa, range 4.0 to 300.0) (p < 0.001). SWE cut-off with highest accuracy (174.4 kPa) achieved 83.3% sensitivity and 97.5% specificity, and the cut-off with 100% sensitivity (55.6 kPa) achieved 75% specificity. All malignant lesions were suspected on conventional sonography. The preliminary data indicate that SWE is feasible for miscellaneous neck lesions. SWE would not have altered management in terms of detecting undisclosed malignancies, although as a quantitative technique, it may increase the diagnostic confidence of less experienced operators performing head and neck ultrasound.

The utility of ultrasound elastography and MicroPure imaging in the differentiation of benign and malignant thyroid nodules

OBJECTIVE

The aim of this study was to evaluate the utility of ultrasound elastography and MicroPure imaging in the differential diagnosis of benign and malignant thyroid nodules.

SUBJECTS AND METHODS

A total of 74 consecutive patients (65 women and nine men; age range, 21-80 years; mean [± SD] age, 51 ± 12.7 years) with thyroid nodules, who were referred for fine-needle aspiration biopsy by endocrinology or general surgery clinics, were prospectively examined using B-mode ultrasound, ultrasound elastography, and MicroPure imaging. The strain value ratio (strain index) of thyroid nodules was calculated. Patients with malignant or intermediate fine-needle aspiration biopsy results underwent thyroid surgery.

RESULTS

Using MicroPure imaging, 17 of 65 benign thyroid nodules (26.6%) and three of nine malignant thyroid nodules (33.3%) were found to contain microcalcifications. The sensitivity, specificity, negative predictive value, positive predictive value, and the accuracy rate of MicroPure imaging were 42.9%, 80.6%, 93.1%, 18.8%, and 77%, respectively. By using receiver operating characteristic analysis, the best cutoff point (2.31) was computed (area under the curve, 0.87; p < 0.001). The sensitivity, specificity, negative predictive value, positive predictive value and accuracy rate of the strain index values were 85.7%, 82.1%, 98.2%, 33.3%, and 82.4%, respectively, when the best cutoff point of 2.31 was used (p = 0.001). The p value (x = malign) was 0.96 for a strain index value higher than 2.31.

CONCLUSION

This preliminary study indicated that ultrasound elastography and MicroPure imaging can be used for the differentiation of benign and malignant thyroid nodules.

Medical ultrasound: imaging of soft tissue strain and elasticity

After X-radiography, ultrasound is now the most common of all the medical imaging technologies. For millennia, manual palpation has been used to assist in diagnosis, but it is subjective and restricted to larger and more superficial structures. Following an introduction to the subject of elasticity, the elasticity of biological soft tissues is discussed and published data are presented. The basic physical principles of pulse-echo and Doppler ultrasonic techniques are explained. The history of ultrasonic imaging of soft tissue strain and elasticity is summarized, together with a brief critique of previously published reviews. The relevant techniques-low-frequency vibration, step, freehand and physiological displacement, and radiation force (displacement, impulse, shear wave and acoustic emission)-are described. Tissue-mimicking materials are indispensible for the assessment of these techniques and their characteristics are reported. Emerging clinical applications in breast disease, cardiology, dermatology, gastroenterology, gynaecology, minimally invasive surgery, musculoskeletal studies, radiotherapy, tissue engineering, urology and vascular disease are critically discussed. It is concluded that ultrasonic imaging of soft tissue strain and elasticity is now sufficiently well developed to have clinical utility. The potential for further research is examined and it is anticipated that the technology will become a powerful mainstream investigative tool.

Real-time qualitative ultrasound elastography of cervical lymph nodes in routine clinical practice: interobserver agreement and correlation with malignancy

To evaluate real-time qualitative ultrasound (US) elastography for cervical lymphadenopathy in routine clinical practice, 74 nodes (37 malignant, 37 benign) in 74 patients undergoing sonography underwent US elastography prior to fine needle aspiration for cytology. Dynamic cine loops of elasticity imaging displayed using a chromatic-scale were qualitatively scored by three independent observers for the proportion of stiff areas from ES1-4 (soft to stiff). There was fair to good interobserver agreement as indicated by weighted kappa (κ) statistic from 0.374 to 0.738. Median ES for benign and malignant nodes were 2 and 3 respectively. ES was higher in malignant nodes (p = 0.0003-0.0049, Mann Whitney U tests) although areas under receiver operating characteristic curves (0.68-0.74) indicated suboptimal discrimination. The optimal discriminatory cut-off, ES > 2, achieved only 62.2% sensitivity, 83.8% specificity and 73% accuracy for malignancy. Improvements in reliability and accuracy of real-time qualitative ultrasound elastography are required for it to be adopted into routine clinical practice.

Imaging the elastic properties of tissue: the 20 year perspective

After 20 years of innovation in techniques that specifically image the biomechanical properties of tissue, the evolution of elastographic imaging can be viewed from its infancy, through a proliferation of approaches to the problem to incorporation on research and then clinical imaging platforms. Ultimately this activity has culminated in clinical trials and improved care for patients. This remarkable progression represents a leading example of translational research that begins with fundamentals of science and engineering and progresses to needed improvements in diagnostic and monitoring capabilities applied to major categories of disease, surgery and interventional procedures. This review summarizes the fundamental principles, the timeline of developments in major categories of elastographic imaging, and concludes with recent results from clinical trials and forward-looking issues.

Real-time qualitative ultrasound elastography of miscellaneous non-nodal neck masses: applications and limitations

To evaluate real-time qualitative ultrasound elastography as an adjunct to conventional sonography for evaluation of non-nodal neck masses identified in routine clinical practice, 52 consecutive masses in 49 patients underwent both techniques. Lesion stiffness was graded visually on chromatic-scale elastograms from ES0-3 (low to high). Diagnosis was based on (cyto)pathology (11), corroborative cross-sectional imaging (18) or characteristic conventional sonography (23). There were 16 lipomas, 15 lymphatic/venous vascular malformations (LVVMs), six neurogenic tumours/neuromas, five thyroglossal duct cysts (TGCs), five (epi)dermoids, three abscesses, one second-arch branchial cleft cyst (BCC), and one soft-tissue metastasis. In general terms, lesion stiffness was high (ES2-3) for neurogenic tumours/neuromas, (epi)dermoids and metastasis, and low (ES0-1) for lipomas, LVVM, TGCs and BCC. Abscesses displayed variable stiffness according to fluid content. Technical limitations and artefacts of elastograms were identified. Data from real-time qualitative ultrasound elastography may be a useful adjunct to sonography for diagnosis of non-nodal neck masses.

Evaluation of real-time qualitative sonoelastography of focal lesions in the parotid and submandibular glands: applications and limitations

OBJECTIVE

To evaluate qualitative ultrasound elastography for focal salivary gland masses identified during routine clinical practice.

METHODS

Sixty-five parotid or submandibular masses in 61 patients underwent real-time qualitative ultrasound elastography and were scored on colour-scaled elastograms in terms of their stiffness relative to adjacent normal salivary parenchyma from ES 1 (soft) to ES 4 (stiff). This was correlated with diagnosis from aspiration cytology or histology.

RESULTS

There were 29 Warthin's tumours (WTs), 23 pleomorphic adenomas (PAs), 2 adenoid cystic carcinomas, 1 adenosquamous carcinoma, 1 nodal metastasis from nasopharyngeal carcinoma, 1 lymphoma (2 deposits), 3 Kuttner tumours and 4 cases of Kimura's disease. ES scores showed clustering according to pathological condition. In this respect, PAs were firmer than WTs (P < 0.004, Fisher's exact test). Nine, 19, 14 and 17 of the benign masses and 0, 1, 2 and 3 of the malignant masses were ES 1, 2, 3 and 4 respectively. All three primary salivary malignancies were ES 4 compared with 1/29 WTs and 16/23 PAs.

CONCLUSION

These preliminary findings suggest that qualitative real-time ultrasound elastography, although an ancillary technique to conventional ultrasound in the salivary glands, is likely to have a poor ability to discriminate benign lesions (particularly PAs) from malignant disease.

Use of sonographic elastography of the masseter muscles for optimizing massage pressure: a preliminary study

To examine the stiffness of the masseter muscle using sonographic elastography and to investigate its relationship with the most comfortable massage pressure in the healthy volunteers. In 16 healthy volunteers (10 men and 6 women), the Masseter Stiffness Index (MSI) was measured using EUB-7000 real-time tissue elastography. They underwent massages at three kinds of pressures using the Oral Rehabilitation Robot (WAO-1). A subjective evaluation regarding the comfort of each massage was recorded on the visual analogue scale. Elastography was also performed in two patients with temporomandibular joint dysfunction with the myofascial pain. The mean MSI of the right and left muscles in the healthy volunteers were 0.85 +/- 0.44 and 0.74 +/- 0.35 respectively. There was no significant difference between the right and left MSI in the healthy volunteers. The MSI was related to massage pressure at which the healthy men felt most comfortable. The two temporomandibular disorder patients had a large laterality in the MSI. The MSI was related to the most comfortable massage pressure in the healthy men. The MSI can be one index for determining the massage pressure.

Accuracy of sonographic elastography in the differential diagnosis of enlarged cervical lymph nodes: comparison with conventional B-mode sonography

OBJECTIVE

The purpose of our study was to evaluate the diagnostic performance of sonographic elastography and B-mode sonography individually and combined in the differentiation of reactively and metastatically enlarged cervical lymph nodes.

SUBJECTS AND METHODS

Eighty-five lymph nodes (metastatic, n = 53; reactive, n = 32) from 37 patients were examined by both elastography and B-mode sonography in this prospective study. Elastographic patterns were determined on the distribution and percentage of the lymph node area with high elasticity (hard), with pattern 1 being an absent or very small hard area to pattern 5, a hard area occupying the entire lymph node. The cutoff line for reactive versus metastatic was set between patterns 2 and 3; patterns 3-5 were considered metastatic. B-mode sonographic diagnosis was based on the sum of scores for five criteria: short-axis diameter, shape, border (regular or irregular), echogenicity (homogeneous or inhomogeneous), and hilum (present or absent). The cutoff line for reactive versus metastatic was set between scores 6 and 7; scores 5 and 6 were considered reactive, and scores 7-10, metastatic.

RESULTS

Sensitivity, specificity, and accuracy of B-mode sonography were 98%, 59%, and 84%, respectively; 83%, 100%, and 89% for elastography; and 92%, 94%, and 93% for the combined evaluation.

CONCLUSION

The combination of highly specific elastography with highly sensitive conventional B-mode sonography has the potential to further improve the diagnosis of metastatic enlarged cervical lymph nodes.

Quantitative characterization of viscoelastic properties of human prostate correlated with histology

Quantification of mechanical properties of human prostate tissue is important for developing sonoelastography for prostate cancer detection. In this study, we characterized the frequency-dependent complex Young's modulus of normal and cancerous prostate tissues in vitro by using stress relaxation testing and viscoelastic tissue modeling methods. After radical prostatectomy, small cylindrical tissue samples were acquired in the posterior region of each prostate. A total of 17 samples from eight human prostates were obtained and tested. Stress relaxation tests on prostate samples produced repeatable results that fit a viscoelastic Kelvin-Voigt fractional derivative (KVFD) model (r(2)>0.97). For normal (n = 8) and cancerous (n = 9) prostate samples, the average magnitudes of the complex Young's moduli (|E*|) were 15.9 +/- 5.9 kPa and 40.4 +/- 15.7 kPa at 150 Hz, respectively, giving an elastic contrast of 2.6:1. Nine two-sample t-tests indicated that there are significant differences between stiffness of normal and cancerous prostate tissues in the same gland (p < 0.01). This study contributes to the current limited knowledge on the viscoelastic properties of the human prostate, and the inherent elastic contrast produced by cancer.

Imaging and estimation of tissue elasticity by ultrasound

Ultrasound (US) elasticity imaging is an extension of the ancient art of palpation and of earlier US methods for viewing tissue stiffness such as echopalpation. Elasticity images consist of either an image of strain in response to force or an image of estimated elastic modulus. There are 3 main types of US elasticity imaging: elastography that tracks tissue movement during compression to obtain an estimate of strain, sonoelastography that uses color Doppler to generate an image of tissue movement in response to external vibrations, and tracking of shear wave propagation through tissue to obtain the elastic modulus. Other modalities may be used for elasticity imaging, the most powerful being magnetic resonance elastography. With 4 commercial US scanners already offering elastography and more to follow, US-based methods may be the most widely used for the near future. Elasticity imaging is possible for nearly every tissue. Breast mass elastography has potential for enhancing the specificity of US and mammography for cancer detection. Lesions in the thyroid, prostate gland, pancreas, and lymph nodes have been successfully imaged using elastography. Evaluation of diffuse disease including cirrhosis and transplant rejection is also possible using both imaging and nonimaging methods. Vascular imaging including myocardium, blood vessel wall, plaque, and venous thrombi has also shown great potential. Elasticity imaging may also be important in assessing the progress of ablation therapy. Recent work in assessing porous materials using elastography suggests that the technique may be useful in monitoring the severity of lymphedema.

Real-time shear velocity imaging using sonoelastographic techniques

In this paper, a novel sonoelastographic technique for estimating local shear velocities from propagating shear wave interference patterns (termed crawling waves) is introduced. A relationship between the local crawling wave spatial phase derivatives and local shear wave velocity is derived with phase derivatives estimated using an autocorrelation technique. Results from homogeneous phantoms demonstrate the ability of sonoelastographic shear velocity imaging to quantify the true underlying shear velocity distributions as verified using time-of-flight measurements. Heterogeneous phantom results reveal the capacity for lesion detection and shear velocity quantification as validated from mechanical measurements on phantom samples. Experimental results obtained from a prostate specimen illustrated feasibility for shear velocity imaging in tissue. More importantly, high-contrast visualization of focal carcinomas was demonstrated introducing the clinical potential of this novel sonoelastographic imaging technique.