Diagnosing breast lesions with contrast-enhanced 3-dimensional power Doppler imaging

Role of qualitative contrast-enhanced ultrasound in the diagnosis of malignant breast lesions

Background

Carcinoma breast is the commonest cancer among women. Various authors have studied breast cancer with Contrast-Enhanced Ultrasound (CEUS) with promising results. Despite promising results, the additional cost of post-processing software limits its availability. In this study, we evaluated the utility of CEUS in differentiating malignant from benign breast lesions on regular ultrasound equipment without the use of dedicated software.

Methods

We performed CEUS in 121 women with 121 breast lesions. CEUS was done by creating a custom preset on existing ultrasound equipment with the help of an application specialist authorized by the vendor. Lesions were evaluated qualitatively without the use of any commercial software. The pattern of enhancement i.e. homogenous, heterogeneous, peripheral, or no enhancement, and the number of penetrating vessels i.e., few or multiple were recorded. Results were compared with histopathological diagnosis.

Results

There were a total of 121 breast lesions. The study showed sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 86.67 %, 54.10 %, 65 %, and 80.49% respectively for differentiating benign vs malignant lesions on the basis of the pattern of contrast enhancement. Using penetrating vessels for differentiating malignant lesions from benign lesions, the sensitivity, specificity, PPV, and NPV were found to be 64%, 67.86%, 78.05%, and 51.35% respectively.

Conclusion

CEUS is useful in differentiating malignant from benign breast lesions. It can be easily performed by creating a custom preset on standard ultrasound equipment without the use of expensive software.

Ultrasound Imaging Technologies for Breast Cancer Detection and Management: A Review

Ultrasound imaging is a commonly used modality for breast cancer detection and diagnosis. In this review, we summarize ultrasound imaging technologies and their clinical applications for the management of breast cancer patients. The technologies include ultrasound elastography, contrast-enhanced ultrasound, 3-D ultrasound, automatic breast ultrasound and computer-aided detection of breast ultrasound. We summarize the study results seen in the literature and discuss their future directions. We also provide a review of ultrasound-guided, breast biopsy and the fusion of ultrasound with other imaging modalities, especially magnetic resonance imaging (MRI). For comparison, we also discuss the diagnostic performance of mammography, MRI, positron emission tomography and computed tomography for breast cancer diagnosis at the end of this review. New ultrasound imaging techniques, ultrasound-guided biopsy and the fusion of ultrasound with other modalities provide important tools for the management of breast patients.

Diagnostic Value of Contrast-Enhanced Sonography for Differentiation of Breast Lesions: A Meta-analysis

OBJECTIVES

The purpose of this study was to systematically review and evaluate the diagnostic accuracy of contrast-enhanced sonography in the differential diagnosis of benign and malignant breast lesions.

METHODS

The scientific literature databases PubMed and Embase were comprehensively searched for relevant studies before January 2015. Data were pooled to yield the summary sensitivity, specificity, and diagnostic odds ratio using meta-analysis software.

RESULTS

A total of 29 studies with 2296 lesions were included in the analysis. The pooled sensitivity and specificity were 0.88 (95% confidence interval [CI], 0.86-0.90; inconsistency index [I(2)] = 77.9%) and 0.80 (95% CI, 0.78-0.83; I(2) = 84.0%), respectively. The pooled diagnostic odds ratio was 30.35 (95% CI, 15.75-58.48; I(2)= 82.1%), and the area under the summary receiver operating characteristic curve was 0.9115 (SE, 0.0243).

CONCLUSIONS

The comprehensive results suggest that contrast-enhanced sonography could be a potentially effective method for differential diagnosis of benign and malignant breast lesions.

Quantitative Nonlinear Contrast-Enhanced Ultrasound of the Breast

OBJECTIVE

Breast cancer is the most frequent type of cancer among women (25% of all cancers). The angiogenic process that fuels the growth of tumors is a potential early indicator for differentiating between malignant and benign tumors. Recently, the use of microbubble-based contrast agents combined with ultrasound has allowed the development of contrast agent-specific imaging modes that provide visualization of tumor neovascularity.

CONCLUSION

Contrast-enhanced Doppler, harmonic, and subharmonic imaging are some of the imaging modes that have been investigated for visualizing and quantifying the vascularity in breast tumors.

Role of 3D power Doppler ultrasound in the further characterization of suspicious breast masses

PURPOSE

To investigate effectiveness of vascular indices obtained with 3D power Doppler ultrasound in the further characterization of breast masses and prevention of unnecessary biopsies.

MATERIALS AND METHODS

Between April 2013 and March 2014, 109 patients (age range, 17-85 years; mean age, 47 years) with 117 radiologically or clinically suspicious breast masses were prospectively evaluated with 3DPDUS before biopsy. Mass volume (MV), vascularization index (VI), flow index (FI) and vascularization flow index (VFI) were calculated using Virtual Organ Computer-aided Analysis (VOCAL) software and they were correlated with the final diagnosis. Cutoff values of vascular indices were determinated and diagnostic efficacy was calculated with receiver operating curve (ROC) analysis.

RESULTS

All vascular indices, age of patients and tumor volume were significantly lower in benign masses compared with malignant ones (p<0.001). AUCs were 0.872, 0.867 and 0.789 for VI, VFI and FI, respectively. The diagnostic efficacy of VI (for cutoff 1.1; 83% sensitivity, 82% specificity and 82% accuracy) and VFI (for cutoff 0.4; 80% sensitivity, 83% specificity and 80% accuracy) were significantly higher than FI (for cutoff 33,9; 73% sensitivity, 69% specificity and 71% accuracy). It was found that with the use of vascular indices of 3DPDUS in the further characterization of suspicious breast masses between 24% to 37% of unnecessary biopsies could have been avoided.

CONCLUSION

The vascular indices obtained with 3DPDUS seem reliable in the further characterization of suspicious breast masses and might be used to decrease unnecessary biopsies.

Quantitative analysis of vascular heterogeneity in breast lesions using contrast-enhanced 3-D harmonic and subharmonic ultrasound imaging

Ability to visualize breast lesion vascularity and quantify the vascular heterogeneity using contrast-enhanced 3-D harmonic (HI) and subharmonic (SHI) ultrasound imaging was investigated in a clinical population. Patients (n = 134) identified with breast lesions on mammography were scanned using power Doppler imaging, contrast-enhanced 3-D HI, and 3-D SHI on a modified Logiq 9 scanner (GE Healthcare). A region of interest corresponding to ultrasound contrast agent flow was identified in 4D View (GE Medical Systems) and mapped to raw slice data to generate a map of time-intensity curves for the lesion volume. Time points corresponding to baseline, peak intensity, and washout of ultrasound contrast agent were identified and used to generate and compare vascular heterogeneity plots for malignant and benign lesions. Vascularity was observed with power Doppler imaging in 84 lesions (63 benign and 21 malignant). The 3-D HI showed flow in 8 lesions (5 benign and 3 malignant), whereas 3-D SHI visualized flow in 68 lesions (49 benign and 19 malignant). Analysis of vascular heterogeneity in the 3-D SHI volumes found benign lesions having a significant difference in vascularity between central and peripheral sections (1.71 ± 0.96 vs. 1.13 ± 0.79 dB, p < 0.001, respectively), whereas malignant lesions showed no difference (1.66 ± 1.39 vs. 1.24 ± 1.14 dB, p = 0.24), indicative of more vascular coverage. These preliminary results suggest quantitative evaluation of vascular heterogeneity in breast lesions using contrast-enhanced 3-D SHI is feasible and able to detect variations in vascularity between central and peripheral sections for benign and malignant lesions.

Meta-analysis of contrast-enhanced ultrasound for the differentiation of benign and malignant breast lesions

BACKGROUND

Contrast-enhanced ultrasound (CEUS) is a non-invasive method for the assessment of breast lesions. The accuracy of CEUS in diagnosing of breast cancer has never been systematically assessed.

PURPOSE

To determine the overall performance of CEUS in the differentiation of benign and malignant breast lesions using meta-analysis.

MATERIAL AND METHODS

PubMed, Embase, Cochrane Library, and article references published before October 2012 were searched. Published studies that used histopathologic results as golden reference to assess the diagnostic performance of CEUS in patients suspected of having breast cancer and the data necessary to calculate the diagnostic results were included. The qualities of eligible studies for final meta-analysis were assessed by using the quality assessment of diagnostic studies (QUADAS) instrument. Sensitivity, specificity, summary receiver-operating characteristic (sROC) curves, and area under the curve were calculated to examine the diagnostic performance of CEUS.

RESULTS

Of 16 eligible studies, 957 breast lesions were included in the original meta-analysis, among which heterogeneity arising from factors other than threshold effect was explored. Meta-regression analysis confirmed the contrast agent was the most significant factor cause of heterogeneity (P = 0.0012, relative diagnostic odds ratio [DOR] = 7.06). The use of perfluoro containing microbubbles (Sonovue or Optison) significantly increased the diagnostic precision compared with Levovist. The pooled weighted estimates of sensitivity and specificity for CEUS in the diagnosis of breast lesions were 0.86 (95% confidence interval [CI], 0.83, 0.89) and 0.79 (95% CI, 0.75, 0.83), respectively.

CONCLUSION

CEUS has good sensitivity and specificity in the characterization of breast lesions and can potentially help to select suspicious breast mass for surgery.

Three-dimensional contrast-enhanced sonography in the assessment of breast tumor angiogenesis: correlation with microvessel density and vascular endothelial growth factor expression

OBJECTIVES

The purpose of this study was to differentiate perfusion and vascular characteristics between benign and malignant breast lesions by 3-dimensional contrast-enhanced sonography and evaluate their correlation with microvessel density and vascular endothelial growth factor (VEGF) expression for further clinical exploration.

METHODS

Three-dimensional contrast-enhanced sonography was performed in 183 patients with breast lesions, and sonographic characteristics were carefully observed for further analysis. The mean microvessel density and VEGF expression were measured by immunohistochemical analysis.

RESULTS

Pathologic results showed 35 benign and 148 malignant cases. Malignancy and benignity differed significantly in peripheral vessel characteristics (number, distribution, course, degree of dilatation, and penetrating vessels), rim perfusion and coarseness degree, intratumoral perfusion type, and intratumoral vessel dilatation (P< .05) but not the presence of peripheral and intratumoral vessels and intratumoral perfusion (P > .05). The specificity of penetrating vessels was 88.6% for diagnosing malignancy. The sensitivity, specificity, and accuracy of rim perfusion coarseness were 90.2%, 70.4%, and 85.3% respectively. The sensitivity of the intratumoral perfusion type was 77.8%, whereas the specificity of intratumoral vessel dilatation was 88.9%. Microvessel density and VEGF expression were significantly correlated with perfusion and vascular characteristics (P < .05), except the presence of peripheral vessels, rim perfusion, and intratumoral perfusion (P> .05). The presence of intratumoral vessels was related to VEGF (P< .05) but not microvessel density (P > .05).

CONCLUSIONS

Three-dimensional contrast-enhanced sonographic characteristics were statistically different between benign and malignant breast lesions. Some of them also correlated significantly with microvessel density and VEGF expression and therefore have potential for objective evaluation of tumor angiogenesis.

Two- and three-dimensional contrast-enhanced sonography for assessment of renal tumor vasculature: preliminary observations

OBJECTIVES

The purpose of this study was to show potential applications of 2-dimensional (2D) and 3-dimensional (3D) contrast-enhanced sonography for assessment of the vascularity of benign and malignant renal tumors.

METHODS

Sixty-eight patients with renal tumors were examined with both 2D and reconstructed 3D contrast-enhanced sonography. The contrast enhancement characteristics of benign and malignant renal tumors were compared on both 2D and 3D contrast-enhanced sonograms. The diagnoses of the lesions were made by surgical pathologic examination in 50 patients and by contrast-enhanced computed tomography in 18 patients.

RESULTS

Both 2D and 3D contrast-enhanced sonography showed hypoenhancement with a few small peritumoral feeding blood vessels and regular intratumoral branches in 18 benign tumors, whereas hyperenhancement with multiple irregular peritumoral feeding vessels and tortuous intratumoral branches was shown in 50 malignant tumors. Compared to 2D contrast-enhanced sonography, 3D contrast-enhanced sonography displayed more intratumoral microvessels and spatial distributions, especially for the vessel network, and tortuous branches in the malignant tumors. Compared to 2D contrast-enhanced sonography, 3D contrast-enhanced sonography was better for detecting and displaying renal tumor vascularity, with a statistically significant difference (P < .05).

CONCLUSIONS

Reconstructed 3D contrast-enhanced sonography is a useful complementary tool in addition to 2D contrast-enhanced sonography for assessing the characteristics and distribution of blood vascularity in renal tumors.

Differentiation of focal liver lesions using three-dimensional ultrasonography: Retrospective and prospective studies

AIM: To differentiate focal liver lesions based on enhancement patterns using three-dimensional ultrasonography (3D US) with perflubutane-based contrast agent.

METHODS: Two hundred and eighty two patients with focal liver lesions, including 168 hepatocellular carcinomas (HCCs), 63 metastases, 40 hemangiomas and 11 focal nodular hyperplasias (FNHs), were examined by 3D US with perflubutane-based contrast agent. Tomographic ultrasound images and sonographic angiograms were reconstructed. Among 282 lesions, enhancement patterns of 163 lesions between January 2007 and October 2007 were analyzed retrospectively. Then from November 2007 to May 2008, compared with contrast-enhanced (CE) 2D US, CE 3D US was performed on 119 lesions for prospective differential diagnosis. Sensitivity, specificity, area under receiver operating characteristic curve (A_z) and inter-reader agreement were assessed.

RESULTS: With the tridimensional view, dominant enhancement patterns were revealed as diffuse enhancement or peripheral ring-like enhancement, followed with washout change for HCCs or metastases, respectively, and peripheral nodular enhancement or diffuse enhancement with spoke-wheel arteries, followed by persistent enhancement for hemangiomas or FNHs, respectively. At CE 3D US, the prospective differentiation of lesions showed sensitivity 92% (mean for two readers), specificity 91% and A_z value 0.95 for HCCs, 84%, 97%, and 0.95 for metastases, 91%, 98%, and 0.98 for hemangiomas and 80%, 99%, and 0.99 for FNHs, respectively, while good to excellent inter-reader agreement was achieved. No significant difference exists between prospective diagnosis accuracy at CE 3D US and that at CE 2D US.

CONCLUSION: CE 3D US provides a spatial perspective for liver tumor enhancement, and could help in differentiating focal liver lesions.

Contrast-enhanced breast ultrasonography: imaging features with histopathologic correlation

OBJECTIVE

The purpose of this study was to identify histopathologic correlates for the varied appearances of breast masses on contrast-enhanced ultrasonography (CEUS).

METHODS

Contrast-enhanced ultrasonography was performed in 104 patients (age range, 19-86 years) after administration of a sulfur hexafluoride microbubble contrast agent, and enhancement patterns were classified as no enhancement, peripheral enhancement, homogeneous enhancement, regional enhancement, and heterogeneous enhancement. All patients' histologic slides were reviewed and correlated with CEUS findings.

RESULTS

In malignant masses, heterogeneous enhancement corresponded to tumor cell cords or clusters in a variable amount of desmoplastic stroma. Homogeneous enhancement corresponded to hypercellularity in the whole mass, or ductal carcinoma in situ (DCIS) was predominant. Regional enhancement corresponded to a DCIS component. Peripheral enhancement corresponded to a DCIS component, hypercellularity or adenosis at the periphery, and low-degree cellularity, degeneration, fibrosis, or necrosis in the center. No enhancement was present in 1 case of low-grade DCIS. In benign masses, heterogeneous enhancement corresponded to loose cell proliferation in a more sclerotic stroma. Homogeneous enhancement corresponded to diffuse hypercellularity, an inflammatory cell infiltrate, or intraductal papilloma. Regional enhancement corresponded to focal hypercellularity or intraductal papilloma within a dilated duct. No enhancement corresponded to desmoplastic stroma. Peripheral enhancement was shown in 1 case of granulomatous mastitis with an inflammatory infiltrate at the periphery and necrosis in the center.

CONCLUSIONS

Breast mass CEUS findings correlated with histologic features.

The reproducibility of the virtual organ computer-aided analysis program for evaluating 3-dimensional power Doppler ultrasonography of diffuse thyroid disorders

AIM

The aim of this study was to evaluate the intra- observer and inter-observer reproducibility of 3-dimensional (3D) power Doppler ultrasonography with the virtual organ computer-aided analysis (VOCAL) program for measuring thyroid volume and vascular indices in patients with diffuse thyroid disorders.

MATERIALS AND METHODS

Patients with diffuse goiters were examined by 3D ultrasonography from August 2005 to July 2006. The parameters for vascular assessment included the vascularization index (VI), flow index (FI), vascularization-flow index (VFI), and thyroid size, and were obtained using the VOCAL program. This program used plane A and a 30 degrees rotational step. Intra-observer and inter-observer repeatability are presented as intra-class correlation coefficient (intra-CC) and inter-class correlation coefficient (inter-CC), with values >0.70 being acceptable.

RESULTS

Sixty-three patients in total were enrolled for this study, including 19 patients with simple goiter and 44 patients with autoimmune thyroid disease (AITD) (23 Graves' disease, 21 Hashimoto's thyroiditis). Thyroid volume and 3 vascular indices showed excellent reproducibility in the AITD group (intra- CC>0.9373 and inter-CC>0.8763) and its subgroups. The VI had excellent consistent reproducibility in the simple goiter group (intra-CC>0.8987 and inter-CC>0.8881), but the other parameters did not.

CONCLUSIONS

Based on this study, 3D power Doppler ultrasonography with the VOCAL program is a reliable tool for evaluating diffuse thyroid disorders due to an autoimmune process. The VI is the most reliable parameter.

Three-dimensional contrast-enhanced sonography of vascular patterns of focal liver tumors: pilot study of visualization methods

OBJECTIVE

We investigated visualization methods of 3D sonography with a perflubutane-based contrast agent in the imaging evaluation of vascular patterns of focal liver tumors.

MATERIALS AND METHODS

Eighty-four patients with focal liver tumors underwent automatic scanning with 3D sonography 20-60 seconds after administration of a perflubutane contrast agent. The confirmed final diagnoses were 50 hepatocellular carcinomas, 20 metastatic lesions, nine hemangiomas, and five cases of focal nodular hyperplasia. Tomographic sonographic images reconstructed in 3D parallel slices and rendered sonographic images resembling angiograms were reviewed by two readers.

RESULTS

Sonographic angiograms rendered by maximum intensity of gray values in surface smooth mode showed tumor vessels and early tumor enhancement. The average intensity of gray values with surface texture mode showed unenhanced areas within tumors. Interobserver agreement for classifying enhancement patterns with both tomographic sonography and sonographic angiography was excellent (kappa=0.84). The main pattern, intratumoral vessels with early homogeneous or heterogeneous tumor enhancement, had a sensitivity of 97% (average of both readers), specificity of 94%, and positive predictive value (PPV) of 96% for hepatocellular carcinomas. The presence of tumor vessels with early peripheral ringlike tumor enhancement had a sensitivity of 90%, specificity of 95%, and PPV of 86% for metastatic lesions. Peripheral nodular enhancement had a sensitivity of 84%, specificity of 99%, and PPV of 89% for hemangioma. The presence of spoke-wheel arteries with early tumor enhancement had a sensitivity of 80%, specificity of 100%, and PPV of 100% for focal nodular hyperplasia.

CONCLUSION

Three-dimensional sonography with a perflubutane-based contrast agent is useful in the evaluation of vascular patterns of focal liver tumors.

Comparing contrast-enhanced color flow imaging and pathological measures of breast lesion vascularity

This study was conducted to compare quantifiable measures of vascularity obtained from contrast-enhanced color flow images of breast lesions to pathologic vascularity measurements. Nineteen patients with solid breast masses received Levovist Injection (10 mL at 300 mg/mL; Berlex Laboratories, Montville, NJ, USA). Color flow images of the mass pre and post contrast were obtained using an HDI 3000 scanner (Philips Medical Systems, Bothell, WA, USA) optimized for clinical scanning on an individual basis. After surgical removal, specimens were sectioned in the same planes as the ultrasound images and stained with an endothelial cell marker (CD31). Microvessel area (MVA) and intratumoral microvessel density (MVD) were determined for vessels 10-19 microm, 20-29 microm, 30-39 microm, 40-49 microm and > or =50 microm in diameter using a microscope and image processing software. From the ultrasound images, the number of color pixels before and after contrast administration relative to the total area of the breast mass was calculated as a first-order measure of fractional tumor vascularity. Vascularity measures were compared using reverse stepwise multiple linear regression analysis. In total, 58 pathology slides (with 8,106 frames) and 185 ultrasound images were analyzed. There was a significant increase in flow visualization pre to post Levovist injection (p = 0.001), but no differences were found between the 11 benign and the eight malignant lesions (p > 0.35). Ultrasound vascularity measurements post contrast correlated significantly with pathology (0.15 < or = r2 < or = 0.46; p < 0.03). The 30-39 microm vessel range contributed most significantly to the MVD relationship (p < 0.001), whereas the MVA was mainly influenced by vessels 20-29 microm (p < 0.004). Precontrast ultrasound only correlated with pathology for relative MVA (r2 = 0.16; p = 0.01). In conclusion, contrast-enhanced color flow imaging provides a noninvasive measure of breast tumor neovascularity, corresponding mainly to vessels 20-39 microm in diameter, when used in a typical clinical setting.

Minimally invasive ablative therapies for invasive breast carcinomas: an overview of current literature

BACKGROUND

Minimally invasive treatment may be an alternative to breast-conserving surgery.

METHODS

A structured PubMed, Embase, Cochrane, and Web of Science search was performed. Endpoints studied were feasibility, completeness of ablation, timing of the sentinel node biopsy (SNB), imaging modalities, and treatment-related complications.

RESULTS

A total of 24 articles were retrieved, and the level of evidence varied (2B-4). Mainly phase II studies with a treat-and-resect protocol were analyzed. Up to 100% completeness of ablation was reported for radiofrequency ablation (RFA), cryosurgery, and focused ultrasound (FUS). The oncologic results need further evaluation. Dynamic contrast enhanced MRI seems to be the best method for monitoring treatment response (77% sensitivity, 100% specificity). Ultrasound is suitable for guiding probes into the tumor. There is no consensus on the timing of the SNB.

CONCLUSIONS

All studies on minimally invasive ablative modalities published so far show that these techniques are feasible and safe. At this stage only T1 tumors should be ablated in a clinical trial setting; it is unclear which of the modalities is most suitable.

Breast lesions: imaging with contrast-enhanced subharmonic US--initial experience

PURPOSE

To prospectively compare accuracy of gray-scale subharmonic imaging (SHI) with that of standard gray-scale ultrasonography (US), power Doppler US (with and without contrast material), and mammography for the diagnosis of breast cancer, with histopathologic or clinical follow-up results as the reference standard.

MATERIALS AND METHODS

This HIPAA-compliant pilot study had institutional review board approval; all subjects gave written informed consent. Fourteen women (age range, 37-66 years) had 16 biopsy-proved breast lesions. In SHI, pulses are transmitted at one frequency, but only echoes at half that frequency (the subharmonic) are received. A US scanner was modified to perform gray-scale SHI (transmitting at 4.4 and receiving at 2.2 MHz). Precontrast imaging (gray-scale US and power Doppler) was followed by contrast material-enhanced power Doppler and gray-scale SHI. A reader blinded to mammographic and pathologic findings assessed diagnosis on a six-point scale. Sensitivity, specificity, accuracy, and receiver operating characteristic (ROC) curves were computed for mammography, gray-scale and power Doppler imaging (pre- and postcontrast), and SHI.

RESULTS

Of the 16 lesions, four (25%) were malignant. Mammography had 100% sensitivity and 20% specificity. Sensitivity and specificity, respectively, were 50% and 92% for precontrast imaging and 75% and 75% for contrast-enhanced power Doppler. SHI had 75% sensitivity and 83% specificity. Specificity was higher for all US modes than for mammography (P<.04). There were no significant differences in specificity among US modes or in sensitivity (P>or=.50). Area under the ROC curve for the diagnosis of breast cancer was 0.64 for standard gray-scale US and power Doppler US, 0.67 for contrast-enhanced power Doppler US, 0.76 for mammography, and 0.78 for SHI (P>.20). Contrast enhancement was better with SHI than with power Doppler (100% vs 44% of lesions with good or excellent enhancement; P=.004).

CONCLUSION

SHI appears to improve the diagnosis of breast cancer relative to conventional US and mammography, albeit on the basis of results in a very limited number of subjects.

Solid breast masses: neural network analysis of vascular features at three-dimensional power Doppler US for benign or malignant classification

PURPOSE

To retrospectively evaluate the accuracy of neural network analysis of tumor vascular features at three-dimensional (3D) power Doppler ultrasonography (US) for classification of breast tumors as benign or malignant, with histologic findings as the reference standard.

MATERIALS AND METHODS

This study was approved by the local ethics committee; informed consent was waived. Three-dimensional power Doppler US images of 221 solid breast masses (110 benign, 111 malignant) were obtained in 221 women (mean age, 46 years; range, 25-71 years). After narrowing down vessels to skeletons with a 3D thinning algorithm, six vascular feature values--vessel-to-volume ratio, number of vascular trees, total vessel length, longest path length, number of bifurcations, and vessel diameter-were computed. A neural network was used to classify tumors by using these features. Independent-samples t test and receiver operating characteristic (ROC) curve analysis were used.

RESULTS

Mean values of vessel-to-volume ratio, number of vascular trees, total vessel length, longest path length, number of bifurcations, and vessel diameter were 0.0089 +/- 0.0073 (standard deviation), 26.41 +/- 14.73, 23.02 cm +/- 19.53, 8.44 cm +/- 10.38, 36.31 +/- 37.06, and 0.088 cm +/- 0.021 in malignant tumors, respectively, and 0.0028 +/- 0.0021, 9.69 +/- 6.75, 5.17 cm +/- 4.78, 1.68 cm +/- 1.79, 6.05 +/- 7.55, and 0.064 cm +/- 0.028 in benign tumors, respectively (P < .001 for all six features). Area under ROC curve (A(z)) values of the six features were 0.84, 0.87, 0.87, 0.82, 0.84, and 0.75, respectively. Accuracy, sensitivity, specificity, and positive and negative predictive values were 85% (187 of 221), 83% (96 of 115), 86% (91 of 106), 86% (96 of 111), and 83% (91 of 110), respectively, with A(z) of 0.92 based on all six feature values.

CONCLUSION

Three-dimensional power Doppler US images and neural network analysis of features can aid in classification of breast tumors as benign or malignant.

A review of breast ultrasound

Frequent advances in transducer design, electronics, computers, and signal processing have improved the quality of ultrasound images to the extent that sonography is now a major mode of imaging for the clinical diagnosis of breast cancer. Breast ultrasound is routinely used for differentiating cysts and solid nodules with high specificity. In combination with mammography, ultrasound is used to characterize solid masses as benign or malignant. There is growing interest in using Doppler ultrasound and contrast agents for measuring tumor blood flow and for imaging tumor vascularity. Ease of use and real-time imaging capability make breast ultrasound a method of choice for guiding breast biopsies and other interventional procedures. Breast ultrasound is used in many forms. B-mode is the most common form of imaging for the breast, although compound imaging and harmonic imaging are being increasingly applied to better visualize breast lesions and to reduce image artifacts. These developments, together with the formulation of a standardized lexicon of solid mass features, have improved the diagnostic performance of breast ultrasound. Several approaches that are currently being investigated to further improve performance include: (1) computer-aided-diagnosis; (2) the assessment of tumor vascularity and tumor blood flow with Doppler ultrasound and contrast agents; and (3) tissue elasticity imaging. In the future, ultrasound will play a greater role in differentiating benign from malignant masses and in the diagnosis of breast cancer.

Three-dimensional ultrasound for the assessment of breast lesions

OBJECTIVE

To evaluate the diagnostic accuracy of three-dimensional (3D) ultrasound in comparison with conventional two-dimensional (2D) ultrasound in the characterization of breast lesions.

METHODS

The digitally stored 2D ultrasound images and the corresponding 3D scans of 100 breast lesions (57 malignant, 43 benign) that had been morphologically classified as solid tumors, were independently analyzed by six investigators. Ten 2D and 13 3D ultrasound characteristics were determined. Lesion characterization was classified on a four-point scale and a logistic regression model was used to analyze the data. A receiver-operating characteristics curve (ROC) analysis was performed to determine the diagnostic performance of 2D and 3D ultrasound, respectively.

RESULTS

Ultrasound criteria showed major differences between 2D and 3D ultrasound. Logistic regression revealed the retraction phenomenon in the coronal plane of the 3D ultrasound scan to be a significant and independent factor for lesion characterization. The characteristics determined on the conventional planes of 3D ultrasound differed from those determined on the 2D ultrasound images. The diagnostic accuracy of 2D and 3D ultrasound in the ROC analysis was almost identical (area under the curve 0.846 and 0.851, respectively).

CONCLUSIONS

Ultrasound features on 3D ultrasound differ significantly from those on 2D ultrasound. However, the diagnostic accuracy of both methods is almost identical. 3D ultrasound as an adjunct to conventional 2D ultrasound should be evaluated in larger trials to determine its clinical value in breast imaging.

Combination of digital mammography with semi-automated 3D breast ultrasound

This paper describes work aimed at combining 3D ultrasound with full-field digital mammography via a semi-automatic prototype ultrasound scanning mechanism attached to the digital mammography system gantry. Initial efforts to obtain high x-ray and ultrasound image quality through a compression paddle are proving successful. Registration between the x-ray mammogram and ultrasound image volumes is quite promising when the breast is stably compressed. This prototype system takes advantage of many synergies between the co-registered digital mammography and pulse-echo ultrasound image data used for breast cancer detection and diagnosis. In addition, innovative combinations of advanced US and X-ray applications are being implemented and tested along with the basic modes. The basic and advanced applications are those that should provide relatively independent information about the breast tissues. Advanced applications include x-ray tomosynthesis, for 3D delineation of mammographic structures, and non-linear elasticity and 3D color flow imaging by ultrasound, for mechanical and physiological information unavailable from conventional, non-contrast x-ray and ultrasound imaging.