Xianfen Diao

Highly Sensitive Computer Aided Diagnosis System for Breast Tumor Based on Color Doppler Flow Images

A computer-aided diagnosis (CAD) system for breast tumor based on color Doppler flow images is proposed. Our system consists of automatic segmentation, feature extraction, and classification of breast tumors. First, the B-mode grayscale image containing anatomical information was separated from a color Doppler flow image (CDFI). Second, the boundary of the breast tumor was automatically defined in the B-mode image and then morphologic and gray features were extracted. Third, an optimal feature vector was created using K-means cluster algorithm. Then a back-propagation (BP) artificial neural network (ANN) was used to classify breast tumors as benign, malignant or uncertain. Finally, the blood flow feature was extracted selectively from the CDFI, and was used to classify the uncertain tumor as benign or malignant. Experiments on 500 cases show that the proposed system yields an accuracy of 100% for the malignant and 80.8% for the benign classification. Comparing with other systems, the advantage of our system is that it has a much lower percentage of malignant tumor misdiagnosis.

Enhanced delivery of paclitaxel liposomes using focused ultrasound with microbubbles for treating nude mice bearing intracranial glioblastoma xenografts

Paclitaxel liposomes (PTX-LIPO) are a clinically promising antineoplastic drug formulation for the treatment of various extracranial cancers, excluding glioblastoma. A main reason for this is the presence of the blood–brain barrier (BBB) or blood–tumor barrier (BTB), preventing liposomal drugs from crossing at a therapeutically meaningful level. Focused ultrasound (FUS) in conjunction with microbubbles (MBs) has been suggested in many studies to be an effective approach to increase the BBB or BTB permeability. In this study, we investigated the feasibility of enhancing the delivery of PTX-LIPO in intracranial glioblastoma-bearing nude mice using pulsed low-intensity FUS exposure in the presence of MBs. Our results showed that the delivery efficiency of PTX-LIPO could be effectively improved in terms of the penetration of both the BBB in vitro and BTB in vivo by pulsed FUS sonication with a 10 ms pulse length and 1 Hz pulse repetition frequency at 0.64 MPa peak-rarefactional pressure in the presence of MBs. Quantitative analysis showed that a 2-fold higher drug concentration had accumulated in the glioblastoma 3 h after FUS treatment, with 7.20±1.18 µg PTX per g glioma tissue. Longitudinal magnetic resonance imaging analysis illustrated that the intracranial glioblastoma progression in nude mice treated with PTX-LIPO delivered via FUS with MBs was suppressed consistently for 4 weeks compared to the untreated group. The medium survival time of these tumor-bearing nude mice was significantly prolonged by 20.8%, compared to the untreated nude mice. Immunohistochemical analysis further confirmed the antiproliferation effect and cell apoptosis induction. Our study demonstrated that noninvasive low-intensity FUS with MBs can be used as an effective approach to deliver PTX-LIPO in order to improve their chemotherapy efficacy toward glioblastoma.

Measurement of Quantitative Viscoelasticity of Bovine Corneas Based on Lamb Wave Dispersion Properties

The viscoelastic properties of the human cornea can provide valuable information for clinical applications such as the early detection of corneal diseases, better management of corneal surgery and treatment and more accurate measurement of intra-ocular pressure. However, few techniques are capable of quantitatively and non-destructively assessing corneal biomechanics in vivo. The cornea can be regarded as a thin plate in which the vibration induced by an external vibrator propagates as a Lamb wave, the properties of which depend on the thickness and biomechanics of the tissue. In this study, pulses of ultrasound radiation force with a repetition frequency of 100 or 200 Hz were applied to the apex of corneas, and the linear-array transducer of a SonixRP system was used to track the tissue motion in the radial direction. Shear elasticity and viscosity were estimated from the phase velocities of the A0 Lamb waves. To assess the effectiveness of the method, some of the corneas were subjected to collagen cross-linking treatment, and the changes in mechanical properties were validated with a tensile test. The results indicated that the shear modulus was 137 ± 37 kPa and the shear viscosity was 3.01 ± 2.45 mPa · s for the group of untreated corneas and 1145 ± 267 kPa and was 0.16 ± 0.11 mPa · s for the treated group, respectively, implying a significant increase in elasticity and a significant decrease in viscosity after collagen cross-linking treatment. This result is in agreement with the results of the mechanical tensile test and with reports in the literature. This initial investigation illustrated the ability of this ultrasound-based method, which uses the velocity dispersion of low-frequency A0 Lamb waves, to quantitatively assess both the elasticity and viscosity of corneas. Future studies could discover ways to optimize this system and to determine the feasibility of using this method in clinical situations.

Broadband detection of dynamic acoustic emission process induced by 6 MV therapeutic X-ray beam from a clinical linear accelerator

Acoustic waves induced by megavoltage photon beam from a clinical linear accelerator (Linac) could provide location and dosimetric information of actual delivered radiation during the course of therapy. In this study, we investigated, for the first time, the technical feasibility of detecting the dynamic acoustic emission process induced by Linac with high SNR. A 6 MV pulsed X-ray beam produced by a Linac was used to excite the X-ray acoustic signals from the water-gelatin phantom and the carbon-gelatin phantom. The induced acoustic signals were collected with a circular plane piston, immersion hydrophone in the frequency range from 100 kHz to 1 MHz perpendicular to the incident X-ray beam direction. The signals were amplified using a preamplifier with a bandwidth of 50 KHz-5 MHz at 34 dB and sampled by a high-speed 14-Bit 100 MS/s data acquisition card. A trigger circuit was designed to synchronize the process of incident pulsed X-ray generation and emitted acoustic signal acquisition. The dynamic X-ray acoustic emission process was consecutively detected from both phantoms with high SNR. The peak amplitude shows a marked increase in the phase of X-ray irradiation and then a rapid fall-off with different dynamic acoustic signal profiles in water-gelatin phantom, suggesting the different processes of accumulation and the absorption of the X-ray energy in different phantom properties. The acoustic emission process of carbon-gelatin phantom lasted more than 5 ms induced by a single X-ray beam with 5 μs pulse width. X-ray acoustic waves detected with high SNR may be used to verify the dose distribution during radiation therapy. Moreover, it may open the opportunity of using X-ray acoustic signals emitted from the tumor to evaluate the radiation treatment efficacy.

Robust topology-adaptive snakes for medical ultrasonic image segmentation

In this study, a modified topology-adaptive snake (T-snake) is proposed for the segmentation of ultrasound image. The algorithm was improved as follows. First, the image is decomposed in the place which has offset from pixels position while snake points are in pixels position. This will reduce the task during calculating intersections between contour and ACID grid. Second, the rule to process topology conflict is simplified and there is no need to judge triangle point in or out of the contour in our model. Third, since ultrasound image has a lot of speckle noise, our external energy is composed by three parts-the gradient-based image energy, the inflation energy and region-based image energy, which can push T-snake into the real edge. The proposed model is tested by both synthetic images and real ultrasound images. Experiments show that our algorithm has the advantage of topological adaptability, less sensitive to the initial contour and speckle noise.

Improved shear wave motion detection using coded excitation for transient elastography

Transient elastography (TE) is well adapted for use in studying liver elasticity. However, because the shear wave motion signal is extracted from the ultrasound signal, the weak ultrasound signal can significantly deteriorate the shear wave motion tracking process and make it challenging to detect the shear wave motion in a severe noise environment, such as within deep tissues and within obese patients. This paper, therefore, investigated the feasibility of implementing coded excitation in TE for shear wave detection, with the hypothesis that coded ultrasound signals can provide robustness to weak ultrasound signals compared with traditional short pulse. The Barker 7, Barker 13, and short pulse were used for detecting the shear wave in the TE application. Two phantom experiments and one in vitro liver experiment were done to explore the performances of the coded excitation in TE measurement. The results show that both coded pulses outperform the short pulse by providing superior shear wave signal-to-noise ratios (SNR), robust shear wave speed measurement, and higher penetration intensity. In conclusion, this study proved the feasibility of applying coded excitation in shear wave detection for TE application. The proposed method has the potential to facilitate robust shear elasticity measurements of tissue.

Assessment of liver fibrosis in chronic hepatitis B via multimodal data

Abstract Assessing liver fibrosis with chronic hepatitis B (CHB) in patients is quite important. Some non-invasive approaches for evaluating liver fibrosis include blood tests and ultrasound elastography. How to effectively combine multiple methods to improve the diagnostic performance remains a challenging problem. The main goal of this paper is to assess and stage liver fibrosis in CHB using feature selection and machine learning methods based on multimodal data. Popular machine learning approaches (e.g., support vector machine (SVM)) and feature selection (FS) were explored to stage the CHB. 16 volunteers and 92 patients with CHB were investigated for liver fibrosis staging based on transient elastography (TE) and acoustical radiation force impulse imaging (ARFI) data. The accuracy of the staging result using FS and a SVM classifier was an accuracy of 90.68% for significant fibrosis (≥F2) and an accuracy of 93.52% for cirrhosis (F4), respectively. The proposed method also increased the sensitivity, specificity, and area under curve (AUC) values for both significant fibrosis and cirrhosis diagnosis, which is very promising for staging liver fibrosis from multimodal information. It outperforms any single method and their linear combination and also achieves a state-of-the-art performance.

Model-dependent and model-independent approaches for evaluating hepatic fibrosis in rat liver using shearwave dispersion ultrasound vibrometry

This study assesses gradations of hepatic fibrosis in rat livers using both model-dependent and model-independent approaches. Liver fibrosis was induced in 37 rats using carbon tetrachloride (CCl4); 6 rats served as the controls. Shear wave velocity as a function of frequency, referred to as velocity dispersion, was measured in vitro by an ultrasound elastography method called shearwave dispersion ultrasound vibrometry (SDUV). For the model-dependent approach, the velocity dispersion data were fit to the Voigt model to solve the viscoelastic modulus. For the model-independent approach, the pattern of the velocity dispersion data was analyzed by linear regression to extract the slope and intercept features. The parameters obtained by both approaches were evaluated separately using a receiver operating characteristic (ROC) curve analysis. The results show that, of all the parameters for differentiating between grade F0-F1 and grade F2-F4 fibrosis, the intercept had the greatest value for the area under the ROC curve. This finding suggests that the model-independent approach may provide an alternative method to the model-dependent approach for staging liver fibrosis.

Computer-Aided Diagnosis of Breast Tumor Based on B-Mode Ultrasound and Color Doppler Flow Imaging

A computerized classification of breast tumor based on B-mode ultrasound and color Doppler flow imaging is proposed. First, the boundary of the breast tumor was manually delineated. Second, five contour features and two gray level features of the tumors were extracted from the B-mode ultrasonic images. Third, an optimal feature vector was created using K-means cluster algorithm. Then a back propagation (BP) artificial neural network (ANN) was used to classify breast tumors as benign, malignant or uncertain. Finally, the blood flow feature was extracted from the color Doppler flow image, which was used to classify the uncertain as benign or malignant. Experiments on 500 cases show that the proposed system yields the accuracy of 100% for the malignant and 80.8% for the benign. According to the result, our system can be used to reduce unnecessary biopsies. Keywords-breast tumor; classification; B-mode ultrasound;color Doppler flow imaging

Dynamic mechanical analysis to assess viscoelasticity of liver tissue in a rat model of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disorder in both developed and developing countries. A noninvasive method of detecting early stage NAFLD and distinguishing non-alcoholic steatohepatitis (NASH) from simple steatosis (SS) would be useful. The over-accumulation of fat in hepatocytes alters the physical microstructure and chemical contents of the liver tissue. This study included dynamic mechanical analysis (DMA) testing on liver samples from a rat model of NAFLD to determine whether the tissue shows any significant changes in viscoelasticity due to the histological changes. Liver steatosis was induced in 57 rats by gavage feeding of a high fat emulsion; 12 rats received a standard diet only and served as controls. Each rat provided 2 or 3 samples for DMA tests. The shear modulus and loss modulus were measured at 9 frequency points evenly-spaced in the range from 1Hz to 41Hz. The phase velocity of shear wave was calculated from the measured modulus. Multivariate T2 test was used to assess the significance of intra-group difference. The results showed significant changes (p < 0.05) in storage modulus in livers with moderate to severe (S2 to S4) steatosis in comparison with livers without steatosis (S0), while the loss modulus demonstrated significant changes earlier in stage S1, indicating that fat accumulation affects the mechanical properties of liver, particularly viscosity. However, no significant differences were observed between the steatosis grades. These results also suggest that mild inflammation may affect the mechanical properties, which requires further verification. These findings provide new information about the mechanical properties of livers with NAFLD in low frequency range and suggest that it is possible to distinguish normal livers from livers with NAFLD.