Chunlan Yang

Temperature distribution analysis of tissue water vaporization during microwave ablation: experiments and simulations.

The temperature distribution in the region near a microwave antenna is a critical factor that affects the entire temperature field during microwave ablation of tissue. It is challenging to predict this distribution precisely, because the temperature in the near-antenna region varies greatly. The effects of water vaporisation and subsequent tissue carbonisation in an ex vivo porcine liver were therefore studied experimentally and in simulations. The enthalpy and high-temperature specific absorption rate (SAR) of liver tissues were calculated and incorporated into the simulation process. The accuracy of predictions for near-field temperatures in our simulations has reached the level where the average maximum error is less than 5°C. In addition, a modified thermal model that accounts for water vaporisation and the change in the SAR distribution pattern is proposed and validated with experiment. The results from this study may be useful in the clinical practice of microwave ablation and can be applied to predict the temperature field in surgical planning.

Correlations Between B-Mode Ultrasonic Image Texture Features and Tissue Temperature in Microwave Ablation

Objective. The purpose of this study was to find the correlations between B‐mode ultrasonic tissue texture features and tissue temperature in microwave ablation. Methods. A total of 20 in vitro porcine liver samples were used for microwave ablation experiments. B‐mode ultrasonic images under various temperatures were acquired. The texture features of the differential images based on the gray level histogram, including the mean of the gray scale (MGS), standard deviation of the gray scale, and entropy of the gray scale (ENT), and those based on the gray level co‐occurrence matrix, including the contrast (CON), angular second moment (ASM), inverse difference moment (IDM), and correlation, were extracted. Correlations between the features and liver sample temperature were analyzed. In addition, water bath heating experiments were also performed on 15 in vitro porcine liver samples for analysis validation. Results. The correlation coefficients across the MGS, ENT, and ASM in 4 directions (0°, 45°, 90°, and 135°), the CON and IDM in 3 directions (45°, 90°, and 135°), and a temperature range of 15°C to 90°C were high and greater than 0.9 during microwave ablation. All texture features of the differential B‐mode ultrasonic images changed with rising temperature from 25°C to 60°C during water bath heating. Conclusions. Changes in image features reflect changes in tissue temperature during microwave ablation.

Automatic Segmentation and 3D Reconstruction of Human Liver Based on CT Image

3D shape reconstruction of the liver from its 2D cross-sections improves the surgeons knowledge of liver anatomy and makes even more complicated liver surgery safe, which can be employed to aid clinical practice as an alternative tool. In this paper, a new method for 3D reconstruction of liver is proposed. It mainly consists of three steps: liver auto-segmentation, surface reconstruction and surface rendering. Firstly, an effective automatic segmentation method based on graph-theory is proposed for extracting liver. Then, NMC algorithm based on a combination of MC and Cuberille algorithms is applied to accomplish surface reconstruction of liver. Finally, surface rendering of liver is implemented by 3D graphics library OpenGL. The method mentioned above is being tested on numerous experiments of 3D reconstruction of liver and results are promising.

Ultrasound monitoring of temperature and coagulation change during tumor treatment with microwave ablation

Microwave ablation therapy has become an important method for tumor treatment in recent years. The temperature and the coagulation region need real-time noninvasive monitoring to ensure the safety and effectiveness during the treatment. The authors reviewed the ultrasonic monitoring methods for tumor microwave ablation therapy both at home and abroad. In addition, the authors also prospected this technique in the future.

Anatomic Differences in Early Blindness: A Deformation‐Based Morphometry MRI Study

This study aims to investigate the regional changes in the early onset of blindness using the deformation‐based morphometry (DBM) method.

Thalamic segmentation based on improved fuzzy connectedness in structural MRI

Thalamic segmentation serves an important function in localizing targets for deep brain stimulation (DBS). However, thalamic nuclei are still difficult to identify clearly from structural MRI. In this study, an improved algorithm based on the fuzzy connectedness framework was developed. Three-dimensional T1-weighted images in axial orientation were acquired through a 3D SPGR sequence by using a 1.5 T GE magnetic resonance scanner. Twenty-five normal images were analyzed using the proposed method, which involved adaptive fuzzy connectedness combined with confidence connectedness (AFCCC). After non-brain tissue removal and contrast enhancement, the seed point was selected manually, and confidence connectedness was used to perform an ROI update automatically. Both image intensity and local gradient were taken as image features in calculating the fuzzy affinity. Moreover, the weight of the features could be automatically adjusted. Thalamus, ventrointermedius (Vim), and subthalamic nucleus were successfully segmented. The results were evaluated with rules, such as similarity degree (SD), union overlap, and false positive. SD of thalamus segmentation reached values higher than 85%. The segmentation results were also compared with those achieved by the region growing and level set methods, respectively. Higher SD of the proposed method, especially in Vim, was achieved. The time cost using AFCCC was low, although it could achieve high accuracy. The proposed method is superior to the traditional fuzzy connectedness framework and involves reduced manual intervention in time saving.

Application Study of Using Ultrasonic Integral Backscatter to Monitor Microwave Coagulation Therapy

Microwave (MW) ablation is a minimally invasive therapeutic strategy for the local treatment of solid malignancies that has received much attention over the past few years. It is very important to detect and evaluate lesions generated by MW during treatment procedures. This study describes one new ultrasonic imaging technique to characterize lesions based on estimation of relative changes in tissue properties derived from backscattered RF data. A single microwave heating antenna was used to produce coagulation in vitro pig liver tissues. The RF signals were recorded as outputs from a modified diagnostic ultrasound system. The integrated backscatter values, which can be used as an indicator of the microstructure and backscattering property of tissues, were calculated in water-bath experiment and MW treatment. The rule of change in integrated backscatter values with temperature has been analyzed by statistics through water-bath experiment. The integrated backscatter ratio values were subsequently used to form images revealing the lesion areas. It is possible using ultrasonic integral backscatter to monitor microwave coagulation. The result shows that this approach can be used to identify the normal and coagulated tissue caused by temperature rise and provide the information of tissue damage.

Features of Ultrasonic Radio Frequency Signal in Microwave Ablation Experiments

The main purpose of this paper was to validate whether the method using features of ultrasonic radio frequency signal (URFS) is effective for non-invasive monitoring in microwave ablation. A total of 15 fresh in vitro porcine livers were experimented. Features of amplitude integral, energy, sum of absolute value of difference (SAD) integral, time-shift and attenuation coefficient of URFS were extracted. Changing rules of these features and the relationships between time-shift, attenuation coefficient and tissue temperature were analyzed. Experimental results showed that maximums of amplitude integral, energy and SAD integral occur at the temperature within 50-60?C. In addition, there was a linear relationship between time-shift and tissue temperature within 60ºC and the ultrasonic attenuation coefficient increased with the temperature rising. Therefore, features of URFS can reflect the change of tissue property and may be used in the non-invasive monitoring of microwave ablation in the future.

Deformation-Based Morphometric study on Blind men's brain structures

Many studies have shown the functional relevance of cross-modal plasticity in blind men. However, few researches have focused on whether such functional plasticity is associated with macroscopic changes of structural anatomy in brain regions. Fortunately, deformation based morphometry (DBM) provides an important tool for the computational anatomy research. In this study we detected the changes of regional volume in brain structures between the blind men and normal controls with DBM method. Information of the difference is derived from the deformation field acquired during HAMMER non-rigid registration. The experimental results show that the regions expanded in the blind men’s brain are located at Brodmann 19,31 while the contracted regions located at Brodmann 17,18. This research is very helpful to discover the relationship between structural anatomy and functional data of blind men at a macroscopic level from neuroimaging perspective.

Alterations in Normal Aging Revealed by Cortical Brain Network Constructed Using IBASPM

Normal aging has been linked with the decline of cognitive functions, such as memory and executive skills. One of the prominent approaches to investigate the age-related alterations in the brain is by examining the cortical brain connectome. IBASPM is a toolkit to realize individual atlas-based volume measurement. Hence, this study seeks to determine what further alterations can be revealed by cortical brain networks formed by IBASPM-extracted regional gray matter volumes. We found the reduced strength of connections between the superior temporal pole and middle temporal pole in the right hemisphere, global hubs as the left fusiform gyrus and right Rolandic operculum in the young and aging groups, respectively, and significantly reduced inter-module connection of one module in the aging group. These new findings are consistent with the phenomenon of normal aging mentioned in previous studies and suggest that brain network built with the IBASPM could provide supplementary information to some extent. The individualization of morphometric features extraction deserved to be given more attention in future cortical brain network research.