Wenpeng Gao

Corpus Callosum Atrophy and Cognitive Decline in Early Alzheimer's Disease: Longitudinal MRI Study

Background: We investigated the rate of corpus callosum (CC) atrophy and its association with cognitive decline in early Alzheimers disease (AD). Methods: We used publicly available longitudinal MRI data corresponding to 2 or more visits from 137 subjects characterized using the Clinical Dementia Rating (CDR) score. We classified these subjects into 3 groups according to the progression of their cognitive status: a healthy control group (CDR 0→0, n = 72), a decliner group (CDR 0→0.5, n = 14) and an AD group (CDR 0.5→0.5/1, n = 51). We measured the CC area on the midsagittal plane and calculated the atrophy rate between 2 or more visits. The correlation between the CC atrophy rate and annualized Mini Mental State Examination (MMSE) change was also analyzed. Results: The results indicated that the baseline CC area was larger in the healthy control group compared to the AD group, whereas the CC atrophy rate was higher in the AD group relative to the control and decliner groups. The CC atrophy rate was also correlated with the annualized MMSE change in AD patients (p < 0.05). Conclusion: Callosal atrophy is present even in early AD and subsequently accelerates, such that the rate of CC atrophy is associated with cognitive decline in AD patients.

Prognostic value of CA4/DG volumetry with 3 T magnetic resonance imaging on postoperative outcome of epilepsy patients with dentate gyrus pathology

PURPOSE Hippocampal sclerosis (HS), the most common feature of mesial temporal lobe epilepsy (MTLE), is widely accepted as surgical indication for refractory epilepsy. Pathological hallmarks in hippocampal dentate gyrus (DG), including granule cell loss (GCL) and granule cell dispersion (GCD), are known to be closely related to the status epilepticus and spontaneous seizure. Our aim was to assess the association between volumetric changes in the hippocampal CA4/DG determined with 3-Tesla (3T) magnetic resonance imaging (MRI) and the postoperative seizure outcomes in MTLE patients with or without dentate gyrus pathology (DGP). METHODS High-resolution T2- and T1-weighted three-dimensional (3D) MRI scans were performed on 39 MTLE patients before surgery with a 3T Philips scanner. ITK-SNAP software was used for segmentation and volumetry of the CA4/DG segment, and NASP software was used for 3D reconstructions of the CA4/DG region. Immunostaining for Neuronal Nuclei (NeuN) was performed on resected hippocampal specimens after surgery to verify the accuracy of CA4/DG segmentation and histopathological changes in DG. RESULTS The CA4/DG subfield could be precisely segmented with high-resolution 3T MRI and confirmed by comparison of NeuN-immunoreactive slices with MRI results. MTLE patients with DGP showed smaller CA4/DG volume and favorable postoperative seizure outcomes. CONCLUSION The volumetry of CA4/DG was associated with the pathological changes in DG in MTLE patients. The volumetry of CA4/DG with preoperative 3T MRI could predict the postoperative seizure outcomes in those patients.

Computer‐assisted automatic localization of the human pedunculopontine nucleus in T1‐weighted MR images: a preliminary study

The pedunculopontine nucleus (PPN) is a new promising target of deep brain stimulation (DBS) for the treatment of Parkinsons disease. This study was to develop a method of computer‐assisted automatic localization of the PPN in T1‐weighted MR images.

Design and performance evaluation of a 3-axis force sensor for MIS palpation

Purpose – This paper aims to develop a novel miniature 3-axis force sensor which can detect the interaction forces during tissue palpation in MIS (minimally invasive surgery). MIS offers many significant merits compared with traditional open surgery, the wound to the patients and the postoperative pains are alleviated and reduced dramatically. However, the inherent drawback due to lack of force feedback still exists while conducting some operation procedures. For example, tissue palpation performed easily during open surgery could not be realized in an MIS manner. Design/methodology/approach – The force sensor is based on the resistive-based sensing method that utilizes strain gauges to measure the strain when the external loads are acting on the tip of the sensor. A novel flexible tripod structure with bending and compression deformations is designed to discriminate the magnitudes and directions of the three orthogonal force components. A linear characteristic matrix is derived to disclose the relationsh...

A non-linear, anisotropic mass spring model based simulation for soft tissue deformation

Mass Spring Model (MSM) is widely used in the simulation of soft tissue deformation due to its high efficiency. However, the anisotropic property of soft tissue challenges such a simulation. This manuscript proposed an improved MSM by taking into consideration of anisotropic property. Firstly, the anisotropic property of soft tissue is investigated. Then, the parameters of MSM are set according to the investigation. Finally, the force on each spring is combined by axial and radial forces. Experimental results illustrates the proposed method can simulate deformation accurately. It shows prospective in the application of surgical simulation.

An Unfixed-elasticity Mass Spring Model based simulation for soft tissue deformation

Mass Spring Model (MSM) and Finite Element Method(FEM) are the two basic models for soft tissue deformation simulation. MSM has high computation efficiency and low physical accuracy, while the case for FEM is just the reverse. How to simulate the deformation of the tissue in real time and accurately is still a challenging. This paper proposed an improved MSM by determining the parameters of MSM using FEM The improved MSM is called Unfixed-elasticity Mass Spring Model (UMSM), meaning the parameters of each spring is different from those of others, and will change gradually during deformation. The experimental results show a fairly realistic simulation can be generated by UMSM The results indicate that the UMSM has a relatively high reasonability and practicability.

Automatic localization of AC and PC landmarks in T2-weighted MR volumetric neuroimages

A novel method is presented for automatic identification of the anterior commissure (AC) and posterior commissure (PC) in T2-weighted MR volumetric images (MRI). AC and PC are two critical landmarks of human brain. It is important to accurately identify them for brain segmentation, registration, functional neurosurgery, human brain mapping, and particularly for the Talairach transformation. The algorithm of identifying them consists of four steps: (1) Identify the corpus callosum and select the region of interest; (2) Identify the fornix and locate the initial AC; (3) Segment part of the third ventricle and locate the initial PC; (4) Refine the positions of AC and PC. The algorithm has been validated quantitatively with 20 T2-weighted MRI data sets. The mean errors of the localization of them were 1.50 mm (AC) and 1.60 mm (PC). It took about 15 seconds for identifying them on P4 3.0 GHz. This fully automatic algorithm is potentially useful in clinic and for research.

Automatic Identification of the Reference System Based on the Fourth Ventricular Landmarks in T1-weighted MR Images

RATIONALE AND OBJECTIVES The reference system based on the fourth ventricular landmarks (including the fastigial point and ventricular floor plane) is used in medical image analysis of the brain stem. The objective of this study was to develop a rapid, robust, and accurate method for the automatic identification of this reference system on T1-weighted magnetic resonance images. MATERIALS AND METHODS The fully automated method developed in this study consisted of four stages: preprocessing of the data set, expectation-maximization algorithm-based extraction of the fourth ventricle in the region of interest, a coarse-to-fine strategy for identifying the fastigial point, and localization of the base point. The method was evaluated on 27 Brain Web data sets qualitatively and 18 Internet Brain Segmentation Repository data sets and 30 clinical scans quantitatively. RESULTS The results of qualitative evaluation indicated that the method was robust to rotation, landmark variation, noise, and inhomogeneity. The results of quantitative evaluation indicated that the method was able to identify the reference system with an accuracy of 0.7 +/- 0.2 mm for the fastigial point and 1.1 +/- 0.3 mm for the base point. It took <6 seconds for the method to identify the related landmarks on a personal computer with an Intel Core 2 6300 processor and 2 GB of random-access memory. CONCLUSION The proposed method for the automatic identification of the reference system based on the fourth ventricular landmarks was shown to be rapid, robust, and accurate. The method has potentially utility in image registration and computer-aided surgery.

Morphology of the Adult Midsagittal Brainstem in Relation to the Reference Systems : MRI-based Variability Study

RATIONALE AND OBJECTIVES Anterior/posterior commissure reference system (AC/PC reference system) and the fastigium/ventricular floor plane reference system (FFL/VFL reference system) are two reference systems used in the stereotactic localization of the invisible nuclei of the brainstem in magnetic resonance (MR) images. This study investigated the variation of the midsagittal brainstem in relation to the AC/PC and VFL/FFL reference systems with respect to age and gender. MATERIALS AND METHODS High-resolution T1-weighted structural MR images were acquired from 64 adults (age range 21-60 years, 32 males and 32 females). The AC/PC and VFL/FFL reference systems were identified automatically. A set of landmarks of the midsagittal brainstem were defined and localized interactively. RESULTS Results illustrated that there was significant difference between the variance of the anteroposterior coordinate of the landmarks in relation to the AC/PC reference system and that in relation to the FFL/VFL reference system (P < .05), the former is larger than the latter. The positions of the landmarks in the females are more anterior than those in the males in relation to the AC/PC reference (P < .05); the difference in relation to the FFL/VFL reference system was not found. CONCLUSION Either the FFL/VFL reference system or the AC/PC reference system has its own advantage in the stereotactic localization of the structure in the brainstem.

The measurement of the volume of stereotaxtic MRI hippocampal formation applying the Region growth algorithm based on seeds

The paper mainly probes into the accuracy of applying the Region growth algorithm to MRI images segmentation. Firstly the researchers scan the adult volunteers to get stereotaxtic MRI images, then discern and segment them in two separate ways: Region growth algorithm and manual segmentation, and compare the differences in results. The outcome shows no obvious difference exists, so the Region growth algorithm can be used into the segmentation of some complex formations such as hippocampus.