Pei Chai

Chinese Academy of Sciences, Peping, Beijing, China

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Publications (7)11.22 Total impact

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    ABSTRACT: The accuracy of attenuation correction in positron emission tomography scanners depends mainly on deriving the reliable 511-keV linear attenuation coefficient distribution in the scanned objects. In the PET/CT system, the linear attenuation distribution is usually obtained from the intensities of the CT image. However, the intensities of the CT image relate to the attenuation of photons in an energy range of 40 keV─140 keV. Before implementing PET attenuation correction, the intensities of CT images must be transformed into the PET 511-keV linear attenuation coefficients. However, the CT scan parameters can affect the effective energy of CT X-ray photons and thus affect the intensities of the CT image. Therefore, for PET/CT attenuation correction, it is crucial to determine the conversion curve with a given set of CT scan parameters and convert the CT image into a PET linear attenuation coefficient distribution. A generalized method is proposed for converting a CT image into a PET linear attenuation coefficient distribution. Instead of some parameter-dependent phantom calibration experiments, the conversion curve is calculated directly by employing the consistency conditions to yield the most consistent attenuation map with the measured PET data. The method is evaluated with phantom experiments and small animal experiments. In phantom studies, the estimated conversion curve fits the true attenuation coefficients accurately, and accurate PET attenuation maps are obtained by the estimated conversion curves and provide nearly the same correction results as the true attenuation map. In small animal studies, a more complicated attenuation distribution of the mouse is obtained successfully to remove the attenuation artifact and improve the PET image contrast efficiently.
    01/2014; 23(2).
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    ABSTRACT: A depth discrimination method is devised based on a multirow linear array detector for push-broom Compton scatter imaging. Two or more rows of detector modules are placed at different positions towards a sample. An improved parallel-hole collimator is fixed in front of the modules to restrict their fields of view. The depth information could be indicated by comparing the signal differences. In addition, an available detector and several related simulations using GEANT4 are given to support the method well.
    Applied radiation and isotopes: including data, instrumentation and methods for use in agriculture, industry and medicine 09/2013; 82C:293-299. · 1.09 Impact Factor
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    ABSTRACT: A PET module that comprises a pair of compact, high-resolution and large-area detectors based on silicon photomultipliers (SiPM) was developed and evaluated. The detector's effective area was 24 mm×24 mm. LYSO crystals measuring 1.9 mm×1.9 mm×10 mm and charge division circuit were employed to obtain high spatial resolution with relatively concise Front-end electronics (FEE). Initial results showed the detector to be compatible with 1.5 T magnetic fields. The system's intrinsic FWHM spatial resolution is 1.50 mm. The average energy resolution is 18.5% and the coincidence timing resolution is 2.6 ns.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 04/2012; 670:49–54. · 1.32 Impact Factor
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    ABSTRACT: To automatically extract regions of interest (ROIs) and simultaneously preserve the anatomical characteristics of each individual, we developed a new atlas-based method utilizing a pair of coregistered brain template and digital atlas. Unlike the previous atlas-based method, this method treats each individual as the target image, and the template and atlas are each transformed to register with the individual. To evaluate the accuracy of this method we implemented it in extracting the hippocampus from two groups of T(2)-weighted structural images with different spatial resolutions and a group of T(2)*-weighted functional images. Furthermore, the results were compared against a manually segmented hippocampus and an atlas-derived hippocampus. Jaccard similarity (JS) reached 84.7%-90.5%, and relative error in volume (RV) was 4.8%-12.7%. The consistency observed between the results of the proposed method and manual drawing was therefore considerable. We developed a new atlas-based method for ROI extraction that can automatically extract ROI and simultaneously preserve each individual's unique anatomical characteristics.
    Journal of Magnetic Resonance Imaging 10/2010; 32(4):830-5. · 2.57 Impact Factor
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    ABSTRACT: Structural brain abnormalities have been widely reported in major depressive disorder (MDD). However, many previous results cannot exclude the interferences of medication or multiple recurrent episodes. In this study, we examined structural brain abnormalities by comparing 68 drug-naïve first-episode adult-onset MDD and 68 healthy controls (HCs). Structural magnetic resonance imaging (MRI) and voxel-based morphometry (VBM) methods were used. The mean values of grey matter volume/white matter volume (GMV/WMV) were calculated, then the differences between MDD and HCs were analyzed, and the associations of the differences with clinical characteristics of depression were discussed. The whole brain GMV/WMV did not differ between MDD patients and HCs; however, the regional GMV of the right pre-supplementary motor area (pre-SMA) was smaller in MDD patients. The GMV of both hippocampi was positively correlated with symptom severity and lower in patients with long durations. These results indicate the GMV reduction of the pre-SMA at an early stage of depression, whereas the GMV of the hippocampus is associated with depressive characteristics. Moreover, the whole brain GMV/WMV was negatively related to the duration of depression, supporting that volume loss could become progressive during the development of disease. These results may suggest the importance of identifying and intervening depression at an early stage, especially the first year after onset, to prevent volume loss in the brain.
    Neuroscience Letters 08/2010; 480(1):30-4. · 2.06 Impact Factor
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    ABSTRACT: The central nervous system (CNS) is often affected by systemic lupus erythematosus (SLE), but assessment of CNS outcomes using noninvasive cerebral structural measures remains in its infancy. Magnetic resonance imaging (MRI) with expert visual interpretation is critical to diagnosis, but does not permit quantitative measurements. Our pilot study investigated whether quantitative brain volumetric analyses could be used to detect white-matter (WM) abnormalities and responses to treatment in SLE ( NCT00703742). Forty-two pairs of SLE patients and healthy controls underwent high-resolution 3-dimensional structural MRI scans. Combining voxel-based morphometry and region of interest analyses, subtle WM volume abnormalities in whole brains from SLE patients were identified, and regional WM volume was calculated. Associations between WM volume and symptom severity, as well as the effects of immunosuppressive therapy, were then investigated. The WM volume of the SLE group was significantly decreased in the bilateral posterior and anterior crus of the internal capsule (PIC and AIC, respectively), the subgyral right frontal lobe, and left temporal lobe (p < 0.001). Regional WM volume (left PIC and right AIC) was correlated with SLEDAI scores. The WM volume of patients treated with immunosuppressive therapy was greater than that of patients who were never treated with immunosuppressive therapy. Quantitative brain volumetric analyses detect brain injuries in WM for SLE that are not obvious by conventional MRI, and may be adequately sensitive and quantitative to measure the effect of therapeutic interventions in preventing brain injury and outcomes in SLE.
    The Journal of Rheumatology 03/2010; 37(5):974-86. · 3.17 Impact Factor
  • Source
    Pei Chai, BaoCi Shan
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    ABSTRACT: A method has been developed to establish the crystal position look-up table for positron emission tomography with block detectors. It is based on the principle that the counts in crystal position histogram obey the Gaussian mixture model (GMM). This method has taken full consideration of the characteristics of the GMM and the detector itself. The experimental results have proved that it is simple, reliable, and universal.
    Science in China Series E Technological Sciences 01/2009; 52(8):2418-2423. · 1.02 Impact Factor

Publication Stats

34 Citations
11.22 Total Impact Points


  • 2010–2012
    • Chinese Academy of Sciences
      • Key Laboratory of Nuclear Analytical Techniques
      Peping, Beijing, China
  • 2009
    • Northeast Institute of Geography and Agroecology
      • Key Laboratory of Nuclear Analytical Techniques
      Peping, Beijing, China