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Ko, Guen Bae,Lee, Jae Sung Published for the American Association of Physicis 2015 Medical physics Vol.42 No.1
<P>Metal package photomultiplier tubes (PMTs) with a metal channel dynode structure have several advanced features for devising such time-of-flight (TOF) and high spatial resolution positron emission tomography (PET) detectors, thanks to their high packing density, large effective area ratio, fast time response, and position encoding capability. Here, we report on an investigation of new metal package PMTs with high quantum efficiency (QE) for high-resolution PET and TOF PET detector modules.</P>
Moon, Woo Kyung,Huang, Yao-Sian,Lo, Chung-Ming,Huang, Chiun-Sheng,Bae, Min Sun,Kim, Won Hwa,Chen, Jeon-Hor,Chang, Ruey-Feng Published for the American Association of Physicis 2015 Medical physics Vol.42 No.6
<P>Triple-negative breast cancer (TNBC), an aggressive subtype, is frequently misclassified as fibroadenoma due to benign morphologic features on breast ultrasound (US). This study aims to develop a computer-aided diagnosis (CAD) system based on texture features for distinguishing between TNBC and benign fibroadenomas in US images.</P>
Wang, Li,Ren, Yi,Gao, Yaozong,Tang, Zhen,Chen, Ken-Chung,Li, Jianfu,Shen, Steve G F,Yan, Jin,Lee, Philip K M,Chow, Ben,Xia, James J,Shen, Dinggang Published for the American Association of Physicis 2015 Medical physics Vol.42 No.10
<P>A significant number of patients suffer from craniomaxillofacial (CMF) deformity and require CMF surgery in the United States. The success of CMF surgery depends on not only the surgical techniques but also an accurate surgical planning. However, surgical planning for CMF surgery is challenging due to the absence of a patient-specific reference model. Currently, the outcome of the surgery is often subjective and highly dependent on surgeon's experience. In this paper, the authors present an automatic method to estimate an anatomically correct reference shape of jaws for orthognathic surgery, a common type of CMF surgery.</P>
Kim, Kyungsang,Lee, Taewon,Seong, Younghun,Lee, Jongha,Jang, Kwang Eun,Choi, Jaegu,Choi, Young Wook,Kim, Hak Hee,Shin, Hee Jung,Cha, Joo Hee,Cho, Seungryong,Ye, Jong Chul Published for the American Association of Physicis 2015 Medical physics Vol.42 No.9
<P>In digital breast tomosynthesis (DBT), scatter correction is highly desirable, as it improves image quality at low doses. Because the DBT detector panel is typically stationary during the source rotation, antiscatter grids are not generally compatible with DBT; thus, a software-based scatter correction is required. This work proposes a fully iterative scatter correction method that uses a novel fast Monte Carlo simulation (MCS) with a tissue-composition ratio estimation technique for DBT imaging.</P>
Yoon, Jai-Woong,Park, Young-Guk,Park, Chun-Joo,Kim, Do-Il,Lee, Jin-Ho,Chung, Nag-Kun,Choe, Bo-Young,Suh, Tae-Suk,Lee, Hyoung-Koo Published for the American Association of Physicis 2007 Medical physics Vol.34 No.11
<P>The stationary grid commonly used with a digital x-ray detector causes a moiré interference pattern due to the inadequate sampling of the grid shadows by the detector pixels. There are limitations with the previous methods used to remove the moiré such as imperfect electromagnetic interference shielding and the loss of image information. A new method is proposed for removing the moiré pattern by integrating a carbon-interspaced high precision x-ray grid with high grid line uniformity with the detector for frequency matching. The grid was aligned to the detector by translating and rotating the x-ray grid with respect to the detector using microcontrolled alignment mechanism. The gap between the grid and the detector surface was adjusted with micrometer precision to precisely match the projected grid line pitch to the detector pixel pitch. Considering the magnification of the grid shadows on the detector plane, the grids were manufactured such that the grid line frequency was slightly higher than the detector sampling frequency. This study examined the factors that affect the moiré pattern, particularly the line frequency and displacement. The frequency of the moiré pattern was found to be sensitive to the angular displacement of the grid with respect to the detector while the horizontal translation alters the phase but not the moiré frequency. The frequency of the moiré pattern also decreased with decreasing difference in frequency between the grid and the detector, and a moiré-free image was produced after complete matching for a given source to detector distance. The image quality factors including the contrast, signal-to-noise ratio and uniformity in the images with and without the moiré pattern were investigated.</P>
Kim, Youngwoo,Hong, Byung Woo,Kim, Seung Ja,Kim, Jong Hyo Published for the American Association of Physicis 2014 Medical physics Vol.41 No.7
<P>A major challenge when distinguishing glandular tissues on mammograms, especially for area-based estimations, lies in determining a boundary on a hazy transition zone from adipose to glandular tissues. This stems from the nature of mammography, which is a projection of superimposed tissues consisting of different structures. In this paper, the authors present a novel segmentation scheme which incorporates the learned prior knowledge of experts into a level set framework for fully automated mammographic density estimations.</P>
Lee, Hyunseok,Lee, Won Seok,Park, Jong In,Son, Kwang-Jae,Park, Min,Bang, Young-bong,Choy, Young Bin,Ye, Sung-Joon Published for the American Association of Physicis 2015 Medical physics Vol.42 No.6
<P>Purpose: In radiotherapy, metallic implants often detach from their deposited sites and migrate to other locations. This undesirable migration could cause inadequate dose coverage for permanent brachytherapy and difficulties in image-guided radiation delivery for patients. To prevent migration of implanted seeds, the authors propose a potential strategy to use a biocompatible and tissue-adhesive material called polydopamine. Methods: In this study, nonradioactive dummy seeds that have the same geometry and composition as commercial 1-125 seeds were coated in polydopamine. Using scanning electron microscopy and x-ray photoelectron spectroscopy, the surface of the polydopamine-coated and noncoated seeds was characterized. The detachment stress between the two types of seeds and the tissue was measured. The efficacy of polydopamine-coated seed was investigated through in vitro migration tests by tracing the seed location after tissue implantation and shaking for given times. The cytotoxicity of the polydopamine coating was also evaluated. Results: The results of the coating characterization have shown that polydopamine was successfully coated on the surface of the seeds. In the adhesion test, the polydopamine-coated seeds had 2.1-fold greater detachment stress than noncoated seeds. From the in vitro test, it was determined that the polydopamine-coated seed migrated shorter distances than the noncoated seed. This difference was increased with a greater length of time after implantation. Conclusions: The authors suggest that polydopamine coating is an effective technique to prevent migration of implanted seeds, especially for permanent prostate brachytherapy. (C) 2015 American Association of Physicists in Medicine.</P>