Liyun Ni

University of North Carolina at Chapel Hill, North Carolina, United States

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Publications (3)4.06 Total impact

  • Contemporary Clinical Trials 08/2005; 26(4):514-515. DOI:10.1016/j.cct.2005.04.003 · 1.99 Impact Factor
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    ABSTRACT: To determine which factors affected the increase in average glandular dose recorded at the annual US Food and Drug Administration Mammography Quality Standards Act inspections of mammography equipment in North Carolina from 1997 to 2001. Average glandular dose, HVL, kVp, ambient light, luminance, equipment age, processing speed, and system speed for every mammography unit at all facilities in the state were collected by state inspectors. A mixed-effect model was used to assess the average changes of glandular dose over time and to identify the factors associated with these changes. There was a statistically significant increase in the average glandular dose in North Carolina in 1999, 2000, and 2001 when compared with the baseline year of 1997. Factors that were statistically significantly linked to this effect were changes in kVp, processing speed, and system speed. Average glandular dose for mammography has recently increased in North Carolina. This change is likely caused by changes in screen-film products and processing techniques.
    Academic Radiology 06/2004; 11(5):536-43. DOI:10.1016/j.acra.2004.01.003 · 2.08 Impact Factor
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    ABSTRACT: Success of blinding is a fundamental issue in many clinical trials. The validity of a trial may be questioned if this important assumption is violated. Although thousands of ostensibly double-blind trials are conducted annually and investigators acknowledge the importance of blinding, attempts to measure the effectiveness of blinding are rarely discussed. Several published papers proposed ways to evaluate the success of blinding, but none of the methods are commonly used or regarded as standard. This paper investigates a new approach to assess the success of blinding in clinical trials. The blinding index proposed is scaled to an interval of -1 to 1, 1 being complete lack of blinding, 0 being consistent with perfect blinding and -1 indicating opposite guessing which may be related to unblinding. It has the ability to detect a relatively low degree of blinding, response bias and different behaviors in two arms. The proposed method is applied to a clinical trial of cholesterol-lowering medication in a group of elderly people.
    Controlled Clinical Trials 05/2004; 25(2):143-56. DOI:10.1016/j.cct.2003.10.016