The results of an experiment that shows that it is very simple to contaminate digital images with information that can later be eztracted are presented. This Contamination cannot be detected when the image is displayed on a good quality graphics workstation. Based on these results, it is recommended that image downgrading based on visual display of the image t o be downgraded not be performed if there is any threat ofimage contamination by Trojan horse programs. Potential Trojan horse programs may include untrusted image processing software.

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AB STRACTRapid, accurate definition and volume calculation of anatomical objects is essential for effective CT and MR diagnosis. Absolute volumes often signal abnormalities while relative volumes -such as a change in tumor sizecan provide critical information on the effectiveness of radiation therapy. To this end, we have developed the "magic crayon" (MC) anatomical object visualization, object definition, and volume calculation tool as a follow on to UNC's Image Hierarchy Editor (THE) and Image Hierarchy Visualizer (THY). This paper presents the magic crayon system detailing interaction, implementation, and preliminary observer studies.MC has several features: First, it uses a number of 3D visualization methods to visualize rapidly an anatomical object. Second, MC can serve as a test bed for various object definition algorithms -such as the 3D Ridge Flow method; by interacting with these algorithms, the user can often define 3D anatomical objects in under 30 seconds. Third, MC serves as a testbed allowing the comparative evaluation of vanous volume calculation methods including pixel counting and Dr. David Eberly's divergence method. 0-8194-1 131-O/93/$6.OO SPIE Vol. 1898 Image Processing (1993) / 789 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/25/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx SPIE Vol. 1898 Image Processing (1993) / 791 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/25/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx

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