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Chapter 7:
Test Patterns and How to Read Them
The details of a test pattern can be an excellent substitute for expensive instrumentation for medical facilities. Instrumentation certainly quantifies the performance of a display system in detail, but these are details the display manufacturer should already be cognizant of and have published for reference. Test patterns provide benchmarks that can be correlated to instrumented results and used as go/no-go gauges. A medical facility need only know that a display is not performing; to the extent it is not, let the vendor determine the details. This chapter focuses on two basic test patterns, that of the Society of Motion Picture and Television Engineers (SMPTE) and the Briggs Test Pattern 4. The Briggs pattern is named for Stewart J. Briggs, Boeing Electronics Company, and will be abbreviated as BTP 4. A number of other patterns have been developed by medical facilities and can be found in SPIE journals. Industry standardization for display interfaces became more organized in 1989 with the establishment of the Video Electronics Standards Association (VESA). A variety of test patterns are available from their web site (see Table 7.1). The Society for Information Display (SID) is an international organization focusing on the technology of displays. SID members directly and through SID standards subcommittees maintain active participation on a worldwide basis. Their magazine, Information Display, provides excellent information on new and emerging technologies. The American Association of Physicists in Medicine (AAPM), specifically Task Group 18, is completing documentation that may be adapted for medical-grade display specifications. A public document has been released for circulation by the Science Committee of the AAPM. Comprehensive test patterns are now available for 1k-line displays in 8 and 10 bits, along with patterns for 2k-line displays. At this time, it is the author’s opinion that it will become a voluntary standard and resource for medical institutions using softcopy displays. Version 9 of the document and test patterns can be downloaded at∼SAMei/tg18. In pointing out specific elements of test patterns, it will be assumed that previous chapters have been read regarding formation of the pixel and the respective contribution of the electron optics and video amplifier bandwidth. Proper setup of a display and gamma correction to a LUT should always be done at installation and then at regular intervals (depending on autoadjustments built into the display). Avoid doing the job twice; verify that proper display calibration procedures have been followed.
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