Introduction and background: the International Angiographic Compression study.

The current issues (April issue) of the Journal of the American College of Cardiology (JACC) and the European Heart Journal (Eur Heart J) contain three related manuscripts that report the findings of a major international clinical study of the impact of digital data compression on the diagnostic accuracy of coronary angiography. Because the topic is complex and most practitioners have a limited background in this area, this introduction is written to assist readers in understanding the study’s findings, interpreting the results, and applying the information to their clinical practices and administrative decisions. This introductory article represents the views of the authors and should not be construed as official policy of the American College of Cardiology (ACC) or the European Society of Cardiology (ESC). These studies were undertaken to provide a scientific basis for identifying standards to be incorporated into the Digital Imaging and Communications Standard for Medicine (DICOM). The pioneers of DICOM proceeded on the premise that eventually digital imaging techniques would completely replace analog recording methods such as film or videotape. They correctly recognized that a successful transition to the digital era would require carefully written standards to ensure that patient data and images could be exchanged without quality degradation. Beginning in 1992, the cardiology community, led by the ACC, initiated the current process of standardizing the digital file format and image exchange medium for cardiac X-ray angiography. A committee jointly directed by ACC and industry representatives has met monthly in Washington, D.C. for the last six years to develop the current angiographic standard. This effort was broadened to include the full participation of the ESC in 1996 and was joined by the Japanese cardiology societies in 1998. In 1995, a basic cardiac X-ray angiographic application profile, defined as 512 3 512 pixel images with 8 bits (256 levels) of gray scale per pixel, was first demonstrated and included in the DICOM standard. This application profile also designated the recordable compact disk (CD-R) as the approved exchange medium for angiographic images. Within a few years, the DICOM cardiac standard became universally accepted throughout the world as the only method appropriate for exchange of digital angiographic images. More recently, the DICOM Standards Committee has adopted a high-resolution standard, defined as 1,024 3 1,024 pixel images with up to 12 bits (4,096 levels) of gray scale per pixel. The large quantities of digital data required to represent a cardiac angiographic study present a major challenge. In the standard DICOM file format, each cine frame contains 256 kilobytes of data. At a 30 frame per second (fps) acquisition rate, each second of cine requires 7.5 megabytes (MB). For 1,024 3 1,024 3 10 bit images, each second of imaging can require more than 35 MB. A typical diagnostic study 60 s in length and acquired at the lower resolution of 512 3 512 3 8 generates approximately 450 MB of digital data. The large size of these digital data files poses a number of operational challenges: