SIIM University explores what propels digital radiography

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SIIM University sessions are proof positive that education is forefront this week at SIIM 2007 in Providence, R.I. On Thursday, Section I, “Digital Radiology” included three presentations under the direction of Charles “Chuck” E. Willis, PhD, The University of Texas MD Anderson Cancer Center, Houston, Texas, and section head of the program. Willis said he considered the three presentations to be equivalent to three levels of college courses.

The presentations included: 101, “Fundamentals of Digital Radiography” by Willis; 201, “What’s New in Digital Radiography?” presented by Willis on behalf of J. Anthony Seibert, PhD, University of California-Davis Medical Center; and 301, “The Transition from Analog to Digital Radiography: A Technologist’s Perspective” presented by Shirley Weddle, RT(R) (M), Total Digital Imaging Consulting.

Willis opened his presentation with a set of learning objectives: explain how ordinary radiographic images can be captured in digital form; and discuss the advantages and limitations of digital images. He compared the current science of digital imaging to that of an Etruscan Roman mosaic and defined a digital radiographic (DR) image as a matrix of numbers with discrete physical pixel dimensions and gray-levels.

DR technologies have advantages over conventional screen-film Willis said. The method is preferred because of its availability, flexibility, and convenience.

The three approaches to DR are film digitization, non-photographic capture with digital development and direct capture with or without conversion to light. Willis described in detail the characteristics, process, and fundamentals of each approach. 

Just how good the approximation of a digital image is Willis said is relative to spatial information that depends on dimensions of the pixels and blur and contrast information that depends on grayscales per pixel, characteristic function and noise.

In the quest for a quality image, he said there is a documented tendency to overexpose in DR, as well as computed radiography. The five technological methods for reducing patient dose and effects on image quality require adjustments in darkening, contrast, noise, sharpness, and artifacts.