Operating Manual

Digital Radiography (DR)

145

16.1 Introduction to DR

As in other NDT methods, the introduction of microprocessors and computers has

brought about significant changes to radiographic examination. Chapter 17 describes

a number of systems such as Computed Tomography (CT), radioscopy and X-ray

microscopy that have been made possible by newly developed technology which involves

rapid digital processing of vast quantities of data. But as this chapter will show, compu-

ter technology has also entered the field of conventional image forming radiography, as

applied in industry.

The driving force was the medical world where digital radiography already earned its cre-

dits and has become standard technology. Along with a few other companies, GE

Inspection Technologies and its affiliated suppliers developed a variety of digital systems

with a wide range of computer-aided NDT applications. Digital radiography partly repla-

ces conventional film and also permits new applications. The growing number of availa-

ble standards, norms, codes and specifications

essential for industrial acceptance and

application

supports this tendency.

Although the process itself is different from film radiography, DR resembles traditional

radiography to a large extent. The optical impression of the X-ray images is similar so

that RT trained personnel can quickly adopt this new technology and adapt to it without

great efforts. Moreover the images can be interpreted in analogy to film.

Digitisation of traditional radiographs although not real digital radiography, uses the

same digitisation technology, presentation on a display of a work station and image

adjustment, and therefore is part of this section too. Digitisation of film is done for the

purpose of archiving and/or image enhancement (adjustment).

Two main methods of real filmless digital imaging can be distinguished:

1. digital radiography by means of phosphor coated semi-flexible imaging plates

(compared with flexible film) in combination with computer processing,

so-called “Computed Radiography”, CR for short

2. digital radiography with rigid flat panel- or flat bed detectors and instant

computer processing, referred to as “Digital Radiography”, DR for short, and

considered as the genuine (true) DR method and sometimes in the field referred

to as “Direct Radiography”.

Each method has differing strengths, advantages and limitations that should be

evaluated in terms of specific application, inspection requirements and economics:

capital, human investment and productivity (number of exposures in a certain time).

144

Digitally enhanced radiograph of a “mermaid/man”.

The radiograph negated a myth by demonstrating that it concerns

a man-made creature.