Chapter 1: What is Diagnostic Imaging?

The term diagnostic imaging within the medical field covers all modalities and procedures aiming at visualization of structures in the human body not seen directly. Until the 1980s diagnostic imaging, including computed tomography (CT) was based on X-ray principles as firstly described by the German professor Konrad Wilhelm Roentgen in December 1896 and consequently called “roentgen”, or “radiology”. The last 20-30 years, however, have seen the development of several imaging techniques based on other principles than X-rays. The most important of these modalities are probably ultrasonography (US), magnetic resonance imaging (MRI), and procedures based on nuclear medicine principles – various types of “scintigraphy” - including the so-called positron emission tomography (PET).

Ideally various imaging modalities should supplement each other, although this is not always the case. It is also the wish that new methods might substitute older and maybe more dangerous procedures. This situation is clearly seen with US versus X-ray examinations where US may offer more exact diagnostic information without exposing the patients to potentially dangerous ionizing radiation.