At one time, the sight of a doctor holding an X-ray film up to the light was commonplace in TV dramas and movies. Nowadays, however, digital photography has replaced film as the predominant technology used in X-ray imaging.
Since the late 1990s, computed radiography (CR) has come into widespread use. In CR, X-rays pass through the body, producing an image on an imaging plate. This image is then scanned and digitised using a special device known as a CR reader. Recent years have also seen the emergence of digital radiography (DR), in which a digital image is captured directly, eliminating the need for scanning and digitising. DR is already in widespread use, mainly at large hospitals and orthopaedic centres.
Besides capturing images as speedily as any digital camera, DR also requires high image-quality. This is because, instead of film or an imaging plate, an X-ray image receptor is used. The performance of the X-ray image receptor determines the extent to which high-quality images can be obtained at low X-ray exposure doses.
One of the indices of image-receptor image-quality is detective quantum efficiency or DQE. The higher this value, the more efficiently X-ray photons can be captured, and the higher the image quality obtainable, even at low doses. Dynamic range is another critical index with regard to image quality. If the image receptor has a wide dynamic range value, stabilised images can be rendered with fine detail.
The X-ray image receptors used in DR imaging are known as Flat Panel Detectors (FPDs). Using scintillator technology cultivated over many years, Konica Minolta has developed high-DQE FPDs. Their key feature is their ability to maintain a high DQE at low X-ray exposure doses.
Conventional DR devices have a dynamic range of approximately 3.5 digits (2μR to 7mR). Konica Minolta has successfully broadened the dynamic range to approximately 4 digits (1.4μR to 12mR), which is close to that of CR.
Thanks to their high DQE and expanded dynamic range, Konica Minolta's DR devices can produce high-quality diagnostic images even at X-ray exposure doses roughly half those required in CR.
Micrograph of CsI crystals
Side view (left) and surface (right)
The scintillator uses caesium iodide (CsI) crystals. In order to convert the X-rays into light and emit that light efficiently, it is important to optimise the shape of the columnar CsI crystals, and ensure uniformity of height and thickness. Thanks to its advanced materials technology and production technology, Konica Minolta is one of the few manufacturers in the world capable of in-house production of scintillators using uniform crystals that have been grown to cover a large area.