Technology

In a first step, a special image plate (with europium doped barium halogenide crystals/ BaFBr:Eu2) is exposed to X-rays. Here electrons are energized out of their initial state and saved in this new state. In step 2 (reading out), the plate is irradiated with a fine laser beam, which makes it 'glow' (luminesence radiography). This 'glowing' is variably strong and, once electronically converted, provides the final X-ray image. Afterwards, the plate is erased.

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• Resolution: 2.5 - 5 line pairs (LP)/mm. The resolution should be >2.4 LP/mm according to the German Medical Association. This is also often given in pixels/mm (5 - 10).
• Plate size: 18 x 24 cm - 35 x 43 cm
• Detective Quantum Efficiency (DQE)*: < 30 %. A high DQE value stands for high contrast and minimal noise at lower X-ray exposures (a DQE of 70 % is optimum).
• Preview image: after Ø 60 seconds
• Acquisition cycle: every 45 to 90 seconds
  (time elapsed between the current and the following image)
• Processing capacity: Ø 60 plates/hour

Advantages

• for stationary and portable radiography in the small animal and equestrian sectors 
• low purchase costs (25,000 - 45,000 €)

Disadvantages

• indirect system (3 steps: exposure, read-out, erase)
• minimal time-saving in comparison to analog radiography
• high maintenance costs (depending on X-ray volume)
• plate wear-and-tear in open systems

*DQE denotes the ability of a system to convert X-ray quanta into image-relevant information. It describes contrast and noise levels within the system.

Technology

Flat panel detectors comprise extremely small image elements (pixels), which convert X-rays into electric charge, either directly (amorphous selenium/a-Se) or indirectly (amorphous silicon/a-Si with a scintillator plate/CsI or Gd2O2S). The radiation level converted into pixels is proportional to a specific grayscale value, the accuracy of which depends upon the pixel depth used. Modern systems can distinguish between up to 16,384 grayscales, which corresponds to a 14 bit pixel depth. Flat panel detectors are connected directly to a computer and display the completed image instantly after X-ray exposure (and all in just one step).

Figures

• Resolution: 2.5 - 5 Lp/mm (5 - 10 pixels/mm)
• Detector size: 23 x 29 cm - 43 x 43 cm with automatic recognition of the actual image size
• DQE: 60 - 70 % (a DQE of 70 % is optimum)
• Preview image: after Ø 2 seconds
• Acquisition cycle: 15 - 20 seconds
• Processing capacity: always adequate

advantages

• for stationary and portable radiography in the small animal and equestrian sectors 
• direct digital system (only one step)
• high time saving (images are instantly available)
• tissue and skeletal structures are visible on one and the same image
• practically maintenance-free
• significantly reduced radiation exposure

Disadvantages

• higher cost of acquisition (50,000 - 65,000 €)