Flat Panel Detector X-Ray Imaging: What It Is and How It Works

How a flat panel detector works

A flat panel detector is built from a layer that captures X-rays and a matrix of tiny electronic sensors, each corresponding to one pixel. After the exposure, electronics read out the charge from each pixel, convert it to a digital value and send the data to the acquisition computer. The image appears on screen within seconds, ready for review and DICOM transfer.

Two conversion principles are used. In indirect conversion, a scintillator layer, typically caesium iodide (CsI) or gadolinium oxysulphide (GOS), turns X-rays into light, and a photodiode and transistor array turns the light into electric charge. In direct conversion, a photoconductor such as amorphous selenium turns X-rays straight into charge. Indirect detectors are by far the most common in general radiography. See flat panel detector types for a fuller comparison.

Why flat panel detectors replaced film and CR

Film needs chemical processing and storage. Computed radiography (CR) uses reusable plates that must be carried to a reader. A flat panel detector removes that step: the image is available at the console immediately, retakes are quicker, and the workflow suits busy emergency rooms. See the comparison in digital radiography vs computed radiography.

Digital detectors also offer a wide dynamic range, which tolerates exposure variation better than film, and good detective quantum efficiency, which can support image quality at a lower dose when the technique is optimised. This depends on the detector model and on correct technique, so it should be verified with the manufacturer's data.

Static and dynamic detectors

A static detector is designed for single radiographs, such as chest, limbs and spine. A dynamic detector reads out fast enough to produce continuous or pulsed fluoroscopy images and is used in remote-controlled R/F tables. The Perlove PLD9600D, for example, uses a 17 x 17 inch dynamic FPD, with pulsed fluoroscopy at 25 frames per second.

Dynamic detectors replaced the older image intensifier chain in fluoroscopy; see flat panel detector vs image intensifier.

Wired or wireless, and how detectors are used in a room

Fixed detectors are built into the table and wall stand, so they are always in position and cannot be dropped. Wireless portable detectors can be moved between table, wall stand and mobile units, and used for cross-table views. They are more flexible but need battery management and careful handling. See wireless flat panel detector.

Villa's Moviplan iC DR room is a good example of a modular layout, with fixed and wireless flat-panel detectors in the table and chest stand, VDX Next acquisition software with full DICOM integration, auto-tracking, auto-positioning and stitching. Details are on the Moviplan iC DR page.

• Scintillator: CsI or GOS (indirect), or a photoconductor (direct)
• Size: for example 35 x 43 cm or 43 x 43 cm
• Static or dynamic readout
• Fixed or wireless, battery and charging
• Software: DICOM, post-processing, stitching

What to check when comparing detectors

Compare detector size, pixel pitch, scintillator type, image-readout time, weight, ruggedness (ingress protection and drop resistance), battery life for wireless models and the warranty. Ask for the DQE and MTF figures from the manufacturer and the conditions under which they were measured. Image quality also depends on the generator, grid and the acquisition software, not only on the detector.

Detectors are the most delicate and costly component of a DR room. Learn how to protect them in flat panel detector care and how they are priced in flat panel detector price.

Talk to Beckfinity about your detector needs

Beckfinity supplies Villa and Perlove digital radiography and fluoroscopy systems to UAE hospitals and clinics. Contact our specialists to discuss detector size, wireless options and compatibility, and request a quotation.