In the field of radiography, advancements in technology have led to the development of the flat panel detector (FPDs), which significantly enhances the quality and efficiency of imaging. This article will explore what flat panel detectors are, how they are made, their operational mechanisms, and the benefits they offer compared to traditional imaging methods.
What is a Flat Panel Detector?
A flat panel detector (FPD) is an advanced imaging device used in digital radiography (X-ray). Traditionally, X-ray images are produced using X-ray film or image intensifiers, but flat panel detectors capture images in a digital format. This allows flat panel detectors to create high-resolution X-ray images that are essential for clinical diagnosis.
What Are Flat Panel Detectors Made Of?
Flat panel detectors consist of various components necessary to achieve the desired results. It is essential to understand that there are two different types of flat panel detectors: indirect and direct. The major difference is that direct detectors convert X-rays directly into an electric charge, while indirect detectors first convert X-rays into light photons. These photons are then converted into an electrical charge. Direct detectors produce the highest resolution images, but indirect detectors provide faster results at a lower cost.
What is an Indirect Flat Panel Detector Made Of?
First is the scintillator layer, which is a type of phosphor material that converts high-energy radiation. In other words, it is the component responsible for absorbing X-rays. Typically, the scintillator layer is made from gadolinium oxysulfide (Gadox) or cesium iodide (CsI). A scintillator refers to the process where a material emits ultraviolet light when energized by high-energy photons or particles.
Next is the photodiode layer. This layer takes the light produced by the scintillator and converts it into an electric current. The photodiode is highly sensitive to light, exciting the electrons within it and generating the electric current needed to create an image. This layer is crucial for accurately capturing light information.
An indirect flat panel detector also contains a thin-film transistor (TFT) array, which reads and amplifies the electric charges. To achieve this, it is made of a semiconductor material such as silicon.
What is a Direct Flat Panel Detector Made Of?
Direct flat panel detectors have a similar structural makeup to indirect detectors, but with slight differences. Between two electrodes lies the photoconductive layer, which converts X-ray energy into ion pairs. This layer is made of amorphous selenium (a-Se).
The high-voltage electrodes collect the electrical charge produced by the X-rays. The flow of electrons to form the X-ray image relies on these high voltage electrodes, which also prevent ion pairs from combining. If these ion pairs were to combine, they would cancel out their electric charges, resulting in neutral compounds. Direct flat panel detectors also include a TFT readout array made of amorphous silicon.
How a Flat Panel Detector Works
To understand how a flat panel detector works, let’s walk through the process of producing an X-ray image.
- Indirect Flat Panel Detectors: First, X-rays pass through the patient and strike the scintillator layer, which converts the rays into visible light photons. The newly converted light photons then hit the photodiode layer, converting them into electrical charges. The electrical charge maintains the same amount of power as the original X-rays. The TFT array reads the electrical charges, processes them, and digitizes them to create the final X-ray image.
- Direct Flat Panel Detectors: X-rays pass through the patient and directly meet the photoconductive layer of amorphous selenium. This generates electrical charges or electron-hole pairs that match the power and intensity of the original X-rays. The TFT array collects the charges from the photoconductive layer, processing and digitizing them to produce the final X-ray image.
Benefits of Flat Panel X-ray Detectors
The traditional alternatives to flat panel detectors are film or image intensifier-based systems. Today, modern radiologists prefer flat panel detectors for several key reasons:
- Less Radiation: FPDs are very sensitive to X-rays, which means less radiation is needed to create the final image. Radiologists work hard to manage radiation doses, prioritizing patient health to prevent overexposure. With FPDs, patients can receive imaging more frequently while using minimal radiation.
- Better Image Quality: Direct FPDs provide high spatial resolution, producing sharp and detailed images thanks to their direct conversion capabilities. Digital processing reduces visual noise, resulting in clearer images. High-quality X-ray images are crucial for accurate clinical diagnosis.
- Cost-Effective: While FPDs have a high upfront cost, they eliminate recurring costs associated with film, chemicals, and maintenance required for traditional systems. Images taken using FPDs also require fewer retakes, saving time and resources that are critical in a clinical setting.
Reveal 35C Dual Energy Flat Panel Detector: 3 layers for Material Differentiation:
A leading option among modern FPDs is the portable Reveal 35C, developed by KA Imaging. The Reveal 35C features a patented 3-layer design, branded as SpectralDR technology, unlike traditional FPDs, which have only a single layer.
The Reveal 35C amplifies the benefits of contemporary FPDs, significantly enhancing X-ray imaging capabilities. While FPDs are known for requiring lower radiation doses, the Reveal 35C’s triple-layer design achieves one of the highest DQEs on the market. Thanks to its patented SpectralDR technology, it collects a series of clinically relevant data in a single exposure.
With just one exposure, the Reveal 35C produces three separate images: a conventional X-ray image, a soft tissue image, and a bone image— all without motion artifacts. For the first time, a FPD can be used to create dual-energy images portably from a single exposure.
The bone and soft tissue images both contribute to enhanced diagnosis. Removing the bone allows soft tissues (lungs in particular) to be better visualized without overlying obstructing bone. The bone images serve to better visualize fractures and other pathology. Medical line and tube visualization is also enhanced.
The Reveal 35C has been clinically tested and shown to find 33% more pneumonia cases, improve lesion visibility by 43%, and increase clinician confidence by 57% in ICU cases thanks to its dual-energy imaging.
Learn more about the Reveal 35C flat panel detector!
Flat panel detectors represent a significant advancement in the field of radiography, providing high-quality imaging with reduced radiation exposure and improved cost-effectiveness. Reveal 35C represents the evolution of FPDs, transforming clinical practice. Reveal 35C is available as a stand alone detector that can be used with any system, or as an integrated portable imaging system.
