What Does a Flat Panel Detector Do? A Quick Overview

May 3, 2023 1:40:00 AM / by Chad Hutchison

Digital radiography utilizes a unique technology, similar to a digital camera, that instantly sends X-ray images to a computer for quick viewing. Likewise, digital radiography systems use a detector known as a flat panel to translate data into a digital electronic signal. This digital electronic signal becomes a digital X-ray image. Flat panel detectors allow for direct digital body imaging so medical practitioners can diagnose and treat disease.

There are two main types of flat panels, indirect and direct, each with unique strengths and weaknesses. In the below article, we're sharing more about the use of flat panel detectors, the differences between flat panel types, and more. Let's jump right into it.

What Is a Flat Panel Detector?

Flat panel detectors are a special radiological device used in digital radiography to detect X-rays. While flat panel detectors create the X-ray image as it exists, they also work by converting X-rays to light or to charge.

Indirect conversion occurs when X-rays are converted to light, whereas direct conversion occurs when X-rays are converted to charge. A thin film transistor (TFT) array will then read the data. The TFT acts as a switch to turn each pixel on or off, displaying it as light or dark. This creates an X-ray image on a computer, desktop, or digital screen for healthcare providers to view instantly - and to provide valuable information to their clients. 

What Are The Different Types of Flat Panel Detectors?

Two types of flat panel detectors convert X-rays into images that utilize two different technologies, including the indirect flat panel detector and the direct flat panel detector. The different flat panel detectors result in varying image quality, and each works better for specific utilizations in a practice. Let's discuss each below.

Indirect Flat Panel Detector

Indirect flat panel detectors work by indirectly converting X-rays to light, then to charge, and finally to a digital signal. Two separate layers accomplish this conversion. The outermost layer is the scintillator; the scintillator is a phosphor screen made of cesium iodide or gadolinium oxysulfide. Behind the scintillator is an amorphous silicon photodiode detector array - this silicon contains millions of pixels. Each pixel also has a photodiode which generates an electrical signal proportionate to the amount of light detected by the scintillator layer in front of the pixel. The photodiodes amplify the signals and encode them to represent the X-ray image digitally. The indirect panel is best for general radiography, angiography, and fluoroscopy.

Direct Flat Panel Detector

Direct flat panel detectors convert X-rays directly to charge utilizing a photoconductor. The photoconductor captures and converts X-ray photons directly into electric charge. The outermost layer of the direct flat panel detector is a high-voltage bias electrode. Behind this layer is the photoconductor. The photoconductor is made of amorphous selenium or cadmium telluride. 

There is no optical conversion step, like in indirect flat panels, which reduces blur. The small pixel size and direct conversion result in a high spatial resolution. It is best to use direct flat panel detectors when a high resolution is required, such as in mammography. High resolution is needed to identify microcalcifications.

What Are Flat Panel Detectors Made Of?

  • Scintillator phosphor screen made of cesium iodide or gadolinium oxysulfide
  • Amorphous silicon detector
  • High voltage bias electrode
  • Photoconductors made of amorphous selenium or cadmium telluride

How a Flat Panel Detector Works

Due to the varying technology, there are two separate processes for how indirect flat panels and direct flat panels work. We will discuss these steps in more detail below.

Indirect Panels

  1. The X-ray beam transmits to a flat panel detector.
  2. The X-ray beam hits the scintillator, which converts the X-ray into light.
  3. Pixels in amorphous silicon detect light.
  4. The photodiode in the pixel generates an electrical signal proportionate to the light produced by the scintillator in front of the pixel.
  5. The electrical signal is amplified and encoded.
  6. TFT or CCD reads out the digital image.

Direct Panels 

  1. The X-ray beam transmits to a flat panel detector.
  2. The X-ray photons strike the photoconductor.
  3. Photoconductor generates electron-hole pairs through the internal photoelectric effect.
  4. Voltage in the selenium layer draws the electron holes to corresponding electrodes creating a current.
  5. TFT reads out the signal.

Need a Flat Panel Detector? We Can Help!

Are you looking to purchase a flat panel detector for your practice? Maven Imaging would happily assist you with this purchase.

Contact our team of knowledgeable professionals who can guide you through buying a flat panel detector for your medical facility. We have many flat panel detector options to choose from, as well as available financing options to make this purchase a reality.

Tags: x-ray equipment

Chad Hutchison

Written by Chad Hutchison

Founder and CEO of Maven Imaging, Chad Hutchison has been in the medical imaging equipment market since 2003. As his business grew, he pioneered buying and selling medical equipment online and eventually began offering leasing and financing to meet market demands and help customers. His market expertise goes beyond traditional medical imaging and finance support, as he’s spearheading cloud-based lending solutions for vendors across the sector.