In today’s rapidly developing digital imaging technology, flat panel detectors have become indispensable core components in fields such as medical X-ray imaging and industrial testing. It gradually replaces traditional films and image intensifiers with advantages such as high resolution, fast imaging, and digital output. This article will delve into the principles, classifications, applications, and future trends of flat panel detectors.
What is a flat panel detector?
Flat panel detector is an imaging device that directly converts X-rays or other high-energy rays into digital signals. It mainly consists of a scintillator layer (or direct conversion layer), a photoelectric sensor array (TFT/CMOS), and a signal processing circuit. Its core function is to replace traditional film and achieve fast, high-definition, and digital image acquisition
Key features:
Digital output: Directly generate standard format images such as DICOM for easy storage and AI analysis.
High resolution: The pixel size can be as small as 50-200 microns, presenting clearer details.
Real time imaging (dynamic FPD): suitable for scenes such as fluoroscopy and interventional surgery.
Low dose radiation: Compared to traditional film, it can reduce the X-ray exposure of patients or operators.
What are the two major technological routes for flat panel detectors?
According to the X-ray conversion method, flat panel detectors are mainly divided into indirect conversion type and direct conversion type
1. Indirect FPD (Indirect FPD)
Principle: X-ray → scintillator (such as CsI, Gd ₂ O ₂ S) → visible light → photodiode → electrical signal → digital image.
Advantages: High sensitivity, suitable for low-dose imaging (such as mammography). Mature technology with relatively low cost.
Disadvantage: Visible light scattering may cause a slight decrease in resolution.
2. Direct FPD (Direct FPD)
Principle: X-rays → photoconductive materials (such as a-Se, CdTe) → direct generation of electrical signals → digital images.
Advantages: No light scattering, higher spatial resolution (suitable for precision scenarios such as dental CBCT). Fast response speed.
Disadvantages: High manufacturing cost and strict requirements for material uniformity.
Core application scenarios:
1. Medical imaging
DR (Digital Radiography): Chest X-ray, bone and joint examination, replacing traditional CR systems.
Dynamic fluoroscopy: gastrointestinal imaging, interventional surgery (such as DSA angiography).
Breast molybdenum target: high resolution early breast cancer screening.
Dental CBCT: Three dimensional dental imaging, direct conversion FPD is the mainstream.
2. Industrial non-destructive testing (NDT)
PCB/electronic component inspection: discovered welding defects and internal cracks.
Aerospace: Analysis of turbine blades and composite structures.
Lithium battery testing: alignment of electrode plates, investigation of internal foreign objects.
3. Security field
Luggage security check: The FPD in the airport CT security check machine can quickly identify dangerous goods.
Technical Challenges and Development Trends
Current challenges
Cost issue: Due to material and process limitations, the price of direct conversion FPD remains high.
Flexibility requirement: Curved detectors are required for curved surface detection scenarios (such as pipeline inspection).
Post time: Jun-30-2025