Key Factors in Selecting Tftbased Xray Detectors

In hospital radiology departments, when doctors diagnose patients through X-ray imaging, highly efficient and reliable X-ray detectors play a crucial role behind the scenes. Different types of detectors vary in their principles, performance characteristics, and application scenarios. How does one select the most suitable solution? This article focuses on Thin-Film Transistor (TFT) technology, providing an in-depth exploration of X-ray detector classifications and key features to support informed decision-making.

X-ray detectors serve as the central component of X-ray imaging systems, converting X-rays into signals that can be recorded and displayed. Based on different working principles and technical implementations, X-ray detectors can be categorized into various types. Among these, flat-panel detectors utilizing TFT technology have gained widespread adoption in medical diagnostics and industrial inspection due to their high sensitivity, superior resolution, and real-time imaging capabilities.

X-ray detectors can be classified through multiple approaches, with the most common standards including:

By Signal Conversion Method:

• Direct Conversion: X-rays directly interact with semiconductor materials (such as selenium), generating electron-hole pairs that are collected and converted into electrical signals. Direct conversion detectors offer higher spatial resolution but relatively lower conversion efficiency.
• Indirect Conversion: X-rays first interact with scintillator materials (such as cesium iodide), converting them into visible light. This light is then captured by photodiodes or CCD/CMOS sensors and transformed into electrical signals. Indirect conversion detectors provide higher conversion efficiency but slightly lower spatial resolution compared to direct conversion types.

By Detector Structure:

• Flat-Panel Detectors: Composed of numerous pixel units capable of capturing entire X-ray images in a single exposure. These represent the most widely used X-ray detector type today.
• Linear Array Detectors: Consisting of a single row of pixel units that require scanning movements to acquire X-ray images. Commonly employed in CT scanning applications.
• Point Detectors: Featuring only one pixel unit that necessitates point-by-point scanning to obtain X-ray images. Primarily used in X-ray diffraction applications.

Thin-Film Transistors (TFTs) represent a type of field-effect transistor where the active layer consists of thin-film materials deposited on a substrate. In X-ray flat-panel detectors, TFTs primarily function as switches for pixel units and facilitate signal readout. Each pixel unit contains both a photodiode (converting light signals to electrical signals) and a TFT (controlling electrical signal readout).

The operational process involves: when light emitted from the scintillator strikes the photodiode, electrical charges are generated. The TFT manages the accumulation and release of these charges. During signal readout, the TFT activates, releasing charges to the readout circuit which converts them into digital signals, ultimately forming the X-ray image.

Compared to other X-ray detector types, TFT flat-panel detectors offer several distinct advantages:

• Enhanced Sensitivity: Capable of detecting weak X-ray signals, thereby reducing required radiation doses.
• Superior Resolution: Delivers clear X-ray images that improve diagnostic accuracy.
• Real-Time Imaging: Enables immediate display of X-ray images, facilitating medical procedures.
• Large-Area Coverage: Accommodates extensive imaging regions, minimizing scan repetitions.
• Digital Output: Provides direct digital signal output for simplified image processing and storage.

Selecting appropriate X-ray detectors requires careful consideration of application scenarios, performance metrics, and cost factors. TFT flat-panel detectors have emerged as the dominant choice in X-ray imaging due to their exceptional performance characteristics and broad applicability. Understanding detector classifications and TFT technology principles enables more informed selection and utilization of X-ray imaging equipment, ultimately enhancing reliability in both medical diagnostics and industrial inspection applications.