The Difference Between Computed Radiography (CR) and 数码放射照相(DR)

数字放射显影术 has seen increasing use in the world of 非破坏性测试 in recent years, of which there are two basic types: Computed Radiography (CR) and Digital Detector Array radiography (DDA), 更常见的说法是 数码放射照相(DR).

With ongoing technological advancements and significant cost reductions with regards to purchasing, 处理, 以及传统胶片的储存, 数字系统已迅速成为首选. 

数字放射照相还包括 计算机断层扫描(CT), which compiles multiple digital images to produce 3D images. Even though CT scanning has been a mainstay of medical imaging for over 40 years, 它在工业上仍是一种较新的应用 非破坏性测试.

计算机放射照相Vs数字放射照相

计算摄影 是一个 间接 process, designed to be a replacement for traditional film radiography. 一个刚性或柔性盒式容纳成像板(IP), 这使得它们在许多应用中更容易使用.

x射线照射后, the IP is removed from the cassette and scanned by a dedicated processor, 读取存储的潜在(隐藏)图像, 把它转换成数字图像. The main advantage over traditional film is that IPs are reused hundreds, even thousands of times (depending on X-ray 能源 received). A scan typically takes two minutes, compared to approximately nine minutes 处理 of film. Image quality is comparable to film and general-ly exceeds it, 尤其是在对比敏感度方面.

ip可以像传统胶片一样使用. 例如, pipe bores and flanges are radiographed as the flexible cassettes can be placed in or around complex shapes. CR系统优越的动态范围, coupled with the ability to enhance and manipulate the processed image (software filters), 确保重拍被消除.

数字射线照相检测 使用数字探测器阵列, also known as a flat panel detector in place of an IP or traditional film. The detector converts the X-rays either directly or 间接ly into a digital image which can be ready to view almost instantly. This feature is harnessed in the field of “real-time” radiography, 哪一种是快速而有效的产品评价方法.

与CR，尤其是胶片相比, DR generally requires a smaller dose of radiation and thus less exposure time to attain comparable image quality. DR also has a very high dynamic range with bit-depths typically ranging from 8 to 16-bit. Images can also be manipulated and enhanced using grey-scale transforms and filters. 在理论上, FPDs can be used many thousands of times over many years and because there is no need for scanning or chemical 处理, 它提供了一个非常高效和经济的解决方案.

三维扫描:计算机断层扫描(CT)

DR和CR两种模式都会产生物体的二维图像. 相比之下, CT系统 produce a 3D image that is created by taking multiple image ‘slices’ (usually many thousands) at different angles around a single axis of object rotation. The computer then uses complex algorithms to reconstruct the slices into a 3D form. This process is very computer-intensive and can be time-consuming. 仍然, the final reconstructed image can pinpoint discontinuities within an object and give a precise depth and location which 2D systems simply cannot provide.

数字系统的好处

As a rule, the main advantage digital systems have over film-based systems is image portability. Images can be easily stored or sent electronically worldwide in seconds, as they are saved as computer files in various formats as opposed to film, which is carefully stored in humidity-controlled environments – for decades in some cases.

在计算机x线摄影和数字x线摄影之间抉择

There are several factors to consider when deciding which method best suits your needs. Both CR and DR systems generally require far less exposure time than film radiography. Both offer high latitude images and eliminate the reliance on chemicals for 处理.

Overall image quality is enhanced and more efficient with DR systems in comparison to CR systems; DDA exposures are typically 10-15 seconds in duration, 这大大减少了检查时间. 

DDA applications include several small specimens placed on one 14”x17” detector, 或者将探测器定位在更大的标本周围/内部. 然而, CR膜是柔性的，以满足试样的轮廓, 这对于DD应用程序来说是不可能的.

As a DDA system does not involve a technician removing the IP (or film to be processed), it permits automation by specimen manipulation between the source and the detector. 这可以适用于小型和大型标本. 

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